# Question about the oscillatory universe theory.

Asked by jaketheripper (2764 ) November 6th, 2009

Ok maybe this is a completely stupid and uninformed question but here I go…
Why would there be enough energy to explode when matter is at its closest and gravity is at its strongest, but then when the matter is completely dispersed and gravity is weaker It causes another crunch?
If there was enough gravity to cause a crunch wouldn’t it maintain that dense state indefinitely?

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The quick answer is that physics works differently at the smallest scales. Gravity is an incredibly weak field, and other forces come into play when you’re on subatomic scales.

That is: “The main idea behind the quantum theory of a Big Bounce is that, as density approaches infinity, the behavior of the quantum foam changes. All the so-called fundamental physical constants, including the speed of light in a vacuum, were not so constant during the Big Crunch, especially in the interval stretching 10−43 seconds before and after the point of inflection. (One unit of Planck time is about 10−43 seconds.)” (from http://en.wikipedia.org/wiki/Big_Bounce )

grumpyfish (6589 )

It’s a little bit like the following:

Take a Slinky and attach a small weight to one end of it that stretches it out about 2–3 ft and then pull it further down and release it . The small weight oscillates in space up-and-down…... down, when the force of gravity is stronger than the tension in the expanding spring and then reversing its motion, up, when the tension in the spring exceeds the force of gravity trying to pull the weight down .

virtualist (2430 )

Just as when you through the ball up and it comes down, if there was not enough energy in the whatever-caused-the-first-big-bang, all matter will come back. That’s oscillating universe theory.

More specifically:
Why would there be enough energy to explode when matter is at its closest and gravity is at its strongest, but then when the matter is completely dispersed and gravity is weaker It causes another crunch?
When matter is completely dispersed, it will move very very slowly, so will be pulled back even by weaker gravity, until everything crunches. Remember the ball…

If there was enough gravity to cause a crunch wouldn’t it maintain that dense state indefinitely?
People don’t know what caused the big-bang, thus the hearsay goes that once matter is pulled back to super-dense-singular-dot state, that unknown mechanism will kick in to reverse everything. Roughly speaking…

gagara (102 )

I think the important concept here is escape velocity. If you throw a ball into the air, it will come back. If you throw it harder, it will take longer to return, but it still will. Even bullets will fall back to Earth somewhere. However, if you were to fire a bullet at 11.2km/s, it would escape the Earth’s gravitational pull forever (assuming, like most physics experiments that you are working in a vacuum).

When it comes to the mass of the universe, escape velocity becomes a little more tricky because there is no central point that mass gravitates to. Instead we have fragments of matter scattered over much of the universe, and each piece is exerting a gravitational field. Gravity works over infinite distance (qualified of course by the speed of gravity), so matter will never truly escape the gravitational pull of other matter. It is just a question of whether or not escape velocity has been reached – calculated relative to every other piece of matter in the observable universe.

It is my personal opinion that the universe is open, meaning it will expand at ever increasing rates until it reaches a cold death. The oscillating universe theory predicts a Big Crunch. For this to happen, the majority of the matter in the universe must be travelling below escape velocity, and hence be able to be drawn together once again by the force of its own gravity. Gravity will always slow matter, but if the velocity of that matter is large enough it will never slow enough to reverse its direction. If the velocity is small enough, then the matter will eventually collapse into the source of the gravitational field.

When matter scrunches together it forms a black hole. Does the oscillatory theory say that when a black hole gets sufficiently large, it explodes?

@LostInParadise Some do say that a black hole may in some way explode as a white hole and this ‘symmetry’ is necessary. There is no evidence of any white holes as yet, to my knowledge.

virtualist (2430 )

@LostInParadise Eh, sort of. The problem is that within Planck time of the singularity, nobody’s really sure what happens. It’s sort of like that Far Side cartoon “and then magic happens….”

We know, from all available evidence, that the universe as we know it went kapow!* from something akin to a singularity, approximately 13.5 to 14 billion years ago. We don’t know what happened “before” and infact there may not have been time as we know it before.

* the exact scientific term.

grumpyfish (6589 )

@grumpyfish, I know that nobody knows for sure what happened. As I understand it, the oscillatory theory is one possible explanation among many.