The Scale Earth
[The idea for the 80 inch scale Earth
came from a presentation by Astronaut/Senator John
Glenn]
copyright: David Carpenter,
2001
Imagine a globe, 80 inches [2 meters] in diameter. I'm 6' 4", and that's 4 inches taller than me. At this scale, every inch represents 100 miles on the real planet Earth [every 1.5 cm represents 100 km]. The real State of Ohio is about 200 miles wide, so our scale Ohio is about 2 inches wide.
At this scale, how big would Mt. Everest be? Are the "lumpy-lumpies" that pass for mountains on many ordinary globes to scale?
The real Mt. Everest is about 5 1/2 miles high. The scale mountain should therefore be only about 1 1/2 mm.
How deep are the oceans then? The deepest ocean trenches are about 7 miles deep. Again, that's only about 1 1/2 mm below scale sea level. The real Earth is shown to be extremely smooth!
What's the Earth made out of? Many people will say that it's 7/10 water and 3/10 land, but that's a surface perspective. Filling those millimeter deep oceans will only require about four or five liters of water. But filling our 2 meter ball will require over 4000 liters of rock and iron. To a first approximation, our planet can be modeled as a giant rusty ball bearing flying through space.
What about the atmosphere? About 99% of the atmosphere is within 30 km [about 20 miles] of the surface of the real Earth. On our scale Earth, that's less than 1/4 inch [or about 5 mm].
Every fish that has ever swam, every critter that's ever crawled, every bird that's every flown, every ship, airplane, car, etc., moves about in a very thin band only a few millimeters thick on our scale Earth! In my classroom, I use a meter stick as a compass to draw my 80 inch [or 2 meter] diameter scale Earth on the marker board. The width of the mark made by the marker is as wide as the band that all human activity except for space flight is confined to. No wonder astronauts have a sense of awe when they look down at the Earth from a height of...hey, just how high are they?
The International Space Station orbits at an altitude of about 225 miles. The shuttle can reach a maximum altitude of about 300 miles. That means to scale, they orbit only a little over 2 inches above our 80 inch Earth. Their orbits have to be pretty good circles to keep from hitting the planet! A scale 3 inches is as far as the shuttle and any astronauts can go.
"Wait a minute," you say, "we've been to the moon. That has to be farther than a scale 3 inches away." It is. To scale, the moon would be about the size of a 20 inch beach ball, and around 200 feet away. But the shuttle doesn't go there. The only rocket capable of sending a large enough spaceship to carry people to the moon is the Saturn V moon rocket. None of these have been built since the 1970's. Only 6 missions actually landed a total of 12 people on the moon, and the last was in 1972. Since then, people have only gone a scale 2 inches or so from the Earth. Smaller satellites are routinely launched farther. The satellites in geosynchronous orbit are 220 scale inches from Earth. Space probes are even sent to the other planets of our solar system. But to put these in scale, even our 80 inch Earth becomes way to big to deal with. At this scale, the sun is a 730 foot [220 m] diameter ball of plasma 175 miles [280 km] away. The scale planets of our scale star are hundreds to thousands of miles away.
If we want to model the solar system, we need a lot smaller scale. We'll shrink the Sun down to the size of a basketball.
To read about this model, click on Scale Solar System Model.
copyright: David Carpenter, 2001
