Astronomy Picture of the Day
Discover the cosmos!
Each day a different image or photograph of our fascinating universe is
featured, along with a brief explanation written by a professional
September 14, 1995
The Far Side
The Soviet Lunar Program
This historic picture was humanity's first glimpse of the far side of
Moon. It was taken by the Soviet spacecraft
Luna 3 in October of 1959. Luna 3 followed closely on the heels of
another Soviet probe, Luna 2,
which had become the
first spacecraft to impact the Moon
on September 13th of that same year.
Why does the Moon have a far side?
Gravitational tidal forces within the
Earth-Moon system have synchronized the Moon's
period of rotation around its axis with its orbital period at about 28 days.
So, as the Moon moves around its orbit its rotation exactly compensates,
keeping the same face toward the Earth.
Tomorrow's picture: Space Station Mir Over Earth
| About APOD
Authors & editors:
NASA Technical Rep.:
Specific rights apply.
A service of:
Michigan Tech. U.