Hopefully I have this right. When they discovered the electron, they immediately realised that the electron should get sucked into the nucleus due to the electromagnetic force from the opposite charges. Why didn't they assume that the electron could orbit the nucleus to cancel out the electromagnetic force if it was travelling fast enough, just like the Moon orbits the Earth to cancel out the gravity? The reason why I ask this in the homework section is because it is in my textbook. I am not sure if I will have to know this.