How was the Big Bang theory proven?

Question

Any astrophysicists out there want to explain this to me?

Answer 1

Scientific theories are never fully "proven," but the circumstantial evidence builds up and up (or not) until most relevant scientists think it's a pretty compelling case, though there are frequently diehard opponents who'll never accept that.

Yes, the Big Bang was suggested to explain the astronomer Edwin Hubble's observations that the Universe was expanding, observations made back in the 1910's and 1920's.

The first generally accepted additional evidence for something like the Big Bang came when the "~ 3 degree cosmic microwave background radiation" was discovered by Penzias and Wilson, and published in 1965. (But still, alternative explanations were, and are being, made for that!)

A largely neglected prediction for the temperature of such "dying radiation" left over by the Big Bang had already been made in the 1940's by George Gamow and his students. With the values for things like Hubble's (Galaxy Expansion) Constant then current, their prediction for such relict radiation had been ~ 20 degrees; the resurrected result, with 1965 values for the inputs, indeed gave ~3 degrees, remarkably close to the observed value! (Dicke et al at Princeton had unwittingly reproduced Gamow's kind of calculation, and were trying to build detectors to look for the radiation. Ironically, their goal oriented research was pipped at the post by Penzias and Wilson, working only 30 miles away, who didn't initially know where the "noise" in their antenna was coming from. Dicke is reported to have said "Boys, we've been scooped!" to his team when he heard of the discovery by telephone.)

A further consequence of a Big Bang origin (with present day values for the Hubble Constant) is that something like 77% hydrogen and 23% helium, but only the merest smidgen of other elements, should emerge, theoretically, out of the Big Bang.

Something like that had ALSO been calculated earlier but gone largely unnoticed, by Hayashi in Japan. In 1964 Hoyle and Tayler in England repeated that calculation (not realizing initially that Hayashi had done it before). Their calculation was performed about a year before the background radiation was discovered.

The latter calculation in particular was in the context that one seemed to see substantial helium around, even in the oldest objects. (Hoyle's own Steady State theory had assumed that the simplest thing to create would be hydrogen --- so why was it that we never seemed to find anything with less than some fairly substantial baseline of helium, much more than we'd expect to find from H ---> He conversion in stars?)

The ability to make such element abundance predictions, that agree with observations, is taken to be yet more confirmation of the general correctness of the theory. Indeed, one "smidgen" Big Bang consequence, the abundance of Deuterium or heavy hydrogen, is avidly pursued in absorption lines in deepest intergalactic space, where stars won't have (easily) burnt it. Measured values of that are now used as a very fine test of the Big Bang theory. (I happen to think that the proponents of this approach often push the supposed accuracy of astronomical abundances, certainly like that of helium in stars, way too far; but that's just my personal and perhaps cynical opinion.)

Big Bang proponents would also claim many other successes for their theory. Space limits saying much more, but key words or concepts are: the formation of structure (superclusters or clusters of galaxies, galaxies, etc. in an EXPANDING universe), the "fingerprints of God" (extremely fine ripples in that same microwave background), "cosmic echoes" (distinct patterns in structure correlations due to the equivalent of cosmic sound waves echoing back and forth in an expanding, cooling down Universe), "Boomerang" or "WMAP," two very significant observational experiments in the last decade or so, etc. If we are to believe the interpretetion of the latter experiment, we now "KNOW" that our Universe came into existence 13.73 billion years ago. (Want to buy the Brooklyn Bridge? --- check my sale on eBay.)

However, in order to explain many of the details in the last paragraph, the original, simple Big Bang picture has had to have a lot added to it: "cosmic inflation," "dark matter," "biasing," "dark energy"; the list may go on and on. Does this mean that every new discovery needs a new explanation, or simply that we're lerarning more details within a generally correct theory? I'll leave you to be the judge of that.

Live long and prosper.

Answer 2

One of the pieces of supporting evidence is that scientists have proved through observation, that every object in the universe is moving away from everything else.

This supports the theory that everything started in one central point and exploded outwards and that the universe is expanding.

If the universe was in a steady states then the celstial bodies would not be moving away from each other.

The way scientists have proved this is by meauring the dopler shift in light from various stars. The dopler effect occurs when a wave emiiting source moves relative to the obervers position. It is noted that there is a change in frequency in the emitted wave compared to that expected.

An example of this that everybody can relate to is a police car siren changing pitch as it fles past you. The same effect applies to the electomagnetic spectrum.

By measuring the doppler effect on stars scientists can calculate the relative velocities of starts to one another and which direction they are moving, by using the amount of shift and whether the shift is to the blue or red end of the spectrum.

Using observations and applying this technique they can produce evidence to support that everything exploded from one central point.

Answer 3

Details are sketchy, but as far as I know, the most solid evidence of the Big Bang was leftover microwave radiation. It's a funny story.
Some guys were using their special astronomy radios when they got some static. So they went outside to clean their antenna, thinking it was mere bird poop that was giving them the static. They went back inside, and the static was still there. It turns out that the static was the leftover radiation from the Big Bang!
As far as I can assume, that radiation was dated a little over 14 billion years, give or take 2 or 3 billion; this happens to be around the time that astronomers predicted the Big Bang was!
Go figure. They though it was bird poop.

Answer 4

Dr. Spock has the correct answer.

I am getting sick to death of all of the people who are saying that such and such is a "theory" and therefore not proven. This is a complete misunderstanding of the meaning of the term "theory" as used in science. I suppose that Newton's theory of universal gravitation has not been proven. Wait - I see people spontaneously flying off the earth. I guess gravity isn't real.

Answer 5

It might not be proven, but the big evidence was from Hubble, who found the universe was expanding (by measuring red shifts of the various stars and galaxies). Since it is expanding, it must have been smaller in the past, hence if you go back far enough, it must have come from something very small. The theory is it started very small and with a big bang.

Answer 6

Originally, the theory was created because radio astronomers were trying to fine tune their receiver and they kept getting a low energy "noise". Everywhere they pointed the antenna, the "noise" was there. They thought it was electrical or interference from somewhere close. After investigation, the source was outer space. The residual energy from the "Big Bang".

Answer 7

Cosmic microwave background radiation provided strong evidence, but it is not 100% proven yet. Also the fact that the universe is expanding provides evidence that it was once compact.

Answer 8

It hasn't been, that's why it's a theory, not a scientific law. The big bang is used to explain the most likely explanation for the solar system at this point. Its based on having a proton, something about 500,000,000,000 smaller than the dot on this "i". Shrink a proton to one-billionth of its original size, then stuff everything from here to the end of creation inside that proton. A really big bang will occur.

Answer 9

One of your previous answerers got it right. Check out www.space.com for tons of interesting articles on this and other astronomical subjects. One of my favorite sites!

Expand that mind!

Answer 10

It's not 'proven'.
Hence the fact why it's a theory.