Page 322 - ABCTE Study Guide_Neat

Sun and the Sun is in its northernmost position in the sky. Hence in the northern hemisphere, we see the
sun higher in the sky, the Sun's rays strike the northern hemisphere more directly, the daylight periods are
longer, and it gets hot.

On the winter solstice, December 21, the reverse is true. The northern hemisphere is tilted 23.5° away
from the Sun. Hence we see the Sun lower in the sky, the Sun's rays strike the northern hemisphere less
directly, the daylight periods are shorter, and it gets cold out. On the spring and autumn equinoxes, March
21 and Sept 21, the Sun is directly over the equator. Clearly it is the tilt of the Earth's axis, and the
revolution of the earth around the sun that causes the seasons and also causes the seasons to be
reversed between the northern hemisphere and the the southern hemisphere. The changing distance
between the Earth and the Sun does not cause the seasons.

What Causes Lunar Phases?

As the Moon orbits the Earth every month, its position in the sky changes. It rises about forty-eight
minutes later every day. Hence depending on where it is in its orbit, the Moon might be seen at any time
of the day or night. At any given time, half the Moon is lighted by the Sun and half can be seen from the
Earth. But these are not always the same parts of the Moon. If the Moon is directly opposite the Sun in the
sky, we see the daylight side of the Moon and call it a full Moon.

If the Moon is between the Sun and Earth, we see only the nighttime side of the Moon and call it a new
Moon. If the Moon is at a ninety-degree angle from the Sun in the sky, we see one of the quarter phases.
Less than ninety degrees gives us the crescent phases, and more than ninety degrees gives us the
gibbous phases. The lunar phases are not caused by the Earth's shadow falling on the Moon. That is an
eclipse.

What Causes Eclipses?

When the Moon passes between the Sun and Earth and blocks the sun from view, the Moon's shadow
falls on the Earth. That is a solar eclipse. A solar eclipse can only occur during the new Moon, but not
during every new moon. The Moon's shadow may fall above the north pole or below the south pole.

During the full Moon, when the Moon is opposite the Sun in the sky, Earth's shadow might fall on the
Moon. This is a lunar eclipse. We don't have a lunar eclipse during every full Moon because the shadow
may fall above the Moon's north pole or below its south pole.

Question

Which moon phase is most likely to cause a solar eclipse?

A Crescent

B Quarter

C Gibbous

D Neither