# I want to understand time.

1. Sep 7, 2013

### dingdongsilve

I would like to have a better understanding of time. I have to start at an extremely basic level, however, due to my lack of intelligence. It was suggested to me that I start with Pre-Algebra. Can someone give me a link to a free resource or a book with which I may learn what is needed to progress to the next suggested topic, Algebra I. Thank you very much for your help.

Note: It isn't necessary to read this part but I felt I should clarify something. I know that there are many resources to learn something such a Pre-Algebra. There are so many, in fact, that I became overwhelmed trying to decide which source has the best explainations and completeness of material. That is why I am asking for a recommendation, so that I may feel comfortable with the completeness of the material. Also, I understand that saying "I want to understand time." is very vague but, due to my current knowledge of physics, it is the best way for me to describe what I am trying to accomplish.

2. Sep 7, 2013

### verty

What is space? Space is just the area between two points. There is space between the sun and the earth because the sun and the earth are not adjacent to each other. Can space exist if there are no points of reference? Not really, like if there was one object only, we couldn't really talk of there being space around it. There would be, but space is nothing, it is the lack of something being there. This is the basic idea and is why people thought there must be an aether to transmit light through space, although no aether can be detected. Although particle physicists talk of mediating particles, like the should be a graviton to mediate gravity, or a photon to mediate light. Because there is no detectable medium, there must be particles or vibrations to carry the force, if you understand. But anyway, so much for space.

Now time is similar. There is a past and a future because change happens and we have memories to remember how things were, and minds to comprehend how things were before we were around. But was there time before the first thing that even happened started happening? No, not really. If there was no change, there was no time. Time is just the progress of change.

Now when physicists say that time is variable because in a gravity well time passes more slowly or at high speed it passes more slowly, it just means that things change more slowly under those conditions. This shouldn't be too surprising, it would have been much more surprising if change happened at the same rate under all conditions, given the extreme conditions in the universe, for example close to neutron stars.

I don't know what more one could say about time, it is just change happening.

There are resources to learn pre-algebra, these videos are very nice. Or just ask if you need more help.

3. Sep 7, 2013

### ModusPwnd

This wiki might help you understand some of the concepts and jargon.

http://en.wikipedia.org/wiki/Arrow_of_time

And of course there is space-time,

http://en.wikipedia.org/wiki/Spacetime

These are two ways that time is often looked at in physics.

Check out the regular wiki on time too. The part on "conceptions of time" seems like it might be of interest to you.

4. Sep 7, 2013

### dingdongsilve

verty and ModusPwnd, thank you both for your answers. The videos appear to be an excellent refresher. Modus, the link you posted on spacetime shows an example of what I am trying to understand. I can't comprehend any thing in that article under the section 'Mathematics of spacetimes' . My goal is to obtain an understanding of mathematics and physics so that I know what, just for example, a Lorentzian manifold is, what it is used for and how it is applied.

5. Sep 7, 2013

### ZeroPivot

Is time constant?

6. Sep 7, 2013

### dingdongsilve

Is that a questions for me? :| Well, Barbour says that change provides the illusion of time and he doesn't believe that time exists at all. But, if it does indeed exist, doesn't special relativity say it's a variable? I have no clue, I'm so confused.

7. Sep 7, 2013

### ZapperZ

Staff Emeritus
Please note that this is the ACADEMIC GUIDANCE forum, not the physics subforums. Discussion with physics content should be done there.