The New Moon appears close to the sun
Q:
How come a new moon is always close to the sun?
A:
To answer this question, let's first consider the phases of the Moon. The Moon goes through phases because it revolves around the Earth in nearly the same
plane as the Earth orbits the Sun. The Moon always casts a shadow over half of its body. We see sometimes more of the Moon and sometimes less depending
on our viewing angle of the bright half. Our angle changes constantly through the lunar month as the Moon revolves about Earth. We call these changing
shadow and light patterns, the phases of the Moon.
I step outside with a tennis ball to visualize Moon phases. The Sun is almost setting when I face the Sun and hold the ball up to the Sun's low rays. I pretend
I'm the Earth and my outstretched arm with the tennis ball is the Moon orbiting Earth. I turn slowly all the way around and watch my tennis ball orbit me and
see the phases of the "moon" occur as the Sun casts shadows on my tennis ball.
First, I stand facing the Sun with the tennis ball in my outstretched hand. I turn a quarter turn counterclockwise and look at the ball. I now stand with my side to
the Sun. The Sun-me line makes a right angle with the me-ball line. I look at the ball: the half ball facing the Sun shines and the other half is in shadow.
When
the Sun-Earth line forms a right angle with the Earth-Moon line, the Moon is at First Quarter phase (or Third Quarter).
I turn another quarter turn and now the Sun's behind me. The Sun, the tennis ball and I form a straight line. My whole tennis ball faces the Sun and shines
brightly with no shadow. When the Sun, Earth, and the Moon line up on the same line, then we have a Full Moon.
Another quarter turn and my left side faces the Sun. I'm now three-quarters the way around from where I started. Half of the tennis ball shines and half is in
shadow. The Third Quarter Moon is half illuminated.
Finally, I turn a quarter turn more and I'm back to where I started, facing the Sun with the tennis ball between me and the Sun. This is New Moon; the Sun and
Moon are in conjunction and the night side of the Moon faces Earth. When the Moon is New, the dark Moon and the bright Sun travel together through our
sky and the Moon's shadow hides it from Earth dwellers.
To answer your question about the New Moon: A New Moon always appears to be close to the Sun because all three bodies are on the same straight line in this
order: Sun, Moon, and Earth. We on Earth have to see the New Moon (except it's too dark to see easily) at the same time we see the Sun because it's on our
line of sight to the Sun. When we can see the almost-new moon, i.e., the Crescent Moon, it is almost on our line of sight to the Sun and, therefore, seems to be
nearby the Sun.
(Answered by April Holladay, science correspondent, June 13, 2001)
Further Surfing:
USATODAY.com: Moon-phase graphic
U.S. Naval Observatory (USNO): Moon phases
USNO: Virtual reality Moon phases
NASA: Phase calculator
U of Wisconsin: Moon phases
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