The biggest myth about outer space is that there is no gravity in space. People do not have a good understanding of what weightlessness is. They see astronauts floating around inside and outside a spacecraft and reach the conclusion that there is no gravity.
Anywhere mass and space exist, gravity exists. Gravity is the curvature of spacetime due to the presence of mass. The gravitational influence from the Sun that keeps the Earth in orbit around the Sun is felt equally by the astronauts in space. The gravitational influence from the Earth that keeps the Moon and the ISS in Earth orbit is also felt by the astronauts floating inside and outside the spacecraft. If these influences were not felt, the astronauts would not stay in orbit.
At the altitude the astronauts in the ISS inhabit, the gravitational influence from the Earth is 8.75 m/s^2. That is only about 11% less than the 9.81 m/s^2 felt by you and me, on the Earth’s surface.
They are weightless and appear to float because they are in freefall. A spacecraft in Earth orbit is falling towards the Earth (because of gravity) but also moving forward at a speed high enough that the path traveled isn’t straight down, but instead a curve that circles the Earth.
[1] The astronaut is falling and so is their spacecraft. If both are falling, there is no force of one against the other and thus no sensation of weight. We can emulate this freefall here on Earth, in a tall chamber that is pumped to vacuum.
Every bit of matter, from the smallest molecule to the largest galaxy, exerts gravitational force on everything else. If the only two things in existence were you and a hydrogen molecule, both floating in space, it would exert a gravitational tug on you, and you on it. Of course, its gravity attraction would be a minute fraction of yours, but eventually, no matter how far apart you are, you would meet.
ReplyDeleteTrue, but it would be a very long time - even if you and your pet molecule were only inches apart.
DeleteThanks for advertising US flags that are made in china...
ReplyDeleteGrey Man
For all the math, the physics, and most especially the hand waywavey explanations, we STILL don't know what light or gravity is.
ReplyDeleteWe can't emulate freefall in a vacuum chamber for very long, though. If it's 32 feet tall freefall would last one and a half seconds, roughly. (Actually 1.4 seconds) Admittedly, though, if you dropped a falcon feather at the same time you'd hit the ground at the same time.
ReplyDeleteUh, ya ended a good piece with this "We can emulate this freefall here on Earth, in a tall chamber that is pumped to vacuum." ? A much better way is to simply experience negative G's in an airplane.
ReplyDeleteThe Vomit Comet.
DeleteNo need for a vacuum to emulate free fall. I think you're conflating the classic feather and rock experiment - which shows the effect of air resistance on falling - with free fall, which is easily if briefly experienced in a plane flying a parabolic path.
ReplyDeleteGravity is the same everywhere.
ReplyDeleteWhat changes is gravitational force, because the force is an inverse function of the square of the distance between the masses.