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 Our Scale Model Solar System

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The long third floor hallway of the Arts & Science Extension is the site of a fun aid to understanding the huge distance scale of the Solar System - the space in our "neighbourhood".

Scale Model PosterNine floor decals, each with the image of one of the planets, have been spaced along the 55 m long hallway, so that Mercury is at one end (next to AS 3034, near the location of the new atrium) and Pluto at the other (near the stairs to the observatory).

The relative spacing of the planet decals illustrates the real relative spacing of the planets’ orbits.  The sizes of the decals were chosen just for visibility - the rocky “terrestrial” planets (Mercury, Venus, Earth, Mars and Pluto) are 10 cm in diameter, while the giant gas planets (Jupiter, Saturn, Uranus and Neptune) are 15 cm.

Because even the Sun is tiny relative to the spacing of the planets, it’s almost impossible to show both the sizes of the planets and their orbits to the same scale. Using the distance scale of our floor model, for instance, the Sun should be just under 1 cm in diameter – the size of a small marble! The Earth at this scale would be less than 1/10 of a millimeter across, smaller than the size of the period at the end of this sentence. A poster (shown at right) on the wall at each end of the hallway shows the relative diameters of the planets.

The best way to appreciate this floor model is from the atrium end:

Look down at the floor nearby and find the dot indicating the position of the Sun. The coziest part of the Solar System is here, with four small, rocky planets clustered closely about the Sun. It’s easier to come to grips with the scale of the Solar System if we abandon thinking of distances in kilometres, and consider instead the light travel time – the time needed by light to travel a given distance. This is like thinking about a drive to Deer Lake as 30 minutes of car travel time instead of 50 kilometres -the big difference being that light travels a bit faster than a car (300,000 km/s, in fact!). A beam of light leaving the Sun will cross the orbit of Mercury after only 3 ¼ minutes, reach Earth in about 8 1/3 minutes and zip by Mars in just over 12 minutes.

From here on out, the distances become truly vast, and the planets we now encounter are giant bodies with thick, hydrogen-rich atmospheres. Our beam of light will reach Jupiter after 43 minutes, fly by Saturn after 80 minutes, and eventually cross the orbit of tiny Pluto 5 ½ hours after leaving the Sun.

Try walking from the Sun to Pluto – imagine yourself a beam of light, the fastest thing there is, and still needing 5.5 hours to reach your destination! Now stand at Pluto, and try to picture what you might see as you looked back toward the Sun – the brightest star in your sky, but no brighter than a streetlight would appear at the end of your street at home.

And now look outward, toward the stars. At the scale of our model, the neighbouring stars would be other small, isolated marbles, each about 400 km apart. A marble here, another in St John’s, another in Halifax, in Moncton, and so on… with their light taking years to reach their nearest fellows. And within our Galaxy alone, there are hundreds of billions of stars!

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