Thread: An odd thought on blackholes & time.

So you know its 3am, insomnia has set in so perfect time to have strange thoughts on cosmology right?

A thought on blackholes. We all know the speed of light is a constant & light cannot escape blackholes. Light is for the most part, without mass.

I was thinking, Is it possible the reason light cannot escape is not because of gravity, but due to time? Could time slow down light so much that once it enters a blackhole, it cannot travel fast enough to overcome the severe slowing of time?

Space & time are connected, I hate the word infinite, but could time be so compressed to a point that light is unable to travel faster than the warping of time will allow?

Consider light, it is a constant. it is of course effected by gravity. That has been proven watching it curve through space, however its speed remains the same. It takes longer to travel around the curved path than a straight line, but the speed is the same.

However, when in a blackhole, time dilation could be so great as to prevent light from overcoming it.

Just a fun late night thought, maybe someone smarter than me can help me with this thought.

In a sense you are right. And wrong ...

The reason light cannot escape from a black hole is the extreme curvature of space-time. And time doesn't really slow down near a black hole: if you were falling into a black hole, your watch would continue ticking away normally and light would pass you at the speed of light. But time does appear slowed to an external observer (which means that someone watching you fall into a black hole would see you get increasingly red-shifted until you disappeared).

All of these things -- space-time curvature, gravity, time slowing, mass, gravitational red-shift, etc. -- are all different perceptions/descriptions of the same thing.

Originally Posted by GoldenRatio

Is it possible the reason light cannot escape is not because of gravity, but due to time?

You are close. The reason why nothing can escape from beyond the horizon is because the radial coordinate becomes time-like in that region - in other words, going into the future means getting closer to the singularity. Since time only ever "flows" into the future, there simply isn't any way to travel back up and out of the horizon.

ah yes. knew all that but logic & sleep deprivation dont go together well.

Could time be considered a constant? A second is a second, a hour a hour & the effects of gravity, simply relative?

Originally Posted by GoldenRatio

Could time be considered a constant? A second is a second, a hour a hour & the effects of gravity, simply relative?

Yes, I think this is a good way to look at it. All clocks will tick at exactly "one second per second", always and everywhere. However, the relation between clock readings at different places may change with relative velocity and gravity - that's what the theory of relativity is for.

I read Markus's written explanation and feel I am close to understanding this sort of thing. Then I see his signature line, with - to me - incomprehensible symbols and I leap out of bed and run around the room screaming, "The sky is falling! The sky is falling!"