Space is big, man. Like, really big.
But how big is big, exactly? Things that exist in the universe deal with size scales and time scales that are hard to wrap your head around, even if you read this stuff all the time like I do. Even within the Solar System itself, the distance that the New Horizons probe has traveled to reach Pluto – 4 billion miles – is hard to personalize or understand.
So, since tangible scales are easier to understand, I decided to find the right scale for a Rochester audience. @brianhalligan on Twitter did a lot of talking about this idea with me, so I started to settle on the idea of the Strasenburgh Planetarium as the focus of my new thought experiment.
As it happens, East Avenue between the Strasenburgh and Main St is just about as straight a line as any street in Rochester. So it ends up being the perfect yard stick for measuring distance. “Why not?” I thought. “Why not line up all the planets, to scale, down the length of East Ave? Let’s get started!
The Solar System on East Avenue
We begin at the center of the Solar System: Sol, our sun. One might be tempted to expect the sun to be a very large object in the Solar System. And indeed it is, inasmuch as the sun makes up about 99% of the total mass of our system. But just how big would you expect the sun to be if the Solar System takes up five city blocks?
At this scale, the sun is just about the size of a dinner plate. 11.46″ round, to be exact. It’s almost incredible that such a comparably small object projects a gravitational field wide enough to capture Pluto, almost a mile away at this scale. The sun’s light, while brighter than other stars, isn’t much more significant to Pluto’s skies than is the North Star to our own. Yet the dust, rock and ice left over from the sun’s creation is what Pluto is made of.
In contrast, the rocky worlds are actually all bunched up relatively close to the sun. At this scale, Mercury is within 60 feet of the Sun. Two first downs, and you’ve passed the Winged Messenger. Which is not hard to do, considering that compared to our dinner plate-sized Sun, Mercury is only about 0.040″, somewhere near the width of 10 human hairs.
At 92 feet away from our Sun, Venus makes it’s home. 127 feet away from the Sun is our home on Earth. We’ve not yet left the front courtyard of the Rochester Museum and Science Center. And the diameter of these planets is less than the size of a BB pellet, about one tenth of an inch. Finally for the Rocky Worlds, there is Mars. Mars is 212 feet away from the Sun and about half the size of both Earth and Venus.
The Gas Giants
After we pass through the Asteroid Belt, we finally get some distance between us and the sun. Out here, we’re past what is known as the “snow belt,” meaning that it’s too cold to have liquid water and it’s cold enough to create “gas giants” like Jupiter and Saturn. Gasses like nitrogen and helium coalesce into clouds around giant snowballs of frozen water, and those balls become planets. Big ones.
Where is Jupiter? 695 feet away from the Sun, half way between Goodman Street and Arnold Park. At this scale, Jupiter comes in at a whopping 1.15″, just shy of a golf ball in size. Not an impressive size at this scale, but remember: that’s 33 times the diameter of Earth.
At 1289 feet, Saturn sits just past the threshold of the Third Presbyterian Church, on the corner of Meigs. This gas giant doesn’t lose much on Jupiter in size, coming in around .96″. Both Saturn and Jupiter have an extensive collection of moons. Jupiter boasts 67 moons, while Saturn has a nothing-to-sneeze-at 62 moons. This, on top of Saturn’s trademark rings, which most scientists now believe are actually the debris of at least one collision of some of Saturn’s former moons.
Hanging with the Young Rich of Rochester, Uranus lies 2,562 feet away from our Sun. That puts it in the same block as Murphy’s Law, on the Lawrence Street side. At this distance, the sun has already become just one more star in the night sky. Uranus is just about half an inch in diameter. We’re slowly creeping up on the dark, cold distances of the Outer Solar System and our ambassador from said distances, Pluto.
Several blocks down, arrive at the corner of Broadway and the WHEC studios. Suspended there among the traffic 3,867 feet from the Sun is a half inch ball of blue known as Neptune. We’ve flown a couple NASA missions past this Greek god planet, but compared to other bodies in the Solar System, it remains a relative mystery to science.
At the corner of East and Main, 5100 feet from where we started, we come to Pluto’s lonely orbit. Actually, that orbital distance is only an average, because Pluto’s orbit ranges from between 30 and 60 Astronomical Units away from the sun. At this scale, you might find Pluto anywhere from Broadway and East to Clinton and Mortimer. Yes, that means that Pluto’s orbit does occasionally cross Neptune’s. It is only a subtle gravitational harmony that prevents a collision of these two worlds.
Pluto measures less than four hundredths of an inch. Pluto is smaller than Mercury, and in fact is the ninth densest object in the Solar System. You can begin to see just why Pluto was demoted from planet to planetesimal: it’s just way too small and way too irregular to be in the same category as the other planets.
Next Stop: Alpha Centauri
Now that we’ve walked the length of East Ave and gotten a good perspective on just how much empty space lies between us and our neighbors, of course, we’d want to know what’s next? After you’ve reached Main Street and you’ve seen Pluto, what’s next to see? After this, we’re still moving in a straight line, but of course, we’ll be crossing lots of streets.
Pluto is actually our ambassador from the Kuiper Belt, whose outside edge would be right at the corner of Andrews and Water Street. The Heliosphere – the point at which the sun’s solar radiation no longer affects space – is about 2.5 miles away, putting it somewhere on Lyell Avenue.
And where, do you suppose, the next nearest star to our own lands in this scale? Don’t count on walking there. The answer would be Osaka, Japan. 6,703 miles away, as the very healthy crow flies. Wow.