Transcript 2 Inch Universe Analogies

The TWO-INCH Universe
A powerful set of analogies to
examine size and distance in
astronomy
Source: smithsonianeducation.org
Earth’s diameter = 8,000 miles
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QUESTION: If Earth is just two inches
wide, how big would the Moon be at this
scale?
Moon = ¼ inch!
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actual diameter = 2,000 miles
QUESTION: At this scale, how far apart
should they be?
5 feet!

actual Earth-moon distance = 240,000
miles …1 light second!
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QUESTION: How big should the sun be in
this analogy?
A minivan (16 feet across)!

Actual Sun diameter = 875,000 miles

QUESTION: If the 2-inch Earth were
placed in the middle of the classroom,
where would the minivan need to be
parked to represent the position of the sun
at this scale?
6 football fields away!
The van could be parked at Family
Fitness!
 Actual Earth-Sun distance = 93,000,000
miles or 8 light minutes
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NEW ANALOGY

Scale down the minivan sun into a 2-inch
sun
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QUESTION: At this scale, how big would
Earth be?
A grain of salt!
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QUESTION: How big would the moon be?
A speck of dust!

QUESTION: How far away would this
“speck of dust” moon be from the “grain of
salt Earth”?
½ inch!

QUESTION: How far away would the sun
be from the “grain of salt” Earth?
20 feet!
New Analogy: 2-inch Solar System
Sun speck in center, planets would be
invisible at this scale!
 Actual solar system size = 7,000,000,000
miles (10 light-hours)
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Next nearest star at this scale (Proxima
Centauri) would be 2 football fields away!

Actual distance = 25.8 trillion miles or 4.3 LY

Sun is 1 of billions of stars in our galaxy

QUESTION: At this scale, how big is the
Milky Way?
About the size of North America

Actual Milky Way size = 100,000 LY

At this scale, if the tiny dot of light at the
center of the solar system were a grain of
salt, a teaspoon of the salt would
represent about 100,000 of the Milky
Way’s 200+billion stars!
New Analogy: The Realm of
Galaxies
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Side note: Andromeda galaxy is a galaxy that is
very near the Milky Way and is seen as a single
smeary light to the naked eye
Actual Andromeda size = 1.3 million trillion miles
(220,000 LY)
Shrink the “continent-size Milky Way” down to 2inches
QUESTION: If Milky Way is 2-inches big, what is
the distance between these two galaxies?
~ 5 feet!

Actual Milky Way-Andromeda distance = 15
million trillion miles (2.5 million LY)

At this scale, individual stars in these galaxies
would not be visible even with a microscope
At this scale, the deep space galaxies seen by
Hubble would be 4 miles from this classroom!
So…QUESTION: How big is the universe?
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Fun things to consider….
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Do you think it’s likely that there is life elsewhere
among these incredible distances? How about
intelligent life?
What would be some of the challenges in trying
to communicate with other life around other
stars?
Some people say they feel insignificant after
understanding the scale of the universe. Others
say it makes them feel that life on Earth is
special, that the human mind has only grown
more significant by understanding this vastness.
What is your view?