Why does the earth have to have gravity?

Answer 1

It has gravity because its mass is so huge until it curves the space time fabrics around it so much until this curvature creates what today we call gravity. - we are actually falling continuesly due to this earths caused curvature of the space time fabrics - there is nothing pushing us down or pulling us down.

Thats explained by Einstein in his theory of general relativity.

OK I will explain to you this effect in plain simple English using analogies.
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Go to a lake

throw a huge carpet on the water of the lake - so that the carpet float on top of the water.

now

throw some iron ball bearing on to the surface of this carpet.

hence this ball bearings will be scattered all aver the carpet.

now take a big and heavier ball bearing and slowly place it on top middle part of the floating carpet.

What will happen

The big ball bearing on the middle of the floating carpet will cause the floating carpets to bent and dent as the ball bearing in the middle will be in the hallow part due to its mass.

SO WHAT WILL HAPPEN

automatically the other smaller ball bearing will roll towards the big ball bearing in the middle due to the dent bent curvature of the floating carpet.

You can say that it looks like the big ball bearing is PULLING the other ball bearings towards it or something call force is pushing them towards the bigger ball.

But the actual reason is - its the carpet's fabric curvature that makes all the ball bearing to fall towards the bigger ball bearing. (this curvature on the carpet fabric is caused by the mass of the big ball bearing )

SAME CASE IS WITH OUR GRAVITY THE - THE EARTHS MEGA-HUGE MASS MAKE's THE SPACE TIME FABRIC CURVATURE AS SUCH THAT WE ALL FALL TOWARDS THE BIG EARTH.

http://www.itwire.com/content/view/11350/1066/

http://einstein.stanford.edu/

Answer 2

Nicely said Linkin Park , you pointed out correctly on the facts of how Gravity exist.

Well I would like to do some explanations as well. Getting more specific from your general apprehensions on what or why and how earth has gravity- the strength of Gravity depends at the mass of the planet.

Why ?

here it goes.......

An atom consists of a dense atomic nucleus of positively-charged protons and electrically-neutral neutrons, surrounded by a much larger electron cloud consisting of negatively-charged electron.

The dense atomic nuclei is the one that creates the MASS of an atom

the atom dense nuclei is like an energy gyroscope for creating various forces - eg: electromagnetism , magnetism ...and so

When more than one atoms bond together thus the total mass and forces created by this combined group of atoms are far far greater then a single atom.


molecules are made of thousand or millions of atoms , substances are made from billions or trillions of molecules and much of the substances with different configurations form or create many components and final components are assimilated to create things - everything.

how much atoms does a thing has - thus how much mass does that thing has and therefore how much forces does this thing can create

ok....now how much thing is in out earth and thus how much atom is in our earth if it is assumed as one big thing with xxx............................................................. amount of atoms - what are the forces created by this atoms as a whole group and what is the mass of this group --- this is the force that makes a dent in the space time fabric by curving it.

and the space time curvature creates the phenomena of falling call gravity.

edit:
obviously if a planet has more mass which means it has more atoms that means the forces created by these atoms as a whole group is also more - and thus more space time is curved making the gravitational effects more obvious.

Answer 3

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Technicaly, the earth does not have to have gravity. If the laws of physics were differant it might not and we would not be here. Boy are we luckey!
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The question is:
What causes gravity?
Not how much is there, why God made gravity or is gravity relative to mass.

Gravity is relative to mass? That tells us nothing about causation because what causes mass is also un known at this time. The answer is unknown at this time.
A unifying theory has eluded the physics community for centuries. String theorists then they are close, I do not.
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Linkin park - Good answer. I hope physicists can prove it correct some day with a unifying theory.
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The answer is un known at this time.

Deep question. So far as I know the force of gravity
is something that is observed, but nobody can say what the
cause is. In other words, it is observed that by postulating
a force of gravity, we can explain the attraction of different
objects to one another and can compute orbits of the planets,
satellites, etc.

Gravitational force is proportional to the masses of the two objects that are attracting each other, so that an object with twice the mass will attract with twice the force. The gravitational force also falls off as the square of the distance, so that an object that is twice as far away will attract with four
times less force. These are postulations that Isaac Newton
made which allowed him to accurately predict the movements
of the planets and other physical phenomena, but is not
an explanation for the cause of gravity.


Nicolas Fatio and the Cause of Gravity
In an unpublished treatise called “On the Cause of Gravity”, which Fatio composed around 1690, he wrote that, despite the apparent heaviness of gold, it is entirely possible that a quantity of gold contains a trillion (1012) times more void than substance. In support of this, he notes that water and glass are dense materials, and yet they are almost totally transparent to the passage of light. By the same token, he argued, it is conceivable that all solid objects, even those that are opaque to light, could allow almost free passage to sufficiently small particles.

Answer 4

Because the Earth has mass. Any object that has mass will also have gravity. The relationship of mass to gravity is proportional. The smaller the mass, the less gravity.

Answer 5

Because gravity is a result of mass and the earth just so happens to be a very large mass

Answer 6

Because when the earth was created, there was nothing but stars and debris floating around in the universe. There was a giant collision, where all these rocks and stars collided, and form the core of the earth. Since there were metallic charge, and opposite charge attract, there was gravity. That is the scientific response, or you can go with the classic, god made it

Answer 7

Because all objects have gravity. It's just that the Earth is so big that we actually notice.

Answer 8

Gravity is proportional to mass, and inverse square
proportional to distance from the center of the mass.

Answer 9

Divachick, we made it all for you, baby. We didn't want you floating in space.

Actually, all mass has gravity. It comes with the turf.

Answer 10

Because it has mass, anything with mass has a gravitational attraction, this applies even to a grain of sand.