[notum]

Cosmic rays are, or rather were, the reason why manufactures avoid shipping high end cameras by plane, cosmic rays kill pixels in imaging sensors: https://youtu.be/98FZ8C6HneE?t=479

It's also the reason why all ISS footage has dead pixels on it.

[thamer]

Astronauts[1] also report seeing random flashes of light from time to time, believed to be due to high-energy particles interacting with their optical nerves, or cells in the retina, or maybe neurons too. Space is not a very friendly environment.

This is somewhat similar – although on a much different scale – to when Anatoli Bugorski[2] had an accident in 1978 involving a beam of protons traveling at over 99% the speed of light going through his head. He also described it as a flash "brighter than a thousand suns".

[1] https://en.wikipedia.org/wiki/Cosmic_ray_visual_phenomena

[2] https://en.wikipedia.org/wiki/Anatoli_Bugorski

[dekhn]

When I was a postdoc at berkeley I was talking to the head of the bioengineering department who mentioned the phenomena. He had actually written a paper in which he put an appropriate set of filters in front of a particle accelerator to ensure that a statistical photon was emitted at a specific frequency (IE, it output 1 photon/sec, although only on average). Then he sat in front of the filters at looked into the accelerator.

https://www.nytimes.com/1971/03/04/archives/space-lights-tra...

Still one of the most audacious things I've seen, but he was a good physicist and did the math right, so he wasn't being unsafe.

[Natfan]

Unrelated tangent, but this is the third time in two days that I've seen Anatoli Burgorski be mentioned. Twice on HN, once on YT.

I guess I'm just noticing his name more?

[woodruffw]

This is a fascinating claim (and video), but I can't find a ton of corroborating evidence for it: searches for "digital camera cosmic rays" bring up (1) considerations for cameras in space (much higher background radiation levels than a commercial flight), and (2) consumer photography forums where people are discussing that 2011 talk. Some of the latter seem to think that Kodak has/had a vested interest in spreading fear around digital photography, since their analog division was imploding at the time.

[sandworm101]

Any ray that might damage a ccd would also impact film stock, exposing sections into bright dots. Did kodak also not ship film by air?

[notum]

Not really, no. It might be too brief to cause a chemical reaction, but powerful enough to induce a very high voltage.

[jmcqk6]

Does anyone know how this works with our space-based telescopes? Or even our mountain top observatories? Surely if it's this crazy, they have to deal with that as well?

[reportingsjr]

Yes, the electronics, including imaging sensors are all radiation hardened.

This can involve things such as using digital circuits that are radiation resistant (e.g. look up radiation resistant flip flop). Using multiple computers running the same thing that all "vote" for the correct result, so if one computer has an error from radiation you don't suffer. Using semiconductors that are more resistant to radiation (larger band gaps mean more energy required to flip a bit).

Physical shielding is key as well. The infrared imager on the Cassini probe had a case made out of tantalum, as tantalum is a very dense material which prevents a lot of radiation from going through it.

[KMag]

Also, larger feature nodes mean more capacitance, so a lower voltage spike and more area to dissipate the same amount of absorbed energy.

[supernova87a]

Well one thing they also do is that pretty much any desired image is taken multiple times/multiple exposures, and multiple offset positions in close succession to remove exactly such artifacts. The images are then stacked, etc.

So this allows removal of effects that do not correlate with what is physically should be in the image, but is an artifact of the sensor, image system, etc:

-- sensor artifacts: dead pixels, flat field irregularity, pixel response variations, electronic noise

-- imaging system issues: optical problems, lens/mirror defects

-- and then exactly what's being discussed here: cosmic rays, transient objects (satellite tracks!)

[rambojazz]

Interesting, where can I see an example of the ISS footage with dead pixels? I've never noticed them before.

[notum]

https://www.youtube.com/watch?v=QvTmdIhYnes

Modern camera firmware detects stuck and dead pixels and tries to fill them in with neighbor data., but when there's too many... there's not enough data to fill in.

Keep watching top left part of the video. Most visible at 0:30.

[petertodd]

Actually at the very end when they go into a dark place is the most visible. The whole sensor is covered with defects.

[rambojazz]

Maybe it's me, maybe it's the screen, I can barely spot any dead pixel at the 00:30 mark. But at the end of the video it's very clear. Thanks for pointing it out.

[hnick]

Does this apply to human retinas too?

[andy_ppp]

Very interesting, so should people who travel with photography equipment take night flights if possible?

[notum]

Rays hit our planet regardless of Sun, if anything it might block a few. They are caused by ultra-energetic cosmic events, such as star collisions, black hole feeding cycles.

Cosmic rays are just very potent photons, capable of knocking out electrons from an atom (meaning they are ionizing) causing havoc in precision electronics and, well, our DNA.

[andy_ppp]

What is the tolerance for cosmic rays for a human... I ask because on the journey to Mars you’ll get quite a few I guess and also on the planet’s surface after you’re there with such a thin atmosphere?

[tinco]

This is actually a thing people are criticizing Musk for, he is being accused of sending people to Mars with insufficient shielding against cosmic rays.

In my opinion it's a bit silly argument, as there's a whole bunch of other risks and quality of life sacrifices made by the persons who are going to undertake that journey. Some raised chance of cancer is probably the least of their worries.

[mlindner]

He can't send people to Mars yet so how are people accusing him of sending people to mars with insufficient shielding? There are limits to criticism of Musk one would think.

[typon]

Humans going to Mars should expect to never come back

[andi999]

But at least they should reasonably expect to arrive.

[Sanzig]

That's actually a fascinating question! It turns out we don't know enough to answer one way or another.

The model commonly used in radiation protection to assess cancer risk with respect to radiation dose is called the Linear No-Threshold (LNT) model [1]. The model critically assumes that (1) total radiation dose is the only predictor of cancer risk, and (2) any radiation exposure results in an increased cancer risk.

This model works at high absorbed doses, however, its applicability is highly controversial when used with low abosorbed doses or with relatively high absorbed doses that occur over a long period of time (ie: low dose rate).

The thing is, the human body has built-in defense mechanisms against cancer such as DNA repair. There is a good body of evidence that small doses and low-rate exposures do not result in cancer risk (ie: there is a threshold absorbed dose and probably also a threshold dose rate), but the model does not account for this.

This is particularly problematic when trying to assess excess mortality from things such as radiological accidents: when you multiply the small LNT-predicted risk for a low dose times a very large population, you end up with a lot of cancers. This is one of the reasons you'll see estimates for deaths from the Chernobyl accident vary by orders of magnitude.

It's also problematic when assessing something like a Mars mission: yes, the astronauts would get large cumulative doses, but the dose rate is pretty low over most of the mission (other than during high dose rate solar events where they would need radiation shielding). How much of an elevated cancer risk is it actually? Nobody is quite sure.

[1] https://en.wikipedia.org/wiki/Linear_no-threshold_model

[andi999]

I remember vaguely that if there would have been a sun eruption at the lunar mission the team might have died. I tried a while ago to find a good source on that though. If this were true, forget Mars.

[btkramer9]

As far as cancer rates go I've heard it's about as bad as taking up smoking cigarettes. Which is not great but doesn't seem like a show stopper

[MauranKilom]

According to https://xkcd.com/radiation/, you get about 4x the normal daily background radiation from a transamerican flight.

[moftz]

Cosmic rays can also be high energy ions. Most of the photons come from the sun and the ions can come from outside the universe and the sun.

[foxyv]

Cosmic rays are not exclusively associated with the sun. There are a lot of Galactic Cosmic Rays still. It's pretty much leftovers from supernovae, black hole mergers, neutron stars, accretion disks and such. But yeah, at night would be better.

Edit: Correction, there is very little difference and fewer cosmic rays during the day. Source: https://arxiv.org/pdf/physics/0105005.pdf