Narrator: 32 stories above the streets of New York City, a cat fell from a window and lived. After vets treated the cat’s chipped tooth and collapsed lungs, the feline was sent home two days later.
Cats fall a lot, and they’ve gotten really good at it. Drop a cat upside down, for example, and it will almost always land on its feet. That’s because cats are extremely flexible. They can twist their bodies mid-air as they fall.
But landing feet first isn’t always the best strategy. Like if you’re falling from 32 stories up. To figure out how cats manage that perfect landing every time, a series of studies looked at over a 100 cats’ falls from two to 32 stories up.
Comes as no surprise that cats who fell from the second floor had fewer injuries than cats who fell from the sixth floor. But here is the fascinating part. Above the seventh story, the extent of the injuries largely stayed the same, no matter how high the cats fell. So, how is that possible?
Well, it all comes down to acrobatics or lack thereof. Cats that fell from two to seven stories up mostly landed feet first. Above that, however, cats used a different technique. Instead of positioning their legs straight down as they fell, they splayed out like a parachuter. And landed belly-first instead.
But this method isn’t 100% foolproof. Chest trauma, like a collapsed lung, or broken rib is more common with this landing method. But the risk of breaking a leg is much less. So, how do cats somehow subconsciously know how to land?
It has to do with a physics phenomenon called terminal velocity. At first, the cat plummets faster and faster under gravity until she’s fallen the equivalent of five stories. At that point, she hits constant terminal velocity at 100 kilometers per hour. She’s now in free fall where air friction counteracts her acceleration under gravity. At this point, she’s no longer accelerating and, more importantly, doesn’t feel the pull from gravity.
So, here’s what researchers think is happening. From two to seven stories up, cats don’t have enough time to reach terminal velocity and prep for landing feet first. But once they hit terminal velocity, their instinct changes and they parachute their limbs.
All that said, don’t throw your cat out of a window. I can’t believe I have to say this. Not only is it still very dangerous, it’s not very polite. Don’t throw your cat out the window just to see all that go down. Just watch this video again. Just hit the little replay button.
EDITOR’S NOTE: This video was originally published in October 2018.
Narrator: In 1959, something happened that revolutionized NASCAR’s stock-car racing: the introduction of Daytona International Speedway.
Daytona was unlike any race track before it because of these: banked turns. The turns had towering walls that sloped downwards to the center. Walls that NASCAR’s stock cars would drive onto. Daytona’s banks were a whopping 31 degrees, significantly steeper than the relatively flat 12-degree banks at Martinsville or Occoneechee Speedways.
In the first year of Daytona, stock-car drivers qualified at speeds of more than 140 mph. And today, at the same track, that speed is more like 200 mph – in large part because of the steep banks. Which raises the question: How do banked walls help cars go faster?
Detractors of NASCAR joke that, to finish a race, all you have to do is turn left. To NASCAR fans’ chagrin, it’s somewhat true. For the majority of NASCAR tracks, most of the lap is completed while turning, or cornering. What critics misunderstand is that it’s the turns where good drivers earn their keep. Oftentimes, viewers will see stock cars rocket past each other in the straightaways and think that the faster car had more horsepower. The speed that driver uses to pass, however, comes largely from the momentum they collect in the curve they just left.
The winningest NASCAR drivers, then, are the ones that understand the corners the best, change direction the fastest, pick the best lines, and apply power at the right times to navigate the corners better than their competitors. It’s the corners where the races are won. Going straight is easy. Newton’s law of inertia tells us that an object going straight will keep going straight until something makes it change direction.
So driving a stock car on a straightaway, even at 180 mph, would be fairly easy for you or I. It’s turning that presents some challenges. To turn, a force needs to push the car sideways. That force is centripetal force. Imagine a ball attached to a string. When I twirl the ball in a horizontal circle, the tension in the string provides the centripetal force needed to make the weight curve.
Our stock cars do not have strings attached to them. The centripetal force needed to move the car left is caused, instead, by friction at the tires. But at high speed, the force of traction at the tires alone is not enough to pull the car to the left.
Let me explain by example. Think about turning sharp circles in a flat parking lot. The faster you go, the more unsteady the car will be. With enough speed, the car will slide out. For cars traveling above 180 mph, friction at the tires alone is not enough to get the cars moving to the left. For example, taking the first turn at Bristol Motor Speedway at 130 mph requires an immense 16,000 pounds of force to move the car to the left. That’s where high banks come in handy. When an object presses onto a surface, the object feels an equal force in the opposite direction. So for a stock car on a flat track, the track will push up with a force equivalent to the weight of the car.
On a banked track, however, only part of the force from the track goes straight up. The angle of the track directs the rest of the force towards the center. And that’s exactly the direction the driver is trying to turn. The extra force from the banked track, combined with the friction from the tires, is enough to turn the car safely. So the steep, banked turns let drivers maintain greater speeds into and through the turns.
While the banked track isn’t the only thing helping the car corner – aerodynamic downforce too helps the car generate lateral force – it is one of the most important factors keeping stock cars cornering at speed. NASCAR’s banks are for cars going at race speeds. At lower speeds, the 33 degree bank at Talladega Superspeedway would be enough to slide a car down to the bottom of the track. In fact, if you or I wanted to take a lap around Talladega in a street car, we’d constantly be turning right to just stay up on the wall.
But you don’t need to be a stock-car driver to test a banked turn for yourself. Banked turns exist on our roads, too, on freeway on-ramps and interchanges. For heavy vehicles like trucks and buses, friction alone may not provide enough force to turn safely, especially if the driver doesn’t slow down enough. A slightly banked turn, with a gentle grade of 15 degrees or less, can help push the vehicle into the turn.
So, for NASCAR, banked turns simultaneously create lateral force that, in addition to friction force at the tires, create enough centripetal force in total to get stock cars moving to the left but also enable them to travel at higher speeds without sliding or flying off the track.
EDITORS NOTE: This video was originally published in August 2019.
One of the most ubiquitous subatomic particles in the universe, the muon, seems to be misbehaving.
Or at least, it isn’t behaving the way physicists expect. In fact, muons are deviating so much from what the laws of physics suggest that scientists are beginning to think their playbook is either incomplete, or there’s some force in the universe we don’t yet know about.
Muons are like fat electrons: They have a negative charge but are 207 times heavier than electrons. Thanks to their charge and a property known as spin, they act like tiny magnets. So when muons are immersed in another magnetic field, they experience an infinitesimal wobble.
But in a study released this week, physicists at the Fermilab in Illinois reported a discrepancy between how much muons should be wobbling and how much they actually did wobble during a lab experiment.
The difference is substantial enough that many scientists are convinced particles or forces we haven’t yet discovered must be involved. The finding, in other words, offers new evidence that something mysterious has played a role in shaping our universe – something that’s missing from the existing rules of physics.
“In this respect, the new measurement could indeed mark the start of a revolution of our understanding of nature,” Thomas Teubner, a theoretical physicist from the University of Liverpool who was not involved in the research, told Insider.
It’s possible that this unknown phenomenon is also linked to dark matter, the shadowy cousin of matter that was created just after the Big Bang and makes up a quarter of the universe.
Shooting muons in a circle at the speed of light
When cosmic rays penetrate Earth’s atmosphere, they create muons. Several hundred muons strike your head every second. They can penetrate objects like an X-ray does – a few years ago, scientists used muons to discover a hidden chamber in Egypt’s Great Pyramid – but the particles only last for two-millionths of a second. After that, they decay into clusters of lighter particles.
During its brief existence, each muon remains oriented around a single point, in the same way a compass always points north. But when it encounters a magnetic field, a muon’s orientation shifts slightly away from that point. That crucial wobble, known as the g-factor, is what the Fermilab experiment is examining.
Fermilab is a US Department of Energy project with ties to the University of Chicago that’s devoted to the study of particle physics.
Scientists there can produce muons for study by running a beam of protons super quickly into metal using a particle accelerator. So the researchers behind the new study took these muons and funneled them inside a circular electromagnet 50 feet in diameter. The muons then traveled at nearly the speed of light around the circle more than 1,000 times.
When muons in the machine decay, ultra-sensitive detectors can measure which direction the resulting smaller particles are moving. Physicists can then use that information to calculate where each muon’s fixed point is.
It should be possible to calculate the precise amount muons will wobble using the Standard Model of physics, which encompasses everything we know about particles’ behavior. But the Fermilab team found that their muons’ wobble did not match those expectations.
Instead, it was off by one-third of one-millionth of a percent.
That difference may seem mind-bogglingly small, but Teubner said it’s actually “a milestone for particle physics.”
And it’s unlikely to be the result of error: The team found that there’s only a 1 in 40,000 chance the discrepancy in their measurement was due to random chance.
“This is strong evidence that the muon is sensitive to something that is not in our best theory,” Renee Fatemi, one of the Fermilab muon experiment managers, said in a press release.
A 20-year mystery
This isn’t the first time muons have not behaved in the way science’s best theories would predict.
In 2001, the Brookhaven National Laboratory in New York ran a similar experiment using the same giant electromagnet. Those results also showed that muons’ wobble in the lab deviated from what it should have been. But those findings had a smaller statistical significance than Fermilab’s: There was a 1 in 1,000 chance it could have been a fluke.
Now, the Fermilab results confirm what Brookhaven physicists discovered 20 years ago – and that “has made the discrepancy which was already seen with the old result more intriguing,” Teubner said.
Fermilab is expected to release data from two more similar experiments within the next two years. A fourth experiment is also already underway, and fifth is in the works.
Whatever is influencing muons could have a link to dark matter
According to Teubner, it’s possible that some force that’s not in the Standard Model of physics could explain the muons’ whack-a-doo wobbles.
That force, he said, may also explain the existence of dark matter, and possibly even dark energy – which plays a key role in accelerating the expansion of the universe.
“Theorists would find it appealing to solve more than one problem at once,” Teubner said.
One hypothesis that could apply to both muons and dark matter, he added, is that muons and all other particles have almost identical partner particles that weakly interact with them. This concept is known as supersymmetry.
But Fermilab’s existing technologies aren’t sensitive enough to test that idea. Plus, Teubner added, it’s could be the case that the mysterious influence on muons isn’t linked to dark matter at all – which would mean the rules of physics are inadequate in more ways than one.