astronaught falling into a blackhole

[gib65]

I am told that as one falls into a black hole, the gravitational pull eventually becomes so strong that it literally pulls one apart. The difference in force between one's feet and one's head is so powerful that it has just this effect.

 

But then I wonder whatever happens to the electromagnetic force holding the atoms and particles together within one's body. Under normal circumstances (i.e. in the absence of black holes), if a body feels a pull at one end and nothing at the other (or at least a weaker pull), the latter end just gets pulled along (in virtue of the electromagnetic bonds holding it together) by the former end. Why wouldn't the same happen in the case of an astronaught falling into a black hole? Is the difference in gravitational force really that different between head and foot? Is it so different that not even the electromagnetic force can compensate?

 

That's the easy question. But I've got a trickier one:

 

I've also been told that as one falls towards a black hole (approaching the event horizon), time passes by more slowly relative to others who are farther away from the black hole. In fact, as one approaches the event horizon, time for him, relative to those farther away, approaches a full halt (i.e. someone at the event horizon would appear frozen in time).

 

Now, if we carry this over to our astronaught falling into the black hole, what would we say about time for his feet versus time for his head. If his feet are closer to the event horizon than his head, then wouldn't it appear to his head (assuming he's not dead from being torn apart) that his feet were moving much slower? Wouldn't it appear, therefore, as though he were catching up to his feet? Imagine this scenario should his feet be right at the event horizon (standing on it as it were). In that case, his feet should appear to his head to be "frozen in time" and therefore completely stopped. Rather than being pulled apart, he should experience being squished.

 

What's wrong with this picture?

[alex folen]

Good pondering. I believe the rate would be slower in spaghettification then that of time/light freedom because the energy consumed or expended in the spaghettification process.

[Mr Skeptic]

Well, gravity can indeed destroy objects, and it doesn't need to be a black hole to do so. Tidal forces can break apart planets that are too close to another massive object. Now as for your astronaut, the problem is not that gravity is pulling him, so much as that it is pulling in different directions and at different strengths. You get shredded. The technical term for this is spaghettification. The time dilation effects depend on how deep in the gravitational well you are; the spaghettification depends on how "sharp" the gravitational field is. Essentially this means that if you have a large enough black hole you should be able to survive falling through the event horizon (you'll still die later though), whereas a smaller black hole will shred you before you could reach it.

 

Now as for differential time dilation effects, I'm not too sure how it would work. I think that your legs would feel dead but act hyperactive (possibly twitch uncontrollably) due to how this would affect the nervous system. Remember that your legs are being tugged harder than the rest of you cause they're nearer. Maybe you'll see them shredded in slow motion? However I think you may be right about the flattening. Some theories say that it takes infinitely long time to cross the event horizon.

[gib65]

The technical term for this is spaghettification.

 

Really? And I thought alex was just being humorous.