The effect of black hole

[Primarygun]

All light waves cannot "leave" the black hole, why?

The black hole reduces their speed or affects their gravitational field?

[lethalfang]

All light waves cannot "leave" the black hole' date=' why?

The black hole reduces their speed or affects their gravitational field?[/quote']

 

The escape velocity of earth is about 11.2 km/sec, i.e. an object has to travel at or above that speed to escape earth's gravitational pull.

The escape velocity of black hole within the event horizon is greater than the speed of light. Since nothing can travel faster than the speed of light, nothing can escape black hole.

[Primarygun]

The escape velocity of earth is about 11.2 km/sec

Why is it velocity but not the force?

[insane_alien]

because you do not need to apply a constant force to escape the earths gravity. 11.2km/s is the escape velocity for the surface of earth. the further from earth the lower the escape velocity.

[Primarygun]

the further from earth the lower the escape velocity.

Why?

If I leave the earth with 1ms^-1 with 10ms^-2 , I can't leave it?

[JaKiri]

Why?

If I leave the earth with 1ms^-1 with 10ms^-2 ' date=' I can't leave it?[/quote']

 

The escape velocity is the required velocity to escape without applying any additional assistive force. Dragging forces into it (boom boom) is unnecessary, especially as we're dealing with a (simplified) example where there can be no change of magnitude of velocity.

[Spyman]

If You had a ladder that went from the surface of the Earth to outer space, then You could leave with any speed You want.

 

If You where to fire a cannon bullet from the surface to outer space it would need the velocity of 11.2 km/sec or more, for not to fall back again.

 

With Black Holes and light it's more complicated but the photon could be viewed as an bullet, it can't be slowed down by gravity but can be pulled sideways. The intense gravity field inside the Event Horizon of a Black Hole is so strong that space-time is curved so hard so the photon is turned back, sideways, before it can escape.

 

If You had a ladder that was strong enough to withstand the strong tidal forces it would still bend so much inside space-time of the Black Hole so both ways would lead down.

(Unless You where able to climb faster than c which is impossible.)

[[Tycho?]]

All light waves cannot "leave" the black hole' date=' why?

The black hole reduces their speed or affects their gravitational field?[/quote']

 

For a black hole and a photon you may want to view it as a question of geometry rather than gravity.

 

A photon cannot slow down. So when a photon is trying to fly out of a black hole, it cannot simply slow down like an object tossed in the air. It is easier to think about it using the idea from General Relativity that gravity isn't a force at all, but instead the result of the curvature of space.

 

Think of a bowling ball on a matress, it will cause a large indentation around the ball. If you placed a marble close to the bowling ball, it would fall closer to the bowling ball. The curved matress can be an analogy for space being curved.

 

A black hole creates an area where space is infinitly curved. You can think of this as a bowling ball so heavy that it sinks so far into the matress that side of the hole is vertical- meaning that no matter how hard you try you can't climb the side. This works in a similar manner with a black hole- space is so curved that nothing can escape, because there are no paths which it can take to get out.

 

Uhh... I think that makes sense, if it doesn't somebody please correct me.

[Nicholas]

Light is not like matter. It travels at a constant velocity even in gravity.

Matter will always slow down coming out of gravity if it is not

accelerating. I do not believe escape velocity can be applied to light.

It is traveling just as fast anywhere outside a black hole.

That's the constancy of the velocity of light.

 

Light emmited at the event horizon of a black hole will

be redshifted by gravity. This is known as the Einstein shift.

But the Einstein shift to light would be infinite at the event

horizon; an infinite redshift or an infinite wavelength of light.

In this way GR predicts energyless light.

 

Energyless light?

PoppyCock.

The predictions of physics at black holes is the downfall of GR.

As Hawking put it: GR predicts its own downfall by predicting

singularities.

But he didn't go far enough.

Neither are there singularities nor are there event horizons.

[insane_alien]

so explain why we have evidence (indirect i will admit) that the event horizon is where the escape velocity is c.

[[Tycho?]]

so explain why we have evidence (indirect i will admit) that the event horizon is where the escape velocity is c.

 

Well it's the mathmatical result. We havn't observed it directly, but when an object collapses into a black hole the Schwarzchild radius of that object becomes the event horizon, its the point beyond which the equations tell us that light (nor anything else) would be able to escape the gravitational pull.

 

http://en.wikipedia.org/wiki/Black_hole#The_event_horizon

 

How I love wikipedia.

[EL]

']Well it's the mathmatical result. We havn't observed it directly' date=' but when an object collapses into a black hole the Schwarzchild radius of that object becomes the event horizon, its the point beyond which the equations tell us that light (nor anything else) would be able to escape the gravitational pull.

 

http://en.wikipedia.org/wiki/Black_hole#The_event_horizon

 

How I love wikipedia.[/quote']

 

 

Then why could the big bang escape the pull of all the matter of the universe!

[Nicholas]

That is the Big Bang debunked.

 

Its gravity would make it a black hole.

No possibility of expansion.

[ydoaPs]

not according to mathman:

The basic flaw is that there is no satisfactory theory describing "before" the big bang. Since it did happen his idea has been refuted by experiment. For all we know the entire universe is a big black hole. There is no good theory of what goes on inside a black hole either.

[Primarygun]

If I leave the earth with 11.2 km/sec, the earth cannot pull me finally?

[Primarygun]

All light waves cannot "leave" the black hole

Black hole varies the shape of the gravitational field of light, so the distance for light to travel is greatly increased though the displacement does not.

That's why light cannot leave?

That accounts for why the speed of light is not slowered?

[Spyman]

If I leave the earth with 11.2 km/sec, the earth cannot pull me finally?

If You where shot out of a cannon with escape velocity Your final velocity would be zero at infinite distance from Earth.

 

As gravity slows You down, You also gets farther away which weakens the gravity field. If fast enough start, gravity will decrease faster than speed.

Black hole varies the shape of the gravitational field of light, so the distance for light to travel is greatly increased though the displacement does not.

All bodies have a gravity field, it doesn't change unless the shape or mass/energy of the bodie change.

 

The gravity field is not made of light.

 

There is no path from inside to outside, all directions leads into the center.

 

Outside the Event Horizon, where light can escape, light loses energy while climbing out of the gravity well which causes it to get redshifted.

[Spyman]

Just read this in SPACE.com news and though it might help visualize the bending of space-time:

Wouldn't it be cool to stand toe-to-toe with a black hole, to stare it in the eye and finally see what one looks like?

Eye-to-Eye with a Black Hole http://www.space.com/scienceastronomy/050711_blackhole_looks.html

[BobbyJoeCool]

ok. As I understand it, gravity is created by mass. The more mass, the greater the effect of gravity's pull. Why does the center of a black hole have to be a singularity? What if it does have volume, albeit a very small about of volume. and that there is just enough mass in the universe to make gravity strong enough to condence all matter into a point with no volume (singularity), and it since it's a point with mass (thus infinite density) and possibly stores all the energy on the universe... the energy of the universe actually overcomes the gravetational forces of a universal black hole, and BOOM. everything is given an escape velocity from the sinularity and for a VERY long time (several trillion eons...) everything slowely comes to a stop and the gravetational forces of everything in the universe slowley draws everything back together back into a that singularity and it all happens again.

 

But back to what I was saying... who can say that there's a true singularity at thew center of a black hole? or has this been proven and I'm just an uninformed fool?

[Spyman]

who can say that there's a true singularity at thew center of a black hole?

Nobody knows whats inside the Event Horizon, we only have mathematical models which predicts certain properties.

 

And there are several of them:

 

Gravastar

Instead of a star collapsing into a pinpoint of space with virtually infinite density, the gravastar theory proposes that as an object gravitationally collapses, space itself undergoes a phase transition preventing further collapse, being transformed into a spherical void surrounded by a form of super-dense matter.

http://en.wikipedia.org/wiki/Gravastar

There is no proof that this new form of matter exists' date=' and thus gravastars remain for the moment no more than a potentially convenient proposal. But other astronomers are intrigued, both because black holes themselves remain mere theory, not fact, and because gravastars might explain strange physical observations that black holes don't.[/quote']

Since this new form of matter is very durable' date=' but somewhat flexible, like a bubble, anything that became trapped by its intense gravity and smashed into it would be obliterated and then assimilated into the shell of the gravastar.[/quote'] http://www.space.com/scienceastronomy/astronomy/gravastars_020423.html

 

Dark Energy Star

A dark-energy star is an alternative term for what are now called black holes, which may more accurately describe their nature and interaction with the universe. The surface of a dark-energy star behaves like a black hole, but the inside has 'negative' gravity causing matter to bounce back out.

http://en.wikipedia.org/wiki/Dark-energy_star

 

Black Hole

A black hole is a concentration of mass great enough that the force of gravity prevents anything from escaping from it except through quantum tunneling behavior.

http://en.wikipedia.org/wiki/Black_hole

 

The Singularity

At the center of the black hole, well inside the event horizon, general relativity predicts a singularity, a place where the curvature of spacetime becomes infinite and gravitational forces become infinitely strong.

http://en.wikipedia.org/wiki/Black_hole#The_singularity

 

Even without Relativity one could say that the pressure inside the body grows high enough to crush the structure of the atom and then the structure of the neutron.

In the 1920s, Subrahmanyan Chandrasekhar argued that special relativity demonstrated that a non-radiating body above a certain mass, now known as the Chandrasekhar limit, would collapse since there would be nothing that could stop the collapse. His arguments were opposed by Arthur Eddington, who believed that something would inevitably stop the collapse.

http://en.wikipedia.org/wiki/Black_hole#Rotating_black_holes

This is the core collapse. At this point neutron degeneracy pressure is sufficient to balance gravity; however the core has actually overshot the equilibrium point and undergoes a slight bounce' date=' creating a shock wave which slams into the collapsing outer layers of the star. A "proto-neutron star" begins to form at the core, though if it is massive enough, it will continue collapsing to form a black hole.[/quote'] http://en.wikipedia.org/wiki/Supernova

 

Now, You could take 10 E 37 kg pure Iron, (a very large quantity indeed), and shape it like a sphere, somewhere out in space and there You have a Black Hole with the density of Iron.

(The radius of the Event Horizon will be larger than the radius of the Iron ball.)

 

But inside the ball the pressure would be to high for the Iron nucleus, which will be crushed.

 

So, it may be crushed down to a Singularity or converted to some strange particles than can withstand the enormous pressure.

 

Does energy create gravity like matter ? & Whats the maximum density of energy, (infinite) ?

 

The Big Rip, The Big Crunch or something in between ?

 

Sorry to disappoint You, but current measurements points towards a Big Rip...

(It could still change though, with better understanding and new knowledge.)

Currently the evidence suggests not only that there is insufficient mass/energy to cause a recollapse, but that the expansion of the universe seems to be accelerating and will accelerate for the whole of eternity.

http://en.wikipedia.org/wiki/Universe#Fate_of_the_Universe

Two teams of astronomers reported that the universe was not only expanding' date=' but that the expansion was accelerating.[/quote'] http://www.space.com/scienceastronomy/solarsystem/accelerating.html