Why do we have seasons on Earth?
A) As Earth goes around the Sun and Earth's axis remains pointed toward Polaris, the Northern and Southern hemispheres alternately receive more and less direct sunlight.
B) The tilt of Earth's axis constantly changes between 0 and 23 1/2, giving us summer when Earth is tilted more and winter when it is straight up.
C) Earth's distance from the Sun varies, so that it is summer when we are closer to the Sun and winter when we are farther from the Sun.
D) Seasons are caused by the influence of the planet Jupiter on our orbit.
Question 2
Which of the following best describes the nature and origin of the atmospheres of the Moon and Mercury?
A) They have thin tropospheres only, with gas coming from evaporation and sublimation.
B) They have thin exospheres only, with gas coming from impacts of subatomic particles and photons.
C) They have only small amounts of gas, all of which is leftover from outgassing long ago.
D) They have very thin atmospheres produced by outgassing, but still have the layers of a troposphere, thermosphere, and exosphere.
Comparison of Ceres with the Moon and Earth
Fossil remains of anatomically modern humans from the Czech Republic and from China (center crania)
Earth-Sun Relationships
Humans are related to Earth’s other organisms
The Distribution of Water on Earth
Planet Z-34 has a mass equal to 1/3 that of Earth, a radius equal to 1/3 that of Earth, and an ...