ih science Flashcards
why do we have different moon phases?
Depending on the relative positions of the Moon and the Earth only a certain portion of the Moon’s illuminated (lit up) side is visible from Earth. This is why the Moon appears to change shape throughout the month.
what does waxing mean?
when the lighted area appears to grow larger
When viewed from Earth the lighted side is on the right.
what does waning mean?
when the lighted area appears to grow smaller
When viewed from Earth the lighted side is on the left.
gibbous
more than half full but less than full
crescent
less than half
how long does it take for the moon to orbit around the Earth?
It takes 27.3 days for the Moon to orbit the Earth, but approximately one month to go through its phases. This is because it takes a little longer for the Moon to “catch up” to Earth as the Earth orbits the Sun.
how long does each phase last
Each phase lasts approximately 3 to 4 days.
Does everyone on Earth see the same phase of the moon?
During a 24-hour period, everyone on Earth will see the same phase of the Moon, since the Moon stays in one place relative to Earth as the Earth makes one rotation on its axis.
eclipse
occurs when the shadow of one celestial body falls on another.
syzygy
when the Sun, Earth, and Moon are in a straight line.
For a solar or lunar eclipse to occur the Sun, Earth, and Moon must be in syzygy (perfectly aligned).
umbra
dark, inner part of a shadow
penumbra
lighter, outer part of a shadow
Solar eclipse
occurs during new moon when the sun appears to be completely blocked by the moon except for a bright halo of light. An observer would have to be in the umbra to see this eclipse.
partial solar eclipse
the new moon blocks only part of the sun’s light. An observer would have to be viewing from the penumbra.
annular eclipse
occurs when the moon is farther away from Earth in its orbit so the moon does not completely cover the sun. The sun’s outer edges can be seen as a ring of light around the dark moon.
what is a total lunar eclipse
A total lunar eclipse occurs when the Earth comes directly between the Sun and the Full Moon. Earth blocks the Sun’s light and casts a shadow on the Moon.
partial lunar eclipse
occurs when the Moon does not fully enter the umbra.
penumbral lunar eclipse
occurs when the moon passes through the penumbra.
why don t eclipses happen every month
Solar and lunar eclipses do not occur on every full and new moon because the Moon’s orbit is tilted 5 degrees and the Sun, Earth, and moon are not perfectly lined up.
how many are each year
There are approximately 2 solar and 2 lunar eclipses each year.
how long does each last
A lunar eclipse lasts much longer (hours) than a solar eclipse (minutes).
what phase does a solar eclipse happen
new moon
what phase does a lunar eclipse happen
full moon
