# B Time in a timeless place

1. Jun 21, 2017

### BL4CKB0X97

Firstly, I don't know where to put this. Sorry if it's in the wrong place.

I was thinking about being past an event horizon, and recalled that time stops in such a place and physics breaks down.

Which made me think: should I find my self alive(and conscious)in a timeless area, surely that fact that I am there introduce a timeline? From human perspective, even if you were in complete sensory isolation, you still have a gist of time passing. Would this be the same?

Even if I could not perceive time passing, Surely my appearance would be an event,a moment where something changed. Change is impossible without time for it to happen.

I am aware that noone would survive such conditions like an event horizon ,but humour me. Thanks!

2. Jun 21, 2017

### phinds

No, it does not
No, it does not.

3. Jun 21, 2017

### Staff: Mentor

Physics does not break down at the event horizon.
Some coordinate systems break down - but that is purely an issue of the mathematical description, and we have coordinate systems that work properly there. This is analogous to your longitude if you are exactly at the North Pole. It is undefined. That doesn't mean the Earth breaks apart there. If you walk over the North Pole, you don't even notice anything unusual, because the undefined longitude is purely a mathematical issue without physical relevance.

Atoms can cross the event horizon normally. This includes humans, which are very complex arrangements of many atoms. There is nothing special about humans.
If the black hole is large enough, you can probably cross the event horizon safely. You just cannot go back, and you will hit the center soon.

Physics as we know it does break down at the center. That center is a point, or at least something extremely small - you can't be there as human anyway.

4. Jun 21, 2017

### Staff: Mentor

Actually it is a moment of time. So it's not properly thought of as a "place" of any sort.

5. Jun 22, 2017

### timmdeeg

I think here you refer to what GR predicts, the point. Whereas if the center is "something extremely small" (what QG perhaps might predict sometime) as mfb mentioned then presumably it is a place. Kindly correct if wrong.

6. Jun 22, 2017

### Staff: Mentor

Well, we don't know what is there. That includes the question what exactly "there" even means in spacetime. But this is a B-level thread, I tried to keep it simple.

7. Jun 22, 2017

### jbriggs444

If quantum gravity manages to extend general relativity and eliminate its singularities, one possibility is that it will do so by explaining the notions of "time" and "position" as emergent properties of some underlying reality. In that case, the "moment in time" description that we use in the language of general relativity will still be approximately applicable and the "position in space" description will still not be.

8. Jun 22, 2017

### BL4CKB0X97

This post has confused me. I have not heard of this,but my knowledge is very limited.

How is it a moment in time but not a place?

If it is not a place, does this mean it has-for want of a better word- lost the other three dimensions?

To everyone, your posts have really helped me. I have little education at the moment, which is why I am hear. To be told I am wrong (with evidence,of course) is as much a victory as being right. One more mistake I will never make again.

9. Jun 22, 2017

### Ibix

The singularity in a black hole isn't a point at the centre. It lies in the future of any object crossing the event horizon. In a sense, this is the reason you can't escape a black hole. Once you've crossed the event horizon you can't avoid the singularity any more than you can avoid tomorrow morning out here.

10. Jun 22, 2017

### phinds

Yeah, this one makes my head hurt too. Once you are inside the Event Horizon of a BH, your world-line ends at the singularity. That is, the singularity is in your future regardless of any physical motion you attempt to make. I can't explain it, really, I"m just regurgitating what I've heard here, but I'm sure @PeterDonis will give you a good explanation.

11. Jun 22, 2017

### jbriggs444

There are a lot of posts in these forums with various plain language descriptions that try to meaningfully capture the notion. It is hard to wrap one's head around.

The way I understand it, the idea is that if you are inside the horizon, the singularity is not so much a place -- no matter where you go in space, you will still arrive at the singularity. It is a moment in time -- it is in your inevitable future.

However, the above is not quite right. If for no other reason than that the "singularity" is neither a time nor a place. It is a feature of the mathematical description. Like the asymptote to the function $y=\frac{1}{x^2}$. To speak by analogy, the singularity is not a point on the graph. It is a feature of the graph.

12. Jun 22, 2017

### BL4CKB0X97

That I get. Thanks.

13. Jun 22, 2017

### BL4CKB0X97

Another question that just popped up. Would it be light or dark beyond the event horizon,hypothetically?

I can see how both could be correct, but I'm not sure what is.

14. Jun 22, 2017

### phinds

When you pass the EH of a supermassive BH, very little happens at the EH except that you can't get back out. You can still see objects that are outward from the EH

15. Jun 22, 2017

### BL4CKB0X97

So inside the EH it would be pitch black?

16. Jun 22, 2017

### jbriggs444

Light from the outside stars still shines in. Light generated from the the reading lamp in your space capsule still illuminates the copy of Treasure Island that you will never finish reading. The fact that your tail lights will never be seen from outside the EH does not mean that it must be dark inside.

That said, I do not recall the red shift situation for an observer who has freely fallen from infinity as he gazes back at the outside stars.

17. Jun 22, 2017

### BL4CKB0X97

I was meaning about outside the capsule, not the light that you introduce but the space itself. Space is black this side of the EH, but with all the matter and light being pulled in the EH, but it be bright and hot or dark and cold?
A similar question to what you would see going FTL.

18. Jun 22, 2017

### timmdeeg

Hm, I'm just speculating now. Let's consider the center of a black hole as a hot and dense area of Planck density. Then particles entering the black hole from different sides will enter said area at different locations, describable by different coordinates. Also, as this area has a finite volume one could think of a thermal equilibrium to exist, allowing diffusion processes without time limit. Sure, the latter point is highly speculative, as we don't know the state of matter under such conditions.

19. Jun 22, 2017

### Staff: Mentor

See above: You still see stars. They appear a bit blueshifted and brighter redshifted and dimmer than before.
"What would the laws of physics predict if these laws do not apply" is a meaningless question.

Last edited: Jun 22, 2017
20. Jun 22, 2017

### timmdeeg

They appear a bit redshifted (due to the Doppler-effect) to the free faller. A stationary observer outside the horizon will see them blueshifted.