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Long lines. Narrow seats. Baggage fees. You recognize this list. It's the downside of flying on modern commercial airlines. And now we have a new item to add: neutrons.
Spaceweather.com and Earth to Sky Calculus have just completed a 5-continent survey of cosmic ray neutrons at aviation altitudes. From Dec. 2018 through Feb. 2019, Hervey Allen of the University of Oregon's Network Startup Resource Center carried Earth to Sky radiation sensors including neutron bubble chambers onboard commercial flights from North America to Europe, Africa, South America and Asia. Neutrons from deep space were detected on every flight.
Hervey logged 83 hours in the air as he traveled 41,500 miles above 30,000 feet. For reference, that's almost twice the circumference of the Earth. The entire time, he gathered data on X-rays, gamma-rays and neutrons in an energy range (10 keV to 20 MeV) similar to that of medical radiology devices and "killer electrons" from the Van Allen Radiation Belts.
The results were eye-opening. During the trip, Hervey recorded 230 uGy (microGrays) of cosmic radiation. That's about the same as 23 panoramic dental x-rays or two and a half chest X-rays. Moreover, 41% of the dose came in the form of neutrons. This confirms that cosmic-ray neutrons are abundant at aviation altitudes and must be considered in any discussion of "Rads on a Plane."
https://spaceweatherarchive.com/2019/03/12/neutrons-detected-on-commercial-airplane-flights/
(Score: 5, Insightful) by Immerman on Friday March 15 2019, @04:50PM (6 children)
I didn't realize that SN was populated primarily by particle physicists.
Experts take all sorts of linguistic short-cuts when talking amongst themselves. When talking to laymen however, it's important to not do that or you just spread confusion and misinformation.
(Score: 1, Flamebait) by PiMuNu on Friday March 15 2019, @05:03PM (5 children)
Sorry for confusing all you laymen. I think it's pretty obvious what is meant however, even to people so uninformed as SN readers.
(Score: 2) by TrentDavey on Friday March 15 2019, @05:24PM (1 child)
I didn't really understand the original since I thought neutrons didn't interact with much and I thought cosmic rays were solar system source gamma rays and I'm a physics lab demonstrator. It never hurts to form your responses with people in mind who don't travel in the same circles as you do. Otherwise, how are others to understand and learn? Kinda of a Catch-22.
(Score: 3, Informative) by Immerman on Friday March 15 2019, @05:46PM
Well, if you're a demonstrator these details may come up at some point, so let me correct you a bit:
You're right about neutrons not interacting much, they pretty much have to collide head-on with the infinitesimally small nucleus of an atom to interact at all. So, once they're produced they tend to travel in a straight line until they either hit something very dense (like lead, or fission fuel), where the odds of a nucleus being directly in their path are high, or until they decay into a proton and electron after an average of about 14.4 minutes (average_life = sqrt(2)*half_life)
Cosmic rays though are high-energy particle radiation (mostly protons and atomic nuclei, often traveling at relativistic velocities) primarily originating outside the solar system (hence "cosmic"), that are believed to mostly originate from supernovas.
Gamma rays in contrast are photons high-energy electromagnetic radiation that originate primarily from nuclear reactions and decays of any type. Space is full of those *too*, since any gamma ray that escapes a star will keep traveling just like the visible light does, but they don't really have anything to do with cosmic rays. Those with an extra-solar origin tend to come from neutron stars, pulsars, supernovae, and other ultra-hot objects that trigger extreme levels of nuclear reactions near their surface where the photons can escape easily.
(Score: 3, Insightful) by Immerman on Friday March 15 2019, @05:30PM (2 children)
Really? You think most SN readers are aware that the half-life of a neutron is such that such low-energy neutron radiation couldn't possibly be cosmic rays and must be secondary radiation?
Now, we have a bunch of clever people here, that's a big part of the reason I take part in the discussions. But there's still a limit to how much random science trivia any one person can hold in their head. Based on my conversations, I really doubt more than maybe 10-20% of Soylentils are well versed enough in nuclear physics to spot the error.
(Score: 0) by Anonymous Coward on Saturday March 16 2019, @03:34AM
I studied astrophysics for my BS and I did not know that answer. Seriously wtf?
(Score: 2) by PiMuNu on Monday March 18 2019, @09:34AM
Sorry I shouldnt have been sarcastic.