[kosh2]

The only thing that can maybe be understandable for us is an infinite universe. What was before 0? -1. What before that? -2.

But how can we ever understand how out of a state of nothingness came something? That is where the science "ends" and the door to philosophy opens.

Those are similar problems like "Why is there not nothing?", "Why are the laws of nature not different?" etc.

[green_on_black]

To add to your point, why should there be nothingness? Who is to say that 0 is before 1? There's 1/2 somewhere right? And 1/4 before that, etc.

It's not obvious that there "should" be nothing, rather than perpetual something. It's not obvious we should work with integers and not the reals. Or the rationals. Or the rationals without zero, which cannot exist as a denominator (in the common definition of the rationals). It's not obvious that we've ever detected zero. And why a line? Why not a circle? And even if a line, couldn't it be the limit of a circle whose radius tends to infinity? Etc.

[goldenkey]

In projective geometry negative infinity and positive infinity meet :-)