The appearance of Gravity

Actually it masures zero because there is zero acceleration.

The approaching earth disagrees.

I'm sorry for bumping an old topic, but I found this one to be interesting.

It seems that both sides have some confusion on gravity and acceleration.

The current formula for gravity is:
F=(GMm)/(r^2)

F is the force of gravity.
G is the universal gravity constant (~6.67x10^-11)
M is the mass of the first object
m is the mass of the second object
r is the distance between the first and second object

The force between the two masses is the same for both. When I am in free fall (such as in the chair example) I am pulling the earth toward me because I exert a gravitational force on the earth. Likewise, the earth is pulling me toward it because it exerts a gravitational force on me. Both me and the earth accelerate. My acceleration is much higher though, around 9.8m/s^2. The earth's acceleration is very small in comparison. This is because the earth is around 4x10^22 times more massive than I am.

Quote from: LiceFarm on January 28, 2010, 10:33:54 AM

Quote from: Tom Bishop on January 27, 2010, 11:26:54 AM

When you stand on the earth's surface your guts are being pinned to the surface as the earth accelerates your body upwards.

Quote from: LiceFarm on January 27, 2010, 03:41:35 AM

LOLWUT?! My guts were never pinned to the earths surface.

An accelerometer measures zero because all parts of the accelerometer are being accelerated at the same rate.

lrn2tooluse.

Actually it masures zero because there is zero acceleration.

Okay Tom, by your logic, if we put an an accelerometer on the ground, make and observer stand near it and then throw a person of the roof of a very High building besides the accelerometer than will the accelerometer give any reading?

Also, Malleo is correct. Earth does have some accelration intheory but practiclly it is negligible in comarison to that of the man that falls.

What these FETs people are saying here that all scientists and Engineers from Galileo and Newton to Stephen Hawking how believe(d) on the basis of Scientifc thought and rational logic and empirical activites that the Earth is round  and all Scientific organisations that believe the same and all scinetific researches that PROVED that the Earth is round are either:

a.) Wrong.
b.) Consipring and corrupted.
C.) Both.

I'm sorry for bumping an old topic, but I found this one to be interesting.

It seems that both sides have some confusion on gravity and acceleration.

The current formula for gravity is:
F=(GMm)/(r^2)

F is the force of gravity.
G is the universal gravity constant (~6.67x10^-11)
M is the mass of the first object
m is the mass of the second object
r is the distance between the first and second object

The force between the two masses is the same for both. When I am in free fall (such as in the chair example) I am pulling the earth toward me because I exert a gravitational force on the earth. Likewise, the earth is pulling me toward it because it exerts a gravitational force on me. Both me and the earth accelerate. My acceleration is much higher though, around 9.8m/s^2. The earth's acceleration is very small in comparison. This is because the earth is around 4x10^22 times more massive than I am.

Sorry to say, but that equation isn't very current. There is a much newer theory called General Relativity, in which gravity is a psuedo-force (still a real force, it hurts) that exists due to acceleration in curved space.

The equation you posted is a very good approximation to GR when traveling much slower than the speed of light, and so is very useful. However for the purposes of this thread the precise and detailed definition of gravity is at question, beyond what is generally useful or well understood.

In our frame of reference we are moving much slower than the speed of light. Therefore this equation should be an adequate approximation.

In our frame of reference we are moving much slower than the speed of light. Therefore this equation should be an adequate approximation.

No, it should not. The background metric needs to be Galilean in the FoR where Newton's Law of Gravitations is a good apporximation. This is clearly not the case.

now, now children, no one like a non-locally flat spacetime

um ondupe, i have the solution for you, and it wont be as painful as falling of your chair, no because i care about what you are saying i only read your first post and then only the first page of responses because i know that these things get derailed easily if there is a tricky question, the logic can still be applied easily, you just dont know how to. ok lay on your back and look into the sky (change the perspecitive) and let something fall onto you, from this you can not tell that the ball is falling, only that it hits oyu in the face (if you where always on your back you would think you are thrusted into it), although this does not favour one side or the other it is the answer to your question, the logic can be applied. now for a little bit of derailing. round earthers have a very bad problem of not being able to see things from another point of view, and are unable to chanegthere perspective, traits like this lead to misundertanding and things like war, racism, hatred etc, no wonder all these things exist on a 'round earth'. good on you, your making this world a better place.

... Yes, because CF, you are so open minded when it comes to perspective.

Can we PLEASE get an educated person who is a Flat Earther in on this ?

No more pseudo scientific theories. I feel like I'm reading a New Age web page on Aura Photography, using Kirlian technique, and how it is proof of ones destiny on Earth ( I wonder if that changes if it's a Flat Earth ! different laws of physics and all... it must become influenced...)

Yeah, bring it on, flat guys. 

All ive got to say to this is magnets.

Quote from: Thermal Detonator on December 05, 2009, 05:30:42 AM

Yeah, bring it on, flat guys. 

All ive got to say to this is magnets.

 

Quote from: zarth on April 19, 2010, 02:37:01 PM

Quote from: Thermal Detonator on December 05, 2009, 05:30:42 AM

Yeah, bring it on, flat guys. 

All ive got to say to this is magnets.

 

It's quite a straightforward statement. How could you not understand?

Quote from: Roundy the Truthinessist on April 19, 2010, 05:22:29 PM

Quote from: zarth on April 19, 2010, 02:37:01 PM

Quote from: Thermal Detonator on December 05, 2009, 05:30:42 AM

Yeah, bring it on, flat guys. 

All ive got to say to this is magnets.

 

It's quite a straightforward statement. How could you not understand?

My mistake, I just realized you're right.  You really showed us, zarth!

I'm sorry for bumping an old topic, but I found this one to be interesting.

It seems that both sides have some confusion on gravity and acceleration.

The current formula for gravity is:
F=(GMm)/(r^2)

F is the force of gravity.
G is the universal gravity constant (~6.67x10^-11)
M is the mass of the first object
m is the mass of the second object
r is the distance between the first and second object

The force between the two masses is the same for both. When I am in free fall (such as in the chair example) I am pulling the earth toward me because I exert a gravitational force on the earth. Likewise, the earth is pulling me toward it because it exerts a gravitational force on me. Both me and the earth accelerate. My acceleration is much higher though, around 9.8m/s^2. The earth's acceleration is very small in comparison. This is because the earth is around 4x10^22 times more massive than I am.

Good start.  From this gravitational force, we can determine (you did, I'll show it) the acceleration.  I'll use the same variables as you did.

Newton's second law:

F = m*a  therefore F / m = a

The mass is indirectly proportional to the acceleration, so the Earth has less acceleration because of its greater mass.

Sorry to say, but that equation isn't very current. There is a much newer theory called General Relativity, in which gravity is a psuedo-force (still a real force, it hurts) that exists due to acceleration in curved space.

The equation you posted is a very good approximation to GR when traveling much slower than the speed of light, and so is very useful. However for the purposes of this thread the precise and detailed definition of gravity is at question, beyond what is generally useful or well understood.

Must we know the genetic makeup of a bull to do bullfighting?  No.

And no, to the best of my knowledge gravity is still a force (at least in the standard model).  I would assume (based on the fact I am assuming we can say I'm not confident on this) that it was considered a force by Einstein as well.

All ive got to say to this is magnets.

Let me save you guys a lot of trouble.  In our every day life, we are used to absolute references, like our four walls.  There are none in relativity.  Newton was a big fan of absolute references, and absolute velocity, but he obviously needed to get his consciousness raised.

IMO Flat Earthers could use a bit of consciousness-raising themselves.  It's the only way man progresses.

Quote from: Ondupe on December 05, 2009, 12:56:57 PM

Stand in from of your chair (a large comfy chair), rock backwards and fall into the chair, then tell me that experience tells us the chair has sped up towards you and slapped you on the arse.

What we experience is the chair hitting us. We don't put our bodies in motion when we fall. When we go into free fall we are inert and motionless. We are not propelling ourselves.

The earth propels itself into us.

No we are being pushed towards the centre of the earth by gravity, the earth does not propel itself towards you when we fall, well unless you way more then the earth and the earth orbits you

weigh

Quote from: Tom Bishop on December 05, 2009, 03:47:33 PM

Quote from: Ondupe on December 05, 2009, 12:56:57 PM

Stand in from of your chair (a large comfy chair), rock backwards and fall into the chair, then tell me that experience tells us the chair has sped up towards you and slapped you on the arse.

What we experience is the chair hitting us. We don't put our bodies in motion when we fall. When we go into free fall we are inert and motionless. We are not propelling ourselves.

The earth propels itself into us.

No we are being pushed towards the centre of the earth by gravity, the earth does not propel itself towards you when we fall, well unless you way more then the earth and the earth orbits you

Actually I think that your mass exerts some force on the earth.

weigh

Tom,
Best one word response ever.  I had to read above to find out exactly why you would post "weigh", but it was well worth it.

No we are being pushed towards the centre of the earth by gravity, the earth does not propel itself towards you when we fall

Both situations are equivalent from your reference frame.

And no, to the best of my knowledge gravity is still a force (at least in the standard model).

Gravity is a fictitious force or manifestation of inertia experienced by an accelerating observer.

it was considered a force by Einstein as well.

This is not true, according to his very own theory of General Relativity. Here is a small part of the theory..

Einstein defined gravity as a distortion in spacetime interacting at light speed rather than as an instantaneous force (action-at-a-distance). He realized that a resting observer under the force of gravity and an accelerating observer under no force of gravity will experience the same effects. Since we are constantly pushed by the Earth's mechanical resistance, we are accelerating and thus he concluded that gravity as a force cannot be real.

'Fictitious force' is one of the worst piece of nomenclature in the history of science.

http://xkcd.com/123/

I'd argue theres a limit to how ficitious anything that can kill you is. Infact i'd say a good way to tell the difference between a real gun and a fictitious gun is whether it can kill you. I used to write INERTIAL in huge letters over anyone in my tutor group who'd dare hand in anything saying fictitious force. Either that or get them to drive fast into a wall without a seat belt on and then ask just how ficitious the break in their ribs were. Considering how many people per year die in car crashes I can't think of any nomenclature as manifestly adsurd as fictitious force. Right i'm done.

guys, just look at how magnets work, they use MAGNETIC  energy to pull them selves together. I dont think im seeing the magnets fall towards eachother. aspeshaly when im holding them side by side.

the earth's core is just one massive magnet, and it so powerful, it's able to pull everything around it towwards it.


just think of that little magnet of yours (assuming you have one that is) as a mini planet core.

guys, just look at how magnets work, they use MAGNETIC  energy to pull them selves together. I dont think im seeing the magnets fall towards eachother. aspeshaly when im holding them side by side.

the earth's core is just one massive magnet, and it so powerful, it's able to pull everything around it towwards it.


just think of that little magnet of yours (assuming you have one that is) as a mini planet core.

Is that what you think gravity is?

Quote from: zarth on April 20, 2010, 06:48:26 PM

guys, just look at how magnets work, they use MAGNETIC  energy to pull them selves together. I dont think im seeing the magnets fall towards eachother. aspeshaly when im holding them side by side.

the earth's core is just one massive magnet, and it so powerful, it's able to pull everything around it towwards it.


just think of that little magnet of yours (assuming you have one that is) as a mini planet core.

Is that what you think gravity is?

GTFO if you can't understand simply gravity, RtT you n00b. It's really quite simple to understand the earth being a giant magnet pulling everything towards the centre.

GTFO if you can't understand simply gravity, RtT you n00b. It's really quite simple to understand the earth being a giant magnet pulling everything towards the centre.

That's not the case, since free-fall is an inertial motion and free-falling observers do experience weightlessness. In RE, objects aren't pulled by the Earth's gravitational force. Instead, they merely follow the straight lines (geodesics) in distorted space-time created by the Earth's presence. I highly recommend you to look up General Relativity; it's a great theory.

Quote from: zarth on April 20, 2010, 06:48:26 PM

guys, just look at how magnets work, they use MAGNETIC  energy to pull them selves together. I dont think im seeing the magnets fall towards eachother. aspeshaly when im holding them side by side.

the earth's core is just one massive magnet, and it so powerful, it's able to pull everything around it towwards it.


just think of that little magnet of yours (assuming you have one that is) as a mini planet core.

Is that what you think gravity is?

I bolded my favorite part. 

It shows that the post was edited.  What could have possibly been more incoherent than what is in there now to warrant going back to edit?

Just to clarify, the FET position with respect to what moves relative to what when an object "falls" is that the earth moves upwards to the object?

If that is the case then, how does the earth know when to move and how much to move by?

At any single moment in the world there are plenty of objects falling from different heights. So how can the earth move 1.5m for one guy but 2m for another guy?

How does my hair (which is held slightly up due to static electricity) stay stationary when I stand next to a guy who falls of a chair? The earth is moving the 1 meter for him, yet my hair stayed stationary. Surely if the earth moved for him my hair would have moved downwards? My hair did not accelearte relative to the earth, yet he did? Why is this occuring if the earth is moving?

AHve you provided any proof to this claim?

Quote from: Sir Rhetor on April 19, 2010, 07:38:28 PM

it was considered a force by Einstein as well.

This is not true, according to his very own theory of General Relativity. Here is a small part of the theory..

Einstein defined gravity as a distortion in spacetime interacting at light speed rather than as an instantaneous force (action-at-a-distance). He realized that a resting observer under the force of gravity and an accelerating observer under no force of gravity will experience the same effects. Since we are constantly pushed by the Earth's mechanical resistance, we are accelerating and thus he concluded that gravity as a force cannot be real.

[citation needed]

So, according to your logic, all forces must act instantaneously?  Newton thought gravity was instantaneous, Einstein did not.  Does this make it not a force?

And it is a phenomena of the property of having mass that bends space.  This is why there is a gravity well here on Earth; it is very hard to escape.  I also believe that light can also bend space but I don't understand that as well.

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

[citation needed]

That was my summary; I wrote that as a small introduction to General Relativity.

So, according to your logic, all forces must act instantaneously?

I was referring to Newton's action-at-a-distance concept. His theory revolves around the instantaneous interaction of the gravitational force.

By the way, do forces have a finite speed?

Newton thought gravity was instantaneous, Einstein did not. Does this make it not a force?

Yes. If we are talking about the RE universe, then gravity is either a force that acts instantaneously or a space-time distortion that acts at the velocity of light. Here is a video that shows why the former is not plausible: http://www.youtube.com/watch?gl=US&hl=hi&v=0rocNtnD-yI

In addition to this theory that objects stay still and the earth moves towards them, I would like to query the role that drag plays in the movement of objects through air.

Drag is a function of the objects velocity relative to the air around it. Hence, if an object is dropped, the speed at which it falls is slowed by the effect of drag.

In the FET theory the object is not moving, hence it has no velocity and therefore will have no drag. Therefore all objects that are dropped should fall at the exact same rate.

However the observed situation is that by deploying a parachute when you exit an aircraft, will create sufficient drag to slow you down such that you impact the earth at a safe velocity. The individual effectively accelarates to earth at less than 9.8m/s^2.

Your theory implies when a person exits an aircraft they remain inert and the earth moves up towards them at 9.8m/s^2. Since he is motionless, he has no velocity therefore no drag therefore his accelaration relative to the earth is 9.8m/s^2. The person will therefore impact the earth at a high velocity and will die.

The observed situation does not agree with your theory. Your theory is therefore wrong and should be revised.

In addition to this theory that objects stay still and the earth moves towards them, I would like to query the role that drag plays in the movement of objects through air.

Drag is a function of the objects velocity relative to the air around it. Hence, if an object is dropped, the speed at which it falls is slowed by the effect of drag.
In the FET theory the object is not moving, hence it has no velocity and therefore will have no drag. Therefore all objects that are dropped should fall at the exact same rate.

However the observed situation is that by deploying a parachute when you exit an aircraft, will create sufficient drag to slow you down such that you impact the earth at a safe velocity. The individual effectively accelarates to earth at less than 9.8m/s^2.

Your theory implies when a person exits an aircraft they remain inert and the earth moves up towards them at 9.8m/s^2. Since he is motionless, he has no velocity therefore no drag therefore his accelaration relative to the earth is 9.8m/s^2. The person will therefore impact the earth at a high velocity and will die.

The observed situation does not agree with your theory. Your theory is therefore wrong and should be revised.

I bolded the key part for you.  If all that matters is the relative velocity between the two, then why would you expect a different result from a stationary object (relative to the earth) with a wind velocity of 5 units vs an object moving at 5 units with no wind velocity?

Just to clarify, the FET position with respect to what moves relative to what when an object "falls" is that the earth moves upwards to the object?

If that is the case then, how does the earth know when to move and how much to move by?

At any single moment in the world there are plenty of objects falling from different heights. So how can the earth move 1.5m for one guy but 2m for another guy?

How would all of the objects know how much to move by if they were the ones falling?