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What are Gravitational Fields?

Updated on March 18, 2013

I shall try to put this as plainly as I can, with as little reliance on scientific words as possible. Please feel free to mention in the comments if I have diverted into gobbledegook and you would like a better description of this in easier to understand English!

Anyway, simply speaking, gravity is the strength or energy that acts between two bodies with mass. The greater the mass and the closer the distance between the objects, the greater the energy between them, and the gravitational field is the area over which that energy is felt.

OK, so that is the bare bones, let’s look into this in a bit more depth.

Gravity is a force of attraction (it never repels anything, only attracts – how personable is that!?) between all things with a mass. You can’t feel the attraction from a table if you were sitting near it because it is very small. However, you can feel the attraction that the earth has on you and other objects around you because otherwise you would fall off into space. This is because our planet is very large in comparison to the table and so the pull is also therefore bigger.

On earth, this force causes objects with mass to accelerate towards it at a constant 9.8m/s2. So this means that any object that is dropped from a decent enough height (if it is too close to the ground it won’t have time to reach 9.8m/s2) will have the same acceleration, whatever the shape or size of the object.

Now strictly speaking, this would be true if we had no atmosphere around the planet, but as we have, we do have to take air resistance into the equation. You would see that a feather would have more air resistance than a steel ball for instance, and as such would take longer to reach the ground. But this is due to the air resistance not to a difference in the gravity itself.

Gravity also is how planets keep their orbits. In our solar system, the planets are attracted to the sun, but are in motion around it. The attraction and the movement balance each other out to enable the planets to continue moving around and around. The same is true of the moon orbiting the earth. They both have a pull on each other, the moon to a lesser extent of course as it is smaller, but with enough forward motion it keeps to the same orbit day after day.

The closer objects are, the greater the pull between them. This means that those planets closer to the sun will have to have more forward motion, i.e. move faster, to counteract the greater pull that the sun is having on them.

Danilo Rizzuti
Danilo Rizzuti

So, in conclusion, the gravitational field of any object is the area around that object that is exerting that attraction. So, for the earth, the field would be the area around it where if something were dropped, it would still fall to the ground, not fly out into space. The gravitational field at any point in space is the pull felt by a mass placed at that point. If you are measuring this though, the mass itself must be small enough not to cause its own distortion of the gravitational force or we will get into a real mix up!

The real science behind this is Newton’s law of universal gravitation which states that every point mass in the universe attracts every other point mass with a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between them. In reality this means that for 2 objects A and B, the gravitational force is proportional to the mass of A multiplied by the mass of B divided by the square of the distance between them.

If the gravitational force is F the mass of A is ma the mass of B is mb the distance between them is r and the gravitational constant is G

Then the equation would look something like this F = G x ma x mb r2

And hopefully this has explained things a little more. Please feel free to comment if there is anything else you would like to know more about.


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    • joer4x4 profile image

      joer4x4 5 years ago from Philadelphia, PA

      "Now let's discuss some facts related to gravity and relativity"

      Unfortunately, there are no facts related to gravity. It has never been proven or recreated in the lab or otherwise. It is "assumed" to exist. Since this statement is true I would submit all related theories are suspect and illogical. After all science has had well over 200 years to prove it as correct.

      Time is another thing that can not be recreated in the lab. One perceives time when awake, but one also fails perceive time throughout the day and when sleeping. These facts are not taken into consideration. It is "assumed" time is a constant and is an element of its own but it is only a perception that allows us to view our world in sequential events.

      If time and gravity were related I think you would experience it. Astronauts experience the same time in space as they do on earth.

      If an astronaut is on the moon is time trapped on the moon? When the astronaut leaves the moon is time still trapped with no one there to experience it? Does the moon experience time?

      In any case, should we establish a base on moon or mars where the gravity is much less than earth, and if people will live there should we expect those people to much live shorter lives? It doesn't seem to be an issue to science. Considering the so called "gravity" vs. time, it seems logical that sending people to the planets for extended period is not a good idea. Of course if the theory is true.

      You can only experience the present moment. One can not experience the future for when one does it is the present moment. One can not re-experience what we call the past. The past is not an event, it is a memory. If it were an event then we could go there.

      "One more thing some people say that root of plants are gravity sensors because it always goes down no matter how it is planted ...Do you believe this?"

      If that were true, wouldn't the roots grow out of the dirt and pot when they are grown upside down? Wouldn't the plant eventually fall out of its pot?

      The intelligence, consciousness, or DNA (whatever term suits you) within the plant seeks to plant its roots in a food source which is usually in the down direction. While the direction is down ward does the plant experience direction like we do?

    • vivek777 profile image

      Vivek Kr.Gupta 5 years ago from punjab india

      Thanks Mr. joer4x4 for giving me such a vast explanation on gravity.

      I also agree with your theory of electricity.Now let's discuss some facts related to gravity and relativity.It is said that gravity is responsible for trapping time on earth or any other planet,stronger the gravitational force slower the time passes and weaker the gravitational force faster the time passes.Do you think time is related to gravity?

      One more thing some people say that root of plants are gravity sensors because it always goes down no matter how it is planted ...Do you believe this? Well

    • joer4x4 profile image

      joer4x4 5 years ago from Philadelphia, PA

      Science has never found gravity within the atom. So if you use the atoms to build a universe the universe would take on the properties of the atom.

      This is reasonalble. If you build a wall out of brick and mortar, the wall will have those properties.

      If someone came along and said the wall may have brick and mortar properties but it was made from wood but never showed you how or why, would you believe it? Further more could they prove it?

      This what main stream science does today.

      When you are standing on the floor the molocules of you feet touch the molocules of the floor. This way you don't go through the floor. If there was only gravity, you would be crushed under your own weight. But science has come up with other forces to expain why you are not crushed.

      The atom is mostly space and acts somewhat like the solar system with electrons whizzing around the nucleus. The electrons stay in their correct orbit due to electromagnetic force. No scientist has ever claimed to find gravity in the atom (that I am aware of). Each neutron, proton, and electon have their own electrical and magnetic properies that keep the atom's structure consistant.

      At the time of Newton's work he did not know of the atom and its electromagnet properties. He called what he observed gravity and assumed it was so.

      If one works out diffferent scenerios using both gravity vs electomagnetic force, electromagnetic force has a far greater effect.

      Now, this thing with gravity after Newton worked it out took off in the scientific community because that's all they had to go on. So it grew and was accepted as fact to the present day. But it has never gone through the full scientific method of 1 - observe, 2-collect data, 3-build a theory, and 4-(most important) disprove the theory.

      No one in main stream science has tried to disprove it nor have they been able to create gravity in the lab.

      If science admitted gravity did not exit, most cosmologic and physical laws created by science would have to be scapped including the work of Einstein.

      Another tell tale sign is when scientist try to use gravity to explain something they have to revert to other theories like thermodynamics. This is because gravity cannot expain what is observed. That is gravitational theory can not stand on its own.

      For instance, a black hole's gravity is so severe that nothing not even light can escape. We are also told every galaxy has a black hole in its center. Yet when science observes some galaxies, bight jets of material are shooting out of the center for light years.

      How is it possible this can happen if there are black holes and gravity? Under circumstances stated by scientist - it is impossble. Yet they forge ahead and create more theory to keep the black hole and gravity in place. And yet they never try to disprove these theories.

      If one looks at other theories, the same hold true. The only theory that I know that can stand 100% on its own is the theory of Electricity. It is predicable, works accurately, needs no other theories to expain what is observed, and has been lab proven. But science had to get this right if they were going to use it.

      Obviously we are not going to use black holes any time soon.

      It really is commom sense if you think about it and you only need the information they feed you. But you do have to constantly recall what you are taught to put it together. Unfortunnately, they teach this in school as fact desipte the fact that the small piece doesn't fit in the big piece.

      The electomagnetic force thing works for me and makes sense.

    • vivek777 profile image

      Vivek Kr.Gupta 5 years ago from punjab india

      @joer4x4 if gravity does not exist in atoms then what causes us to stand and move on earth is it electromagnetic force.Then why is gravity always act as attractive and electomagnetic force is repulsive as well as attractive

    • writerbeth profile image

      writerbeth 5 years ago from England

      Excellent comment, thanks, and of course you are right, the effect of gravity is arrived at because of a few assumptions.

      However, science has traditionally based thought processes and derivations on assumptions only for them to be either proved true when more advanced knowledge catches up with these suppositions or thrown out and new theories put in their place.

      As far as gravity is concerned, scientists can describe gravity in amazing detail but exactly what it is is another matter. I am aware of this inconsistency but as science at the moment (and indeed NASA as you say) stands by gravity as a real force, then I am just trying to explain it for those that are interested in understanding science's current view.

      Hope that's OK as I'm afraid my physics degree sadly doesn't imbue me with any "Stephen Hawking"-like intelligence to be able to take this further! Doh! Thanks, Beth

    • joer4x4 profile image

      joer4x4 5 years ago from Philadelphia, PA

      G = m1 m1/d2 (where 2 is the square) pretty much negates the effect of gravity if it exist at all.

      Electromagnetic force has a far greater impact on objects.

      The universe is built on the atom and there is no gravity in the atom. Only electromagnetic force.

      How can gravity possibly exist if it is nonexistent within the atom, the building block of the universe?

      Of course Newton did not know this - but established science refuses to acknowledge this yet admit atoms are bound by electromagnetic force.

      Even NASA admits the measurement of gravity is based on assumptions and not real world facts or observations which is against scientific principle.. Science can not create gravity in the lab and never will.

    • writerbeth profile image

      writerbeth 5 years ago from England

      Thanks for your question vivek777. My use of the word pull was to indicate that the gravity of a large object attracts other objects to it, rather than pushes them away but strictly speaking I don't think anyone knows if it is a 'pull' towards or a 'push' towards that large object. For instance, on earth are you being pulled down onto the surface or pushed down?

      Does this help?Hopefully I haven't made things more confusing!?

    • Zualtea profile image

      Lawmsangzuala 5 years ago from Sihphir, Mizoram, India

      I think... it is the area where gravitational force can be experienced.

    • vivek777 profile image

      Vivek Kr.Gupta 5 years ago from punjab india

      Can u explain why gravity pulls.....why not it pushes


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