Saturday, November 20, 2010
Chapter Five: Elementary Particles and Forces of Nature
Sunday, October 17, 2010
What is Quantum Mechanics?
Newton’s success with gravity and other theories let the Frenchman, Marquis de Laplace around the early 19th century to argue that the universe was made in a way such that if we knew the position and velocity of every object at one time then we could predict the future. It is understandable in the case of predicting a planet’s rotation, but predicting human behavior, that’s hard to believe. In early 20th century, two British scientists, Sir James Jeans and Lord Rayleigh said that a hot body must radiate infinite amount of energy. To avoid this ridiculous result, German scientist Max Planck suggested in 1900 that waves were emitted in packets called quanta and making each quanta required a certain amount of energy that is higher than the frequency of the wave making the energy emitted being finite. This suggestion lead to a bigger discovery. In case you forgot, light is a wave. This suggestion about quantum made a German scientist, Werner Heisenberg to say that the longer the wavelength of an object, the easier it is to tell it’s velocity and harder to tell the position and vice-versa with a high wavelength. Because of this, Laplace’s argument might be true, but will never be used since it impossible to tell and objects’ position and velocity at the same time. This became known as the Uncertainty Principle. If you multiply the uncertainty in the position of a particle times the uncertainty of the velocity of the particle multiplied by the mass of the particle your product will always be less than a certain amount known as the Plank’s constant.
Because of the Uncertainty Principle, a new theory called Quantum Mechanics, led by Werner Heisenberg, Erwin Schrödinger, and Paul Dirac, sprang up in the 1920’s. This theory stated that objects did not have specific positions and velocity but rather a quantum state, in which they had a combination of both. In general, Quantum Mechanics didn’t predict a single observation rather the probability of that observation. This received a lot of criticism, especially from Einstein but most scientists agreed with it. Quantum Mechanics tells that things can’t be particles or waves, but it is the observation that is a particle or wave. A result of this idea is that when two wave crests and two wave troughs occur at the same time, the wave is reinforced and in phase. If the crests happen at the same time as a trough then both waves cancel each other out and the wave is out of phase.
Before Quantum Mechanics is that the electrons should lose energy and spiral into the nucleus. That means all matter should collapse into a very high density. That can’t be true because it has not happened to all matter! A partial solution was discovered by Danish scientist Niels Bohr in 1913. He said that electrons could only orbit from certain distances form the nucleus. The problem with this is that it was seemed very reasonless. This was fixed in Quantum Mechanics because it said that the electron would travel like a wave.
Quantum Mechanics has helped in technology, creating circuits, building computers and televisions, chemistry, and even biology. General Relativity and Quantum Mechanics have not fully been combined, but will have to work together with other forces of nature to create a single unified theory of the universe.
Saturday, October 9, 2010
Chapter Three: The Expanding Universe from A Brief History of Time
If the universe was expanding, shouldn't it eventually collapse? General Relativity Theory supported that the universe must be in motion. Einstien, who liked a static universe, introduced an " antigravity force" that keeps the universe in balance. The only person willing to take Hubble seriously was Alexander Friedmann. Friedmann made two assumptions about the universe: It looks approximatly identical in whichever direction you look and that this would be true wherever you were. In 1965, two American physisist, Arno Penzias and Robert Wilson, were working with a sensitive microwave detector. The detector detected an almost equal amount of microwave energy outside the atmosphere. They had accidently proved the first of Friedmann's assumptions! As for the second assumption, there has been nothing to prove or disprove it. Friedmann, seeing that the galaxies are moving apart theorized that they must have been at the same place, long ago. This led to the first Friedmann model of the universe, saying that the world began with the Big Bang and will begin to expand, and eventually contract into the Big Crunch. They're actually two other models, one stating the universe will expand forever and the other saying the universe expansion force will eventually become smaller and smaller but never quite reach zero. No one knows which model represents our universe.
Saturday, October 2, 2010
Chapter Two: Space and Time
10.02.10
Saturday, September 25, 2010
Our Understanding of the Universe
From now on, every week, I'm going to post a summary for each chapter of the book A Brief History of Time by Steven Hawking. The book explains the universe for those of you who don't understand it. Some topics include black holes, the hunt for the grand unification theory, the arrow of time, the expansion of the universe, quantum mechanics, the beginning and the end of the universe, the uncertainty principle, the forces, and, in the newest edition, wormholes and time travel. You can buy the book here.
Best Books
- A Brief History of Time
- The Red Pyramid
- The Ranger's Apprentice series