A Question of gravity!!

Fellow ATS members,

Gravity is a distortion of spacetime caused by matter. In the center of mass of a body, there is no distortion, and thus gravity is 0.

Gravity at the top of a mountain is almost the same as gravity in a deep valley, because the difference in altitude is very small. You have to have a greater altitude difference in order to have less gravity between the high and the low point.

Gravity at the center of the earth isn't zero. Well, I guess it depends on which direction you are talking about. At the center of the earth, there is technically no mass if the radius being measured is zero, and therefore no gravity.

But if you magically appeared at the center of the earth, all of the mass wourd be AROUND you, and so you would have gravitational attraction being exterted on you equally in all directions.

Currently, we reside on a side of the planet, and so gravity is only directed in one direction, as far as the earth is concerned. The farther you are from the center of mass (approximating the Earth to a perfect sphere) then the weaker the gravitational force. This is also mathematically supported in that gravitational force is inversely proportional to the square of the distance between the two objects.

Assuming blindly that Mt. Everest is farther away from the center of mass of the Earth than Death Valley is, I would guess Mt. Everest.

I'm going to say they're equal.

My logic probably makes no sense though, so don't mind me. Heck, I don't even think I could accurately explain how I came to this conclusion. Just throwing something out there.

--Kit.

Some are unsure whether gravity is actually Zero at the centre of the Earth.
A simple explanation is given Dr R. Barrans Jr., Ph.D:

At the center of the earth, you would not feel any gravity. This is
because the gravitational pull from every region of the earth is exactly
counteracted by the gravitational pull from the corresponding region on the
opposite side of you. This all adds up to a great big zero.

Richard Barrans Jr., Ph.D.
Chemical Separations Group
Chemistry Division CHM/200
Argonne National Laboratory
9700 South Cass Avenue
Argonne, IL 60439
[email protected]

What the good doctor is saying is what you feel is zero. There is still an acceleration due to gravity none the less and gravity still exist, meaning it is not zero.

If all gravitational forces cancel out at the centre (ie. the earth is perfectly spherical) then dont all the acceleration vectors add up to 0 too, therefore there is no acceleration due to gravity?

Repeat after me: at the center of the Earth, gravity is 0, because spacetime is distorted equally from all directions. Gravity at the center of the earth, if measured, gives G = 0.

Originally posted by masterp
Repeat after me: at the center of the Earth, gravity is 0, because spacetime is distorted equally from all directions. Gravity at the center of the earth, if measured, gives G = 0.

How?

I can't remember where I read it, but I know it was a trustable source. It had to deal with the power of a black whole and how gravity is affected by it. It has to do with the hawkings effect, but anyway, For every mile you move away from the source of the gravitational energy, the power of the force is 1/7 that of what it was exactly 1 mile in the direction of the source. So unless the effects of gravity are different throughout the cosmos, I believe the farther away from the source you are, the weaker the gravity, therefore, the MASS of someone on everest would be less than that of someone in the dead valley.


[edit on 22-3-2006 by formoneyormind]

[edit on 22-3-2006 by formoneyormind]

According to www.newton.dep.anl.gov if you were at the very center of the Earth you would feel zero Gs.

Question - What is gravity like at the centre of the earth? If I dug
a hole through the earth and travelled to the centre would I be pulled in
both directions or float or what?

Ian
Yes, you would be pulled equally in all directions, in essence in "zero
gravity". But the temperatures in the center of the earth would melt all
known materials, you'd need some special insulating field to protect you
there. Getting there would be another issue, another question.
This is all a "what-if" journey, right?
Lou Harnisch

I don't see how this would effect your weight at Death Valley or on top of Mt Everest.

formoneyormind just like some other posters you are making a common mistake, mass stays the same whatever gravity is present, it is constant. Weight changes as it is dependant on gravity. Your MASS will be the same everywhere in the universe.

Sorry Guys,
Missed you all a lot! Had gone on a vacation and just returned. (Not to Mt Everest or Death Valley!!)

OK. I've received a lot o' U2Us for the answer. It's quite simple really.
So here goes....Have a nice day!!

curious.astro.cornell.edu...

Wow ...very interesting ... but I still have trouble understanding this...ok equal gravitational force from all directions at center...gotcha..so about wieght....you would be weightless..gotcha...but that means that the forces from all sides have no effect..such as crushing you to the size of a pin due to the enormous preassure? And increasing your wieght...this has nothing to do with math ... I have a very limited grasp of mathmatics...but from a logical standpoint does this make sense to anyone ? and could you explain to me how it doesnt without the use of complex mathmatics....

You'll weigh the same. Weight (or "mass") doesn't change simply because you're nearer or farther away from a gravity source.

YOU FOOLS, YOU!!

Originally posted by Enkidu
You'll weigh the same.

Nope.

Weight equals mass times gravitational acceleration.
As mentioned already a few posts earlier.
Your mass will stay the same, but in the center of the earth the effective gravitational acceleration is 0, so you'll be "weightless".

Step on a scale on the moon and the weight of your 80 kilo's of mass will be less than 80.

Originally posted by Enkidu
You'll weigh the same. Weight (or "mass") doesn't change simply because you're nearer or farther away from a gravity source.

YOU FOOLS, YOU!!

OK this is the third time i have said this in this thread..... Mass and Weight are two totally different values, anyone with basic scientific education knows this. Surely the only fools are the people who firstly make posts without reading the thread first and secondly make condesending posts based on incorrect and flawed knowledge.

-George

Originally posted by gfad

Originally posted by Enkidu
You'll weigh the same. Weight (or "mass") doesn't change simply because you're nearer or farther away from a gravity source.

YOU FOOLS, YOU!!

OK this is the third time i have said this in this thread..... Mass and Weight are two totally different values, anyone with basic scientific education knows this. Surely the only fools are the people who firstly make posts without reading the thread first and secondly make condesending posts based on incorrect and flawed knowledge.

-George

Yeah, would people quit acting like know-it-alls! Please! This is a very serious and complicated problem and deserves our utmost concentration and seriousity.

lol, damn, he came back too soon and answered it... I only just saw the thread.

Yeah, gravity at the center of the earth is measured as 0. However, whats actually happening is you are being forced in all directions with equal force.

Its like two identical cars playing tug of war... theyre not getting anywhere... neither is the guy sitting on the middle of the rope.

Originally posted by Enkidu
You'll weigh the same. Weight (or "mass") doesn't change simply because you're nearer or farther away from a gravity source.

YOU FOOLS, YOU!!

Fool 42 here...

uhhh, I think I'm going to have to ask you to come in and work on Saturday, because it appears you're not getting basic physics Monday thru Friday.

The force (that's your weight) is equal to the gravitational constant times your mass times the other mass (that would be whatever you're on or near at the time) divided by the distance between you and it's center squared.

W = G*mass(you)*mass(planet, moon or whatever)/(d^2)

So, no you don't have the same weight everywhere...you have the same mass (unless you start approaching the speed of light - but that lesson doesn't come until next Sunday - which you'll have to fill out a TCP report first before you can get into that one).

Originally posted by Valhall
The force (that's your weight) is equal to the gravitational constant times your mass times the other mass (that would be whatever you're on or near at the time) divided by the distance between you and it's center squared.

W = G*mass(you)*mass(planet, moon or whatever)/(d^2)

Does this apply to a black hole?

If the mass is that of 1,000,000,000 of our suns, and I weigh 200 pounds. How much would I weigh in a black hole?