Biological systems in relativistic effects?

[MWresearch]

Suppose there is a stationary person near rapidly changing curvature in space time, near a black hole. Ignoring tidal forces that would kill them and the force of intense force of gravity against whatever was holding them stationary also cause their own weight to crush them, I have a scenario I can't quite complete.

 

Let's say the person sticks their hand out closer to the black hole. Their hand experiences a much greater gravitational effect, modeled by tidal forces. But, suppose a person were to touch another object while they reached their hand out. How would the impulse of touch travel? From the frame of reference of the person at their head, the hand's time should be dilated, but the person's brain isn't and furthermore the person can see when they think they are touching the black hole, so he delay can't be great enough such that a person is visually observing that they are touching something before the force of the touch is felt, because that would imply the electromagnetic repulsing between atoms isn't affecting their hand, thus creating a violation in the exclusion principal.

So, would a person measure the sense of touch as highly delayed or...what would happen involving the time it takes for a person to know they touched something?

[Delta1212]

It takes time for the signal to travel through your nervous system to teach your brain and experience a sense of touch. The speed it takes is significantly less than the speed of light, so however long it takes like to reach you from the point of touch, the sensation is going to come after. You won't feel whatever you're touching before the light reaches your eye.

[MWresearch]

But that's exactly the point. Would a person observe, with photons, that they are touching an object before they feel they are touching it?

Or at least, would they observe a highly significant delay? Because their hand is relatively more dilated than their head, but at the same time, it's not their hand that is interpreting the sense of touch, so...

[Strange]

But that's exactly the point. Would a person observe, with photons, that they are touching an object before they feel they are touching it?

Or at least, would they observe a highly significant delay? Because their hand is relatively more dilated than their head, but at the same time, it's not their hand that is interpreting the sense of touch, so...

 

As the normal delays are typically hundreds of milliseconds, the extra picoseconds (or whatever) in your scenario hardly seem relevant. But feel free to do some calculations to show otherwise.

[MWresearch]

Well I don't know that its extra picoseconds or that its extra anything it all. What calculations was I suppose to have shown by asking a question on whether or not there are any extra calculations at all? I can't figure it out, maybe you could explain.

[Strange]

Well, while the tidal force is insufficient to rip the nerves apart, I doubt there is any noticeable delay due to time dilation. (But then again, intuitions are often wrong when it comes to black holes).

 

I did wonder how you would continue to feel your extremities when falling through the event horizon because the nerve impulses obviously couldn't pass back through the horizon to your brain. But you would be falling through the event horizon faster than the nerve impulses were travelling back, so they would never have to go back through the event horizon. Which is, kinda, the same reason that you would never lose sight of the the person in front of you as they fell through the event horizon. Their photons could never pass back through the EH, but, instead, you would catch them up.

 

Sorry for the digression. Maybe it is another way of saying: I don't know....

[MWresearch]

Well, is there anyone who does? It's too bad there's no experienced members who have studied relativity.

I guess it would be possible for someone to touch something without feeling it, I was trying to avoid a scenario where someone was physically passing through another object because they didn't feel it, like saying you can't pass through a wall just because you're drunk.

[Mordred]

Tnruthfully how can anyone answer this without, with emphical data? We can speculate till the cows turn blue.

Plenty of ppl studied relativity. What does personal reactions to being torn apart have to do with it?

[Delta1212]

Well, is there anyone who does? It's too bad there's no experienced members who have studied relativity.

 

I guess it would be possible for someone to touch something without feeling it, I was trying to avoid a scenario where someone was physically passing through another object because they didn't feel it, like saying you can't pass through a wall just because you're drunk.

Why would you pass through an object just because the signal telling you you've touched it hasn't reached your brain yet?

[MWresearch]

How can anyone answer? Probably by physicist using physics. Simplify the biological system. Instead of it being a person, simplify it to an electric signal traveling through a copper wire. That's a start.

 

And why would you pass through an object? Even I have to ask "seriously?" I just said that you wouldn't pass through an object and that I was trying to avoid that scenario. I guess this is some kind of time travel paradox where trying to prevent an action ends up causing it?

[Strange]

It isn't really clear what you are asking.

 

For example, you pose the question as if you could be stationary outside the event horizon and just reach out towards it. This is physically impossible and so the answer is undefined. In reality, you would be in free fall and, apart from tidal forces, there would be no effect on nerve impulses or any other aspect of your biology. (As far as I know.)

Edited March 4, 2015 by Strange

[MWresearch]

The question is somewhat broader, but it's asking I guess if someone would see themselves touching something before they actually felt it due to time dilation in the hand.

[Strange]

The question is somewhat broader, but it's asking I guess if someone would see themselves touching something before they actually felt it due to time dilation in the hand.

 

I can't imagine a situation where the time dilation would be significant compared to how incredibly slowly nerves convey signals.

[Endy0816]

I'm wondering what would actually happen to your poor extremity. I don't think you are supposed to be able to 'know' where an event horizon is, but have to imagine that the physical damage would be a clue when you've reached past it.

[MWresearch]

But that's what I mean, would time dilation actually create a delay in the nerve signals?

[Strange]

In principle, yes. In practice your arm would be torn off before you noticed.

[Delta1212]

How can anyone answer? Probably by physicist using physics. Simplify the biological system. Instead of it being a person, simplify it to an electric signal traveling through a copper wire. That's a start.

 

And why would you pass through an object? Even I have to ask "seriously?" I just said that you wouldn't pass through an object and that I was trying to avoid that scenario. I guess this is some kind of time travel paradox where trying to prevent an action ends up causing it?

My confusion is over why that scenario needs avoiding. Why would there be any reason for that to happen in the first place?

[MWresearch]

To be honest Strange that's just a copout answer, because electrons and photons and other signals can still travel outward from a black hole so long as they were never observed crossing they event horizon and already mentioned we should neglect the damage a person would suffer at the start.

[Mordred]

Assuming you can maintain integrity, all particle interactions and corresponding force medications will experience the same time delay from an outside observers reference frame.

 

However from the same reference frame as particles themselves there is no time delay

Edited March 6, 2015 by Mordred

[MWresearch]

You're not being specific enough for me to understand how your point applies. Could you apply what you're saying to exact elements of the proposed scenario?

Edited March 6, 2015 by MWresearch

[Mordred]

Seems pretty clear to me. An outside observer measuring any interactions occurring will see the time delay. However if you are in the same reference frame as the particles in your arm you will not notice any time dilation. In other words the only way to have a time delay is if your brain is in a different reference frame than your arm.

From the reference frame of other particles in your arm, they are all in the same reference frame (they will not notice a time delay). Relativity depends on the reference frame of the observer. You didn't specify

Edited March 6, 2015 by Mordred

[Strange]

To be honest Strange that's just a copout answer, because electrons and photons and other signals can still travel outward from a black hole so long as they were never observed crossing they event horizon and already mentioned we should neglect the damage a person would suffer at the start.

 

The trouble is, on the one hand, you don't provide enough information to calculate anything: how big is the black hole, how far are you from it, etc.

 

On the other hand, you appear to be suggesting something that is physically impossible: hovering just outside the event horizon, an area where the difference in time dilation is significant but tidal forces aren't, etc.

 

As such I don't see how anyone can give a sensible answer.

 

Why is this of interest? Given details, someone could calculate the time dilation invoivled, but so what. You would be in free fall so that you wouldn't notice it anyway.

[imatfaal]

Tidal forces at the event horizon of a supermassive black hole are almost negligible; so just choose a really really big one and all ideas of the arm being pulled off by tidal forces are dismissed.

 

[back of envelope sums indicate that for a record breaking black hole a standard human would have order of 10s of micronewtons differential in force between head and foot at event horizon]

 

Tidal forces vary with the inverse cube - whereas gravitational potential varies with the inverse of the the root; so there might be a possibility of a measurable time dilation without tidal effects ripping asunder - although not in such a small test object as an arm

 

[further back of envelope sums have a fast-ticking observer at a huge difference seeing a disparity in the local time of head and feet of a few percent. remember this is where you have possibilities of rapid changes in time dilation and even a mathematical singularity at the EH]

 

To avoid problems of EH mathmatical singularity in Schild Coords I have done sums at 10 and 8 metres out from EH of 20 million solar mass black hole.

[Strange]

Tidal forces at the event horizon of a supermassive black hole are almost negligible; so just choose a really really big one and all ideas of the arm being pulled off by tidal forces are dismissed.

 

But then the time dilation along the length of the arm would be insignificant as well.

 

For the time dilation to be noticeable my back-of-the-envelope calculation suggests you would need a black hole a few metres in diameter, so about a thousand times the mass of the Earth. In this case, the tidal forces would be pretty high.

[imatfaal]

 

But then the time dilation along the length of the arm would be insignificant as well.

 

For the time dilation to be noticeable my back-of-the-envelope calculation suggests you would need a black hole a few metres in diameter, so about a thousand times the mass of the Earth. In this case, the tidal forces would be pretty high.

 

Not by my sums I wonder where we are differing. I have the time factor between fast ticking very distant observer as t = t_fast *[sqrt (1-r_0/r)] . When r is close to r_0 then you get a rapid change in the time factor with small changes in r