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# Astrophysics/Singularity?? & Atoms

Question
QUESTION: What exactly does it mean when something is a singularity, and are there others that aren't blackholes? I can understand how blackholes are extremely dense areas of matter packed into a small area of space as a result of stars that collapse in on themselves, but I am not keen on the idea of anything that can be packed infinately small on its own force. That can't be true? Maybe the mass of a star packed into the size of a marble?

Also I was wondering how much energy is packed into each atom? How can it be measured? And would the explosion caused by an atom and anti-matter atom colliding release as much energy as 2 atoms respectively?

ANSWER: "Singularity" is what we mean when we (physicists) reach a point where the laws of physics break down.  A black hole (two words) is what happens when gravitational pull exceeds a certain limit where light cannot escape it.  Also, not all black holes are small, since their radius expands much faster than normal objects as they absorb matter.  Scientists are no more comfortable with the question of "what is a singularity" than you are, and are working to solve that mystery... but that's at the edge of our understanding right now.

How much energy?  A tiny amount in the electrons.  How can it be measured?  That requires years of nuclear physics courses to explain, and is beyond the scope of this forum...but it is quantifiable for sure.

That last question is easy, yes it would (multiplied by the square of the speed of light, good old E=mc^2 to the rescue).  The form it would release it in would rapidly decay to various particles and neutrinos and photos with high energies, but the total energy would remain the same.

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QUESTION: So blackholes as we know them are so far just mathematical concepts that although have a physical component are only give broad assumptions based on a very limited amount of data since we've never been able to get ourself or anything else near one? Are we any bit close to seeing the symtoms of a white hole?

And could I take my weight in grams, figure the number of moles, and determine how much energy there is in my own molecules?

ANSWER: There's no such thing as a white hole, period.  And black holes have been observed in the accretion disks around them.  Those disks are some of the brightest objects in the universe, so yes black holes are easily observed in terms of the matter around them.  They are not just mathematical concepts.

And of course you can calculate that, just use Einstein's relationship E=mc^2.  Of course, you'd have to figure a way to convert that matter into energy first to get that energy output, which is currently not possible.

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QUESTION: So just to clarify we don't really know how compact matter in a blackhole is in relation to the space it takes up (also considering that without matter itself there is no way to measure space)? I know our sun is too small to become a blackhole in all chance, but if it were to how small a space would it fold into compared to say a snowglobe? There is no such thing as infinite reduction in size, is there?

Black hole is two words, not one.  Please don't bug me with the non-word "balckhole."

The point is that we don't know what happens at the very center of a black hole, but the laws of physics dictate that all the matter in one shrink to a single point.  The "radius" of a black hole is given by setting the escape velocity from the compact object equal to the speed of light.    That gives enough gravitation that space becomes more like time...it only has one forward direction to the center of the black hole.  If the Sun was about 40% bigger it could eventually become a black hole.  We know that compact objects of enormous gravitation exist, we observe the matter surrounding them, and we know that black holes satisfy Einstein's gravitational field equations.  As to the singularity, there's no way to get information out of a black hole, so we currently know that the equations are valid and that all the mass should reside in a single point in the center.  Until new physics is uncovered to invalidate this, and with very good reason, there's nothing else we can say about what happens in the very center of a black hole.  Matter can exist in the region between the event horizon of the black hole (what you would consider to be its "size," in a way) and the center, but it always must move towards the center.  Everything else about the center of a black hole is speculation at this point, until some of the more advanced theories come along a lot further.

Astrophysics

Volunteer

#### Dr. Stephen O. Nelson

##### Expertise

Fusion, solar flares, cosmic rays, radiation in space, and stellar physics questions. Generally, nuclear-related astrophysics, but I can usually point you in the right direction if it's not nuclear-related or if it's nuclear but not astrophysics.

##### Experience

Just moved from being a physics professor at the University of Texas of the Permian Basin into government work. Doctoral dissertation was on a reaction in CNO-cycle fusion, worked in gamma-ray astronomy in the space science division of the naval research laboratory in the high-energy space environment branch.

Organizations
Government work as a physical scientist with a nuclear focus.

Education/Credentials
Ph.D. in physics, research was on nuclear fusion reactions important in stellar fusion, further work on space telescope technology.