I’m not a physicist, but physics fascinates me almost as much as some people see in science a source of universal truth. It’s an unfortunate confusion, as science, by design, simply can’t answer all questions. Theories are based on assumptions, so there is always a level beyond which the answers stop. What’s more, some of the most fundamental phenomena still lack any kind of explanation. In short, we don’t have a clue what’s going on.
We measure time with clocks and think of it as something that is constantly flowing forward, together with us and everything we see. We found out just a century ago that it actually flows differently for different observers and that it’s possible to fast-forward through time by moving faster or getting closer to heavy objects. But these are abstract notions that we can hardly grasp, and they don’t clarify what time is. We don’t even know if it’s continuous or discrete and it seems like, from outside, our universe would simply look static.
We think of space as a three-dimensional emptiness in which our universe resides. We now know it to be intricately connected with time in a continuum called spacetime, but have no clue if it’s finite or infinite, if it has a shape and how it appeared. We don’t know why our universe has three spatial dimensions, and actually we aren’t even sure if they are three.
Space is a mysterious topological void through which electromagnetic and gravitational waves propagate. They travel at a certain speed which looks the same regardless of our own movement, and nothing can go faster. Experiments seem to confirm these rules, but what causes this behavior and why the speed of light has this particular value is unknown.
As we still commonly think of it as a force, gravity is now described as a consequence of objects bending the spacetime around them, pulling towards each other and dilating time. Again, nobody knows why this happens.
Matter makes up these objects around us, but we don’t know what it itself is made of. We call matter’s building blocks “elementary particles”, first believed to be atoms, then electrons, protons, neutrons and photons, and now quarks and leptons, each of different types. The deeper we look, the stranger things are, as particles sometimes behave as waves by spreading through space and interfering with themselves, and our observations seem to influence that. Matter has mass, another fundamental, yet elusive physical property that in some ways is equivalent to energy. There is also antimatter, which interestingly bears the properties of regular matter moving backward in time, and it is believed that most of our universe is actually made of dark matter, a hypothetical kind of matter that was not yet observed.
These are just some of the fundamental notions that we just take for granted. Science is built on postulates, and although we get better at modeling the behavior of the world around us using complex, powerful formalisms, we still can’t answer the most basic questions. But science doesn’t even attempt to do that. Physicists say they’re only addressing “how” questions, imagining and validating theories that describe and predict more accurately what we can observe. “Why” questions, they claim, have no definitive answer, as there will always be a certain base level of “why” where the answer can only be “because”. These distinctions and limitations are nothing new, but many seem unaware of them, believing that science can eventually clarify everything.