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Friday FACTS: cosmic radiation

Friday Facts on a Sunday again - I'm starting to think I should just call it "facts"... Well, I'll try a little bit more, and see if I manage to get back on track with actually having FRIDAY facts on FRIDAYS again 😛
Anyway: this day started super super early; the alarm rung at 3:15, and at 7 we took off from Gardermoen airport, with Tenerife as our destination. I feel almost silly to have one week of vacation now, just after Easter, but it just had to be this way this time. Since we've been flying today, I thought the perfect theme for facts is cosmic radiation...:
    1. cosmic radiation is a mixture of particles, like protons, neutrons, alphas, and electrons, and gamma- and X-rays. Most of it comes from outside our solar system, and a small part comes from the sun 
    2. when the solar activity is high, there is more radiation coming towards the earth (since the small part that comes from the sun becomes larger 🙂 )
    3. our atmosphere works as a radiation shield for us; the cosmic rays come into it and interact, so that the rays/particles are either stopped completely, or at least lose their energy - which is a good thing for us here on Earth 🙂
    4. the intensity of the cosmic radiation changes with altitude - which is sort of logic, since you move “closer to space” if you climb up on a high mountain, or you get on a plane, so that there’s less atmosphere to stop whatever rays that are coming towards us from outer space. When you go from sea level to around 1600 meters above sea level, the intensity of the cosmic radiation doubles. If you go to 5000 meters, the radiation is 8 to 10 times more intense than at sea level, and if you’re on a plane, at 8500 meters above sea level,  the level of radiation is 40 times higher than at the ground 
    5. pilots and air attendants are actually classified as radiation workers; even though I work in a nuclear physics lab, with the cyclotron (that produces ionizing radiation), and with actual radioactive substances, they receive a higher dose each year than I have ever received 
    6. there are four factors that decides how big of a dose you will receive: solar activity (more activity from the sun means more particles bombarding Earth), time (if you spend a lot of time in a plane, 10 000 meters above sea level, you will of course receive a larger dose than if you spend little time at these altitudes), altitude (the higher you go, the more radiation - see point number 4), latitude (the shielding is better around equator that towards the poles - at typical flight altitudes, the difference between the cosmic ray dose rates at the equator and high latitudes is about a factor of two to three) 
    7. normal, average annul dose from cosmic radiation is 0.35 milli Sievert (this is not much - in Norway, we receive around 2 milli Sivert from radon gas, 0.6 from medical use, 0.55 from external gamma radiation, 0.35 from internal gamma radiation, and then just 0.35 from cosmic 😉 )
    8. the annual dose for pilots and air attendants is somewhere between 2 and 3 milli Sivert per year; which means that if you work on a plane, your dose is well below the normal annual limit for radiation workers that is 20 milli Sievert, but more than the general public is allowed to receive (still not much - it just means that the dose limits for “members of the public” is really really strict 😉 )
    9. the dose you receive on a long distance flight (like Oslo-Tokyo back and forth) is four times bigger than the total dose the average Norwegian receives from fallout from the Chernobyl accident in April 1986, from that year and 50 years into the future. (This does NOT mean that you receive a big dose from being on a plane, but that the dose we get from Chernobyl in Norway is small.)
    10. flying to the Mediterranean will get you an extra dose from cosmic radiation, equal to one meal of reindeer meat with a radioactivity of 10 000 Bq/kg. A pilot receives something equal to 100 such meals every year. If you have been scared into believing it's dangerous to eat Norwegian reindeer meat because of the radioactive downfall from Chernobyl 30 years ago, then you definitely shouldn't fly… (hint: fly as much as you want to, and eat the reindeer you want to - it's not doses that are dangerous to you; they might even be positive 🙂 )
    Back and forth to Tenerife is about 13 hours on a plane, in roughly 10 000 meters altitude. This means that when we get back to Oslo, we've all received an extra dose of radiation of 0.065 milli Sieverts (this is just a very rough average estimate, since I haven’t really taken into account where we are flying, or where in it 11-year cycle the sun is just now - I actually have no idea of that , but maybe some of you guys know? 😛 ).
    PS: I didn't manage all my goals, but at least I did "finish" my article draft, and I sent it off to supervisor Jon on Friday. Also, I'm planning on plotting some stuff while I'm here - not exactly working, but sort of maintenance 😉 

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