What are the green blips in the war footage?


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rebbryan
March 27, 2003, 01:30 PM
i've just been seein that on the recent war footage of little green blobs being shot that look like the photon torpedos from star trek. what are they? they move too slow to be guns, and too many of em to be tank shots

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QuarterBoreGunner
March 27, 2003, 01:36 PM
Tracers probably; I have no idea why but alway look like they're just floating up like balloons...

Mike Irwin
March 27, 2003, 01:52 PM
One thing has always amazed me about tracers...

They appear to be moving in complete slow motion.

I think it must be an optical illusion.

Mark D
March 27, 2003, 01:57 PM
Much depends on the caliber. A 7.62 tracer will "drift" up into the air. While a 37mm will streak by that 7.62 like it's standing still.

Mike Irwin
March 27, 2003, 02:50 PM
I wonder why that is, because initial muzzle velocity is roughly the same...

Kharn
March 27, 2003, 03:16 PM
Its probably an illusion due to the frame rate of the camera and the cyclic rate of the machine gun being at odds with each other. Instead of seeing the trace from a single bullet, you're probably seeing several different bullets at different times, thus creating the illusion of a slow moving tracer.

Kharn

Mike Irwin
March 27, 2003, 03:18 PM
Kharn,

Well, that would be one explanation, but when I've seen tracers in person, they still look as if they're moving in slow motion...

I've not seen cannon tracers, though, so it could still be a cyclic rate optical illusion.

J Miller
March 27, 2003, 04:16 PM
I don't know about optical illusions. I have fired 7.62 tracers out of my Ishapore bolt rifle and they still look like they are floating up and away.

Personally I think it's an optional delusion. :D

blades67
March 27, 2003, 04:26 PM
It appears that way in part because of the way our eyes collect light and our brains perceive it.

Zak Smith
March 27, 2003, 04:37 PM
I think blades67 is on to something.

In addition, the angular velocity is probably low relative to the observer, like how the ground looks like it is moving slowly under you when you're at 30kft in a 747. This effect would be amplified if the rounds were "outgoing".

As for the 37mm vs. 7.62 apparent speed, my guess is that the 37mm will have a much higher BC and thus retain velocity longer.

-z

telewinz
March 27, 2003, 04:44 PM
They are anti-aircraft peas, the all natural air defense.:D

Ebbtide
March 27, 2003, 04:45 PM
They are classified photon guns.

Actually, if you are talking about the chain gun video, count how long it takes to get to target that appears to be about a mile down range, if not more. I can barely get out the "one" in "one-onethousand".

Given that, I guess the round travels at roughly 4 miles a second, or, roughly, 24,000 feet per second. It is just a long way.

Mal H
March 27, 2003, 05:42 PM
I don't think they're going quite that fast ehenz. More like 1/10th that. They would vaporize within 100 yards if going 4 mi/sec. I believe Zak is closest to the truth on that phenomenon. If you are the shooter, you see a point of light going away from you which doesn't appear to grow a lot smaller as it gets farther away and it doesn't move fast vertically. Your brain would interpret that as a slow moving object. If you see tracers fired in the distance, they are covering a lot of ground fast, but the distance in terms of an arc isn't very large, so again you see that as a slow moving object. If you were at midrange within 100 yards the tracers would look like they were zipping along, which they are. Take this to the extreme like viewing a satellite in the sky. It is traveling roughly 5 miles/sec and yet it appears to be lazily moving along in the sky.

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