The "big bang"?

Question

What triggered the "big bang" and what existed before it?

Answer 1

In physical cosmology, the Big Bang is the scientific theory that the universe emerged from a tremendously dense and hot state about 13.7 billion years ago. The theory is based on the observations indicating the expansion of space (in accord with the Robertson-Walker model of general relativity) as indicated by the Hubble redshift of distant galaxies taken together with the cosmological principle.

Extrapolated into the past, these observations show that the universe has expanded from a state in which all the matter and energy in the universe was at an immense temperature and density. Physicists do not widely agree on what happened before this, although general relativity predicts a gravitational singularity (for reporting on some of the more notable speculation on this issue, see cosmogony).

The term Big Bang is used both in a narrow sense to refer to a point in time when the observed expansion of the universe (Hubble's law) began — calculated to be 13.7 billion (1.37 × 1010) years ago (±2%) — and in a more general sense to refer to the prevailing cosmological paradigm explaining the origin and expansion of the universe, as well as the composition of primordial matter through nucleosynthesis as predicted by the Alpher-Bethe-Gamow theory.

From this model, George Gamow in 1948 was able to predict, at least qualitatively, the existence of cosmic microwave background radiation (CMB).The CMB was discovered in 1964 and further corroborated the Big Bang theory, giving it an additional advantage over its chief rival, the steady state theory.

The Big Bang theory developed from observations of the structure of the universe and from theoretical considerations. Observers determined that most "spiral nebulae" were receding from Earth; but the observers themselves were unaware of the cosmological implications of this fact, or that the supposed nebulae were actually galaxies outside our own Milky Way. Georges Lemaître, a Belgian Roman Catholic priest, independently derived the Friedmann-Lemaître-Robertson-Walker equations from Albert Einstein's equations of general relativity in 1927 and proposed, on the basis of the recession of spiral nebulae, that the universe began as a simple "primeval atom"—what was later called the Big Bang.

Soon after, in 1929, Edwin Hubble provided an observational basis for Lemaître's theory. He discovered that, seen from Earth, light from other galaxies is redshifted proportionally to their distance from Earth. This fact is now known as Hubble's law. Given the cosmological principle whereby the universe, when viewed on sufficiently large distance scales, has no preferred directions or preferred places, Hubble's law implied that the universe was expanding, contradicting the infinite and unchanging static universe scenario developed by Einstein.


Artist's depiction of the WMAP satellite gathering data to help scientists understand the Big Bang.This idea allowed for two distinct possibilities. One possibility was Fred Hoyle's steady state model whereby new matter would be created as the universe seemed to expand. In this model, the universe is roughly the same at any point in time.The other was Lemaître's Big Bang theory, advocated and developed by George Gamow. It was actually Hoyle who coined the name of Lemaître's theory, referring to it sarcastically as "this big bang idea" during a program broadcast on March 28, 1949, by the BBC Third Programme. Hoyle repeated the term in further broadcasts in early 1950, as part of a series of five lectures entitled The Nature of Things. The text of each lecture was published in The Listener a week after the broadcast, the first time that the term "big bang" appeared in print. While Hoyle's "steady state" and Lemaître's "Big Bang" were the two most popular models used to explain Hubble's observations, other ideas were also proposed. Some of these alternatives included the Milne model, Richard Tolman's oscillatory universe, and Fritz Zwicky's tired light hypothesis.

For a while, support was split between the "steady state" and "Big Bang" theories. However, the observational evidence eventually began to favor the latter. The discovery of the cosmic microwave background radiation in 1964 secured its place as the best theory of the origin and evolution of the cosmos. Much of the current work in cosmology includes understanding how galaxies form in the context of the Big Bang, understanding what happened at the Big Bang and reconciling observations with the basic theory.

Huge advances in Big Bang cosmology were made in the late 1990s and the early 21st century as a result of major advances in telescope technology in combination with large amounts of satellite data such as that from COBE, the Hubble Space Telescope and WMAP. Such data have allowed cosmologists to calculate many of the parameters of the Big Bang to a new level of precision and led to the unexpected discovery that the expansion of the universe appears to be accelerating.

Answer 2

No one knows what triggered the Big Bang.

Since "time" itself began with the Big Bang, there was no "before" the Big Bang. I realize this is difficult to imagine, but that is the current state of scientific knowledge on the topic.

Answer 3

What triggered it? No one knows. This is why a lot of scientists are uncomfortable with the Big Bang theory -- with a big bang, you have to deal with the question of what set it off. Many scientists are atheists or agnostics, and they don't much like the idea of a scientific theory that points to the possibility of what they euphemistically call the First Cause (iow, God).

What existed before it? All of the matter, energy and space in what would become our universe, compacted into a single point. So says the theory, anyway.

Answer 4

Ah, this is the ultimate scientific/philosophical question. Essentially, what you're asking is "how did existence begin"? Is it possible that something (like the universe) has always existed, but that leads to the question of how something could not have a beginning. A puzzle for the ages, to be sure.

Answer 5

There is no right answer to your question as of yet... I like several of the suggestions here... it was interesting to see what other people's thoughts were on the subject (besides the religious people that feel they need to inject faith into science). I especially like the one from the 18 year old - as he said, it is short and sweet and it is kind of comforting (as opposed to the theory that the universe will continue to drifting appart into nothingness).... I don't have anything usefull to add.

Answer 6

When your blind date that your best friend set you up outweighs the entire 5th platoon in Iraq. A credit card bill is always better smaller. Glenfiditch scotch and a good game of poker sounds like a cool way to enjoy the evening.

Answer 7

Hi. Both questions are not known and may be unknowable. My opinion is that this is only one in an infinites series of events (I hate the term "Big Bang") with each one destroying all evidence of prior events.

Answer 8

My personal 18 year odl opioion is the universe was sucked into a giant black hole. Which over loaded the black hole which caused it to exploded, hence the multiverse. Short and Sweet.

Answer 9

The "big bang" sure, God said it and Bang! it happend.

Answer 10

Cosmologists are trying to answer those very questions.