What is causing the accelerated expansion of the universe?

In summary, scientists are still trying to figure out what dark matter and dark energy are. They are both mysterious and effects are seen indirectly.
  • #1
Allen_Wolf
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What is dark matter?
What are the effects of both dark matter and dark energy?
 
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  • #2
Nobody knows exactly what they are which is partly why they are called 'dark'.
They both are observed indirectly by their effects but the cause is unknown.
In the case of dark matter something unseen is causing gravatitational effects so it has to be some kind of matter.
It's widely suspected to be some kind of subatomic particle which has so far not been detected.
That is not the only theory, but experimental work is in progress to try to detect such particles.
Dark energy is even more mysterious. Something seems to be causing the Universe to expand,
(although that is in the large scale, individual galaxies are not expanding, but generally galaxies are moving away from each other)
 
  • #3
rootone said:
Nobody knows exactly what they are which is partly why they are called 'dark'.
They both are observed indirectly by their effects but the cause is unknown.
In the case of dark matter something unseen is causing gravatitational effects so it has to be some kind of matter.
It's widely suspected to be some kind of subatomic particle which has so far not been detected.
That is not the only theory, but experimental work is in progress to try to detect such particles.
Dark energy is even more mysterious. Something seems to be causing the Universe to expand, (although that is in the large scale, individual galaxies are not expanding)
So does dark energy exerts some kind of anti-gravity?
 
  • #4
You could think of it as a force which works as an opposite to gravity, but only on the very largest scale.
At the scale of stars and planets it is insignificant,
 
  • #5
Allen_Wolf said:
So does dark energy exerts some kind of anti-gravity?
Not any more-so than magnetic levitation would be anti-gravity. When gravity pulls two objects together, they move through spacetime to get to each other. When dark energy pushes two objects apart, it does so by literally adding more space in between them.
 
  • #6
newjerseyrunner said:
When gravity pulls two objects together, they move through spacetime to get to each other. When dark energy pushes two objects apart, it does so by literally adding more space in between them.

This is a common heuristic viewpoint, but you should be aware that it has significant limitations. This came up in another thread just now, see here:

Dark energy and expansion vs gravity and spatial contraction
 
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  • #7
Just to clarify a bit, the universe is expanding and will continue to do so without interference. Observations uncovered the surprising fact that the expansion seems to be accelerating, which was unexpected. We would expect gravity to slow down the expansion instead. We have no idea what is causing the accelerated expansion, but have given it the handle of "dark energy," which sounds more dignified than "spooky expansion pushy stuff." We don't even know if it's energy. We are at the level of a cave man finding a nickel-iron meteorite and thinking it is just another rock.
 
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1. What is dark matter?

Dark matter is a type of matter that does not interact with light or other forms of electromagnetic radiation. It is invisible to telescopes and other instruments, making it difficult to detect. Its presence is inferred through its gravitational effects on visible matter.

2. How is dark matter different from regular matter?

Regular matter, also known as baryonic matter, is composed of particles such as protons, neutrons, and electrons. These particles interact with light and other forms of electromagnetic radiation, making them visible. Dark matter, on the other hand, is made up of particles that do not interact with light and are therefore invisible.

3. What is dark energy?

Dark energy is a theoretical 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 observed accelerated expansion of the universe. Its exact nature is still a mystery and is currently being studied by scientists.

4. How do scientists study dark matter and dark energy?

Scientists study dark matter and dark energy through various methods, such as observing the effects of their gravitational pull on visible matter, studying the large-scale structure of the universe, and using computer simulations. They also use instruments such as telescopes, particle accelerators, and detectors to search for and study dark matter particles.

5. What are the implications of dark matter and dark energy?

The existence of dark matter and dark energy has significant implications for our understanding of the universe. It helps to explain the observed motions of galaxies and the overall structure of the universe. It also poses new questions and challenges for scientists to better understand these mysterious components of the universe.

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