A Scale Model of the Local Universe, for CSU Fresno
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[Background: Some computers won't let you type exponents.  A way of
expressing scientific notation therefore often seen on computers is to
write 1.5e8, instead of the more conventional 1.5 x 10^8.]


Charlie Duke, who walked on the Moon during the Apollo 16 mission in 1972,
said that "From the Moon, the Earth looked like a little blue marble---the
most beautiful little blue marble you could imagine."

Let the Earth be represented by a little blue marble, 1.50 cm in diameter
(0.75 cm radius).  The radius of the real Earth is about 6380 km.

On this scale, the Moon would be about the size of the head of a small
finishing nail, since the Moon's radius is about 1/4 that of Earth's.

The Moon is about 60 Earth radii away from the Earth.  On our scale, this
would put it 44 cm away from Earth.

On this scale, the Sun would be 174 m away from Earth---which from the
classrooms where P Sci 21 is held, would put it near the fountain, by the
University Student Union building.

The Sun's radius is 108 times that of Earth's, and so on our scale, would
be 1.6 m in diameter---about as tall as many of my students.  (About
5'4").

At closest approach to Earth (also known as opposition), Mars is about 55
million km from Earth.  On our scale, if the Earth were in the classrooms
where P Sci 21 is held, this would put Mars in my office, in the new J
wing of McLane Hall.  The radius of Mars is about half that of Earth's,
and so on our scale, this would make it about the size of an orange seed.

The diameter of Jupiter is about 11 times that of Earth.  On our scale,
this would make it 16.5 cm in diameter---about the size of a cantaloupe.
At 5.2 times the average distance between the Sun and Earth (an
Astronomical Unit or AU, 1.5e8 km) from the Sun, at opposition to Earth,
on our scale, Jupiter would be about 1 km away.  This would put it in the
middle of the vineyard north of Barstow Avenue.

Pluto, at 39 AU from the Sun, would on our scale be 6.6 km away---in the
Tower District of Fresno.

And now for the punchline:

The nearest star, aside from the Sun, is 4.3 light-years away.  On our
scale, this would be 4.7e5 km away---greater than the distance to the
(real) Moon!

MORAL: The stars are Suns, and are _very_ far away.