Pressure: What's it like out there?
Given that the pressure we experience on a daily basis is actually the weight of the atmosphere sitting on us what does that suggest about space? There is certainly not much stuff out there so perhaps its not much of a surprise that the pressureout between the earth and moon is around 3 nPa. That little 'n' means nano as in nanotechnology. Nano is the prefix we use to indicate 1 billionth of a thing. That's really small!!
But here's a practical application: You're helping do maintenance work on a spaceship on the way to Mars as McGyver's assistant. You slip with the screwdriver and put a little hole in your space suit. It's pretty clear this is not going to turn out well unless you can stop the leak. If you slap a piece of duct tape over the hole will it hold and save you or not? Remember there is no pressure on the outside and 100 kPa (1 atm or 14.7 psi) on the inside. A big hole would be 1 cm2 which would represent a force from the inside of about 1 kg. The adhesive strength of duct tape is roughly 2 kg/cm2 which basically means if you can slap a patch over that hole you're good. Even a pretty big hole can be managed if you get right on it! Good to know.
While it's not top of everyone's mind its worth pointing out that there are really remarkable differences in the atmospheres and pressures of the different planets even when we think of them as much like our planet. If you follow the link above to the NASA planetary data site you will find the the surface pressure on Venus is 92 bar (92 times our own 1 atm) while Mars is less than 10 mbar (0.1% of ours). Places like Jupiter where it is hard to define what the surface might be are estimated to be more than 1000 times our own atmospheric pressure. We'll compare this to the bottom of the ocean next....Just food for thought.
