Relativistic Problems

[Neko_Oni]

Okay, I was reading The Algebraist by Iain M. Banks and there's one bit where a warship streaks past another ship at near light-speed (something like 0.8c or higher) and destroys it with a x-ray laser pulse. The paragraph says that the target was destroyed before it could even react, implying that the velocity difference was responsible for the suprise factor.

However any problems which the target might experience would also apply equally to the attacker right? Since both ships can consider themselves to be stationary and the other ship the one approaching at high speed.

Anyone want to help me out? Relativistic stuff gives me a headache.

[Howedar]

Light moves at 3E8m/s in all reference frames.

[Neko_Oni]

Light moves at 3E8m/s in all reference frames.

Yeah I know that much, but I'm saying that attacking a ship or system from a very high speed platform provides very little advantage since relativity applies to both of you, you're just as blind to your target's position as they are to yours.

[Howedar]

As far as I know, yeah.

[Darth Wong]

Light moves at 3E8m/s in all reference frames.

Yeah I know that much, but I'm saying that attacking a ship or system from a very high speed platform provides very little advantage since relativity applies to both of you, you're just as blind to your target's position as they are to yours.

Correct; given equal sensor technology, you would have as much trouble tracking the target as the target does tracking you. People often forget why ground-attack aircraft actually slow down to accurately strike their targets, rather than being designed to zoom by at Mach speed.

[SPOOFE]

but I'm saying that attacking a ship or system from a very high speed platform provides very little advantage since relativity applies to both of you, you're just as blind to your target's position as they are to yours.

My immediate guess would be that the attacking ship had already performed the calculations necessary to know exactly when and where it would need to fire to hit the enemy ship. The target, not anticipating having to deal with relativistic attacks, hadn't the chance to make similar calculations.

Knowing Banks, at least, that would be my guess.

[omegaLancer]

but I'm saying that attacking a ship or system from a very high speed platform provides very little advantage since relativity applies to both of you, you're just as blind to your target's position as they are to yours.

My immediate guess would be that the attacking ship had already performed the calculations necessary to know exactly when and where it would need to fire to hit the enemy ship. The target, not anticipating having to deal with relativistic attacks, hadn't the chance to make similar calculations.

Knowing Banks, at least, that would be my guess.

Problem is that since the X ray laser operate at the speed of light, it would never detect it firing until the beam has already hit.

I can see where such hi relativitic velocities would aid missile attacks, with beam attacks it would not matter much once a targeting solution has been calculated.

[Symmetry]

Problem is that since the X ray laser operate at the speed of light, it would never detect it firing until the beam has already hit.

Thats assuming that there is no way to tell that an X ray laser is going to fire soon. Even a microsecond chargeup time is long enough for a culture mind to react, unless the enemy goes from being too far away to detect this to within fireing range very quickly. Of course, he might very well have messed up, too. David Webber made this same mistake in a first edition of one book, and he generally gets his Newtonian physics right, even if his technobabble is less convincing that Banks's.

[The Nomad]

I haven't done any calc or read the book yet, but wouldn't relativistic blueshift increase the power of the beam ?

[The Nomad]

BTW Symmetry, The Algebraist ain't a Culture book - a Culture fight would involve a few light-years' range, FTL speeds and effectors/Displacers .

[Crown]

Light moves at 3E8m/s in all reference frames.

Yeah I know that much, but I'm saying that attacking a ship or system from a very high speed platform provides very little advantage since relativity applies to both of you, you're just as blind to your target's position as they are to yours.

Correct; given equal sensor technology, you would have as much trouble tracking the target as the target does tracking you. People often forget why ground-attack aircraft actually slow down to accurately strike their targets, rather than being designed to zoom by at Mach speed.

Mike is correct, however that isn't the only reason aircraft don't drop ordanance at Mach speed. There's also the issue of seperation of ordanace and airplane safety. You can't let go of a bomb/missile at any attitude/altitude/speed. I've seen test videos where the ordanance being dropped flys back up into the plane.

Of course this has nothing to do with your question, which is more about sensor ability, but I just though I the other fact should be added aswell.

[GrandMasterTerwynn]

I haven't done any calc or read the book yet, but wouldn't relativistic blueshift increase the power of the beam ?

No, it wouldn't. You don't magically get an increase in power just because you increase the frequency and decrease the wavelength of the photons in your beam. You just get a beam of the same power that's 'bluer.'

[Lord Zentei]

I haven't done any calc or read the book yet, but wouldn't relativistic blueshift increase the power of the beam ?

No, it wouldn't. You don't magically get an increase in power just because you increase the frequency and decrease the wavelength of the photons in your beam. You just get a beam of the same power that's 'bluer.'

Correct me if I'm wrong, but isn't that a contradiction in terms? The energy of a photon is proportional to it's frequency. While energy is a conserved quantity, it is not invariant between refrence frames. The beam can have a higher energy in the target's reference frame than in the ship's reference frame.

[Lancer]

Yeah I know that much, but I'm saying that attacking a ship or system from a very high speed platform provides very little advantage since relativity applies to both of you, you're just as blind to your target's position as they are to yours.

Correct; given equal sensor technology, you would have as much trouble tracking the target as the target does tracking you. People often forget why ground-attack aircraft actually slow down to accurately strike their targets, rather than being designed to zoom by at Mach speed.

Mike is correct, however that isn't the only reason aircraft don't drop ordanance at Mach speed. There's also the issue of seperation of ordanace and airplane safety. You can't let go of a bomb/missile at any attitude/altitude/speed. I've seen test videos where the ordanance being dropped flys back up into the plane.

Hmmn, I know that the F-22's method of deploying missiles from it's internal bays (basically shooting the missile out of the bay at several hunderd g's) was meant to keep the plane as stealthy as possible while deploying missiles, but would it also be useful for deplying ordinance at mach+ speeds?

[omegaLancer]

I haven't done any calc or read the book yet, but wouldn't relativistic blueshift increase the power of the beam ?

No, it wouldn't. You don't magically get an increase in power just because you increase the frequency and decrease the wavelength of the photons in your beam. You just get a beam of the same power that's 'bluer.'

You wrong it does get more energy, the energy come from the kinetic energy of the reference frame it is leaving, so the ship firing the Beam actually slow down, it lose kinetic energy equal to energy gain by the blue shift beam...

[Beowulf]

I haven't done any calc or read the book yet, but wouldn't relativistic blueshift increase the power of the beam ?

No, it wouldn't. You don't magically get an increase in power just because you increase the frequency and decrease the wavelength of the photons in your beam. You just get a beam of the same power that's 'bluer.'

You wrong it does get more energy, the energy come from the kinetic energy of the reference frame it is leaving, so the ship firing the Beam actually slow down, it lose kinetic energy equal to energy gain by the blue shift beam...

Yes, relativistic blue shift would increase the power of the beam. Bluer light has more energy per photon, and the number of photons remains constant. There's a reason why UV light is bad for you in large quantities, while visible light is no problem.