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I'd love to play around with the math, but am extremely ill-equipped to answer my XKCD What If?-Style Question, so I'll just ask it here. If i'd ignore the tim

I'd love to play around with the math, but am extremely ill-equipped to answer my XKCD What If?-Style Question, so I'll just ask it here. If i'd ignore the time necessary to accomplish my goal, could I use such a craft to steer an asteroid to earth? I'm imagining to balance the minuscule gravity a craft like the LightSail 2 would effect on an asteroid with the propelling force of the lightsail over a few centuries to slowly but steadily tug the asteroid on a collision course. When looking at the cost of the LightSail 2 I'd imagine this to be the most cost effective method of putting a deadline on humanity for the enterprising villain on the lookout for a bargain.

WJW 7y ago
That could work if your villain is on a budget, but a time frame of a few centuries is MUCH too optimistic. It would expect diverting even a small asteroid to take several million years, let alone one of the really dangerous ones. Making the sail (much) bigger would help, but then you have additional problems because people would see it coming and could take countermeasures.
dmd 7y ago
In general, the answer to "If I ignore how physics works, can I XXXX" is "yes", because what you've actually asked is "can I do XXXX with magic".
kadoban 7y ago
If your math is good enough, could you just "paint" the surface of a suitable object enough to steer it via differences of light pressure?
- larkeith 7y ago
  Interestingly, this is one of the ways we could deflect an asteroid on a collision course with the Earth, if we detect it early enough.
- inamberclad 7y ago
  Yes, some deep space missions need to take solar radiation pressure into account due to effects like this.
- sandworm101 7y ago
  Not really. The differences in pressure would create spin, not push the craft in a different direction. You would need something else to push against, to "tack" against the solar wind, like how a sailboat's keel pushed against the water. Magnetic fields are an option, but those get less and less as you move away from the sun. There are some complicated options involving mirrors that could move a craft in other directions, but they are radically difficult to manage. You send five mirrors with the craft as a formation, one on each side and one ahead. Then you can bounce the lasers off these mirrors to steer the ship. At the destination, the ahead mirror is used to slow the craft. All these mirrors would essentially be separate craft that would need to be themselves accelerated and managed.
  - hughes 7y ago
    If you use a material on the back of the asteroid that had a higher albedo at more oblique angles, you could have a form of feedback.

WJW 7y ago

That could work if your villain is on a budget, but a time frame of a few centuries is MUCH too optimistic. It would expect diverting even a small asteroid to take several million years, let alone one of the really dangerous ones. Making the sail (much) bigger would help, but then you have additional problems because people would see it coming and could take countermeasures.

dmd 7y ago

In general, the answer to "If I ignore how physics works, can I XXXX" is "yes", because what you've actually asked is "can I do XXXX with magic".

kadoban 7y ago

If your math is good enough, could you just "paint" the surface of a suitable object enough to steer it via differences of light pressure?

larkeith 7y ago
Interestingly, this is one of the ways we could deflect an asteroid on a collision course with the Earth, if we detect it early enough.
inamberclad 7y ago
Yes, some deep space missions need to take solar radiation pressure into account due to effects like this.
sandworm101 7y ago
Not really. The differences in pressure would create spin, not push the craft in a different direction. You would need something else to push against, to "tack" against the solar wind, like how a sailboat's keel pushed against the water. Magnetic fields are an option, but those get less and less as you move away from the sun. There are some complicated options involving mirrors that could move a craft in other directions, but they are radically difficult to manage. You send five mirrors with the craft as a formation, one on each side and one ahead. Then you can bounce the lasers off these mirrors to steer the ship. At the destination, the ahead mirror is used to slow the craft. All these mirrors would essentially be separate craft that would need to be themselves accelerated and managed.
- hughes 7y ago
  If you use a material on the back of the asteroid that had a higher albedo at more oblique angles, you could have a form of feedback.