Guide to the Cosmos
on Radio

Hosted by
Dr. Robert Piccioni


Shop Now

Listen to Robert


About Dr. Piccioni

Free Videos

mailbox Newsletter

Gravity and the 3 R's

Click here for Broadcast

Why the Moon Orbits Earth

Moon Causes Earth's Tides

Image #1

Why the Moon Orbits Earth

Every minute, the Moon moves forward 38 miles (green arrow) and also falls 16 feet toward Earth (yellow arrow). The combination of forward motion and gravity turns the Moon just the right amount to keep it circling Earth.

Image #2

Moon Causes Earth's Tides

The Moon pulls every part of Earth toward its center, and pulls more strongly on nearer parts. Water nearest the Moon is pulled more than Earth's center, which is pulled more than water on the opposite side. Water on the top side is pulled in a direction that's slightly down, and water on the bottom is pulled slightly up. Thus we have two high tides and two low tides each day. The Sun causes tides also, but with half the effect of the Moon.

Light Redshifts & Time Changes
Image #3

Light Redshifts & Time Changes

As it moves away from a massive body, Light loses energy by reducing its frequency. Since the number of light's wave cycles can't change, a scientist at the top of the Space Needle says the frequency was less because the peaks took longer to pass. His clock must run faster than one in the parking lot.









myspace visitors