# Volume of a Negitive Sphere.

by PoPpAScience
Tags: negitive, sphere, volume
 P: n/a If I wanted to run a formula for the Volume of a Negitive Sphere on a computer which way would I write it?: V=(4pi/3)-r^3 or V=(4pi/3)r^(-3) or ? Has anyone else tried to run this formula on a computer?
 P: 1,370 What in the world is a negative sphere? If you have the formula for a negative sphere, just make a function to do the calculation. What is the problem?
 P: n/a The problem is lack of math education. The question is do I put the negitive sign in front of the r or the 3? A negative sphere can be pictured as a reverse Big Bang. Also, I am wondering what happens if this equation is run on a computer. Tks 4 your replies.
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## Volume of a Negitive Sphere.

So I'm guessing a negative sphere is a sphere with negative volume!? If it is, put the negative sign in front of the r. I'm not sure what you mean by "running" the equation on a computer. You can do this on a calculator if you wanted to, so...
 PF Patron Sci Advisor Emeritus P: 10,400 1) There is no such thing as a negative sphere. Radii can only be zero or positive. 2) A sphere is not a model of the big bang. It's just a sphere. 3) You don't "run an equation" on a computer. You can solve an equation with a computer, or you can use a computer to plug numbers into any formula you can dream up. That doesn't mean the results mean anything. - Warren
 P: n/a Thank you for those replies. Another question if you pls. When one puts two mirrors in front of another, there seams to be an over lapping reflection, maybe into infinity. If at the moment of alining the two mirrors, the reflections take time to reflect back and forth into infinity, what would be a formula to describe this? Please be patient with my process, this is the first time I have asked any questions about my thoughts. Thks.
 PF Patron Sci Advisor Thanks Emeritus P: 38,400 How about an object with constant negative curvature? Is it a closed figure? Does it have a finite volume?
 P: 608 Maybe what you mean is an inverse sphere instead of a negative sphere?
 P: n/a Yes Entropy that sounds like a better discription. Tks.
 PF Patron Sci Advisor Emeritus P: 10,400 I can't say I know what an inverse sphere is, either. - Warren
 P: n/a Lets say if you take the Singularity at the beginning of the Big Bang theory, and instead of it exploding outwards into some unknown medium, it instead exploded in upon itself. What would that equation be?
 PF Patron Sci Advisor Emeritus P: 10,400 There's no "equation" for such a situation. - Warren
 P: n/a Tks Warren for your replies. I see I am going to have a hard time equating my thoughts on reverse expansion from a "Zero Point". The only time this can happen, is at the very beginning of our Universe. I can see it , but I can not express it. I feel the equation "(4pi/3)-r^3" would cover this, if a number generator starting at Zero is introduced to "r". This number generator can run into infinity, or have a stopping point. I have seen on tv animation where it looks as if you are falling forever into a smaller point (like a black Hole), or like my mirror example from before. This is the way I see it.
 P: 2,824 I fear for you PoPpAScience, because you say you suffer from lack of math education (well, we all do ) and you are trying to tackle problems that are so difficult. Big Bang theory requires a fairly advanced knowledge in math and physics.
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 Quote by PoPpAScience When one puts two mirrors in front of another, there seams to be an over lapping reflection, maybe into infinity. If at the moment of alining the two mirrors, the reflections take time to reflect back and forth into infinity, what would be a formula to describe this?
Unfortunately, the light will not reflect back and forth forever as each reflection absorbs an amount of light. I remember being in an entranceway of an office building that had mirrors on all walls. As I looked at my reflections in one mirror, they repeated for what seemed like at least one hundred reflections, but eventually they faded away into darkness.

-Ray.
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 Quote by rgoudie each reflection absorbs an amount of light
Even with pefectly reflecting mirrors, that would not work, because you need an integer number of photons with definite energy (color), as opposed to classical waves whose energy can be arbitrarily small.

But there are indeed a classical formulae to describe the wave model of light reflecting on ideal mirrors.
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 Quote by PoPpAScience Tks Warren for your replies. I see I am going to have a hard time equating my thoughts on reverse expansion from a "Zero Point". The only time this can happen, is at the very beginning of our Universe. I can see it , but I can not express it. I feel the equation "(4pi/3)-r^3" would cover this, if a number generator starting at Zero is introduced to "r". This number generator can run into infinity, or have a stopping point. I have seen on tv animation where it looks as if you are falling forever into a smaller point (like a black Hole), or like my mirror example from before. This is the way I see it.
When you say "(4pi/3)-r^3" do you mean $(4\pi/3)(-r^3)$ or $4\pi/3 - r^3$? The first one doesn't make any sense as all 3D geometrical objects have a positive volume and radius is also always positive. The 2nd one seem to be applicable for a situation where you have a hollow sphere with radius one r represents the radius of the space inside the sphere.

The idea of the big bang unfortunately uses more than Euclidean geometrical shapes and requires a much greater understanding of physics and mathematics to model. However (and I don't have the knowledge in this area) I don't believe the universe is even close to a sphere.

I believe a misconception of black holes is that the centre mass is infinitely small, this is not so (although you'd need to ask a physicist).
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 Quote by Zurtex I don't believe the universe is even close to a sphere.
The current paradigm is that the expansion of the universe accelerates. That indeed implies an open universe with negative curvature. The fate of this universe would be a death due to dilution of energy.
 Quote by Zurtex a misconception of black holes is that the centre mass is infinitely small, this is not so
As far as I understand "center of mass", this is mathematically defined as the barycenter point with respect to mass density weighting : this is a single well-defined spot. But the "center" of the black-hole is the singularity of spacetime, where the 4-curvature becomes infinite. This is classically a point where the General Relativity failure occurs. It is know strongly likely that QM theory of gravitation will somehow "blurry" the singularity, either through extended objects (strings) or due to granular spacetime (like in Loop Gravity) for instance.

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