In fact, if the laboratory in the train or rocket issoundproof and has no windows, there is no experiment a person could conductthat would show he/she is moving. Two people, one in astationary laboratory and another in a laboratory aboard a train or rocketmoving in a straight line at uniform speed, should get the same results in anyexperiment they conduct.
In his SpecialRelativity theory, Einstein assumedthat the fundamental laws ofphysics do not depend on your location or motion. Time is not completely separate from and independent of space as you would ordinarily assume. It takes around 1.3 seconds for light to go from the moon to the Earth.Einstein's Relativity Spacetime Chapter index in this window Chapterindex in separate window This material (including images) is copyrighted!.See my copyright notice for fair use practices. It takes around 8 minutes for light to get from the Sun to the Earth.
The Sun is almost 93 million miles from the Earth. To give you an idea as to how fast light is, we'll give you some examples. In a vacuum, where there is nothing to slow it down, light travels 186,282 miles per second! Wow, that's fast! When light travels through matter, like air or water, it slows down some, but it's still pretty fast. Nothing moves faster than (or even close to) the speed of light. Light moves at the fastest known speed in the universe. Sunlight is a source of energy as well as a source of vitamin D for humans. It also is a major component in photosynthesis which is how most of the plant life on Earth grows and gets nutrients. Sunlight keeps the Earth warm, so it's not just a frozen ball in outer space. Sunlight does more than just help us see (which is pretty great, too). Without sunlight our world would be a dead dark place. These objects are called translucent objects. A third type of object does some of both and tends to scatter the light. Other objects completely reflect light, like an animal or a book. This type of matter is called transparent. Sometimes light will pass directly through the matter, like with air or water. Why does light go through some things and not others?ĭepending on the type of matter it comes into contact with, light will behave differently. Light is unique in that it behaves like both a particle and a wave. Today scientists say light is a form of energy made of photons. So does it even exist? Of course it does! We couldn't live without light. Light has no mass and is not really considered matter.
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