When we think of the beginning, we think of it as the start of a series of chronological events. In the context of the Universe, the beginning refers to the origin of space and time. The beginning is dependent on time. Without time, we cannot have a beginning. Cosmology only started to make sense when people began to understand space-time as a living and evolving thing. Time is simply part of the Universe, and it must be considered when we analyze its existence.
In the early 1970s, English physicists Stephen Hawking and Roger Penrose postulated that the Universe did, in fact, have a beginning. Hawking and Penrose postulated that if the evolution of the Universe could be described by Einstein’s general theory of relativity, and it is composed of energy content that we are familiar with, then it had to have a beginning. Based on their observations, it is impossible to discern the actual beginning of space-time to a specific point. This theorem is known as the singularity theorem.
Wednesday, May 13, 2009
Chapter 17: Wrapped and Warped
Extra Dimensions of Space
When we perceive our Universe, we perceive it as being three-dimensional, however, we must consider that there are more than three dimensions. It is possible that certain dimensions are hiding. We can add another dimension to our Universe. We cannot interpret this extra dimension because from where we stand, we cannot see it. Every point in our three-dimensional space has an invisible dimension. This new idea was proposed by Theodor Kaluza and Oskar Klein and has been very influential in developing the current cosmological model. They proposed that the electromagnetic force arose like gravity, as a deformation of space-time. They postulated that the electromagnetic force resulted from the warping of the fourth-dimension. The third-dimension was warped by mass and energy, and Kaluza and Klein postulated that charge affected the fourth dimension.
When we perceive our Universe, we perceive it as being three-dimensional, however, we must consider that there are more than three dimensions. It is possible that certain dimensions are hiding. We can add another dimension to our Universe. We cannot interpret this extra dimension because from where we stand, we cannot see it. Every point in our three-dimensional space has an invisible dimension. This new idea was proposed by Theodor Kaluza and Oskar Klein and has been very influential in developing the current cosmological model. They proposed that the electromagnetic force arose like gravity, as a deformation of space-time. They postulated that the electromagnetic force resulted from the warping of the fourth-dimension. The third-dimension was warped by mass and energy, and Kaluza and Klein postulated that charge affected the fourth dimension.
Chapter 16: The Ecology Of Galaxies
There are many galaxies in the Universe. Our galaxy has two close neighbouring galaxies- the Large and Small Magellanic Clouds-which are a twentieth and a hundredth the size of the Milky Way. Also closely neighbouring our galaxy is the Andromeda Galaxy, and there are more galaxies that exist a little further out. Together, this group of galaxies form what is known as the Local Group. Throughout the Universe, there are many galaxies, embedded in larger agglomerations or cluster composed of thousands of individual galaxies. Closest to our Galaxy is the Virgo Cluster, which is situated about 50 million light years away. The Virgo Galaxy is so large that its gravitational force is sucking the Milky Way in towards it. Situated about 300 million light years away is the Coma Cluster, which is made up 10,000 galaxies.
Andromeda has a spiral shape and it is very similar to our Galaxy. Most of the galaxies that are observed have a spiral shape and extend to great lengths. They tend to be found in low-density regions of space, where there are few other galaxies.
Besides spiral galaxies, there are elliptical galaxies. Elliptical galaxies are large accumulations of stars with no obvious features. They do, as their name indicates, have an elliptical shape, and they are classified by their ellipticity. When naming elliptical galaxy, the convention is to indicate it with a E followed by a number. For example, if an elliptical galaxy is E0, it will not be elliptical, but it will be spherical. If it is classified as E1, the galaxy will be slightly elliptical. An E8 galaxy will be basically flat and look unlike a spiral.
Edwin Hubble developed a classification system for the galaxies. In his system, galaxies are ordered into a tuning fork structure. At the base of the tuning fork, are the E0s. As we move farther down the fork’s stem, the galaxies’ shapes become more elliptical, until the end of the tuning fork where they become essentially flat without spiral arms. This is where the two prongs of the fork begin. As you move down the prongs, the prongs become larger and larger, and the galaxies become larger with longer arms. On one prong, galaxies have spherical bulges, and on the other arm, galaxies have cores shaped as bars.
Most of the galaxies that are observed are classified under this classification scheme. Galaxies that are not classified are not because their shape is too irregular, or do not possess spiral arms. Galaxies that have an irregular shape are called irregulars, where all the other galaxies that cannot be classified are placed. Many irregular galaxies are a result of a collision between spiral and elliptical galaxies. Most irregular galaxies, such as the Magellanic Clouds, contain up to a third of their masses in gas, which is used to form stars.
Andromeda has a spiral shape and it is very similar to our Galaxy. Most of the galaxies that are observed have a spiral shape and extend to great lengths. They tend to be found in low-density regions of space, where there are few other galaxies.
Besides spiral galaxies, there are elliptical galaxies. Elliptical galaxies are large accumulations of stars with no obvious features. They do, as their name indicates, have an elliptical shape, and they are classified by their ellipticity. When naming elliptical galaxy, the convention is to indicate it with a E followed by a number. For example, if an elliptical galaxy is E0, it will not be elliptical, but it will be spherical. If it is classified as E1, the galaxy will be slightly elliptical. An E8 galaxy will be basically flat and look unlike a spiral.
Edwin Hubble developed a classification system for the galaxies. In his system, galaxies are ordered into a tuning fork structure. At the base of the tuning fork, are the E0s. As we move farther down the fork’s stem, the galaxies’ shapes become more elliptical, until the end of the tuning fork where they become essentially flat without spiral arms. This is where the two prongs of the fork begin. As you move down the prongs, the prongs become larger and larger, and the galaxies become larger with longer arms. On one prong, galaxies have spherical bulges, and on the other arm, galaxies have cores shaped as bars.
Most of the galaxies that are observed are classified under this classification scheme. Galaxies that are not classified are not because their shape is too irregular, or do not possess spiral arms. Galaxies that have an irregular shape are called irregulars, where all the other galaxies that cannot be classified are placed. Many irregular galaxies are a result of a collision between spiral and elliptical galaxies. Most irregular galaxies, such as the Magellanic Clouds, contain up to a third of their masses in gas, which is used to form stars.
Monday, May 11, 2009
Chapter 15: Primordial Sound
As we saw in the last chapter, in the 1970s, the Universe was believed to be homogeneous. The photons have been traveling since recombination; they have been affected by the roughness of the Universe on the scale of the cosmological horizon. Overall the level of inhomogeneity is very mild. If space-time were rough, it would be so warped that it would be populated by black holes. Rarely do we see black holes on small scales, which means that space-time cannot be too rough on small scales. When we look at galaxies on a scale, which correspond to sizes between thousands and millions of light years, it is clear that there is structure. This means that between the smoothness of large scales and the mild roughness of small scales, there is inhomogeneity on intermediate scales. Inhomogeneity has some randomness.
The existence of sound waves in the Universe was predicted in the 1970s and 1980s. The expedition of the COBE satellite revealed the discovery of inhomogeneities on large angular scales. A number of experiments were designed to detect sound waves from the primordial universe. To effectively measure sound, powerful telescopes were needed that could block out sound from contaminating sources. Contaminating sources, including the atmosphere, absorb and emit radiation. One way to get around the contamination from other sources, such as the atmosphere, is to send telescopes up in balloons to a height of about 40 kilometres. To accurately measure, it is essential to get high enough in the atmosphere to escape contaminating factors like variable weather conditions and other uncontrollable effects that might affect the interpretation of the relic sky.
The existence of sound waves in the Universe was predicted in the 1970s and 1980s. The expedition of the COBE satellite revealed the discovery of inhomogeneities on large angular scales. A number of experiments were designed to detect sound waves from the primordial universe. To effectively measure sound, powerful telescopes were needed that could block out sound from contaminating sources. Contaminating sources, including the atmosphere, absorb and emit radiation. One way to get around the contamination from other sources, such as the atmosphere, is to send telescopes up in balloons to a height of about 40 kilometres. To accurately measure, it is essential to get high enough in the atmosphere to escape contaminating factors like variable weather conditions and other uncontrollable effects that might affect the interpretation of the relic sky.
Chapter 14: From Order to Chaos
Although we believe otherwise, everything has texture- nothing is completely smooth. Even though it may feel smooth to the touch or look smooth to the eye, nothing is completely smooth. When we consider a wooden table for example. To the naked eye, it looks completely smooth, and to the touch it feels very smooth, however, if we could magnify the texture of the table with a superfine microscope at and extremely high magnification, we would realize that it is not smooth. Really, the table would look like a vast space of hills and valleys. The same can be said about the Universe. When we look at the night sky, it appears to be completely smooth and homogeneous, but on an extremely small scale, its constituents would not appear smooth. If we could see the Universe on such a scale, we would see the space between particles, and we could see that some areas are more dense or empty than others.
The Universe looks homogeneous from afar, but it in actuality, it is very structured. When we view the sky we can see some stars and maybe even a few planets depending on where we situated in relation to their positions. As we judge from a larger scale, we see that we are embedded in a galaxy, and that galaxy resides in and amongst a larger galaxy. From even further away, we see that cluster of galaxies is seen as many clusters composing a massive network of filaments, walls, and nodes of light. If we observe this from very far away, it appears as if all of these irregularities blend into one faint, smooth texture.
When we look at the surface of a table, a piece of material, or even the surface of the Earth, it appears that the farther away we move, the more indefinite textures become. When we view the Universe, we are confined to the Earth, so we can’t move further away, we can only move closer. The closer we get, the more irregularities that are present, and the more we realize that the Universe is simply not smooth.
Since the 1970s, it has been possible to measure angular positions of galaxies in the sky. These observations relay that galaxies tend to be evenly distributed throughout the sky. There aren’t any preferred directions in the sky, which is expected if the Universe is homogeneous. It is not only possible to measure the angular positions in the sky, but also the distances to galaxies. As we can recall from a previous chapter, we know that a red shift is a measure of how fast a galaxy is moving away from us; Hubble’s law tells us that the more distant a galaxy is, the faster it moving away from us. Therefore, we can use the angular positions and the red shift to construct a three-dimensional model of the galaxies.
The most compelling evidence for homogeneity is relic radiation. Homogeneity implies that the Universe cooled at exactly the same rate at all points in space. Basically, the rate at which hydrogen and helium captured electrons was the same at all points in space. The left over radiation must have had exactly the same temperature everywhere. The smooth collection of radiation is an indication that the Universe was smooth in the past. This is the strongest evidence for a homogeneous Universe. A rough Universe on small scales appears smoother and smoother the farther away we move from it.
The Universe looks homogeneous from afar, but it in actuality, it is very structured. When we view the sky we can see some stars and maybe even a few planets depending on where we situated in relation to their positions. As we judge from a larger scale, we see that we are embedded in a galaxy, and that galaxy resides in and amongst a larger galaxy. From even further away, we see that cluster of galaxies is seen as many clusters composing a massive network of filaments, walls, and nodes of light. If we observe this from very far away, it appears as if all of these irregularities blend into one faint, smooth texture.
When we look at the surface of a table, a piece of material, or even the surface of the Earth, it appears that the farther away we move, the more indefinite textures become. When we view the Universe, we are confined to the Earth, so we can’t move further away, we can only move closer. The closer we get, the more irregularities that are present, and the more we realize that the Universe is simply not smooth.
Since the 1970s, it has been possible to measure angular positions of galaxies in the sky. These observations relay that galaxies tend to be evenly distributed throughout the sky. There aren’t any preferred directions in the sky, which is expected if the Universe is homogeneous. It is not only possible to measure the angular positions in the sky, but also the distances to galaxies. As we can recall from a previous chapter, we know that a red shift is a measure of how fast a galaxy is moving away from us; Hubble’s law tells us that the more distant a galaxy is, the faster it moving away from us. Therefore, we can use the angular positions and the red shift to construct a three-dimensional model of the galaxies.
The most compelling evidence for homogeneity is relic radiation. Homogeneity implies that the Universe cooled at exactly the same rate at all points in space. Basically, the rate at which hydrogen and helium captured electrons was the same at all points in space. The left over radiation must have had exactly the same temperature everywhere. The smooth collection of radiation is an indication that the Universe was smooth in the past. This is the strongest evidence for a homogeneous Universe. A rough Universe on small scales appears smoother and smoother the farther away we move from it.
Chapter 13: Dark Energy is the Fifth Element
Max Planck, a German Physicist, postulated that energy existed in discrete chunks or quanta, to explain how we view radiation. Einstein proved that this, in fact, was a reality, and it was acceptable to think of radiation as a collection of individual photons. This led to the duality of light as a wave and as a particle. French Physicist Louis de Broglie recognized that this principle explained energy levels in all particles, like electrons and protons. What he discovered was that everything in nature has quantized energy levels. All objects have well-defined and discrete energy spectra.
Many people ask, “What is the lowest possible energy state?” Logically, most people would assume that it is zero, but the truth is that an energy state can never be zero. The Uncertainty Principle can be stated in terms of energy and time. Basically, it is impossible to measure, at the same time, to measure the time elapsed and the energy involved in any given process. If we consider a particle, which has a finite lifetime, we can conclude that there is an uncertainty in its lifetime, meaning that it cannot have a zero energy level. Two important observations come from this observation. First, the minimum energy level cannot be zero because it has a value, which is fixed by the uncertainty principle. Secondly, we can no longer think of parts of the Universe as “empty space”. We can pick any region of the Universe and consider it for a fixed amount of time, there is an uncertainty placed on the energy in that region- it cannot equal zero because of the Uncertainty Principle. Therefore, from these speculations, we can conclude that empty space is not simply empty- it actually has energy.
In conjunction with the Uncertainty Principle, we can assume that at any given moment, there is an uncertainty in the amount of energy present. It is possible that certain areas of space will have more energy than others. This energy can give rise to particles, which collide and disappear very rapidly. The energy continually presents itself in the form of various particles swaying in and out of existence.
One thing that I found very interesting was the author’s explanation of water. It had never occurred to me how the cracks in water form when water freezes. When water freezes and there are no cracks or fissures present, water is said to be symmetrical, however, this symmetry can be broken. The orientation of each water molecule is completely random, meaning that they have no preferred direction. Water molecules are weakly bound through each other by electrostatic forces, but are still able to freely move around. As water cools, its molecules slow down, and its electrostatic forced help to lock it into place in an order where they can all fit together. As a result of this random arrangement, each molecule chooses its own direction in space and water starts to solidify.
Each section of water begins to solidify independently. One location begins to freeze and then another begins to freeze. Each of the molecules at that site pick out a preferred direction at that site, and there is no guarantee that the preferred direction will be the same at all of the sites- most will be misaligned. When the different sections are misaligned, we are left with cracks and fissures. The cracks represent the separation between the different zones that have frozen and to tolerate the tension created by the misaligned water molecules.
Many people ask, “What is the lowest possible energy state?” Logically, most people would assume that it is zero, but the truth is that an energy state can never be zero. The Uncertainty Principle can be stated in terms of energy and time. Basically, it is impossible to measure, at the same time, to measure the time elapsed and the energy involved in any given process. If we consider a particle, which has a finite lifetime, we can conclude that there is an uncertainty in its lifetime, meaning that it cannot have a zero energy level. Two important observations come from this observation. First, the minimum energy level cannot be zero because it has a value, which is fixed by the uncertainty principle. Secondly, we can no longer think of parts of the Universe as “empty space”. We can pick any region of the Universe and consider it for a fixed amount of time, there is an uncertainty placed on the energy in that region- it cannot equal zero because of the Uncertainty Principle. Therefore, from these speculations, we can conclude that empty space is not simply empty- it actually has energy.
In conjunction with the Uncertainty Principle, we can assume that at any given moment, there is an uncertainty in the amount of energy present. It is possible that certain areas of space will have more energy than others. This energy can give rise to particles, which collide and disappear very rapidly. The energy continually presents itself in the form of various particles swaying in and out of existence.
One thing that I found very interesting was the author’s explanation of water. It had never occurred to me how the cracks in water form when water freezes. When water freezes and there are no cracks or fissures present, water is said to be symmetrical, however, this symmetry can be broken. The orientation of each water molecule is completely random, meaning that they have no preferred direction. Water molecules are weakly bound through each other by electrostatic forces, but are still able to freely move around. As water cools, its molecules slow down, and its electrostatic forced help to lock it into place in an order where they can all fit together. As a result of this random arrangement, each molecule chooses its own direction in space and water starts to solidify.
Each section of water begins to solidify independently. One location begins to freeze and then another begins to freeze. Each of the molecules at that site pick out a preferred direction at that site, and there is no guarantee that the preferred direction will be the same at all of the sites- most will be misaligned. When the different sections are misaligned, we are left with cracks and fissures. The cracks represent the separation between the different zones that have frozen and to tolerate the tension created by the misaligned water molecules.
Chapter 12: An Accelerating Universe
Using Supernovae to Measure Distances
Supernovae are some of the brightest objects in the sky, characterized as the explosions of massive stars. Interestingly enough, supernovae shine as brightly as billions of stars put together, emitting as much light as the` galaxy of its residence. It is likely to find supernovae on a given night. They have been observed and recorded for many hundreds of years. The last reported supernova in the Milky Way was in 1572, and it was visible by the naked eye.
A supernova finalizes the life cycle of a star- a star that is heavier than the Sun. The supernova is dependent on the mass of the star. Nuclear forces cause the collapse of the lighter stars, where as heavier stars ignite because of such strong gravitational attractions present at their core. Therefore, there are two types of supernova.
Supernovae Ia have very distinctive features, making them very identifiable. Supernovae Ia correspond to light stars and Supernovae Ib, correspond to heavier stars. When the supernovae Ia detonates, its spectra is easily identifiable because hydrogen is absent, allowing them to be distinguishable compared to other types of supernovae.
Supernovae are some of the brightest objects in the sky, characterized as the explosions of massive stars. Interestingly enough, supernovae shine as brightly as billions of stars put together, emitting as much light as the` galaxy of its residence. It is likely to find supernovae on a given night. They have been observed and recorded for many hundreds of years. The last reported supernova in the Milky Way was in 1572, and it was visible by the naked eye.
A supernova finalizes the life cycle of a star- a star that is heavier than the Sun. The supernova is dependent on the mass of the star. Nuclear forces cause the collapse of the lighter stars, where as heavier stars ignite because of such strong gravitational attractions present at their core. Therefore, there are two types of supernova.
Supernovae Ia have very distinctive features, making them very identifiable. Supernovae Ia correspond to light stars and Supernovae Ib, correspond to heavier stars. When the supernovae Ia detonates, its spectra is easily identifiable because hydrogen is absent, allowing them to be distinguishable compared to other types of supernovae.
Chapter 11: Dark and Exotic Matter
The Universe contains matter, which evidently, we know exists. However, there is visible matter and invisible matter or dark matter. There is evidence that establishes this “missing matter,” but it is impossible for us to know what this matter is, or the form that it takes. Two ideas have been proposed over the last 30 years. The first proposal was a halo, which consists of heavy clumps ordinary matter that form spherical covers around galaxies. The other type is a particle that does not emit or interact with radiation.
Dark matter, unlike most objects in the Universe, does not shine, but there are many other objects in the Universe that don’t shine like planets, asteroids, comets, and rock masses. Interestingly enough, these objects don’t shine because they don’t give off energy like a star. They simply reflect light from the Sun, which allows them to be seen. The problem with dark matter is that we cannot identify it form. Maybe it is in such an obvious form that we’re looking too hard for it and can’t identify it. Dark matter accounts for such a large mass that small objects such as planets and other small masses combined could not account for all of the dark matter in the Universe. At the same time, they can’t be too heavy because if they are, they will ignite and become stars.
Objects that have a mass that is equal to or less than 80 per cent of the Sun’s mass have been called Massive Compact Halo Objects or MACHOs for short because they are massive and could be used to explain the mass of halos.
An example of a MACHO is a brown dwarf. So far in my studies in science, I have never heard of a brown dwarf. Brown dwarfs are very much like planets, and have masses a few times greater than Jupiter’s mass. Although their masses are greater than Jupiter’s, they are actually smaller than Jupiter because they are so dense from the principles of quantum mechanics. Planets are held together by electromagnetic forces, but brown dwarfs follow Heisenberg’s Unicertainty Principle that accounts for the movement of particles as they try resist gravitational force. Brown dwarfs are very heavy, and because they account for such a great amount of mass, they can clearly be considered to be dark matter.
Black holes also possess characteristics of MACHOs. When light attempts to travel beyond its gravitational pull, it is restricted and pulled towards the centre of the gravitational force. A black hole is essentially an object with a radius equal to the Earth’s radius with the ability to restrict light. The point at which no light can escape is called the event horizon, causing objects to appear dark. Although it was believed that black holes were just a speculation- a mathematical speculation based on Einstein’s genera theory of relativity- there is evidence for their existence.
At a black hole’s surface, the gravitational pull is so powerful that it destroys the surrounding material, and separates it into constituents of energetic particles and radiation. Black holes are surrounded by light that can be viewed with x-ray telescopes. If this is so, can we correctly categorize black holes as MACHOs?
Brown dwarfs and black holes are definitely dark, but gravity makes it possible to see them- gravity works as a lens. Take, for example, a star shining in the distance, and a MACHO is passing in front of it. It is expected that it would cause and eclipse as it passes in front of the star, however, this is not the case. Instead, the MACHO deflects the light and focuses towards the Earth. Just as the MACHO passes in front of the star, the light is beamed at us and we can see the light. This effect is called microlensing and effectively deflects dark objects.
Although effective, there are two drawbacks to this method of identifying dark matter. First of all, stars change their brightness and dimness regularly. It is possible that in some cases, their twinkle may be confused with the passage of a MACHO. Secondly, microlensing is incredibly rare. To find such a event, an observer must observe several million stars over years and be in the right place at the right time to catch one of them twinkle.
Researchers have even postulated the existence of a dark matter particle, however, such a particle would be too light to detect or to clump together in the Sun’s core. These particles could potentially collide at the centre of the galaxy. In doing so, they would produce pairs of electrons and positrons eventually producing beams of photons.
Dark matter, unlike most objects in the Universe, does not shine, but there are many other objects in the Universe that don’t shine like planets, asteroids, comets, and rock masses. Interestingly enough, these objects don’t shine because they don’t give off energy like a star. They simply reflect light from the Sun, which allows them to be seen. The problem with dark matter is that we cannot identify it form. Maybe it is in such an obvious form that we’re looking too hard for it and can’t identify it. Dark matter accounts for such a large mass that small objects such as planets and other small masses combined could not account for all of the dark matter in the Universe. At the same time, they can’t be too heavy because if they are, they will ignite and become stars.
Objects that have a mass that is equal to or less than 80 per cent of the Sun’s mass have been called Massive Compact Halo Objects or MACHOs for short because they are massive and could be used to explain the mass of halos.
An example of a MACHO is a brown dwarf. So far in my studies in science, I have never heard of a brown dwarf. Brown dwarfs are very much like planets, and have masses a few times greater than Jupiter’s mass. Although their masses are greater than Jupiter’s, they are actually smaller than Jupiter because they are so dense from the principles of quantum mechanics. Planets are held together by electromagnetic forces, but brown dwarfs follow Heisenberg’s Unicertainty Principle that accounts for the movement of particles as they try resist gravitational force. Brown dwarfs are very heavy, and because they account for such a great amount of mass, they can clearly be considered to be dark matter.
Black holes also possess characteristics of MACHOs. When light attempts to travel beyond its gravitational pull, it is restricted and pulled towards the centre of the gravitational force. A black hole is essentially an object with a radius equal to the Earth’s radius with the ability to restrict light. The point at which no light can escape is called the event horizon, causing objects to appear dark. Although it was believed that black holes were just a speculation- a mathematical speculation based on Einstein’s genera theory of relativity- there is evidence for their existence.
At a black hole’s surface, the gravitational pull is so powerful that it destroys the surrounding material, and separates it into constituents of energetic particles and radiation. Black holes are surrounded by light that can be viewed with x-ray telescopes. If this is so, can we correctly categorize black holes as MACHOs?
Brown dwarfs and black holes are definitely dark, but gravity makes it possible to see them- gravity works as a lens. Take, for example, a star shining in the distance, and a MACHO is passing in front of it. It is expected that it would cause and eclipse as it passes in front of the star, however, this is not the case. Instead, the MACHO deflects the light and focuses towards the Earth. Just as the MACHO passes in front of the star, the light is beamed at us and we can see the light. This effect is called microlensing and effectively deflects dark objects.
Although effective, there are two drawbacks to this method of identifying dark matter. First of all, stars change their brightness and dimness regularly. It is possible that in some cases, their twinkle may be confused with the passage of a MACHO. Secondly, microlensing is incredibly rare. To find such a event, an observer must observe several million stars over years and be in the right place at the right time to catch one of them twinkle.
Researchers have even postulated the existence of a dark matter particle, however, such a particle would be too light to detect or to clump together in the Sun’s core. These particles could potentially collide at the centre of the galaxy. In doing so, they would produce pairs of electrons and positrons eventually producing beams of photons.
Chapter 10: Gravity Sheds Light on the Invisible
When we say we see something, we are referring to how our eyes can detect and respond to light. This is called, “visible light.” When light enters our eyes, we can decompose any incoming light beams into electromagnetic waves with different wavelengths or frequencies. As we know, the human eye can only view light between the narrow range of wavelengths two fifths to seven fifths of a thousandth of a millimeter. However, we must remember that light waves have wavelengths that range from zero to infinity, the human just can’t detect given frequencies.
When we look into the night sky, we can see visible light emitted by stars. I have always wondered why planets appear so much brighter than stars. The truth is that planets reflect light from the sun, which makes then appear brighter than stars. When we observe the Universe in this way, we tend to believe that this is the Universe- this is what it is, but that’s simply not the case. When we look at the sky, we think we can perceive everything, but really, most of the Universe cannot be seen by the naked eye.
The 20th century revolutionized astronomy because astronomers began to view the Universe in wavelengths- wavelengths that were not detected by the human eye. Today, they still continue to do this, which is made possible by the conversion of one type of wavelength into another viewable form, like radio waves. Radios pick up electromagnetic waves with wavelengths greater than a few centimeters, emitted by a transmitter, and then converted into sound energy, which can be processed by the human ear.
In the 1930s, Karl Jansky, an engineer at the Bell Laboratories, showed that the Milky Way emitted radio waves. In the 20th century, after Jansky’s discovery, radio observations were used to view very distant objects. The development of radio telescopes has allowed for the detection of radio waves emitted by galaxies such as the Milky Way. Unlike conventional telescopes, radio telescopes can pick radio waves out of darkness.
Obviously the sky looks different when viewed through an optical telescope and a radio telescope, but the question is, how different? It’s common to think that we’ll observe the same picture that we perceive in the visible sky, but we won’t. Different physical processes emit different light frequencies, especially when there are temperature variations. With a normal optical telescope, we would believe that there is no activity in the invisible light regions, but when we view these areas with a radio telescope, we can interpret that they are actually full of radio waves. The fact of the matter is, the sky looks different, depending on how you look at it.
When we define the visible Universe, we have to be clear in our definition. Technically, the visible Universe is not only what we can see optically, but also what we can detect, like electromagnetic waves of varying wavelength. Using radio telescopes, scientists can detect waves like X-rays, and wavelengths that are a thousandth of a millionth of the wavelength of visible light.
Galaxies are not what they appear to be, they are actually much heavier and larger than they appear, but we are unable to identify what makes them so heavy. This unidentifiable mass is called dark matter. How much of the Universe is dark matter? Today it is believed that the Universe contains almost 100 times more dark matter than visible matter.
When we look into the night sky, we can see visible light emitted by stars. I have always wondered why planets appear so much brighter than stars. The truth is that planets reflect light from the sun, which makes then appear brighter than stars. When we observe the Universe in this way, we tend to believe that this is the Universe- this is what it is, but that’s simply not the case. When we look at the sky, we think we can perceive everything, but really, most of the Universe cannot be seen by the naked eye.
The 20th century revolutionized astronomy because astronomers began to view the Universe in wavelengths- wavelengths that were not detected by the human eye. Today, they still continue to do this, which is made possible by the conversion of one type of wavelength into another viewable form, like radio waves. Radios pick up electromagnetic waves with wavelengths greater than a few centimeters, emitted by a transmitter, and then converted into sound energy, which can be processed by the human ear.
In the 1930s, Karl Jansky, an engineer at the Bell Laboratories, showed that the Milky Way emitted radio waves. In the 20th century, after Jansky’s discovery, radio observations were used to view very distant objects. The development of radio telescopes has allowed for the detection of radio waves emitted by galaxies such as the Milky Way. Unlike conventional telescopes, radio telescopes can pick radio waves out of darkness.
Obviously the sky looks different when viewed through an optical telescope and a radio telescope, but the question is, how different? It’s common to think that we’ll observe the same picture that we perceive in the visible sky, but we won’t. Different physical processes emit different light frequencies, especially when there are temperature variations. With a normal optical telescope, we would believe that there is no activity in the invisible light regions, but when we view these areas with a radio telescope, we can interpret that they are actually full of radio waves. The fact of the matter is, the sky looks different, depending on how you look at it.
When we define the visible Universe, we have to be clear in our definition. Technically, the visible Universe is not only what we can see optically, but also what we can detect, like electromagnetic waves of varying wavelength. Using radio telescopes, scientists can detect waves like X-rays, and wavelengths that are a thousandth of a millionth of the wavelength of visible light.
Galaxies are not what they appear to be, they are actually much heavier and larger than they appear, but we are unable to identify what makes them so heavy. This unidentifiable mass is called dark matter. How much of the Universe is dark matter? Today it is believed that the Universe contains almost 100 times more dark matter than visible matter.
Chapter 9: The Fundamental Forces and the Origin of Matter
To fully understand the origin of matter, we must consider four forces: the electromagnetic, weak, strong, and gravitational forces. These forces are essential to understanding the composition of matter and matter’s composition in the Universe.
Each force plays a role in different physical phenomena. For example, the electromagnetic force is responsible for the electron’s attraction to the nucleus to form neutral atoms, ultimately dictating chemical reactions. The weak force governs radioactive decay, and the transformations of particles like the neutron into other particles like the proton. The strong force forms the nucleus by binding neutrons and protons together. Lastly, we are familiar with the gravitational force.
What we have figured out from the electromagnetic forces is that the combination of the electrical and magnetic fields is what we conventionally call radiation. Radiation has a particle-wave duality; it can be a particle, such as a photon, or it can be a wave, which we know is part of the electromagnetic field.
When we talk about Schrodinger’s equation, we talk about the Uncertainty Principle. When we talk about the Uncertainty Principle, we must also consider what is called spin in quantum mechanics. Spin describes a particle’s rotation. Take the electron as an example, it can spin clockwise or counterclockwise. Each type of particle has a characteristic spin in multiples of a half. Fermions are a class of particles characterized by their half-integer spins. These are particles like electrons, protons, and neutrons. Bosons are particles characterized by their integer spins. Photons are an example of bosons with spin values of positive or negative one.
Fermions and bosons are very distinct and different in behaviour. In chemistry class, we learned about fermions because we studied the Pauli Exclusion Principle, which states, “Two fermions can never have the same energy, spin, position, or other property, which is necessary to classify each individual particle.” When the Pauli Exclusion Principle is applied to an atom, it details how electrons are organized around a nucleus, dictating the s, p, d and f orbitals. The Pauli Exclusion Principle and the organization of electrons in an atom is responsible for the atomic spectra that is observed.
In comparison to fermions, bosons are not subjected to restrictions like the Pauli Exclusion Principle. Instead, they are allowed to occupy and energy level.
British Physicist Paul Dirac constructed a quantum equation for the electron. In his research to explain the electron’s behaviousr, he rationalized the existence of another particle, the positron, with quantum properties opposite to the electron’s properties. Like the electron, it is a fermion, but it is positively charged. Basically, Dirac discovered that all particles have anti-particles.
The strong force is the force that holds protons and neutrons together in the nucleus. It is much stronger than the electromagnetic force, and overcomes the repulsion between electrons. However, once you go beyond the radius of an atom, the electromagnetic force is stronger than the strong force.
It turns out that protons and neutrons are made up of basic constituents called quarks. Quarks have a spin of one half, but their electrical charges are multiples of one-third. A proton is made up of three quarks. It’s charge is calculated by adding up the charges on the three quarks to give a value of positive one. A neutron is also made up of three different quarks. When you add up the charges to calculate a neutron’s charge, the resulting charge is zero. The strong force acts on quarks, allowing them to form protons and neutrons.
The weak force is responsible for radioactive beta decay of a neutron into a proton. The weak force changes the nature of interacting particles. The neutrino, the massless particle, only interacts with other particles through the weak force.
When we study matter, we must also study anti-matter. For example, the electron’s anti-matter is the positron, for every quark, there is an anti-quark, and for every proton, there is an anti-proton. Dirac’s discovery has now led scientists to the discovery of anti-particles for all matter particles. For every particle, there is an anti-particle.
Each force plays a role in different physical phenomena. For example, the electromagnetic force is responsible for the electron’s attraction to the nucleus to form neutral atoms, ultimately dictating chemical reactions. The weak force governs radioactive decay, and the transformations of particles like the neutron into other particles like the proton. The strong force forms the nucleus by binding neutrons and protons together. Lastly, we are familiar with the gravitational force.
What we have figured out from the electromagnetic forces is that the combination of the electrical and magnetic fields is what we conventionally call radiation. Radiation has a particle-wave duality; it can be a particle, such as a photon, or it can be a wave, which we know is part of the electromagnetic field.
When we talk about Schrodinger’s equation, we talk about the Uncertainty Principle. When we talk about the Uncertainty Principle, we must also consider what is called spin in quantum mechanics. Spin describes a particle’s rotation. Take the electron as an example, it can spin clockwise or counterclockwise. Each type of particle has a characteristic spin in multiples of a half. Fermions are a class of particles characterized by their half-integer spins. These are particles like electrons, protons, and neutrons. Bosons are particles characterized by their integer spins. Photons are an example of bosons with spin values of positive or negative one.
Fermions and bosons are very distinct and different in behaviour. In chemistry class, we learned about fermions because we studied the Pauli Exclusion Principle, which states, “Two fermions can never have the same energy, spin, position, or other property, which is necessary to classify each individual particle.” When the Pauli Exclusion Principle is applied to an atom, it details how electrons are organized around a nucleus, dictating the s, p, d and f orbitals. The Pauli Exclusion Principle and the organization of electrons in an atom is responsible for the atomic spectra that is observed.
In comparison to fermions, bosons are not subjected to restrictions like the Pauli Exclusion Principle. Instead, they are allowed to occupy and energy level.
British Physicist Paul Dirac constructed a quantum equation for the electron. In his research to explain the electron’s behaviousr, he rationalized the existence of another particle, the positron, with quantum properties opposite to the electron’s properties. Like the electron, it is a fermion, but it is positively charged. Basically, Dirac discovered that all particles have anti-particles.
The strong force is the force that holds protons and neutrons together in the nucleus. It is much stronger than the electromagnetic force, and overcomes the repulsion between electrons. However, once you go beyond the radius of an atom, the electromagnetic force is stronger than the strong force.
It turns out that protons and neutrons are made up of basic constituents called quarks. Quarks have a spin of one half, but their electrical charges are multiples of one-third. A proton is made up of three quarks. It’s charge is calculated by adding up the charges on the three quarks to give a value of positive one. A neutron is also made up of three different quarks. When you add up the charges to calculate a neutron’s charge, the resulting charge is zero. The strong force acts on quarks, allowing them to form protons and neutrons.
The weak force is responsible for radioactive beta decay of a neutron into a proton. The weak force changes the nature of interacting particles. The neutrino, the massless particle, only interacts with other particles through the weak force.
When we study matter, we must also study anti-matter. For example, the electron’s anti-matter is the positron, for every quark, there is an anti-quark, and for every proton, there is an anti-proton. Dirac’s discovery has now led scientists to the discovery of anti-particles for all matter particles. For every particle, there is an anti-particle.
Chapter 8: The Alchemy of the Stars
Why do stars shine?
The Ultimate question, in my mind, is, “Why do stars shine?” Obviously, their shine is produced by light energy. Well, where does this light energy come from? The energy to power stars comes from nuclear fusion.
We know that an atom’s nucleus contains two particles: protons and neutrons. Indeed, the particles are held together by the strong force, a very powerful nuclear force, but it has limited range. The effect of the strong force is only felt when protons and neutrons are extremely close at distances less than a millionth of a billionth of a centimetre. The strong force has competition though. Take the helium atom for example. Helium’s nucleus has two protons, which cause an electromagnetic repulsion. However, if the nucleons are close enough, the strong force will overcome the repulsive electromagnetic force.
Nuclear fusion is “the capture by a nucleus of another proton or neutron as a source of energy.” This is called nuclear fusion because it is the fusion of lighter particles leads to the formation of one heavier particle. Consider the case of hydrogen and helium. Four hydrogen nuclei can form a helium nucleus, producing an extremely abundant source of energy. The four hydrogen nuclei have a greater total mass than the final helium nucleus. The excess mass present in the nucleus must be released by the structure. Einstein’s theory of general relativity outlined that energy and mass are interchangeable. If mass decreases, the total amount of energy increases.
Using the Sun as an example, through nuclear fusion, 10 per cent of the Sun’s mass can be converted from hydrogen to helium. If so, this tells us that at this rate, there is enough energy for the Sun to radiate at its current intensity for about 10 billion years. The Sun’s energy production is based on the fusion of hydrogen into helium. These estimates tell us that the Sun, a star, is approximately in the middle of its life cycle.
Quantum Tunneling in Stars
George Gamow defined quantum mechanics as an essential part of nuclear fusion in stars. Later came the “Uncertainty Principle” postulated by German Physicist, Werner Heinzberg. Heinzberg stated that, “We cannot know the exact position and the state of motion of any particle.” For example, if we placed an apple in a bowl, under the classical physics laws, we assume that this apple will not move because it is simply sitting in the bowl. In quantum mechanics, however, we cannot actually be certain of where the apple is, and how or where it is moving. All we know is that the apple is somewhere in the bowl.
We are not used to describing objects in terms of their positions and velocities, but in quantum mechanics, we have to consider that there is an uncertainty. There is only probability that the object is in a certain place or moving at a certain speed. We cannot predict the exact motion of an object or its destination; all we can do is predict the likelihood of various possible outcomes. Like Mr. Barry discussed in grade 12 chemistry, Schrodinger’s equations comes into play. Schrodinger’s equation gives us various possible outcomes and their likelihood at any given moment.
When understanding quantum mechanics, it deals with probability. Even though the apple is resting in the bowl at this specific instant, it is probable that eventually, the apple could be resting outside of the bowl.
The Ultimate question, in my mind, is, “Why do stars shine?” Obviously, their shine is produced by light energy. Well, where does this light energy come from? The energy to power stars comes from nuclear fusion.
We know that an atom’s nucleus contains two particles: protons and neutrons. Indeed, the particles are held together by the strong force, a very powerful nuclear force, but it has limited range. The effect of the strong force is only felt when protons and neutrons are extremely close at distances less than a millionth of a billionth of a centimetre. The strong force has competition though. Take the helium atom for example. Helium’s nucleus has two protons, which cause an electromagnetic repulsion. However, if the nucleons are close enough, the strong force will overcome the repulsive electromagnetic force.
Nuclear fusion is “the capture by a nucleus of another proton or neutron as a source of energy.” This is called nuclear fusion because it is the fusion of lighter particles leads to the formation of one heavier particle. Consider the case of hydrogen and helium. Four hydrogen nuclei can form a helium nucleus, producing an extremely abundant source of energy. The four hydrogen nuclei have a greater total mass than the final helium nucleus. The excess mass present in the nucleus must be released by the structure. Einstein’s theory of general relativity outlined that energy and mass are interchangeable. If mass decreases, the total amount of energy increases.
Using the Sun as an example, through nuclear fusion, 10 per cent of the Sun’s mass can be converted from hydrogen to helium. If so, this tells us that at this rate, there is enough energy for the Sun to radiate at its current intensity for about 10 billion years. The Sun’s energy production is based on the fusion of hydrogen into helium. These estimates tell us that the Sun, a star, is approximately in the middle of its life cycle.
Quantum Tunneling in Stars
George Gamow defined quantum mechanics as an essential part of nuclear fusion in stars. Later came the “Uncertainty Principle” postulated by German Physicist, Werner Heinzberg. Heinzberg stated that, “We cannot know the exact position and the state of motion of any particle.” For example, if we placed an apple in a bowl, under the classical physics laws, we assume that this apple will not move because it is simply sitting in the bowl. In quantum mechanics, however, we cannot actually be certain of where the apple is, and how or where it is moving. All we know is that the apple is somewhere in the bowl.
We are not used to describing objects in terms of their positions and velocities, but in quantum mechanics, we have to consider that there is an uncertainty. There is only probability that the object is in a certain place or moving at a certain speed. We cannot predict the exact motion of an object or its destination; all we can do is predict the likelihood of various possible outcomes. Like Mr. Barry discussed in grade 12 chemistry, Schrodinger’s equations comes into play. Schrodinger’s equation gives us various possible outcomes and their likelihood at any given moment.
When understanding quantum mechanics, it deals with probability. Even though the apple is resting in the bowl at this specific instant, it is probable that eventually, the apple could be resting outside of the bowl.
Chapter 7: The Origin of Light Elements in the Primeval Fireball
Nuclei, Elements, and Isotopes
An atom’s nucleus will have a definite number of protons and neutrons. Its electrical charge is determined by its number of protons. The atomic number gives the number of protons found in a nucleus, and the mass number gives the number of nucleons- protons and neutrons. However, it turns out that there can be slight variations I elements. These are called isotopes, and they are less common in nature than the element itself. For example, hydrogen has two sister nuclei- the deuterium nucleus and the tritium nucleus. The deuterium nucleus has one proton and one neutron, and the tritium nucleus has one proton and two neutrons. These isotopes are both heavier than hydrogen and less than a fiftieth of a per cent as abundant. The helium nucleus also has two isotopes. The helium has two protons and two neutrons. The isotope, helium-3, has one neutron. There are two heavier nuclei with four and six neutrons, however, these isotopes exist for less than a second.
After counting all of the atoms in the universe, it was found that 99 per cent of them are helium and hydrogen. Helium amounts for about 26 per cent of this total. It is crucial to understand even though there are many heavier elements in the Universe, helium and hydrogen are the most abundant. The origin of helium and hydrogen are crucial to the origin of the other elements found in the Universe.
Synthesizing Helium in the first three minutes of the Universe
Not only does the Universe consist of electrons, protons, neutrons and photons, it is known that the Universe also consists of positrons and neutrinos. Positrons are simply positively charged particles, but neutrinos, like photons, are particles that are almost massless. The number of neutrinos greatly outnumbers the number of protons and neutrons.
Particles are always undergoing transformations or metamorphosis from one particle to another. For example, if a proton collides with the anti-particle of a neutrino, it transforms into a neutron, and it then emits the electron’s anti-particle, the positron. Another reaction can also occur where a neutron collides with a neutrino and creates a proton, whereby releasing an electron. The transformation process is called beta decay. Beta decay, in the early Universe, is responsible for the conversion of protons and neutrons into one another.
The Principle of Thermal Equilibrium is responsible for the variety and proportions o light elements that we see today. The combination and transformations of elements such as hydrogen and helium are responsible for the formation of all the elements. In the early Universe, helium was found. The entire process took just over three minutes, and the result of these collisions was the Universe that we still observe today.
An atom’s nucleus will have a definite number of protons and neutrons. Its electrical charge is determined by its number of protons. The atomic number gives the number of protons found in a nucleus, and the mass number gives the number of nucleons- protons and neutrons. However, it turns out that there can be slight variations I elements. These are called isotopes, and they are less common in nature than the element itself. For example, hydrogen has two sister nuclei- the deuterium nucleus and the tritium nucleus. The deuterium nucleus has one proton and one neutron, and the tritium nucleus has one proton and two neutrons. These isotopes are both heavier than hydrogen and less than a fiftieth of a per cent as abundant. The helium nucleus also has two isotopes. The helium has two protons and two neutrons. The isotope, helium-3, has one neutron. There are two heavier nuclei with four and six neutrons, however, these isotopes exist for less than a second.
After counting all of the atoms in the universe, it was found that 99 per cent of them are helium and hydrogen. Helium amounts for about 26 per cent of this total. It is crucial to understand even though there are many heavier elements in the Universe, helium and hydrogen are the most abundant. The origin of helium and hydrogen are crucial to the origin of the other elements found in the Universe.
Synthesizing Helium in the first three minutes of the Universe
Not only does the Universe consist of electrons, protons, neutrons and photons, it is known that the Universe also consists of positrons and neutrinos. Positrons are simply positively charged particles, but neutrinos, like photons, are particles that are almost massless. The number of neutrinos greatly outnumbers the number of protons and neutrons.
Particles are always undergoing transformations or metamorphosis from one particle to another. For example, if a proton collides with the anti-particle of a neutrino, it transforms into a neutron, and it then emits the electron’s anti-particle, the positron. Another reaction can also occur where a neutron collides with a neutrino and creates a proton, whereby releasing an electron. The transformation process is called beta decay. Beta decay, in the early Universe, is responsible for the conversion of protons and neutrons into one another.
The Principle of Thermal Equilibrium is responsible for the variety and proportions o light elements that we see today. The combination and transformations of elements such as hydrogen and helium are responsible for the formation of all the elements. In the early Universe, helium was found. The entire process took just over three minutes, and the result of these collisions was the Universe that we still observe today.
Chapter 6: Chapter 6: A Hot Beginning and the Cosmic Photosphere
The Energy Density of Matter and Radiation in the early Universe
Interestingly enough, chapter six deals with the cosmic photosphere. The beginning of the chapter outlines the basic fundamental structure of the atom.
The Universe we observe is a combination of a series of chemical elements, each one with a unique atomic structure. An atom has a nucleus, which is orbited by many electrons. The nucleus holds most of the mass of the atom, however, compared to its mass ratio with the rest of the atom, it only occupies a very minute amount of space in the atom. For example, hydrogen’s nucleus is 99.5 per cent of its total mass, and it is orbited by one electron. The radius of its nucleus however, is 100,000 times smaller than the radius of the entire atom. Personally, I think that it is amazing that something so small is even a measurable quantity. It’s pretty fascinating to know that scientists are even able to measure values that are that small.
As it turns out, although the Universe is made up of many well-known identifiable elements, 99 per cent of the visible universe is actually made up of hydrogen and helium, the two simplest elements. It is well known that the evolution of the Universe is a consequence of the way radiation and atoms interact at high temperatures. Scientists have a general idea of how much energy in the Universe is in atomic form, and how much energy is in the form of radiation.
A quick estimate says that there are roughly one billion galaxies in the Universe, each containing about 100 billion stars. It is assumed that many of these stars and galaxies are composed of hydrogen atoms. From this knowledge, we can estimate that there are a few hydrogen atoms per every cubic metre. This concept is hard to imagine considering that we are and everything else is composed of an infinite number of atoms- there are not that many atoms around compared to the size of the Universe.
In comparison, the Universe is littered with photons. Roughly one billion photons can be found in a cubic metre- this number is much larger than the number of atoms we find in the observable Universe. Now when we picture the Universe, we can picture it consisting mostly of radiation, with a scattered amount of atoms.
Interestingly enough, chapter six deals with the cosmic photosphere. The beginning of the chapter outlines the basic fundamental structure of the atom.
The Universe we observe is a combination of a series of chemical elements, each one with a unique atomic structure. An atom has a nucleus, which is orbited by many electrons. The nucleus holds most of the mass of the atom, however, compared to its mass ratio with the rest of the atom, it only occupies a very minute amount of space in the atom. For example, hydrogen’s nucleus is 99.5 per cent of its total mass, and it is orbited by one electron. The radius of its nucleus however, is 100,000 times smaller than the radius of the entire atom. Personally, I think that it is amazing that something so small is even a measurable quantity. It’s pretty fascinating to know that scientists are even able to measure values that are that small.
As it turns out, although the Universe is made up of many well-known identifiable elements, 99 per cent of the visible universe is actually made up of hydrogen and helium, the two simplest elements. It is well known that the evolution of the Universe is a consequence of the way radiation and atoms interact at high temperatures. Scientists have a general idea of how much energy in the Universe is in atomic form, and how much energy is in the form of radiation.
A quick estimate says that there are roughly one billion galaxies in the Universe, each containing about 100 billion stars. It is assumed that many of these stars and galaxies are composed of hydrogen atoms. From this knowledge, we can estimate that there are a few hydrogen atoms per every cubic metre. This concept is hard to imagine considering that we are and everything else is composed of an infinite number of atoms- there are not that many atoms around compared to the size of the Universe.
In comparison, the Universe is littered with photons. Roughly one billion photons can be found in a cubic metre- this number is much larger than the number of atoms we find in the observable Universe. Now when we picture the Universe, we can picture it consisting mostly of radiation, with a scattered amount of atoms.
Chapter 5: The Recession of Distant Galaxies
American Astronomer, Vesto Slipher, attempted to determine the distance to faraway objects, specifically galaxies. Slipher’s observations were of spectral lines corresponding to specific galaxies. It is known that each element has a highly distinctive set of spectral lines. Each line represents the transition between energy levels of an atom or molecules.
Slipher’s biggest observation was the Andromeda Galaxy, and he observed its spectrum. Its spectrum had elements well known in the laboratory. Although the positions of the lines were familiar, he observed that the spectral lines were situated at shorter wavelengths than what had been measured in the laboratory. When light moves towards us or away from us, a phenomenon takes place, which changes our perception of the light we are receiving. The wavelength of light appears to be shorter than its actual length. The speed of light remains the same, but the separation between the crests and the troughs of the waves are shorter. We then perceive the effect as a colour change in the light source, and it appears bluer. Technically speaking, the light has been blue-shifted.
There is another phenomenon, which we must consider. This time, suppose that light is being emitted from a farther distance. As the light rays travels towards us, the expansion of the Universe will cause their wavelengths to be stretched. Based on the time that each light ray has been traveling, it will dictate how the wavelengths have changed. Slipher had documented red shifts, which corresponds to distant light sources. The farther away a light source is, the longer their light rays will take to reach the earth, therefore, the more stretched their wavelengths will be. The cosmological red shift refers to distant objects and the fact that they have a larger change in wavelength than closer objects do because of the distance they have to travel.
Slipher’s measurement of Andromeda’s spectra indicated that it is moving towards the earth. Obviously, Andromeda’s spectra was blue-shifted, which meant that it was moving towards us at a speed of 300 kilometres per second, the largest velocity recorded at that time. Slipher’s observation of other galaxies showed that most other galaxies were moving away from Earth. In essence, their spectra were red-shifted. Based on his observations, Slipher believed that the galaxy was drifting with respect to other galaxies because he thought that there were larger velocities on one side of the galaxy. Continued measurements showed that the recession of distant galaxies was the same in all directions. Slipher’s method for obtaining atomis spectra was time consuming- it took him two years to observe and record 15 spectra. 13 of these spectra were red-shifted and receding from Earth at speeds over 1000 kilometres per second. By the end of the next 10 years, Slipher had recorded data for more than 30 red shifts. His observations allowed him to conclude that brighter galaxies have smaller red shifts, and fainter galaxies have larger red shifts. The implications of Slipher’s results were that the further galaxies were receding at speeds greater than the closer ones, lending evidence to the theory of an expanding universe.
Slipher’s biggest observation was the Andromeda Galaxy, and he observed its spectrum. Its spectrum had elements well known in the laboratory. Although the positions of the lines were familiar, he observed that the spectral lines were situated at shorter wavelengths than what had been measured in the laboratory. When light moves towards us or away from us, a phenomenon takes place, which changes our perception of the light we are receiving. The wavelength of light appears to be shorter than its actual length. The speed of light remains the same, but the separation between the crests and the troughs of the waves are shorter. We then perceive the effect as a colour change in the light source, and it appears bluer. Technically speaking, the light has been blue-shifted.
There is another phenomenon, which we must consider. This time, suppose that light is being emitted from a farther distance. As the light rays travels towards us, the expansion of the Universe will cause their wavelengths to be stretched. Based on the time that each light ray has been traveling, it will dictate how the wavelengths have changed. Slipher had documented red shifts, which corresponds to distant light sources. The farther away a light source is, the longer their light rays will take to reach the earth, therefore, the more stretched their wavelengths will be. The cosmological red shift refers to distant objects and the fact that they have a larger change in wavelength than closer objects do because of the distance they have to travel.
Slipher’s measurement of Andromeda’s spectra indicated that it is moving towards the earth. Obviously, Andromeda’s spectra was blue-shifted, which meant that it was moving towards us at a speed of 300 kilometres per second, the largest velocity recorded at that time. Slipher’s observation of other galaxies showed that most other galaxies were moving away from Earth. In essence, their spectra were red-shifted. Based on his observations, Slipher believed that the galaxy was drifting with respect to other galaxies because he thought that there were larger velocities on one side of the galaxy. Continued measurements showed that the recession of distant galaxies was the same in all directions. Slipher’s method for obtaining atomis spectra was time consuming- it took him two years to observe and record 15 spectra. 13 of these spectra were red-shifted and receding from Earth at speeds over 1000 kilometres per second. By the end of the next 10 years, Slipher had recorded data for more than 30 red shifts. His observations allowed him to conclude that brighter galaxies have smaller red shifts, and fainter galaxies have larger red shifts. The implications of Slipher’s results were that the further galaxies were receding at speeds greater than the closer ones, lending evidence to the theory of an expanding universe.
Chapter 4: An Evolving Universe
The Cosmological Principle, Evolution, and Change
There is nothing exceptional about our place in the Universe; everything in the Universe looks the same. This was originally titled “The Copernican Principle,” but it was later renamed “The Cosmological Principle”. The Cosmological Principle states that regardless of where we are in the Universe, everything looks identical. The principle implies that the Universe is homogeneous. Any measured physical quantity at a random point in the Universe will always have that give value at the same time. It allows us to say that the universe is smooth.
It is inappropriate to assume that everything in the Universe is smooth because everything has a texture. Regardless of how smooth things may be, they will never be perfectly smooth. Even when we view the stars, the sky appears smooth, but it is not smooth- it is scattered with stars and astronomical clusters. Therefore, the Universe is definitely not smooth. Even though the Cosmological Principle insists that it is smooth, and we know that it isn’t, we can still study the properties of the Universe as if it were smooth on such a large scale.
Assisted by the Cosmological Principle, the Universe looks the same wherever we are in reference to the fact that the Universe does not have a centre, nor does it have edges. The Cosmological Principle pays not attention to the large-scale structure of the Universe, but it is a crucial factor in understanding the Universe’s evolutionary history.
When the word evolution is used, it means that there has been a change over time; not necessarily that something has evolved. What can be said about the Universe- has it evolved or has it merely changed over time? Take the stars, for example. When you look at the stars, it appears that there is no change- there is no motion. Now look at the Earth and the other planets, they are always moving in their orbits, and they sky appears different at different times of the year. But really, it maintains its normal state. Considering the state of the Universe at this point, each planet revolves around the Sun, situated at a specific distance from it, where they have been situated for the past five billion years. It is true that stars do move- they have velocities, which cause a shift in angular positions in the sky. However, despite the changes the Universe undergoes, it is simply changing with respect to time, not evolving.
Newton’s belief in a static universe caused him to reconstruct his theory of gravity. What wasn’t recognized was gravity’s attractive nature. A concentration of mass at the centre of space would tend to pull everything towards it. With this idea, Newton boasted, that in a finite universe all exterior matter would be attracted to this central matter and would fall towards this central matter. However, he refused to accept this for the entire Universe, so he then conjured that all matter was evenly disposed in an infinite space. This prevented the collapse of matter because it was evenly dispersed in the Universe and in a state of equilibrium. Although Newton was insightful, his new idea was not applicable to the concept of gravity. It was not until Einstein’s general theory of relativity that it became clear that the Universe was and is evolving.
There is nothing exceptional about our place in the Universe; everything in the Universe looks the same. This was originally titled “The Copernican Principle,” but it was later renamed “The Cosmological Principle”. The Cosmological Principle states that regardless of where we are in the Universe, everything looks identical. The principle implies that the Universe is homogeneous. Any measured physical quantity at a random point in the Universe will always have that give value at the same time. It allows us to say that the universe is smooth.
It is inappropriate to assume that everything in the Universe is smooth because everything has a texture. Regardless of how smooth things may be, they will never be perfectly smooth. Even when we view the stars, the sky appears smooth, but it is not smooth- it is scattered with stars and astronomical clusters. Therefore, the Universe is definitely not smooth. Even though the Cosmological Principle insists that it is smooth, and we know that it isn’t, we can still study the properties of the Universe as if it were smooth on such a large scale.
Assisted by the Cosmological Principle, the Universe looks the same wherever we are in reference to the fact that the Universe does not have a centre, nor does it have edges. The Cosmological Principle pays not attention to the large-scale structure of the Universe, but it is a crucial factor in understanding the Universe’s evolutionary history.
When the word evolution is used, it means that there has been a change over time; not necessarily that something has evolved. What can be said about the Universe- has it evolved or has it merely changed over time? Take the stars, for example. When you look at the stars, it appears that there is no change- there is no motion. Now look at the Earth and the other planets, they are always moving in their orbits, and they sky appears different at different times of the year. But really, it maintains its normal state. Considering the state of the Universe at this point, each planet revolves around the Sun, situated at a specific distance from it, where they have been situated for the past five billion years. It is true that stars do move- they have velocities, which cause a shift in angular positions in the sky. However, despite the changes the Universe undergoes, it is simply changing with respect to time, not evolving.
Newton’s belief in a static universe caused him to reconstruct his theory of gravity. What wasn’t recognized was gravity’s attractive nature. A concentration of mass at the centre of space would tend to pull everything towards it. With this idea, Newton boasted, that in a finite universe all exterior matter would be attracted to this central matter and would fall towards this central matter. However, he refused to accept this for the entire Universe, so he then conjured that all matter was evenly disposed in an infinite space. This prevented the collapse of matter because it was evenly dispersed in the Universe and in a state of equilibrium. Although Newton was insightful, his new idea was not applicable to the concept of gravity. It was not until Einstein’s general theory of relativity that it became clear that the Universe was and is evolving.
Chapter 3: Albert Einstein and the Geometry of Space and Time
A New View of Gravity: The General Theory of Relativity
Albert Einstein, one of the most famous men of all-time, developed his special theory of relativity that discussed electromagnetism and mechanics. In his theory he postulated two things:
a) “The laws of physics are identical in any reference frame moving at a constant speed.”
b) “The speed of light is the same in all reference frames.”
Although Einstein’s special theory of relativity unified mechanical and electromagnetic forces, he did not discuss Newton’s proposed gravitational forces. Einstein’s general theory of relativity was developed after he made two cunning observations. First, he observed that the gravitational mass of an object is related to its inertial mass. Secondly, he observed that a gravitational field could be mimicked in gravity’s absence by accelerating a reference frame. Based on Newton’s theories, the gravitational force exerted on an object depends on the object’s mass, defined as the gravitational mass. Newton’s proposal was that objects respond to forces by accelerating. Newton’s second law states that force equals mass multiplied by acceleration. For example, an object twice the mass of another object will undergo half the acceleration if subjected to the same force. However, this is not so because we know that two objects dropped from the same height will hit the ground at the same time. Take the classic example of the brick and the feather for example. The brick has a larger gravitational mass and is pulled stronger by the gravitational force, however, the feather has a larger inertial mass, but it is not as quick to respond to a given force. The force applied to the brick is the same as the feather, but it responds at a much slower rate than the feather. That is why they have the same acceleration.
Einstein’s connection between gravity and accelerated reference frames led to his general theory of relativity. After his new development, he proposed the equivalence principle, which states “the laws of physics in a gravitational field are the same as in an accelerated reference frame.” With this knowledge, Einstein said that it was now possible to mimic the effects of gravity in a reference frame, which is not subjected to gravitational forces. The special theory of relativity notes that mass can be converted into energy. In the general theory of relativity, energy and mass respond to gravity. Gravity affects the motion of light. Based on this discovery, it is possible to detect the effect just by studying the stars.
Albert Einstein, one of the most famous men of all-time, developed his special theory of relativity that discussed electromagnetism and mechanics. In his theory he postulated two things:
a) “The laws of physics are identical in any reference frame moving at a constant speed.”
b) “The speed of light is the same in all reference frames.”
Although Einstein’s special theory of relativity unified mechanical and electromagnetic forces, he did not discuss Newton’s proposed gravitational forces. Einstein’s general theory of relativity was developed after he made two cunning observations. First, he observed that the gravitational mass of an object is related to its inertial mass. Secondly, he observed that a gravitational field could be mimicked in gravity’s absence by accelerating a reference frame. Based on Newton’s theories, the gravitational force exerted on an object depends on the object’s mass, defined as the gravitational mass. Newton’s proposal was that objects respond to forces by accelerating. Newton’s second law states that force equals mass multiplied by acceleration. For example, an object twice the mass of another object will undergo half the acceleration if subjected to the same force. However, this is not so because we know that two objects dropped from the same height will hit the ground at the same time. Take the classic example of the brick and the feather for example. The brick has a larger gravitational mass and is pulled stronger by the gravitational force, however, the feather has a larger inertial mass, but it is not as quick to respond to a given force. The force applied to the brick is the same as the feather, but it responds at a much slower rate than the feather. That is why they have the same acceleration.
Einstein’s connection between gravity and accelerated reference frames led to his general theory of relativity. After his new development, he proposed the equivalence principle, which states “the laws of physics in a gravitational field are the same as in an accelerated reference frame.” With this knowledge, Einstein said that it was now possible to mimic the effects of gravity in a reference frame, which is not subjected to gravitational forces. The special theory of relativity notes that mass can be converted into energy. In the general theory of relativity, energy and mass respond to gravity. Gravity affects the motion of light. Based on this discovery, it is possible to detect the effect just by studying the stars.
Chapter 2: How High is the SKY?
“How high is the sky?” This is a question that has pondered many people over the centuries. Within that question lies many others such as, “How far are the planets?” or, “Why are the stars so far away?” When the sky is examined and these questions are asked, distances can be explained in terms of light years. A light year is the distance traveled by a light ray, at a speed of 300,000 kilometres per second over a span of one year. For example, the Sun is eight light minutes away.
Before light years were understood, observers, such as the Greeks, used parallax to estimate the distance to a planet or star. During the 17th century, Johannes Kepler constructed a scale model of the solar system by mapping positions of the planets relative to the Earth as they orbited the Sun. Based on astronomer Tacho Brahe’s observations of Mars’ elliptical orbit around the Sun, Kepler developed three laws that are still highly regarded today.
Kepler’s First Law: Planets follow elliptical orbits with the Sun at one focus.
Kepler’s Second Law: The closer a planet is to the Sun, the faster it moves.
Kepler’s Third Law: “The ratio of the squares of the period of time required for any two planets to complete an orbit of the Sun is proportional to the ratio of the cubes of their average distances from the Sun.”
His third law was very important. If one planet’s distance from the Sun was known, it was possible to determine the distance of any other planets from the Sun. Ultimately, we could then determine the size of the solar system.
To determine the solar system’s size, a group of astronomer’s among them Edmund Halley, proposed that Venus’s transit in front of the Sun could be used to determine the distance between Earth and the Sun. Although Venus’ orbit is slightly tilted compared to Earth’s orbit about the Sun, it can still be seen crossing in front of the Sun roughly every 100 years. In recording the path of Venus from two different locations on Earth, the parallax method could be used to find Earth’s distance from the Sun. Venus’ track would be displaced when viewed from different places on Earth, which can be compared to the Sun’s angular size. The distance between Venus and the Earth could be determined, and using Kepler’s third law, the distance between the Earth and the Sun could be determined. The distance from the Earth to the Sun is roughly 150 million kilometres.
Based on this knowledge, parallax methods could be used to determine distances beyond the solar system. Observations made from the surface of the Earth limit the distance to less than 10,000 kilometres, however, if the Earth’s motion through space is used, further distances can be determined. By allowing rotation of the Earth and recording observations from two different points during orbit, the viewing distance becomes millions of kilometres. The most effective observations are made at six months when the Earth has completed half of its orbit, corresponding to an observational distance of about 300 million kilometres.
The understanding and use of parallax is very important. In 1840, parallax was used by Friedrich Bessel to measure the distance to a star, which was 11 light years away. However, it was soon realized that far distances were much harder to measure because it was too difficult to measure angular positions in the sky. Distances outside of our galaxy could not be measured- the farthest within our galaxy was only 160 light years away.
Even though it cannot be accurately used to measure far distances, the parallax method can be used to construct a rough scale. Parallax is still important. In 1989, a Hipparcos satellite was launched to measure parallitic distances for over 100,000 stars. Over three years, catalogues of material were collected, and today it is still used as a primary reference and standard for determining astronomical distances.
Before light years were understood, observers, such as the Greeks, used parallax to estimate the distance to a planet or star. During the 17th century, Johannes Kepler constructed a scale model of the solar system by mapping positions of the planets relative to the Earth as they orbited the Sun. Based on astronomer Tacho Brahe’s observations of Mars’ elliptical orbit around the Sun, Kepler developed three laws that are still highly regarded today.
Kepler’s First Law: Planets follow elliptical orbits with the Sun at one focus.
Kepler’s Second Law: The closer a planet is to the Sun, the faster it moves.
Kepler’s Third Law: “The ratio of the squares of the period of time required for any two planets to complete an orbit of the Sun is proportional to the ratio of the cubes of their average distances from the Sun.”
His third law was very important. If one planet’s distance from the Sun was known, it was possible to determine the distance of any other planets from the Sun. Ultimately, we could then determine the size of the solar system.
To determine the solar system’s size, a group of astronomer’s among them Edmund Halley, proposed that Venus’s transit in front of the Sun could be used to determine the distance between Earth and the Sun. Although Venus’ orbit is slightly tilted compared to Earth’s orbit about the Sun, it can still be seen crossing in front of the Sun roughly every 100 years. In recording the path of Venus from two different locations on Earth, the parallax method could be used to find Earth’s distance from the Sun. Venus’ track would be displaced when viewed from different places on Earth, which can be compared to the Sun’s angular size. The distance between Venus and the Earth could be determined, and using Kepler’s third law, the distance between the Earth and the Sun could be determined. The distance from the Earth to the Sun is roughly 150 million kilometres.
Based on this knowledge, parallax methods could be used to determine distances beyond the solar system. Observations made from the surface of the Earth limit the distance to less than 10,000 kilometres, however, if the Earth’s motion through space is used, further distances can be determined. By allowing rotation of the Earth and recording observations from two different points during orbit, the viewing distance becomes millions of kilometres. The most effective observations are made at six months when the Earth has completed half of its orbit, corresponding to an observational distance of about 300 million kilometres.
The understanding and use of parallax is very important. In 1840, parallax was used by Friedrich Bessel to measure the distance to a star, which was 11 light years away. However, it was soon realized that far distances were much harder to measure because it was too difficult to measure angular positions in the sky. Distances outside of our galaxy could not be measured- the farthest within our galaxy was only 160 light years away.
Even though it cannot be accurately used to measure far distances, the parallax method can be used to construct a rough scale. Parallax is still important. In 1989, a Hipparcos satellite was launched to measure parallitic distances for over 100,000 stars. Over three years, catalogues of material were collected, and today it is still used as a primary reference and standard for determining astronomical distances.
Chapter 1: A Mechanical Universe
People often question, “What is the universe? Where did it come from? How does it exist?” The truth is that the universe is still not entirely understood. Over the years, philosophers, physicists, scientists, and even historians have tried to explain the phenomenon. They have tried to explain cosmology. Cosmology is the study of the origin and evolution of the universe. Cosmological history originates with the Greeks and their Earth-centred universe, followed by Copernicus and Galileo and their Sun-centred universe, and finally Newton’s laws that present a new outlook on understanding the state of the universe.
Although Isaac Newton was the man who revolutionized theoretical physics and developed the three laws of motion and the universal gravity law, Galileo Galilei was a very important man at the time. Nicolaus Copernicus hypothesized that the universe revolved around the sun; he called his model “The Heliocentric Universe,” which was based on Aristarchus of Samos’ model of the heliocentric universe, however, Copernicus believed that there was more to understanding the universe than Aristarchus had outlined and decided to reconstruct the heliocentric model.
Copernicus, like many others, used the sphere to construct his universe model because of its perfect geometric construction. Copernicus believed that the universe could not be centred around the Earth, but rather that the Earth rotated around a fixed centre. Based on the heliocentric model, the retrogression of planets is easily explained. Logically explained by the model, Venus and Mercury are often seen near dusk or dawn because they have tight orbits around the sun.
After three decades, Copernicus was able to confidently declare his model of the Universe. Although it was accurate, it did not account for the epicycles eccentric orbits of some planets. Copernicus’ model of the universe was widely accepted by scholars of the day because the Earth was no longer targeted as the centre of the cosmos.
Galileo’s work at the beginning of the 17th century greatly contributed to the Copernican model of the universe. First, he discovered that the planet Venus has phases like the Moon. At different times during the month, the Moon shines because it reflects light from the Sun. Based on the position of the Moon, an observer situated on Earth will recognize different phases of the Moon. Galileo’s observations of Venus relative to the Earth and Sun showed that Venus undergoes phases as does the Moon, however, they are only logically explained if the Sun lies closer to the Earth than to Venus. Basically, the Sun illuminates Venus, which in turn shares light with Earth. Galileo’s observations prove that Venus is not orbiting the Earth, but rather that it is orbiting the Sun, which was a step closer to understanding that the Universe is heliocentric.
Galileo always defended his model and argued that, in fact, the Universe was heliocentric.
Although Galileo was fascinated by the cosmos, he proceeded to study the laws of motion. In particular, Galileo was influential in the development of understanding the laws of motion. Aristotle’s idea was that objects tend to stay still until a force acts on the object, which causes it to have motion. Galileo’s later work outlines the motion of a projectile along a parabolic path. Galileo was able to describe parabolic trajectory by separating angular motion into two motions- horizontal and vertical motions. His breakthrough in motion marked a turning point in Western physics. It was also Galileo who initially proposed that the Earth pulls masses towards it with a constant acceleration.
The work of Kepler, Copernicus and Galileo, led Isaac Newton to unite their theories and conjure the universal gravitation constant. Newton’s three laws of motion are the foundation for the study of motion in modern-day physics.
Although Isaac Newton was the man who revolutionized theoretical physics and developed the three laws of motion and the universal gravity law, Galileo Galilei was a very important man at the time. Nicolaus Copernicus hypothesized that the universe revolved around the sun; he called his model “The Heliocentric Universe,” which was based on Aristarchus of Samos’ model of the heliocentric universe, however, Copernicus believed that there was more to understanding the universe than Aristarchus had outlined and decided to reconstruct the heliocentric model.
Copernicus, like many others, used the sphere to construct his universe model because of its perfect geometric construction. Copernicus believed that the universe could not be centred around the Earth, but rather that the Earth rotated around a fixed centre. Based on the heliocentric model, the retrogression of planets is easily explained. Logically explained by the model, Venus and Mercury are often seen near dusk or dawn because they have tight orbits around the sun.
After three decades, Copernicus was able to confidently declare his model of the Universe. Although it was accurate, it did not account for the epicycles eccentric orbits of some planets. Copernicus’ model of the universe was widely accepted by scholars of the day because the Earth was no longer targeted as the centre of the cosmos.
Galileo’s work at the beginning of the 17th century greatly contributed to the Copernican model of the universe. First, he discovered that the planet Venus has phases like the Moon. At different times during the month, the Moon shines because it reflects light from the Sun. Based on the position of the Moon, an observer situated on Earth will recognize different phases of the Moon. Galileo’s observations of Venus relative to the Earth and Sun showed that Venus undergoes phases as does the Moon, however, they are only logically explained if the Sun lies closer to the Earth than to Venus. Basically, the Sun illuminates Venus, which in turn shares light with Earth. Galileo’s observations prove that Venus is not orbiting the Earth, but rather that it is orbiting the Sun, which was a step closer to understanding that the Universe is heliocentric.
Galileo always defended his model and argued that, in fact, the Universe was heliocentric.
Although Galileo was fascinated by the cosmos, he proceeded to study the laws of motion. In particular, Galileo was influential in the development of understanding the laws of motion. Aristotle’s idea was that objects tend to stay still until a force acts on the object, which causes it to have motion. Galileo’s later work outlines the motion of a projectile along a parabolic path. Galileo was able to describe parabolic trajectory by separating angular motion into two motions- horizontal and vertical motions. His breakthrough in motion marked a turning point in Western physics. It was also Galileo who initially proposed that the Earth pulls masses towards it with a constant acceleration.
The work of Kepler, Copernicus and Galileo, led Isaac Newton to unite their theories and conjure the universal gravitation constant. Newton’s three laws of motion are the foundation for the study of motion in modern-day physics.
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