The Perseid Meteor Shower

[Haggis]

This weekend is the annual Perseid Meteor Shower (http://www.jupiterscientific.org/sciinfo/perseid.html) with the peak on the morning of August 13th.

[KillJoy]

Thanks for the heads up! We're gonna try and check this out.

KillJoy

[Dr Caleb]

It's worth it. The really cool ones you hear 'sizzle' as you see them.

Being several tens of miles up and hundreds of miles downrange, the fact that seeing and hearing them ocurrs at the same time is left as an exercise for the student.

[Bluerauder]

It's worth it. The really cool ones you hear 'sizzle' as you see them.

Being several tens of miles up and hundreds of miles downrange, the fact that seeing and hearing them ocurrs at the same time is left as an exercise for the student.
I have seen them --- never heard them. But I question the assertion in your student exercise. Sound must always lag behind considerably due to the differential in speeds of sound (in air) vs. light. If there is a correlation of sight and sound, it is due to the apparent alignment with a meteor that passed by several minutes ago. Because of the density (and thus a certain regularity) of meteors in Persieds, it may only "seem" that you are hearing a particular meteor.

Below an altitude of 70 km (42 miles) sound travels between 967 - 1115 fps. That's roughly about 1 mile every 5 seconds. If the meteor is 100 miles away, the sound you hear happened about 8.3 minutes ago since the lag for light across the same distance is instantaneous for all intents (i.e. about .0000537 seconds).

So, I think that "sizzle" is coming from somewhere else. :D

[DefyantExWife]

I have seen them --- never heard them. But I question the assertion in your student exercise. Sound must always lag behind considerably due to the differential in speeds of sound (in air) vs. light. If there is a correlation of sight and sound, it is due to the apparent alignment with a meteor that passed by several minutes ago. Because of the density (and thus a certain regularity) of meteors in Persieds, it may only "seem" that you are hearing a particular meteor.

Below an altitude of 70 km (42 miles) sound travels between 967 - 1115 fps. That's roughly about 1 mile every 5 seconds. If the meteor is 100 miles away, the sound you hear happened about 8.3 minutes ago since the lag for light across the same distance is instantaneous for all intents (i.e. about .0000537 seconds).

So, I think that "sizzle" is coming from somewhere else. :D


morning gas ? :baaa:

[Dr Caleb]

Sound must always lag behind considerably due to the differential in speeds of sound (in air) vs. light. If there is a correlation of sight and sound, it is due to the apparent alignment with a meteor that passed by several minutes ago. Because of the density (and thus a certain regularity) of meteors in Persieds, it may only "seem" that you are hearing a particular meteor.

Below an altitude of 70 km (42 miles) sound travels between 967 - 1115 fps. That's roughly about 1 mile every 5 seconds. If the meteor is 100 miles away, the sound you hear happened about 8.3 minutes ago since the lag for light across the same distance is instantaneous for all intents (i.e. about .0000537 seconds).

So, I think that "sizzle" is coming from somewhere else. :D

You are essentially correct - if what is heard are sound waves. There is a phenomenon known as 'electrophonics', where the energenic plasma created by a low mass meteor breaking up in Earth's atmosphere creates VLF plasma resonating in the 30Hz - 30kHz range, which is audible. The plasma is electromagnetic, and does not obey the speed of sound.

The first time I heard a meteor the same time I saw it (5 years ago, the Leonoid metor shower), I thought 'impossible!' too. But, it's the same principal by which you can hear the Northern Lights. (A very cool experience in itself!)

http://science.nasa.gov/headlines/y2001/ast26nov_1.htm

[Hotrauder]

morning gas ? :baaa:

Lisa, you may be on to something. I ordered those absolutely the best ever crab cakes from G&M. They were great. thanks to CAM for the 411. However, Penny thought she heard meteors for 3 days. Dennis:lol:

[DefyantExWife]

nice Dennis http://img.photobucket.com/albums/v682/snexus/rolleyes-1.gif

[Bluerauder]

You are essentially correct - if what is heard are sound waves. There is a phenomenon known as 'electrophonics' ...
Very interesting ..... you learn something new everyday. Now, I can go home since I've reached my quota. :D

Of course, human ears can't directly sense radio signals. If Keay is right, something on the ground -- a "transducer" -- must be converting radio waves into sound waves. In laboratory tests, Keay finds that suitable transducers are surprisingly common. Simple materials like aluminum foil, thin wires, pine needles -- even dry or frizzy hair -- can intercept and respond to a VLF field.

[Dr Caleb]

Ya didn't think I'd make it an easy exercise for the student, did ya? ;)

[Bluerauder]

Ya didn't think I'd make it an easy exercise for the student, did ya? ;)
But it seems that you had a small class today. :D As long as I can keeping learning ... I figure my brain cells can hold off Al Zeimer. ;)

[LordVader]

:P Thanks for the "heads-up"! But you guys are making my head hurt! Too much technology at work on this thread. I just wanna see pretty lights.