-
-
---------------------- 2302 - Einstein’s Relativity
-
- When Isaac Newton defined the laws of motion in 1687 he defined velocity as the rate of change of space with respect to time. Back then, space and time were absolutes. They were standard measurements that everyone saw as the same. A meter was a meter and a second was a second. They were the same for everyone.
-
- At that time mass, or matter, and energy were totally different things. In 1905 Einstein changed this world of physics and astronomy using one very, very simple idea, the laws of nature are the same for all observers regardless of their position or their relative motion.
-
- That simple theory changed everything. First, in order to keep the laws of nature the same for all observers the speed of light had to be constant, 186,000 miles per second, and space and time had to be the terms that were relative.
-
- As matter approaches the speed of light lengths got shorter (space shrinks), time slowed down, and mass increased. At those speeds matter formed into a pancake with near infinite mass. It would take infinite energy to accelerate it further. That was impossible.
-
- Therefore, no object with mass could travel at the speed of light. Photons which do travel at that speed had to be massless.
-
- Second, mass and energy became two forms of the same thing with E = mc^2. A large amount of energy could create a small amount of mass, and, a small amount on mass could create a large amount of energy.
-
------------------------ E = c^2 * m
-
----------------------- Energy = 90,000,000,000,000,000 times mass.
-
---------------------- Energy in kilograms*meter^2/sec^2 = 9*10^16 meters^2 / sec^2 * kilograms.
-
- With relativity simultaneous events between two observers cannot occur. Technically, two observers can not exactly synchronize their watches. If both observers are at rest an event can appear the same to both.
-
- However, if one observer is in relative motion then one event will appear differently to the two observers. That is because it takes a finite time for light to reach the eyes of an observer. If two observers are at rest observing each others clocks, the time delay for light to reach their eyes is the same. So, they see each other’s clocks the same.
-
- However, if one observer is in motion relative to the other observer at rest the observer in motion will see a delay for the light to reach his eyes and the other clock will appear to slow down, more time duration between ticks.
-
- Third, an observer in motion cannot tell the difference between the force of acceleration and the force of gravity at rest. A force of acceleration is required to change a mass that has constant motion in a straight line. That is the definition of a force, F = ma.
-
- Gravity around a mass then becomes a curvature, or a warping of space-time so objects feel the force of attraction but to them they are going in a straight line.
-
- Einstein started thinking of this when he was 16 years old and he published his special theory of relativity when he was 26. The first theory was “special” because it applied only to relative observers in constant motion in a straight line.
-
- He worked 10 more years to publish his “general” theory of relativity that applied to observers under acceleration, not moving in straight lines. He was not experimenting in the lab. He was not reading books. He was just thinking. He was doing experiments in his head.
-
- Einstein thought he was traveling on the head of a light beam. He holds a mirror out in front of himself. As he approaches the speed of light does the image in the mirror disappear? Can he possible see his own reflection in the mirror?
-
- According to Galileo without an external reference no one could tell if they were moving at a constant speed in a straight line. Einstein was moving at a constant speed in a straight line on the light beam. So, he could not tell the difference if he was standing still. So, if Galileo is right he should be able to still see his reflection in the mirror.
-
- Galileo did his thought experiment as though he was in the hull of a ship with no port holes. How could he tell if the ship was moving? He concluded that he could not. All motion was relative. As long as you were traveling at a constant speed in calm water, in a straight line all the laws of nature remain the same and you could not tell if you were moving.
-
- Einstein did the same thought experiment only he was on a space ship that could travel the speed of light. What would happen if you were traveling at that speed and you turned a flashlight on straight ahead? Would the light from the flashlight be traveling twice the speed? Einstein concluded that the speed of light remained the same and that all the laws of nature remained the same to all observers regardless of their relative motions.
-
- Once he concluded this there were consequences. For this to be true then two observers in relative motion could not possible see the same event in the same way. For the other observer time must slow down, lengths must shorten, and mass must increase. All of these are natural consequences of keeping the speed of light constant for all observers.
-
- There is another consequence when you consider not just constant motion but acceleration. In another thought experiment Einstein concluded that an observer could not tell the difference between the force of acceleration and the force of gravity.
-
- A force is defined as a push that causes a mass to accelerate. Acceleration is the rate of change of velocity with time. Therefore, acceleration is the rate of change of the rate of change of space with time. If you can’t tell the difference then gravity is the same thing. Since space and time are flexible gravity must be the result of a curvature of space-time.
-
- Einstein was thinking in 4 dimensions. That thought will warp your mind. In 2 dimensions space time can be thought of as a trampoline. Gravity is caused by mass. Mass would be like a bowling ball in the center of the trampoline causing it to stretch into a giant dimple in the center.
-
- The Sun would be like the bowling ball and the Earth would be like a tennis ball rolling around in a circle inside the funnel. The Moon would be like a marble rolling around the tennis ball dimple.
-
- Each orbit feels to the observer as though they are traveling in a straight line at a constant speed. Therefore, they can feel no motion. We are in orbit traveling in a circle around the Sun at 100,000 miles per hour but we can not feel it.
-
- Earth’s orbit is a straight line in space time. It is like a geodesic circle on Earth, the surface of a sphere. The shortest distance from San Francisco to Paris is over the Artic Circle. A geodesic is a Great Circle that has its radius at the center of the Earth. The arc of a Great Circle traces out the shortest distance on the surface of a sphere. The shortest distance between two points is a straight line, but on the surface of a sphere it is the arc of a Great Circle.
-
- Einstein visualized space-time as a curvature like the surface of a sphere. Mass causes space and time to bend , And, mass is the same as energy. Mass is just energy that has slowed down enough that we can see it.
-
- The Universe started out as a bundle of energy that started expanding creating space and time as it expanded. Before then there was no space and no time. But, what is the Universe expanding into? It is expanding into no space and no time. It is expanding into a Black Hole where nothing can escape. It is expanding into another singularity where space and time need to be created all over again. I know, it does warp the mind.
-
- To really bend the mind think of the fact that all the laws of nature are so finely tuned for us observers that if any one law, or natural constant, changed by the slightest amount life as we know it could not exist. We are observers with a defined environment finely tuned for our existence.
-
- Einstein said, “ The most incomprehensible thing about our Universe is that we are here trying to comprehend it”
-
- March 10, 2019 766
----------------------------------------------------------------------------------------
--- Some reviews are at: -------------- http://jdetrick.blogspot.com -----
-- email feedback, corrections, request for copies or Index of all reviews
- to: ------- jamesdetrick@comcast.net ------ “Jim Detrick” -----------
- https://plus.google.com/u/0/ -- www.facebook.com -- www.twitter.com
-------------------------- Sunday, March 10, 2019 --------------------------
------------------------------------------------------------------------------------------
No comments:
Post a Comment