How do you become an Atheist?

[theVOID]

Scientists have a philosophy (most commonly methodological naturalism) but I don't see how that gets to Physics == Philosophy.
You can have a philosophy (interpretation) of physics, but physics exists without an interpreter.

Philosophy is a systematic study of fundamental problems. The working of the world of which we are a part is the most fundamental of them all, without which no other philosophical problem can exist on anything like credible footing, so the natural sciences are the most philosophical of all philosophies.

I'm glad to see that at least one person in the world has a definition of philosophy that fits into a single line

Philosophy is not a study of all fundamental problems, it's more of a fuzzy subset of problems that can't actually be given any clear boundaries, some overlap with physics, some with psychology, some with neuroscience etc, but Science and Philosophy aren't the same thing, notably in the nature of the questions being answered. Science is generally asking "what does this mean" and philosophy "what does this mean for us", but like always there is a healthy amount of overlap, I'm into the Experimental Philosophy movement which is a fairly comprehensive example of this.

Also, natural science doesn't establish a priori truths, which is a massive part of the philosophical endeavor, you can't scientifically arrive at non-contingent and necessary truth.