The physics of our everyday life such as baseballs travelling, the sun shining, electrical circuits, how your car works, things like that are explained well using what is called classical physics. This is using Newton's three laws of motion and his theory of gravity, along with Maxwell's equations to describe electricity, magnetism and light. Regions where some branches of physics get pushed are describing the very small, quantum mechanics, describing the very fast, special relativity, and describing the very massive, general relativity. In talking about physics and infinity I'm talking about pushing physics towards the very small, that is to zero size, and pushing physics to infinitely large, such as is the universe infinitely large? What does it mean to be infinitely small or big? Physics has problems with these issues. An interesting discussion is in the following post:
This is another post to the edge.org question about what scientific idea should be retired, all responses to this question are here:
The post I mentioned is from Max Tegmark, a physicist from MIT who wants to retire the idea of infinity.
The infinitely small I kind of understand, in that as far as I can tell the smallest size that can exist using present physics is the Planck length of 10-35 meters, that's a decimal point followed by 34 zero's then a 1. So space has a finite smallness at least as present physics says. Pretty darn small, an atom is about 10-10 meters. So Planck length is small but not zero. A picky point is that calculus is based on breaking up finite size object into smaller and smaller pieces until they are infinitely small. But physics says that the Planck length is not zero. I suspect that doesn't change what calculus means. Or in other words in calculus proofs for every epsilon that goes to zero, it now instead goes to the Planck length. Still a question, QED says electron's are point particles, so what gives? This I also have talked about here:
The infinitely big I still have a problem with. Our observable universe is about 28 billion light years in diameter, it is BIG. I like how the BBC's Hitchhiker's Guide to the Galaxy TV series talks the universes size. A light years is about 6 trillion miles. One mile = 1.61 km, I don't like miles but folks in the states have no good feel for a kilometer and the distance from the earth to Pluto is about 4 billion miles. So the universe is big but not infinite. That's all we can see, the observable universe. Modern Cosmology from inflation theory says that we live in a multiverse. That is we live in still a larger region, which we cannot observe that has other universe's similar (I'm at a loss for words here, like, similar just doesn't make it) to ours. The only way that I know about how we can observe these other universe's like ours is if in our universe's early history we collided with another universe. As far as I can tell from reading this could possibly be observed in the cosmic microwave background (CMB), that has been observed since the 60' but has been mapped out using satellites recently. As expected newer satellites are getting better resolution images of the CMB. Matching this data to theory is an area of research in Astronomy and Physics. A pretty cool area of research. The idea of a multiverse just kind of bothers me since we may not be able to ever observe them. If a theory has something that we can't observe what does that mean about that theory? I've posted stuff about topic earlier.