If you were shot by a grain of sand(at lightspeed)

[ed21x]

from a fluid dynamics point of view, it could potentially not cause much damage, as the speed would essentially be too high for the matrix it is penetrating to react. Think of this like moving a blade through penut butter. If you move it really quickly, you'll get a really clean slice, while a smooth motion would move alot more mass with each stroke.

 

[zerocool84]

If it was moving that fast wouldn't the heat from the friction of the atmosphere kill you even before the grain of sand gets near you?

 

[Jeff7]

Also count me into the "You're very very dead" camp.

To those who say that the sand will pass right through and leave only a grain-sized hole:
It's moving incredibly fast. It's going to want the particles of your body which are in its way to move out of the way with similar expedience. Those particles in turn will kindly ask that their neighboring particles do the same. Result: Same as what happens when you fire a tiny projectile, such as a rifle bullet, at high speed into a fleshy target. You get a hole that's much larger than the projectile.

Surely this has been done before, but what the hell...
Momentum is simply mass * velocity.
Let's go with 0.5 milligrams.
And we'll say it's moving damn fast, 299,000,000 m/s, somewhere around 99.67% c. That's still 149.500 m-kg/s
Wikipedia gives 1000m/s as the velocity of a rifle bullet, around what an M-16 could do, also according to Wikipedia.
Working backwards, that'd work out to be the equivalent of a bullet with a mass of 0.1495kg. M-16's bullet mass: less than 5 grams. So instead of being shot with a 5 gram bullet, you're being shot with a 149.5 gram bullet.
Or switch it up - a 5 gram bullet at 29,900 m/s (~98,000fps).
Either way, you're quite dead.

That's just going by momentum though. An analysis of energy transfer would likely be more accurate. In that case, we'd need to figure out if it were elastic, inelastic, or partly inelastic, should the sandgrain just punch right through and leave a gaping hole in its wake.

So let's go with good old e = mc² for the hell of it, and the half-milligram grain of sand.
44,937,758,936.8 joules.
Wikipedia gives 1MT of TNT as 4.184 * 10^9 joules.
So that sand grain would be packing 10.8MT of energy.

Or just fall back to 0.5mv², for a kinetic energy figure of 22,468,879,468.4 joules - 5.2MT.

Let's say 0.001% of that energy is transferred to you. That's still well over 2 megajoules. Result: you pretty much just blow up.

 

[DrPizza]

Reading this thread was rather painful. Particularly:

Originally posted by: Train
plus we dont know the physics of being in proximity of mass traveling the speed of light. Science as we know it today says mass CAN'T travel that fast.

If you think about a hyper sonic bullet, (50 cal) it can travel past you (technically not touching you) yet still rip you in half because of the vaccum it creates.

Originally posted by: hiromizu
I think you guys are thinking way too scientifically to the point where you can't even get realistic answers. In reality, you'll feel a small pinch and the grain will bounce right off. Nothing more, nothing less.

Originally posted by: hiromizuIf at all else i think it'll barely penetrate the skin and you should be able to just flick it off

Originally posted by: hiromizu
Yea but a space shuttle is flying at a few hundred miles per hour in space. In this case you're not moving and there's air n stuff to cause resistance. It's all relative.

Originally posted by: Train
Convential ballistecs = a 50 cal ripping you in half without even touching you. Thats more in line with a small object hitting a human.

Originally posted by: Train
If you think about the bullet example I mentiond above. Obviously sand is a lot less mass, but theats WAAAAYYY offset by the exponential growth in speed.

Force = Speed x Mass, therefore a grain of sand at light speed is 1000000000 X times more force than a hypersonic 50 cal round.

If it flew within a thousand yards of you, you'd be ripped to shreds in under a second.

Originally posted by: darkxshade
To the "you'll be vaporized" camp... what if said sand instead hit Earth from space at the speed of light? How big of a dent/crater are we talking about here?

And, would you cut it out already? Mass CANNOT travel at the speed of light. As soon as you say that it is traveling at the speed of light (hypothetically), you are imparting INFINITE MASS AND ENERGY to the sand. So, for the "it'll only impart a small percentage of its energy" camp: what's a small percentage of INFINITE??

 

[The Boston Dangler]

dr. pizza, what did you expect?

 

[mryellow2]

Originally posted by: PlasmaBomb

Originally posted by: mryellow2
E = (1/2) X .05 g X (299 792 458 m / s)(299 792 458 m / s)

:

2,246,887,946,842,044.1 joules

~ to 570,000 tons of exploding TNT =o

You are just a little bit out there champ

Damn you Newtonian physics, how could you fail me?! Perhaps Herr Einstein can lend a helpful equation...

 

[Jeff7]

Originally posted by: The Boston Dangler
dr. pizza, what did you expect?

I wish I could remember more of high school physics - when we touched on relativistic stuff, we calculated the yields of things like golf balls moving at various percentages of the speed of light. I don't remember it much anymore though; stuff like a golf ball moving at 0.75c would wipe out NYC, things like that. This guy made physics fun.

"Assume Kathy here has a mass of 53kg, and I push her off of a 100 meter cliff at 5m/s into a lake below. How far away from the cliff should the divers start looking for fattened fish?"

 

[zerocool84]

Originally posted by: DrPizza
Reading this thread was rather painful. Particularly:

Originally posted by: Train
plus we dont know the physics of being in proximity of mass traveling the speed of light. Science as we know it today says mass CAN'T travel that fast.

If you think about a hyper sonic bullet, (50 cal) it can travel past you (technically not touching you) yet still rip you in half because of the vaccum it creates.

Originally posted by: hiromizu
I think you guys are thinking way too scientifically to the point where you can't even get realistic answers. In reality, you'll feel a small pinch and the grain will bounce right off. Nothing more, nothing less.

Originally posted by: hiromizuIf at all else i think it'll barely penetrate the skin and you should be able to just flick it off

Originally posted by: hiromizu
Yea but a space shuttle is flying at a few hundred miles per hour in space. In this case you're not moving and there's air n stuff to cause resistance. It's all relative.

Originally posted by: Train
Convential ballistecs = a 50 cal ripping you in half without even touching you. Thats more in line with a small object hitting a human.

Originally posted by: Train
If you think about the bullet example I mentiond above. Obviously sand is a lot less mass, but theats WAAAAYYY offset by the exponential growth in speed.

Force = Speed x Mass, therefore a grain of sand at light speed is 1000000000 X times more force than a hypersonic 50 cal round.

If it flew within a thousand yards of you, you'd be ripped to shreds in under a second.

Originally posted by: darkxshade
To the "you'll be vaporized" camp... what if said sand instead hit Earth from space at the speed of light? How big of a dent/crater are we talking about here?

And, would you cut it out already? Mass CANNOT travel at the speed of light. As soon as you say that it is traveling at the speed of light (hypothetically), you are imparting INFINITE MASS AND ENERGY to the sand. So, for the "it'll only impart a small percentage of its energy" camp: what's a small percentage of INFINITE??

Did you not read the part that it was hypothetical???

 

[miketheidiot]

might do some damage if it hit bone, but survivable

 

[RESmonkey]

Originally posted by: Jeff7
Also count me into the "You're very very dead" camp.

To those who say that the sand will pass right through and leave only a grain-sized hole:
It's moving incredibly fast. It's going to want the particles of your body which are in its way to move out of the way with similar expedience. Those particles in turn will kindly ask that their neighboring particles do the same. Result: Same as what happens when you fire a tiny projectile, such as a rifle bullet, at high speed into a fleshy target. You get a hole that's much larger than the projectile.

Surely this has been done before, but what the hell...
Momentum is simply mass * velocity.
Let's go with 0.5 milligrams.
And we'll say it's moving damn fast, 299,000,000 m/s, somewhere around 99.67% c. That's still 149.500 m-kg/s
Wikipedia gives 1000m/s as the velocity of a rifle bullet, around what an M-16 could do, also according to Wikipedia.
Working backwards, that'd work out to be the equivalent of a bullet with a mass of 0.1495kg. M-16's bullet mass: less than 5 grams. So instead of being shot with a 5 gram bullet, you're being shot with a 149.5 gram bullet.
Or switch it up - a 5 gram bullet at 29,900 m/s (~98,000fps).
Either way, you're quite dead.

That's just going by momentum though. An analysis of energy transfer would likely be more accurate. In that case, we'd need to figure out if it were elastic, inelastic, or partly inelastic, should the sandgrain just punch right through and leave a gaping hole in its wake.

So let's go with good old e = mc² for the hell of it, and the half-milligram grain of sand.
44,937,758,936.8 joules.
Wikipedia gives 1MT of TNT as 4.184 * 10^9 joules.
So that sand grain would be packing 10.8MT of energy.

Or just fall back to 0.5mv², for a kinetic energy figure of 22,468,879,468.4 joules - 5.2MT.

Let's say 0.001% of that energy is transferred to you. That's still well over 2 megajoules. Result: you pretty much just blow up.

I think we have a winner? It seems sound.

edit = Thread has potential to become epic.

 

[mjrpes3]

Originally posted by: zerocool84

Did you not read the part that it was hypothetical???

You can't make hypothetical what is illogical. Positing an object moving at the speed of light is like positing a triangle with two right angles. It's just not logically possible and the triangle ends up not being a triangle anymore.

 

[Fayd]

does the grain of sand slow down as it passes through the body?

 

[RESmonkey]

Originally posted by: Fayd
does the grain of sand slow down as it passes through the body?

Should, at least a little.

 

[sandorski]

Yes, No, No, No

You would not even realize it happened.

 

[Fayd]

Originally posted by: Train

Originally posted by: Arkaign

Originally posted by: JTsyo

Originally posted by: mugs
Hmmmm... well, we take out tanks by hitting them with oversized lawn darts at about 3000 mph. I figure a grain of sand moving at the speed of light would have quite a lot of kinetic energy.

well that only works because the tanks have multiple inches of armor. If you were to fire the same round through a regular car it would cause almost no damage other than putting 2 holes in it. Spalling of the armor is what gets the crew.

EDIT: I mean through the car door or roof, not through the engine block or some heavy area.

The army was running into the same problem using armor-piercing rounds on unarmored targets. The shots would pass right through the targets and they would still be able to fight. Of course those guys were probably doped up.
Based on these examples, I think the grain would just pass through as long as it didn't hit anything hard and imparted some of its energy. As long as it was occurring in vacuum, I don't think there's enough time for any secondary thermal effects either.

I'm not a physicist but my understanding of the subject is that the object nearing lightspeed doesn't actually increase in mass but just acts like it does. For mass to increase either volume or density would have to increase both would take more matter to increase. Not sure what that would mean at the atomic level though.

This is essentially correct.

Either by impact or hydrostatic shock, at the speeds we are talking about, there's simply no way the density of a human target would be enough to transfer a meaningful amount of energy, and thus, damage would be almost insignificant.

Fire the ~light speed sand grain at a 10-foot-diameter ball of lead, and you'd see a tremendously different reaction.

Nope.

At that speed, water = led.

Ever see high speed boat races? Water is essentially concrete when those things crash. A human body for the sake of this experiment is a bag of water.

The molecules of your body will be literally exploding under the impact, creating a massive energy wave that rips you to shreads.

no, no it doesnt.

conventional wisdom with regard to impacts does not apply when you introduce particles travelling at a significant fraction of the speed of light.

 

[ManBearPig]

http://en.wikipedia.org/wiki/Anatoli_Bugorski

 

[tfcmasta97]

Are you guys fucking morons? bounce off of your skin?

The hadron collider is smashing what, 2 protons together in a vacuum? [not nearly the speed of light] and the force of those 2 are to be equal to some ship traveling on the ocean [weird analogy but yeah that's what was said]

Would you die? depends on where you get hit id guess

 

[zerocool84]

Originally posted by: tfcmasta97
Are you guys fucking morons? bounce off of your skin?

The hadron collider is smashing what, 2 protons together in a vacuum? [not nearly the speed of light] and the force of those 2 are to be equal to some ship traveling on the ocean [weird analogy but yeah that's what was said]

Would you die? depends on where you get hit id guess

:laugh:

 

[Nerva]

Originally posted by: Train
If you think about the bullet example I mentiond above. Obviously sand is a lot less mass, but theats WAAAAYYY offset by the exponential growth in speed.

Force = Speed x Mass, therefore a grain of sand at light speed is 1000000000 X times more force than a hypersonic 50 cal round.

If it flew within a thousand yards of you, you'd be ripped to shreds in under a second.

actually its acceleration x mass.

 

[Krazy4Real]

Originally posted by: sandorski
Yes, No, No, No

You would not even realize it happened.

You wouldn't realize it happened, because YOU'D BE DEAD!

 

[YOyoYOhowsDAjello]

Originally posted by: Kazaam
http://en.wikipedia.org/wiki/Anatoli_Bugorski

"Reportedly, he saw a flash "brighter than a thousand suns"

Sounds pretty bright

I wonder how many protons hit him to do that damage.

So protons were able to burn him, cause nerve damage, destroy his hearing in one ear, and cause seizures for the rest of his life?

A grain of sand is what... about 5x10^21 protons worth of mass?

If we assume it's cubical, that means that the cross-section going through your body is about 17 million times as large as a single proton?
(just taking the cube root of above)
That assumes that the nuclei are all tightly packed next to each other though...
http://www.utas.edu.au/science...ing/images/network.gif
There's whole atoms to deal with now and then the structure between the atoms making up the silicon dioxide structure.

 

[JTsyo]

Ok let's filter this down one level. I think the question is how much energy will be transferred from the grain on sand to the person. We can all agree that you can put a hole a lot bigger than a grain of sand through a person and have them live.

We don't have much of an idea of how the energy transfer occurs at those speeds. If any meaningful part of the energy is transferred, the person is dead. If the matter that the grain contacts is thrown out the exit hole instead of being pushed out radially, I don't see much damage occurring.

Those that keep talking about increasing mass please look into relativistic mass.

 

[Eli]

No. No matter where it went through your body, the number of cells a single grain of sand would kill would be pretty insignificant.

It wouldn't take very many to prove lethal though.

Although, a grain of sand moving at the speed of light would probably make a pretty nasty exit wound. But as far as just passing through you, I don't think it would be lethal.

 

[Jeff7]

Originally posted by: zerocool84

Originally posted by: tfcmasta97
Are you guys fucking morons? bounce off of your skin?

The hadron collider is smashing what, 2 protons together in a vacuum? [not nearly the speed of light] and the force of those 2 are to be equal to some ship traveling on the ocean [weird analogy but yeah that's what was said]

Would you die? depends on where you get hit id guess

:laugh:

:laugh: indeed.

The LHC fires bundles of lots of protons. Millions, I believe, but that's just going on memory. Then they just hope that a few of them collide now and then. So there can be millions of protons in there, but very few collisions at once - but that's only because you're firing bullets at each other - bullets much smaller than individual atoms.

That Anatoli Bugorski guy effectively endured exposure to a rapid-fire railgun, with the bullets passing right through him, obviously imparting considerable energy with each impact.

 

[alphatarget1]

ottawa sand retains at 0.595mm (diameter larger than 0.595mm), but that's not really average. Some beaches have finer sand then others.