What-If 0073: "Lethal Neutrinos"

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What-If 0073: "Lethal Neutrinos"

Postby Earthling on Mars » Tue Nov 26, 2013 2:37 pm UTC

Lethal Neutrinos
How close would you have to be to a supernova to get a lethal dose of neutrino radiation?

(Overheard in a physics department)


Image

Survive being inside a sun, only to die at the hands of infinitesimal particles. What a way to go. Now, where does "lethal neutrinos" belong in http://xkcd.com/1242/?

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Re: What-If 0073: "Lethal Neutrinos"

Postby Klear » Tue Nov 26, 2013 2:40 pm UTC

The best part of this what-if are the mouseover texts. Especially the last one.

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Re: What-If 0073: "Lethal Neutrinos"

Postby Vroomfundel » Tue Nov 26, 2013 2:47 pm UTC

A post about neutrinos hitting earth without a reference to the Hitchhiker's Guide to the Galaxy? What a waste.

This also reminded me of a quotation from a physicist who introduced the neutrino but now I can't find it anymore. Maybe it was Fermi but I'n not quite sure. The quote something like "I've committed the ultimate sin in physics - I've introduced an undetectable particle". It was later detected though so all was fine eventually.
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Re: What-If 0073: "Lethal Neutrinos"

Postby biggles1 » Tue Nov 26, 2013 2:48 pm UTC

I can't hear 'Neutrinos' anymore without being reminded of that godawful plot device in the film 2012.

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Re: What-If 0073: "Lethal Neutrinos"

Postby I-ku-u » Tue Nov 26, 2013 2:50 pm UTC

I think Randall needs to check his calculator, as 0.00001118 is most definitely not the square root of 10-10. Not that that materially affects the result of 2.3AU :-)

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Re: What-If 0073: "Lethal Neutrinos"

Postby davidstarlingm » Tue Nov 26, 2013 3:15 pm UTC

Being beaten to death with neutrinos is kind of an awesome way to die. Especially given that it's rather difficult to block neutrinos.

Can anything shield you from neutrinos?

I probably should have considered this more thoroughly when we wrote this chapter (where SSj2 Vegeta manages to produce an energy shield around part of a planet during a nova).

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Re: What-If 0073: "Lethal Neutrinos"

Postby Half-Borg » Tue Nov 26, 2013 3:25 pm UTC

The best What-if in MONTHS!
But I'm curoius what would happen to you, if you got that much neutrions. Is it just like any other type of radioation?

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Re: What-If 0073: "Lethal Neutrinos"

Postby Adam H » Tue Nov 26, 2013 3:48 pm UTC

Wait, so is it (sort of) accurate to say that our sun going supernova would exert a billion times more energy on a person than if a nuclear bomb exploded directly on top of that person? That's a fun thing to say.
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Re: What-If 0073: "Lethal Neutrinos"

Postby Diadem » Tue Nov 26, 2013 3:48 pm UTC

I knew supernovae were big, but I had no idea they were that big. 9 orders of magnitude bigger at 1 AU than a nuclear bomb pressed against your eye? That's just sick.

davidstarlingm wrote:Can anything shield you from neutrinos?

No. The best part of neutrino radiation is in fact that any form of shielding makes the problem worse. The fraction stopped by your shield is negligible (unless your shield is like a billion miles of solid lead), so you still have to deal with all the neutrinos, but now you also have to deal with the radiation the shield is giving off due to neutrinos hitting it.
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Re: What-If 0073: "Lethal Neutrinos"

Postby airdrik » Tue Nov 26, 2013 3:53 pm UTC

Half-Borg wrote:But I'm curoius what would happen to you, if you got that much neutrions. Is it just like any other type of radioation?

I wondered that as well. After all, there are different kinds of radiation: alpha and beta particles, x-rays, gamma rays, billy rays, hawking radiation, Čerenkov radiation, tsvetanov radiation, neutrinos (which don't seem to do much other than flip bits in random hard drives). Each of these has different penetration power and effects on the body (younger billy rays are known to increase growth of hair in the back of the head).

I have discovered a little known fact1 about neutrinos: If you manage to get around 0.5 Sv of Neutrino radiation it will cure cancer, Parkinson's, Alzheimer's and the common cold. You can get it at around 0.000031622777 parsec, or 6.5 AU from the supernova. Good luck! (at least you get to start from outside the giant star in question)

1 Yup, I made that one up all by myself. Feel free to disseminate

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Re: What-If 0073: "Lethal Neutrinos"

Postby Klear » Tue Nov 26, 2013 4:40 pm UTC

Diadem wrote:I knew supernovae were big, but I had no idea they were that big. 9 orders of magnitude bigger at 1 AU than a nuclear bomb pressed against your eye? That's just sick.

davidstarlingm wrote:Can anything shield you from neutrinos?

No. The best part of neutrino radiation is in fact that any form of shielding makes the problem worse. The fraction stopped by your shield is negligible (unless your shield is like a billion miles of solid lead), so you still have to deal with all the neutrinos, but now you also have to deal with the radiation the shield is giving off due to neutrinos hitting it.


Maybe you could put a strong gravitational anomaly in front of yourself to bend space and make the neutrinos go around you? Seems to me like something you could do if you had alcubierre drive-type technology.

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Re: What-If 0073: "Lethal Neutrinos"

Postby jgh » Tue Nov 26, 2013 4:51 pm UTC

"Supernovii" is discouraged.

"Supernovii" are discouraged, surely.

ducks and hides

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Re: What-If 0073: "Lethal Neutrinos"

Postby Trickster » Tue Nov 26, 2013 5:01 pm UTC

I came here hoping someone would explain why ln(x)^e approaches x. As a computer scientist, I haven't done derivatives in years and I'm predisposed to keep it that way while the streak is hot.

(I adore math and study it on my own, but I prefer mathematical theories which have virtually no applications. The calculus of limits is far too useful.)

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Re: What-If 0073: "Lethal Neutrinos"

Postby Trickster » Tue Nov 26, 2013 5:12 pm UTC

jgh wrote:
"Supernovii" is discouraged.

"Supernovii" are discouraged, surely.

"Supernovii", our; discouraged?

Our supernovii, discouraged? It's more likely than you think. Click here.

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Re: What-If 0073: "Lethal Neutrinos"

Postby rhomboidal » Tue Nov 26, 2013 5:14 pm UTC

It makes me both happy and sad to imagine that stars actually shout "NEUTRINOS!" when they go supernova -- but in the silent void of space, no one is able to hear it.

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Re: What-If 0073: "Lethal Neutrinos"

Postby ModoTheGreat » Tue Nov 26, 2013 5:19 pm UTC

Trickster wrote:I came here hoping someone would explain why ln(x)^e approaches x.


if e^a = x, then a = ln(x).
So if e^a = x, what's ln(x)^e = a^e ?

In other words, the two formulae (yup, I did) don't actually approach one another as such.


A better question would be why or where you'd ever need to to know the solution to ln(x)^e...

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Re: What-If 0073: "Lethal Neutrinos"

Postby MartianInvader » Tue Nov 26, 2013 7:41 pm UTC

I believe the derivative is eln(x)e-1/x, correct?
Let's have a fervent argument, mostly over semantics, where we all claim the burden of proof is on the other side!

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Re: What-If 0073: "Lethal Neutrinos"

Postby davidstarlingm » Tue Nov 26, 2013 7:51 pm UTC

Adam H wrote:Wait, so is it (sort of) accurate to say that our sun going supernova would exert a billion times more energy on a person than if a nuclear bomb exploded directly on top of that person? That's a fun thing to say.

It may be even more energy. I don't know that brightness and energy are directly proportional. I'd figure it out, but I'm not entirely sure which definitive quantity Randall means by "brightness" in the what-if.

Diadem wrote:
davidstarlingm wrote:Can anything shield you from neutrinos?

No. The best part of neutrino radiation is in fact that any form of shielding makes the problem worse.
You have a strange definition of "best".

Diadem wrote:The fraction stopped by your shield is negligible (unless your shield is like a billion miles of solid lead), so you still have to deal with all the neutrinos, but now you also have to deal with the radiation the shield is giving off due to neutrinos hitting it.

Klear wrote:Maybe you could put a strong gravitational anomaly in front of yourself to bend space and make the neutrinos go around you?

Hmm. A forcefield approach is definitely better than a shielding approach. Neutrinos are supposed to have a small magnetic moment, right? Perhaps they could be deflected with a properly-designed magnetic field. Perhaps the weak interaction could even be used.

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Re: What-If 0073: "Lethal Neutrinos"

Postby jay35 » Tue Nov 26, 2013 7:55 pm UTC

This is fantastic: http://what-if.xkcd.com/imgs/a/73/neutrinos_bomb.png

I'd say I'd like it on a t-shirt but you could never wear it in public these days given the climate of fear that would cause false alarms. =\

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Re: What-If 0073: "Lethal Neutrinos"

Postby Klear » Tue Nov 26, 2013 8:18 pm UTC

jay35 wrote:This is fantastic: http://what-if.xkcd.com/imgs/a/73/neutrinos_bomb.png

I'd say I'd like it on a t-shirt but you could never wear it in public these days given the climate of fear that would cause false alarms. =\


Without context it looks like he wants to eat it.

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Re: What-If 0073: "Lethal Neutrinos"

Postby Pfhorrest » Tue Nov 26, 2013 8:39 pm UTC

Now I'm wondering about the physics of that feather knocking you over. It seems like it would be similar to the can-you-boil-tea-by-stirring question. Sure, you could take sufficient energy to boil the tea and impart it via a stirring motion... but as a consequence of other factors you're not going to have a cup of tea left to boil after doing that for long. Likewise, say you somehow accelerated a feather to have a momentum sufficient to knock a person over, and let's do this in a vacuum so we don't have a shockwave of air complicating the matter. The feather hits the person and... what exactly is their collision like? Certainly it won't be perfectly elastic and just impart all the feather's momentum uniformly to the person's body, knocking them cleanly back. Part of the feather and part of the person will likely crumple, shatter, or otherwise take that energy and do something other than send the person flying back. Would the feather punch through the person like a (certain kind of) bullet? Would it shatter on impact and blow a crater at the point of contact?
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Re: What-If 0073: "Lethal Neutrinos"

Postby Gralphidb » Tue Nov 26, 2013 10:37 pm UTC

I believe that Randall's comparison of the brightness of a Supernova at the distance of the sun vs. the brightness of a nuclear bomb in front of your face is flawed. It looks like he compared energy outputs instead of apparent magnitudes for the supernova, which results in significant errors, since supernova glow for several weeks. Using an energy of 1 foe (10^51 ergs) and then scaling for distance (using the inverse scale law) and comparing with the largest nuclear weapon's energy of roughly 210,000 kilojoules at a distance of 1 cm, you do get a factor of around 10^9 times brighter.

However, if you instead use a supernova's peak absolute magnitude of around -22, and thus a resulting apparent magnitude of around -53 (at a distance of 1 AU), you get an energy output of 1.4 *10^44 ergs/second. Assuming a nuke releases all of its energy in one second (I don't know if that's true, but it sounds right. I do astronomy, not nuclear weapons testing :D), you get that a supernova at the distance of the sun is roughly 300 times brighter than a nuclear bomb in front of your eye. So still quite a bit brighter, but not that much brighter!

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Re: What-If 0073: "Lethal Neutrinos"

Postby davidstarlingm » Tue Nov 26, 2013 10:50 pm UTC

Pfhorrest wrote:Now I'm wondering about the physics of that feather knocking you over. It seems like it would be similar to the can-you-boil-tea-by-stirring question. Sure, you could take sufficient energy to boil the tea and impart it via a stirring motion... but as a consequence of other factors you're not going to have a cup of tea left to boil after doing that for long. Likewise, say you somehow accelerated a feather to have a momentum sufficient to knock a person over, and let's do this in a vacuum so we don't have a shockwave of air complicating the matter. The feather hits the person and... what exactly is their collision like? Certainly it won't be perfectly elastic and just impart all the feather's momentum uniformly to the person's body, knocking them cleanly back. Part of the feather and part of the person will likely crumple, shatter, or otherwise take that energy and do something other than send the person flying back. Would the feather punch through the person like a (certain kind of) bullet? Would it shatter on impact and blow a crater at the point of contact?

Two What-ifs I would like to see examined:

Can you really knock someone over with a feather?

How many straws does it take to break a camel's back?

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Re: What-If 0073: "Lethal Neutrinos"

Postby Klear » Tue Nov 26, 2013 11:33 pm UTC

Pfhorrest wrote:Now I'm wondering about the physics of that feather knocking you over. It seems like it would be similar to the can-you-boil-tea-by-stirring question. Sure, you could take sufficient energy to boil the tea and impart it via a stirring motion... but as a consequence of other factors you're not going to have a cup of tea left to boil after doing that for long. Likewise, say you somehow accelerated a feather to have a momentum sufficient to knock a person over, and let's do this in a vacuum so we don't have a shockwave of air complicating the matter. The feather hits the person and... what exactly is their collision like? Certainly it won't be perfectly elastic and just impart all the feather's momentum uniformly to the person's body, knocking them cleanly back. Part of the feather and part of the person will likely crumple, shatter, or otherwise take that energy and do something other than send the person flying back. Would the feather punch through the person like a (certain kind of) bullet? Would it shatter on impact and blow a crater at the point of contact?


Yeah, it made me think of this.

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Re: What-If 0073: "Lethal Neutrinos"

Postby richP » Tue Nov 26, 2013 11:58 pm UTC

"Karman calculates that the neutrino radiation dose at a distance of one parsec[6] would be around..."

Hah! don't you idiots realize a parsec is a unit of... oh wait, he used it correctly! Never mind!

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Re: What-If 0073: "Lethal Neutrinos"

Postby Jackpot777 » Wed Nov 27, 2013 12:30 am UTC

Pfhorrest wrote:Now I'm wondering about the physics of that feather knocking you over. It seems like it would be similar to the can-you-boil-tea-by-stirring question. Sure, you could take sufficient energy to boil the tea and impart it via a stirring motion... but as a consequence of other factors you're not going to have a cup of tea left to boil after doing that for long. Likewise, say you somehow accelerated a feather to have a momentum sufficient to knock a person over, and let's do this in a vacuum so we don't have a shockwave of air complicating the matter. The feather hits the person and... what exactly is their collision like? Certainly it won't be perfectly elastic and just impart all the feather's momentum uniformly to the person's body, knocking them cleanly back. Part of the feather and part of the person will likely crumple, shatter, or otherwise take that energy and do something other than send the person flying back. Would the feather punch through the person like a (certain kind of) bullet? Would it shatter on impact and blow a crater at the point of contact?


All depends on the size of the feather... I think it'll bend a little.

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Re: What-If 0073: "Lethal Neutrinos"

Postby rmsgrey » Wed Nov 27, 2013 12:37 am UTC

Klear wrote:
Diadem wrote:I knew supernovae were big, but I had no idea they were that big. 9 orders of magnitude bigger at 1 AU than a nuclear bomb pressed against your eye? That's just sick.

davidstarlingm wrote:Can anything shield you from neutrinos?

No. The best part of neutrino radiation is in fact that any form of shielding makes the problem worse. The fraction stopped by your shield is negligible (unless your shield is like a billion miles of solid lead), so you still have to deal with all the neutrinos, but now you also have to deal with the radiation the shield is giving off due to neutrinos hitting it.


Maybe you could put a strong gravitational anomaly in front of yourself to bend space and make the neutrinos go around you? Seems to me like something you could do if you had alcubierre drive-type technology.


A general products hull or a stasis field can block them, or a significant depth of scrith will block a middling percentage. Of course, all of those are fictional...

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Re: What-If 0073: "Lethal Neutrinos"

Postby bigchiefbc » Wed Nov 27, 2013 1:15 am UTC

Wow, my first real GOOMHR moment!!

I actually remember thinking about this particular problem about a decade ago and trying to work the physics out myself. But I hadn't seen that Karam paper yet, so I had trouble finding what percentage of neutrinos would actually hit you at specific distances. I knew roughly how many neutrinos we can detect coming from the sun from books, and also how many neutrinos should be released in a supernova, at least in theory, and tried to work it out from there. I remember coming out with an answer that was not particularly close to Randall's but it was within an order of magnitude so. I feel proud I was that close.

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Re: What-If 0073: "Lethal Neutrinos"

Postby 5th Earth » Wed Nov 27, 2013 4:08 am UTC

I find the unit "hydrogen bomb" frustratingly vague. Although I suppose with the scales we're dealing with, choosing from the largest or smallest of the range of available thermonuclear ordinance doesn't much matter.

A black hole would make a good shield for neutrinos. A neutron star might work too.
It seemed like a good idea at the time.

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Re: What-If 0073: "Lethal Neutrinos"

Postby Himself » Wed Nov 27, 2013 4:32 am UTC

Pfhorrest wrote:Now I'm wondering about the physics of that feather knocking you over. It seems like it would be similar to the can-you-boil-tea-by-stirring question. Sure, you could take sufficient energy to boil the tea and impart it via a stirring motion... but as a consequence of other factors you're not going to have a cup of tea left to boil after doing that for long. Likewise, say you somehow accelerated a feather to have a momentum sufficient to knock a person over, and let's do this in a vacuum so we don't have a shockwave of air complicating the matter. The feather hits the person and... what exactly is their collision like? Certainly it won't be perfectly elastic and just impart all the feather's momentum uniformly to the person's body, knocking them cleanly back. Part of the feather and part of the person will likely crumple, shatter, or otherwise take that energy and do something other than send the person flying back. Would the feather punch through the person like a (certain kind of) bullet? Would it shatter on impact and blow a crater at the point of contact?

I am not a physics person, but I will still take a crack at it. Let's say we have a 1 gram feather and a 70 kilogram person, and say the momentum needed to knock the person over is equivalent to accelerating him to 0.5 m/sec (just a guess there). So that gives us a feather moving at 35,000 m/sec, which is comparable to the speed of an impacting bolide. So, if this were attempted in a vacuum, my guess would be that the results would be rather explosive.
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Re: What-If 0073: "Lethal Neutrinos"

Postby ataral@s » Wed Nov 27, 2013 9:09 am UTC

When I was an undergraduate physicist, I overheard in the hallway someone exclaiming, "Dinosaurs versus cosmic rays? I know who would win!" So I googled, fell down a black hole, and found out that, interestingly, there was an academic argument about dinosaurs vs. neutrinos in the late 90s among physicists who were sticking their noses where they don't belong.

It kicked off with "Biological Effects of Stellar Collapse Neutrinos" (astro-ph/9505028) (aka, how the neutrinos killed the dinosaurs) which spawned both criticism (astro-ph/9612003v1) and "Volcanogenic Dark Matter and Mass Extinctions" (astro-ph/9612214v1) (aka, how the dark matter killed the dinosaurs) which, in turn, spawned another response (astro-ph/9702026v1) from the original author.

My apologies for not providing direct links to the papers—the spam filter denies me if I do. All the papers can be found on arxiv.org with the given reference numbers.

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Re: What-If 0073: "Lethal Neutrinos"

Postby Chappers » Wed Nov 27, 2013 10:41 am UTC

Hello everyone! I've registered just to post this because it's making my brain hurt a little. (bear with me, I'm an engineer, not a mathemagician dammit!)

However... and I think I kind of know the answer... but I want to run it by you guys anyway:

If the energy at the distance between the sun and earth released from a supernova is 10^9 hydrogen bombs, why isn't a supernova at 15,000 light years (10^9 AU) equivalent to the energy of 1 hydrogen bomb?

Something to do with energy not being related to distance?

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Re: What-If 0073: "Lethal Neutrinos"

Postby AussieJono » Wed Nov 27, 2013 11:42 am UTC

jgh wrote:
"Supernovii" is discouraged.

"Supernovii" are discouraged, surely.

ducks and hides


No, "Supernovii" is discouraged is correct. Although the term refers (incorrectly) to multiple objects, when Randle writes that it should be discouraged he is referring to the term itself as an abstract and therefore in the singular.
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Re: What-If 0073: "Lethal Neutrinos"

Postby Xenomortis » Wed Nov 27, 2013 11:52 am UTC

But I would also like people not to encourage stars to explode.
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Re: What-If 0073: "Lethal Neutrinos"

Postby rmsgrey » Wed Nov 27, 2013 1:03 pm UTC

Chappers wrote:Hello everyone! I've registered just to post this because it's making my brain hurt a little. (bear with me, I'm an engineer, not a mathemagician dammit!)

However... and I think I kind of know the answer... but I want to run it by you guys anyway:

If the energy at the distance between the sun and earth released from a supernova is 10^9 hydrogen bombs, why isn't a supernova at 15,000 light years (10^9 AU) equivalent to the energy of 1 hydrogen bomb?

Something to do with energy not being related to distance?


At any given distance, the energy is spread over the surface of a sphere (there may also be some time smearing, depending on the propagation mechanisms, but if you wait long enough, all the energy from the original event will cross the boundary sphere of a given radius - well, aside from that region's share of the portion of the cosmic thermal background energy that's due to that event).

Since the surface area of a sphere increases as the square of the radius, the energy follows an inverse square law - you'd get 1 hydrogen bomb at about 10^(4.5) AU or half a light-year.

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Re: What-If 0073: "Lethal Neutrinos"

Postby Diadem » Wed Nov 27, 2013 1:56 pm UTC

rmsgrey wrote:At any given distance, the energy is spread over the surface of a sphere (there may also be some time smearing, depending on the propagation mechanisms, but if you wait long enough, all the energy from the original event will cross the boundary sphere of a given radius - well, aside from that region's share of the portion of the cosmic thermal background energy that's due to that event).

Since the surface area of a sphere increases as the square of the radius, the energy follows an inverse square law - you'd get 1 hydrogen bomb at about 10^(4.5) AU or half a light-year.

Of course that 's a hydrogen bomb pressed to your eyeball. Assuming the average hydrogen bomb has a radius of 1 meter, then Alpha Centauri going supernova would be roughly equivalent with a hydrogen bomb exploding in your neighbor's house.
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Re: What-If 0073: "Lethal Neutrinos"

Postby davidstarlingm » Wed Nov 27, 2013 2:35 pm UTC

And keep in mind that energy may or may not be linearly proportional to brightness, which is the quantity Randall was using. There's a lot of energy in both supernovae and thermonuclear explosions that isn't radiated as visible light.

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Re: What-If 0073: "Lethal Neutrinos"

Postby PolakoVoador » Wed Nov 27, 2013 2:56 pm UTC

Xenomortis wrote:But I would also like people not to encourage stars to explode.


Why not? As long as it is not our star...

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Re: What-If 0073: "Lethal Neutrinos"

Postby Red Hal » Wed Nov 27, 2013 4:02 pm UTC

Randall did say "energy delivered to your retina"
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Re: What-If 0073: "Lethal Neutrinos"

Postby MikkoKolkkala » Wed Nov 27, 2013 4:32 pm UTC

So, this sentence from David Deutsch's book is an exaggeration: "[supernova's] neutrino radiation alone would kill a human at a range of billions of kilometres, even if that entire distance were filled with lead shielding." ?

Deutch, D. 2012: The beginning of infinity: Explanations that transform the world. Penguin Books. P. 2.


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