- #1
Jon Richfield
- 482
- 48
It seems to me that concern occasioned by the risks attendant on loss of the Earth's magnetic field is very nearly totally misplaced. Could someone please help me worry?
I realize that popular science is largely hooey, but some items are so widely circulated that it is hard to find anything authoritative to debunk it. We are told that without the Earth's magnetic field deflecting radiation from space, we would all be dead anyway, and if we were dead we wouldn't even be alive because there would be nothing for us to breathe, or something like that.!)
Now, I am sure that this makes good sense; how could it not, given that everybody knows it? And yet, the more I think about it, the more worried I am about not dying and all that. First of all, what radiation do we get from outer space? Neutrons? I hardly think so! There are not many fast neutron sources out there, especially not very close to the Earth. It would take a very, very fast neutron from say, the Sun to reach us in less than a few days, and a neutron’s half life, last time I didn't measure it, probably was around eight or 10 minutes. Never mind neutrons from neutron stars or anything like that!
So let's accept (unless you know different!) That neutrons from space are not much of a worry. The rest of the nuclear zoo have even shorter half lives, except for the commoner nuclei, especially hydrogen (a.k.a. protons, and if you like, antiprotons), helium (a.k.a. Alpha particles), electrons (and of course positrons, a.k.a. beta particles if you like), and neutrinos. Am I forgetting any of note?
Oh yes! And let's not forget all those photons bulleting at us! Mustn't forget the photons!
Now, far be it from me to be negative, positronic though my brain is not, but I find it very difficult to get excited about the protective effect of our geomagnetic field on say, neutrinos, photons and the like. They may not be indifferent to magnetic fields, but I cannot imagine their being seriously affected by Earth's magnetic field. If they were going to hit us, it would not be the geomagnetic field that would deflect them, but the atmosphere. There are certain complications of course, such as ozone, but neutrinos pass through us routinely. Quite a few sneaked through while I was writing this, and serve me right no doubt! Gammas, x-rays, and most ultraviolet rarely get very far through the troposphere; in fact, most don't get very far through the stratosphere, geomagnetic field or no geomagnetic field.
Not to make too much of a meal of it, non-charged intruders either get stopped in the atmosphere or hit us anyway.
Now the charged particles. Protons and electrons currently (suit yourself about puns) get deflected by the geomagnetic field, and spiral into entertain us with auroras in reds or blues and greens, depending on how far north or south we might be watching them. That is all very nice for people living on the equator, but for those near the poles it amounts, not so much to protection, as to concentrated incoming. Not much to thank our magnetic field for! What is it that makes me think that without the field we would get more (and more diffuse) auroras and more diffuse exposure to charged particles. And then in any case, how many protons, electrons and alphas will get through the atmosphere except as hydrogen and helium? In which form they might be expected to do exactly what harm?
I remark in passing that very likely our planet has had something like one or two thousand magnetic reversals since we (certain of our ancestors anyway) originally crawled out onto land. Each time, as far as we can tell, our projection was severely compromised at least, and yet none of our major extinctions seems to have had anything to do with space radiation. (Not that I was there to check, so if you know different, please tell us!)
Bottom line to that bit: apart from homing pigeons and Boy Scouts with pocket compasses, who should care what happens to our magnetic field? (Actually, I would, but mostly because I like homing pigeons and scouts (Girl Scouts for preference!)) and in particular I love auroras.)
Some people say that without our magnetic field, our atmosphere would be stripped away by charged particles. Perhaps, but I would love to see a cogent defence of that assertion. Surely it would be rather a slow process? After all most of the particles would simply be sopped up by the atmosphere, charged or not.
And then again, what about the ozone layer? If we removed it, as some people claim we very nearly did, that would have no effect on our ultraviolet C in the stratosphere. How much effect would it have on our flux of ultraviolet B? And ultraviolet A? One hears such dread pronouncements on how sheep will be blinded and plants will be destroyed and plankton will be wiped out, and yet all of those sound to me like rubbish!
Please correct me and tell me why I should run, not walk, to the nearest nuclear bomb shelter.
Jon
I realize that popular science is largely hooey, but some items are so widely circulated that it is hard to find anything authoritative to debunk it. We are told that without the Earth's magnetic field deflecting radiation from space, we would all be dead anyway, and if we were dead we wouldn't even be alive because there would be nothing for us to breathe, or something like that.!)
Now, I am sure that this makes good sense; how could it not, given that everybody knows it? And yet, the more I think about it, the more worried I am about not dying and all that. First of all, what radiation do we get from outer space? Neutrons? I hardly think so! There are not many fast neutron sources out there, especially not very close to the Earth. It would take a very, very fast neutron from say, the Sun to reach us in less than a few days, and a neutron’s half life, last time I didn't measure it, probably was around eight or 10 minutes. Never mind neutrons from neutron stars or anything like that!
So let's accept (unless you know different!) That neutrons from space are not much of a worry. The rest of the nuclear zoo have even shorter half lives, except for the commoner nuclei, especially hydrogen (a.k.a. protons, and if you like, antiprotons), helium (a.k.a. Alpha particles), electrons (and of course positrons, a.k.a. beta particles if you like), and neutrinos. Am I forgetting any of note?
Oh yes! And let's not forget all those photons bulleting at us! Mustn't forget the photons!
Now, far be it from me to be negative, positronic though my brain is not, but I find it very difficult to get excited about the protective effect of our geomagnetic field on say, neutrinos, photons and the like. They may not be indifferent to magnetic fields, but I cannot imagine their being seriously affected by Earth's magnetic field. If they were going to hit us, it would not be the geomagnetic field that would deflect them, but the atmosphere. There are certain complications of course, such as ozone, but neutrinos pass through us routinely. Quite a few sneaked through while I was writing this, and serve me right no doubt! Gammas, x-rays, and most ultraviolet rarely get very far through the troposphere; in fact, most don't get very far through the stratosphere, geomagnetic field or no geomagnetic field.
Not to make too much of a meal of it, non-charged intruders either get stopped in the atmosphere or hit us anyway.
Now the charged particles. Protons and electrons currently (suit yourself about puns) get deflected by the geomagnetic field, and spiral into entertain us with auroras in reds or blues and greens, depending on how far north or south we might be watching them. That is all very nice for people living on the equator, but for those near the poles it amounts, not so much to protection, as to concentrated incoming. Not much to thank our magnetic field for! What is it that makes me think that without the field we would get more (and more diffuse) auroras and more diffuse exposure to charged particles. And then in any case, how many protons, electrons and alphas will get through the atmosphere except as hydrogen and helium? In which form they might be expected to do exactly what harm?
I remark in passing that very likely our planet has had something like one or two thousand magnetic reversals since we (certain of our ancestors anyway) originally crawled out onto land. Each time, as far as we can tell, our projection was severely compromised at least, and yet none of our major extinctions seems to have had anything to do with space radiation. (Not that I was there to check, so if you know different, please tell us!)
Bottom line to that bit: apart from homing pigeons and Boy Scouts with pocket compasses, who should care what happens to our magnetic field? (Actually, I would, but mostly because I like homing pigeons and scouts (Girl Scouts for preference!)) and in particular I love auroras.)
Some people say that without our magnetic field, our atmosphere would be stripped away by charged particles. Perhaps, but I would love to see a cogent defence of that assertion. Surely it would be rather a slow process? After all most of the particles would simply be sopped up by the atmosphere, charged or not.
And then again, what about the ozone layer? If we removed it, as some people claim we very nearly did, that would have no effect on our ultraviolet C in the stratosphere. How much effect would it have on our flux of ultraviolet B? And ultraviolet A? One hears such dread pronouncements on how sheep will be blinded and plants will be destroyed and plankton will be wiped out, and yet all of those sound to me like rubbish!
Please correct me and tell me why I should run, not walk, to the nearest nuclear bomb shelter.
Jon
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