## Gravity visualized with a big sheet of stretched Lycra

AP physics teacher Dan Burns gave a fun demonstration about spacetime curvature in 2012 at Los Gatos High School. Here's the 10 minute video.

Here's another good one from Burns: the "Pole and Barn Paradox":

This is my favorite Special Relativity paradox. It will blow your student's minds. A runner traveling at 0.87c with a 20 m long pole runs through a 10 m long barn. To the barn FOR the pole shrinks and the barn doors can be closed for an instant with the ole completely inside. From the runner's frame of reference the barn contracts to 5 m and the pole can NOT fit with both doors closed! How is this resolved? You can use the slides and associated videos to go though this mind-bender with an added twist at the end.

[via]

## Make: the simplest electric car toy, a homopolar motor

Put round magnets on either end of a AA battery and set it down on a sheet of tinfoil and watch it spin! It's a homopolar motor, a simple electric motor that relies on the Lorentz effect to set it in motion.

## Stephen Hawking cancels appearances because of “ill health”

Cambridge University today said that Stephen Hawking is cancelling several public appearances because of ill health.

## Entropy explained, beautifully, in comic-book form

Nick Sousanis became a Boing Boing favorite for his 2015 doctoral dissertation in graphic novel form, and since attaining his PhD, he's become a postdoctoral fellow in Comics Studies at the University of Calgary. Read the rest

## Sagan, Hawking, and Clarke have a gabfest (1988)

Watch these three guys discuss "God, The Universe and Everything Else," which includes extraterrestrials, creativity, science fiction, education, the Cold War, fractals, and so much more.

## Actual textbook physics problem

You are kidnapped by political-science majors (who are upset because you told them political science is not a real science). Although blindfolded, you can tell the speed of their car (by the whine of the engine), the time of travel (by mentally counting off seconds), and the direction of travel (by turns along the rectangular street system). From these clues, you know that you are taken along the following course: 50 km/h for 2.0 min, turn 90° to the right, 20 km/h for 4.0 min, turn 90° to the right, 20 km/h for 60 s, turn 90° to the left, 50 km/h for 60 s, turn 90° to the right, 20 km/h for 2.0 min, turn 90° to the left, 50 km/h for 30 s. At that point, (a) how far are you from your starting point, and (b) in what direction relative to your initial direction of travel are you? – From Halliday & Resnick Fundamentals of Physics Extended 9th Edition Read the rest

## Heathrow security insists that ice is a liquid

Simon Perry froze a can of Diet Coke solid and took it through security at London's Heathrow Airport to see whether he could find a loophole in the "no liquids" rule. Read the rest

## World's most powerful digital camera gets green light from U.S. Dept. of Energy

Construction has been okayed for a 3.2-gigapixel digital camera, which would be the world’s largest, at the heart of the Large Synoptic Survey Telescope.

## Watch: Tiny floating robot can jump from water's surface

Researchers led by Je-Sung Koh created a biomimetic robot that floats using surface tension and can jump from the surface of water like a water strider insect. Read the rest

## Why magenta doesn't appear in the rainbow

Steve Mould's colored flashlights (sometimes called "coloured torches" in distant lands) are useful props in this excellent 5-minute lecture on color mixing. I learned that magenta is not a color. Rather, it is the absence of green.

## Gorgeous mirrored room with 250 colorful fluorescent tubes

The UK's National Media Museum currently hosts a Festival of Light installation by Liz West. An Additive Mix fills the room with white light, teaching visitors about the concept of additive color.

Liz will be at the museum in person for free family talks on July 23.

## Ant-Man, the Physics of Shrinking, and the Higgs Boson

It's simply a cross-interaction between the Higgs field and the Pym field!

## WATCH: How to detect a secret nuclear test

MinutePhysics created a simple explanation of the complicated task of detecting secret nuclear tests. There's a push underway to demand that the US and other countries legalize such inspections worldwide. Read the rest

## Neal Stephenson's Seveneves: five thousand years of apocalypse and rebirth

Neal Stephenson's no stranger to ambition, but his new novel Seveneves stretches to lengths (and heights) that beggar the imagination.

## WATCH: Matchstick rockets in super slo-mo

The Slow Mo Guys did a King of Random crossover episode, launching Grant's matchstick rockets recorded on their Phantom. Read the rest

## WATCH: Mystery of dancing colored droplets solved

Food coloring on sterile slides will spontaneously start interacting like living cells, and Stanford researchers have figured out how. Read the rest

## First-ever photo of light behaving as a wave and particle

Nicholas writes, "Since Einstein's day, scientists have been trying to directly observe the wave- and particle- aspects of light at the same time. Now, scientists at a Swiss lab have succeeded in capturing the first-ever snapshot of this dual behavior." Read the rest