Conservation of Momentum
Conservation of momentum is one of the most fundamental and reliable laws in all of physics. Momentum, the product of an object's mass and its…
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Gravitational Lensing
Gravitational lensing is the bending of light from distant objects by the gravity of massive bodies that lie in between, which can magnify and…
Radioactive Decay
Radioactive decay is the process by which unstable atomic nuclei spontaneously break down, releasing energy and particles and transforming into other…
The Bending of Starlight
The bending of starlight is the deflection of light by gravity, predicted by Einstein's general theory of relativity and confirmed during a solar…
Superconductivity
Superconductivity is a remarkable state in which certain materials, when cooled below a critical temperature, conduct electricity with absolutely no…
The Higgs Boson
The Higgs boson is a fundamental particle whose discovery in 2012 confirmed how other particles acquire mass. Long predicted but famously hard to…
The Neutrino
The neutrino is a tiny, almost massless subatomic particle that barely interacts with anything, streaming through matter, and through us, in…
The Cosmic Microwave Background
The cosmic microwave background is a faint glow of microwave radiation that fills all of space, the leftover heat from the early universe. Its…
Brownian Motion
Brownian motion is the random, jittery movement of tiny particles suspended in a fluid, caused by their constant bombardment by the fluid's…
The Expanding Earth
The expanding Earth was a hypothesis, taken seriously by some scientists into the twentieth century, which claimed that the planet is steadily…
Piltdown Man
Piltdown Man was a supposed "missing link" between apes and humans, announced in 1912 from fossil fragments found in England. For decades it misled…
What Causes Alzheimer's Disease
Alzheimer's disease is the most common cause of dementia, slowly destroying memory and thinking. That it damages the brain is clear, but what…
How Birds Navigate
Many birds travel thousands of miles between breeding and wintering grounds, often returning to the very same spot year after year. How they find…
How the Americas Were Settled
How and when the first people reached the Americas is a genuinely contested question. That humans came from Asia is clear, but the timing and the…
Exoplanets
Exoplanets are planets that orbit stars other than our Sun. For centuries their existence was only speculation; today thousands have been confirmed,…
The Photoelectric Effect
The photoelectric effect is the release of electrons from a material when light shines on it. Simple to observe yet impossible to explain with older…
Gravitational Waves
Gravitational waves are ripples in the fabric of space and time, set off by some of the most violent events in the universe. Predicted by Einstein a…
The Drake Equation
The Drake equation is a famous formula that estimates how many communicating alien civilizations might exist in our galaxy. It is less a precise…
The Aquatic Ape Hypothesis
The aquatic ape hypothesis is the controversial idea that human ancestors went through a phase of living partly in water, and that this shaped many…
Grand Unified Theory
A Grand Unified Theory is a hypothesized framework that would merge three of the fundamental forces of nature, the electromagnetic, weak, and strong…
Snowball Earth
Snowball Earth is the hypothesis that, on one or more occasions in the distant past, our planet froze over almost completely, with ice reaching from…