# Expansion and acceleration of the Universe

1. Nov 28, 2012

### nicholasmath

I know that it is observed that galaxies and stars thousands and millions of light years away are expanding away from our own galaxy and that it's observed that not only are they moving away from us but they're accelerating away from us. This is thought to be the anti gravitational field of dark energy.

But I was wondering if perhaps time for us is slowing down? Hence it only appears like everything is accelerating in the universal expansion when perhaps everything may be moving at a constant speed but degrading time. since s=d/t. If time slows down speed would increase. Anyway its just a thought and I'd like to know if anyone else thinks that it may be plausible

Last edited: Nov 28, 2012
2. Nov 28, 2012

### Staff: Mentor

Actually it's dark energy that causes this, not dark matter.

I'm not sure this is coherent, but rather than try to disentangle it, I recommend that you read Ned Wright's Cosmology FAQ on this question:

http://www.astro.ucla.edu/~wright/cosmology_faq.html#CC

Read his answer, and then follow the links he gives to more detailed explanations of the concepts he's using. That may help you to formulate your question better.

3. Nov 28, 2012

### nicholasmath

I'm just asking if its possible that time itself is slowing down. maybe not universally but at least for our galaxy. I mean if we are accelerating then for the speed of light to remain constant our time must decrease and hence everything outside the galaxy may in fact look like its moving faster than it actually is. But if time is slowing down for some unknown reason there may not even be any dark energy and galaxies may not be accelerating away because its covering greater distances in the same amount of time, but it may in fact be covering the same distance in the same amount of time, but because our time is slowing ( just a theory) it would appear as though the galaxies are moving away at a faster rate. It would just appear as though its speed increases as time goes on I hope. I'll look through the link above in more detail I know there are alot of things I still need to read up on but as a novice I think it allows me to think about these things without any predefined boundaries of thought.

4. Nov 28, 2012

### tom.stoer

It's hardly possible to discuss whether "time itself is slowing down" as long as we do not specify the definition of time:
- coordinate time
- proper time
- time of macroscopic or thermodynamic physical processes

5. Nov 28, 2012

### Staff: Mentor

nicholasmath, your follow-up post didn't really help to clear things up to the point where I can usefully comment. Thinking about things on your own "without any predefined boundaries of thought" is a good thing, but in order to communicate your thoughts to others it really helps if you at least know the basics of the standard vocabulary for talking about the subject. The link I gave you, and the other links that appear there, may help with that.