Dark matter and dark energy make up about 95% of our universe› 70% is dark energy› 25% is dark matter› 5% is normal, visible matter

Know more about what it isn't than what it is› Not readily visible› It's dark

Meaning that it's not visible like stars and planets It doesn't reflect or emit electromagnetic

radiation› Can only be detected indirectly› May consist of…

Dust Planets Black holes Dwarf stars Clouds of gas that don’t light up

Astronomers know dark matter is there by its gravitational effect on the matter that we see, and there are ideas about the kinds of particles it must be made of

More is unknown than known We know how much dark energy

there is because we know how it affects the Universe's expansion

People were sure that gravity was going to slow the expansion of the universe

In 1998, the Hubble Space Telescope came along and observed distant supernovae that showed that the universe was expanding slower than it is now a long time ago› People came up with 3 theories

Result of a long-discarded version of Einstein's theory of gravity

There was some strange kind of energy-fluid that filled space

There is something wrong with Einstein's theory of gravity Scientists still don't know which theory is

correct, but they named the solution dark energy

Dark energy proves that the universe will keep expanding

Scientists have more to learn about dark matter and dark energy, which will keep them studying for years

"Dark Energy, Dark Matter — NASA Science." NASA Science. N.p., n.d. Web. 27 Jan. 2010. <http://nasascience.nasa.gov/astrophysics/what-is-dark-energy>.

"dark matter — Infoplease.com." Infoplease: Encyclopedia, Almanac, Atlas, Biographies, Dictionary, Thesaurus. Free online reference, research & homework help. — Infoplease.com. N.p., n.d. Web. 25 Jan. 2010. <http://www.infoplease.com/ce6/sci/A0814671.html>.

"dark matter: meaning and definitions — Infoplease.com." Dictionary Search Page — Infoplease.com. N.p., n.d. Web. 25 Jan. 2010. <http://dictionary.infoplease.com/dark-matter>.

"Dark matter." Science Daily: News & Articles in Science, Health, Environment & Technology. N.p., n.d. Web. 27 Jan. 2010. <http://www.sciencedaily.com/articles/d/dark_matter.htm>.

Farndon, John. From Ptolemy's Spheres to Dark Energy: Discovering the Universe (Chain Reactions). Chicago: Heinemann, 2007. Print.

"Invisible universe: interview with George Smoot - | unesco.org." UNESCO. N.p., n.d. Web. 29 Jan. 2010. <http://portal.unesco.org/en/ev.php-URL_ID=46036&URL_DO=DO_TOPIC&URL_SECTION=201.html>.

Sparrow, Giles. Observing the Universe (Secrets of the Universe). Milwaukee: World Almanac Library, 2006. Print.