Is There Gravity In Space? (Why Are Astronauts Weightless?)

If you've seen footage from the International Space Station or any of the space shuttle missions, you know that astronauts float around as they orbit the Earth. Why is that? Is it because the gravitational force on them is zero in space? (Or nearly zero?) The truth is that the strength of the gravitational attraction is only slightly less than it is on Earth's surface. So how are they able to float? Well, they aren't floating - they're falling, along with the space station. They don't crash into the Earth because they have a huge orbital velocity. So as they accelerate towards the Earth, the Earth curves away beneath them and they never get any closer. Since the astronauts have the same acceleration as the space station, they feel weightless. It's like being in a free-falling elevator (without the disastrous landing).

Director of Photography: Stefan Smith
Camera Assistant: Raa Perajeev
Boom Operator: Maha Sivalingam

Production Coordinator: Adrian Tan
Production Assistants: James Peniata, Pratheep Ramachandran

Category:

Education

Tags:

• weightlessness
• no gravity in space
• astronauts
• international space station
• floating
• gravity
• orbits
• gravitational force
• satellites
• space station

[Hmjals]

You just said that the force on the astronaut is almost as much as the force on us in earth while the formula proves that the further you are from the subject, the weaker the gravitational force. In this case the distance is 400km more which definitely means the gravitational force has decreased with large numbers.

[1veritasium]

@Hmjals The force would be 88% as much. That's what I mean by almost as much. 400km is not that large compared to the radius of Earth which is ~ 6400 km

[1LaSmyth]

So if gravity does play a part, then why don't the astronauts experience G-force when orbiting at that speed?

[1veritasium]

@1LaSmyth do you mean G-force because of the high speed? You don't experience G-force if you're going fast - only if you are accelerating (changing your velocity). Now astronauts are changing their velocity, but at the same rate as their satellite so there is no relative acceleration between the two so there is no contact force.

[0001robm]

I get Newton's Cannonball and it makes sense with a vector diagram as well, but why doesn't the earth gravity eventually 'win'. I mean act like a "tractor beam" and slow it down like its sprillaing down a drain?

I know you're right, but its like watching a good card trick and you know its a trick but can't figure it out..

[1veritasium]

@0001robm I don't know if it's really a trick - the force acts only towards the centre of the Earth - and the velocity of an orbiting object is at 90 degrees to this force. Hence the force can't slow it down - only change its direction. Other forces can (and do) slow satellites down like a bit of friction with the few molecules very high up in Earth's atmosphere. In which case they need a little boost from time to time to increase their altitude and stop them 'spiralling down the drain'

[TheCaphits]

I liked the part where he proved I'm an idiot.

[DanielFreyr22]

Can you make a tutorial on how to get as awesome editing skills as you?

[MadCat360]

@Aviatorsmith Indeed. Einstein likened it to standing in a big chest that was constantly accelerating. The person standing in a chest that was experiencing acceleration equal to earth's gravity would have no idea whether the acceleration was from gravity or propulsion. In this limited example, they are practically the same thing.

[TheVerandaguy]

In LEO, the Earth's gravity is weak enough to have a practically negligible effect on something with a mass as insignificant as that of an astronaut, or a space station. The reason the Moon is affected is because of its own mass, several million (or billion, I don't know the exact numbers) times greater than that of the ISS.

If the Higgs Boson is ever conclusively proven to exist and studied, there'll also be proff of the Higgs Field, proving that gravity has an infinite range.

[Aviatorsmith]

@Moloch6666 G-force has nothing to do with the gravitational pull of the Earth. 1G is just defined as approx. 9.81m/s^2. If you accelerate in space, you would experience the exact same G-force as if you accelerate on Earth (if you exclude the acceleration due to Earth's gravity).

[iluvroknmylife]

@SillyEddyPhotography thanks Alooot :D U deserve a subsciption :D

[SillyEddyPhotography]

@iluvroknmylife Because gravitational acceleration is still pulling the satellite in. Imagine gravity to be a rope that is between the satellite and the centre of the Earth... You speed forwards, but the rope pulls you in and forces you to orbit the planet. If you go too fast, the rope breaks and you fly into space. If you're too slow, then the rope just pulls you back down into Earth's atmosphere and you burn up!

[iluvroknmylife]

@SillyEddyPhotography Thanks Alot...Appretiate ur Tyme... but as the satellite is thrown Vertically with dat tat speed then how it circulates the earth [horizontally] with dat speed?? :D stupid question though :p

[SillyEddyPhotography]

@iluvroknmylife Because when you launch a satellite, you have a massive rocket in it that throws it up into orbit. There is effectively no air in space, so there is no air resistance, so the satellite doesn't slow down. I mean, eventually it will slow down, but it will take a long time of colliding into the very little amounts of matter up there. As they go at 20,000mph they fall, but they fall past the Earth, and then this creates a circular motion... Look up Newton's Cannonball

[iluvroknmylife]

I Dont understand the part...that "the Earth's surface curves away from them"..and 1 more question..how is dat much velocity generated by the satellite?? Plz reply..oOo Yea ur Videos Are really Amazing.. Thanks :D

[T3AI2S]

I learned this in physics and all i was thinking was "man i wished he interviewed me, cause then I'd feel smart for once in my life"