Did the Big Bang really occur?  Is this not just one possible interpretation of the "evidence"?

Why do you want alternative explanations?  The universe could have been created 5 min ago with just the right attributes to make it look as it does now; you cannot know otherwise.  Indeed, you live only in the current instant, and the past is just models and memories.  Science only provides reliable models that are useful for prediction and control of the natural world.  Your decision to use any particular model is a value judgment.  The question of whether "the Big Bang really occur[red]" is beyond the scope of science. On the other hand, Astronomy does present some miracles for which useful models do not yet exist.  Dark Energy clearly violates the conservation of energy; what is pumping the universe?  'Cosmological constant' explanations are lame.  How can supermassive black holes exist in the universe only a few hundred million years after the Big Bang?  Why does it appear that the Big Bang occurred at all, and what triggered it? The Big Bang is not an 'assumption'; it is a model that provides useful predictions, but it is incomplete and inadequate.  The contradictions should indeed bother you.

Sure.  The trouble is that all of this was argued to death in the early 1970's.  Unless someone has some *specific* reason why we missed something, there's really not much to do here, and the more stuff that we see, the more it seems that the big bang really happened. At this point trying to argue that the big bang didn't happen is like arguing that America doesn't exist.  It's plausible in 1500, that Columbus ended up in Asia, but at this point there's just too much evidence (like baryon acoustic oscillations).

The proof is in the math. What more do you need other than complex math? If the universe is expanding then it is expanding from somewhere. If we take all we know about matter and its interactions and combine it with our best theories of thermodynamics and plasma physics etc, we then just reverse engineer the universe to its starting point. Bang! All you need is math.

Let me begin by saying this is my opinion and/or quandary over this question and its usual answers. I am NOT advocating or proposing that the big bang is dead wrong and I am definitely not suggesting that it was divine intervention that created the universe. However, I really dislike a theory that is widely supported by people that selectively use confirming evidence and interpretations and conveniently ignore conflicting evidence and alternative interpretations.  Science is not a democracy - we do not get to vote on what is true about nature.In my opinion, the big bang theory has evolved to the point of being "conventional wisdom", "accepted thoughts", "the only rational explanation" and "essentially established fact".  It is also a fact that anyone that challenges the big bang theory is labeled a quack or dismissed as a kook.  A few reports pop up every year that attempt to offer an alternative view but they are quickly shouted down and condemned and almost always cannot get their reports accepted for publication in scientific journals.I won't attempt to tell you that the big bang theory is wrong but I would like to offer you some food for thought.  I welcome anyone that can to respond with some explanation of some of the issues I raise.I have read about the big bang for a long time and if you read carefully, you will see that what we actually did was back in a theory based on seeing the end result.  That is, Hubble saw an expanding universe so we surmise it must have been smaller in times past.  We can see out into space (back in time) for about 13.7 billion light years (BLYs) so that must have been how long ago the big bang (BB) happened.  Then we ran a lot of math and looked for compliance in our observations - like the CMBR, the mixture of elements (neucleogensis) such as the helium-to-hydrogen ratios, and the latest being the primordial B-mode polarization - and we found it.  These all are confirming evidence of the BB theory.Unfortunately, we also found some verifiable evidence that cannot be explained by the BB theory.  For instance, there is an imbalance of matter and anti-matter and there is much less lithium than there should be.  Some other inconsistencies are so complex that they usually go by names such as the horizon problem, the flatness problem and the monopole problem.  (look them up)  There are others.And then there is the simple matter of timing of the BB.  If we see the universe is expanding and theorize that it must have been smaller in the past, wouldn't it be necessary to know how large it is now in order to project how long it took it to expand to its present size?  Even at speed C.  We can not see past 13.7 BLY out but for a variety of reasons (see this link:  https://en.wikipedia.org/wiki/Observable_universe ), the observable diameter of the universe is actually about 93 billion light years and the diameter of the whole universe beyond that can be seen may be as large as 3 x 10 (to the 23 power) times larger than 93 BLYs.  That is a large number but the difference (between that large number and 13.7) is explained, not by the BB but by the expansion of space itself by some, as yet, unknown process.One other interesting fallacy is related to the cosmological constant.  The error between observation and calculated (conjectured) vacuum energy of space is a factor of 1 x 10 to the 120th power.  That is the largest error between theory and observation of anything in any science.  This is called the  https://en.wikipedia.org/wiki/Vacuum_catastrophe .  It is hard to relate to the size of this error, it is so big.Proponents of the BB theory have lots of answers for these discrepancies.  The size of the universe is satisfied by adding in an "expansion phase" of undefined amount and process that gives us what we have today.  They have introduced dark energy and dark matter to make up for a huge discrepancy between observation and theory.  Specifically, that 96% of the entire universe is either undetected, unexplained or unknown.  They claim that all laws of physics break down at the moment of the BB so we can explain some things that defy nature by saying that during the BB, the present laws of nature do not apply.  Conflicting issues of entropy and problems with the first law of thermodynamics fall into this category.Although it is true in much of human affairs (politics, economics, religion, biology, etc.), it seems to me that there is something wrong when the "conventional wisdom", "accepted theory" and "essentially established fact" does, in fact, NOT explain all of the observed, empirical evidence that contradicts that line of thinking.What most people do not know is that there are at least 32 different versions of the BB theory. Use FIND at http://www.cosmologyscience.com/glossary.htm#Math to look up "cosmology models".  I don't mean alternative views like static state, creation or plasma model.  I mean different math, mechanisms and models of the big bang itself.  Each one has flaws or fails to explain some observation or calculation but otherwise use different evidence and interpretations in the same manner as all the others do but resulting in different models.As a scientist, I consider the BB theory to be the best we have at the moment but I strongly believe that we are missing something.  We don't yet have the whole picture and the part that is missing may be that we got it all wrong.  In my opinion.

"The Big Bang" is an expression used to ridicule those who didn't accept the steady-state universe.  There was no "bang", there wasprobably a rapid expansion of spacetime (possibly starting with nothing).  Since space was totally opaque at that time, we can't see what happened, we can only theorize, based on what we see from about 400,000 years later (when the universe cooled down enough that light could get through).

There are alternative explanations for all cosmological observations, for example, that galactic redshifts are the result of a scattering process rather than expanding space, and the CMB is the black-body radiation emitted by matter in the intergalactic medium which has a minimum temperature of 2.7°K under the glare of the universe's light. There is a lot of bias in science so the prevailing theories are not necessarily the better supported theories, but simply the conventionally preferred ones.  Research into alternatives to the standard model tends to be discouraged.  There is a good documentary here that gives a good example of this... http://bit.ly/sv3MGo