| MadSci Network: Physics |
Kuhanesan
There are in fact two theories of Relativity. The special theory of Relativity is a simple theory that explains how different observers see things in the Universe. The general theory deals more with 'what is space' and 'how do mass and gravity affect things' as well. If you want a full description of the concepts and findings of relativity I would read some books first. It takes a lot of information to explain these theories without using any maths.
The above may not sound like much but Relativity has shown that the Universe is a strange place indeed. For one thing time slows down the faster you go. For example, ocean going vessels now rely on Global Positioning Satellites to tell them where they are. These satellites have to have their clocks Relativistically corrected in order to provide accurate postioning data for ships. Gravity slows time down as well. Gravity is caused by a mass `bending' space. The General Theory of Relativity also provides some maths that help us explain how the Universe was created, why it looks the way it does and how it will end. This, more so than anything, is why people are interested in Relativity. The one question everyone asks at some point is `where did we come from, how was the Universe made'. Normally religions have had the monopoly on answering this. General Relativity provides a much more tangible set of answers. In this century we have been able to actually describe and measure real things about the Universe and see if it matches predictions. By real things I mean the speed remote objects are moving at, the ratio of Hydrogen to Helium in the Universe, the density of space and so on. Previously the answers would simply be "because God made it this way". Now we can see why God made it that way.
Though Relativity has possibly never saved one persons life it achieves another function. It helps us understand the real world, why it is the way it is and the ultimate fate of the Universe.
If you wish to know more there are many online sources about Relativity. Try searching for "General Relativity", "Special Relativity", "Big Bang Cosmology", "Einstein" and so on. I have also just answered another question describing some basics of Relativity in some detail, look for question number 856498350.Ph on MadSci Network. Also, a lot of books have been written about it.