# How can space know how to curve

• duordi
In summary: The black hole solutions (generalized Kerr-Newman, which includes Schwarzschild as a special case but also includes rotating and charged holes);(2) The FRW solutions, which are central in cosmology.
duordi
How can space know how to curve from a black hole.
My understanding is that the no information can escape a black hole
so how can space know how much to curve?

Duordi

Thanks for the reference.
There was some interesting discussion.

So technically nothing actually goes inside a black hole it is all frozen in time outside the black hole.

Duordi

"Nature cannot be fooled."

Margarine can fool mother nature.

So technically nothing actually goes inside a black hole it is all frozen in time outside the black hole

Technically, something does go into a black hole, and whatever that is does not come out. Sometimes a chair is just a chair.

so how can space know how much to curve?

Space doesn't "know" anything, it just does what it does, and what it does is curve or bend asccording to Einsteins GR equations. That is a first principal concept, not up for analysis unless you want to challenge the foundations.

DiracPool said:
Space doesn't "know" anything ... what it does is curve or bend according to Einsteins GR equations...

Isn't that putting the cart before the horse?

duordi said:
So technically nothing actually goes inside a black hole it is all frozen in time outside the black hole.

No. Things can fall into the black hole; it's just that nothing that happens inside the black hole's horizon can affect anything outside. So the gravity you feel outside the hole can't come from inside the hole; it comes from somewhere else. (As I noted in my posts in that thread, it actually comes from the past history of the object that collapsed to form the hole.)

Isn't that putting the cart before the horse?

What do you mean by that? First of all, Einsteins GR equations are non-linear, and therefore are only solvable via numerical integration, with perhaps the exception of the shperical Schwarchild thinga-ma-bobber.

DiracPool said:
What do you mean by that? First of all, Einsteins GR equations are non-linear, and therefore are only solvable via numerical integration, with perhaps the exception of the shperical Schwarchild thinga-ma-bobber.

I meant Einstein's equations describe how space curves, rather than space curving to keep in line with Einstein's equations. Just joking!

BTW, question to anyone who may know the answer - is space 'bending' a scientific term (as opposed to 'curving')?

BTW, question to anyone who may know the answer - is space 'bending' a scientific term (as opposed to 'curving')?

What's the diff? Sounds like the same thing to me.

arindamsinha said:
is space 'bending' a scientific term (as opposed to 'curving')?

"Curving" is the term I usually see in papers (or popular books and articles) written by scientists; "bending" seems to be a more colloquial term used by laypeople.

DiracPool said:
First of all, Einsteins GR equations are non-linear, and therefore are only solvable via numerical integration, with perhaps the exception of the shperical Schwarchild thinga-ma-bobber.

This is not correct. There are many exact, analytical solutions known to the Einstein Field Equation:

http://en.wikipedia.org/wiki/Exact_solutions_in_general_relativity#Types_of_exact_solution

Nonlinear differential equations are harder to solve than linear ones, but "harder" is certainly not the same as "impossible".

This is not correct. There are many exact, analytical solutions known to the Einstein Field Equation:

Ok, so maybe there are more exact solutions than the Schwartzchild one, but, in fact, Einstein's field equations are notorious for being intractable analytically, for exactly the reason I mentioned, the non-linearlity of the differential equations. In neuroscience, we have the same problem with Freeman's KV model which couples thousands of non-linear ODE's to model the solutions. Impossible to solve even the simplest scenarios analytically.

DiracPool said:
Ok, so maybe there are more exact solutions than the Schwartzchild one, but, in fact, Einstein's field equations are notorious for being intractable analytically, for exactly the reason I mentioned, the non-linearlity of the differential equations.

This is true, but it's not as extreme as it appears to be in neuroscience by your report:

DiracPool said:
Impossible to solve even the simplest scenarios analytically.

The exact solutions listed on the page I linked to include "simple scenarios" that are pivotal in our understanding of the universe:

(1) The black hole solutions (generalized Kerr-Newman, which includes Schwarzschild as a special case but also includes rotating and charged holes);

(2) The FRW solutions, which are central in cosmology.

It is true that for more complicated cases, which lack the symmetry of the above classes of solutions, we use numerical simulations; but the exact solutions above have given a lot of insight into the key factors involved. So analytical solutions, idealized as they are, are extremely important in GR.

It is true that for more complicated cases, which lack the symmetry of the above classes of solutions, we use numerical simulations; but the exact solutions above have given a lot of insight into the key factors involved. So analytical solutions, idealized as they are, are extremely important in GR.

Point taken. You still haven't addressed my assertion that margarine can fool mother nature, though...

DiracPool said:
You still haven't addressed my assertion that margarine can fool mother nature, though...

You're right, I haven't. I think I'm a counterexample; at least, I am if "margarine" is broadly interpreted to mean "butter substitute". Those haven't helped me lose any weight.

I think I'm a counterexample; at least, I am if "margarine" is broadly interpreted to mean "butter substitute". Those haven't helped me lose any weight.

I still can't believe it's not butter..

## 1. How does space know how to curve?

Space itself does not "know" how to curve. The concept of curved space is a mathematical model used to describe the behavior of objects in space, based on Einstein's theory of general relativity.

## 2. Why does space curve?

According to Einstein's theory, the presence of massive objects in space creates a curvature in the fabric of space-time. This curvature is what we perceive as gravity and it affects the motion of objects in space.

## 3. How can space have curvature if it is infinite?

The curvature of space is not limited by its size or boundaries. It can exist in both finite and infinite spaces. The concept of curved space is a mathematical abstraction used to explain the effects of gravity.

## 4. Is curved space the same as a black hole?

No, a black hole is a region of space where the curvature is so intense that not even light can escape. Curved space, on the other hand, exists everywhere in the universe to some degree due to the presence of matter.

## 5. Can we physically see the curvature of space?

No, the curvature of space is not something that can be seen with the naked eye. It can only be observed indirectly through its effects on the motion of objects in space.

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