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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: 2) by Immerman on Friday March 15 2019, @04:04PM (3 children)
Quite so. I went back and added the two that I had forgotten, and then adjusted the result in the wrong direction. Except, actually it was the *right* direction (increasing the power decreases time needed to to receive X energy) , and the rest of my math was completely wrong. Too early for math I guess. Really need to remember to always put in my units and make sure they cancel properly for sanity checking
So, the proper calculation should be:
time needed = total energy needed / power influx:
so 1.6e26 J (energy needed to vaporize ocean) / 1.7e17 J/s (total solar power hitting Earth, from the table) = 941e6 seconds = 29 years
Which is also a lot closer to my original expectations.
So, pile on enough greenhouse-effect insulation, and it would take less than a century to *completely* vaporize the Earth's oceans.
(Score: 0) by Anonymous Coward on Friday March 15 2019, @04:37PM (2 children)
Yes, that matches with the "Total energy from the Sun that strikes the face of the Earth each year" I see there now.
I hadn't thought of this before. So there is an observable drop in the amount of radiation leaving the earth when viewed from space? I.e., earth would actually appear cooler when measured remotely?
(Score: 2) by Immerman on Friday March 15 2019, @04:56PM (1 child)
Well, it depends on exactly what you're asking.
So long as a planet is in thermal equilibrium (i.e. not currently heating or cooling) it will always emit *exactly* 100% as much average energy as it's receiving from the sun. Any less, and that excess energy must be accumulating on the planet, causing warming.
If instead you're talking about the current situation, then yes - the increase in greenhouse gasses will make the planet look slightly dimmer, until such time as the planet warms enough to once again be able to radiate energy as fast as it's coming in.
(Score: 2) by Immerman on Friday March 15 2019, @04:59PM
It's worth mentioning that at the current thermal discrepency though the imbalance in received versus radiated light is *tiny* - it's only the truly mind-boggling absolute amount of solar energy hitting the Earth that allows a tiny imbalance to cause as much heating as we're seeing.