History and Philosophy of Physics physics.hist-ph

The clock on the kitchen wall ticks, and each tick relentlessly carries us from breakfast to lunch. This is so familiar that it seems like a law of nature, but physics says otherwise. In Einstein's equations, time is reversible: you can rewind the film, and no frame will give the trick away.

When entropy reaches its maximum, the play is over. The curtain falls, the actors leave, the scenery freezes. But the stage remains. So it is with time: the heat death of the universe erases the direction 'past—future', but not time itself.

Intelligent action begins with a plan. Just as an architect needs blueprints to evaluate options, any agent with will needs to repeatedly copy data about reality.

Two particles can become linked so that a nudge on one instantly reverberates in the other, even if they are separated by galaxies. Einstein called it "spooky action at a distance." Physicists wondered: can gravity itself, a simple mutual attraction, create such a connection?

We are used to thinking that events have causes, objects exist independently, and signals cannot outpace the speed of light. Quantum mechanics, which describes the Standard Model of particles, challenges all these assumptions at once — as if a recipe couldn't use all seven ingredients.

The night sky is full of stars, but they are only a small part of everything that exists in the universe. Astronomers have long noticed a strange thing: galaxies rotate so fast that they should fly apart, yet they don't. Something invisible holds them together, like invisible threads linking beads on a spinning wheel. This "something" was named dark matter.

According to the laws of physics, nothing can outrun light, otherwise for some observers the effect would occur before the cause. Artur Ekert and Andrzej Dragan showed that this situation creates an uncertainty resembling quantum indeterminacy.

Physics often resembles the construction of a giant ship — the Universe. The physicist-engineers have yet to agree on the basic blueprints.

In 1867, James Clerk Maxwell proposed an image that still stirs physicists today. Two compartments of gas are separated by a door. Molecules dart about chaotically: fast and slow. A tiny gatekeeper opens the door only for fast ones, letting them through to one side, and slow ones to the other. The hot compartment gets hotter, the cold one colder.

An old mechanical alarm clock ticks on the shelf. You hear the steady sound, see the hands moving, and you're certain time is passing. But if you take the clock apart, you won't find a single part labeled "time." Only springs and gears.

Erasing even a single bit means releasing heat. This discovery by Rolf Landauer hinted that information is neither material nor illusory. Imagine that every event casts a shadow: that is information, the collection of all unrealized possibilities.

Two thousand years ago, a brilliant beacon shone in the constellation Eridanus, recorded in the registers of ancient astronomers. Hipparchus in 129 BCE noted it as a first-magnitude star, Ptolemy confirmed its brightness in the Almagest, and the Persian scholar Al-Sufi still saw it among the brightest in 964.

In the grand orchestra of the universe, every instrument has its own rhythm. Electrons in an atom make quantum leaps in femtoseconds, neurons in the brain exchange signals in milliseconds, and a human needs tenths of a second to become aware of the 'now.' Physicists have long sought the conductor…

A quantum wave is like a long-exposure photograph: everything’s blurred, but the blur itself reveals motion. Usually these frozen waves are treated as convenient abstractions. Yet if at each point in the image you estimate, by brightness, the moment on the particle’s internal clock it landed there, flat space suddenly acquires curves.

Berlin, December 1943. A bomb flash, and the first fully automatic programmable computer in history, the Z3, vanishes in flames. Its creator, Konrad Zuse, doesn’t even try to rebuild the hardware: after the war, he constructs new machines. But the idea of the Z3—like a lost painting, with only sketches and memories left — awaits its moment.

Deep in the Amazon rainforest, beneath a multi-layered canopy of leaves, lie vast earthen figures — squares, rectangles, the occasional rhombus. For decades they teased archaeologists with their silent geometry, until a researcher armed with orbital optics saw them as an astronomical instrument.

In 2019, the world saw the first image of a black hole's shadow — an orange doughnut on a black background, becoming a symbol of scientific progress. But this image wasn't captured by a camera: it was born from mathematical alchemy, where data from eight radio telescopes, which gathered only crumbs of signal, merged into a single picture.

Newton gave us a world where bodies move in a void and clocks tick the same for everyone. For three centuries, this picture worked flawlessly. But it relies on many invisible props: absolute position, the 'up-down' direction, and a single rhythm of time for the entire universe. We have never measured these directly — only through the relations between objects.

A thrown stone arcs through the air, but a planet around the Sun follows a closed curve. Why an ellipse, and not a circle or a spiral? Kepler's first law provides the answer, but its usual proof requires heavy computation. This work offers a shorter path — through a single simple ratio of velocities.