Here's why:
* Newton's Law of Universal Gravitation: This law states that every particle of matter in the universe attracts every other particle with a force that is proportional to the product of their masses and inversely proportional to the square of the distance between their centers.
* Mass of Earth and Mars: Both Earth and Mars have significant mass.
* Distance: While the distance between Earth and Mars varies, they are still close enough for their gravitational forces to influence each other.
However, the gravitational force between Earth and Mars is extremely weak compared to their own self-gravity. The reason for this is that the distance between them is very large, and the force of gravity weakens rapidly with distance.
Here's an analogy: Imagine holding two magnets. If they are close together, their attraction is strong. If you move them far apart, the attraction becomes much weaker. The same principle applies to the gravity between Earth and Mars.
The gravitational force between Earth and Mars is not strong enough to be noticeable in our everyday lives, but it does play a role in the long-term orbital motions of both planets.
