The document provides information about the moon and how its appearance changes from Earth. It states that the moon is the natural satellite of Earth, takes 27 days to revolve around Earth, and shines due to reflected sunlight from Earth. It explains that the portion of the moon illuminated depends on its position relative to the sun. The surface was found to be brownish, gray soil with glass beads when astronauts first landed. In addition, it gives definitions for astronomical units, light years, and parsecs as measures of astronomical distances.
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• Moon is the natural satellite of the Earth.
• The moon is the brightest object we see in
the night sky.
• The mass of the moon is 7.5×10²²
kilograms.
• It takes around 27 days for the moon to
revolve around the Earth.
• The moon shines by reflecting the sun’s
light.
• The moon‘s appearance from the Earth
9. MOON
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• We see the moon because the sunlight
falling on it gets reflected towards us
(Earth).
• We see only the part of the moon from
which the light of the sun is reflected
towards us(Earth).
• It depends on the position of the moon in
relation to the sun.
12. • It should be remembered that the Moon
revolves around the Earth which itself revolves
around the sun.
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13. MOON’S SURFACE
• Our moon has been an object of fascination for the poets and
story tellers.
• But when the first astronauts landed on the moon ,they found
the soil was brownish ,medium grey ,slightly cohesive ,granular
material which contained tiny glass beads.
• The moon has craters and a large number of steep and high
mountains.
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16. MEASURING ASTRONOMICAL DISTANCES
• Astronomical unit (AU) – it is defined as the mean distance of the earth from the sun.it is
equal to a distance of 1.496×10^11m . On this scale Jupiter is just over 5 AU from the sun
and pluto about 40 AU.
• Light year (ly)- it is the distance travelled by light in vacuum in one year . The speed of
light in vacuum is given by 3×10^8 ms-1 . the number of seconds in one year is 3.16×10^7
s therefore one light year is given by {ly =3×10^8 ×3.16×10^7 m = 9.48×10^15 m}.
• Parallax Second (parsec) (pc)- it is the distance at which an arc of length one astronomical
unit subtends and angle of one second.the term parsec comes from the words PARallax
and SECond . 1 parsec = 3.26 ly = 3.08×10^16.
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