The Big Bang Theory Astronomers theorize that the universe came into being at a single moment in an event called the big bang. All matter and energy were concentrated in an incredibly hot region smaller than the period at the end of this sentence. Big bang theory states that the universe began in an instant, billions of years ago in an enormous explosion.

After the big bang The universe expanded quickly and cooled down After a few thousand years of expansion (smaller & hotter than now) cool enough for atoms to form Gravity pulled atoms together into gas clouds…stars…galaxies Sun & planets formed 4.6 billion years ago (universe was 2/3 size)

Evidence of Big Bang In 1965, Arno Penzias and Robert Wilson, using a radio telescope, noticed a faint distant glow in every direction. Today this glow is called the cosmic microwave background radiation. This glow is energy produced during the big bang, still traveling throughout the universe.

Continued Expansion Dark matter is matter that does not give off radiation. Galaxies like ours may contain as much as ten times more dark matter than visible matter. Without dark matter there would not be enough gravitational force to keep galaxies from flying apart.

In the past few years, astronomers have discovered that the rate of expansion of the universe may be increasing, theorized to be caused by a mysterious force called dark energy. If the expansion is accelerating, it’s likely that the universe will expand forever.

“How the Universe Works: Big Bang” 0c019529f623&fromMyDe=0&isPrinterFriendly=0&provider=&isLessonFromHealth=0&productcode=US&isAssigned=false&includeHeader=YES&homeworkGuid= 0c019529f623&fromMyDe=0&isPrinterFriendly=0&provider=&isLessonFromHealth=0&productcode=US&isAssigned=false&includeHeader=YES&homeworkGuid