Comment on Shine a laser on the moon
FooBarrington@lemmy.world 2 days agoNo, we don’t yet know why space is expanding. But space has way way waaaaay lower pressure than the earth atmosphere since it’s almost empty. It even keeps sucking away bits of our atmosphere.
lath@lemmy.world 2 days ago
You’re telling me nibbling bits of our atmosphere isn’t a form of pressure exerted towards it?
“Hey, gimme your gases! Only just a bite, come on! Yum! Yum!”
benderbeerman@lemmy.world 2 days ago
Ok, now I can’t tell if you’re just being funny, so I’ll answer you in good faith.
Yes, but it’s a negative pressure compared to the pressure of our atmosphere, so also… No.
There’s an inherent property of an object with mass to be attracted to other objects with mass. It’s a somewhat weak force, but it does exist. This force is known as gravity. Now picture a sheet being held at all 4 corners, then having a bowling ball rolled to the center of it. The sheet is like space and the bowling ball is like our planet (or any other celestial body, really) that sag of the sheet is gravity. Now put a marble on the sheet and you’ll see the force in action. Put that marble fast enough away and it won’t even roll toward the bowling ball.
The Earth’s mass produces enough gravity to retain a bubble around it, otherwise known as “atmosphere”. The atmosphere has weight, due to the mass of the gasses that are being produced on the planet. The further you get from the center of the planet, the lower the weight of the gasses above you. This is what causes the pressure known as “atmospheric pressure” which is around 14.7lbs inward toward the center of the planet on every in^2 of surface at sea level, whether liquid, solid, or gas.
Beyond a certain point of our atmosphere, this weight becomes virtually non-existent. There are still other gasses, dust, rocks, particles, radiation and other energies, etc… but there’s not enough of them close enough to sufficiently pressurize the space between the stars or planets to the degree that our own gasses do to us.
This negative pressure differential is colloquially known as a vacuum, albeit an imperfect vacuum.
lath@lemmy.world 2 days ago
Hmm… I am indeed being funny as per the community we’re in, but thank you for the good faith answer.
In conclusion: Sooo… It’s not really a vacuum, but it’s kinda a vacuum or at least an acceptable form of vacuum.
Qed. 🙃