I understand why astronauts orbiting the earth are weightless since they are in constant freefall. But why are the astronauts who went to the moon weightless?
I imagine that as you accelerate away from the earth towards the moon, you are no longer falling but are instead climbing. Intuitively, I think that this would give you some kind of gravity. Coming back I would think that you are constantly falling towards the earth, so I understand how the return journey would be weightless.
In: Physics
theye are weightless as soon as thrust and friction (atmosphere) disappears.
Because, as you said, they are in freefall
Falling is not the best word because it implies going ‘down’. Objects in orbit are not falling so much as they are in free fall. The Apollo astronauts were in earth’s orbit all the way until they got close to the moon. Their orbit was simply very eccentric or lopsided. When you throw a ball straight up, as soon as it leaves your hand it is in free fall even as it still goes up.
Whenever gravity is the only force acting on you then you will feel weightless. This includes ballistic trajectories (throwing something) and all orbits including ones that take you to the moon.
Imagine that there’s a really large lake, miles across in every direction. It’s fed by a small rivers and drained by one too. If you were on a boat and close to the draining river, you’d be affected by its flow and would have to power the boat to not get sucked into their currents. But when you’re on the middle of the lake, you don’t feel affected by any of the rivers. You could sit out there for hours and barely drift.
This is a bit like gravity and space. You can feel the effects of gravity close to a large source of it like a planet (or river in the description), and though there is still some gravity in space it’s hard to discern it since the force weakens a lot when you get away from the source. It’s still there, but you only feel the large effects when you’re close to it.
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When you accelerate you would be pushed back into your seat, but for the majority of the flight path the spacecraft is not accelerating (that much) so the space craft is “falling” with the astronauts.
The engines are off for the majority of the time.
the moon has its own gravity, it is just a fraction of our own (I think 1/7th or so), so once you’re on the moon you are indeed not “weightless”. but you are “lighter”.
gravity is essentially just a form of acceleration, so if you accelerate in some direction you will experience more or less gravity (depending on your situation and the direction you’re accelerating to).
when you’re “falling” you’re NOT weightless. falling means you’re getting accelerated towards something.
It’s not exactly “falling.” Falling is the inertia feeling. The feeling of the Gs from the acceleration. Or from slowing down. They are only weightless because the gravity well of earth, like a magnet, pulls down on the craft and the people in it, but after a certain distance, there is an illusion of freeness, but for a while the earth will still have you falling towards it. At a certain point, you start to fall to the next closest object. I.e. : the moon.
Btw The higher your altitude, the weaker the earths pull is on you. I learned that a week or two ago. But i thought i already kinda knew that.
The Apollo craft were in an extended orbit, simply an orbit which got wider as they approached the Moon.
The craft described an arc between Earth and Moon, not a straight line.
While on the Moon, the astronauts were not weightless.
They were still in orbit around the earth (freefall), it was just a highly elongated orbit. More like a comet that goes way out into space then comes near the sun. They had to fire their boosters again to get into orbit around the moon.
if you’re moving at a constant speed you don’t feel the effect of gravity, so when they’re accelerating they feel pushed back to their seats, when they decelerate they feel pushed to the front, when V= cte they’re in pseudo 0 gravity
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