Surely the scientists working on (un)manned spaceflight understood the concept of the earth having an upper level to its atmosphere, but how were they able to determine what exactly the physics of space were, before a spacecraft had ever made it out of the atmosphere?

Issues such as:

  • space is a vacuum
  • traveling at incredibly high speeds while in orbit (due to low friction)
  • atmospheric reentry
  • etc

must have been hard to figure out without some sort of actual testing. Was it simply trial and error?

  • 4
    $\begingroup$ They have studied physics and mathematics ... $\endgroup$ Dec 24, 2014 at 9:26
  • $\begingroup$ Well, yeah, but my question is how were they able to observe the conditions and physics of outer space without ever having gone there? $\endgroup$
    – galois
    Dec 24, 2014 at 19:23
  • 1
    $\begingroup$ Before mankind ever sent anything to outer space, there was plenty of stuff up there already, and a lot of that stuff can be seen from down here (especially if you have a telescope). $\endgroup$
    – David H
    Dec 24, 2014 at 23:07
  • $\begingroup$ Are you referring to manmade objects able to give us data? $\endgroup$
    – galois
    Dec 24, 2014 at 23:38
  • $\begingroup$ @jaska No. I am talking about objects that were already in space before humans first sent objects into space, like the Moon or Jupiter or comets, et cetera. $\endgroup$
    – David H
    Dec 25, 2014 at 1:25

1 Answer 1


I'll expand a little bit my "oracolar" comment above (with less fun) :

They have studied physics and mathematics, and physics and mathematics, and ...

There was "explorations" of "outer layers" of atmosphere with balloons.

There ware the "experiments" made with rockets (mainly German) used during WW II.

But mainly, there were faith in the immense power of newtonian mechanics (and mathematics) to predict the correct behaviour of bodies subject to the "law of motion".

With insight, space travel (think about a 10 years travel of a little "spacecraft" able to "land" on a comet after a journey of millions of km) has been - for me - the "paradigmatic" cased of verification (if any) of a scientific theory.

I mean : we can speculate about skepticism, philosophical realism and any other kind of "mental experiment" about the reality of the world "out there".

But, if we are able to compute a ten years long trajcetory with this precision... this means that the theory is definitively correct.

See e.g.

If you can spray them, then they are real.


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