How do we know we are not inside a blackhole?

[marcelhattingh]

If you fall into a black hole, that what is closer to the singularity, will fall faster that than what is further. However, space before and after you, is falling in with you. So from each General Relativistic perspective of "you", because there would be no inertial frame to orient yourself (you could see), it would seem, like you are standing still, with all matter in your personal observable universe expanding in all directions, in an accelerating manner. What if this is already busy happening. What if the Hubble Horizon is just our personal event horizon, as seen from the "inside", and Dark Energy, is just due to extreme tidal effects? If this is true, the observed red shift due to apparent expansion wouldn't be 100% uniform in different directions (measured at fixed distances from earth). This is because of the inverse distance square law in Newton's Gravitational Force equation. Any thoughts?

 

[stevendaryl]

There is a discussion of whether the universe might be a black hole here:
http://math.ucr.edu/home/baez/physics/Relativity/BlackHoles/universe.html

 

[Kevin McHugh]

Is your body still in one piece? As I understand it, your body would be torn to shreds from the gravitational forces. So perhaps the proof is in the pudding.

 

[stevendaryl]

Is your body still in one piece? As I understand it, your body would be torn to shreds from the gravitational forces. So perhaps the proof is in the pudding.

That's a misconception about black holes. The gravitational stresses inside a black hole can be quite mild for a period of time. Eventually they will become great enough to rip you to pieces, but depending on the size of the black hole, that "eventually" can be an arbitrarily long time.

 

[Kevin McHugh]

That's a misconception about black holes. The gravitational stresses inside a black hole can be quite mild for a period of time. Eventually they will become great enough to rip you to pieces, but depending on the size of the black hole, that "eventually" can be an arbitrarily long time.

As I understand it, the forces that would rip a body apart are due to differential acceleration as the body is drawn to the black hole. Is that correct?

 

[Chronos]

The short answer is no, the universe is not a black hole, as noted by stevendaryl. For further discussion, see http://www.preposterousuniverse.com/blog/2010/04/28/the-universe-is-not-a-black-hole/

 

[PeterDonis]

As I understand it, the forces that would rip a body apart are due to differential acceleration as the body is drawn to the black hole. Is that correct?

It is true that a body free-falling into a black hole will be ripped apart by tidal forces at some point. But that point might be deep, deep inside the horizon, almost to the singularity. So there can be a very large volume of spacetime inside a black hole where bodies are not ripped apart by tidal forces.