ADVERTISEMENT
See Inside September 2009

The Origin of the Universe

Cosmologists are closing in on the ultimate processes that created and shaped the universe

More In This Article

The universe is big in both space and time and, for much of humankind’s history, was beyond the reach of our instruments and our minds. That changed dramatically in the 20th century. The advances were driven equally by powerful ideas—from Einstein’s general relativity to modern theories of the elementary particles—and powerful instruments—from the 100- and 200-inch reflectors that George Ellery Hale built, which took us beyond our Milky Way galaxy, to the Hubble Space Telescope, which has taken us back to the birth of galaxies. Over the past 20 years the pace of progress has accelerated with the realization that dark matter is not made of ordinary atoms, the discovery of dark energy, and the dawning of bold ideas such as cosmic inflation and the multiverse.

The universe of 100 years ago was simple: eternal, unchanging, consisting of a single galaxy, containing a few million visible stars. The picture today is more complete and much richer. The cosmos began 13.7 billion years ago with the big bang. A fraction of a second after the beginning, the universe was a hot, formless soup of the most elementary particles, quarks and leptons. As it expanded and cooled, layer on layer of structure developed: neutrons and protons, atomic nuclei, atoms, stars, galaxies, clusters of galaxies, and finally superclusters. The observable part of the universe is now inhabited by 100 billion galaxies, each containing 100 billion stars and probably a similar number of planets. Galaxies themselves are held together by the gravity of the mysterious dark matter. The universe continues to expand and indeed does so at an accelerating pace, driven by dark energy, an even more mysterious form of energy whose gravitational force repels rather than attracts.

This is only a preview. Get the rest of this article now!

Select an option below:

Customer Sign In

*You must have purchased this issue or have a qualifying subscription to access this content


It has been identified that the institution you are trying to access this article from has institutional site license access to Scientific American on nature.com.
Click here to access this article in its entirety through site license access.

Rights & Permissions
Share this Article:

Comments

You must sign in or register as a ScientificAmerican.com member to submit a comment.
Scientific American Dinosaurs

Get Total Access to our Digital Anthology

1,200 Articles

Order Now - Just $39! >

X

Email this Article

X