COS - Expanding Universe LESSON

Expanding Universe

The universe has been expanding since the Big Bang 13.7 billion years ago. Astronomers are trying to determine what will happen in the future. Depending on the variables, the volume of the universe could follow any of the paths shown in this graph.

 

It was believed for a long time that the fate of the universe depended only on the total mass of the universe, the force of gravity between that mass, and the momentum left from the Big Bang. Scientists try to determine the total mass of the universe so we can determine the mass density. Will there be enough so that the universe will collapse in the Big Crunch, or will we fall short and expand forever in the Big Chill?
Recent observations have thrown a wrench into the calculations. It appears that the rate of expansion of the universe is increasing. This observation cannot be explained using mass and gravity. This leads to the idea of dark energy. This energy appears to cause a force of expansion in the universe. So what is this dark energy that might be causing the universe to expand?
We do not really know what dark energy is. We do know that if current observations are true, it makes up almost 70% of the universe. What we experience of the universe is only about 3-5% of the universe.
Albert Einstein was the first to suggest that empty space is not really nothingness. To understand what is happening you have to realize that as the universe expands the total volume of space increases. If there is energy associated with space, then this energy is increasing as the universe increases.  
 
Quantum Theory predicts that empty space is really a place where temporary particles are forming and disappearing. This could be the source of the dark energy. The problem at the moment seems to be that this would produce too much dark energy. Perhaps dark energy is something totally new. We may not have any idea what it is yet. One more possibility is that we do not really understand gravity and that there is more to it than current theory explains.

So if dark energy does cause the universe to increase, the rate of expansion will increase exponentially. The more volume of space, the more dark energy will exist to cause further expansion. Eventually other galaxies would become impossible to see. Everything will gather into black holes, and then those black holes will slowly change into energy.

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