3 ms·

If I accelerate 1000 1kg masses to .99c 1ly away from your planet you can't detect them, and I've just destroyed your entire species (sterilized the planet) wit

If I accelerate 1000 1kg masses to .99c 1ly away from your planet you can't detect them, and I've just destroyed your entire species (sterilized the planet) with a metric ton of rocks. It doesn't matter how long I take to accelerate them, once they are going fast you are destroyed in 1 year.

deeviant 12y ago
You would need some pretty killer orbital prediction to do this. I would assume you'd start a bit closer.
rwallace 12y ago
With the caveat that at the tech level required to launch such an attack, destruction of one's home planet would constitute something closer to vandalism of a historic site than destruction of one's species. Of course, if you're thinking of a scenario where aliens at that tech level launch such an attack against us 21st-century humans, yes, we'd be toast.
TheLoneWolfling 12y ago
Why are you saying we couldn't detect them? There's enough interstellar medium to make any such impactor detectable. (Rough calculation: 67kw/m^2. And that's not even talking about dust grains (which ends up with much brighter instantaneous flashes))
- letstryagain 12y ago
  By the time you see it, it will be too late to respond.
  - TheLoneWolfling 12y ago
    Why? Sure, there's time dilation effects, but they are largely cancelled out. We have less notice for a given distance, but we also can see it coming from farther away.
    - InclinedPlane 12y ago
      .99c means that you have 1/100th as much time to respond relative to the detection distance. Let's say you spot the impactors an entire light-year away. The light will only reach you less than 4 days before impact. Can you put together an effective response plan in 4 days? If instead you spotted them out in the oort cloud (say, 1000 AU away) you would have less than 2 hours to respond.
      - TheLoneWolfling 12y ago
        Right, but that is compensated by the fact that that same time compression also applies to any energy released by the impactor. It'd be putting out >3.5*10^7 watts / m^2 at 0.99c, from our perspective. And a single sand grain hitting it would release 27GJ. Not to mention... How on earth are you managing to keep something together when its being bombarded by hydrogen / helium at 0.99c?

deeviant 12y ago

You would need some pretty killer orbital prediction to do this. I would assume you'd start a bit closer.

rwallace 12y ago

With the caveat that at the tech level required to launch such an attack, destruction of one's home planet would constitute something closer to vandalism of a historic site than destruction of one's species. Of course, if you're thinking of a scenario where aliens at that tech level launch such an attack against us 21st-century humans, yes, we'd be toast.

TheLoneWolfling 12y ago

Why are you saying we couldn't detect them? There's enough interstellar medium to make any such impactor detectable. (Rough calculation: 67kw/m^2. And that's not even talking about dust grains (which ends up with much brighter instantaneous flashes))

letstryagain 12y ago
By the time you see it, it will be too late to respond.
- TheLoneWolfling 12y ago
  Why? Sure, there's time dilation effects, but they are largely cancelled out. We have less notice for a given distance, but we also can see it coming from farther away.
  - InclinedPlane 12y ago
    .99c means that you have 1/100th as much time to respond relative to the detection distance. Let's say you spot the impactors an entire light-year away. The light will only reach you less than 4 days before impact. Can you put together an effective response plan in 4 days? If instead you spotted them out in the oort cloud (say, 1000 AU away) you would have less than 2 hours to respond.
    - TheLoneWolfling 12y ago
      Right, but that is compensated by the fact that that same time compression also applies to any energy released by the impactor. It'd be putting out >3.5*10^7 watts / m^2 at 0.99c, from our perspective. And a single sand grain hitting it would release 27GJ. Not to mention... How on earth are you managing to keep something together when its being bombarded by hydrogen / helium at 0.99c?