
Voyager 2 Spacecraft will cross "termination shock" in Late 2007 or Early 2008 - nickb
http://www.newsroom.ucr.edu/cgi-bin/display.cgi?id=1720
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pg
What's significant about whether particles there are travelling above or below
the speed of sound? Surely there are not enough of them to produce the sort of
compression waves that cause problems for supersonic jets.

~~~
DanielBMarkham
For what it's worth, I read about this on a couple of other sites.

From what I understand, particles build up along the compression front,
causing a sort of magnetic storm for things passing through it. The effect is
magnetic and not compression-based as it is in jets. One anonymous poster on
/. claimed to be from JPL and said they were worried about having some of the
electronics in the spacecraft fry as it passed the boundary. For some reason
that made me think of old Star Trek episodes -- "Where No Man Has Gone Before"

I also learned that, far from what we've been told, there IS sound in space.
It travels around 100km/sec in the near vaccum, but nobody has come up with a
way to measure pressure waves at that extreme low inensity. Sounds like a cool
thing -- wouldn't it be neat to listen to the universe?

~~~
ivankirigin
It's all about the density. Even what we consider nebulae are small fractions
of an atmosphere. Sound as we think of it just doesn't apply.

But for SciFi shows that don't respect the audience enough to have no sound in
space, I choose to believe they just placed simulated microphones near the
explosions. The particulate matter and smoke could temporarily host the sound
in space.

Also, sound travels slower in lower density areas, not faster. Where did you
get this 100km/s number? I think it is a neutron star where the matter is so
dense, sound waves move so fast as to cause relativistic effects. But of
course all our models for sound would fail in a Singularity. Just add sound to
the long list of things we have no idea how to model in Black Holes.

~~~
DanielBMarkham
I'm in way over my head, but I'll keep going. Hey this is the internet -- lack
of knowledge never stopped folks from talking about stuff before! You're
probably much better-informed.

This sound question is very much like the "if a tree falls in the wilderness
and nobody is there to hear, does it make a noise?" By sound I mean pressure
waves, which exist I guess everywhere (from what I am hearing) except for a
complete and total vaccum. But at the level of just a 1-1000 particles per
cubic meter, there's not enough matter there to make something like the human
eardrum work. So yes, it's sound, but no, we could never hear it. Does that
make sense?

Here's one of the comments I sourced for my post. Like I said, I am a complete
novice in this area.

[http://science.slashdot.org/comments.pl?sid=373279&cid=2...](http://science.slashdot.org/comments.pl?sid=373279&cid=21507799)

~~~
ivankirigin
That comment was over my head I think.

