Date: April 6, 2011
Title: The Whole World in Your Hands
Podcaster: Rob Berthiaume
Links: www.yorkobservatory.com
www.youdontfreezeinspace.com
Description: Things in space are incredibly big, long-lived, and far apart. It’s hard (if not impossible) to grasp the scale of it all in human terms, but why not give it a try?
Bio: Robert Berthiaume is working towards an MSc in atomic physics at York University in Toronto, Canada. When he can get away from building diode lasers, he rides his motorcycle when the sun is up, and shares the stars with the public at the observatory when it’s not.
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Transcript:
Hi there. I’m Robert Berthiaume bringing you today’s edition of the 365 Days of Astronomy Podcast from the York University Observatory in Toronto, Canada. Things in space are incredibly big, long-lived, and far apart. It’s hard, if not impossible, to grasp the scale of it all in human terms. Modern science tells us things like “the Sun is 5 billion years old”, and that “The nearest galaxy is several million light years away”. Having studied astronomy for several years now, I’ve grown more accustomed to these terms and scales. It seems I’ve come to easily comprehend and relate to the enormous timescales and distances I deal with every day. But then a little while ago, I realized that this was just some mental construct, some false reality I’ve created in some sector of my brain that allows me to avoid confusion and distraction when it comes to astronomy, much like one can flick a switch when watching sci fi or fantasy films and just accept that people can fly on brooms, cast spells, and teleport.
Any decent popular book or text on astronomy will almost immediately take the reader through the scales of the universe, starting with the solar system, then the local stellar neighborhood, then the galaxy, and so forth. But things get so big, so quick, it quickly stops making any real sense. But I think that to some extent, it can be done, and today I’d like to try to get you to see just a small part of space in human terms that make sense based on everyday life.
I’m going to try to describe what the Earth-Sun-Moon system looks like, to scale. This will be something you can start, but not complete, inside your home. We’re going to need a basketball, or a ball or balloon of similar size. We’ll call this the Earth. The Earth is almost 13 000km across, and a basketball is about 24cm across. This means, at this scale, 1 mm represents about 50 km. Great, lots of numbers, but I said I’d try to keep this real. So let’s see what our basketball Earth looks like in human terms.
Well, the tallest mountain on Earth, Mt Everest, would only be the height of a few human hairs. Like me, you may not have had the privilege of seeing Everest first hand, but you may have seen mountains of some sort. A typical mountain a few kilometers tall would scale to be about the height of a human hair. Likewise, the deepest oceans are the same sort of size. A few human hairs, or a couple of sheets of paper to look at it another way. Now take a deep breath. Look outside, check out the clouds, the big blue sky, planes flying high up above: this all happens in the atmosphere. In our model, all of this is well contained in the first millimeter away from the surface of your balloon or ball.
Now, go to your change jar, find a nickle and place it on the surface. This is the distance you’d be able to drive in a day. It represents about 1000 km, which is a decent distance for one person to in a single day. If you were traveling on vacation and stopping for lunch and sightseeing, it might be more realistic that you’d drive across a penny or a dime, and if you were really pushing it, you might cover a quarter. Hopefully this all gives you some relatability so far. We’ll need it now that we’re going to talk about space. Going outside might be a good idea right about now.
Looking at the Earth that is in your hands right now, let’s see if we can imagine just how far out in space astronauts travel. Picture the fully fuelled space shuttle ready to blast off into the depths of space to explore the cosmos. 3, 2, 1. liftoff! And off it goes…about 7mm above the surface of the ball. This is Low Earth Orbit, where the space shuttle, International Space Station, and all manned spaceflight has taken place for decades. About 1 billion dollars each launch, just to take some people the width of a pea, or a kernel of corn, above the Earth. This may help to explain why so many people are itching to, as they say, “get out of Low Earth Orbit” and to go out into space a little bit further.
Geostationary satellites that relay our TV and data signals are in special orbits that keep them hovering above the same point on Earth as it rotates. These are about 75cm away from the surface of the ball, which is the height of three sheets of paper.
The Moon in our model would be the size of a tennis ball. Again, you don’t need a tennis ball in particular, you can substitute it with a similar sized onion or apple or orange or something. Most people picture the Earth and Moon really close to each other, but you’ll need to take a few steps away from the basketball to get the scale right. A few more…keep going…don’t stop until you’re about 7 meters apart. This is equivalent to one person standing on the side of a two-lane road with the Earth basketball, and another person standing on the opposite side with the tennis ball Moon, two lanes away.
How fast do things go in space? Well our astronauts on the shuttle or ISS do one circle around the Basketball, one pea above the surface, every 90 minutes. The Apollo astronauts went from the Earth to the Moon, crossing two lanes of traffic, in 3 days. Light, the fastest thing in the universe, makes the trip in just over a second. This all might not seem too fast, but consider that, again, driving at highway speeds for 24 hours straight, only gets you across two quarters, and the whole trip from basketball to tennis ball would take you 6 months.
The Sun is about 400 times further away from the Earth as the Moon is. In the scale model here, you’ll have to set your Earth and Moon on the ground, and then start walking at a normal pace. Don’t stop for at least 30 minutes, this will put you just under 3 km away from where you started. This is the location of the Sun. How big is it? 26 meters across. That’s the length of a basketball court, or a North American hockey rink. I can’t think of any household items that are ball shaped and the size of a hockey rink, so at this point, the realism of the scale model starts to break down, and we have to use our imagination.
Where is the closest star to the Sun in this model? You should picture our basketball Earth and tennis ball Moon sitting a 30 minute walk from your local rink or court, the Sun, and then a two car garage floating in space twice as far as the real Moon. That’s Proxima Centauri, the absolute closest star to Earth beyond our Sun.
You can make the model a little more detailed by adding some of the close planets along the way. Maybe a volleyball for venus and a softball would be appropriate. doing the whole solar system gets big. Neptune would be several dozens of kilometers away. But one thing that I find really cool is something much smaller. About 65 million years ago, a killer asteroid, a huge, monsterous object screaming through space impacted the earth and took out all the dinosaurs, half the plant life on Earth, and thousands upon thousands of species of life across the planet. How big a rock does it take to do all this? In our model, something the size of a grain of salt.
There are some great examples of scale solar systems that have been completed around the world. It’s my hope that using everyday materials is a very effective way of presenting the model. Explaining scale models using centimeters and ratios has its merits, but my guess is that using stuff that people interact with daily might have a sort of legacy. You tell me, though…next time you ask to pass the salt, is there a chance you might start thinking about the asteroid that made dinosaurs extinct and feel a little more fascinated about astronomy? I hope you will.
Thanks for listening, I hope you learned something and had a little fun. Until next time, this is Robert Berthiaume wishing you all clear skies and good times.
End of podcast:
365 Days of Astronomy
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