Solar Eclipse

'Physics for Cats' is my next collection of science cartoons. It'll be out in the autumn. More details and an excerpt are here: www.drawnandquarterly.com/books/physics-for-cats/

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When a physicist falls in love :)

Richard Feynman's love letter to his deceased wife, 1946.

general relativity for babies

The Mermaid Nebula Supernova Remnant Image Credit: Neil Corke

Okay so a guy in my solid state physics class was telling us about this muon scanning startup he worked at, GScan, and I'm going insane. I don't work there and I have no stake in the company, financial or otherwise, I just need to tell you about it.

Muons are short-lived subatomic particles, same charge as an electron but ~200 times more massive. On Earth, they're produced by cosmic rays colliding with the upper atmosphere, and they hit the ground at a rate of about ten thousand per minute per square meter.

They're moving extremely fast at ground level, like 0.99 c. So they careen right through matter, deflecting only very slightly around heavy atomic nuclei – they'll penetrate like a hundred meters into solid rock.

What do you do with this continuous shower of deep-penetrating charged particles, constantly blanketing every square inch of the Earth's surface?

(source)

The classic thing is use them to image the inside of massive structures, like we use x-rays to look inside living tissue – except instead of generating them yourself, you just use atmospheric muons. Muon archeology is a whole thing, they've used it to find hidden chambers in pyramids and stuff. Neat!

But this one Estonian company is doing some crazy bullshit and I love it.

Sandwich anything between a pair of portable muon detectors and get full 3D imaging of the interior, with sub-millimeter accuracy, by tracking the minute deflection of muons between them. Samples that are WAY too thick for x-rays, made of literally anything. Just put some muon detectors on some two by fours in a warehouse and call it a day.

You can just. Image anything??? Anything you want?? Completely passively!! Just detectors! No particle source! Put them anywhere. The detectors themselves are a mature technology, the company's tech is in the algorithms they use to get this level of spatial and elemental resolution.

You can detect failures inside cable-reinforced concrete bridges without cutting open the bridges.

Decommissioned Soviet nuclear submarine filled with concrete, with no drawings or documentation, that may or may not have spent fuel canisters in it? And you need to cut it up for storage? Just look at the muons.

One of the wackiest ideas is to put one detector under your bed and one on the ceiling, so you get a full 3D scan of your body every night, passively. I want one.

The Moon Dressed Like Saturn ©

NGC 2244, Cosmic Rose