Scientists Created a Water Tractor Beam

Tractor beams have long been a science fiction fantasy—a magical force that attracts objects from a distance, like an alien’s spaceship sucking up its earthling specimens. We’re not quite that advanced, but physicists at The Australian National University have created a “tractor beam on water” that makes floating objects move wherever they are directed.

The group, led by Professor Michael Shats, started with a ping pong ball. Placing it in a small pool, they created waves using a thin, cylindrical device with suction cups on the bottom. When the device vibrates up and down, these cups come in contact with the water, creating waves. Different wave frequencies and sizes, along with different cup shapes, create different kinds of currents. Some pulled the ball inward, some pushed it outward.

Dr. Horst Punzmann, from the Research School of Physics and Engineering, said the team even found a way of “creating waves that can force a floating object to move against the direction of the wave.”

This doesn’t sound like rocket science. It seems quite obvious that waves make floating objects move, right? But actually, what propels floating objects aren’t the waves themselves, it’s the currents they create. Never before have we identified the precise wave patterns that make an object go one way or another, or how to replicate them. “It’s one of the great unresolved problems, yet anyone in the bathtub can reproduce it,” Punzmann said. Interestingly, there’s still no mathematical theory to explain why these experiments work. That said, this new knowledge could help us clean up oil spills and ocean trash, or retrieve drifting boats.

"The applications could be numerous," Shats said. A paper documenting the findings is featured in the journal Nature Physics.

© 2017 USPS
Pop Culture
Speedy Delivery: Mister Rogers Will Get His Own Stamp in 2018
© 2017 USPS
© 2017 USPS

USPS 2018 Mister Rogers stamp
© 2017 USPS

After weeks of mailing out this year’s holiday cards, postage might be the last thing you want to think about. But the U.S. Postal Service has just given us a sneak peek at the many iconic people, places, and things that will be commemorated with their own stamps in 2018, and one in particular has us excited to send out a few birthday cards: Mister Rogers.

In celebration of the 50th anniversary of Mister Rogers’ Neighborhood, Fred Rogers’s groundbreaking PBS series that the USPS says “inspired and educated young viewers with warmth, sensitivity, and honesty,” the mail service shared a mockup of what the final stamp may look like. On it, Rogers—decked out in one of his trademark colorful cardigans (all of which were hand-knitted by his mom, by the way)—smiles for the camera alongside King Friday XIII, ruler of the Neighborhood of Make-Believe.

Though no official release date for Fred’s forever stamp has been given, Mister Rogers is just one of many legendary figures whose visages will grace a piece of postage in 2018. Singer/activist Lena Horne will be the 41st figure to appear as part of the USPS’s Black Heritage series, while former Beatle John Lennon will be the face of the newest Music Icons collection. Sally Ride, the first American woman in space, will also be honored.

Can You Spot the Christmas Pudding?

Whether it’s a sheep hanging out with Santa Claus or a panda bear hiding among some snowmen, regular Mental Floss readers know that hidden picture brainteasers are one of our favorite things. And the optical experts at have released a delicious one, just in time for Christmas. Somewhere in the midst of all these holiday-themed goodies above, there’s a holiday pudding just waiting to be discovered. Can you spot it? Your time starts … now.

If you give up, or are the kind of person who reads the last page of a book before the first one and just wants to know the answer, scroll down to see where it’s hiding.



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