braces_for_impact

Magus55:

Incorrect, that is not what he said. Perhaps you should read more carefully. Or do you 'interpret' people's post as you do biblical passages, so that you always come out to maximum advantage?

It constantly amazes me how this 'holy spirit' can interpret the conflicting, mistranslated, edited ancient book but can't help at all with regular everyday people.

Godless Dave

First, I didn't say the material has always been there. As far as what "set off' the big bang, we don't know the larger context (if any) in which our universe exists. Classical physics says we can't know, but quantum physics offers some possibilities we are just beginning to explore.

That's not what Paul2 said. Paul2 said this:
It is bad manners to misrepresent what someone else has said.


Do you really think hundreds of thousands of physicists would devote their professional lives to studying it if there weren't some evidence first? The cosmic background radiation is what led physicists to start taking it seriously. The only hypotheses to satisfactorily account for that radiation were the ones that included the Big Bang. I would need a PhD in physics to relate all the evidence to you accurately but you can get a good idea from The Universe in a Nutshell by Stephen Hawking.

Jesse

Magus55:
Not to mention, is there any actual evidence of the Big bang? Having an expanding universe doesn't count.

The theory of the Big Bang is the theory that the universe has been expanding from a superdense state--most physicists are agnostic/skeptical about whether there was really an initial singularity at t=0, whether it was the beginning of time, etc. Classical general relativity says these things are true, but most physicists think GR breaks down where singularities are concerned, and you'd need a theory of quantum gravity to know what was really happening in that first fraction of a second.

eh

See eternal inflation. The universe may have no beginning at all.

Magus55

There is no solid evidence for the Big Bang, thats why its a theory - you guys take how the universe was created on just as much faith as we take on God.

Asha'man

There is solid evidence for the Big Bang, we just told you what it is.

Cosmic Background Microwave Radiation.

Do a Google search, you might learn something in the process.

Do you know what the word theory means when used by a scientist? It doesn't mean wild guess, it means an explanation for observations that allows you to make testable predictions. According to that definition, the Big Bang theory has been proven: it has made predictions that have been verified.

Now, if you state that there is no evidence again, or that the Big Bang is "just a theory," I will have to ask you why you insist on bearing false witness, isn't there a commandment against that?

MyKell

I'm quoting from thislink

MyKell

I hope this answers your questions Magus... and yeah, follow the advice and learn what positivism is, and what a modern scientific theory is formulated

MyKell

I mean how

Tim Thompson

Magus55: Not to mention, is there any actual evidence of the Big bang? Having an expanding universe doesn't count.

Why doesn't an expanding universe count? Do you reject the crumpled wreckage of cars as evidence of a collision? "Evidence" is a convolution of observed facts & their interpretation. Systematic patterns of spectral redshift are observed facts. Interpretation of same as an indication of an expanding universe is well within the scope of physics as we know it, and therefore a perfectly valid interpretation. It is both unscientific and illogical (aside from just plain unreasonable) to insist that "an expanding universe doesn't count". It does count, and you can't avoid the issue by running from it like that.

There is copious evidence for a Big Bang. The expanding universe is one of the evidentiary points. It does not require the insight of the legendary rocket scientist to figure out that, if the universe is now expanding, then it must have in the past been smaller. There is a clear limit to smallness, hence the extrapolation from expansion observed to Bang implied. This is evidence for a Big Bang.

A super hot & dense early universe will promote the formation of nuclei from the fusion of protons and neutron capture. The application of physics to the problem leads to a calculation of the expected relative abundances of hydrogren, helium, deuterium, lithium & etc. The observed abundances are consistent with those computed from scenarios of Big Bang Nucleosynhtesis. This is evidence for a Big Bang.

As already mentioned, a key prediction of any Big Bang theory is that the universe should be filled with a thermal background radiation, which could range from as low as just above zero, to as high as 50 Kelvins (the theories by themselves are unable to constrain better than that). The observed roughly 3 Kelvin background temperature is consistent with the predictions that preceded its discovery. Furthermore, the distribution of temperature variations on the sky can be tied almost directly to large scale structure formation in the early universe (temperature fluctuations match the pattern of galactic cluster growth). Both of these features of the cosmic microwave background constitute evidence in favor of a Big Bang.

In general relativity (GR), the initial condition of the universe is necessarily singular (which means "undefined"). The first law argument is not applicable, because the first law of thermodynamics (conservation of energy) is a principle that applies inside the universe, and exists only after time itself exists. It does not necessarily apply outside the universe (there is no reason to assume the process of creating the universe must conserve energy), and it cannot apply where time does not exist (because it would be an undefinable constraint). Since the Bang under these conditions constitutes the true beginning of everything, including the first law of thermodynamics, it cannot be constrained by the not-yet-existing laws of nature.

However, it must also be pointed out that the hard line approach to the Bang being a true beginning is based on an overly literal interpretation of GR. Since we have long known that some quantized form of GR must be applicable, that opens the door to families of pre Big Bang cosmologies that I already addressed in an earlier message (the popular ones these days are based on string theory). Hence, in a modern cosmological setting, the Big Bang should not be viewed as a "true beginning", but only as an "apparent beginning", due to the limitations of our unique reference frame.

Here are some sources of further edification.

• Ned Wright's Cosmology tutorial.
• Cosmology 101 (from the WMAP mission).
• The Four Pillars of the Standard Cosmology (from the Cambridge Relativity Group).
• Big Bang Nucleosynthesis (Ned Wright).
• Review of Big Bang Nucleosynthesis and Primordial Abundances (from the Caltech Level5 Knowledgebase).
• Introduction to the Cosmic Microwave Background (Wayne Hu).
• Anisotropies in the Cosmic Microwave Background (Wayne Hu).
• A Tour of CMB physics (Wayne Hu).