After Turing, computer scientists began to classify other problems by their difficulty. Harder problems require more computational resources to solve — more running time, more memory. This is the study of computational complexity. Ultimately, every problem presents two big questions: “How hard is it to solve?” and “How hard is it to verify that an […]

Can you spot the ISS? It’s that “star” that looks like a short line, near the tree. The phone took a 1-second exposure, and that’s how far the station moved in that time. That’s pretty cool. Oh, notice that this is right by the star Betelgeuse in the constellation Orion. (Speaking of which, I’m a […]

I hope you already know you shouldn’t believe every crazy-awesome thing you see on the internet; there’s a lot of fake stuff out there. But don’t worry, it’s possible to use physics and video analysis to see what’s real and what’s not. So, some guys tweeted out this cool-looking soccer trick: One dude kicks a […]

The catch is that directly measuring the Hubble constant is very tricky. To do so, astronomers like Riess and Freedman must first find and calibrate “standard candles”: astronomical objects that have a well-known distance and intrinsic brightness. With these values in hand, they can infer the distances to standard candles that are fainter and farther […]

Katherine Johnson blazed trails, not just as a black female mathematician during the Cold War, but by mapping literal paths through outer space. Her math continues to carve out new paths for spacecraft navigating our solar system, as NASA engineers use evolved versions of her equations that will execute missions to the moon and beyond. […]

In doing so, they found GJ 1151, a faint star with a shockingly long-lived emission. GJ 1151 belongs to a class of stars called M dwarfs, which are small, dim, and extremely common; they make up roughly 70% of all stars in the Milky Way. M dwarfs are often extremely magnetically active. Many spin rapidly, […]

That’s all fine and everything until the human loses contact with the ground. At that point, there are only two forces on the human—the downward gravitational force and the downward spring force from the pack. That yields a downward acceleration greater than what it would be from gravity alone. At the same time, the pack […]

The laws of physics, as experts currently understand them, dictate the following: Every fundamental particle has an antimatter twin. The electron, quark, and muon, for example, are paired with the positron, antiquark, and antimuon, respectively. Each antiparticle weighs exactly the same as its twin, but exhibits precisely the opposite electric charge. If the twins meet […]

The broom challenge is back! This fun little trick returns every few years on social media. It’s supposed to show a gravitational alignment (whatever that is) among the planets that allows a broom to stand up by itself. It’s super special and rare. At least that’s what I hear from Cal Tech high-energy physicists and […]

One sunny day last summer, Mathias Kolle, a professor at the Massachusetts Institute of Technology, took a couple of eminent colleagues out sailing. They talked about their research. They had some drinks. Then Kolle noticed something was off: A rowboat tied to his boat had come loose and was drifting toward the horizon. As he […]

But after a quick search, I found that a titanium alloy has an ultimate tensile strength of 900 MPa. With that, I can calculate the width of a beam with a square cross section that can support this force. Actually, as you can see above, it isn’t bad—just 15 centimeters. That’s doable. What about the […]

Everybody loves bubbles, regardless of age—the bigger the better. But to blow really big, world-record-scale bubbles requires a very precise bubble mixture. Physicists have determined that a key ingredient is mixing in polymers of varying strand lengths, according to a new paper in Physical Review Fluids. That produces a soap film able to stretch sufficiently […]

But how about a numerical value for the electric field between these conducting plates? If I just go straight down the middle from one plate to the other, I can get electric potential values for different y values. Here’s what that looks like: Remember the relationship between the electric field and the potential. The electric […]

It sounds almost like science fiction: a tiny world that formed around another star, visiting our cosmic neighborhood for us to study. And yet that’s exactly what has happened, twice now as of the last few months. It will only happen more often this decade. Original story reprinted with permission from Quanta Magazine, an editorially […]

Inside a small metal box on a laboratory table in Vienna, physicist Markus Aspelmeyer and his team have engineered, perhaps, the quietest place on Earth. The area in question is a microscopic spot in the middle of the box. Here, levitating in midair—except there is no air because the box is in vacuum—is a tiny […]

In this position, the truck is stable—there is no rotational motion. As before, the gravitational force acts at the center of mass. The force from the ground is not applied at the center of mass, but notice that if you extend a line from that arrow, it would pass right through the center of mass. […]

Along with personal jetpacks for every man, woman, and child (sure, why not), levitation is one of those conveniences that sci-fi has long promised us but has yet to deliver, other than magnetically levitating trains. But at Argonne National Laboratory in Illinois, physicist Chris Benmore and his colleagues are levitating objects with an unlikely tool: […]

Although the emergence of organoid consciousness, experience of pain, self-recognition and other worrisome traits inevitably comes up in Brainstorm Project meetings, that’s not their central focus—those developments are still too far off. Instead, Lunshof, Hyun and their colleagues want to pinpoint more immediate ethical issues worth considering. Discussions of consciousness are crucial, “but keeping your […]

On January 9, the World Health Organization notified the public of a flu-like outbreak in China: a cluster of pneumonia cases had been reported in Wuhan, possibly from vendors’ exposure to live animals at the Huanan Seafood Market. The US Centers for Disease Control and Prevention had gotten the word out a few days earlier, […]