Greetings! I hope that you all recall our dear friend Johannes Kepler, astronomer, astrologer, philosopher and all round nice guy. He was the smart gentleman who brought us three laws of planetary motion.
The first we covered in depth in class – the law of ellipses relating to any object orbiting the sun is orbiting in an elliptical shape (a squished circle), with the sun at one focal point.
Each one of you knows that, no matter what ‘shape’ a triangle is, it will always have 180degrees. With orbiting planets, the same rule applies, with one point of the traingle always the sun. Thi is Kepler’s 2nd law – that the orbit of a planet covers the same area in equal amounts of time. That means, the further away the planet from the sun the slower the orbit. The link below shows this in action.
And finally, Kepler presented a formula that allows us to calculate average distances from the sun based on orbital periods (and vice versa): The square of the orbital period is equal to the cute of the average distance to the sun —> T^2=a^3
So now you can go outside, armed with information when you stare up at the night sky. Of course, it helps to have a telescope and I’d recommend that if you’re ever in Sydney to pop into the observatory there – the sky will never look as impressive!
Wishing you all the best of luck in your exams, may the stars shine brightly on you!
http://www.physicsclassroom.com/class/circles/u6l4a.cfm <– this one will help with the understanding of the 2nd law
http://www.youtube.com/watch?v=WTJa8DXlerc (i apologise for the high pitch of this woman’s voice – but seriously – applying songs to your work makes it to remember!)
http://galileoandeinstein.physics.virginia.edu/more_stuff/flashlets/kepler6.htm <– this is a challenge for anyone who wants to get planets to orbit…
http://antwrp.gsfc.nasa.gov/apod/astropix.html <– astronomy picture of the day – cos really, what is astronomy if not beautiful!