Does black holes exist all around us?

In summary, Wikipedia says that in order for a black hole to form, the 'critical radius' must be bigger than the object's volume.
  • #1
wavingerwin
98
0
I read Wikipedia about black hole and interpreted it as such: that black holes exist all
around us, most of them are very, very small.

Suppose we have a drinking water glass (just suppose its mass is 10kg)
hence at radius 1.48 E-26 m (far smaller than even the radius of an electron)
there exists a black hole at the centre of mass of the glass.
(by the calculation done using escape speed equation, plugging in the speed of
light as the escape speed, we can get the value of r, in which any particle
even in the speed of light cannot escape from.)

because by calculation, the escape speed;v of any object inside the
radius will be greater than the speed of light hence it cannot escape, even light cannot.

so there is a tiny black hole at the centre of the glass. Am i right? please explain if not.

Thank you

here's the extract of the article in http://en.wikipedia.org/wiki/Black_hole
consider a heavy object of mass M centered at the origin. A second object with mass m starting at distance r from the origin with speed v, trying to escape to infinity, needs to have just enough kinetic energy to make up for the negative gravitational potential energy, with nothing left over:

mv2/2 - GMmr-1 = 0

That way, as it gets closer to r=infinity it has less and less kinetic energy, finally ending up at infinity with no speed.

This relation gives the critical escape velocity v in terms of M and r. But it also says that for each value of v and M, there is a critical value of r so that a particle with speed v is just able to escape:

r = 2GM/v2

When the velocity is equal to the speed of light, this gives the radius of a Newtonian dark star, a Newtonian body from which a particle moving at the speed of light cannot escape. In the most commonly used convention for the value of the radius of a black hole, the radius of the event horizon is equal to this Newtonian value.

rSchwarzschild = 2GM/c2
 
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  • #2
Welcome to PF, V.
I think that microscopic black holes are still open for conjecture. For a 'real' black hole, you need a body of at least 3.2 Solar masses in order for the gravitational collapse to take hold. The most likely place for that to occur is in a red giant star that goes supernova. If SpaceTiger is still around here, he's definitely the go-to guy for this.
 
  • #3
v_bachtiar said:
Suppose we have a drinking water glass (just suppose its mass is 10kg)
hence at radius 1.48 E-26 m (far smaller than even the radius of an electron)
there exists a black hole at the centre of mass of the glass.

No, the meaning of the radius you calculated is that if the mass of the glass were concentrated into a volume less than that radius, then a black hole will form.
 
  • #4
atyy said:
No, the meaning of the radius you calculated is that if the mass of the glass were concentrated into a volume less than that radius, then a black hole will form.

Right. As you shrink your radius you also shrink your mass, so there is no point at which there is a black hole inside any object that, well, isn't a black hole.
 
  • #5
mass of the glass were concentrated into a volume less than that radius, then a black hole will form.

I see.. it makes good sense for me
So for a black hole to exist, the 'critical radius' (of which any object cannot escape from
without moving at v>c) must be bigger than the volume of the object itself (which creates the black hole).
 

1. What is a black hole?

A black hole is a region in space where the gravitational pull is so strong that nothing, including light, can escape from it. This makes it invisible to the naked eye, making it difficult to detect.

2. How do black holes form?

Black holes form when a massive star dies and collapses under its own weight. This process is known as a supernova. The gravity of the star becomes so strong that it sucks in all the surrounding matter, creating a singularity, which is a point of infinite density and zero volume.

3. Can we see black holes?

Since black holes are invisible, we cannot see them directly. However, scientists can detect their presence by observing the effects of their strong gravitational pull on the matter and light around them.

4. Are there black holes in our galaxy?

Yes, there are believed to be millions of black holes in our galaxy, the Milky Way. However, most of them are relatively small and difficult to detect. The largest black hole in our galaxy is called Sagittarius A* and is located in the center of the Milky Way.

5. Are black holes dangerous?

Black holes are only dangerous if you get too close to them. The strong gravitational pull of a black hole can tear apart anything that gets too close, including stars and planets. However, since black holes are usually located far away from us, they do not pose a threat to our planet or our existence.

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