# The Naked Scientists Forum

### Author Topic: How much does the Earth weigh?  (Read 56440 times)

#### imatfaal

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##### How much does the Earth weigh?
« Reply #25 on: 01/12/2010 12:32:33 »
Foolosophy - perhaps if you spent a moment with a basics physics text or even on wikipedia; the recommended reading topic is vector quantities with reference to velocity and acceleration  (magnitude and direction).  You will soon learn that scalars such as speed are not same as vectors such as velocity.  Both forms of reference will also have a section on circular motion - that will fill the most obvious gaps.

#### Foolosophy

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##### How much does the Earth weigh?
« Reply #26 on: 01/12/2010 12:48:18 »
Foolosophy - perhaps if you spent a moment with a basics physics text or even on wikipedia; the recommended reading topic is vector quantities with reference to velocity and acceleration  (magnitude and direction).  You will soon learn that scalars such as speed are not same as vectors such as velocity.  Both forms of reference will also have a section on circular motion - that will fill the most obvious gaps.
you are still claiming that the earth has weight because its accelerating????

Its a physical fact that the weight of the earth is exaclty equal to zero

reason?? because its in free fall motion around the sun

Its the same reason why astronauts are weightless in orboting space stations

are you disputing these facts?

#### Foolosophy

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##### How much does the Earth weigh?
« Reply #27 on: 01/12/2010 12:52:43 »
Foolosophy - perhaps if you spent a moment with a basics physics text or even on wikipedia; the recommended reading topic is vector quantities with reference to velocity and acceleration  (magnitude and direction).  You will soon learn that scalars such as speed are not same as vectors such as velocity.  Both forms of reference will also have a section on circular motion - that will fill the most obvious gaps.

Are you still claiming that the earth has a value for WEIGHT?

The fact is that the earth is in free fall motion around the sun and so its weigth is equal to exactly zero - its weightless.

Why do astronauts experience weightlessness in orbiting space stations?

Are you disputing this simple high school physics assigment?
« Last Edit: 01/12/2010 12:54:25 by Foolosophy »

#### QuantumClue

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##### How much does the Earth weigh?
« Reply #28 on: 01/12/2010 13:56:33 »
Foolosophy - perhaps if you spent a moment with a basics physics text or even on wikipedia; the recommended reading topic is vector quantities with reference to velocity and acceleration  (magnitude and direction).  You will soon learn that scalars such as speed are not same as vectors such as velocity.  Both forms of reference will also have a section on circular motion - that will fill the most obvious gaps.

Are you still claiming that the earth has a value for WEIGHT?

The fact is that the earth is in free fall motion around the sun and so its weigth is equal to exactly zero - its weightless.

Why do astronauts experience weightlessness in orbiting space stations?

Are you disputing this simple high school physics assigment?
I don't think this is technically correct. This is the kind of thing taught in freshmen college, but a deeper understanding of F=Mg suggests otherwise.

F=Mg still applies in space. Technically, astronauts still have a weight because there are gravitational forces acting on the particles of their bodies.

#### QuantumClue

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##### How much does the Earth weigh?
« Reply #29 on: 01/12/2010 14:50:23 »
For instance, usually in very elementary physics, weight is the force exerted on a mass. The acceleration ''g'' is not zero in space. So setting g=0 for W=Mg is not exactly correct. It is true we experience weightlessness, but there is some debate as to whether this is technically correct.

#### imatfaal

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##### How much does the Earth weigh?
« Reply #30 on: 01/12/2010 15:45:34 »
Foolosophy

Firstly - you seem to have drawn back from your claims that the earth isn't accelerating, glad to see you have read up on vectors v scalars and circular motion.  Secondly, you need to understand what free-fall means.

Free-fall motion is when the only force experienced is that of gravitational attraction.  We feel gravitational attraction on earth - but on earth there is also a normal force (equal and opposite) from the ground; this is why we don't sink through the floor.

Astronauts in a space station are in orbit - they are in freefall, but it is completely incorrect to say that there is no gravitational attraction towards the earth.  If they were not continually accelerating (due to a force) towards the earth they, and their tin can, would fly off at a tangent.  They weigh something (not as much, but something) in space just as much as they do when they jump in the air when back on planet earth.  Just because there is no normal at an instant in time does not mean that there is no attraction/force - it is that their attraction to the earth is counteracted in a different manner than the normal force that we suffer.

#### Foolosophy

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##### How much does the Earth weigh?
« Reply #31 on: 01/12/2010 22:04:21 »
Foolosophy

Firstly - you seem to have drawn back from your claims that the earth isn't accelerating, glad to see you have read up on vectors v scalars and circular motion.  Secondly, you need to understand what free-fall means.

Free-fall motion is when the only force experienced is that of gravitational attraction.  We feel gravitational attraction on earth - but on earth there is also a normal force (equal and opposite) from the ground; this is why we don't sink through the floor.

Astronauts in a space station are in orbit - they are in freefall, but it is completely incorrect to say that there is no gravitational attraction towards the earth.  If they were not continually accelerating (due to a force) towards the earth they, and their tin can, would fly off at a tangent.  They weigh something (not as much, but something) in space just as much as they do when they jump in the air when back on planet earth.  Just because there is no normal at an instant in time does not mean that there is no attraction/force - it is that their attraction to the earth is counteracted in a different manner than the normal force that we suffer.

I am astonished at the polemic here.

The weight of the earth = 0 for the same reason that astronauts are weightless when orbiting the earth in a space station - THEY ARE IN FREE FALL MOTION

Now if you don't like this reality all I can suggest is to take up the matter with Sir Isaac Newton's estate.

ARE you still claiming that the earth's weight ISNT equal to zero??

Perhaps you can use your scalarisation and vectoring techniques to prove your alchemic claim?

« Last Edit: 02/12/2010 00:04:10 by Foolosophy »

#### Foolosophy

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##### How much does the Earth weigh?
« Reply #32 on: 01/12/2010 22:23:12 »
For instance, usually in very elementary physics, weight is the force exerted on a mass. The acceleration ''g'' is not zero in space. So setting g=0 for W=Mg is not exactly correct. It is true we experience weightlessness, but there is some debate as to whether this is technically correct.

The F=ma equation is in relation to an accelerating body.

The gravitational force between two bodies can be determined by Newtons law

where G is the universal gravitational constant = 6.67*10^-11 (Nm^2/kg^2)

(G is just a phyisical constant, its not the same as the "g" in F=mg - you're confusing the two)

For example, when pilots experience g forces in their planes, say 4g, it means that the force they are experiencing is 4 times that of the earths normal gravitational pull.
« Last Edit: 02/12/2010 00:05:18 by Foolosophy »

#### Foolosophy

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##### How much does the Earth weigh?
« Reply #33 on: 02/12/2010 01:20:10 »
"imatfaal" wishes to discuss the centrifugal force of a body in circular motion

(And remember the orbit of the earth around the sun isnt strictly circular - its eliptical, but what's a few focii amongst friends hey?)

#### Foolosophy

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##### How much does the Earth weigh?
« Reply #34 on: 02/12/2010 01:22:04 »
the centripetal force is a different thing again

#### Foolosophy

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##### How much does the Earth weigh?
« Reply #35 on: 02/12/2010 01:24:45 »
But most importantly though, Imatfaal needs to acknowledge the fact that the weight of the earth is equal to zero

#### QuantumClue

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##### How much does the Earth weigh?
« Reply #36 on: 02/12/2010 02:15:56 »
For instance, usually in very elementary physics, weight is the force exerted on a mass. The acceleration ''g'' is not zero in space. So setting g=0 for W=Mg is not exactly correct. It is true we experience weightlessness, but there is some debate as to whether this is technically correct.

The F=ma equation is in relation to an accelerating body.

The gravitational force between two bodies can be determined by Newtons law

where G is the universal gravitational constant = 6.67*10^-11 (Nm^2/kg^2)

(G is just a phyisical constant, its not the same as the "g" in F=mg - you're confusing the two)

For example, when pilots experience g forces in their planes, say 4g, it means that the force they are experiencing is 4 times that of the earths normal gravitational pull.

No offense, but you really do need to work on your units. Yes (a) is acceleration, but g is also an acceleration. This relationship is true. Weight W is also the dimensions of a force exerted on an object.

#### QuantumClue

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##### How much does the Earth weigh?
« Reply #37 on: 02/12/2010 02:19:10 »
Learn here:

Equations for a falling body - Wikipedia, the free encyclopediaFor example, Newton's law of universal gravitation simplifies to F = mg, ...

#### Foolosophy

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##### How much does the Earth weigh?
« Reply #38 on: 02/12/2010 02:47:17 »
Learn here:

Equations for a falling body - Wikipedia, the free encyclopediaFor example, Newton's law of universal gravitation simplifies to F = mg, ...

...are you saying that the earth is NOT weightless?

I am not saying that the earth is massless (its mass is an instrinsic property)

I am just saying that the earth is in free fall motion aroudnd the sun - so its weight is equal to zero

Similar to being weightless in a space station that is orbiting the earth in free fall motion

Weight and Mass are not equivalent

#### maffsolo

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##### How much does the Earth weigh?
« Reply #39 on: 02/12/2010 03:48:30 »
What is the difference between mass and weight?

Mass is a measure of how much matter an object has. Weight is a measure of how strongly gravity pulls on that matter. Thus if you were to travel to the moon your weight would change because the pull of gravity is weaker there than on Earth but, your mass would stay the same because you are still made up of the same amount of matter.

Answered by: A. Godbehere, High School Student, Port Perry

Imagine yourself out is space away from any gravitational field, with a bowling ball in your hands. Let it go and it just floats in front of you. Without gravity, it has no weight. Now grab it again and shake it back and forth. That resistance to being moved is inertia, and mass measures how much inertia an object has. Inertia does NOT depend on gravity.

Mass is determined only by the amount of matter contained in an object.

Any two masses exert a mutual attractive force on each other. The amount of that force is weight. A one kilogram mass on the Earth's surface results in 2.2 pounds of force between the mass and the Earth, so we say the mass weighs 2.2 pounds. That same one kilogram mass on the Moon, because of the Moon's lower mass, results in only about 1/3 pounds of mutual force.

Just remember that the weight of an object depends on where it is, while its mass stays the same.

Answered by: Paul Walorski, B.A., Part-time Physics Instructor

=============================

Ironic that weight is always referenced to a surface ground plane ...

So what ground plane is the Earth's weight   referenced to ????

I have heard the that a free fall in space still has Micro Gravity, what is meant by that?

Is it earth's gravity affect on the freefall?

http://en.wikipedia.org/wiki/Gravitational_constant

Hmmmm no mention of weight there....

« Last Edit: 02/12/2010 04:01:32 by maffsolo »

#### Foolosophy

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##### How much does the Earth weigh?
« Reply #40 on: 02/12/2010 04:01:58 »
What is the difference between mass and weight?

Mass is a measure of how much matter an object has. Weight is a measure of how strongly gravity pulls on that matter. Thus if you were to travel to the moon your weight would change because the pull of gravity is weaker there than on Earth but, your mass would stay the same because you are still made up of the same amount of matter.

Answered by: A. Godbehere, High School Student, Port Perry

Imagine yourself out is space away from any gravitational field, with a bowling ball in your hands. Let it go and it just floats in front of you. Without gravity, it has no weight. Now grab it again and shake it back and forth. That resistance to being moved is inertia, and mass measures how much inertia an object has. Inertia does NOT depend on gravity.

Mass is determined only by the amount of matter contained in an object.

Any two masses exert a mutual attractive force on each other. The amount of that force is weight. A one kilogram mass on the Earth's surface results in 2.2 pounds of force between the mass and the Earth, so we say the mass weighs 2.2 pounds. That same one kilogram mass on the Moon, because of the Moon's lower mass, results in only about 1/3 pounds of mutual force.

Just remember that the weight of an object depends on where it is, while its mass stays the same.

Answered by: Paul Walorski, B.A., Part-time Physics Instructor

=============================

Ironic that weight is always referenced to a surface ground plane ...

So what ground plane is the Earth's weight   referenced to ????

I have heard the that a free fall in space still has Micro Gravity, what is meant by that?

Is it earth's gravity affect on the freefall?

So you agree that the earth is in free fall motion around the sun and therefore its weight is equal to ZERO??

Why are astronauts weightless in space stations that are orbiting the earth?

#### maffsolo

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##### How much does the Earth weigh?
« Reply #41 on: 02/12/2010 04:28:44 »
What is the difference between mass and weight?

Mass is a measure of how much matter an object has. Weight is a measure of how strongly gravity pulls on that matter. Thus if you were to travel to the moon your weight would change because the pull of gravity is weaker there than on Earth but, your mass would stay the same because you are still made up of the same amount of matter.

Answered by: A. Godbehere, High School Student, Port Perry

Imagine yourself out is space away from any gravitational field, with a bowling ball in your hands. Let it go and it just floats in front of you. Without gravity, it has no weight. Now grab it again and shake it back and forth. That resistance to being moved is inertia, and mass measures how much inertia an object has. Inertia does NOT depend on gravity.

Mass is determined only by the amount of matter contained in an object.

Any two masses exert a mutual attractive force on each other. The amount of that force is weight. A one kilogram mass on the Earth's surface results in 2.2 pounds of force between the mass and the Earth, so we say the mass weighs 2.2 pounds. That same one kilogram mass on the Moon, because of the Moon's lower mass, results in only about 1/3 pounds of mutual force.

Just remember that the weight of an object depends on where it is, while its mass stays the same.

Answered by: Paul Walorski, B.A., Part-time Physics Instructor

=============================

Ironic that weight is always referenced to a surface ground plane ...

So what ground plane is the Earth's weight   referenced to ????

I have heard the that a free fall in space still has Micro Gravity, what is meant by that?

Is it earth's gravity affect on the freefall?

So you agree that the earth is in free fall motion around the sun and therefore its weight is equal to ZERO??

Why are astronauts weightless in space stations that are orbiting the earth?

Yea how can you weigh the earth against the earth.

I kind of like learning to staying away from the association of the words "weightless" with "freefall" in the same breath...
Reason being, it is easy to misinterpret the slang...

"There is no gravity in space."  FALSE  If there were no gravity in space, the space shuttle would not be able to orbit the Earth, the moon would not orbit the Earth, and the Earth would not orbit the Sun.  The reason we tend to think of there being no gravity in space is that we have seen movies of the astronauts being "weightless".  They aren't actually weightless, they are still being pulled down by gravity but they and the space shuttle are in a constant state of freefall around the Earth.  So they seem to be weightless as a result of the falling - just as you would seem weightless if you were in an elevator when the cable broke.

http://www.regentsprep.org/regents/physics/phys01/unigrav/default.htm

#### Foolosophy

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##### How much does the Earth weigh?
« Reply #42 on: 02/12/2010 04:39:41 »
maffsolo

what is the weight of the astronauts in the spcae stations when they are orbiting the earth in free fall motion?

They are weightless - their mass doesnt change (although strictly speaking their relativistic masss does change when compard to their rest mass - but that is neglible for the speed that they are travelling at and really a topic for another thread)

I doubt whether you can find a physicist in the world today that would dispute the fact that the earth is weightless as it orbits the sun.

I am just responding to the actual question posed in this thread - and it asks what the earth WEIGHS - not its mass.
« Last Edit: 02/12/2010 04:53:22 by Foolosophy »

#### maffsolo

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##### How much does the Earth weigh?
« Reply #43 on: 02/12/2010 04:58:42 »
maffsolo

what is the weight of the astronauts in the spcae stations when they are orbiting the earth in free fall motion?

They are weightless - their mass doesnt change (although strictly speaking their relativistic masss does change when compard to their rest mass - but that is neglible for the speed that they are travelling at and really a topic for another thread)

I doubt whether you can find a physicist in the world today that would dispute the fact that the earth is weightless as it orbits the sun.

I am just responding to the actual question posed in this thread - and the it asks what the earth WEIGHS - not its mass.

I believe you can mathmatically hypothisize a value that can represent a weight.
In saying that, I also contest that, that value has no scientific value except for saying wow thats heavy.

We can hypthetically evaluate...

We know the earths mass we know the earths gravitational acceleration.
Let's just say we like to know, if an object was the same mass of the earth and it were sitting on the surface of the earth, hypothetically speaking, how much will the object weigh?
« Last Edit: 02/12/2010 05:11:38 by maffsolo »

#### Geezer

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##### How much does the Earth weigh?
« Reply #44 on: 02/12/2010 05:02:01 »
It would certainly be quite hard to find bathroom scales that were capable of weighing it. Boots maybe?

You'd also need a really big bathroom.

#### Foolosophy

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##### How much does the Earth weigh?
« Reply #45 on: 02/12/2010 06:48:03 »
-----------------------------------------------------------------------------------------
[/quote]
We can hypthetically evaluate...

We know the earths mass we know the earths gravitational acceleration.
Let's just say we like to know, if an object was the same mass of the earth and it were sitting on the surface of the earth, hypothetically speaking, how much will the object weigh?
[/quote]
----------------------------------------------------------------------------------------------

what do you mean by the "earth's gravitational acceleration"??? g?

You can hypothecise all you wish but the question in htis thread is "how much does the earth weigh"

the answer is zero because the earth is in free fall motion around the sun

What is the weight and mass of an astronaut on a free falling space station?

What is the weight of a pilot under 4g flight conditions?

When you jump from an aeroplane with a parachute (hopefully) and you reach a terminal velocity (ie stop accelerating) your weight is equal to zero - you are experiencing weightlessness.

If you want to put another earth on top of our earth and weigh it you can - but both earths will be weightless as they hurl around the sun

I dont understand why people are disputing this in here?

Its just a definition thing

#### Geezer

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##### How much does the Earth weigh?
« Reply #46 on: 02/12/2010 07:08:40 »
Its just a definition thing

It's more fundamental than that. Mass is a property of matter. Weight is a measure of the interaction between matter.

I suppose it's possible to weigh the Earth on a sort of beam balance if you compare it with the mass of the Sun, or the Moon. For example, we might say that the Earth has a weight of x Moons. We should be able to determine the null point of the fulcrum from the Earth's Lunar wobble.
« Last Edit: 02/12/2010 07:12:51 by Geezer »

#### Foolosophy

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##### How much does the Earth weigh?
« Reply #47 on: 02/12/2010 07:36:42 »
Its just a definition thing

It's more fundamental than that. Mass is a property of matter. Weight is a measure of the interaction between matter.

I suppose it's possible to weigh the Earth on a sort of beam balance if you compare it with the mass of the Sun, or the Moon. For example, we might say that the Earth has a weight of x Moons. We should be able to determine the null point of the fulcrum from the Earth's Lunar wobble.

Its not about weighing the earth whilst its static

THe question is "what is the weight of the earth"?

Are you disputing the fact that the earth's weight is equal to zero?

#### Geezer

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##### How much does the Earth weigh?
« Reply #48 on: 02/12/2010 07:55:16 »
Its just a definition thing

It's more fundamental than that. Mass is a property of matter. Weight is a measure of the interaction between matter.

I suppose it's possible to weigh the Earth on a sort of beam balance if you compare it with the mass of the Sun, or the Moon. For example, we might say that the Earth has a weight of x Moons. We should be able to determine the null point of the fulcrum from the Earth's Lunar wobble.

Its not about weighing the earth whilst its static

THe question is "what is the weight of the earth"?

Are you disputing the fact that the earth's weight is equal to zero?

I really don't know if I'm disputing any facts or not.

Weight is a measure of gravitational attraction due to mass. The Moon and the Earth can be weighed against each other, therefore, they are not weightless. (If you can find an alternative definition for weight, you should be able to prove me wrong.)

#### Foolosophy

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##### How much does the Earth weigh?
« Reply #49 on: 02/12/2010 08:01:09 »
Its just a definition thing

It's more fundamental than that. Mass is a property of matter. Weight is a measure of the interaction between matter.

I suppose it's possible to weigh the Earth on a sort of beam balance if you compare it with the mass of the Sun, or the Moon. For example, we might say that the Earth has a weight of x Moons. We should be able to determine the null point of the fulcrum from the Earth's Lunar wobble.

Its not about weighing the earth whilst its static

THe question is "what is the weight of the earth"?

Are you disputing the fact that the earth's weight is equal to zero?

I really don't know if I'm disputing any facts or not.

Weight is a measure of gravitational attraction due to mass. The Moon and the Earth can be weighed against each other, therefore, they are not weightless. (If you can find an alternative definition for weight, you should be able to prove me wrong.)

This is incorrect reasoning (if you dont mind me being abrupt)

The moon is also in free fall motion aroudn the earth so its weight is zero also.

If you weighed yourself on earth and then on the moons surface the weight values will differ (by a factor of 6). But you are not in free fall motion when youre being weighed.

Its to do with the fact that the earth is in free fall orbit around the sun - just like a space station orbiting the earth

#### The Naked Scientists Forum

##### How much does the Earth weigh?
« Reply #49 on: 02/12/2010 08:01:09 »