3 ms·

Surely after 12M years, the bullet will have rusted to dust in-flight? :)

throwaway_yy2Di 13y ago
No, it would have been perfectly preserved, hanging motionless in a dry vacuum. Archivists would be envious. Speaking of archivists: http://sci.esa.int/rosetta/31242-rosetta-disk-goes-back-to-the-future/ http://sci.esa.int/rosetta/31242-rosetta-disk-goes-back-to-t... http://blog.longnow.org/02009/05/21/what-13500-pages-micro-etched-into-nickel-looks-like/ http://blog.longnow.org/02009/05/21/what-13500-pages-micro-e... (this is the object of yesterday's HN story https://news.ycombinator.com/item?id=7092313 https://news.ycombinator.com/item?id=7092313)
- sliverstorm 13y ago
  Oh I know, just kidding :)
pavel_lishin 13y ago
Not enough oxygen for it to rust. And even if it were, a collection of dust traveling at bullet speeds would still probably kill you. But worry not! A bullet fired from 12 million light years away would probably be ablated into nothing by the interstellar dust.
- btilly 13y ago
  Nope. Stop and think about the fact that starlight can travel that distance. Therefore the accumulated dust along that path is not enough to block light. That little dust won't stop a bullet either.
  - pavel_lishin 13y ago
    But it's not just starlight - it's the light of a whole nova (and the collective light of a whole galaxy.) I can see starlight from the bottom of a pool, but the water in the pool will still stop a bullet. (I am not a scientist, I could be entirely wrong, but it seems like the collective dust of 12 million light years would surely ground down a bullet, while being intermittent enough to let starlight pass through in aggregate.)
    - btilly 13y ago
      Well let's calculate it. According to http://www.universetoday.com/30280/intergalactic-space/ http://www.universetoday.com/30280/intergalactic-space/ there is about 1 hydrogen atom per cubic meter. According to https://www.google.com/search?q=light+year+in+meters&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:en-US:official&client=firefox-a&channel=fflb https://www.google.com/search?q=light+year+in+meters&ie=utf-... there are about 10^16 meters in a light year. So 12 million light years is about 10^23 meters. Avagadro's number is about 6 * 10^23. So a tube a square meter across is a bit under 0.2 moles of hydrogen. According to http://answers.yahoo.com/question/index?qid=20080619205711AAuBH5O http://answers.yahoo.com/question/index?qid=20080619205711AA... at standard air pressure a mole of hydrogen would be about 22 liters, so we're talking about 4 liters of gas at standard pressure. Which would be about 1 square meter across, and 4 millimeters tall. The collective dust of 12 million light years of intergalactic space does not seem likely to grind down a bullet very much. That said, the whole calculation is flawed because first you have to get out of our galaxy, which is much higher density. Though that also wouldn't stop a bullet. But then you have our atmosphere, and that most definitely would destroy a bullet that tried to pass through it! But the moral remains. Space is empty. Really empty. Unimaginably so.
- larubbio 13y ago
  What affect would expansion of the universe have on the bullet? Would it just be a little longer and pointier?
lutorm 13y ago
More likely, it will have reached its apoapsis and fallen back on your planet, unless you have one hell of a gun...

No, it would have been perfectly preserved, hanging motionless in a dry vacuum. Archivists would be envious. Speaking of archivists: http://sci.esa.int/rosetta/31242-rosetta-disk-goes-back-to-the-future/ http://sci.esa.int/rosetta/31242-rosetta-disk-goes-back-to-t... http://blog.longnow.org/02009/05/21/what-13500-pages-micro-etched-into-nickel-looks-like/ http://blog.longnow.org/02009/05/21/what-13500-pages-micro-e... (this is the object of yesterday's HN story https://news.ycombinator.com/item?id=7092313 https://news.ycombinator.com/item?id=7092313)

sliverstorm 13y ago
Oh I know, just kidding :)

pavel_lishin 13y ago

Not enough oxygen for it to rust. And even if it were, a collection of dust traveling at bullet speeds would still probably kill you. But worry not! A bullet fired from 12 million light years away would probably be ablated into nothing by the interstellar dust.

btilly 13y ago
Nope. Stop and think about the fact that starlight can travel that distance. Therefore the accumulated dust along that path is not enough to block light. That little dust won't stop a bullet either.
- pavel_lishin 13y ago
  But it's not just starlight - it's the light of a whole nova (and the collective light of a whole galaxy.) I can see starlight from the bottom of a pool, but the water in the pool will still stop a bullet. (I am not a scientist, I could be entirely wrong, but it seems like the collective dust of 12 million light years would surely ground down a bullet, while being intermittent enough to let starlight pass through in aggregate.)
  - btilly 13y ago
    Well let's calculate it. According to http://www.universetoday.com/30280/intergalactic-space/ http://www.universetoday.com/30280/intergalactic-space/ there is about 1 hydrogen atom per cubic meter. According to https://www.google.com/search?q=light+year+in+meters&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:en-US:official&client=firefox-a&channel=fflb https://www.google.com/search?q=light+year+in+meters&ie=utf-... there are about 10^16 meters in a light year. So 12 million light years is about 10^23 meters. Avagadro's number is about 6 * 10^23. So a tube a square meter across is a bit under 0.2 moles of hydrogen. According to http://answers.yahoo.com/question/index?qid=20080619205711AAuBH5O http://answers.yahoo.com/question/index?qid=20080619205711AA... at standard air pressure a mole of hydrogen would be about 22 liters, so we're talking about 4 liters of gas at standard pressure. Which would be about 1 square meter across, and 4 millimeters tall. The collective dust of 12 million light years of intergalactic space does not seem likely to grind down a bullet very much. That said, the whole calculation is flawed because first you have to get out of our galaxy, which is much higher density. Though that also wouldn't stop a bullet. But then you have our atmosphere, and that most definitely would destroy a bullet that tried to pass through it! But the moral remains. Space is empty. Really empty. Unimaginably so.
larubbio 13y ago
What affect would expansion of the universe have on the bullet? Would it just be a little longer and pointier?

lutorm 13y ago

More likely, it will have reached its apoapsis and fallen back on your planet, unless you have one hell of a gun...