Matter of Density

The reason for these limited options comes down to the density of the universe. If the universe contains a sufficient amount of matter—is sufficiently dense— then the force of gravity will be such that it will eventually succeed in halting expansion. The universe will gradually expand at a slower and slower rate, and then reverse itself and begin to collapse. If the universe (even counting all of the material that we can't see— the dark matter) does not contain sufficient mass—is too gruelly and thin—the expansion of the universe will continue forever.

Remember that in the Big Bang theory, there is no such thing as new or old matter. All the matter there is was created as a result of the Big Bang; therefore, the density of the universe—and its fate—was determined at the moment the Big Bang occurred.

There is a certain density of matter in the universe that is the sword edge between ultimate collapse and eternal expansion. This critical density has been calculated. If the universe is more dense than this, it will eventually collapse. If it is less dense than this, it will expand forever, and if it is exactly this dense, it will keep expanding, more and more slowly, forever.

Close Encounter

Close Encounter

Some recent discoveries have a bearing on the question of the eventual fate of the universe. Two groups of astronomers using the Hubble Space Telescope (one at the Harvard-Smithsonian Center for Astrophysics, and the other at Berkeley Labs) have found evidence that the universe is likely to expand forever, that the universe does not have enough mass in it to cause the expansion to halt.

They have used what are called Type Ia supernovae (cataclysmic explosions that result when a white dwarf star borrows a bit too much material from its binary companion) as standard candles. Type Ia supernovae are so incredibly luminous that they allow us to see farther than just about any other phenomenon we know of. Using these supernovae, the astronomers have determined that the expansion of the universe (as described by Hubble's Law) doesn't seem to be slowing down at all. In fact, it may be accelerating.

Telescopes Mastery

Telescopes Mastery

Through this ebook, you are going to learn what you will need to know all about the telescopes that can provide a fun and rewarding hobby for you and your family!

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