# Tag Info

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### At the Big Bang, when everything was close together, why did it not "collide", violating Planck length or Pauli Exclusion Principle?

The Pauli Exclusion Principle forbids two indistinguishable fermions occupying the same quantum state. It does not prevent them getting arbitrarily close together so long as they have very different ...
• 115k

### Does matter accumulate just outside the event horizon of a black hole?

What you're describing is basically the "collapsed star" (Eng) or "frozen star" (Rus) interpretation of black holes that was common prior to the late mid-1960s. It was a mistake. Suppose you are ...
• 7,674
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### Does matter accumulate just outside the event horizon of a black hole?

Yes, you are absolutely right, from OUR VIEWPOINT it does. From Kip Thorne's book "Black Holes and Time Warps: Einstein's Outrageous Legacy." “Like a rock dropped from a rooftop, the star’s surface ...
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### What's the percentage of strange matter inside a star at any time?

Zero. Normal stars are not dense enough to produce strange matter. They have regular matter only (neutrons and protons). Strange matter has been hypothesized to form inside neutron stars, but this is ...
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### Could there be dark matter black holes?

The problem with trying to form a black hole with dark matter is that dark matter can only weakly interact (if at all) with normal matter and itself, other than by gravity. This poses a problem. To ...
• 115k
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### Is normal matter always accompanied by dark matter and vice versa?

We lack the precision to say that there aren't regions where there is matter without dark matter or vice-versa. But what is clear is that the ratio of dark matter to normal matter, which is (or needs ...
• 115k
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### What are the differences between matter, dark matter and antimatter?

Matter is the stuff you are made of. Antimatter is the same as matter in every way, looks the same, behaves the same, except its particles have electrical charges opposite to matter. E.g., our ...
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### Does matter accumulate just outside the event horizon of a black hole?

We need to think about just where the time dilation effect occurs. By then thinking about the observations from each point of view, that is the free falling object and the external observer, we can ...
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### Could there be dark matter black holes?

As pointed out by Rob Jeffries, forming a black hole (BH) from dark matter (DM) is impossible (unless there is a [hypothetical] interaction by which dark-matter can lose energy that evades all ...
• 5,276
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### When the universe expands does it create new space, matter, or something else?

Yes, space is constantly being created. The new space does not hold any matter (like atoms) or dark matter. This means that the density of normal and dark matter decreases at the same rate as the ...
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### Is there any proof of space being created?

This is an intriguing proposition, but I would ask how your hypothesis explains that the universe appears to be flat? That is with $\Omega_M + \Omega_\Lambda = 1$. The evidence for this comes from ...
• 115k
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### Do we know how old the matter that makes us is?

The material (heavier than helium) that makes up the solar system was made in millions, if not hundreds of millions of stars that lived and died in the ~7 billion years between the formation of the ...
• 115k
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### What's the percentage of strange matter inside a star at any time?

Let me first underline two specific definitions of @Alexandre: We are looking for "matter", that means a finite region in space in thermal equilibrium. And we are looking for "...
• 106
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### How is observable matter distributed in the universe?

I think the following is a fair summary. It's based on a fairly old study by Fukugita & Peebles (2004) but the numbers are quite reasonable. Your guess about stars dominating is way off. Most of ...
• 115k
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### How does gravity interact with a photon?

It is simply not true that gravity can only interact with mass. Rather, any long-range spin-2 force interacts with all energy-momentum equally, and it source is the stress-energy-momentum tensor. That ...
• 7,674
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### What explains the existence of energy/matter if it cannot be created or destroyed?

That's a very complicated question! First, let's remember that Moses didn't bring the Law of Conservation of Energy down from Sinai on stone tablets -- it's something that we've observed to be true ...
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### Does matter accumulate just outside the event horizon of a black hole?

Several wonderful yet technical answers have been given, and I cannot add anything to those very nice answers that explain why it is not useful to think black holes get "frozen" at their event ...
• 5,142
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### Scenarios: Abusing a black hole

Black holes are not "made of matter". They are better described as structures of gravity/warped spacetime. However, they do grow when absorbing things with positive mass-energy. Antimatter still has ...
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### Does matter accumulate just outside the event horizon of a black hole?

The logical consequence is, that an event horizon cannot form, since the first particle slows down asymptotically to zero, just before the event horizon forms (Fermat's infinite descent). The ...
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### How much larger would a star have to be to cause thermonuclear reactions if it was made out of mostly rock like Earth, instead of gases?

It really depends what you mean by "rock". At the temperatures and pressures at the cores of stars (and at which nuclear fusion reactions are possible), "rocks" as I suspect you are thinking of, do ...
• 115k
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### What percentage of the hydrogen today has never been in a star

About 70% of the baryonic matter in the universe is hydrogen, with a mean density of about $4\times 10^{-29}$ kg/m$^3$. Most of the stars that have ever been born are still alive, since an average ...
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### Could there be dark matter black holes?

Black holes are the result of mass so concentrated that gravity does not let anything out, including light. Just about the only things we know about dark matter is that it has mass and seems to only ...
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### Does matter accumulate just outside the event horizon of a black hole?

Thought provoking cosmologists! I'm uber late to this discussion as I see it has been ongoing for literally years and don't know if there is still anyone monitoring this thread, but here' goes. I ...
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### Why isn't the black hole white?

What's going on here is that you have been misled into thinking the ring-like structure has anything to do with the accretion disk. It doesn't, or at least only indirectly. The disk is referred to as ...
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### Mass distribution in the early universe

It is unfortunate that the usual poor journalism labels the growth of the black hole as "inexplicable" and then further down in the article refers to some possible explanations. The basic problem is ...
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### How does gravity interact with a photon?

What we call "gravity" is really just the distortion of spacetime. If spacetime was completely straight, there would be zero gravity. But the existence of a massive body is one of the things that can ...
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### Is there any proof of space being created?

As is always the case in physics, there is no proof. But if your scenario were true, it would have to be rather fine-tuned in order to create the observed expansion of the Universe. First of all, ...
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### Are we made of stars we're seeing?

Stars really are immensely far, however it's a common misconception that the stars that you can see are millions of light years away. Most of the visible stars are a few tens to a few hundreds of ...
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### Conversion of matter into antimatter

It would be more accurate to say that a black hole eventually turns whatever falls in it into equal quantities of matter and antimatter. The difference between matter and antimatter is defined by ...
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