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There's no conventional or nuclear way to generate enough directed energy to push a decently sized asteroid, on a straight course for the planet and within a re

There's no conventional or nuclear way to generate enough directed energy to push a decently sized asteroid, on a straight course for the planet and within a reasonable distance of it, away. An asteroid with a diameter of 2 km and a density of 1 ton/m^3 weighs ~410^9 kg. Travelling at 0.01c, it has a kinetic energy of ~410^22 J, or ~100 times the current worldwide energy production per year. Of course deflecting it doesn't require you to fully stop it, but it's closing in fast and you need a strong sideways push to accelerate it fast enough to end up with enough speed to miss the planet. If we ever see an reasonably sized asteroid with reasonable speed on a collision course, we're as doomed as if we hadn't seen it.

reitzensteinm 17y ago
"Ever" is a long time!
jheriko 17y ago
Actually there is - like most technology it all scales up, and if it happens you bet we'd all be in factories churning out nukes/rockets if we had to. If you do the numbers, sure it comes out big, but 4 billion kg is not really that much - especially compared to the production capacity of 6 billion people over a couple of days. We could produce the required energy to move it by collectively winding handles let alone manufacturing nukes. Besides that impending death is an excellent motivator.
- zaphar 17y ago
  Yeah but the real problem is spotting it in time. The sky is really big.
  - stcredzero 17y ago
    If the projectiles are relativistic, then warning could only be a few days or even a few hours ahead of time. Even relativistic impactors are unnecessary. Low albedo impactors coming in from angles far off the ecliptic would be exceedingly hard to spot.
- Retric 17y ago
  It's not a question of mass but velocity. .01 * the speed of light = 2,997,924.58 m / s 1kg traveling at 2,997,924.58 m / s = 6,706,166.29 mph. At that speed it has the same kinetic energy as ~10,000,000,000 kg traveling 67mph.

reitzensteinm 17y ago

"Ever" is a long time!

jheriko 17y ago

Actually there is - like most technology it all scales up, and if it happens you bet we'd all be in factories churning out nukes/rockets if we had to. If you do the numbers, sure it comes out big, but 4 billion kg is not really that much - especially compared to the production capacity of 6 billion people over a couple of days. We could produce the required energy to move it by collectively winding handles let alone manufacturing nukes. Besides that impending death is an excellent motivator.

zaphar 17y ago
Yeah but the real problem is spotting it in time. The sky is really big.
- stcredzero 17y ago
  If the projectiles are relativistic, then warning could only be a few days or even a few hours ahead of time. Even relativistic impactors are unnecessary. Low albedo impactors coming in from angles far off the ecliptic would be exceedingly hard to spot.
Retric 17y ago
It's not a question of mass but velocity. .01 * the speed of light = 2,997,924.58 m / s 1kg traveling at 2,997,924.58 m / s = 6,706,166.29 mph. At that speed it has the same kinetic energy as ~10,000,000,000 kg traveling 67mph.