Why earth has gravity

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All mass has gravity, the Earth, the Sun, you, your PC, all have mass and all have a gravitational field and all attract one another.

It's an intrinsic property of matter.

Of course, it's incredibly weak which is why you're not pulled towards your PC. It's so weak that it might be hard for you to believe me that everything is attracted towards each other.

Have a look at Cavendish's experiment, performed 200 years ago: Cavendish experiment - Wikipedia, the free encyclopedia

It's a notoriously innaccurate experiment but he managed to show that some huge steel balls attracted each other gravitationally.

The earth has gravity because of the molten iron in its core... the molten metals produe magnetic field and you get gravity!

Mahima, the magnetic field produced by the core doesn't produce gravity. However the mass of the earths core does increase its gravity. If there was less mass there would be less gravitational pull.