MadSci Network: Astronomy
Query:

Re: what made dark energy, what does it contain, and how does it work ?

Date: Mon Nov 12 09:21:32 2001
Posted By: Jeff Robertson, Faculty, Physical Sciences
Area of science: Astronomy
ID: 1004195828.As
Message:

When you throw a ball up in the air, you give it a finite amount of energy. It rises against gravity but eventually slows down and returns to earth. Scientists had thought that this would also be the ultimate fate of the universe. However, recent findings suggest that the universal expansion is accelerating. Some unknown force or "dark energy" is proposed to be operating to cause this acceleration.

No one has proposed what this energy is, nor does anyone have an idea of how it is produced. This "dark energy" is also related to the problem astronomers have had with the question of dark matter.

The "Dark Matter" problem has been known for quite some time in astronomy. Here is its essence: We can only observe the light from distant objects. Observations of stars orbiting around the centers of their galaxies and observations of clusters of galaxies revolving around each other around a center of mass like a swarm of bees suggest that there is much more gravity in these systems than is seen in visible light. Thanks to Newton and Einstein we are able to understand the celestial mechanics of motion based on gravitational influence of massive bodies and this has worked well enough to place space craft on the moon, around Jupiter and other exotic places so we are confident in that.

There is a problem though. When we combine the observed behavior of celestial objects acting under the influence of gravity and the amount of stellar mass implied because of the amount of light emitted by stars and gas that we see, there is a huge deficit.

The motion behaves as if there is a whole lot of mass around, the light emitted tells us that there is not a lot mass around. But we think this is the key. We only see luminous mass! There appears to be a lot of "dark matter" around. We measure its gravitational influence even if we can not see photons of light coming from it. This shouldn't be too bizarre because the earth and moon are forms of dark matter. They do not produce light, they only reflect the light from the sun.

The problem is in the size of this deficit. There is more dark matter than can reasonably be explained. If the dark matter is planets and asteroids, then the density of planets and asteroids would have to be enormously greater than what we have seen. If dark matter is some small atomic particle, then there must be so many of these particles around (compared to electrons, protons, etc.) that it upsets the physicists. What is this stuff? A question astronomers and physicists are wrestling with even as we speak.

It is estimated that only 10% of matter is luminous, and 90% is made up of "dark matter" in order to explain things in the universe we observe today.
http://imagine.gsfc.nasa.gov/docs/introduction/dark_matter.html
http://www.time.com/time/covers/1101010625/story.html


Current Queue | Current Queue for Astronomy | Astronomy archives

Try the links in the MadSci Library for more information on Astronomy.



MadSci Home | Information | Search | Random Knowledge Generator | MadSci Archives | Mad Library | MAD Labs | MAD FAQs | Ask a ? | Join Us! | Help Support MadSci


MadSci Network, webadmin@www.madsci.org
© 1995-2001. All rights reserved.