[iLikebeer]

Last year, I read a scifi book where unknown terrorists crashed a spaceship traveling at lightspeed into earth. The collision barely grazed the ocean and passed through, but caused major tsunamis killing millions.

I just got my wisdom teeth removed and I'm on some painkillers and thought of that for some reason. It got me to thinking. What if we get lightspeed travel in the next 500-1000 years. Human nature, religious differences, and regular crazy people will most likely still be ongoing issues. If some crazy person gained possession of one of these spacecraft, how much damage could they do if they hit earth directly. Would you use relativistic mass or invariant mass in the calculations? How big of a spacecraft would you need to have to destroy all life on the planet?

[Kerrigan]

I'm on some painkillers

If some crazy person gained possession of one of these spacecraft, how much damage could they do if they hit earth directly.

I would guess a ****-ton of damage.

[LegendaryPinkOx]

I just woke up, but seems to me that anything that it contacts would vaporize instantly and it would be the equivalent of shooting a very wide laser at the earth. any damage would be caused by stuff rushing in to fill the absence of what used to be there. Which yeah could be pretty damaging depending on the scale of the spaceship.

Hehe nothing makes one feel more like a nerd than having an opinion on sci-fi science

[Laminar]

You'd probably need more pain killers.

[residentEvil]

Originally Posted by LegendaryPinkOx 

I just woke up, but seems to me that anything that it contacts would vaporize instantly and it would be the equivalent of shooting a very wide laser at the earth. any damage would be caused by stuff rushing in to fill the absence of what used to be there. Which yeah could be pretty damaging depending on the scale of the spaceship.

Hehe nothing makes one feel more like a nerd than having an opinion on sci-fi science

science fiction science? do you have a PIN number? a hot water heater?

[nonhuman]

As speed approaches C, mass approaches ∞. A near-infinite mass impacting the Earth at near light speed would be ...devastating, to say the least. Consider that a tiny bullet, traveling at high speed can knock a man off his feet. Now scale that up so that the bullet masses more than the man.

The Earth would most likely be destroyed.

[subego]

Originally Posted by Kerrigan

I would guess a ****-ton of damage.

Imperial ****-ton or metric ****-ton?

[Chuckit]

The plus side is that by the time this is a practical concern, we'll be so many and so widely spread that nobody will miss Earth.

[subego]

It also implies technology (say, workable fusion) that will reduce the prevalence of factors (poverty, lack of education) that allow insane (awesomely so in this case) ideologues to attract followers.

This means we're talking about a near-light speed craft that can be piloted by only a handful of people, which would make it take longer before it was possible, and hence increase the spread even more.


In the meantime, more painkillers. K? Thx.

[subego]

To keep things grimly transhumanist, I think one can posit the ability to "fix" such sociopathic tendencies by that time. Even in the womb if desired.

You think your puny Terran Federation could stop us or something?

[Chuckit]

Originally Posted by subego 

It also implies technology (say, workable fusion) that will reduce the prevalence of factors (poverty, lack of education) that allow insane (awesomely so in this case) ideologues to attract followers.

I don't think workable fusion would prevent despots and crackpots from coming into power. There have always been crazies, and I see no reason to believe there won't continue to be crazies. It would be nice if technology could solve human psychology, but so far it doesn't look that way.

[subego]

Originally Posted by Chuckit 

I don't think workable fusion would prevent despots and crackpots from coming into power. There have always been crazies, and I see no reason to believe there won't continue to be crazies. It would be nice if technology could solve human psychology, but so far it doesn't look that way.

Reduce, not prevent.

Likewise, fusion can be pretty directly assumed from the question. Less direct, but no less probable, are things like truly global internet access and truly global cellular communication.

There's a reason why despots don't like the internet.

Edit: I should also add, blowing up the earth isn't despotic, and as I said, crackpots need followers. Followers need a reason to follow. That reason is usually poverty and/or lack of education. Fusion (and other tech) would help enormously with that.

[subego]

Originally Posted by Chuckit 

It would be nice if technology could solve human psychology, but so far it doesn't look that way.

You didn't have the cojones.

That's why we left Terra.

[Doofy]

Hold on, hold on. Don't you think we'd better make it as far as the moon before we start talking about terrorists crashing DC-10s spaceships into volcanos the earth?

[subego]

[Railroader]

Originally Posted by nonhuman 

As speed approaches C, mass approaches ∞. A near-infinite mass impacting the Earth at near light speed would be ...devastating, to say the least. Consider that a tiny bullet, traveling at high speed can knock a man off his feet. Now scale that up so that the bullet masses more than the man.

The Earth would most likely be destroyed.

Debunked by The Mythbusters.

[subego]

Originally Posted by Railroader 

Debunked by The Mythbusters.

I thought it was Newton.

[Don Pickett]

A object moving at 3 km/sec produces kinetic energy on impact equal to its mass in TNT. In other words, a 1,000 kilo asteroid hitting the side of your spaceship at 3 km/sec would be as if a 1 kiloton warhead hit your ship. Now consider that 3 km/sec is 1/100,000 of the speed of light and you can see how this would scale. In other words, a 1,000 asteroid hitting the earth at .99c would devastate the planet.

There is another issue: an object moving at .99c is pretty much unstoppable. Due to light speed lag, by the time you saw the thing it would be on top of you.

More here.

[waxcrash]

To get a visual representation of what an asteroid hit would do to earth, check this link out. Put in your city and for weapon type select asteroid. If an asteroid would hit my home (Chicago) it would take out all of North America.

http://www.carloslabs.com/node/16

[ghporter]

Originally Posted by subego 

I thought it was Newton.

Newton used numbers; Adam and Jamie used pictures for the numerically challenged...

Of course neither addressed what exactly it is that causes the "jump/lurch/bounce" effect rather than the occasionally seen "drop like a puppet with his strings cut" effect. But that's fodder for a different thread...

[nonhuman]

Originally Posted by Railroader 

Debunked by The Mythbusters.

A .50 cal round certainly has the impact force necessary to knock a man off his feet. It will make a 600 lbs. safe laying on it's side (as in, a very heavy, very stable target) jump on impact.

http://www.youtube.com/watch?v=i9lMViBr6d8

[Don Pickett]

Originally Posted by nonhuman 

A .50 cal round certainly has the impact force necessary to knock a man off his feet. It will make a 600 lbs. safe laying on it's side (as in, a very heavy, very stable target) jump on impact.

http://www.youtube.com/watch?v=i9lMViBr6d8

The MythBusters episode was specifically about hand guns, so think 9 mm.

[subego]

^^

If a .50 cal is a "tiny" bullet, what is a .22LR?

What's a "large" bullet? 20mm? At that point, aren't they generally called shells?



Yes, I realize this is hopelessly pedantic on my part. Likewise, even something like a 105mm tank shell actually is tiny compared to a craft that can reach relativistic velocity.

[nonhuman]

Originally Posted by Don Pickett 

The MythBusters episode was specifically about hand guns, so think 9 mm.

Yes. And my statement was not specifically about hand guns.

[nonhuman]

Originally Posted by subego 

Likewise, a 105mm tank shell actually is tiny compared to a craft that can reach relativistic velocity.

That's what I was getting at. On the scale we're talking about any bullet is tiny.

[subego]

Absolutely.

I think this came across less though than the "bullets knock people over" meme. I know that's not what you were trying to say, but for those following at home I'd like to clarify they can, but this is generally the exception rather than the rule (i.e., sniper rifles designed to penetrate vehicles that will almost break your collarbone when fired, something mounted on a tripod/pintle, or something that what it fires isn't even called a bullet anymore).

If a bullet has the capability to knock a man over, it usually means a man can't fire it unassisted.

[nonhuman]

Originally Posted by subego 

If a bullet has the capability to knock a man over, it usually means a man can't fire it unassisted.

Unless you happen to have a Barrett M82.

[ghporter]

Originally Posted by subego 

If a bullet has the capability to knock a man over, it usually means a man can't fire it unassisted.

Originally Posted by nonhuman 

Unless you happen to have a Barrett M82.

If you can fire the M82 from your shoulder, I want you on my side of ANY argument. The M82 is designed to be fired prone and dug in...for a very good reason. 1/10 oz of bullet traveling at around 2500 feet per second means a huge impact at the target end, but ENORMOUS recoil too...

[subego]

Originally Posted by nonhuman 

Unless you happen to have a Barrett M82.

Well, that's the "will almost break your collarbone when fired" exception.

[nonhuman]

Originally Posted by ghporter 

If you can fire the M82 from your shoulder, I want you on my side of ANY argument. The M82 is designed to be fired prone and dug in...for a very good reason. 1/10 oz of bullet traveling at around 2500 feet per second means a huge impact at the target end, but ENORMOUS recoil too...

I don't know if I'd count firing from the ground as 'assisted' though. One guy, with no equipment besides the gun itself, can fire it.

[subego]

Originally Posted by nonhuman 

I don't know if I'd count firing from the ground as 'assisted' though. One guy, with no equipment besides the gun itself, can fire it.

Would you accept one guy, pre-knocked over?

[Don Pickett]

Originally Posted by subego 

Yes, I realize this is hopelessly pedantic on my part. Likewise, even something like a 105mm tank shell actually is tiny compared to a craft that can reach relativistic velocity.

Sure. But a 105mm HE round weighs about 20 kg. Accelerate that to 3 km/sec, and when it hits your ship it will do the equivalent damage of 20 kg of TNT going off next to your hull. Accelerate that to .5c and it will completely destroy your ship.

[subego]

So our hypothetical relativistic terror vessel was annihilated by the chunk of space debris it accidentally hit on the way in.


Party pooper.

[nonhuman]

Originally Posted by subego 

So our hypothetical relativistic terror vessel was annihilated by the chunk of space debris it accidentally hit on the way in.


Party pooper.

Not to worry, at these speeds the chances of Earth detecting the approaching craft, let alone managing to intercept it, are minimal.

[King Bob On The Cob]

Originally Posted by nonhuman 

A .50 cal round certainly has the impact force necessary to knock a man off his feet. It will make a 600 lbs. safe laying on it's side (as in, a very heavy, very stable target) jump on impact.

http://www.youtube.com/watch?v=i9lMViBr6d8

Humans are made of stuff a lot less strong than the safe, meaning that it will go through you, like it was designed to, and keep going, not expending much energy on your body.

[Laminar]

Originally Posted by Don Pickett 

The MythBusters episode was specifically about hand guns, so think 9 mm.

But they tested shotguns as well.

[subego]

Originally Posted by nonhuman 

Not to worry, at these speeds the chances of Earth detecting the approaching craft, let alone managing to intercept it, are minimal.

I think Don has a good point though. Even light years away from anything visible, there's still a very real possibility of smacking into a brown dwarf. Usually you start slowing down before you're even halfway to the destination.

It works both ways. You won't see the ship coming, but the ship won't be able to see what's between it and that blue fart of a planet of yours until it's too late.

I think a move to plan B (switching off the sun) is in order.



As an aside: unknown terrorists try and blow up the earth? Talk about unclear on the frigging concept. Trust me, this plan here will have "subego" written all over it.

[Dakar V]

Originally Posted by Laminar 

But they tested shotguns as well.

They laced into that pig carcass like it was Alex J. Murphy.

[Don Pickett]

Originally Posted by subego 

I think Don has a good point though. Even light years away from anything visible, there's still a very real possibility of smacking into a brown dwarf. Usually you start slowing down before you're even halfway to the destination.

It works both ways. You won't see the ship coming, but the ship won't be able to see what's between it and that blue fart of a planet of yours until it's too late.

But if you're just shooting stuff at the Earth in order to hit it, you don't care what it hits on the way there. Shoot off a bunch of 1,000 kg rocks at the earth, shotgun style, and so long as one hits the target, you're fine.

Any civilization which develops the technology to accelerate sizable hunks of rock to relativistic speeds has also just developed a near-unstoppable universal WMD.

[subego]

Originally Posted by Don Pickett 

Any civilization which develops the technology to accelerate sizable hunks of rock to relativistic speeds has also just developed a near-unstoppable universal WMD.

Any useful relativistic spacecraft has this ability (hitch-up an asteroid and fling). I think targeting is where things get sticky.

[Don Pickett]

Originally Posted by subego 

Any useful relativistic spacecraft has this ability (hitch-up an asteroid and fling). I think targeting is where things get sticky.

You actually don't even need a spacecraft. All you need is some way to accelerate the rock. Accelerate a constant 1g for for a year and you're almost at the speed of light. Since a rock can take a lot more than 1g, accelerate the rock at 10g for a little over a month. Once it's been aimed you know where it will land.

[subego]

Originally Posted by Don Pickett 

You actually don't even need a spacecraft. All you need is some way to accelerate the rock. Accelerate a constant 1g for for a year and you're almost at the speed of light.

I'm not sure how you could do this without a spacecraft, or without turning the rock into a spacecraft, which means you're using a spacecraft.

A long tube?

[nonhuman]

Originally Posted by subego 

I'm not sure how you could do this without a spacecraft, or without turning the rock into a spacecraft, which means you're using a spacecraft.

A long tube?

Sure, it's a staple of sci-fi asteroid mining: mine useful/valuable ores from asteroids way out in the belt, load them into some sort of container, then use a mass driver to accellerate them towards the inner solar system where they're intercepted and brought to Earth/Mars/(insert location of space ore processing plant here).

They also make great weapons when trained on large, non-moving targets such as planets.

[Edit: and by 'non-moving' I of course mean 'moving in a predictable manner'.]

[subego]

But wouldn't we be talking about a mass driver about 3/4 of a light year long?

[nonhuman]

Originally Posted by subego 

But wouldn't we be talking about a mass driver about 3/4 of a light year long?

I suppose it would depend on the technology being used. We're already positing FTL travel, so why not superconducting mass drivers capable of accelerating their payload to an appreciable fraction of c in a reasonable short distance? The power involved in this is no greater than accelerating a ship to relativistic speeds, and would probably be easier to manage since the whole assembly doesn't need to be mobile.

There's also a question of time scales involved. If patient, it may be possible to wait for a fortuitous alignent of the planets such that you can accelerate your balistic mass to a lower speed but on a trajectory that takes advantage of the gravity wells of the various planets to slingshot your missile at ever increasing speeds.

[nonhuman]

Although I suppose that a slingshot maneuver at relativistic speeds would necessarily involve masses so great that the effect on the planetary body in question might start to become relevant. A body moving at near light speed, and therefore near infinite mass, would presumably have such a massive gravity well that rather than having it's own trajectory perturbed as it passes, say, Jupiter, it might rip Jupiter out of it's orbit.

An interesting question.

[nonhuman]

His orbit? Is Jupiter (the planet) male?

[subego]

Originally Posted by nonhuman 

We're already positing FTL travel

What?

That would be fiction.

[subego]

Originally Posted by nonhuman 

it might rip Jupiter out of it's orbit

That's why I'm proposing plan B. You wouldn't so much switch off the sun as stretch it out like a spiral-cut ham.

The sun is also a much bigger target.