 Well for this adventure we come back to present time to my lab to discuss some very neat things that happen as a result of planetary motion. One such example is the tides on the Earth. You may ask yourself, or not, why does the ocean have tides? Well the answer for this comes from perhaps an unlikely source - the moon. Yes, as discussed in the Newton section(s), the moon has a force of gravity on the Earth. Since the Earth is so much larger than the moon, the Earth doesn't get hurdled into it, but the Earth does orbit the moon as a result. Now since the moon pulls on the Earth, anything on the Earth experiences a upward gravitational field effect. The effect on normal objects such as you and I is very small, but the effect can be seen on a moveable object like water. When the moon orbits the Earth, it "pulls" the water with it - causing large tides directly beneath it on the Earth. Conversely, on the exact opposite side of the Earth, you get a bulge of water that sinks away from the planet - tides. Thus you get high tides at two ends of the planet. The Areas 90 degrees from the Earth experience low tide, since the effect of the moon is at a minimum here.  We have spoken to Kepler and found out that planetary orbits are elliptical. But as Newton said in his law of universal gravitation, planets are attracted to each other. Thus when planets get close together, you get a perturbation in its orbit. In other words, the planet's path gets slightly altered to move closely to the other planet. The neat part of this is that we can use this to find out if there are more planets or stars than we know. In fact, scientists now say that there is a 10th planet which is too far to see. Called Humphrey, the perturbations in Pluto's orbit have led to the conclusion that there really might be a tenth planet. Just so you know, this planet likely is pretty small (large as Pluto) and will likely not be found for a while yet. 
If you think you have mastered the subject |
The Earth
has tides because of the gravitational pull of the moon