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FYI about Supernovas: https://what-if.xkcd.com/73/ https://what-if.xkcd.com/73/ --- Which of the following would be brighter, in terms of the amount of energ
by adekok 10y ago
FYI about Supernovas:
https://what-if.xkcd.com/73/ https://what-if.xkcd.com/73/
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Which of the following would be brighter, in terms of the amount of energy delivered to your retina:
1) A supernova, seen from as far away as the Sun is from the Earth, or
2) The detonation of a hydrogen bomb pressed against your eyeball?
A: Applying the physicist rule of thumb suggests that the supernova is brighter. And indeed, it is ... by nine orders of magnitude.
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There are some suggestions that a close supernova would emit enough neutrinos to affect life on Earth. I worked on the Sudbury Neutrino Observatory, for my M.Sc. Roughly, about 10^22 neutrinos go through an average building in a day, and maybe one interacts with the building.
- deleted 10y ago[deleted]
- Santosh83 10y agoMaybe I'm mistaken, but wasn't the suggestion that a close enough supernova would pose a threat to life on Earth because of gamma radiation and not neutrinos?
- Guillaume86 10y agoThe "fun" part is that neutrinos barely interact at all with other matter so the idea of something emitting so much of them than they pose a threat to life is impressive in itself, but sure, it would be the least of our worries if a supernova occured close to earth.
- ChuckMcM 10y agoYes, it isn't the neutrinos you have to worry about, its the mass of protons traveling at relativistic speed that nail you.
- Retric 10y agoHiding on the other side of a planet can block most forms of radiation except neutrinos. So, it's not completely irrelevant.
- ridgeguy 10y agoI think our radiation shield wouldn't last long. Back of the envelope, just for fun: supernova type Ia energy release: ~ 1e44 Joules [1] radius of Earth orbit, m: ~ 1.5e11 meters diameter of Earth, m: ~ 1.27e7 meters mass of Earth: ~ 5.9e24 kg average specific heat of Earth (assume it's all granite): 2,000J/kg/°K Grinding through the above says that if the Sun went supernova of the wimpiest type, it would dump 1e44 Joules to its surroundings. I think this happens pretty fast, say less than an hour or so. Assuming isotropic distribution, the Earth would intercept about 4.5e-10 of that, or about 4.5e34 Joules. That's enough to heat the entire mass of the Earth to ~ 3.8e6°K. That would literally vaporize the entire Earth. There goes our radiation shield. Never mind the supersonic shock coming through the planet from the ablation blow-off on the side facing the supernova. Amazing and hard to imagine... [1] https://en.wikipedia.org/wiki/Supernova#Energy_output https://en.wikipedia.org/wiki/Supernova#Energy_output
- Santosh83 10y agoAwesome. But IIRC even our Sun expanding into its red giant phase should be sufficient to vaporise the Earth, at least according to some models, while other models say everything up to Venus will be vaporised while Earth will be left as a charred lump. More interesting is the case of a supernova within ~100 light years.
- Retric 10y agoPlanets are going to act like an ablative heat shield so it's not quite that simple, however yea even if you survive the initial event it's going to cook any fragments that would otherwise make it. Also, supernova don't just toss out radiation, the kinetic energy imparted to the outer layers of hydrogen is ridiculous.
- ChuckMcM 10y agoThere was an interesting article in Scientific American a while ago that the jets from a super massive black hole, from a different galaxy, had the potential to wipe out all life on earth if we passed through the "jet wash". The interesting bit for me was that as the equivalent of a massive solar wind (of exceptional strength) it rips away the atmosphere. That hurts no matter where you are.
- adekok 10y agoBoth. The neutrino flux can be large. Even if the gamma rays don't get you, the neutrinos will. Supernovas convert a substantial part of a solar mass to neutrinos. That's a lot of neutrinos.