E-mail a message to me. This is to demonstrate that you have an email account and know how to use email. The email must come from your own account, not a friend's. I had to recieve your email message by class time on September 10. Gravity keeps the crust of the Earth, where we live, attached to the planet.
Gravity keeps the planets, comets, and asteroids of the solar system bound in orbit around the Sun.
Gravity keeps the Sun in orbit around the center of the Milky Way. Gravity keeps the Local Group of galaxies together. This has been measured to be about 93 million miles or 150 million kilometers. Imagine building a model of the Solar System on your campus. For the sizes of the planets we must first calculate how much smaller the model solar system is than the real solar system.