Which of the following best describes the origin of ocean tides on Earth?
A) Tides are caused by the difference in the force of gravity exerted by the Moon across the sphere of the earth.
B) The Moon's gravity pulls harder on water than on land, because water is less dense than rock.
C) Tides are caused by the 23 1/2 tilt of the earth's rotational axis to the ecliptic plane.
D) Tides are caused primarily by the gravitational force of the Sun.
E) Tides are caused on the side of Earth nearest the Moon because the Moon's gravity attracts the water.
Question 2
In relativity, two people share the same frame of reference only if
A) they are not moving relative to each other.
B) they are both located in the same place.
C) they are both located in the same place and are traveling at the same speed.
D) they are both located in the same place and are stationary.
E) they agree on the laws of nature.
Tides on Earth
The Atmosphere Screens Earth from Harmful Solar Radiation
Notice the reddish-brown haze caused by nitrogen oxides that is often over many major cities.
Earth’s Spheres
Earth’s Heat Budget
Earth 65 Million Years Ago