Dark Energy

[AlyssaYanagi]

To what extent, does dark energy affect universe expansion?

[bystander]

Read dark energy and expansion of the universe.

[AlyssaYanagi]

Thank you for the references and your response. I am a student studying astronomy and have been researching the concept of dark energy affecting universe expansion. Unfortunately, I do not understand exactly how dark energy expands the universe in relation with the many other factors such as dark matter and gravity.

[Chris Peterson]

Thank you for the references and your response. I am a student studying astronomy and have been researching the concept of dark energy affecting universe expansion. Unfortunately, I do not understand exactly how dark energy expands the universe in relation with the many other factors such as dark matter and gravity.

You're not alone! Nobody understands how dark energy works. It's a theoretical explanation of the observation that the Universe appears to be expanding faster as it gets older. Gravity is an attractive force, whether it stems from the mass of ordinary matter or from dark matter. If that were the only force involved, we'd expect the rate of expansion of the Universe to be decreasing with time, as gravity tries to pull it together. That's what we thought for a long time was happening- the only question being whether there was enough mass to completely stop expansion, or if that expansion would continue forever, although always getting less. Recent discoveries based on examining the brightness of certain supernovas strongly suggest that something is working in opposition to gravity- a repulsive force rather than an attractive one- and that's why the expansion rate of the Universe is increasing. Dark energy is the name we give that force, and it answers some interesting cosmological questions at a highly theoretical, mathematical level, inspiring some confidence that it's a real thing. But beyond that, many questions remain to be answered.

[bystander]

Dark energy and dark matter are essentially just place holders for things we do not know or understand.

From astrophysical observations it was apparent that there was more mass in galaxies and galaxy clusters than we could account for in the mass we could see. Since we couldn't see it, we called this mass "Dark Matter". We still don't know what it is, but we can observe its effects.

We also know from observations that universe is expanding, and that the expansion is accelerating. According to our understanding of physics, this requires energy. We don't know where this energy comes from or what it is, so let's call it "Dark Energy".

This is an over simplification, but really dark matter and dark energy are just place holders for things our understanding of physics says must exist.

[BDanielMayfield]

To what extent, does dark energy affect universe expansion?

The above answers are good. I can only add, as the simplest direct answer I can think of, is that dark energy can be thought of as a force that keeps the universe from collapsing in on itself due to gravity. It affects universal expansion by causing the rate of expansion to increase over time.

Do those answers suffice Alyssa?

[AlyssaYanagi]

Yes. Thank you all for your responses.