Reddit reviews Relativity: The Special and the General Theory

Please everyone, read this book.
It is written conversationally and with very simple mathematics, but is extremely thorough in explaining most of the WTF?! bits of relativity.

Also Einstein had a great sense of humor.

Feynman's QED

Asimov's non-fiction is good

Godel, Escher, Bach

Einstein's original book

Maxwell's book (lots of math)

When you say "clock in motion", you really mean in motion relative to an observer. The distinction is important, as it is the reason you can observe the time dilation phenomenon.


Example: I have a clock, and you have a clock, which are synchronized to begin with. You and your clock board a spaceship which after a relatively brief period of acceleration (this is to simplify the math), is traveling at 0.5c (that's 0.5 times light speed) relative to me. Now lets say that your spaceship passes by me, and I have a way to compare the ticks of your clock with those of mine. I will observe that your clock is ticking slow. However, you on your spaceship, at rest relative to your clock, will observe that my clock is ticking slow.


So which of us is right? Actually, we both are. By using the Lorentz transformation, we can convert our times to agree with each other. What it really means is that time can only be measured relative to frames of observation. There is no universal flow of time. Time and space are linked.



This is just one part of special relativity, and if you are interested in learning about it, I recommend Einstein's Relativity. It is written for the non-scientist and can be clearly understood, albeit with some difficulty and patience. If you really want to understand it, take a class.

Edit: spelling and grammar

This is a nice one for visualization:

http://www.pitt.edu/~jdnorton/teaching/HPS_0410/chapters_2015_Jan_1/Special_relativity_rel_sim/index.html

Going deeper than that, I'd just look for a cheap textbook on relativity that mentions simultaneity in the table of contents, or read Einstein's math-free book on relativity:

http://www.amazon.com/Relativity-The-Special-General-Theory/dp/0517884410

(One reviewer there is saying that that version is missing the crucial images, so make sure you find one that has them.)

One thing I suspect you're getting hung up on is that this ought to make time travel a possibility. It doesn't.

Essentially, events can be separated in two ways: timelike and spacelike. So you should think in those terms instead of simultaneous or not simultaneous.

If events are spacelike separated, then they can be seen as either occurring simultaneously, A before B, or B before A.

If events are timelike separated, then event A precedes event B, always.

The difference between the two types of events is simple. If light has enough time to make it from one event to the other, they are timelike separated.

If light doesn't have enough time to make it between the two events, they are spacelike separated.

This is actually why faster than light drives ALWAYS implies the possibility of time travel, no matter what hand-waving warp drive, hyper drive, or what ever a sci-fi author tries to introduce. If you can travel between two spacelike separated events, you can travel backward in time. They are identical.

Put another way, with spacelike separated events, you can ALWAYS find a reference frame where the events occurred simultaneously, but you can NEVER find a reference frame where the events occur at the same place.

With timelike separated events, you can ALWAYS find a reference frame where the events occured in the same place, but NEVER a reference frame where they occurred at the same time.

I can't believe no one has mentioned Einstein's book, Relativity: The Special and the General Theory. Actually, people may have not mentioned it because it could be a little light for a math major, but if you "prefer to not work to hard in [your] casual readings" then it could be perfect for you. Einstein kind of glosses over the difficult math, but if you know that stuff already then this book will give you a great intuitive understanding of relativity.

http://www.amazon.com/Relativity-The-Special-General-Theory/dp/0517884410

Why not start with Einstein's own book on the subject? Less than $10. Amazon link.