# Just wondering

1. Aug 15, 2007

### narcokiller

what happens to light if it is not interfered with in any way, will it just carry on forever? What is the relationship between light and spacetime more specifically can there be time without light?

2. Aug 15, 2007

### CompuChip

Welcome to PF, narcokiller.

First question:
Yep, for this you can just view it as a particle: if it's not affected by anything it will run straight (which is the reason we have shadows, of course).

As for the second: I don't think light and time have anything to do with each other. You could have space without matter, as well as time without light. If I lock you in a thick metal box for a week, that may seem like forever to you, but time still passes. Light and matter just happen to move in space (and) time

3. Aug 15, 2007

### Claude Bile

Yes
While the properties of spacetime are obviously dependent on the speed of light, light itself has no direct effect. So yes, there can be time without light. If I am in a room completely absent of light, time will still pass yes?

Claude.

4. Aug 16, 2007

### narcokiller

you got to the answer i was really seeking the relationship, i have only just started studdying physics, however i did think that time would pause, thankyou

5. Aug 16, 2007

### CompuChip

Time is a strange thing. Mathematically, we can treat in on equal footing with space (this is why we speak about a 4-dimensional space-time), but whereas we can move freely in all spatial directions, we seem to be stuck in a forward movement through time.

Just keep on studying and asking questions, and you'll get some answers (and then study some more, and you'll begin starting to ask questions nobody can answer.... yet ).

6. Aug 16, 2007

### rbj

in fact, as i understand what the physicists say, is that this quantity we call c and first measured to be various numbers around 299792458 m/s and later assigned to that value and most often called the "speed of light", is really the speed of propagation of all ostensibly instantaneous interaction. when something changes here and has an effect over there, the speed of propagation of that effect is c. if it happens to be an electromagnetic interaction, then that would be an E&M wave of which visible light is part of that spectrum.

so it isn't that time is intrisically tied to light per se, but that time is tied to c in some way which is the speed of light in vacuo among the speed of other interactions (like gravity).