People often ask themselves how the universe was created. Well, the universe was not created. It doesn't have a creator - just is. The explanation of this on scientific grounds is rather simple, without going for obvious reasons in details. Thus, it can perfectly be illustrated on absurd considerations on SOMETHING and its “complement” or NOTHING. If we assume that there is NOTHING that means automatically, there is no time / motion / change of anything. NOTHING is inconceivable, because the concept represents absence of any physical entity, including also the lack of space. If indeed there was nothing, or “would be” only NOTHING, then you could not determine how long such a state of nature / non-nature was. In a word, when NOTHING could have a start time of its non-existence. So it is in nature, that there occur in it polarities, such as:
positive charge - negative charge
brightness - darkness
inside - outside
and countless oppositions
and the most essential, primordial SOMETHING - NOTHING
The Universe / Nature is the real entity. So by this, there is SOMETHING. And as previously mentioned antipodes exist side by side complementary, so SOMETHING and NOTHING cannot be exceptions. It means that SOMETHING cannot have the beginning of time of its existence. Now the question may arise, but what was SOMETHING? Well, the primordial SOMETHING was (and still is, but in a different proportion to the evolved forms of physical entities), the simplest, elementary physical entity, which forms a threshold that cannot be crossed. Because nothing can come from NOTHING, while SOMETHING can give rise to more complex forms of something. In short, causality must have its limit. If it didn't have, nothing could be started, because it would be an endless string of causes! Can we therefore say that something was eternal? No. Despite the fact that eternity is commonly understood as the measure of time of something that exists infinitely long, it loses its sense in relation to prematerial state of nature, because time (of something) means change (of something). Since there were no changes, then we cannot say anything about time. What was SOMETHING can be explained, but it is a separate and longer story. There was therefore no time / change of SOMETHING. Time was delivered along with matter, so it had its beginning: WAS-IS-WILL_BE - with matter of course.
Anticipating possible questions on infinity of time, I would like to emphasize that infinity occurs only in mathematics, as for example continual string of numbers. But what infinity for physics could look like? Could we interpret it as a continual string... - but of what? Time? Nonsense! Time / motion / change does not occur spontaneously in nature! It was, therefore, a state of nature (timelessness) in which there were no changes. Thus, with regard to the future we can say that it can be forever - the perpetual motion of matter and its evolution (provided matter won't change its state to prematerial one, which in my opinion is rather unlikely).
Conclusion: SOMETHING does not have the time point of its occurrence. However, the material world was created by accident. I'd like to stress explicitly that since the moment of birth of matter (from prematter – could be referred to as ether), time (changes) came into being as the inseparable attribute of matter.
In a nutshell: As NOTHING cannot create SOMETHING (and SOMETHING cannot turn to NOTHING), the materialized part of the universe was delivered by primordial, filled with ether space, and not by alleged Big Bang as nothing could exist without space. Moreover, there is no rational explanation of the cause that was able to compress the matter to such a microscopic "grain". The materialized part of the universe was born from an accidental concentration of primordial ether (in some of its part), that masses of which started to rotate and complicate their forms. The condensed ether of space initiated an avalanche creation of the simplest forms of matter, which started to combine with themselves leading to creation of the most simple element, hydrogen. There were created numberless, gigantic whirling hydrogen clouds leading to further evolution of stars and to various forms of matter and their clustering. This process continues uninterrupted. Please treat it just as just my guess of course.
Unfortunately, I have upset those who would like to use a similar analogy that God just is and no one had created him. Well, it cannot be such analogy, because God is regarded as a perfect and ready-made being and at this point is missing another analogy, that similarly as complicated physical entity has its fundamental form, so God also should have his basic primordial element which evolved into perfect God. Because it is like this that nothing is created of NOTHING, but everything that was created, evolved from the primordial, fundamental building block of all forms of matter.