Le 15-02-19 03:22, scott a écrit :
>> The density of hydrogen atom in outer space is variable, but the
>> pressure is in the nano-pascal ( 10^-9 ) range, and we live in
>> kilohecto-pascal ( 10^5 ), so the influence of the drag is to be
>> corrected by at least something like a 10^-14 factor.
>
> Drag depends on velocity squared, so that would mean if your velocity
> was 10^7 times higher than on earth, you would experience a similar
> level of drag.
>
> I have no idea what "interstellar velocities are" though, 10^7 or more? :-)
>

The 10^-9 range is for our spacial neigourhood, or relatively close to a 
star. As you travel farther, it drops conciderably. Between the Sun and 
Proxima Centaury, the vacuum around the moon looks like high pressure.

In space, to have a drag equivalent to 100 Km/h on a road, using the 
10^14 factor for Earth region, you would need to travel at over 100 000 
000 000 000 Km/h (10^16 Km/h). That's  /way/ faster than the speed of 
light ! (about 10^9 Km/h)



Alain

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