This week's guest video comes from Active Galactic Videos: go subscribe! https://www.youtube.com/ActiveGalacticVideos/ They got to walk on the dish of a telescope: https://www.youtube.com/watch?v=1lfXsN45088 At the Richard F. Caris Mirror Lab, under the football stadium of the University of Arizona, there's an enormous rotating furnace, keeping tonnes of glass heated as it forms the mirrors for the Giant Magellan Telescope. Here's a look inside!

In Göttingen, Germany, there's a four-tonne steel ball that can be raised up a 14-metre tower -- and then dropped in less than two seconds, crashing back to earth. It makes tiny, artificial earthquakes: here's why. Thanks to all the team at Wiechert'sche Erdbebenwarte Göttingen! You can find out more about them here: https://www.erdbebenwarte.de/ Three things I had to cut out of this video, because they didn't quite fit into the story or because I couldn't film them: The reason the steel ball

Thanks to the Starrship team for arranging this! I'm also over on their channel, flying with the Blades: https://www.youtube.com/watch?v=iWY3-1gOrxk • At the Royal Air Force training centrifuge in Farnbrough, pilots learn how to avoid G-LOC: g-induced loss of consciousness. Let's talk about g-force, about jerk, and about how to keep circulation flowing to your brain. FAQs: * Isn't 3.6g a really low g-tolerance? * Yep. Turns out I would not qualify to be a fighter pilot. The average range for g

If you're in Canada, you need good winter boots. But how do you know whether they're actually safe, or whether you'll fall over the first time you step on ice? This is WinterLab, part of the Challenging Environment Assessment Laboratories at the Toronto Rehabilitation Institute, where they're testing winter shoes with science. More about the lab and their ratings: http://www.ratemytreads.com/ Thanks to Evan from Rare Earth for being camera op! https://www.youtube.com/channel/UCtGG8ucQgEJPeUPhJ

At Reed College in Portland, Oregon, there's a TRIGA nuclear reactor, used for research. You can stand next to it and watch the blue glow from the bottom of a deep swimming pool. I had to visit. More about the reactor and about Reed College: https://reactor.reed.edu/ Edited by Michelle Martin (@mrsmmartin) Post audio by Emi Paternostro (http://proximitysound.com) I'm at http://tomscott.com on Twitter at http://twitter.com/tomscott on Facebook at http://facebook.com/tomscott and on Snapchat an

The Global Vehicle Target is the new standard for testing autonomous driving and crash test systems. To cameras and radar, it looks like a car: but if you hit it, it'll fly apart. So if your emergency braking doesn't quite work... well, this is what happens. Thanks to everyone at Thatcham Research! You can find out more about them at https://www.thatcham.org/ and about the target at https://www.thatcham.org/car-safety/driver-assistance/ Filmed by Tomek: https://youtube.com/tomek Edited by Mich

Subscribe to Neuro Transmissions! https://www.youtube.com/user/neurotransmissions or start with their video on how to train a cat to high-five: https://www.youtube.com/watch?v=VfsVw0ndFAQ We're all used to seeing MRI scans of brains. But how do they work? Can you really "see" brain activity, or read someone's mind? Alie and Micah from Neuro Transmissions went to get scanned -- and ended up having some fun with 3D printing, too.

The Forbes Pigment Collection at the Harvard Art Museums is a collection of pigments, binders, and other art materials for researchers to use as standards: so they can tell originals from restorations from forgeries. It's not open to the public, because it's a working research library -- and because some of the pigments in there are rare, historic, or really shouldn't be handled by anyone untrained.

The Multi-Axes Rotation and Tilt Device (MART) is used for spatial orientation experiments: it's a chair balanced on a metaphorical knife-edge, powered by precise and fast motors. And my job was to not fall over.

In the Ashton Graybiel Spatial Orientation Laboratory at Brandeis University, there's the Artificial Gravity Facility: otherwise known as the rotating room. No-one's invented futuristic gravity plating yet, but if you want to test how humans would cope with artificial gravity, this is the best way.

At the University of Canterbury, in Christchurch, New Zealand, the team at Mars Bioimaging are using detector equipment originally developed for the Large Hadron Collider, and putting it to a very different use: medical imaging that allows 3D, false-color images inside the human body.

If you invent a new theme park or amusement ride, how do you test it to make sure it's safe? There's no Federal Bureau of Zip Lines. I visited one of the companies that does just that sort of testing - and, now, inventing.

"Build some models" seems obvious: but this is a story of ingenuity, of using natural resources well, and of a country that humans dragged from the sea.

Turns out that trying to precisely detect fire from space is more difficult than "point a camera at it".

NERC's Space Geodesy Facility, hidden away in the English countryside, fires lasers at satellites. Because it turns out that knowing a satellite's position exactly is really, really difficult. More about the Facility: http://sgf.rgo.ac.uk/