Chapter 11: Conclusion

We as humans are born with curiosity, curiosity that leads us to explore the world around us. We want to know about everything that is around us including the infinitely large universe. Many theories about the universe have tried to explain the behavior of it. There are theories to explain how the universe was created and how the universe might end. Some theories have even proposed that the universe has no beginning or end. Other theories have explored the uncertainties about black holes and other celestial bodies. Some scientists have even considered the existence of a master theory that could explain everything that happens in the universe quantitatively. As more discoveries about the world around us are being made, theories are being modified or disregarded and new theories are being formed. But there are still many aspects of the universe that remain invisible to us. Although we may never know everything about the universe and even if a unified theory is never discovered, one thing will always remain the same. We will continue to explore all the aspects of life and the universe that is within our comprehension. 

Chapter 10: The Unification of Physics

It is extremely difficult to create a complete theory to describe everything that happens in the universe. Because of this, several smaller theories with limited ranges have been developed. The unification of physics describes a theory that could combine all the smaller theories into one detailed theory. Einstein spent most of his scientific career trying to find this combined theory, but as we can tell, he was unsuccessful. The discovery of the atomic structure and the uncertainty principle ended the popular idea that everything could be explained by examining the properties of the matter. However, the discovery of a unified would put an end to the uncertainty principle. The uncertainty principle of quantum mechanics states that we cannot know everything that occurs in the universe without having some amount of uncertainty about it, so it would contradict the unified theory. The strength of gravity and the quantity of the cosmological constant must be modified in order for the uncertainty principle to fit in with the theory of general relativity. In 1984, new theories called string theories emerged. These theories explain that particles have length but no dimension. The term string came form the example of an infinitely thing piece of string. The string theory was technically invented in the 1960s, and it said that particles such as protons can be described as waves on the string. Theories are constantly evolving based on knew observations and scientific discoveries. One day, we may discover a master theory that could explain all the theories in one accurate calculation. On the same note, we could also discover that such a theory cannot exist or that we do not have the correct tools to make an accurate calculation. Although we may never fully understand everything there is to know about the universe, we can try to understand all that can be measured in the areas of our knowledge.

Chapter 9: The Arrow of Time

The idea that time could be measured as a set quantity led to the theory of relativity. It is true that time is measured based on perspective. Time for one person that is standing still will be different from time for another person that is in motion or on something that is moving. In "imaginary" time, it is safe to say that if one is moving forward in time, one must also be able to move backward in time. There should not be a difference the back and forth direction of "imaginary time." However, in real time, there is a huge difference between the two directions. We can recall the past but not the future. Time is also directly related to the entropy of the universe. The increase of entropy with time is one example of the arrow of time. There are three known arrows of time. One of the other arrows of time deals with thermodynamics, and the direction of time with a given amount of entropy. As stated in the second law of thermodynamics, the amount of disorder in a system outweighs the amount of order. The early life stages of the universe were probably marked with many disorderly systems and very few orderly systems. If this were true, than it would make sense that the entropy of the universe would be decreasing with time. As time goes on, the entropy of the universe will continue to decrease while the order of the systems in the universe will continue to increase.

As time goes on, the entropy of the universe will continue to decrease while the order of the systems in the universe will continue to increase. The theory of general relativity cannot foretell how the universe began because the laws we have now would be null and void at the point of the big bang. The universe could have started organized and smooth just as easily as could have started out disorderly. Since the amount of disorder has not reached the point of total entropy, we can assume that entropy does not increase with time. It can only decrease or remain constant at the same level. The existence of the thermodynamic arrow of time can be explained if the universe started out with little entropy that steadily increased with time. If the collapse of a star could be compared to the collapse of the universe, than the amount of entropy should decrease as time goes on for both. The conclusion that the universe has no boundary is accurate because it would have had to have orderly when it was created in order for the entropy to decrease with time. The three arrows of time help differentiate the past and the future. They summarize the direction of time and how it relates to the amount of entropy in the universe. 

Chapter 7 and Chapter 8

Black Holes Ain't So Black

The edge of a black hole is merely rays of light that are too close to escape but far enough to avoid the gravitational pull of the black hole. But if these light rays were to come in to contact with one another, they would be subject to the power of the black hole, and would therefore be pulled into it. If two black holes were close enough to one another, they will eventually form a single black hole that was either larger or equal to the size of the two original black holes combined. The fact that a black hole can never decrease in size corresponds to its entropy (measures the amount of disorder of a system). The second law of thermodynamics states that the entropy of an isolated system always increases, and that when two systems combine to form one system, the entropy of the new system is is greater than the sum of the entropies of the parent systems. If the universe around a system is losing matter and energy, that the system must be gaining the matter and energy from its surroundings. Based on the second law of thermodynamics, black holes should be gaining energy and matter because its surroundings are losing matter/ energy. Because we cannot study the entropy of a black hole, we can only assume that it would be higher than the entropy of the surroundings. However, the problem with this theory is the fact that black holes should have a temperature. If they contain entropy, like the second law of thermodynamics explains, than they should give off some amount of radiation. But, according to their definition, they cannot emit radiation.






The Origin And Fate Of The Universe

The general theory of relativity, developed by Einstein, implies that the universe was created during the big bang and that the universe would end if and when it collapses again or is pulled into a black hole. But the state of the universe during the early stages of its existence is generally unknown to us, and will most likely stay that way. The idea that the universe's existence was infinite, with no beginning or end did not sit well with many religious leaders. They argued that God created the universe, implying that there was an exact moment of creation. Quantum mechanics may unlock the history of the universe and it may be the key to predicting the fate of the universe. We know that the universe is constantly expanding. We also know that as it expands, the temperature of the matter in the universe decreases. This means that if the universe is expanding infinitely, it will eventually reach a point where particles of matter are moving infinitely slow.

Chapter 6: Black Holes

The term black hole was developed by John Wheeler in 1969. However, the idea of black holes started nearly 200 years ago. The theory about light that was favored by Newton was that light was made up of particles. The other theory about light implies that light is made of waves. Since these early times, we have concluded that both hypotheses are correct. Many people believed that gravity could not influence the speed of light. But gravity does play a key role in the speed of light. John Mitchell, who wrote the Philosophical Transactions of the Royal Society of London, said that light could not escape a large, compact star that had a strong gravitational field. Any light that escaped the star would be pulled back by the star's gravitational field. These absent-lighted stars are what we call black holes. We can not see them because they do not emit light, but you know they exist. We can learn more about black stars by observing the life cycles of a star. A star is born when hydrogen atoms as well as other atoms are drawn together by a gravitational field. The atoms heat up and continually collide with one another to form helium. The pressure increases to form a balance between the atom repulsion and the gravitational attraction. These two forces hold stars together. The star also releases hydrogen atoms, which makes them light up in the universe. These now stable stars will remain in tact for many years. The life time of a star depends solely on the quantity of energy used in the first stages of the star's life cycle. If the energy input is very high, the star will die sooner then it would have if it had used less energy to start with.



Black holes are formed when stars run out of hydrogen and begin to cool off. The balance between the repulsion of the atoms in the star and the gravitational field comes to an end. This caused the star to cave in, pulling particles close with its gravitational attraction. A once thriving star becomes a black hole that pull light and matter towards it. The fact that black holes do not emit light make them hard to detect with even our best technology. But was can predict that black holes exist by examining the movement of other objects in the universe. When stars are close enough to each other, the orbit abound each other, eventually colliding due to the gravitational attraction. But sometimes we can see stars orbiting around something that is invisible to our eyes. Although it could be a star that is too faint to see from here, it could also be a black hole. We can only assume that black holes exist due to the orbiting pattern of other stars as well as other celestial bodies. Many scientists believe that their could be a large black hole at the center of our galaxy. Such large black holes would need a lot of energy to exist, but it is not impossible. For now, we can only base our ideas of scientific observations and calculations.

Chapter 5: Elementary Particles and the Forces of Nature

Aristotle thought that matter was made up of earth, water, fire, and air. He believed that the force of gravity could act on the four "elements". He also believed that the other acting on the "elements" was levity and the ability to rise. He also believed that matter was made up of tinnier particles that could be broken down infinitely. He believed that there was no limit in the amount of matter that one could have. In fact, this belief of infinite division remained alive until John Dalton challenged the theory in 1803. He proposed that chemical compounds had set proportions of certain components. Even after his preposition, the main belief remained the Aristotle theory. When the existence of the atom became known in the early 20th century, scientists found that atoms were made up of the smallest particles known to mankind. At first, scientists believed that the nucleus of the atom was made up electrons and protons. In 1932, however, James Chadwick discovered that a particle called a neutron also existed in the nucleus. In fact, the true model of the atom was not known until much later. It was discovered that the nucleus consisted of the protons (positively charged particles) and neutrons (neutral particles) while negatively charged electrons orbit around the nucleus in an electron cloud.

Chapter 4: The Uncertainty Principle

Newton's theory of gravity caused Marquis de Laplace to believe that scientific laws could be made to predict everything that could happen in the universe. However, we are unable to calculate the randomness of the position of an object in space. The value of this theory can represented through the uncertainty principle. A man by the name of Max Planck proposed the idea that waves could only be emitted in specific packets, which he called quanta. The quantum hypothesis proposed by Planck also helped establish the uncertainty principle. A man named Werner Heisenburg represented the uncertainty of the position of an object multiplied by the uncertainty of that object velocity could not be smaller than the quantity known as Planck's constant. The value of Planck's constant is represented as 6.626 X 10^-34.

The uncertainty principle explains that you cannot know the exact position of a particle in the universe because the calculations are out of our reach. The observations of Planck's constant and the idea of random placements of particles in space led Heisenberg, Erwin Schrodinger, and Paul Dirac to propose the theory of quantum mechanics. Quantum mechanics and is based of the idea of the uncertainty principle. Quantum mechanics predicts the number of possible different positions that an object in space could be and calculates the most likely outcome. Although these quantities can not be used to predict the exact location of a particle in space, it narrows the locations down to a specific area.

Chapter 3: The Expanding Universe

A countless number of stars and satellites and even a few planets can be seen in sky at night. The planets will most likely be brighter and they will be the closet planets to Earth. Some planets that can been seen at certain times are Mars, Saturn, Jupiter and/or Venus. They appear to shift positions in the sky from time to time. However, we know that they stay stationary. An illusion is created when the Earth orbits the Sun. It seems like the stars are moving, but, we are the ones moving. We cannot feel the  Earth move while we are on the ground, but it does move. We can use this movement to determine the distance between stars and the Earth. The closer the stars are to Earth, the more they seem to move or shift positions. It would take us four years to reach the closest star, Proxima Centauri, which is 23 million miles away. Our star (the sun) is only 8 light- minutes away from Earth! The brightness of the star depends on its luminosity (light it radiates) and its distance from the earth. 

http://www.youtube.com/watch?v=1S_1YfjMRvY

The existence of the Milky Way galaxy has been acknowledged since 1750. The existence of other galaxies was not known until 1924, when Edwin Hubble proposed the theory. Hubble said that if stars in another galaxy were close enough to be measured, we would be able to calculate the distance between that galaxy and ours. Different types of stars can be distinguished by observing the color light they give off. It is hard to determine this difference with the naked eye, so telescopes are used to determine the spectrum of the light from the star. Different types of stars have different visible spectra. Certain colors are absent from the star's spectrum, and different stars have different colors missing.

Chapter 2: Space and Time

Before Galileo, many people thought that scientific laws could be based on thought rather than scientific observations. Galileo did an experiment to determine if the weight of an object could affect the speed at which it fell from a fixed height.  He rolled two balls with different weights down a slope. He found that both balls increased their speed at the same rate. This proved that the same amount of force acts on objects with different weights and disproved Aristotle's idea about motion. Newton based his laws of motion on Galileo's measurements. This also showed that force changes the speed of an object rather than causing it to move from a stationary position.



Newton's First Law of Motion: An object in motion will keep moving in a straight line at a constant speed until an outside force acts upon it.
Newton's Second Law of Motion: The body will accelerate (change speed) at a rate equal to the force.
Newton's Law of Universal Gravitation: Every object attracts every other object with a force equal to the mass of each object.
Newton's Law of Gravity: Objects closer to each other will have more force than objects that are farther apart. This laws explains the gravitational attraction of stars and predicts the orbitals of celestial bodies.