Here's why:

* Gravity's Strength: Gravitational force depends on mass and distance. The Earth has a massive amount of mass, and you're sitting on its surface, so the gravitational pull is very strong.

* The Computer's Mass: While your computer has mass, it's minuscule compared to the Earth. Even if you were sitting right next to the computer's core, the Earth's gravitational pull would be much stronger.

* Other Factors: Other objects like the Sun and Moon also exert a gravitational pull on you, but their influence is much weaker due to their distance.

Let me know if you have more physics questions!