Reddit mentions of General Relativity from A to B

I wouldn't call it subjective. But time is indeed always relative. This is what Einstein's theory was all about-- Newtonian physics always operated on the notion of absolute time, which was the same everywhere, always. That is now an old fashioned view that no one subscribes to anymore.

I think you would get a lot out of this book. It explains all of these concepts from the ground up in an amazingly intuitive way. It contains almost no equations whatsoever, and explains everything via diagrams. It's excellent, and will flesh out the picture of the relativistic nature of time, starting from the "common sense" Newtonian take, then building special, then general, relativity.

Ah yes, the extended essay, I remember an IB friend of mine telling me about his one time.

So, when it comes to realistic time travel you're limited to a few options, and with everything you read you have to keep in mind that there is scientific consensus on the issue, and the consensus is that time travel isn't possible. There aren't really multiple scientific theories on the issue, though you will be able to find science fiction accounts of the different 'models' of time travel.

If you want a serious essay about why that is you're going to need to learn a bit about relativity. There a book that I always liked by Geroch called General Relativity from A to B which is not a textbook, in that it doesn't really contain any math, but it's not a popular science book either. It might be worth a read to give you some insight into what exactly the question you're asking means, and how understanding a bit about relativity answers it.

The wikipedia page introducing special relativity is pretty good, and should give you enough information to understand this little argument which talks about the relationship between causality, time travel and going faster than the speed of light.

You'll find in your reading that gravity and geometry are linked. And Einstein wrote down some equations which, if you solve them, tell you the geometry you get for some mass and energy distributions. Some mass and energy distributions give you really weird geometries which someone might say admit time travel. These solutions are, in the scientific community, discarded as 'unphysical'. The most famous of them is the Godel Spacetime (fair warning, that's a really technical link). Another solution of Einstein's equation is a geometry known as the Alcubierre metric which pulls space towards it in front of it, and pushes it out from behind to effectively travel faster than light, which one could call time travel (possibly). But to do so you need a large amount of negative energy, which is not something we believe to exist. Though, there's a guy at Nasa who works on it.

I think Geroch's book could serve you well, or at least help you refine your essay question into something you can talk about reasonably precisely, the other links should give you a bit of idea about what's out there in terms of actual time travel, but the consensus is that it isn't possible. As far as theories go, there's one theory, which is General Relativity, and all time travel ideas have to somehow fit inside it.

If you want to talk more about any of it, or want a hand with math/concepts behind relativity just ask. There are relativity questions here all the time, so I'm sure people would be interested in talking about it.

i recommend the following books, all of which give excellent treatment to spacetime and spacetime diagrams:

• general relativity from a to b by robert geroch
  
  
• flat and curved space-times by george ellis and ruth williams
  
  
• space and time in special relativity by david mermin
  
  
• spacetime physics by john wheeler and edwin taylor

I've heard very good things about [General Relativity from A to B]
(https://www.amazon.com/General-Relativity-B-Robert-Geroch/dp/0226288641/ref=sr_1_1?ie=UTF8&qid=1499632748&sr=8-1&keywords=general+relativity+from+A+to+B) by Robert Geroch, but haven't read it myself.

If you had gone over the site, you would have noticed that I address your objection, which is a silly one. If you think you can use proper time tau to parametrize time t as a way of showing that t is a variable, I've got a bridge to sell you. Time is time. What's good for the gander is good for the goose. If you think that you can use tau to show that t is a variable, you must first show that tau can change. You would need a meta-tau for your tau, and a meta-meta-tau and so on, ad infinitum.

Not all relativists are as dumb as you though. Here is a quote from "Relativity from A to B" by Prof Geroch at the U. of Chicago.

>"There is no dynamics within space-time itself: nothing ever moves therein; nothing happens; nothing changes. [...] In particular, one does not think of particles as "moving through" space-time, or as "following along" their world-lines. Rather, particles are just "in" space-time, once and for all, and the world-line represents, all at once the complete life history of the particle.

From Relativity from A to B by Dr. Robert Geroch, U. of Chicago

If that does not shut you people up, nothing else will. I tried. Besides, your intelligence compared to someone like Karl Popper is obviously miniscule. He was smart enough to understand that time cannot change by definition. You're just a pompous ass. Those who are voting you up are ass kissers. Now vote this down, AKs. LOL.