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visits member for 2 years, 1 month
seen Apr 2 at 18:16

Sep
29
answered Supermarket refrigerator - why is it noticebable colder in this shop area?
Sep
29
answered Optical Drive Physics
Sep
27
comment Underground explosions due to plate tectonics and natural gas pockets
It's likely that parts undergoing subduction i.e. active regions at the fringes of the tectonic plates don't have enough time to build up substantial reserves of oil or gas. It's the stable areas far from plate boundaries that manage to build up reserves over time.
Sep
26
comment How does nuclear war look like from space?
@Martin: Brilliant :-D
Sep
26
awarded  Teacher
Sep
26
revised How does nuclear war look like from space?
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Sep
26
accepted Effect of surface treatment on fair dice
Sep
26
accepted What do bullet trails really look like?
Sep
26
asked How does nuclear war look like from space?
Sep
26
revised Store up cheap electricity to use later?
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Sep
26
answered Store up cheap electricity to use later?
Sep
24
awarded  Scholar
Sep
24
accepted How many grams of explosive are equivalent to the energy in a battery?
Sep
19
asked How many grams of explosive are equivalent to the energy in a battery?
May
3
answered Effect of surface treatment on fair dice
Apr
14
comment What do bullet trails really look like?
Thanks, dmckee. It's interesting that your images (presumably) show subsonic bullets whereas tmac's are supersonic. I wonder what differences that makes.
Apr
14
comment What do bullet trails really look like?
Thanks for clarifying, tmac. That's what I expected. I wonder if you could comment on dmckee's answer below. In his images, I presume air rifle bullets are subsonic. Should any distortion be visible for bullets travelling below the speed of sound?
Apr
12
comment What do bullet trails really look like?
Thanks, tmac. Based on your images and assuming supersonic bullets, am I correct to conclude that the main effects are (1) a small cloud just behind the bullet and (2) a blunt refracting cone shell just ahead of it? From equation BoatSpeed = WaveSpeed x tan(PI/2-Angle) at physicsforums.com/showthread.php?t=328445, is it right that the cone's half-angle is PI/2 - atan(Mach number) i.e. 39 degrees for 1380 ft/s bullets from Desert Eagles that Agents use? It's unclear from the shadowgraph how far the cone extends or how visible it is to the naked eye. Any idea? What about subsonic bullets?
Apr
12
awarded  Supporter
Apr
12
comment What do bullet trails really look like?
Could you please explain "a non-trivial stretch of space before the bullet's point of impact?" Perhaps my question was unclear: I wish to know what a bullet trail looks like as it is flying through air, not after it has hit a solid or liquid object. In your examples, most of the particles are debris from the target.