7 ms·

Obligatory xkcd reference: 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 e

Obligatory xkcd reference: 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 energy delivered to your retina: > * A supernova, seen from as far away as the Sun is from the Earth, or > * The detonation of a hydrogen bomb pressed against your eyeball? > > ... the supernova is brighter ... by nine orders of magnitude.

cduzz 2y ago
Any time you're killed by neutrino radiation poisoning you're likely done in by a bunch of other things at the same time...
- jajko 2y ago
  to the point that probably all atoms once within your body are spread rather evenly far from each other, and not coming back
  - kijin 2y ago
    Oh they'll come back together, sooner or later, because of gravity. They'll form a gas cloud at first, which condenses into a new star and its planetary system. We're all made from star dust, and will become star dust again.
    - dvaun 2y ago
      Time to return to the Brahman.
adrianN 2y ago
Lethal doses of neutrinos are a plot point in Diaspora by Greg Egan.
- luyu_wu 2y ago
  Also in Supernova Era if I remember correctly!
  - QuercusMax 2y ago
    Cixin Liu sure likes writing books about the end of humanity....
- pfdietz 2y ago
  And in Charles Stross's Iron Sunrise.
perihelions 2y ago
- "by nine orders of magnitude." They're actually much closer to equal, if you account for the duration of the supernova light curve. It's a somewhat relevant difference. A supernova 4 light years away, with all the energy released instantaneously like a bomb, should ignite and vaporize everything on one-half of the planet. That's a wrong calculation. The peak rate— the peak luminosity of a type Ia supernova, for example (10^43 erg/s or 10^36 W—a famous standard candle) would be no more than 50 W/m^2, from the distance of Alpha Centauri. That's about a 5% addition to the solar irradiance, sustained over a few weeks—probably just a moderate change in weather patterns.
- colechristensen 2y ago
  >A supernova, seen from as far away as the Sun is from the Earth GP and XKCD are talking about a supernova from the Sun, you're talking Alpha Centauri.
  - perihelions 2y ago
    Right; I elided from one to the other to give a calculation of interest to the thread topic. (I had thought I had written it sufficiently clearly? What should I change?) The "sol" case is still at the hydrogen-bomb level—but not 9 orders of magnitude beyond it.
    - jjk166 2y ago
      Why wouldn't you just give the numbers for the supernova at 1 au?
      - perihelions 2y ago
        Because there's few reference points with which to interpret numbers on the scale of 10^12 Watts/meter^2, and it doesn't fundamentally change the XKCD outcome anyway (from the human perspective). I thought shifting it to nearby stars made it topical to this thread, where multiple comments are asking about the impact of galactic supernovae. (That's the less important part of my comment, and I'm not sure why people latched onto it! The important part is that supernovae are >7 orders of magnitude slower than hydrogen bomb explosions).

cduzz 2y ago

Any time you're killed by neutrino radiation poisoning you're likely done in by a bunch of other things at the same time...

jajko 2y ago
to the point that probably all atoms once within your body are spread rather evenly far from each other, and not coming back
- kijin 2y ago
  Oh they'll come back together, sooner or later, because of gravity. They'll form a gas cloud at first, which condenses into a new star and its planetary system. We're all made from star dust, and will become star dust again.
  - dvaun 2y ago
    Time to return to the Brahman.

adrianN 2y ago

Lethal doses of neutrinos are a plot point in Diaspora by Greg Egan.

luyu_wu 2y ago
Also in Supernova Era if I remember correctly!
- QuercusMax 2y ago
  Cixin Liu sure likes writing books about the end of humanity....
pfdietz 2y ago
And in Charles Stross's Iron Sunrise.

perihelions 2y ago

- "by nine orders of magnitude." They're actually much closer to equal, if you account for the duration of the supernova light curve. It's a somewhat relevant difference. A supernova 4 light years away, with all the energy released instantaneously like a bomb, should ignite and vaporize everything on one-half of the planet. That's a wrong calculation. The peak rate— the peak luminosity of a type Ia supernova, for example (10^43 erg/s or 10^36 W—a famous standard candle) would be no more than 50 W/m^2, from the distance of Alpha Centauri. That's about a 5% addition to the solar irradiance, sustained over a few weeks—probably just a moderate change in weather patterns.

colechristensen 2y ago
>A supernova, seen from as far away as the Sun is from the Earth GP and XKCD are talking about a supernova from the Sun, you're talking Alpha Centauri.
- perihelions 2y ago
  Right; I elided from one to the other to give a calculation of interest to the thread topic. (I had thought I had written it sufficiently clearly? What should I change?) The "sol" case is still at the hydrogen-bomb level—but not 9 orders of magnitude beyond it.
  - jjk166 2y ago
    Why wouldn't you just give the numbers for the supernova at 1 au?
    - perihelions 2y ago
      Because there's few reference points with which to interpret numbers on the scale of 10^12 Watts/meter^2, and it doesn't fundamentally change the XKCD outcome anyway (from the human perspective). I thought shifting it to nearby stars made it topical to this thread, where multiple comments are asking about the impact of galactic supernovae. (That's the less important part of my comment, and I'm not sure why people latched onto it! The important part is that supernovae are >7 orders of magnitude slower than hydrogen bomb explosions).