> Gravity is always present. What you feel as “weightlessness” is actually freefall.
Article makes this seem true, regardless of whether or not you are in orbit. But doesn’t this matter of perspective become ridiculous if you are floating freely in space? As in, yes, you’re “falling” but only because Earth is moving away from you or toward you? Honest question here…
How to define "floating freely" is not easy to define. The potential energy surface of gravitation extends in 1/r wgich makes it a long range interaction. So if the earth attraction is small enough that you want to neglect it, you may still be trapped in the sun potential well. And if you can escape the sun attraction you are still prisoner of the galaxy. There is no 0 gravity, but there is various levels of neglectable gravity of course. But neglectable is always defined relative to whatever you want to measure.
You are never really floating freely, all gravitational wells extend to infinity. The curvature just becomes really small so the resulting acceleration is infinitesimally small too.
The statement is technically true, but slightly confusing because the article talked about orbit being free fall, and about microgravity being in the range of one millionth to one thousandth of earths gravity.
It is certainly possible to get far enough away from anything that gravity is far less than one millionth of earth’s gravity, so it’s no longer microgravity by the article’s criteria. Floating freely would be free fall, but that doesn’t exactly mean what it sounds like when gravity is negligible.
The article also didn’t clarify that at our typical orbital distances for ISS and satellites, gravity is not in the microgravity range, it’s still very strong.
I'm confused, the article simultaneously claims the ISS isn't "zero-G" and is "0G". Is it possible to conduct a true 0G experiment on the ISS, or is there always microgravity i.e. '10⁻³G to 10⁻⁶G'?
There is always microgravity, i.e. residual acceleration due to drag and thrusters, and especially vibrations.
Worst offenders are actually the astronauts, especially when they work out on one of their exercise devices right next to your experiment
There are also tidal accelerations due to not being in the center of mass of the space station.
Robert Forward had a scheme for nulling these over a larger volume using a heavy ring, a technology related to the one he used in the novel Dragon's Egg (which used SFnal superdense matter to enable a space station to exist in close orbit to a neutron star without the tidal forces killing the occupants.)
> Gravity is always present. What you feel as “weightlessness” is actually freefall.
Article makes this seem true, regardless of whether or not you are in orbit. But doesn’t this matter of perspective become ridiculous if you are floating freely in space? As in, yes, you’re “falling” but only because Earth is moving away from you or toward you? Honest question here…
How to define "floating freely" is not easy to define. The potential energy surface of gravitation extends in 1/r wgich makes it a long range interaction. So if the earth attraction is small enough that you want to neglect it, you may still be trapped in the sun potential well. And if you can escape the sun attraction you are still prisoner of the galaxy. There is no 0 gravity, but there is various levels of neglectable gravity of course. But neglectable is always defined relative to whatever you want to measure.
> potential energy surface of gravitation extends in 1/r
What does this mean? Gravity falloff is 1/r^2 right?
Gravitational attraction falls off as 1 / r^2; potential energy falls off as 1 / r. The former (a force) is the derivative of the latter.
https://en.wikipedia.org/wiki/Gravitational_energy#Newtonian...
GP may have used superscript that got stripped, here's a test with normal numbers followed by the superscript version : 0⁰ 1¹ 2²
But what about the point where your own attraction offsets that of any other nearby objects? Wouldn’t that be zero gravity, if the forces cancel out?
You are never really floating freely, all gravitational wells extend to infinity. The curvature just becomes really small so the resulting acceleration is infinitesimally small too.
The statement is technically true, but slightly confusing because the article talked about orbit being free fall, and about microgravity being in the range of one millionth to one thousandth of earths gravity.
It is certainly possible to get far enough away from anything that gravity is far less than one millionth of earth’s gravity, so it’s no longer microgravity by the article’s criteria. Floating freely would be free fall, but that doesn’t exactly mean what it sounds like when gravity is negligible.
The article also didn’t clarify that at our typical orbital distances for ISS and satellites, gravity is not in the microgravity range, it’s still very strong.
I'm confused, the article simultaneously claims the ISS isn't "zero-G" and is "0G". Is it possible to conduct a true 0G experiment on the ISS, or is there always microgravity i.e. '10⁻³G to 10⁻⁶G'?
There is always microgravity, i.e. residual acceleration due to drag and thrusters, and especially vibrations. Worst offenders are actually the astronauts, especially when they work out on one of their exercise devices right next to your experiment
There are also tidal accelerations due to not being in the center of mass of the space station.
Robert Forward had a scheme for nulling these over a larger volume using a heavy ring, a technology related to the one he used in the novel Dragon's Egg (which used SFnal superdense matter to enable a space station to exist in close orbit to a neutron star without the tidal forces killing the occupants.)