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Explain to a non-physicist what goes wrong when trying to quantize gravity

Callculation in th3 Quantum field theories tends to give infinite answers to various questions. This is a problem, but it can be fixed with renornalisation. It basically works like this Measure some ...
sojuz1t1's user avatar
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Explain to a non-physicist what goes wrong when trying to quantize gravity

I am adding this answer because although @Andrew and @JF10356 wrote perfect answers, I think there are a few things that need to be explained at the "non-technical" level. I would like to ...
Árpád Szendrei's user avatar
2 votes

Realistic black holes

Why must we associate real black holes with the mathematical artifacts we call singularities ? The simplest model of the interior (inside the event horizon) of a black hole that is consistent with GR ...
gandalf61's user avatar
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2 votes

Realistic black holes

Why don't we treat theoretical singularity points and realistic black holes separately? Because black holes, as we understand them presently, are the prediction of GR, and the same theory results in ...
S.G's user avatar
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29 votes
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Can a Kerr black hole become super-extremal?

TLDR; No, it cannot. The answer to this question has a somewhat storied history. Back in 1974 Wald considered a Gedanken experiment of what would happen if you would try to drop an object into a Kerr ...
TimRias's user avatar
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4 votes

Explain to a non-physicist what goes wrong when trying to quantize gravity

The problem arises when trying to quantize gravity the same way as other fields are quantized. The standard way to solve such a quantum field theory is start from an easy-to-solve (linear) model where ...
nanoman's user avatar
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1 vote
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Deriving OPE between vertex operator: Di Francesco Conformal Field Theory equation 6.65

Yes, OP is right. Taylor expanding the exponential $:e^{i\alpha \phi(z,\bar{z})+ i\beta \phi(w,\bar{w})}:$ around $(z,\bar{z})=(w,\bar{w})$ leads to subleading singular terms in the OPE (6.65) if $\...
Qmechanic's user avatar
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3 votes

Explain to a non-physicist what goes wrong when trying to quantize gravity

I'll take a stab at an oversimplification for a partial answer here. More or less I consider this a comment addendum to JF10356's answer. Renormalization can be thought of as a very fancy resizing ...
David S's user avatar
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5 votes

Explain to a non-physicist what goes wrong when trying to quantize gravity

Trying to be very concise here: Quantum Mechanics brings minimal uncertainty (fluctuations, fuzziness) to quantities. According to general relativity, gravity is an effect of mass curving spacetime. ...
Wouter's user avatar
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26 votes

Explain to a non-physicist what goes wrong when trying to quantize gravity

I think, like a lot of technical questions, you can get different answers by "zooming in" to different levels of technical detail. Here is highest level, least technical, shortest ...
Andrew's user avatar
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Removing the cosmic horizon in the de Sitter metric

You can remove the singularity by the same trick that removes the singularity of Schwarzschild coordinates: substitute $t = u + f(r)$ for some $f$. Taking $f(r) = \ell \tanh^{-1} (r/\ell) - r$ gives ...
benrg's user avatar
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8 votes

Explain to a non-physicist what goes wrong when trying to quantize gravity

I'll give a brief explanation of renormalization. Suppose you have a single electron. According to electrostatics it produces a potential: $$V(r)=\frac{e}{r}$$ This potential seems to indicate that ...
alanf's user avatar
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47 votes
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Explain to a non-physicist what goes wrong when trying to quantize gravity

“What exactly goes wrong when trying to quantise gravity?” There is no problem specific to quantum gravity! I know this isn’t conventional way to look at it, but the physics is actually not ...
JF10356's user avatar
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3 votes

How do black holes move if they are just regions in spacetime?

The black hole is a region around a singularity. It's the singularity that creates the "gravity well" around it that we call a "black hole" and the singularity itself can move like ...
Alex's user avatar
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3 votes

How do black holes move if they are just regions in spacetime?

The renowned John Archibald Wheeler (Princeton) once (the 1960's) said "Matter tells space-time how to curve, space-time tells matter how to move" This expresses the intimate, "...
JonesTheAstronomer's user avatar
28 votes

How do black holes move if they are just regions in spacetime?

Black holes are not just regions of space time. There was once a star there. According to the law of conservation of mass and energy, the star is still there. The star has spin and angular momentum. ...
Russell Hankins's user avatar
18 votes

How do black holes move if they are just regions in spacetime?

Adding a picture to illustrate what some other answers here already have said. Suppose you throw a ball straight up into the air, and then it falls back down. You've probably seen a picture like this, ...
Solomon Slow's user avatar
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18 votes

How do black holes move if they are just regions in spacetime?

Remember, we are talking about spacetime, not just space. In space by itself, the black hole is a ball-shaped region. But it extends far into the past and future, so it's more like a kind of tube. So ...
Mark Foskey's user avatar
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3 votes

How do black holes move if they are just regions in spacetime?

First of all, a point to note is that a black hole is not a "body" in of itself. Black holes are just solutions to point masses in general relativity, analogous to point masses in newtonian ...
Ronny's user avatar
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3 votes

How do black holes move if they are just regions in spacetime?

A black hole has all the properties of an object with mass. has gravitational influence on other objects, it responds to the gravitational field of other objects (e.g a bigger black hole) and ...
KDP's user avatar
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9 votes

How do black holes move if they are just regions in spacetime?

How do black holes move if they are just regions in spacetime? It might sound strange but nothing really moves in spacetime. Say, for example, we have two black holes orbiting each other in the frame ...
S.G's user avatar
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1 vote

How do black holes move if they are just regions in spacetime?

how can black holes even move? Imagine yourself in a powerful ship hovering outside a black hole (BH) event horizon. You start to accelerate in a particular direction then get to a constant velocity ...
joseph h's user avatar
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3 votes

How do black holes move if they are just regions in spacetime?

If black holes are just regions in spacetime, how can it bend the spacetime around it, so it can remain a black hole, if there is no matter to continuously bend it? There is no matter, but there is ...
Níckolas Alves's user avatar

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