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What
Albert Einstein Thought
No one changed the fundamental landscape of physics more
than Albert Einstein. Before Einstein, space and time were fixed, and separate.
Einstein showed they were elastic, and intertwined. Before Einstein, solid
matter was different from insubstantial energy. But Einstein showed they were
the same, and matter could melt into energy, according to E=mc2. Before
Einstein, gravity was considered a force, like electricity. He showed it was the
warping of space-time into an unseen fourth dimension. Here are four key theories he developed: * 1905: Photoelectric Effect. Einstein showed that light
has concrete, particle-like properties in addition to its well-known wavelike
nature. Among other things, this discovery led to the invention of nifty devices
such as photoelectric detectors that keep the closing elevator door from
squashing you into spaghetti. It was for his work on the photoelectric effect
that Einstein received the Nobel Prize in 1922. * 1905: Brownian Motion. Before Einstein, the idea that
matter was made of molecules was generally accepted, but far from proven.
Molecules themselves weren't visible. But Einstein calculated that molecules
moving around in a liquid would cause little grains sitting on the surface to
dance around in a jittery way. His calculations accurately described the erratic
behavior of pollen grains on water previously noticed by botanist Robert Brown.
Hence, Einstein offered the first convincing proof that molecules were real. * 1905: Special Theory of Relativity. Einstein came to the
startling conclusion that the speed of light is always constant, no matter
whether you're moving toward the light, or running away from it. That meant that
space and time were elastic; that is, the space and time you perceive depend on
your point of view. If you're moving almost as fast as light (imagine running
alongside a light beam, as Einstein did), then the light won't appear to go any
slower. However, your space will contract, and time will slow down. What's more,
he showed that traveling fast also increases your mass. As you travel close to
light speed, you get infinitely massive. Since nothing can be infinitely
massive, nothing can travel as fast as light. One consequence is that energy can
turn into mass, and vice versa. Among other things, this theory explained how
the sun shines (by converting mass into energy, through nuclear fusion). Alas,
it also led to the development of the atom bomb. * 1916: General Theory of Relativity. This was an extension of the "special" theory because it brought gravity into the fold. That is, it showed "gravity" is also relative. If you are falling off the side of a building, you don't feel any gravity, because you are moving along with the gravitational field. (That's why astronauts feel weightless; they are still affected by gravity, but they are moving along with it, so it seems to disappear.) Einstein called this insight the "happiest moment of his life." It led him to the realization that gravity is not actually a "force," but rather, the effect of the curvature of space-time caused by massive objects. Imagine the sun sitting in space like a bowling ball sitting on a water bed. The sun warps space-time the same way the bowling ball warps the mattress. If you happen to be a marble rolling around near the bowling ball, you'll fall into the "gravity well" created by the bowling ball. The Earth "falls" toward the sun for the same reason. |
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Copyright © 2010
Tim Stouse
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K.C. COLE, LA Times Science Writer