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February 12, 2014 / BTM

Fingerprint #3: Earth is Designed For Life!

final earth fingerprintYesterday I posted about some of what we’re learning about how special earth’s position and composition are to supporting life.   To help our kids understand some of what we’d learned, we created a model solar system.  I found that having a model to illustrate what I was telling them helped our kids to better understand some slightly difficult topics.  And after years of fading, our 8 year old still loves it and wants it to hang in his room.


When I started this activity, I didn’t realize that paper maché was so time consuming.  It took us days to complete this activity, which wasn’t my plan!  If you’d like to do something like this, but don’t have a ton of time, consider using balloons, cutting out coloured pieces of paper, or painting foam balls (find them at craft stores) for your planets.  You can find a lot of instructions for how to make a solar system on google, so I won’t repeat them here.  One thing we added to ours, however, was our moon as it plays an important role in helping Earth to host life.

solar system pict

We hung our planets from two separate metal rods (which are unravelled coat hangers).  Ideally, you’d have each planet hang from its own metal rod so you can show how each orbits the sun separately, but I couldn’t figure out how to make that work easily enough.  We hung the ‘inner planets’ on one rod and the ‘outer planets’ on the other.  This is because the inner and outer planets play slightly different roles, and I wanted to be able to illustrate how the asteroid belt encircles earth to protect it.

With a physical model to use,  you can explain and illustrate some of the major scientific discoveries about how many factors combine to protect earth and its inhabitants, such as:

– why you need planets that move in circular orbits.  You could ask what would happen if Earth got too close to the sun (it would get too hot and boil off our oceans), or too far from the sun (the opposite), or didn’t move in a circular orbit (it would crash into other planets or stars);

– the role that shielding planets play (to deflect collisions with comets and asteroids away from your inhabited planet).  Use your model to show how Jupiter, Saturn and Uranus deflect comets by attracting them through their higher gravitational pull; and Mars and Venus shield us from asteroids.  The asteroid belt also provides us with shielding;

– how our sun is very unique.  It is one of the biggest stars in the galaxy, which means that it gives us enough light that we can be at a safe distance from it.  It also gives a perfect red/blue blend of radiation is which optimal for photosynthesis.  If our sun were a smaller star (like a red dwarf), we would have to be closer to it because it wouldn’t be as bright and that would make the earth too hot for life;

– how our moon controls the tilt Earth’s axis and creates tides that keep large-scale ocean circulation operating

One other thing you could illustrate to your kids does not require the solar system model.  You could show them a spiral galaxy (here is an example) and point out how Earth and its solar system are nestled midway between the spiral arms, as well as midway between the inner and outer regions of the spiral galaxy.  This is the safest place to avoid getting hit by other planets or exposed to explosions or hazardous gases that would kill life on earth.

I recommend again this video by the authors of Privileged Planet to give you more background information so that you can teach your kids some of the science we’ve learned about Earth’s privileged place in the universe.  I hope you have fun!

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