Date: July 16, 2010

Title: Your Head is Jupiter


Podcaster: Sandy Antunes


Description: You get to convert your desk to a solar system, but beware, space is bigger than most think!

Bio: Sandy looks at the science and the people in today’s 9-5 pro astronomy world. Born in the heart of a dying star (as we were all), he draws from his research, writing, and game design work to bring you the joy of science twice a week at— and to launch the first personal science/music satellite via

Today’s sponsor: This episode of “365 Days of Astronomy” is dedicated to truck drivers looking at the stars, desiring to know more about them.


[Sandy] We’re going to start with a quote from classic literature, then I’ll be walking you through how to simulate a solar system at your desk. I’m Dr Sandy Antunes, the Daytime Astronomer, on 365DOA.

Our classic literature quote is excerpted from Douglas Adam’s “The Hitchhiker’s Guide to the Galaxy”:

The introduction begins like this: “Space,” it says, “is big. Really big. You just won’t believe how vastly hugely mindboggingly big it is. I mean you may think it’s a long walk[sic] down the road to the chemist, but that’s just peanuts to space. Listen . . . ” and so on.

(After a while the style settles down a bit and it begins to tell you things you really need to know, like the fact that the fabulously beautiful planet Bethselamin is now so worried about the cumulative erosion by ten billion visiting tourists a year that any net imbalance between the amount you eat and the amount you excrete whilst on the planet is surgically removed from your bodyweight when you leave: so every time you go to the lavatory it is vitally important to get a receipt.)

To be fair though, when confronted by the sheer enormity of distances between the stars, better minds than the one responsible for the Guide’s introduction have faltered. Some invite you to consider for a moment a peanut in reading and a small walnut in Johannesburg, and other such dizzying concepts.

The simple truth is that interstellar distances will not fit into the human imagination. Even light, which travels so fast that it takes most races thousands of years to realize that it travels at all, takes time to journey between the stars. It takes eight minutes from the star Sol to the place where the Earth used to be, and four years more to arrive at Sol’s nearest stellar neighbour, Alpha Proxima. For light to reach the other side of the Galaxy, for it to reach Damogran for instance, takes rather longer: five hundred thousand years.

End of quote, back to this podcast. Time to explain it using peanuts in Reading and a small walnut in Johannesburg. Bode’s Law, more accurately the Titius-Bode Relationship, isn’t a law at all. It’s jsut an observation that, roughly, each planet is about twice as far out from the sun as the previous planet. Although it breaks down, especially around Neptune, it is a handy rule of thumb approximating the size and scale of our solar system.

And right now, you are going to make a solar system around your computer. Now the screen is the Sun. And if you lick your finger and touch the screen, which is something I don’t actually recommend, you’ll leave a roughly planet-sized ‘dot’ on it. Planets are tiny compared the sun, even though they seem big to us.

If your monitor is the Sun, where is Mercury? Right next to it, in space terms. But we’re already going to run out of room mimicking that. Really. If you have, like, a 20 inch monitor and you’re saying that’s the size of the Sun, the Sun’s about 0.01AU in diameter, we have to put Mercury out about 40 Monitors away, 0.4AU. That’s over 60 feet away on this scale, and that’s for the closest planet. And Venus is going to be about twice as far, about 120 feet away. So already if the monitor is the size of the Sun, we can’t fit.

So we need to make a smaller scale if we’re going to make the entire solar system on your desk. Let’s say the Sun isn’t your monitor. It’s just on your monitor. We’ll say it’s the size of period, the dot you type at the end of a sentence on your computer monitor. Maybe 1 millimeter, or 0.04 inches or so.

So on this scale, Mercury is going to be about an inch and a half away from your monitor. That’s about 3 finger widths away. So put your 3 fingers away from your monitor, that’s where Mercury is. Hello, Mercury!

Venus, the next planet out, at 0.72AU, is around 2.8 inches, about 3 inches away from the monitor, a little less than the width of all your fingers together.

Earth is 1 AU by definition. An AU (Astronomical Unit) is defined as the average distance from the Sun to the Earth, a very handy unit– especially when describing the solar system. Our scale says, if the sun equals 1 mm, then the distance from monitor in inches is roughly 4 inches per AU. We’re going to round it to 4 inches to make this easier. So Earth is 4 inches away from your monitor, the width of your full hand.

Mars is 1.52 AU, so that’s about 6 inches, or about the size of a stapler away from the monitor.

Next is the asteroid belt, that’s a planet-less gap that has the big asteroid Ceres, which can debatably be called a planet (much like Pluto). At 2.77AU, that’s 11 inches, nearly a foot away– two hand lengths or so away from the sun, that dot on your monitor.

Jupiter, at 5.2AU, comes in at 21 inches away. That’s about the distance you should sit away from your monitor when you’re leaning a bit too close than the recommended ‘arm’s length away’ viewing distance. So go an arm’s length away, lean in a little bit, your head is Jupiter!

Saturn, 9.52AU, 38 inches in our scale. Jupiter was a bit closer than arm’s length from the monitor, Saturn is about leg-length away.

Uranus, 19.2AU, about 6.4 feet away. Even if you’re 6 feet tall and lie down with your feet at your monitor, Uranus is going to be just past the top of your head.

Neptune, 30AU, is about 10 feet away. If you have a rolling chair like I do and you kick off from your desk, you’ll roll about 10 feet away. If you’re in a cubical, you’ll also probably hit your cube wall. Or reach near the end of your office.

If your computer is positioned near a stairs like mine and you kick off, though, you’ll fall off the stairs and die. I know this by experiment– I measured first. Be warned.

Pluto is going to be 13 feet away, representing its average distance of 39.4AU. Or a bit closer or further, since it’s orbit is very eccentric– the famous factoid that Pluto is sometimes closer to the Sun than Neptune, depending where it is in its orbit.

Next up are either Eris or Sedna. Usually Eris is closer, but right now Eris is at the further part of its orbit, while Sedna is near the closer approach. But to make this podcast timeless, we’ll use their average distances.

Eris goes from 37 to 97AU, with an avg of about 67AU, or around 22 feet in our current scale. So go 22 feet away from your monitor. You’ll have to really crank up your speakers so that you can hear the rest of this podcast from there.

We’ll wrap up with Sedna. I hope you’re listening to his podcast via a portable device, actually, because otherwise you’ll miss the end of my podcast by the time you get to Sedna. Senda ranges from 76 to 975AU, averaging a semi-major axis of 525AU. So it’s out 175 feet. Yes, 175 feet. Go for it! Walk, run, roll! Go to our scale Senda!

Are you at Sedna yet? Congratulations, I’ve gotten you out of your office! Take a break, have a nice walk, enjoy being outside, and this has been Dr Sandy Antunes, the Daytime Astronomer, on 365DOA. To tide you over until next month’s podcast, you can always read my work twice weekly at Goodbye!

End of podcast:

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