Why would a star explode into a supernova first and then form a black hole when gravity on anybody is maximum at its surface ?

Why cant the start just explode and its matter just hush away for formation of new stars.
And if nothing can escape black hole then how does the information of its presence escape from it, this is all confusing, the concept of black holes is absolutely ridiculous.

Now here is a huge problem ! When a star forms into a black hole then radius of its gravitational pull doesnt increase then why is a super massive black hole at galaxies center theory required ?

Here is a killer ! Please read this para 10 times as all humans on this planet r victims of alien brain wash to stop us inventing warp drive. If its not the light that bends but space, then will we ever know about it, because the light should regain its path once it passes away from black hole along with the regaining of curvature of space ? But we do get a Lens effect suggesting that its not space but light that is bending, if that is correct than how many modern physics theories collapse ?

Please correct above statements for their deficiencies.

Blacks holes are formed when an expression is divided by zero.... most mathematicians would call such results meaningless.... but NO, relativists claim enlightment.

>> suggesting that its not space but light that is bending,

This is correct,..... we really do need a dump truck to take away quite a bit of trash.

Hello RawThinkTank:

Why would a star explode into a supernova first and then form a black hole when gravity on anybody is maximum at its surface ?

A supernova happens when a star is in the process of collapse. The star is not a solid object, and the outer layers are "held up" by the internal pressure from fusion in the star. As the nuclear "engine" of the star starts to die, gravity takes over and the star collapses. When it collapses to the size of a neutron star, there is a sudden halt due to neutron degeneracy pressure effects, which causes much of the material falling inwards to bounce back, and be ejected into space, leaving a smaller core. However, for very large stars, even the degeneracy pressure cannot hold the star up against gravity. In that case, the collapse continues and a black hole forms.

And if nothing can escape black hole then how does the information of its presence escape from it, this is all confusing, the concept of black holes is absolutely ridiculous.

The information of the presence of the hole is carried by the curvature of the surrounding spacetime. Black holes are sometimes called "fossil fields" for the reason that the remnant spacetime curvature reflects the matter which used to be there before it fell into the hole.

Now here is a huge problem ! When a star forms into a black hole then radius of its gravitational pull doesnt increase then why is a super massive black hole at galaxies center theory required ?

I don't understand your statement or your question. Can you explain, please?

Here is a killer ! Please read this para 10 times as all humans on this planet r victims of alien brain wash to stop us inventing warp drive. If its not the light that bends but space, then will we ever know about it, because the light should regain its path once it passes away from black hole along with the regaining of curvature of space ?

Again, I'm not sure what you're saying here. In general relativity, the spacetime near the hole is curved, and light follows that curvature near the hole, which is why light rays bend around the hole.

But we do get a Lens effect suggesting that its not space but light that is bending, if that is correct than how many modern physics theories collapse ?

If you're talking about gravitational lensing here, then no modern theories collapse. General relativity describes what we see very accurately indeed.

Zarkov,

You are wrong, as usual. Black holes are physical objects, not mathematical expressions.

The only trash which needs removing here is your post.

>> Black holes are physical objects,

Oh, and how do we see these black holes?

Oh, and how do we see these black holes?

We see them primarily by means of radiation emitted from their accretion discs.

>> We see them primarily by means of radiation emitted from their accretion discs.

Oh, then you can't see them directly, it is an inferrence or speculaton that they then exist.

Bit like the voices in Joan of Arc's head.

Oh, then you can't see them directly, it is an inferrence or speculaton that they then exist.

An inference, yes. A speculation, no.

Bit like the voices in Joan of Arc's head.

No, not really.

>> We see them primarily by means of radiation emitted from their accretion discs.

Oh, then you can't see them directly, it is an inferrence or speculaton that they then exist.

Bit like the voices in Joan of Arc's head.

Than,we could also say that tornados don't exist.You can't actually see tornadoes,you can only see what effect and destruction they have on the outside environment.You can only "see" tornado,when you see the dust,parts of homes,cowes swirling around the centre of each invisible tornado as well as its destructive power that is left on the environment.So,the tornado also has its "event horizon".The same finding system works for black holes.You can't see black holes directly,that's what makes them black holes,no light comes back once it's trapped and crushed into singularity,but what you can see is black holes' destructive effects on the environment they are in.The gas and the interstellar dust are sorrounding the black hole and they rub themselves which creates temperatures millions of degrees because of the inertion between the particles.Enough close and the inertion will speed up to the speed of light,just before falling into oblivion...

I thought that the type of radiation we're talking about is called Hawkin radiation, and has been observed. Hence the fame of a certain Stephen Hawkin. Is this not right?

I thought that the type of radiation we're talking about is called Hawkin radiation, and has been observed. Hence the fame of a certain Stephen Hawkin. Is this not right?

As far as I know,there is not sure,if there is Hawking radiation-not in an absolute sense.They detect black holes in this way:Gas and the dust are heated up to millions od degrees,and they emmit X-rays,gamm-rays,plus astronomers measure the gravitational lensing,plus the speed of stars around the black hole,and etc..
You see,it has been experimentally proven that mass is an form of energy.In time mass would transform itself into pure high-energy plasma.So,since black holes are uber-masses of the universe in a very small spot/place/volume,they should lose mass-which converts into energy.However,they have said that will try due to Hawking radiation find black holes-which I don't it will happen at all.I also don't think that Hawking radiation is correct theory,since nothing can get out fro the black hole.The only way,in my opinion,an photon can runaway from the black hole is if this photon is not too close to the event horizon.But that doesn't make black hole losing mass.I don't care what Hawking radiation says about virtual particle and anti-particle collision and than in that sense losing mass which transforms into energy-because it's virtual.There is a way how black hole lost their mass/energy,however,I truly don't think it has something to do with Hawking radiation,since it hasn't been yet proven in laboratory experiments-plus no particle can get faster than the speed of light.We will see yet what would happen...

Please read this u humans 100 times, Ur future depends on it !

Light should regain its path to its original straight lined direction once it passes by the BH as the space too regains its straightness along the path of light; Because other wise it should not have bend with space as it approaches near the BH along with space.

But we do get a Lens effects in space suggesting that its not space but light that is bending, if that is correct then space bending is an alien conspiracy imparted in the most intelligent human scientist to turn our course of inventions to destructive ones.

Hope U can comprehend that one; And yes I will keep trying till U get it unless those aliens don’t get me first.

Please read this u humans 100 times, Ur future depends on it !

Light should regain its path to its original straight lined direction once it passes by the BH as the space too regains its straightness along the path of light; Because other wise it should not have bend with space as it approaches near the BH along with space.

But we do get a Lens effects in space suggesting that its not space but light that is bending, if that is correct then space bending is an alien conspiracy imparted in the most intelligent human scientist to turn our course of inventions to destructive ones.

Hope U can comprehend that one; And yes I will keep trying till U get it unless those aliens don’t get me first.

Yes,but it is proven that light is bended,when passes close to an massive object,nobody knows why,but it simply is.I suppose that would mean light particles/photons must have some sort of mass,no matter how small it is.

If light doesn't have a mass, how can it get sucked into a black hole?
Simple,In a Black Hole, light traveling outwards towards an event horizon is pulled back by the very strong gravitational field, because of the warping of space-time inside the event horizon, regardless of the lack of a photon mass. This prevents light from ever escaping the Black Hole.

What makes little sense to me about black holes is that a finite mass can move reference frames toward itself at >= c (within the reference frame objects move at < c), yet a finite mass cannot itself attain c by accelerating. That seems contradictory. It makes more sense to me that a finite mass would always move reference frames toward itself at < c. You should still get the evidence of “black holes” that astronomers have seen. I don’t think any other GR confirmatory evidence would be rejected. I don’t think any observational data has shown beyond reasonable doubt that a mass is moving reference frames toward itself at >= c.

Another contradiction is Hawking radiation. Books on GR point out that the crew of a ship crossing an event horizon should not find that anything special happens; that makes intuitive sense because the reference frame in which the ship exists could be moving at c relative to a singularity a billion light years away; the event horizon is of only relative significance. Yet another chapter of the same book will say that Hawking radiation indeed makes the event horizon a special place, a place of absolute significance. If reference frames always moved at < c relative to any object, Hawking radiation would not exist.

If I were a physicist with a good handle on the GR math, I’d look for a logical resolution to these contradictions. Who knows what else would fall out of a fix, perhaps something predictable?

zanket:

What makes little sense to me about black holes is that a finite mass can move reference frames toward itself at >= c

I have no idea what you mean by this. A reference frame is a point of view. How can you move a point of view towards yourself, at whatever speed?

Another contradiction is Hawking radiation. Books on GR point out that the crew of a ship crossing an event horizon should not find that anything special happens

What the books mean is that the crew of a ship would not see any obvious change in the space around them. Their clocks would not suddenly go haywire, for example. However, they would discover that they could no longer halt their progress towards the singularity, let alone get back outside the horizon.

ther chapter of the same book will say that Hawking radiation indeed makes the event horizon a special place, a place of absolute significance.

Yes, but there's no contradiction there. The event horizon is significant even for the astronauts; it is the point of no return. The fact that they wouldn't notice it as they crossed it does not in any way diminish the significance.

I think zanket is referring to an object in an inertial reference frame at and beyond the event horizon, and the superluminal velocity of that object relative to a distant observer.

I don't know if velocity relative to the singularity is really meaningful?

I have no idea what you mean by this. A reference frame is a point of view. How can you move a point of view towards yourself, at whatever speed?

What Pete said. It’s not the reference frame per se that matters, but the objects within it.

Yes, but there's no contradiction there.

There’s no contradiction as long as nobody measures an object moving at >= c. I didn’t explain myself as to how somebody could so measure.

Let ship H be hovering just above the event horizon. You free-fall past H and, at the moment you cross the event horizon, you shine a light radially outwards. What speed do you measure for H? It must be >= c, because your light doesn't gain on H. According to GR books you can still see H so they can still send you communications (like the image of their ship that you see), but how, since the rate of their clock could not be > zero by your reckoning?

That makes the event horizon a special place indeed, and it seems it’s a GR self-contradiction. Can you resolve it?

The event horizon is significant even for the astronauts; it is the point of no return. The fact that they wouldn't notice it as they crossed it does not in any way diminish the significance.

Tests of local space could confirm the crossing. For example, they could check for the “continental divide” that is Hawking radiation as the divide passes through their ship.

zanket:

Let ship H be hovering just above the event horizon. You free-fall past H and, at the moment you cross the event horizon, you shine a light radially outwards. What speed do you measure for H? It must be >= c, because your light doesn't gain on H.

I don't think so. The speed you measure for H is the rate of increase of distance between yourself and H. That will not be greater than the speed of light.

This is where it becomes very important to distinguish proper time from the time measured by an observer far from the horizon.

What makes little sense to me about black holes is that a finite mass can move reference frames toward itself at >= c (within the reference frame objects move at < c), yet a finite mass cannot itself attain c by accelerating. That seems contradictory. It makes more sense to me that a finite mass would always move reference frames toward itself at < c. You should still get the evidence of “black holes” that astronomers have seen. I don’t think any other GR confirmatory evidence would be rejected. I don’t think any observational data has shown beyond reasonable doubt that a mass is moving reference frames toward itself at >= c.

Another contradiction is Hawking radiation. Books on GR point out that the crew of a ship crossing an event horizon should not find that anything special happens; that makes intuitive sense because the reference frame in which the ship exists could be moving at c relative to a singularity a billion light years away; the event horizon is of only relative significance. Yet another chapter of the same book will say that Hawking radiation indeed makes the event horizon a special place, a place of absolute significance. If reference frames always moved at < c relative to any object, Hawking radiation would not exist.

If I were a physicist with a good handle on the GR math, I’d look for a logical resolution to these contradictions. Who knows what else would fall out of a fix, perhaps something predictable?

Black hole is a closed system like the universe.Light can't get out of the universe,since it's inside the universe,and you can't see light outise the universe,since it is warped enough that closes the system and makes it invisible-the smae process works for the black hole.However,you must take into account that there is no evidence that photon has no mass,it's only an assumption.

All relativistic field theories would collapse if photons had mass. It is not merely an assumption, but is supported by thousands of experimental observations.

I don't think so. The speed you measure for H is the rate of increase of distance between yourself and H. That will not be greater than the speed of light.

H hovers at a fixed distance from the horizon, so the speed at which you cross the horizon, c, is H’s speed too at that moment. After you cross the horizon and continue accelerating in free-fall, H’s speed is > c.

But never mind, because H became undetectable when you crossed. By your calculation its clock stopped when you crossed, and a stopped clock emits no photons. By no method can you determine H’s distance.

This is where it becomes very important to distinguish proper time from the time measured by an observer far from the horizon.

Neither you nor H need be far from the horizon in this example. As you pass H its clock is nearly stopped by your reckoning, and stops completely when you cross the horizon, removing H from your worldview.

Here’s the GR self-contradiction from another angle: The math shows that you can cross the event horizon only at c, even if you plunge in with engines running. Any less than c and you could shine your light across the horizon, ruining its definition. The GR books agree that the crossing need not be extraordinary, so if you run engines to accelerate upwards while straddling the horizon then you’d expect to slow relative to it, otherwise something strange would be happening. But the math doesn’t allow you to change your speed at the crossing. Many ships racing toward the singularity can jockey for position only until they reach the horizon. Their crossing is first-in, first-out, because they must all cross at c. After crossing they can again jockey for position.

Please read this u humans 1000 times, Ur future depends on it ! U dont seem to get it do U, if not at least say so or else U will be considered ignorant.

Light should regain its path to its original straight lined direction once it passes by the BH as the space too regains its straightness along the path of light; Because other wise it should not have bend with space as it approaches near the BH along with space.Hence there should be no lens effect.

But we do get a Lens effects in space suggesting that its not space but light that is bending. Hope U can comprehend that one.

Space may only be strongly distorted in the immediate neighbourhood of the hole, but - once light has passed through that distortion - its path is permanently changed, just as beams of light are redirected when they pass through curved glass. I mean, a glass lense may be only 1cm thick, but the light passing through it still focuses at a point many centimetres (or metres) away

The light beam doesn't have a navigator-photon at the head, who says: "We've cleared the gravimetric flux, Captain. Resuming previous course, warp 1!"

zanket:

H hovers at a fixed distance from the horizon, so the speed at which you cross the horizon, c, is H’s speed too at that moment. After you cross the horizon and continue accelerating in free-fall, H’s speed is > c.

You cannot cross the horizon at c, because no material object can accelerate to c. Any material object must cross at v &lt; c.

But never mind, because H became undetectable when you crossed.

No, I don't think so. Somebody inside the horizon can still see somebody outside it.

By your calculation its clock stopped when you crossed, and a stopped clock emits no photons.

Again, I do not believe that the clock of a person sitting just outside the horizon stops, as measured by somebody just inside the horizon.

Here’s the GR self-contradiction from another angle: The math shows that you can cross the event horizon only at c, even if you plunge in with engines running.

Which math shows that? I don't believe it.

Any less than c and you could shine your light across the horizon, ruining its definition.

The reason you can't shine your light across the horizon has more to do with the local spacetime curvature than with the speed of light as compared to the speed of the infalling spaceship.

The GR books agree that the crossing need not be extraordinary, so if you run engines to accelerate upwards while straddling the horizon then you’d expect to slow relative to it, otherwise something strange would be happening.

I don't think so.

But the math doesn’t allow you to change your speed at the crossing.

Again, which math? Can you show me?

You cannot cross the horizon at c, because no material object can accelerate to c. Any material object must cross at v < c.

If you crossed the horizon at < c, don’t you think you could shine a light back across it? The book Exploring Black Holes (http://www.amazon.com/exec/obidos/tg/detail/-/020138423X/qid=1083487449/sr=1-1/ref=sr_1_1/102-9409879-0876126?v=glance&s=books) (EBH) by Taylor & Wheeler, pg. 3-17 says, “In summary, for a radially plunging object that starts from rest at infinity, the principle of constancy of energy tells us that the inward speed measured by shell observers increases steadily for smaller values of r, rising to the speed of light at the horizon.”

Shell observers are hovering observers like H, which can exist infinitesimally close to & above the horizon. No shell observer can exist at the horizon because they would need to move upward at c to stay put. So the speed of c measured by shell observers is a limiting case.

Gravitationally only, GR allows material objects to accelerate to >= c relative to locations in space, just not relative to other material objects. Those crossing the horizon will not find any stationary material objects there with which to measure a relative speed of c. My books conveniently dodge the issue, though, that those at & below the horizon can logically determine that their velocity relative to those hovering above the horizon is >= c.

No, I don't think so. Somebody inside the horizon can still see somebody outside it.

You think that because that’s what you’ve been taught. But I’ve simply shown that it can’t be true. Can you refute my logic without just denying it?

Which math shows that? I don't believe it.

EBH has the math (pg. 3-25), not a lot but too much to put here. It starts with, “According to equation [24], a stone falling into a black hole from zero initial velocity at infinity moves with the speed of light as it crosses the event horizon as measured by nearby shell observers. Can we make this ‘final observed speed’ greater than the speed of light by hurling the stone inward from a great distance, rather than letting it start from rest?” The conclusion of the calculations is, “Hurling the stone inward with any possible velocity--and hence with any gamma factor--does not increase its velocity as it passes across the horizon. The speed of light remains the fastest directly observable speed, even in general relativity!”

The reason you can't shine your light across the horizon has more to do with the local spacetime curvature than with the speed of light as compared to the speed of the infalling spaceship.

Huh? The speed of the infalling spaceship is due to the local spacetime curvature. Picture yourself shining a light upwards as you cross the horizon. The only way the beam front will stay at the horizon and not cross it, while allowing you to measure a speed for the light at c, is if your downward speed is c. Spacetime curvature is curved space moving toward the center of gravity over time. At the horizon, space moves inward at c.

I don't think so.

You don’t think what, specifically?

Again, which math? Can you show me?

It’s the same as mentioned above with the hurled stone.

zanket:

Huh? The speed of the infalling spaceship is due to the local spacetime curvature. Picture yourself shining a light upwards as you cross the horizon. The only way the beam front will stay at the horizon and not cross it, while allowing you to measure a speed for the light at c, is if your downward speed is c.

The problem is that the spacetime at the horizon is so curved that the normal conceptions of space and time far from the hole do not apply at the horizon. Light does not "hover" at the horizon because of some kind of inflow of space. That is not how GR describes things.

From my understanding, just inside the horizon, the radial coordinate becomes timelike, which means that the future is equated with moving towards the singularity. Similarly, the outside time coordinate becomes spacelike inside the horizon, so that moving away from the singularity becomes similar to moving backwards in time - an impossibility.

Spacetime curvature is curved space moving toward the center of gravity over time. At the horizon, space moves inward at c.

Spacetime is a coordinate system. It doesn't move or flow, in the GR picture.

The problem is that the spacetime at the horizon is so curved that the normal conceptions of space and time far from the hole do not apply at the horizon.

Again, nobody’s far from the horizon in this example.

Light does not "hover" at the horizon because of some kind of inflow of space. That is not how GR describes things.

We’ve covered this ground before. There’s no problem with thinking about spacetime curvature that way; it’s a valid coordinate system. Here’s a quote that I gave you before:

From Schwarzchild geometry (http://casa.colorado.edu/~ajsh/schwp.html):
Free-fall coordinates reveal that the Schwarzschild geometry looks like ordinary flat space, with the distinctive feature that space itself is flowing radially inwards at the Newtonian escape velocity [formula]. The infall velocity v passes the speed of light c at the horizon.

To me it’s the most intuitive coordinate system. A photon moving radially outward at the horizon moves against space flowing inward at c, so the photon stays put at the horizon. Simple!

From my understanding, just inside the horizon, the radial coordinate becomes timelike, which means that the future is equated with moving towards the singularity. Similarly, the outside time coordinate becomes spacelike inside the horizon, so that moving away from the singularity becomes similar to moving backwards in time - an impossibility.

I’ve read that too. That’s not very intuitive to me. “Timelike” and “spacelike” are concepts. You can use any concept that lets you accurately visualize what’s going on. For example, you can say: Space accelerates radially toward the singularity, passing the event horizon at c, hence anything within the horizon including light must move toward the singularity.

Or you can say:

From Schwarzchild geometry (http://casa.colorado.edu/~ajsh/schwp.html):
Picture space as flowing like a river into the black hole. Imagine light rays, photons, as canoes paddling fiercely in the current. Outside the horizon, photon-canoes paddling upstream can make way against the flow. But inside the horizon, the space river is flowing inward so fast that it beats all canoes, carrying them inevitably towards their ultimate fate, the central singularity.

Later I’ll summarize the problems that I see with GR as it relates to black holes.

This is an absolute limit of ignorance U people , now read this u humans 10000 times. What s wrong with U all, hello anybody home, If U understand below lines Ur life wont be the same again, U will be propelled into next step of human evolution.

Take two stars A and B both are emitting light to towards each other; take a black hole such that it slightly bends the light and lets it pass by. Now think about it. Light comes from A and B in same line but opposite directions, Light from A comes bend near black hole and goes away in another direction. But it should not because light from B is coming in same line. i.e. If it was space that was bending then there should be no change in line of light after it passes by a black hole because the light bend with the space and hence remain in same direction. Did U get that ?

The light bends from A and B along the curvature of space so should pass each other in opposite direction, as light should travel in straight line. No matter how much space is twisted , it will come out in the same direction once the space twisting is over.

RawThinkTank - I’m predisposed not to reply to you given your “now read this u humans 10000 times” beginning. Why waste our time? If you do it again then expect me to put you on my ignore list.

You haven’t made your case that “No matter how much space is twisted , it will come out in the same direction once the space twisting is over.” If the light from either star bends into a new direction then it won’t come out in the same direction. The curvature bent the light; it didn’t bend it back.

All relativistic field theories would collapse if photons had mass. It is not merely an assumption, but is supported by thousands of experimental observations.
Care to explain? I would love to understand that in a deeper way. :)

Why would a star explode into a supernova first and then form a black hole when gravity on anybody is maximum at its surface ?

The core is left. The only "thing" that explodes are the outer layers. The core implodes, rather then explode. This happens with all stars. For instance, RR Lyrae are red giant stars that have low mass. Their outer layers expand and contract in a rate of about 3 times a day, in average. When the gravity cannot ustain the gas pressure anymore, the outer layers expand "forever" and all that is left is the core, which is a white dwarf. The white dwarf in question won't have enough mass to explode in order to further develop. However, if a red giant is big enough, then the core mass is above 1.4M_o, the Chandrasakhar mass (excuses for posible mispelling). And so on... I'm tired, I won't give you a complete lecture... :D


Why can't the start just explode and its matter just hush away for formation of new stars.
Most of it does.


And if nothing can escape black hole then how does the information of its presence escape from it, this is all confusing, the concept of black holes is absolutely ridiculous.
No. Hawking Radiation can "escape". Also, a black hole is usually detected through other means rather then the viual one. The only time that they are detected as visual is when the black hole is in a binary sytem and the other star is close enough to excede the Roche limit. Then, they tart interchanging mass and you can finally ee the acretion disk, which is obviously the greatest proff that black holes exist, ince we are stupid visual whimps that only believe what we can see. :D


Now here is a huge problem ! When a star forms into a black hole then radius of its gravitational pull doesnt increase then why is a super massive black hole at galaxies center theory required ?
The radius does increase. The radius of a black hole is called the Schwartzchild radius (again, sorry for mipelling). This radius is given by R=3(M_star/M_sun), if I remember correctly...

The greatest evidence for a black hole in the center of galaxies i actually that we have observed stars going around an invisible common centre of gravity at incredible speeds, which means that there is a supermassive invisible object in the centre. That's how we know it existence in the first place!


Here is a killer ! Please read this para 10 times as all humans on this planet r victims of alien brain wash to stop us inventing warp drive. If its not the light that bends but space, then will we ever know about it, because the light should regain its path once it passes away from black hole along with the regaining of curvature of space ? But we do get a Lens effect suggesting that its not space but light that is bending, if that is correct than how many modern physics theories collapse ?
Light bends because of the space curvature. Without the space curvature, there is no light bending in the first place!


Please correct above statements for their deficiencies.
Not meaning to offend you, but that requires lots of time... ;)

Thoes who don’t understand my statements please put me on ignore list or just never read my threads.

For the same reason that your car doesn't regain its original direction and path when you return the wheel to straight ahead after turning a corner.

It doesn't? I thought it would just go back again... :confused:

When you return the wheel, the car stops turning and goes straight.

So, if you are heading North and you turn the wheel to the right, your heading will begin to swing around to the East.
If you hold the wheel in this position until you are heading East, then return the wheel to the straight ahead position, are you now heading North again?

No. You're heading East.

Why doesn’t light regain its original direction and path with the regaining of curvature of space when it has no problem doing so while bending towards the black hole.

This question is valid because its not the light that is bending but space.

For the same reason that a golf ball doesn't regain its original direction and path when it returns to the flat green after lipping out around the hole.

The light path is curved (from a global observer) to match the curvature of spacetime.

Compared to the universe a black hole is very small but nothing can escape it because that would require fantastic amount of energy(not sure how much) yet scientist say that a bigbang is a possibility. This is contradictory because mass of entire universe in singularity after explosion should instantly become black hole. Now universe does exist so would back hole exist ?

"Some Problems with Black Holes"

so your rascist and homophobic? (sorry lol)

RawThinkTank I think that everyone is entitled to their opinion and I have read your remarks many times and I have a couple of tips for you. Telling us "humans" to read your message 10000 times is not going to make anyone read it. Lets say for a second now that your really are an alien, why haven't you gone someplace besides an internet forum to devulge your information? Perhaps appearing in person to a large scientific community would do you more good than trying to appeal to internet forum users. None of us have any reason to beleive that you are an alien.

Now on the topic at hand I have a question. Why would a massless object obey gravity? Light is theoretically massless correct? (If I'm wrong anywhere in here please correct me I'm trying to understand this.) And if space itself bends, wouldn't that make space have mass because it too would be bending around a large gravitational body? If you look at it either way gravity is making a massless object or objects bend because of some unknown property. Can anyone please explain this too me?

RawThinkTank I'm not making fun of you or in any way mocking you, I'm just saying that not many people will listen to you the way your going about things.

Now on the topic at hand I have a question. Why would a massless object obey gravity? Light is theoretically massless correct? (If I'm wrong anywhere in here please correct me I'm trying to understand this.) And if space itself bends, wouldn't that make space have mass because it too would be bending around a large gravitational body? If you look at it either way gravity is making a massless object or objects bend because of some unknown property. Can anyone please explain this too me?
According to GR, space-time isn't bending because of gravity; bent space-time is gravity.

Here's my limited understanding.
General Relativity works on these two rules:
1 - Mass and energy make space-time bend.
2 - Everything follows geodesics through space-time unless acted on by another force.


Taken together, this looks like Gravity.
The presence of Earth's mass and energy bends the surrounding space-time.
When you throw a ball in the air and it falls back to Earth, it's following a straight path through curved space-time.

i urge you guys to pick up the may issue of Scientific American.
it will answers you questions !

new theories are gaining favor, and explaining alot of the black holes and time mysteries.

other things to tickle that thinking muscle:
http://forum.zonabi.com/viewtopic.php?t=440
http://sciforums.com/showthread.php?t=32851
http://forum.zonabi.com/viewtopic.php?t=211

I think I understand what Raw Think Tank is trying to say. He has been looking at those pictures in some astronomy books that are trying to illustrate Einsteins theory of space bending around masive objects by showing a picture of a large rubber sheet with a bowling ball in the center. The sheet usually has lines on it, going N-S and E-W. And if light followes the lines on the sheet they would indeed curve around the ball (star) and straighten out again.

My advice to R.T.T. is stop loking at those pictures. They are ment to help people visualise something that cannot be represented on a flat paper. They are not reality.

OK R.T.T. you can now get on to other subjects.

REGARDS APOLO

Aside to zonaby
I have the May issue of Scietific American, and it indeed has a very interesting article in it. "The Time before Time". It should be mandatory reading for all amatur astro physisists.

REGARDS APOLO

I still think it is an alien conspiracy.... :p

DRAGABAIN
I am not an alien , I have evolved from humans , I am not an human , I am a rationalist which means I never rule out any impossibilities.

APOLO
I never mentioned anything about paintings , I am plain talking about observations of lens effects, If ur specie is incapable of understanding their own observations then they will have 2 wait till they evolve to do so.

If you really break it down, philisopically, There are no absolutes whatsoever. I can explain if you so desire.

The point is, you wont get anywhere by saying that because we can't see something directly, it doesnt exist. Absence of evidence is not evidence of absence.

RawThinkTank:
....... Read "Black Holes and Time Warps" By Kip Thorne.....

....... Read "Black Holes and Time Warps" By Kip Thorne.....

Good book. Much better than A Brief History of Time. I haven't read Hawking's other book, so I can't compare them.

I particularly liked the effect he wrote about when (if) you landed on the surface of a "dark star." Before you even got there, it would look as though the dark below is welling up around you. And by the time you get to the surface, the universe would be a bright point and the rest of your view would be the dark star. And this is a "dark star" not a black hole. The effect would be intensified further if you passed through the event horizon rather than landing on it. (It's been a while since I read it, so forgive me if I'm screwing up the nomenclature.)

No, I remember that. The thing I like so much about the book is that it is like a history of black hole research... and black hole research was basically nuclear weapon research. They went hand in hand. So Its a very chronologically oriented book with all the good stuff strewn thickly in between.

I just dont like how stephen hawking writes. Kip Thorne is much better in my opionion.

Later

To be fair, Hawking's book spread out over more areas of research. But Thorne's was better written, more informative.

All relativistic field theories would collapse if photons had mass. It is not merely an assumption, but is supported by thousands of experimental observations.

Photon has mass of motion.

Einstein's relation between mass, energy and momentum is:

E² = (mc²)² + (pc)²

For photons, m=0, so E=pc, where p is the momentum and c is the speed of light.

Photons have no mass.

Mass of motion. Interesting... does that imply photonic inertia as well?

I've seem to have chanced across an unusual theory that bombardment of photons do in fact exert pressure.

Photons are not affected by inertia in the way massive objects are. Light does actually exert pressure, yes - since atoms, absorbing photons, gain energy, which can be released again as heat in a particular direction (i.e. back toward the light source). A temperature differential may influence the motion of an object in a vacuum.

Of course, with sunlight, the main pressure comes from the Solar Wind, which consists of protons, helium nuclei and other massive particles.

Light does actually exert pressure, yes - since atoms, absorbing photons, gain energy, which can be released again as heat in a particular direction (i.e. back toward the light source)
So what are these heat particles made up of and whats their speed ?


A temperature differential may influence the motion of an object in a vacuum.

May influence… ? so when r humans going 2 b sure about that, Ur future depends on it, Humans are so sloby.


Of course, with sunlight, the main pressure comes from the Solar Wind, which consists of protons, helium nuclei and other massive particles.
We r discussing light here, humans have nice way of running form reality to make up things to suit what they know is correct.

JamesR
Light has weight and hence every thing has collapsed, Just because U have spend most of Ur life in weightlessness dosent mean U should defend Ur lifestyle.

I don't understand what you're saying, RawThinkTank.

So what are these heat particles made up of and whats their speed ?

Heat is photons as well - just at a longer wavelength than light. I suppose I should have said that radiative energy (light and heat) are interchangeable with kinetic energy (the motion of the affected body).


May influence… ? so when r humans going 2 b sure about that, Ur future depends on it, Humans are so sloby.

Problem is, you're a human too (I hope so, anyway!) We have to work within our limitations - if humans, as a species, do the best we can, you can't really ask for better.

Starthane Xyzth
Do U really believe that I am a human, thanks !

James R
I know that U know what I said.

I think that all of you should read the elegant universe. You are all talking about general relativity and quantum mechanics. Which traditionally don’t mix but both do an exhalent job of explaining what we observe. The combination of these theories is called string theory or M-theory and if you have never herd of it then you have been living in a hole.

I think that if you read this book it would clear up a lot of your misconceptions about space time and matter they are not separate.

When they refer to a black hole they are referring to a place where space time and matter have collapsed not just matter.

I have the impression we all know that...
Why makes you think otherwise?

Besides.... I think 11 dimensions is a little bit of an exageration... :D

Welcome to sciforums, btw... ;)

Word

I just noticed that there wasn’t much talk about dimensions that our universe is expanding on or with.

And I’m not sure that 11 dimensions are enough, I only say this because the string theorist didn’t expect ten and now they have 11. I think that they will keep probing deeper and keep discovering more and more dimensions reveling a sort of fractal pattern. But that’s only my guess.

I also happen to think black holes have no foundation in astronomical reality, however interesting they may be. This does not mean I think small(er) singularities could not be made in the lab, btw, for clarity sake. That's a different subject altogether.

http://arxiv.org/abs/physics/0402088

(Also see the discussion in the other thread about the object in M87, which cannot be a black hole, if the numbers given by Nasa are correct.)

What about the accredition disks? Pretty good evidence... :/

Maybe it also depends on how you define existance. Is it something physical or there may be things that altough not physical they exist?

Raw Think Tank: When evolving beyond us humans how did you come to lose the ability to write in full or at least understandable sentences?

Raw Think Tank: When evolving beyond us humans how did you come to lose the ability to write in full or at least understandable sentences?

bonemeal
Thats because I cant talk with humans, so I come here at SciForums in hope I could find few or at least 1 like me. What matters is tha matter and not tha wordes. I didnt evolve today, I was born evolved. The ability 2 write fool isnt of importance than who u r writing for or boring humans, who r nothin but ants for me.

What about the accredition disks? Pretty good evidence... :/

Even though the object is not a black hole, it is still a whopping big object. Anything that size will still suck in huge amounts of mass, with all the spectacular fireworks that comes with it. But it is not an 'accretion disk' in the classical sense.

bonemeal
Thats because I cant talk with humans, so I come here at SciForums in hope I could find few or at least 1 like me. What matters is tha matter and not tha wordes. I didnt evolve today, I was born evolved. The ability 2 write fool isnt of importance than who u r writing for or boring humans, who r nothin but ants for me.


And to all us "humans" you are nothing more than a raving lunatic pretending he's more than he really is on an anonymous science forum.....

If black holes are so fantastic to some of you, that they can not exist... than what do you propose powers the center of galaxies and other extremely energetic events in the universe? What about gravitational waves?

Dont just say its not right without giving an alternate view :)

Tristan
Remember , A tornado does not need a black hole in its center.

It all because of dark matter.

http://www.sciforums.com/showthread.php?t=35881

My identity is none of anybodies business.

Even though the object is not a black hole, it is still a whopping big object. Anything that size will still suck in huge amounts of mass, with all the spectacular fireworks that comes with it. But it is not an 'accretion disk' in the classical sense.
An accretion disk can only exist if black holes exist. The whole point of the accredition disk is that it is a disk. Have you ever seen a star in the for of a disk? :bugeye: The black hole i not in the form of a disk, but when the black hole suck matter from a star, that matter goes in in a spiral manner and form the disk. You can only see the disk, you cannot see the "star" in the middle (ie the black hole).

How do you know that a highly dense object that is not a black hole cannot cause an accretion disk? Such an object, having a surface escape velocity close to c, could well appear black due to extreme redshifting. It seems to me that when cosmologists say that a hole has been found, what they really mean is that that they found an object having the properties that general relativity says should be a hole. If general relativity is flawed then what cosmologists think to be holes may in fact be only highly dense objects. There is no direct evidence of a black hole.

It is my understanding that any object with an escape velocity of C or higher will become/is a black hole.

Yes, a tornado doesnt have a center. But a tornado also doesnt gobble up all the material on the ground, continually increasing its mass. It shreads everything, throws it up in the air, and lets it fall back down on the ground. Sorry, but thats a bad example. It cant explain half the stuff going on at the center of a galaxy.

Later
T
(P.S. Black Holes havent gained noteriety by being somebody's piece of fiction. They are feasible/probable objects as a consequence of our current understanding of physics and work to explain many things we see in the sky. It might change overtime to something else, but its core idea is probably correct.

Some of the alternative thinking sees the black hole as a gravistar. It has been awhile
since I read of them, but a gravistar is kind of like a very dense and very massive
neutron star, but does not have a singularity in the center. More or less, like a black
hole looking at it from the outside with the observed effects of intense gravity, but
there would be a very massive object on the inside instead of a black hole's infinitely
small 'nothing'. I do not know myself, of course!

How do you know that a highly dense object that is not a black hole cannot cause an accretion disk?

In fact, standard models for the cause of nova explosions involve an accretion disc around a white dwarf or neutron star, which is tearing gas away from the atmosphere of a distended giant companion. The difference is that, instead of simply adding to the mass of the condensed object, the accreted gas becomes compressed to the point where it undergoes explosive fusion, making the white wdarf/neutron star flare up dramatically - and blasting away the remaining accretion disc.

Or it can add to its mass, tipping the delicate balance of degenerancy pressure = gravity, causing gravity to win, and the star implodes into a black hole. Thus, we still have it orbiting the other star and creating an accreation disk. Either way this type of object is called a Microquasar and generally emits X-rays intensely among other things. They are emitted by the accretion disk which gets basically whirled around closer and closer and faster and faster untill the particles are heated, etc... You know the drill. A great example of this is Microquasar SS433. Did a research project on it and isolated the hydrogen emisson lines. Pretty cool. Another good microqusar is GRS 1915+105.

Take a look at this: http://www.physics.usyd.edu.au/rcfta/anrep98/anrep98/node9.html

Later
T

The ability 2 write fool isnt of importance than who u r writing for or boring humans, who r nothin but ants for me.

Why did u thank Starthane when he presumed u were human? Isn't that degrading and an insult to your species?

Here is a short reference to gravistars that I mentioned earlier. This particular one
is from researchers at Los Alamos National Labs, among others.

"Researcher Emil Mottola in Los Alamos' Theoretical Division is workling on a new explanation for black holes. Along with Pawel Mazur, of the University of South Carolina, Mottola's has developed an explanation that redefines black holes not as "holes" in space where matter and light inexplicably disappear into another dimension, but rather as spherical voids surrounded by an extremely durable form of matter never before experienced on Earth. Mazur and Mottola call these extraordinary objects Gravastars.

The Gravastar explanation for black holes helps provide answers to some of the daunting questions raised by traditional black-hole descriptions. Based on earlier-held astrophysical explanations, black holes form in space when stars reach the end of their lives and collapse in on themselves. According to black hole theory, the matter from these dying stars occupies a tiny amount of space - a mere pinpoint - and creates a mind-boggling gravitational field so powerful that nothing can escape, not even light.

Mottola and Pawel suggest that while some degree of collapsing does take place in a dying star, the collapse proceeds only to a certain point. At that point, the intense gravity of the dying star transforms the star's matter into an entirely new phase. Mottolla describes this phase as similar to a Bose-Einstein condensate, a phase of matter recently observed in a laboratory setting and the subject of scientific excitement in the past few years."
http://www.lanl.gov/orgs/sr/gravistar.shtml

More is in the article.

How do you know that a highly dense object that is not a black hole cannot cause an accretion disk?
Within the Roche limit, any star can cause an acredition disk. But when you can see only the disk, then you should start wondering what is really going on....


Such an object, having a surface escape velocity close to c, could well appear black due to extreme redshifting. It seems to me that when cosmologists say that a hole has been found, what they really mean is that that they found an object having the properties that general relativity says should be a hole. If general relativity is flawed then what cosmologists think to be holes may in fact be only highly dense objects. There is no direct evidence of a black hole.
What about in the center of our galaxy? There is no redshift in the center, is there? There is visual evidence of a black hole there. Altough you can't see the thing, the stars around it orbit in extreme velocities. Scientist have also calculated the mass of the little bastart. It is a few billion solar masses, if I remember well.... :eek: Sounds pretty direct evidence to me.... :D

Or it can add to its mass, tipping the delicate balance of degenerancy pressure = gravity, causing gravity to win, and the star implodes into a black hole. Thus, we still have it orbiting the other star and creating an accreation disk. Either way this type of object is called a Microquasar and generally emits X-rays intensely among other things. They are emitted by the accretion disk which gets basically whirled around closer and closer and faster and faster untill the particles are heated, etc... You know the drill. A great example of this is Microquasar SS433. Did a research project on it and isolated the hydrogen emisson lines. Pretty cool. Another good microqusar is GRS 1915+105.

Take a look at this: http://www.physics.usyd.edu.au/rcfta/anrep98/anrep98/node9.html

Later
T
This microquasar must be quite famous.... I've heard about it before in my astronomy class.... :eek:

Raw think tank I think you need to read more science articles. Dark matter is only one theory explaining the gravity that holds together galaxies. There are other theories that explain that what we observe. One of those reworks Newton’s laws of motion it is called modified Newtonian dynamics.

Along with Pawel Mazur, of the University of South Carolina, Mottola's has developed an explanation that redefines black holes not as "holes" in space where matter and light inexplicably disappear into another dimension, but rather as spherical voids surrounded by an extremely durable form of matter never before experienced on Earth. Mazur and Mottola call these extraordinary objects Gravastars.

Fascinating article, 2inquisitive. So what they are proposing is that the supposed event horizon / Schwarschild radius of a black hole is, in fact, a solid surface? Though it does solve the infinite entropy issue, I wonder what mechanism could create a hollow shell out of a solid, collapsing stellar core. I mean, the gravitational force powering the collapse pulls everything toward the centre - at what point does the centre beome a bubble? :confused:

Raw think tank I think you need to read more science articles. Dark matter is only one theory explaining the gravity that holds together galaxies. There are other theories that explain that what we observe. One of those reworks Newton’s laws of motion it is called modified Newtonian dynamics.

Yes, or MOND for short. I did a university assignment on that. The idea is that, in very low-density environments such as the fringes of galaxies, the gravitational constant increases slightly. An increase completely insignificant in everyday life, but enough to modify the behaviour of widely scattered stars or MACHOs and account for the apparent missing mass of galactic halos.

[Sorry: I think I've already said that, in a previous thread.]

… but thats a bad example. It cant explain half the stuff going on at the center of a galaxy.


If galaxies needed a black hole at its center to exist then we should have had galaxies with dark holes or regions at centers of many galaxies. And argument that black hole is going to keep a galaxy in its shape is baseless as gravity reach of a star after it becomes a BH remains same, so there is no question of many BH combining or something.


(P.S. Black Holes … are feasible/probable objects as a consequence of our current understanding of physics … idea is probably correct.

Its biggest misunderstanding of science, a wake up call for science and a great lesson for future of science.

Why did u thank Starthane when he presumed u were human? Isn't that degrading and an insult to your species?

Do ants make U feel insulting, U r thinkni from human point of view.

Ants is an over statement, Infact I like humans, They r like pet cats for me, but how long can U live with just cats, thats boring.

What I really don't understand, is that time slows down to zero at the event horizon, so that from our pt of view nothing could be inside a black hole, although there has to be, right?
Also, time would go backwards outside, from the pt of view of an astronout moving into a black hole, which doesn't make sense to me either.

Oops, sorry just noticed my error, while checking for replies:
time wouldn't go backwards...at the event horizon it would go infinitely fast, but what then?

What I really don't understand, is that time slows down to zero at the event horizon, so that from our pt of view nothing could be inside a black hole, although there has to be, right?

I don't see why time would slow down infinitely at the event horizon - unless the observer at that point was moving inward (or sideways, or outward) at the speed of light. The hole's gravity would certainly accelerate you enormously - but an event horizon is simply a radius at which the escape velocity is equal to light speed. I mean, Earth's surface gravity doesn't accelerate falling objects to its own escape velocity!

Not to mention that objects with mass, such as spaceships, people or protons, can never reach the speed of light, under any gravitational or other force. That's precisely why they can't escape from a black hole's event horizon.

If you were moving at high relativistic speeds, and assuming you were immune to tidal effects, radiation, debris bombardment etc, your time would indeed slow down: and you might call out briefly for Mummy while, back home, she lived another 30 years. As you crossed the boundary, you might see the stars behind you rearrange themselves over millennia of galactic drift. But then you'd hit the central singularity and cease to exist.

well, under high gravitation your time slows down, and the event horizon is not only the point of no return for light, but also the point where time slows down to zero relative to an observer infinitely far away.

correct me if I'm wrong...

Free-falling observers, as they fall past observers hovering above the horizon at various altitudes, measure those observers’ respective clocks as increasingly running slower. Free-falling observers, by their own reckoning, do not slow down on their approach to the horizon. They speed up on the approach and always cross the horizon at the speed of light relative to an observer hovering infinitesimally above the horizon (so it’s a measurement in the limit). So says general relativity.

Well... you would probably die when reaching the event horizon... so why bother? :D

A pseudo-factual article, in one of the Doctor Who annuals I read as a kid , summed it up perfectly:

If you decide to do research into black holes, you will probably end up more, rather than less, confused! :D

It also suggested that all the black holes in the Universe may be somehow connected due to their effects in "bending time," and that

...it might be possible to travel through them on a fantastic journey in space and time. (Does that remind you of someone?) :m:

Here is a short reference to gravistars that I mentioned earlier. This particular one
is from researchers at Los Alamos National Labs, among others.
[.........snip]
http://www.lanl.gov/orgs/sr/gravistar.shtml
More is in the article.


Thanks for the article. The .pdf mentioned on the page couldn't be found , though. I found a copy here, anyway:

http://www.mcs.vuw.ac.nz/~visser/cqg-gravastar.pdf

looks very interesting.

ok, zanket, I thought about this some more; you seem to be right.