Quanta Magazine

We know the sequence of our genome. But beyond that, things get a little fuzzy. Since its molecular structure was deduced in the 1950s, DNA has been hailed by many biologists as the secret of life. They’ve read and studied the information stored in the DNA found in the cells of living organisms, known as their genomes, and claimed that this genetic database must be some kind of blueprint. But if DNA really does harbor some greater secret about how life works, biologists have yet to find it – and it’s not from lack of trying. Despite knowing the entire sequence, the human genome is less of a blueprint than a puzzle that gets harder the longer you look at it. This is in large part thanks to gene regulation: By switching suites of genes on and off, many different cell types in our bodies can all be created from the same material. Cells also regulate their genes from moment to moment in response to a constant inflow of signals from their neighbors and surroundings. It’s the processes that

How many elementary particles do you think there are? It’s not a trick question — and the answer depends on whom you ask. The known elementary particles and their interactions obey a set of equations called the Standard Model of particle physics. The Standard Model is a “quantum field theory,” a mathematical description of reality in which entities called quantum fields permeate the universe. Ripples moving through these fields are what we call elementary particles; some make up matter, others impart forces. The quantum fields and associated particles in the Standard Model underline all physical phenomena other than gravity, dark matter, and dark energy. On classroom posters, there are 17 particles, which you might be familiar with: 12 for matter, four for forces, and finally the special Higgs boson. It may just be this simple. Or maybe not. You could theoretically keep counting and counting, and end up at 37, or 61, or maybe even 118. And that’s before we get to what David Tong, a Uni

Ice comes in more forms than what you’ll find in a freezer or a glacier. Since 1900, scientists have observed more than 20 phases of ice, many of them shaped under extreme conditions. The growing list includes hot ice and even ice that conducts electricity. Ice is the name for any phase of water that is solid and crystalline, meaning that it has a repeating molecular structure. Over the past decade, computer simulations have predicted tens of thousands of possible forms of ice. Though uncommon on our planet, exotic ice may exist in off-Earth environments, from cold and amorphous comet tails to the hot and crushing cores of icy planets. As physicists put water to the test with improved experimental techniques, they keep finding surprises. “You take water, and just the way you compress it — a little bit faster, a bit slower, up and down, at the right timescale — and then you can find this completely unexpected behavior,” said Marius Millot, a research scientist at Lawrence Livermore Nati

From the tangle in your computer cord to the mess your cat made of your knitting basket, knots are everywhere in daily life. They also pervade science, showing up in loops of DNA, intertwined polymer strands, and swirling water currents. And within pure mathematics, knots are the key to many central questions in topology. Yet knot theorists still struggle with the most basic of questions: how to tell two knots apart. It’s hard to decide whether two complicated knots have the same structure just by looking at them. Even if they appear completely different, you might be able to turn one into the other by moving some strands around. (To a mathematician, the ends of a knot are always fastened together so that such motions won’t untie it.) Over the past century, knot theorists have developed a set of clear, if imperfect, tools for distinguishing knots. Called knot invariants, these tools each measure some aspect of a knot — a pattern formed by its interwoven strands, perhaps, or the topolog

You’re the earliest known life form. There’s no food around right now. It would be great to go somewhere else. But you’re stuck. Really stuck. At your size (a couple of microns), water feels like tar, or rather, it feels the way being stuck in tar will eventually feel to a human. What do you do? [𝘖𝘯𝘦 𝘰𝘳 𝘮𝘰𝘳𝘦 𝘣𝘪𝘭𝘭𝘪𝘰𝘯 𝘺𝘦𝘢𝘳𝘴 𝘭𝘢𝘵𝘦𝘳.] You’ve found the perfect solution. Literally perfect. Evolution has created the flagellar motor, a combination propeller/brain that enables single-celled bacteria to move toward food sources. It’s an electric motor that rotates at several hundred revolutions per second — faster than the flywheel in a race car engine — to twirl a tail-like flagellum that pushes the cell along. When the flagellar motor rotates counterclockwise, it propels the cell through the water 10 or more times its own length in a second. The motor can also rotate clockwise, causing the cell to tumble about randomly. This amazing, self-assembling, signal-processing, direction-switching molec

If you were asked to picture how electrons move, you could be forgiven for imagining a stream of particles sluicing down a wire like water rushing through a pipe. After all, we often describe electrons as “flowing” in an “electric current.” In reality, water and electricity flow in completely different ways. Whereas water molecules move together to form a swirly, coherent substance, electrons tend to fly past one another. “Water is seeing nothing but other water,” said Cory Dean, a physicist at Columbia University, “but in an electronic system, in a wire, that’s manifestly not the case.” Water molecules unite to flow, but each electron acts on its own. This every-particle-for-itself movement serves as the foundation for all of electronic theory. It explains why a warm wire resists more than a cold wire, and why a round wire conducts as well as a square wire. But since the 1960s, theorists have suspected that electrons can be coaxed to act more like their watery counterparts, and to for