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Join Date: Feb 2005
 
2011-02-18, 10:58

Quote:
Originally Posted by Kraetos View Post
As the solar wind expands outwards, it covers more space, which means it loses density. Although the interstellar medium is usually called a void, it is not completely devoid of matter. IIRC it's something like one atom per square meter.

And since it has mass, it has pressure. As the solar wind expands, it's density decreases. At about 80 AU, it's pressure drops below that of the void's, and thus, it gets "pushed" back towards the sun. We call this point the termination shock.
Quote:
Originally Posted by Curiousuburb View Post
And the 'shock front' isn't a fixed distance out because of variability of solar activity.
Thanks for the explanations. Thinking about it more, I think I tripped over the word "shock" because it seems to imply there's a barrier that would destroy an object that tried to pass through the barrier (a la sound barrier - if plane can't withstand the stress, well... no more plane.) but Voyager apparently seemed to survive the trip past termination shock just fine and is supposed to be approaching bow shock, (hope I got it right)

I also have this idea that because gases are supposed to diffuse, it's weird to imagine there's a sphere of mass being trapped by what is relatively a void. Thank goodness my lack of imagination does not invalidate the reality!
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