[amsat-bb] Re: AMSAT-NA totally metric? and now almost totally off topic.

[Tony Langdon]

At 03:38 PM 1/22/2007, Sil - ZL2CIA wrote:

>Are you really weightless in space? Surely you're just in free fall. 
>When the  term "weightless" is used to describe the condition 
>astronauts experience, this is surely a literary term, rather than a 
>scientific one.

As it turns out, the answer is "yes" or "no".  It depends on your 
frame of reference and the definition you use.  Using the definition 
that weight is the force exerted by gravity, then one would presume 
at a point near the Earth - Moon L1 point, you would be very nearly 
weightless (there would be some unbalanced gravitational influence of 
the Sun most of the time, but you could move around and null that out too...).


>Why spend the $20.000.000 (or 20,000,000 if that's your custom) you 
>mention, when you could achieve that same "weightlessness" by 
>jumping out of a building (if for a shorter time, of course, and 
>with a riskier outcome).

A _much_ shorter time (remember air resistance quickly builds up so 
you soon have the same reaction force from air resistance as you do 
standing on the ground - i.e. you quickly reach terminal velocity).


>Am I weightless when I jump off a chair?

Depends who you ask, but most physics sources do say "no" as they 
define weight purely in terms of gravitation.


>Are orbiting satellites "weightless"?

See above, but after looking at a number of sources, I'll concede 
"no" (assuming the strict gravitational definition of weight).

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