By Alex J.

What is Dark Matter?

We are much more certain of what dark matter is not than what it is

It doesn't emit, reflect or absorb light Doesn’t seem to be composed of the

familiar electrons, neutrons and protons Some dark matter is probably composed

of black holes

Dark Matter Continued

Roughly 25% of the universe is dark matter

Best estimates of the total mass of everything that we can see with our telescopes is roughly 0.01 M

The other 99% is dark matter Astronomers know dark matter is there

by its gravitational effect on the matter that we see

What is Dark Energy?

In 1998 the Hubble Space Telescope that showed that, a long time ago, the Universe was actually expanding more slowly than it is today

The expansion of the universe hasn’t been slowing because of gravity like everyone thought, it has been accelerating

Roughly 70% of the universe is dark energy

Dark Energy Continued

Scientists have come up with three explanations for this accelerationIt could be a result of a version of Einstein's

theory of gravity, one that had what was called a "cosmological constant."

Or something is wrong with Einstein's theory of gravity, a new theory could include some kind of field that creates this acceleration

Scientists still don’t know the right explanation, but they gave it the name “dark energy”

Works Cited "Dark Energy, Dark Matter — NASA Science." NASA

Science. N.p., n.d. Web. 20 Jan. 2010. <http://nasascience.nasa.gov/astrophysics/what-is-dark-energy>.

"Dark matter detailed." The Why Files | The Science Behind the News. N.p., n.d. Web. 20 Jan. 2010. <http://whyfiles.org/092x_ray/4.html>.

"What is Dark Matter?." XS4ALL - internet, bellen en hosting. N.p., n.d. Web. 20 Jan. 2010. <http://www.xs4all.nl/~johanw/PhysFAQ/Relativity/GR/dark_matter.html>.

they, we know how long ago. "Dark Energy - Introduction." Imagine The Universe! Home Page. N.p., n.d. Web. 20 Jan. 2010. <http://imagine.gsfc.nasa.gov/docs/science/mysteries_l1/dark_energy.html>.