What Makes Black Holes So Mysterious and Dangerous?

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Discussion Overview

The discussion revolves around black holes, exploring their nature, existence, and the effects they may have on matter, particularly in extreme conditions. Participants share resources, pose questions, and speculate on the implications of black holes in both theoretical and conceptual contexts.

Discussion Character

  • Exploratory
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants seek information about black holes and their gravitational effects, asking for resources and clarification.
  • There is strong indirect evidence for the existence of large black holes at the centers of some galaxies.
  • One participant speculates about the physical consequences of a black hole coming into contact with Earth, suggesting extreme stretching of human bodies.
  • Another participant challenges the idea of black holes being molecular in size, questioning the implications of size and density as more material is absorbed.
  • Discussion includes the concept of the event horizon as a measure of size, with some arguing that the singularity's size is not physically meaningful.
  • There are differing views on the relevance of semantics in discussing the nature of black holes and their properties.
  • Participants discuss the potential for atoms to be ripped apart by gravitational differences near a black hole's event horizon, with some suggesting this could occur even outside the event horizon if the black hole is small enough.

Areas of Agreement / Disagreement

Participants express multiple competing views regarding the nature of black holes, their size, and the implications of their gravitational effects. There is no consensus on several points, particularly regarding the physical meaning of size and the consequences of approaching a black hole.

Contextual Notes

Limitations include unresolved assumptions about the nature of singularities, the definitions of size in relation to black holes, and the implications of gravitational effects on matter.

andrewking
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Black hole...

Hi I am Andrews, I want to learn about black hole and its gravity where I can collect information about black hole. If anyone knows about the site or about it reply me
Thanks in advance
 
Astronomy news on Phys.org
 
Thanks for your reply.I have another question about black hole.Is there any exist for black hole,if you know about it shre the information with me
 
There is strong indirect evidence for the existence of large black holes at the centre of some galaxies.

Ask in the astrophysics section.
 
did u no if a black hole came into contact wth the earth, all our molecules would expand causeing us to all be strechted out. for example, ud be like 20 yards tall, ur hands would be waaayyy up ther! wut a cool way to die.
 
u83rn00b said:
did u no if a black hole came into contact wth the earth, all our molecules would expand causeing us to all be strechted out. for example, ud be like 20 yards tall, ur hands would be waaayyy up ther! wut a cool way to die.

Sort of. The intense gravitational field would rip us apart (very quickly you wouldn't have any... recognizable human features left!) and we'd be peeled down to another single layer of atoms on the 'surface' of the black hole.
 
fasterthanjoao said:
The intense gravitational field would rip us apart (very quickly you wouldn't have any... recognizable human features left!) and we'd be peeled down to another single layer of atoms on the 'surface' of the black hole.

Aren't black holes molecular in size? what is, if any, the difference between the size of black holes. If more material is absorbed, then more gravity is possible, therefore the hole gets smaller but denser.
 
It can be useful to talk about the radius of the event horizon as being a "size" since we don't really know what is going on inside it and it generally doesn't matter anyway.
 
There is also a book by Stephen Hawking called The Cambridge Lectures which has a couple of GREAT lectures on Black Holes.
 
  • #10
How could a black hole be molecular in size. I understand the great gravity pulling in on the particles but wouldn't they only be compressed to the plank length?
 
  • #11
u83rn00b said:
did u no if a black hole came into contact wth the earth, all our molecules would expand causeing us to all be strechted out. for example, ud be like 20 yards tall, ur hands would be waaayyy up ther! wut a cool way to die.

Yes, but black holes also stretch light rays. We would look red all over!
You are right about one thing, it's a cool way to die.
 
  • #12
russ_watters said:
It can be useful to talk about the radius of the event horizon as being a "size" since we don't really know what is going on inside it and it generally doesn't matter anyway.
I really don't see any physical meaning of size here.

What's the meaning of size for an ant that sits on a deflating balloon when it has deflated to a point?
 
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  • #13
I think that is Russ's point MJ, that it's pointless to try and talk about the size of the 'singularity', but what you can talk about for black holes is the radius of the event horizon, which does depend on the black hole mass and hence allows black holes of different 'sizes'.

I think you'll find you are actually agreeing with Russ.
 
  • #14
Wallace said:
I think that is Russ's point MJ, that it's pointless to try and talk about the size of the 'singularity', but what you can talk about for black holes is the radius of the event horizon, which does depend on the black hole mass and hence allows black holes of different 'sizes'.
My point is that that the r-coordinate in the usual Schwarzschild coordinate chart does not represent a radial or any other physical distance. For instance the size of a black hole is most definitely not \frac{4}{3} \pi r^3.
 
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  • #15
Semantics!
 
  • #16
Wallace said:
Semantics!

What?! Sementics?
 
  • #17
Wallace said:
Semantics!

What?! No, I mean what does that mean?
 
  • #18
Wallace said:
Semantics!

What?! No, I mean what does that mean?
 
  • #19
From Dictionary.com:

Semantics is commonly used to refer to a trivial point or distinction that revolves around mere words rather than significant issues: “To argue whether the medication killed the patient or contributed to her death is to argue over semantics.”
 
  • #20
going back to the death thing... if u went ova a blck holes event horizon, ur atoms would b ripped apart, as the gravitational difference between very small distances is so great... ie. the front of ur atoms would b traveling faster than the back of ur atoms and hence would b ripped to pieces... its not a nice way 2 die, but at least ud b going out with a bang =P
 
  • #21
Teresa said:
going back to the death thing... if u went ova a blck holes event horizon, ur atoms would b ripped apart, as the gravitational difference between very small distances is so great... ie. the front of ur atoms would b traveling faster than the back of ur atoms and hence would b ripped to pieces... its not a nice way 2 die, but at least ud b going out with a bang =P

If a black hole is small enough, this happens outside the event horizon.
 

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