# If there is no gravity in space

#### Arhamx

Then why not things like pens and other stuff small stuff gets attracted to the gravitational force released by the space travellers when they are in space as there is no other force that is preventing this like earth’s gravitational force?

Moderator
Everything that has mass has a gravitational force. It's just so weak that the force of attraction takes a VERY long time to actually make an object move in a way that is noticeable to the human eye.

If a crewman accidentally left a pen floating outside the International Space Station, eventually, the station's force of gravity would draw the pen to it (assuming no other force interacts with the pen in any other way).

-Wolf sends

#### vincenzosassone

Pardon? This question is very very long, and complex too.
Anyway, if I understand correctly, you're asking why small objects aren't attracted by other small ones. Well, as a matter of fact that isn't true at all, since these objects we are talking about (a pen, a man, for instance) attract each other. According to Newton, gravity is given by an equation: F=(G*m1*m2)/d^2; where G is a constant, m1 and m2 are the masses of the two bodies, and d^2 is the distance squared. Now, the distance isn't so important in our speech, but masses are! m1 and m2, in the case of a man into space with a pen close by, are very week, their impact in this formula is really low. In the case of a man on Earth, there is Earth with its mass that is a way bigger than a pen or a man, so the force is stronger. When the force is strong, the process is quick and visible (if you jump now, you probably return with your feet on Earth quikly), when the force is week, we basically need to wait a lot for this process to get complited, and at the same time, this isn't visible.

#### Catastrophe

##### "There never was a good war, or a bad peace."
If there is no gravity in space

Is it not the case that the orbital velocity is adjusted to neutralise Earth gravity?

Cat

vincenzosassone

#### Challenger007

Then why not things like pens and other stuff small stuff gets attracted to the gravitational force released by the space travellers when they are in space as there is no other force that is preventing this like earth’s gravitational force?
Do you think the human body emits gravity? This sounds strange, because there are a number of factors that cause gravity on Earth. Man is only a particle in the universe and his potential is clearly not enough to attract objects to him.

#### vincenzosassone

There isn't a lot to talk about. Gravity can be "produced" (even though this isn't the correct term to use now) by every body with mass (fermions). Since all of us (men), Earth, planets, asteroids, etc... have mass, we have gravity.
According to Newton, gravity is given by an equation: F=(G*m1*m2)/d^2; where G is a constant, m1 and m2 are the masses of the two bodies, and d^2 is the distance squared.
there is the point.
Man is only a particle in the universe and his potential is clearly not enough to attract objects to him.
Correct, but this isn't the way to say it in my opinion: men have mass, so, they basically warp the fabric of the space-time. Their influence, though, isn't enough to move objects around them, or better, they can't move objects so much to be percieved by us.
And what do you think?

Catastrophe

#### Catastrophe

##### "There never was a good war, or a bad peace."
There isn't a lot to talk about. Gravity can be "produced" (even though this isn't the correct term to use now) by every body with mass (fermions). Since all of us (men), Earth, planets, asteroids, etc... have mass, we have gravity.

there is the point.

Correct, but this isn't the way to say it in my opinion: men have mass, so, they basically warp the fabric of the space-time. Their influence, though, isn't enough to move objects around them, or better, they can't move objects so much to be percieved by us.
And what do you think?
I agree. Cat

vincenzosassone

#### David-J-Franks

If you search Google for a man called Cavendish/gravity he used to do experiments with gravity. He used to hang 2 weights on a torsion wire and he was able to measure a very small Twist when another mass was put next to one of these hanging weights. I think he was also able to determine whether there was a mountain nearby as well. Without searching anymore that's all I know.

sideband

#### David-J-Franks

Our sun formed just from the gravity of a gas and dust cloud collapsing in on itself. The remaining dust circling the sun then attracted to itself to form ever bigger and bigger clumps of matter to form the rest of the planets. All of this of course took millions of years.

#### Catastrophe

##### "There never was a good war, or a bad peace."
If there is no gravity in space

That is the question. It is not, if there were no gravity anywhere. Thus to talk about planets falling apart is not what the OP intends.

Cat

#### Slarty1080

All material objects attract all other material objects. It's just that gravity is a very very weak force and a man sized mass has such a tiny gravitational attraction that it's too tiny to measure by any ordinary means. Its only when mass is heaped together in enormous quantities of millions of millions of millions of tons that it becomes a force to be reckoned with in planets like the Earth.

Things like the International Space Station and other objects in orbit around the Earth are still effected by Earths gravity in a similar way that a free fall parachutist is. They are constantly falling towards the Earth under the force of gravity. The reason why they don't fall down is they are moving so fast sideways (parallel to the Earths surface) that the Earths surface curves sufficiently to give them enough space to fall into and they just orbit around and around.

sideband

#### Catastrophe

##### "There never was a good war, or a bad peace."
If there is no gravity in space

So it is a valid approach to compare very little to no gravity.

Cat

#### Slarty1080

If there is no gravity in space

So it is a valid approach to compare very little to no gravity.

Cat
Yes in some cases it is a valid approach, but I'm not sure I quite follow? Perhaps the question is a little vague?

#### Pogo

There is no place in the universe where there is truly zero gravity. The closest would be in a void millions of parsecs from any galaxies or other mass. We would have to put two objects (astronaut and pen?) in an otherwise empty universe.
Objects orbit because there is a balance between the gravitational attraction of the parent body and the orbiting body and the orbiting body trying to follow Newton's first law trying to keep on a straight line.
In one second, the Moon travels along its orbit about a kilometer, but, it falls maybe a tenth of a centimeter at the same time, so it's continuously falling until it falls all the way around its orbit.
Ya have to realized that while in orbit, the Earth outweighs the ISS, astronaut, and pen altogether by more than 10^23 times. It's gotcha, any gravity between the objects are less than minuscule.
The ISS is in orbit with the same balance. The astronaut inside the ISS is not in zero gravity. If he/she is floating and not holding onto anything, he/she is in an independent orbit around the Earth inside the ISS. A pen floating in the ISS is also in an independent orbit. Chances are, HVAC air currents will drag the astronaut and pen into a wall in short order.
Placing an astronaut and the pen in a universe where otherwise ain't nuttin', let's say a meter apart, and starting with absolutely zero speed, it'll take hundreds of years for them to collide. In a one meter orbit, the period would likely be thousands of years. That poor astronaut will get tired of waiting.

#### Jeremy8733

Some people think that there is no gravity in space. In fact a small amount of gravity can be found everywhere in the space. Gravity, however, does become weaker with advancedmd distance. It is possible for a spacecraft to go far enough from Earth that a person inside would feel very little gravity.

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#### David-J-Franks

There is no place in the universe where there is truly zero gravity. The closest would be in a void millions of parsecs from any galaxies or other mass. We would have to put two objects (astronaut and pen?) in an otherwise empty universe.
Objects orbit because there is a balance between the gravitational attraction of the parent body and the orbiting body and the orbiting body trying to follow Newton's first law trying to keep on a straight line.
In one second, the Moon travels along its orbit about a kilometer, but, it falls maybe a tenth of a centimeter at the same time, so it's continuously falling until it falls all the way around its orbit.
Ya have to realized that while in orbit, the Earth outweighs the ISS, astronaut, and pen altogether by more than 10^23 times. It's gotcha, any gravity between the objects are less than minuscule.
The ISS is in orbit with the same balance. The astronaut inside the ISS is not in zero gravity. If he/she is floating and not holding onto anything, he/she is in an independent orbit around the Earth inside the ISS. A pen floating in the ISS is also in an independent orbit. Chances are, HVAC air currents will drag the astronaut and pen into a wall in short order.
Placing an astronaut and the pen in a universe where otherwise ain't nuttin', let's say a meter apart, and starting with absolutely zero speed, it'll take hundreds of years for them to collide. In a one meter orbit, the period would likely be thousands of years. That poor astronaut will get tired of waiting.
There is no place in the universe where there is truly zero gravity. The closest would be in a void millions of parsecs from any galaxies or other mass.
I agree with the first sentence but without doing further research I think you might find close to zero gravity nearer than you thought if you search Google for something called Lagrange points. These Lagrange points are places in the solar system where the gravity balances out between planets or planets and the sun. For example, there is 1 Lagrange point between the Earth and the sun and there is close to zero gravity there. There are several other Lagrange points but I don't know any details about them. I also vaguely remember that these Lagrange point have asteroids or comets stuck in them and we also have satellites or instruments positioned in these points as well, I think.

#### Pogo

Correct, for the earth for example, L1 is between the Sun and Earth, L2 is further out from the Earth, L3 is on the opposite side of the Sun, L4 is 60 degrees ahead, and L5 is 60 degrees behind the Earth. They would be balance points between gravitational sources, but they are somewhat unstable, a spacecraft would need to do Station keeping burns to remain correctly. Any variation would overwhelm the astronaut/pen gravity scenario, much like being in orbit. Even the Trojans wander considerably from the true L points, and it seems a few leave and a few join from time to time.

#### Helio

Placing an astronaut and the pen in a universe where otherwise ain't nuttin', let's say a meter apart, and starting with absolutely zero speed, it'll take hundreds of years for them to collide. In a one meter orbit, the period would likely be thousands of years. That poor astronaut will get tired of waiting.
The Casimir Effect makes this claim more interesting. Two plates close together will be pushed together faster than their gravitational mass will allow.

Helio

#### Pogo

This seems like what allows a machinist to 'wring' together gauge blocks to one another to stack up to a certain dimension for measuring purposes. They stick together very well even though they are just steel blocks with nothing making them stick together except the attraction of the atoms they are made of (if done correctly).
But this effect works only on nanometer scales, not the separations we can see and measure. This may also be some of the difference between static and dynamic friction when making a stationary object move, once it starts, it gets easier.

Also, in close proximities, the electromagnetic force may affect the attraction of objects.

The inverse square law works when objects are separated fairly far. In close proximity, the inverse square will be affected by the shape of the objects. Long objects become a line source and large planar objects will become a planar source as opposed to a point source, the law no longer applies. Even spacecraft in low orbit will be effected by the earth's flattening even though it's only about 0.3%, as non-spherical gravity source.

The strong and weak forces probably don't do much unless objects get really close, like subatomic scales.

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#### BoxCar

In high school Physics class I once asked our teacher about space travel where there was "No Gravity"> Her answer was "There IS NO such place where there is NOT gravity" and she was RIGHT> What we call gavityless is simply a suspension or balance of forces between radial acceleration of S/C in orbit vs Earth's gravitational pull> Just as on the Equator U R traveling 1000mph east but U'd only notice it IF U were on a shooting range & U'd notice RISE in bullet trajectory IF U fired back to the West as your target is moving towards U at 1000mph but the bullet is falling at 32fps when it leaves the muzzle> Not the same going East

#### Helio

The inverse square law works when objects are separated fairly far. In close proximity, the inverse square will be affected by the shape of the objects. Long objects become a line source and large planar objects will become a planar source as opposed to a point source, the law no longer applies. Even spacecraft in low orbit will be effected by the earth's flattening even though it's only about 0.3%, as non-spherical gravity source.
That's a good point, except I would rephrase it to say the inverse square law is valid but cannot be treated as a simple point source as one gets closer to large objects, where varying densities must be taken into account.

Catastrophe

#### Catastrophe

##### "There never was a good war, or a bad peace."
That's a good point, except I would rephrase it to say the inverse square law is valid but cannot be treated as a simple point source as one gets closer to large objects, where varying densities must be taken into account.
Is there not some similarity, to the stretching of a body (person) entering a black hole?

Cat

Helio

#### Helio

Is there not some similarity, to the stretching of a body (person) entering a black hole?

Cat
Yes, the inverse square law is working fine during spaghettification. Using the law, the calculation shows a much greater force is upon the closer part of the body. This is why there is no spaghettification for a SMBH since the force gradient along the body is minimal when the distance is far greater (thanks to the inv. sq. law).

Catastrophe

#### Slarty1080

I agree with the first sentence but without doing further research I think you might find close to zero gravity nearer than you thought if you search Google for something called Lagrange points. These Lagrange points are places in the solar system where the gravity balances out between planets or planets and the sun. For example, there is 1 Lagrange point between the Earth and the sun and there is close to zero gravity there. There are several other Lagrange points but I don't know any details about them. I also vaguely remember that these Lagrange point have asteroids or comets stuck in them and we also have satellites or instruments positioned in these points as well, I think.
The Lagrange points are not zero gravity points. The gravitational attraction of the Earth stretches out to them. There is a net zero force due to the counter acting gravity of the Sun and or the Moon, but gravity is still present just balanced.