Black hole being 4d object?

Discussion of theories involving time as a dimension, time travel, relativity, branes, and so on, usually applying to the "real" universe which we live in.

Postby Gilles » Mon Feb 13, 2006 10:35 pm

Hey Guys!

I'm bad at calculating, but apparently some dude just found out mathematically that our universe may be a 5d black hole.

Maybe that's where our communication went wrong a year ago :wink:

Jinydu, you might want to restart your black hole calculations at the 5-d level, and maybe you'll understand that life is not only possible, but allso present in black holes

Toodels,

Ps, by the way, here's a nice link

http://www.newscientist.com/home.ns
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Postby moonlord » Tue Feb 14, 2006 6:13 pm

I don't think life can exist on a black hole.

1. They are 3D objects: in this case, calculus and observations show they have no volume. Therefore, life cannot exist on their surface. Because the gravitational force pulls light back, life cannot exist in its surroundings either.

2. They are 4D or 5D objects: in this case, a 3D slice of it is a sphere. This slice has been calculated and observed not to have volume. This means all of them just 'touch' our realm. What is the probability that ALL of the black holes in the universe are tangent to our realm? I think we may consider it zero.
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Postby Gilles » Wed Feb 15, 2006 9:10 pm

Unless that's what they are..
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Postby thigle » Wed Feb 15, 2006 11:03 pm

What is the probability that ALL of the black holes in the universe are tangent to our realm? I think we may consider it zero.

how come ? is that so improbable ?
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Postby moonlord » Thu Feb 16, 2006 5:24 pm

It depends afterall on what do you consider to be the probability of a single black hole touching our realm. There are infinite more possibilities of it intersection our realm to a non-zero-volumic body. Therefore, the possibility we're considering tends to zero. The probability of all black holes toughing our realm is even smaller.

NOTE: I'm not sure with the meaning of 'tends to zero'. I meant lim p = 0.
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Postby jinydu » Sat Feb 18, 2006 10:25 pm

Gilles wrote:Hey Guys!

I'm bad at calculating, but apparently some dude just found out mathematically that our universe may be a 5d black hole.

Maybe that's where our communication went wrong a year ago :wink:

Jinydu, you might want to restart your black hole calculations at the 5-d level, and maybe you'll understand that life is not only possible, but allso present in black holes

Toodels,

Ps, by the way, here's a nice link

http://www.newscientist.com/home.ns


That link points to the main page of a magazine. Needless to say, it has long since been updated and the article you're thinking about is no longer on the page. Here is what I think you had in mind:

http://www.newscientist.com/channel/fun ... -hole.html

In fact, I haven't made any black hole calculations. Those require general relativity, which I haven't learned yet.
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Postby Hugh » Sun Feb 19, 2006 1:58 am

Here is another link to check out which talks about 5d black holes:

http://www.euclideanrelativity.com/idea/index.htm
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Postby PWrong » Sun Feb 19, 2006 3:51 pm

The article isn't really about finding life in black holes. That's just to get your attention. It's really about the fact that 5D black holes have nice mathematical properties, and that our universe itself might be a 5D black hole. That doesn't mean there is any other kind of life inside a black hole. Incidentally, the article includes time as a dimension, so it's really only a 4D black hole.
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Postby AlienBilly » Thu Feb 23, 2006 12:00 pm

A black hole is (as far as sience suspect) formed when a huge star collapses under it's own gravitational force and so forming a quantum mechanical singuarity, this works very well with the Lorentz-transformation.. (m=m0/sqrt(1-(v/c)²)) as so, it has an infinite mass and a volume of zero, as the gravity pulls at the speed of light.
And having a volume of zero makes it mathematicly have zero dimentions as it's not stretched either in lenth, width och depth.
That's why the description of something approacing a black-hole is this:
First there is gravity pulling you towards the superdense object (because of it's mass that's curving the space around it), then you're getting pulled thinner and thinner (this is relativly, so you wont notice it), until your're one dimentional, the next thing is that you enter the event-horizon where you become energy, that's according to the special theory of relativity (E=mc2) ..

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Postby bo198214 » Thu Feb 23, 2006 10:43 pm

AlienBilly wrote:it has an infinite mass and a volume of zero

Thats nonsense. A black hole has only a mass big enough and radius small enough that the escape speed is superluminal. The escape speed is the speed a body needs to leave the orbit. Its computed by
v=sqrt(2 gamma M/r)
The so called Schwarzschild-radius is the radius for a given mass M such that the escape velocity at that radius is light speed. So we can get it simply from the above formula:
r=2 gamma M / c<sup>2</sup>

For example the Schwarzschild-radius of our sun is 2.95 km. That means if the sun becomes smaller than 2.95 km then its a black hole.
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Postby AlienBilly » Fri Feb 24, 2006 3:37 am

bo198214 wrote:Thats nonsense. A black hole has only a mass big enough and radius small enough that the escape speed is superluminal. The escape speed is the speed a body needs to leave the orbit. Its computed by
v=sqrt(2 gamma M/r)
The so called Schwarzschild-radius is the radius for a given mass M such that the escape velocity at that radius is light speed. So we can get it simply from the above formula:
r=2 gamma M / c<sup>2</sup>

For example the Schwarzschild-radius of our sun is 2.95 km. That means if the sun becomes smaller than 2.95 km then its a black hole.


I will take that as a fact if you can explain this:
The gravitaional pull can not exceed the speed of light, as it's a constant.
And as layed down here the escape velocity of light is naturally the speed of light.
For an object or particle to travel at or pull at the speed of light it would requier infine energy, how can an object without infinite mass have infinite energy ?
Wouldent that contradict the formula E=mc<sup>2</sup> ?
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Postby bo198214 » Fri Feb 24, 2006 1:47 pm

AlienBilly wrote:I will take that as a fact if you can explain this
Its not so much a fact than the definition of a black hole.

The gravitaional pull can not exceed the speed of light, as it's a constant.
And as layed down here the escape velocity of light is naturally the speed of light.
For an object or particle to travel at or pull at the speed of light it would requier infine energy, how can an object without infinite mass have infinite energy ?
Wouldent that contradict the formula E=mc<sup>2</sup> ?

The gravitational pull is a force not a velocity. But it is so strong that light and everything that is slower than light can not escape (below the given radius). In that sense it indeed exceeds the speed of light.
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Postby moonlord » Fri Feb 24, 2006 2:15 pm

A black hole is the black area around a very dense object. I don't think you become energy when you pass the event horizon. You could still be in one piece, seeing light the respective object emmits but which cannot pass the event horizon.

However, most scientists today agree that inside black holes there are singularities. I must admit I haven't understood why can't there be objects with finite mass and very small, but non-zero volume.
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Postby AlienBilly » Sat Feb 25, 2006 1:19 am

bo198214 wrote:The gravitational pull is a force not a velocity. But it is so strong that light and everything that is slower than light can not escape (below the given radius). In that sense it indeed exceeds the speed of light.


So you're seriously saying that an object of finitive mass and thus finitive energy can have a gravitational pull (which also spreads with the speed of light), that's faster and stronger then there is energy to ?

Your super dense object would indeed dent the space around it very suvearly, and you would relativly probably need to be traveling in speeds of up to 75% of the speed of light to escape it.

But the CURVE that it's gravitational force is using on it's surrounding is
not infinitivly deep, that's why light would still escape your object, because
the light would just go in a straight line down your gravitational dent and up the other side.
However when you have a singuarity the gravitational curve i infinete, så the light just keeps on going in a straight line towards the singularity for infinity.

And an object with volume has a non-infinite mass so it doesn't have infinete energy, and without infinete energy the gravitational force does simply not have power to constrain light, or something that's traveling in the speed of light.

You say that gravity is a force not a speed.... doesnt your little mattematic stunt on the escape velosity show that force and speed
are both an expression of energy ?

And as we know from E=mc<sup>2</sup> to reach the speed of light
either it's a pull or push, it's still requiers the same amount of energy,
which in this case is infinite (just do the math on E=mc<sup>2</sup>)
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Postby houserichichi » Sat Feb 25, 2006 1:53 am

Gravitational waves propagate at the speed of light, the reasons for which (if you care in the first place) can be found in this paper up until the middle of page 5.

Don't worry about "how deep" a black hole is, but rather how curved spacetime is in a general area. Infinite curvature implies black hole.

Force and velocity don't even have the same units as energy, though they can be related to eachother by simple arithmetic and dimensional analysis. E=mc^2 is the rest energy. There is a longer version of the equation for accelerating bodies. Which one are you referring to?
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Postby jinydu » Sat Feb 25, 2006 8:42 am

Light does not have infinite energy, even though it travels at the speed of light. This is because light has zero mass. And force and velocity are not the same thing; one is measured in Newtons and one is measured in meters per second.
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Postby AlienBilly » Sat Feb 25, 2006 10:18 am

jinydu wrote:Light does not have infinite energy, even though it travels at the speed of light. This is because light has zero mass. And force and velocity are not the same thing; one is measured in Newtons and one is measured in meters per second.


Sorry, my bad about the velocety and force thing ... flue+fever+beer does not equal brain groth...I was thinking acceleration...

And yes, true that light doesnt have infinite energy,
m*c<sup>2</sup> where m=0 equals 89875517873681764
which is not an infinite amount of energy..

However to make light unable to escape an object it needs a gravitational
force that can deselerate light to 0, and wouldent you need the same
amount of energy to accelerate to the speed of light as to deselerate from it ?
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Postby houserichichi » Sat Feb 25, 2006 11:28 am

AlienBilly wrote:...to make light unable to escape an object it needs a gravitational force that can deselerate light to 0


All you'd need to do is sufficiently curve spacetime. In a photon's frame of reference it never slows down when it enters the black hole...in fact, even in ours that's true. Light is redshifted off the scale but not slowed down.
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Postby moonlord » Sat Feb 25, 2006 5:36 pm

AlienBilly wrote:m*c<sup>2</sup> where m=0 equals 89875517873681764


If m=0 then mc^2=0.
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Postby jinydu » Sat Feb 25, 2006 8:44 pm

The formula E = mc^2 is in fact only valid for massive particles at rest.

A more general formula is E = gamma * mc^2, which is valid for any massive particle.

An even more general formula, that applies to both massive and massless particles at any speed is:

E = sqrt((mc^2)^2 + (pc)^2), where p is the momentum of the particle

Light has no mass, so its energy is given by:

E = pc
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Postby bo198214 » Sun Feb 26, 2006 10:38 am

moonlord wrote:However, most scientists today agree that inside black holes there are singularities.


The problem with black holes is that in classical mechanics the (average) orbit velocity is independent of the mass of the orbiting planet
sqrt(GM/r)
That means, if I choose the r small enough then the orbiting planet must be superluminal. And now is the question then what happens for bodies so near to the core of the black hole. And maybe general relativity has answers for this, together with using singularities.

Though I should mention that there is an outer area of the black whole where the orbiting velocity is between c/sqrt(2) and c. Because the orbiting velocity at the Schwarzschild-Radius R is:
sqrt(GM/R) = sqrt(GM/ (2GM/c<sup>2</sup>)) = c/sqrt(2)

And if I look at the number c/sqrt(2) I realize that it is circa 0.70 c = 70% c = the number that AlienBilly always mentioned. Dont know where he snapped it up and what it did to his mind ;)
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