# Space-time and matter

1. Jun 20, 2014

### Yoozer

Hello experts,

Could someone suggest some materials that would explain to me the current state of knowledge about how space and time are two aspects of the same thing, but matter is not?

I've seen and read many popular explanations of how space-time was unified by Einstein's theories of relativity, but I am curious about how matter stands apart from spacetime and has not been unified into something like, say, matter-space-time.

I'm not raising this question as an alternative theory (which I know is now allowed on these forums) but rather looking for references to explanations of why matter has not (or cannot?) be combined with space-time into some unified theory of existence (for lack of a better term).

Thanks for any help.

- Yoozer

2. Jun 20, 2014

### ModusPwnd

Special relativity does not require very sophisticated mathematics... But you do need to be very confident with your algebra, vectors and perhaps even a bit of calculus.

Note that you are talking about "matter" which is not well defined in physics and probably a word best not used. Generally its a colloquial, non-technical term. You might be better off to consider "mass" which is a technical and well defined term. In special relativity mass is a kind of combination of momentum and energy similar to how space is combined with time to form space-time. Both space-time and momentum-energy are what is known as "four-vectors", four dimensional vectors that behave (or transform) a certain way. You can see that if you are not confident with the algebraic concept of vectors this may not make much sense at all...

When I was an undergrad in physics we had this book for special relativity;
https://www.amazon.com/Special-Relativity-M-I-T-Introductory-Physics/dp/0393097935

Otherwise, for a more accessible reference consider "hyper physics";
http://hyperphysics.phy-astr.gsu.edu/hbase/hframe.html

Last edited by a moderator: May 6, 2017
3. Jun 23, 2014

### Simon Bridge

mass and energy are unified, space and time are unified, energy has a close relationship with space but they are different thingies.

unifying mass/energy and space/time would involve figuring out how to look at one so that it looks like the other - i.e. can we turn one into the other? So far nobody knows how that could happen.

meanwhile we can exchange time and space, and we can exchange energy and matter.