Would Rapid Expansion of a Parallel Universe Affect a Black Hole?

[Dryson]

I have a "What If." question.

Suppose a black hole located in a universe encounters a rapid expansion of another universe with the universe that is in close approximation to the black hole. Would the rapidly expanding universe destroy the black hole or would the expanding universe actually cause the space time around and within the black hole itself to be warped as the two colossal forms of energy unite?

 

[Orodruin]

Expansion does not work that way. The universe is not expanding into something. It is the something of the Universe that expands.

 

[Drakkith]

To elaborate on Orodruin's post, our current model of expansion describes the evolution of our own universe from a very dense state to a much lower density state over the last 13.7 billion years due to expansion. Expansion here means 'unbound objects within the universe recede from each other over time'. It does not mean that the universe has a boundary that is moving outward into pre-existing space. By our current understanding, a black hole cannot encounter another expanding universe because that is not what expansion, in the cosmological sense, is talking about.

 

[Chronos]

Shouldn't this be in the scifi forum?

 

[phinds]

Shouldn't this be in the scifi forum?

Yep.

 

[Dryson]

It is the something of the Universe that expands.

If something is expanding does it not occupy a larger area of space? If it is the something of the Universe that expands like a balloon expands then the Universe would expand outwards as an expanding force that will create an equal and opposite reaction against other something's in the Universe.

The reason this question is based off of two black holes being theorized about colliding - http://hubblesite.org/explore_astronomy/black_holes/encyc_mod3_q6.html

 

[phinds]

If something is expanding does it not occupy a larger area of space? If it is the something of the Universe that expands like a balloon expands then the Universe would expand outwards as an expanding force that will create an equal and opposite reaction against other something's in the Universe.

No, that's not the way it works. The universe is all there is. It doesn't expand "into" or "against" anything. Drakkith already explained this.

 

[Drakkith]

If it is the something of the Universe that expands like a balloon expands then the Universe would expand outwards as an expanding force that will create an equal and opposite reaction against other something's in the Universe.

You're thinking of space as something physical that presses up against something else as it expands. This is not correct. Expansion means that the distances between objects within space increases over time. The exact way expansion works is that the recession velocity, which is simply the speed that an object is moving away from us, increases as the distance between us and the object increases. If you double the distance, the recession velocity doubles as well. So if you choose an object at any finite distance from us, there will be a clear velocity that it is moving away at. Expansion will never cause an object to come towards us. In other words, there are no other 'somethings'. Expansion applies to our universe just as I explained.