The Fun of Figuring Things Out

If you had to pass on just one sentence of scientific knowledge to the next generation, it would be the atomic hypothesis: all things are made of atoms — tiny particles in perpetual motion that attract one another at a small distance but repel when squeezed too close together. That one idea, used with a little imagination, explains why water freezes into a rigid pattern and boils into steam, why things have pressure and heat, and why salt dissolves. It is the foundation everything else is built on.

Before about 1920 we thought we understood the world: a three-dimensional stage, things changing in time, and particles pushed and pulled by forces like gravity and electricity. Then we looked closely at the world of the atom and found the old rules were wrong. On a small scale, things behave in strange, 'unnatural' ways. This is quantum mechanics, where you cannot know a particle's position and speed at the same time and where we can only predict probabilities. That stranger physics is the deeper game Nature is really playing.

A poet once said, 'The whole universe is in a glass of wine.' Look closely enough and it is true. The swirling liquid and evaporating alcohol are physics; the glass is distilled from the Earth's rocks, which is geology; the ferments and enzymes are chemistry; and the great idea that life is a kind of fermentation is biology. The sciences are different views of the same reality, and physics is the most fundamental because it describes the atoms everything is made from. Nature does not know we divided her into subjects.

There is a law that, as far as we know, is never broken: energy is conserved. But what is energy? Imagine a child with 28 indestructible blocks. Each day the total is still 28, even when some are hidden in a box or out on the lawn — the mother just needs a clever formula to count the hidden ones. Energy is like that. It is not a 'thing' you can hold; it is a number you compute from a formula, and the astonishing fact is that the total never changes, no matter how the energy shifts from one form to another.

Time is what a clock reads; distance is what a ruler reads. But how do you measure the age of the Earth or the distance to a galaxy? You cannot use a stopwatch or a meter stick, so scientists invent new clocks — like the radioactive decay of uranium — and new rulers — like the parallax shift of stars. The key point is that our ideas of time and distance are tied to the actual operations we perform to measure them. Physics is not abstract philosophy; it is about what we can really measure.

We make guesses because we rarely have all the information. Probability is a system for making better guesses. Picture a drunk man taking steps at random: on average he ends up nowhere, yet he does drift away from the start. Remarkably, the average of the square of his distance grows in proportion to the number of steps. This 'random walk' is a powerful model for diffusion of gases and many other natural processes — showing that even in pure chaos, predictable laws emerge.