What is big bang theory?

Answer 1

the big bang theory states that the universe began at some time, and was much smaller and hotter and has expanded and cooled since its origin. there is much evidence for it, and it is generally accepted.

the evidence is that the universe is 13 700 000 000 (13.7 billion) years old.

the origin of the universe was not an explosion of matter in empty space-time, but space-time itself seems to originated in the big bang. nothing, not even space-time exists "outside" the universe. the universe has no center and no edge. it is four-dimensional, but if you can imagine a two-dimensional version then it seems to be something like the surface of a sphere. it is this surface that is expanding.

the name itself comes from a dismissive remark by fred hoyle on BBC radio in 1949.

here is a lot of information:
http://www.sciam.com/print_version.cfm?articleID=0009F0CA-C523-1213-852383414B7F0147
http://en.wikipedia.org/wiki/Physical_cosmology
http://universeadventure.org/

Answer 2

Well... I challenge the big bang theory. The universe looks like soap bubbles clumped together and just like with soap, matter (star and galaxies) exist only where the bubbles touches each other, thus the center of each bubble is empty space created by some sort of pressure wave. Each bubble is growing because of this pressure wave in each bubble so the universe expand. What happens when on bubble collapse? The space is reorganized to accommodate the existing bubbles and the process continue for ever. Where did the bubbles came from? Who knows. My point, the big bang theory suggest a point of origin which contradicts the current model of the universe. If the big bang theory is correct, then how can we explain that the matter in the universe is arranged in filaments of galaxies that look like the soap lines around clumped soap bubbles? Trying to make sense of something that doesn't make sense is an exercise in futility.

Answer 3

big bang theory was a cosmological theory were the universe are being formed in terms of big explosion of gases.Big bang emanated from a previous universe and that a temperature in excess of one billion degrees was necessary to create our new universe. This energy would in turn produce an infinitesimal amount of radiation that should be measurable to this day. Big Bang model that attempts to explain the origin and structure of the universe incorporates the talents of many individuals through the course of more than 150 years of study. Many times facing opposition similar to that of Galileo and Copurnicus, these cosmologists used a deductive approach in solving the greatest question in the history of science. The findings and observations of these emminant scholars forced them to draw the conclusions they arrived at. Every prediction that quantum physics and the theories of relativity have made regarding the origin and the state of the universe have either been observed and confirmed and/or not proven to be false. That is in essence the reason we have arrived at this cosmology, fully confident that our science and technology can look back in time 15 billion years and see the birth of our universe.

Answer 4

The Big Bang Theory is the dominant scientific theory about the origin of the universe

Answer 5

Officially called the "primeval atom" is a cosmological theory that describes how the universe we live in and the laws that govern it have began and developed.

Our universe began in a hot dense state which began, and still is expanding. In this initial event, all the matter in our universe was created with approximately 80% hydrogen and 20% helium.

The Big Bang theory does have a good amount of evidence behind it. So we’ll take a look at the three biggies.

a) Cosmological Redshift: As I explained in my earlier post, we can use spectroscopy to determine the rate at which galaxies are moving away from us. Additionally, since it takes light time to travel, the further away we look, the further back in time we are looking.

What we find, is that all galaxies in the universe are moving away from us. The further they are, the faster they’re moving away. So if we play the whole thing in reverse, all the galaxies will come back together at a single point in time. This point in time is what we call the Big Bang.

b) The Cosmic Microwave Background (CMB): Figuring that if you played everything back in time like this that all that energy would be crammed into a smaller space, that means the temperature would go up. And also since galaxies couldn’t have formed yet, we’d expect a gaseous sort of universe early on. As I discussed earlier, hot dense gasses emit photons at a peak wavelength corresponding to their temperature. Unfortunately, since things were so dense, photons couldn’t get very far.

However, with the available information, astronomers were able to determine at what density and time, photons would finally be able to get far enough that we could observe them. This is called the “surface of last scattering” and has a very specific temperature. So we should be able to look for photons with energy (wavelength) corresponding to that temperature.

But due to redshift, they will appear at a different wavelength. This radiation should appear from every direction. This was a prediction made by the Big Bang theory that was later confirmed by Penzias and Wilson who stumbled on it accidentally!

No other theory of the universe has ever been able to make such a profound prediction to the degree of accuracy the Big Bang did in this instance. Making such amazing predictions is one of the highlights of a good theory. None before or since have ever been able to pull off such a feat.

But the successes of the CMB prediction don’t stop there. Another important piece of the puzzle lies in that the CMB couldn’t be completely even. If it were, then galaxies couldn’t form since there would be no “seeds” with higher mass and thus a stronger gravitational pull to form around.

Thus, the Big Bang theory had to predict that the CMB would not be completely homogeneous. It should have some variations to it, and those variations would have to be of a specific size in order to get the universe we see today.

Early results for the Big Bang didn’t look too good for this prediction and threatened to sink the whole ship. However, the devices used were not actually sensitive enough to pick up these minute variations. But recently, with the Wilkinson Microwave Anisotropy Probe (WMAP), these perturbations have been discovered precisely as predicted.

Score two strong predictions for the Big Bang. Zero for any others.

c) Distribution of Elements: With the conceptual framework intact thanks to the first point, it was also possible to calculate how much of each element should be formed in the initial event. It should be obvious that, given a bunch of protons, electrons, and neutrons, hydrogen should be the easiest to form. Indeed, stick a proton and an electron in a room together and they’ll automatically hook up due to their magnetic attractions.

Additionally, with such high energies, it would be possible to fuse some of this hydrogen into helium and even a little bit of heavier elements. Since astronomers had a good handle on the energies, it was possible to calculate how much of each there should be. If that number didn’t match up with observations, the Big Bang theory would be shot.

Fortunately, the predictions do match up pretty closely. I stated a value earlier of 80% hydrogen, 20% helium, and neglected the rest since it would be statistically insignificant. In the universe today, we observe 75% hydrogen, 24% helium, and 1% everything else. This discrepancy is easily accounted for by nearly 14 billion years of stars cooking hydrogen into helium and other heavier elements.

So there’s three major pieces of evidence for the Big Bang, any one of which, if it had turned out any other way, would completely discredit the theory. Fortunately for the Big Bang, it has passed all of those tests, and not a single other theory has yet been able to adequately explain such things, or many anywhere near as profound of predictions (or any successful predictions for that matter). This is why the Big Bang stands alone as the premiere theory in cosmology today.

Answer 6

In physical cosmology, the Big Bang is the scientific theory of how the universe emerged from a tremendously dense and hot state about 13.7 billion years ago.

Answer 7

Sceintists have shown that all of the universe began when matter was compressed into a single mass and then exploded, throwing matter and gas out to form the millions of galaxies. So they called it the "big bang" for short. That was about 5 billion years ago.

Answer 8

The big band theory states that all matter started out in a singualrity that all of a sudden,decided to expand and turn inot our universe.

Answer 9

That the known universe originated in a huge explosion of matter and energy that is still expanding to this day.

Answer 10

It is the theory of how the universe was born from a giant explosion that made the first stars.

http://liftoff.msfc.nasa.gov/academy/universe/b_bang.html