David Appell

There is no measurement that can directly observe the wave function of a quantum mechanical system, but the wave function is still enormously useful as its (complex) square represents the probability density of the system ...

A new study of climate extremes since 1988 finds that many regions have seen increases in deaths due to floods, storms and extreme temperatures. In human terms, the harm comes not just from deaths, but also from lost labor ...

Hypervelocity stars have, since the 1920s, been an important tool that allows astronomers to study the properties of the Milky Way galaxy, such as its gravitational potential and the distribution of matter. Now astronomers ...

Scientists in China have performed an experiment first proposed by Albert Einstein almost a century ago when he sought to disprove the quantum mechanical principle of complementarity put forth by Niels Bohr and his school ...

For experimental physicists, the latest measurement of the muon is the best of times. For theorists there's still work to do.

With the discovery of ever more exoplanets—over 6,000 now—scientists, of course, want to know if they are habitable for life. (At least, life as we know it.) But assessing habitability is a difficult task, as information ...

Are you worried that artificial intelligence and humans will go to war? AI experts are. In 2023, a group of elite thinkers signed onto the Center for AI Safety's statement that "Mitigating the risk of extinction from AI should ...

In their quest to explore and characterize high-temperature superconductors, physicists have mostly focused on a material that is not the absolute highest. That's because that crystal is much easier to split into uniform, ...

There has long been a mystery when calculating how an incoming light wave scatters off an object and becomes a modified, outgoing light wave. In particular, the time delay of the transition from one to the other comes out ...

In 2015, astronomer Tabetha Boyajian and colleagues announced the discovery of unusual light fluctuations coming from a star about 1,500 light-years away. It came to be known as "Tabby's star" or "Boyajian's star," and the ...

Pounding on the bottom of a glass bottle of ketchup is one of life's small annoyances. Getting that sweet, red concoction from its solid phase to a liquid takes too long when you're hungry and could even require messy strategies ...

Very soon after the Big Bang, the universe enjoyed a brief phase where quarks and gluons roamed freely, not yet joined up into hadrons such as protons, neutrons and mesons. This state, called a quark-gluon plasma, existed ...

Besides particles like sterile neutrinos, axions and weakly interacting massive particles (WIMPs), a leading candidate for the cold dark matter of the universe are primordial black holes—black holes created from extremely ...

Comets that have hit Earth have been a mixed bag. Early in Earth's history, during the solar system's chaotic beginning, they were likely the source of our planet's water, ultimately making up about 0.02% of the planet's ...

In every scientific discovery in the movies, a scientist observes something unexpected, scratches the side of his or her forehead and says "hmmmmm." In just such a moment in real life, scientists from Canada observed unexpected ...