When the sky is clear but still only a small part of the moon is visible,
the cause may be any one of the following:
-- The moon is in its waning crescent phase, during the last 6 or 7 days
before New Moon.
-- The moon is in its waxing crescent phase, during the first 6 or 7 days
after New Moon.
-- An umbral lunar eclipse is in progress.
The "new moon" is technically not visible at all. The Moon is directly between the Earth and the Sun and none of the illuminated part is visible from Earth. Sometime on the day of the new moon, the Moon will appear as a very thin crescent (last crescent or first crescent).
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Only during a lunar eclipse, which can only happen during a full moon. The visible phases of the moon are caused by it changing its position relative to Earth and the sun. The visible portion is the moon's day side; the side facing toward the sun. The unlit portion is the night side, facing away from the sun.
The general term for the visible lit part of the moon is "the phase of the moon." The visible lit portion can have a crescent shape, a gibbous shape or a "half-moon" (half circle) shape.
Astronauts land on a half moon the same way that they would land on the moon any other time. A half moon is created when the sun is shining on only part of the moon, therefore making only that part visible. The other part that the sun is not shining upon is still there, just people on earth cannot see it because we are so far away.
When the sky is clear but still only a small part of the moon is visible, the cause may be any one of the following: -- The moon is in its waning crescent phase, during the last 6 or 7 days before New Moon. -- The moon is in its waxing crescent phase, during the first 6 or 7 days after New Moon. -- An umbral lunar eclipse is in progress.
only a small part of each is visible on the surface
Only a small part of culture is visible.
The "new moon" is technically not visible at all. The Moon is directly between the Earth and the Sun and none of the illuminated part is visible from Earth. Sometime on the day of the new moon, the Moon will appear as a very thin crescent (last crescent or first crescent).
The far side of the Moon.
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It depends on what kind of eclipse you are talking about. If it is a solar eclipse, no. The eclipse covers only part of the Earth, where the moon casts a shadow. and only a fairly small area will experience a total eclipse. A lunar eclipse is visible from anywhere that is facing the moon at the time.
... becoming smaller as time passes.
That's because a solar eclipse is caused when the Moon gets between the Earth and the Sun, blocks the Sun's light when viewed from Earth, and casts a shadow on Earth's surface. The Moon's shadow on Earth's surface is very small, and the moon only aligns with the Sun when viewed from a small area, so a total eclipse only happens for a very small region. If you're outside that shadow, the sky won't go dark, and the Moon won't completely block the Sun's disc, but you will see the Moon cover at least part of it. A lunar eclipse, on the other hand, is visible across the entire night side of Earth.
We only see one part of the surface, at any time the moons faces occur.