...I have a fascination with trying to grasp Einstein's theories of "special" and "general" relativity. I just think their so neat. Even though I had heard of them before it wasn't until one day several years ago that I took my class to the library because the librarian (or Media Specialist as they are called now) was going to do a lesson with them, that I found myself with some extra time. So I found a book about his theories. I had heard of them, but didn't really know what they meant. So I went through that whole book. I couldn't put it down. It was so interesting.
So anyway, I actually got to read some of his original paper published in 1920. Its too much for me to understand the details, but I get the overall ideas. Here is a good simple summary. There is a fun question thing at the end.
This very well may be one of those posts that no one reads. But it had been awhile since I posted and this is what I was thinking about today, so here it is anyway.
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Brilliantly simple
Einstein's theory put world in a different light
Richard Halicks - Staff
Sunday, September 25, 2005
One hundred years ago on Tuesday, a 26-year-old patent clerk in Switzerland published a short paper in Annalen der Physik. In it, Albert Einstein introduced what would become the most famous equation in history. His breakthrough on "special relativity" does not explain why your relatives' three-day visit turns into three months. The theory, after all, has its limitations. Among them is that, 100 years later, most of us don't understand it. So read on, and see whether this helps.
Einstein saw the light.
And the light changed everything.
One of the things Einstein postulated is that light travels at the same speed for any observer, regardless of how fast or slow that observer may be moving.
This seems to contradict what we see around us. Speed depends on your frame of reference. If you're standing alongside the road and I drive past at 70 mph, then in your frame of reference I'm going 70. But inside my car, my steering wheel does not appear to me to be going 70 mph. It appears not to be moving at all because it is traveling the same speed and in the same direction that I am. Likewise, if another car passes me going 75, then in my frame of reference it's going 5 mph.
Light doesn't work that way. The observer's frame of reference does not affect it. Nor does the speed of the light's source. For example, light coming from a starship traveling at 100,000 mph will move at the same speed as if the starship were hanging motionless in space.
Einstein also showed that the speed of light, about 186,000 miles per second, is the universe's speed limit. An object may approach that speed, but nothing may exceed that speed.
These deductions had an interesting impact on our concept of time. In a sense, Einstein stopped the clock, or at least slowed it down. Galileo, Isaac Newton and others suspected that there was a universal clock ou there somewhere, keeping perfect time, precisely measuring all of our moments. But Einstein showed that time is not absolute at all, that it moves more slowly as velocity increases.
David Finkelstein, emeritus professor of physics at Georgia Tech, explains it this way. Say you and I synchronize our clocks. Then you take a fast plane around the world, and I stay put. "Of course our clocks will still agree the next time we meet," Finkelstein says. "Time is time. It waits for no man."
Then he takes it all back. "But it turns out that it waits a little bit! Experimentally, this has been shown. If you carry a sufficiently precise clock around the world in a commercial airliner, you'll see it differs from a clock left at home by some fraction of a microsecond. So you don't see it ordinarily, but if you look hard you can see it."
That's another thing about Einstein's theory. You don't start to notice special relativity until things are moving really fast. It isn't something we see in our slow everyday lives.
Einstein, of course, did not seem to dwell in the same world as most of us but in that realm of vast distances and great speeds that we can scarecely comprehend. And because of him, we see our world differently.
Note: Special relativity is not to be confused with Einstein's theory of general relativity, which came years later and is said to be his greatest accomplishment. But that's another anniversary at another point in space and time.
Test your knowledge of relativity
1. Relative to the Earth, you are standing still. Relative to the sun, you are traveling 67,000 miles per hour, which is the speed at which Earth travels around the sun. So motion depends on your frame of reference. In one frame of reference --- Earth's --- you are stationary; in another --- the sun's --- you are moving at high speed.
. . True . . . False
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2. The speed of light is the same for every observer everywhere, regardless of his or her frame of reference.
. . True . . . False
---
3. If you are riding a bicycle with a headlight at night, the speed of light coming from your headlight increases with the speed of the bicycle.
. . True . . . False
---
4. Einstein's remark that "imagination is more important than knowledge" is an accurate statement.
. . True . . . False
---
5. Nothing in the universe can travel faster than the speed of light.
. . True . . . False
---
6. Bill and John are 20 years old. Bill watches John leave Earth in a rocket traveling near the speed of light. On Earth 20 years later Bill sees John's rocket return. Bill is now 40. But John is still 20. This is possible, provided John's spaceship travels at a high enough speed.
. . True . . . False
---
7. If the speed of light is constant, then the flow of time is also constant. That is, the passage of time is absolute and unchanging regardless of motion.
. . True . . . False
---
8. One net effect of E=mc2 is this: a very small amount of mass can produce an enormous amount of energy.
. . True . . . False
---
9. Mass and energy are different quantities in physics.
. . True . . . False
---
10. In 1895, Einstein failed the liberal arts section of an entrance exam at a school in Zurich, Switzerland.
. . True . . . False
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ANSWERS AND SCORING
1. True: in spite of your suspicions, this is not a trick question.
2. True: This is a trick question. It was also one of Einstein's great breakthroughs.
3. False: You weren't paying attention on No. 2!
4. True, especially if you are Einstein or the secretary of defense.
5. True: An object gains mass as it gains velocity. The greater its mass, the more energy required to make it go still faster. So an infinite amount of energy would be required to make the object go as fast as light.
6. True: see No. 7
7. False: If the speed of light never changes, then something else has to. That something else is time. Isaac Newton believed there was a great universal clock somewhere that always kept perfect time. But Einstein showed that Newton was mistaken. Time is relative to motion. That is why time passes more slowly for an object that is gaining in velocity. For example, scientists once set two very precise timepieces to exactly the same time. Then they flew one around the world on a plane, while the other stayed in the same place on the ground. When the plane finished its revolution of the earth, less time had passed on the airborne clock than had passed on the stationary one. And that's why, in question No. 6, John is so much younger than Bill. Twenty years passed for Bill on Earth, but on that speeding space ship, just a few moments passed for John. Stephen Hawking once wrote in Time magazine that you could add time to your life by continually flying east in an airliner. "But," he said, "the tiny fraction of a second you gained would be more than offset by airline food."
8. True: This consequence of E=mc2 accounts for why nuclear weapons are so destructive. When the nucleus of an atom is split into two pieces with slightly less mass than the whole, a tremendous amount of energy is unleashed.
9. False: E=mc2 showed that mass and energy are equivalent. "It followed from the special theory of relativity that mass and energy are but different manifestations of the same thing," said Einstein, "a somewhat unfamiliar conception for the average mind. "
10. True: Nobody's perfect.
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SCORING
Ten right: 100 percent! You're relatively brilliant.
Eight or nine right: You're way smarter than you've been letting on.
Six or seven right: Are you in your third or fourth year at Georgia Tech?
Four or five right: You may qualify for the HOPE scholarship.
Three right: You have the hair of Einstein, but not the brain.
Two right: Relative to you, everything's moving really fast.
One or none right: You could run FEMA.
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Sources: American Museum of Natural History Museum, "Nova," BBC, Manhattan Project Heritage Preservation Association, Time magazine
Find this article at:
http://www.ajc.com/sunday/content/epaper/editions/sunday/issue_3463337f90c8e1df0060.html
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