LADEE Lights the Night!

Astrophotography: share your photos & discuss techniques
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WCGucfa
Posts: 1856
Joined: Mon Apr 17, 2006 1:39 pm

Re: LADEE Lights the Night!

Unread post by WCGucfa »

Oh yeah, I forgot to mention in my last post that I didn't think the rocket could be heard, but am positive
meteors CAN! My wife and I heard more than one report (as in bang) during the 2001 Leonids.

Bill G.
Comets:40, Best Meteor shwr: Leonids '01, Best Aurora:Oct. '03.
Total.Sol.Eclipse,7/10/72 from Nova Scotia.Annular Sol. Eclipse '94,
Trans.of Venus 2004&2012.,ShoeLevy crash into Jupiter '94.
4/25/66 fireball-9 mag.,SN2011fe,N2012aw,DelphN2013.
Bruce D
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Joined: Sat Jun 14, 2003 6:10 am

Re: LADEE Lights the Night!

Unread post by Bruce D »

Well, at sea level it takes sound about 5 seconds to travel 1 mile ( think about the formula for determining the distance to a thunder storm... count the seconds between the flash and boom then divide by 5 ) so even if the meteor were only 5 miles up (very low indeed for a meteor! ) it would take about 25 seconds for the sound to reach an observer directly below the meteor. As it turns out, the speed of sound decreases with altitude [Ulf]http://www.fighter-planes.com/jetmach1.htm[/url], at an altitude of 5 miles sound actually travels about 100 mph slower than at sea level. I did some googling, and what seemed an obscure and maybe far fetched article I read many years ago now seems to be the accepted explanation for hearing meteors- they have measured the electromagnetic energy produces by meteors, a steady burn can produce a hiss or buzz, while a sudden event like a fireball exploding can produce an EM spike and we hear a pop or bang. We don't hear sound waves directly from the meteor, but rather from nearby objects reacting to the EM pulse created by the meteor (the pulse would essentially travel at the speed of light). There's just no way to get sound waves from 60, 000 ft up down to sea level in 2 or 3 seconds and most meteors are very much higher. I would hazard a guess that a meteor that survived to 60, 000 ft will probably make the whole trip to earth because by that height the atmosphere has probably slowed it down enough that it's no longer burning up (else it's so big nothing will slow it down but the dirt - Yikes!) but that would be another thread 8)
You are right Bill, this is more fun than working!
Bruce D
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Paul D
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Re: LADEE Lights the Night!

Unread post by Paul D »

This is what Bob found about hearing meteors.

Meteors obviously release electromagnetic radiation in the visible portion of the spectrum, but the fact that they also release very low frequency (VLF) radio waves, below 30 kilohertz, is less known and less studied Because these VLF radio waves travel at the speed of light (not at the speed of sound), they arrive at the same time observers see a meteor passing overhead. But in order to be heard by hundreds of people, Keay deduced, radio waves need a "transducer," or some physical object that could create a sound.

Under laboratory conditions, Keay was able to do just that: He created rustling sounds in ordinary objects by exposing them to VLF radiation. Aluminum foil, plant foliage such as pine needles, thin wires — even dry, frizzy hair — produced sounds that were easily heard. This phenomenon is known as electrophonics
Paul...

16" f/5 Night Sky Truss (Midnight Mistress)
10" f/5 Home built Dob with Parks mirror.
Pre-Meade PST
Celestron Skymaster Binos 25-125x80
Meade Travelview Binos 10x50

See that 16" in the sleek black dress? She is all mine. :)
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WCGucfa
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Joined: Mon Apr 17, 2006 1:39 pm

Re: LADEE Lights the Night!

Unread post by WCGucfa »

This launch is certainly causing us to learn a lot of stuff!! :shock: :lol: 8)

Bill G.
Comets:40, Best Meteor shwr: Leonids '01, Best Aurora:Oct. '03.
Total.Sol.Eclipse,7/10/72 from Nova Scotia.Annular Sol. Eclipse '94,
Trans.of Venus 2004&2012.,ShoeLevy crash into Jupiter '94.
4/25/66 fireball-9 mag.,SN2011fe,N2012aw,DelphN2013.
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