[Liskaspexia]

About 8:30 saw a meteorite heading South West of Sydney.

There was a visible fireball and it disappeared from sight within a second or two, enough time to turn my head to the left & it was gone. No sound wave though.

How high is it to not create sound?

[Sertvfdnhgjk]

Not sure, but being high would make it a meteoroid rather than a meteorite.

[ceagstuntee]

> How high is it to not create sound?

Hmm, difficult question to answer without doing a web search. The speed of sound stays remarkably constant up to at least 86 km, but that's not what you're asking. A sonic boom is continually being regenerated by non-linearities in the sound propagation - the higher pressure parts of the wave travel faster than the lower pressure parts and as they overtake they keep the shock wave sharp, until it runs out of energy and then the loudness drops off very rapidly. Meteors become visible at about 100 km up.

Because the sound and heating is produced by ram pressure, the intensity of the sound produced and therefore the distance the sonic boom travels before fizzling out, is going to depend a lot on the mass of the meteor. Just because a high-flying aircraft produces a sonic boom at ground level when flying at a particular altitude doesn't mean that a meteor at the same altitude will.

In other words, I don't know.

[AdobeCreativeSuite]

I think I saw that one also, though I was at altitude and a long way north of sydney. I would suggest it was very high in the atmosphere, a few tens of kilometers, and this is more important than its spot over the ground interns of hearing it.

[Patgaepx]

Not an explanation about why your meteorite made no sound, but an interesting discussion about meteorites that do make a sound.

http://science.nasa.gov/science-news...01/ast26nov_1/
in 1719 astronomer Edmund Halley collected accounts of a widely-observed fireball over England. Many witnesses, wrote Halley, "[heard] it hiss as it went along, as if it had been very near at hand." Yet his own research proved the meteor was at least "60 English miles" high. Sound takes about five minutes to travel such a distance,

[moopogyOvenny]

I've seen them enter, traverse the entire hemisphere of view and depart our atmosphere with no sound at all. Spectacular though.

[Liskaspexia]

Reason I was wondering about height was I've noticed sound attenuates with distance, ie a jet at a few thousand metres is quite loud, whereas a jet at cruising altitude , ~8K, is much quieter so was wondering if there's a height at which the sound becomes inaudible for those on the ground.

Whilst it appeared as overhead it could have been some distance to the west of where I was.

[Thomas12400]

Not an explanation about why your meteorite made no sound, but an interesting discussion about meteorites that do make a sound.

http://science.nasa.gov/science-news...01/ast26nov_1/
in 1719 astronomer Edmund Halley collected accounts of a widely-observed fireball over England. Many witnesses, wrote Halley, "[heard] it hiss as it went along, as if it had been very near at hand." Yet his own research proved the meteor was at least "60 English miles" high. Sound takes about five minutes to travel such a distance,

Thanks for that!

I was unaware of that explanation. I also heard several meteors towards the end of the very same Leonids meteor shower in 2001. I had stayed up all night to watch them. I couldn't understand why I heard some. I do wear spectacles.