Use words revolve and rotate to explain earth’s movements in space

Two friends at different locations want to communicate with each other by sending low energy signals. which of the following methods can they use to communicate? a) produce x-rays using colliding electrons and send them to radios, which capture sound b) send messages using infrared radiation, which travel in the form of waves c) send radio waves through intervening media like radio and television d) produce sound waves using microwaves from heated objects

How do scientists think that gravity affected the formation of our solar system?

Name the element in group 17, period 2. (periodic table)