A question about dark energy and the expansion/acceleration of the Universe.

This is due to the fact that it counteracts the attractive force of gravity on a large scale. This has been observed through the brightness of Type IA supernovae and confirms that the universe is indeed accelerating. In summary, the expansion of the universe is accelerating due to the presence of dark energy, as observed through the decreasing brightness of Type IA supernovae with increasing redshift.
  • #1
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I was curious about whether or not the Universe was accelerating or decelerating and how we could know one way or another.

I read an article I found online http://curious.astro.cornell.edu/question.php?number=63" and it said that, among other things, that the universe is accelerating partly due to dark energy and its "repulsive force of empty space that counteracts gravity on large scales." I had never heard of anything actually "repulsive" to gravity and was wondering if this was right or wrong.
 
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  • #2
It is correct that the expansion of the universe is accelerating. The way this has been typically measured is to look at things, typically Type IA supernovae, which we know how bright they should be. If the universe is accelerating then they'll look less bright as a function of redshift than they would if the universe wasn't accelerating.

It can indeed be shown that a term with negative pressure, like dark energy, causes the expansion of the universe to accelerate.
 

1. What is dark energy and how does it affect the expansion of the Universe?

Dark energy is a hypothetical form of energy that is thought to make up about 70% of the total energy in the Universe. It is believed to be responsible for the current accelerated expansion of the Universe, meaning that the distance between galaxies is increasing at an ever-increasing rate.

2. How do we know that dark energy exists?

The existence of dark energy is inferred from observations of the large-scale structure of the Universe, such as the distribution of galaxies and the cosmic microwave background radiation. These observations show that the expansion of the Universe is accelerating, which cannot be explained by the known forces of gravity and matter alone.

3. How does dark energy differ from dark matter?

Dark energy and dark matter are two separate and distinct concepts. Dark matter is a type of matter that does not interact with light, but can be detected through its gravitational effects on visible matter. Dark energy, on the other hand, is a form of energy that is thought to permeate all of space and is responsible for the accelerating expansion of the Universe.

4. Are there any theories that explain the origin and nature of dark energy?

There are several theories that attempt to explain the origin and nature of dark energy, but none have been proven definitively. Some theories suggest that dark energy is a property of space itself, while others propose the existence of a new type of particle or field that is responsible for the acceleration of the Universe.

5. How does the discovery of dark energy impact our understanding of the Universe?

The discovery of dark energy has significantly impacted our understanding of the Universe, particularly in the field of cosmology. It has led to the development of new theories and models to explain the accelerating expansion of the Universe, and has raised questions about the ultimate fate of the Universe. It also highlights the fact that there is still much we do not know about the Universe and the fundamental forces that govern it.

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