# What is Dark Energy: The Most Common Type of Energy in the Universe

• meteor
In summary: But once the universe was large enough, it would have had a noticeable an effect. I don't think there's anything wrong with proposing different types of quintessence, as long as the fundamental principle is that it's all the same energy.

## What's dark energy?

• ### Dark energy? That doesn't exist

• Total voters
8

#### meteor

What's dark energy?
It's important to know what is the most common type of energy of the universe

All of your choices are the same thing.

The names "quintessence," "vacuum energy density," "lambda," "cosmological constant" and "dark energy" are all synonymous.

- Warren

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No. Vacuum energy is due to the negative pressure of virtual particles that continually appears in space. Quintessence is aa propossal of Paul Steinhardt, and consists of a scalar field that permeates the space

Originally posted by meteor
No. Vacuum energy is due to the negative pressure of virtual particles that continually appears in space. Quintessence is a propossal of Paul Steinhardt, and consists of a scalar field that permeates the space

I have the impression (correct me if i am mistaken) that
if the dark energy is "vacuum energy" then it must be constant throughout space

but it seems to me that now so many different people have
proposed different kinds of "quintessence" that the idea has
some flexibility----some kinds of quintessence are imagined to have a variable energy density (?)----and especially the equation of state is less restricted

for vacuum energy one must have an exact equality:
p = - rho
where p is the pressure

for quintessence I believe there is a parameter w
which may be exactly -1, or may be some number near -1,
and the equation of state is then

p = w rho

people who want more freedom to play around theoretically may
prefer quintessence because the possibilities are not so
narrowly restricted as with vacuum energy

but I believe it is very much the same thing fundamentally----a constant or nearly constant energy density associated with the vacuum

I must agree with chroot. The vacuum energy can be modified and shown to be equivalent to a uniform scalar field that permeates all space.

All choices are equal, hence I chose the one that has both.

Brad_Ad23: Marcus is right. The vacuum energy is the same that the cosmological constant of Albert Einstein and is supposed to be constant through time. Quintessence is supposed to change in time and place. For example, nowadays it exerts negative pressure. But from Big Bang til 50000 years after it, it exerted positive pressure. It's not discarded that quintessence can return to exert positive pressure (thus provoking the universe to contract again)
There's something I can't comprehend: How can vacuum energy drive the acceleration of the universe?
I'm interested to hear the possible alternatives of the people that have voted Other thing
Comment: NASA researchers believe that dark energy is more likely vacuum energy than quintessence

Isn't dark matter just the matter that we can't see, I mean of the stuff in space much is not in the form of a sun as not giving off light or detectable energy at this time so that there might be a lot of space dust or small rocks and be attributed to dark energies that speed up galaxy rotations?

Dark energy don't speed up galaxy rotations

A new candidate to dark energy has appeared: the generalized Chaplygin gas

I know what marcus was saying. I was saying that the mechanism behind this is believed to be operating under the premise of the negative pressure that quantum fluctuations as a whole make. The more space expands, the more space there is for added flux, and hence you get an accelerative process. Up until the point where the universe was large enough to sustain this, the quantum vacuum or whatever you wanted to call this would have had a negligable impact.

## 1. What is dark energy?

Dark energy is a type of energy that is thought to make up about 70% of the universe. It is a mysterious force that is causing the expansion of the universe to accelerate.

## 2. How is dark energy different from other types of energy?

Dark energy is different from other types of energy because it is believed to have a negative pressure, causing it to repel matter and accelerate the expansion of the universe. Other types of energy, such as electromagnetic energy and nuclear energy, have positive pressure and do not have the same effect on the expansion of the universe.

## 3. What evidence do we have for the existence of dark energy?

The existence of dark energy is supported by observations of the expanding universe, which show that the expansion rate is increasing over time. This suggests the presence of a repulsive force, which is believed to be dark energy. Additionally, the cosmic microwave background radiation and the distribution of galaxies also provide evidence for the existence of dark energy.

## 4. How does dark energy affect the fate of the universe?

Dark energy is believed to play a crucial role in the fate of the universe. If the amount of dark energy remains constant, it will continue to cause the expansion of the universe to accelerate, eventually leading to a "big rip" scenario in which all matter in the universe is torn apart. However, if the amount of dark energy decreases over time, the expansion of the universe may eventually slow down and reverse, leading to a "big crunch" scenario in which the universe collapses back in on itself.

## 5. Can we harness dark energy for practical use?

At this time, we do not have the technology or understanding to harness dark energy for practical use. Its nature is still largely unknown, and it is currently only observed through its effects on the universe. However, further research and advancements in technology may one day allow us to harness this mysterious force for practical purposes.