In a few weeks we'll be at the centennial of the publication of Einstein's paper on general relativity. Special relativity came out about a decade earlier nailing down what is relative and what is absolute about time, space and motion. It is beautifully elegant and even simple. The only math is high school level geometry and with a bit of dedication and logic a high school student can understand the basics.
General relativity is a different beast. Mathematically complex - Einstein needed serious help with the math - it is traditionally first introduced as a junior or senior level course for physics majors with a much deeper dive in grad school. But it is both beautiful and important, so the challenge is to describe the basics accurate enough. Randall Munroe of xkcd fame has a nice little introduction in November 18 issue of The New Yorker - The Space Doctor's Big Idea. He restricts himself to a vocabulary of the 1,000 most commonly used words in American English - a feat in it's own right. read it!
Einstein said he only had a few original thoughts - 'the happiest thought of my life' came to him in 1907 when he was working at the patent office in Bern.
If a person falls freely he will not feel his own weight.
Most people wouldn't go much further, but Einstein saw that an accelerating reference frame was equivalent to a gravitational field. From there things quickly into some difficult math, but Randall paints some of the results. My approach usually begins with:
down is the direction in which time runs more slowly...
In any event there will be several explanation in the popular press in the next month. If you haven't been exposed give them a read - start with Randall's. You can get a rough overview - good enough to follow some fascinating astrophysics a bit better. And here you have a leg up on Einstein. In his day it was felt the effects of general relativity would be very difficult to detect. It was all about getting closer to Nature. Now we have that, but also a powerful tool to probe a Universe much more exotic than the human imagination could conjure up by itself. It sometimes holds that the equations of Nature seem to know much more than the people who discover them.
If you've had an introductory physics class in college you might enjoy taking a look at Relativity : the Special and General Theory by Albert Einstein from 1916. He was a good writer and the translation is good. Many of the explanations by others follow it's form.
nope, nothing from me. 'too close to Thanksgiving.