Yes one and one equals two in human mathematics but the universe doesn't care about human mathematics and it's calculations could result in a myriad of different answers each time it does the calculation. Isaac Newton believed that his theory of gravity was correct because what he observed agreed with his mathematics but it turned out that it was only 'close enough for jazz' and it took Einstein to realise that, while the maths gave a 'good enough' answer it wasn't actually the correct answer. Even now, although we accept Einstein's theorems because they agree with our observations they may not, again, actually be correct but simply appear to be correct. We try to fit the mathematics to what we observe and it often seems that the two agree but it ain't necessarily so. In this crazy mixed up universe quantum physics includes the idea that particles can pop into and out of existence without rhyme or reason and can essentially be everywhere and anywhere until we look at them in which case we cause a collapse and pin them down. So, in quantum terms you could have one plus one but, when you go to do the calculation you discover that one or both of them have popped out of existence and you have a different result than expected. We take the speed of light in a vacuum as a 'constant' and so, theoretically, if you were able to reach the speed of light yourself travelling in the same direction as a beam of light, you would find it to appear stationary, like two cars both travelling at the same speed and one car is stationary relative to the observer in the other car but no, even if you were travelling at the speed of light that beam of light would be travelling at exactly the speed of light relative to you if you measured it. logically that doesn't compute but it's real. Light seems to be the one thing in the entire universe that doesn't experience and isn't affected by time.
