It is difficult enough to imagine a time, roughly 13.7 billion years ago, when the entire universe existed as a singularity. According to the big bang theory, one of the main contenders vying to explain how the universe came to be, all the matter in the cosmos -- all of space itself -- existed in a form smaller than a subatomic particle.
Once you think about that, an even more difficult question arises: What existed just before the big bang occurred?
The question itself predates modern cosmology by at least 1,600 years. Fourth-century theologian St. Augustine wrestled with the nature of God before the creation of the universe. His answer? Time was part of God's creation, and there simply was no "before" that a deity could call home.
Armed with the best physics of the 20th century, Albert Einstein came to very similar conclusions with his theory of relativity. Just consider the effect of mass on time. A planet's hefty mass warps time -- making time run a tiny bit slower for a human on Earth's surface than a satellite in orbit. The difference is too small to notice, but time even runs more slowly for someone standing next to a large boulder than it does for a person standing alone in a field. The pre-big bang singularity possessed all the mass in the universe, effectively bringing time to a standstill.
Following this line of logic, the title of this article is fundamentally flawed. According to Einstein's theory of relativity, time only came into being as that primordial singularity expanded toward its current size and shape.
Case closed? Far from it. This is one cosmological quandary that won't stay dead. In the decades following Einstein's death, the advent of quantum physics and a host of new theories resurrected questions about the pre-big bang universe. Keep reading to learn about some of them.
Branes, Crunches and Other Big Ideas
Here's a thought: What if our universe is but the offspring of another, older universe? Some astrophysicists speculate that this story is written in the relic radiation left over from the big bang: the cosmic microwave background (CMB).
Astronomers first observed the CMB in 1965, and it quickly created problems for the big bang theory -- problems that were subsequently addressed (for a while) in 1981 with the inflation theory. This theory entails an extremely rapid expansion of the universe in the first few moments of its existence. It also accounts for temperature and density fluctuations in the CMB, but dictates that those fluctuations should be uniform.
That's not the case. Recent mapping efforts actually suggest that the universe is lopsided, with more fluctuations in some areas than in others. Some cosmologists see this observation as supporting evidence that our universe formed out of a parent universe.
In chaotic inflation theory, this concept goes even deeper: an endless progression of inflationary bubbles, each becoming a universe, and each of these birthing even more inflationary bubbles in an immeasurable multiverse [source: Science News].
Still other models revolve around the formation of the pre-big bang singularity itself. If you think of black holes as cosmic trash compactors, they stand as prime candidates for all that primordial compression, so our expanding universe could theoretically be the white hole output from a black hole in another universe. A white hole is a hypothetical body that acts in the opposite manner of a black hole, giving off serious energy and matter rather than sucking it in. Think of it as a cosmic exhaust valve. Some scientists propose that our universe may have been born inside a black hole, and every black hole in our own universe could each contain separate universes as well.
Other scientists place the formation of the singularity inside a cycle called the big bounce in which our expanding universe will eventually collapse back in on itself in an event called the big crunch. A singularity once more, the universe will then expand in another big bang. This process would be eternal and, as such, every big bang and big crunch the universe ever experiences would be nothing but a rebirth into another phase of existence.
The last explanation we'll discuss also supports the idea of a cyclical universe, courtesy of string theory. It surmises that new matter and energy spring into existence every trillion years when two extra-dimensional membranes, or branes, collide in a zone outside our universe.
What existed before the big bang? It's still an open question. Perhaps nothing. Perhaps another universe or a different version of our own. Perhaps a sea of universes, each with a different set of laws dictating its physical reality.
Explore the links on the next page to tackle other lofty, cosmological questions.
Related HowStuffWorks Articles
More Great Links
- Atkinson, Nancy. "Thinking About Time Before the Big Bang." Universe Today. June 13, 2008. (April 28, 2010)http://www.universetoday.com/2008/06/13/thinking-about-time-before-the-big-bang/
- "Before Big Bang." AAAS Sciene NetLinks. 2010. (April 28, 2010)http://www.sciencenetlinks.com/sci_update.php?DocID=7
- Britt, Robert Roy. "'Brane-Storm' Challenges Part of Big Bang Theory." Space.com. April 18, 2001. (April 28, 2010)http://www.space.com/scienceastronomy/astronomy/bigbang_alternative_010413-1.html
- Davies, Paul. "What Happened Before the Big Bang?" God For the 21st Century. March 2000.
- "Every Black Hole Contains Another Universe?" National Geographic. April 9, 2010. (April 28, 2010)http://news.nationalgeographic.com/news/2010/04/100409-black-holes-alternate-universe-multiverse-einstein-wormholes/
- Kazan, Casey. "What Came 'Before' the Big Bang? Leading Physicists Present a Radical Theory." Daily Galaxy. Feb. 6, 2010. (April 28, 2010)http://www.dailygalaxy.com/my_weblog/2010/02/what-came-before-the-big-bang-two-of-the-worlds-leading-physicists-present-a-radical-theory.html
- Lintott, Chris. "Hints of 'time before Big Bang.'" BBC News. June 6, 2008. (April 28, 2010)http://news.bbc.co.uk/2/hi/science/nature/7440217.stm
- Marquit, Miranda. "The Branes Behind String Theory." Physorg.com. Oct. 2, 2006. (April 28, 2010)http://www.physorg.com/news79009171.html
- Moskowitz, Clara. "Glimpse Before Big Bang Possible." Space.com. Jan. 13, 2009. (April 28, 2010)http://www.space.com/scienceastronomy/090113-st-before-big-bang.html
- Overbye, Dennis. "Before the Big Bang, There Was… What? New York Times. May 22, 2001. (April 28, 2010)http://www.time.com/time/health/article/0,8599,1916055,00.html
- "Probing Question: What happened before the Big Bang?" Aug. 3, 2006. (April 28, 2010)http://www.physorg.com/news73844848.html
- Short, Nicholas M. Sr. "Remote Sensing Tutorial." March 1, 2010. (April 28, 2010)http://rst.gsfc.nasa.gov/Sect20/A10a.html
- "Test of Big Bang: The CMB." NASA Universe 101. April 16, 2010. (April 28, 2010)http://map.gsfc.nasa.gov/universe/bb_tests_cmb.html
- "Universe Offers 'Eternal Feast,' Cosmologist Says." Science Daily. Feb. 22, 2007. (April 28, 2010)http://www.sciencedaily.com/releases/2007/02/070221093222.htm
- "What is the Inflation Theory?" NASA Universe 101. April 16, 2010. (April 28, 2010)http://map.gsfc.nasa.gov/universe/bb_cosmo_infl.html