Cheap Astronomy - Dear CA #109: Planets

Things that orbit the Sun and clear their orbits. Dear Cheap Astronomy – What happens when worlds collide? The outcome of a collision between two planets depends on the speed of the collision, the angle of the collision and the relative masses of the two bodies and their composition – think rocky planets versus gas giants for example. A small planet approaching a large planet slowly might get tidally stretched and break up into pieces, but a fast moving one might impact before there’s been time for gravitational stretching to break it up.   Dear Cheap Astronomy – Why is Mars’ sky red? A good place to start is to think about the colours we are familiar with in Earth’s sky. In the middle of the day, the overhead Sun is a bright white disk you can’t look at directly and the rest of the sky is blue. This is because most of the visible light from the Sun passes straight through the atmosphere, which is transparent to those wavelengths, except at the very short end – so rather than passing straight through, photons in the blue and violet parts of the visible spectrum are scattered – meaning they are deflected off their straight line path and bounce around a lot, although most eventually reach the ground.   We've added a new way to donate to 365 Days of Astronomy to support editing, hosting, and production costs.  Just visit: https://www.patreon.com/365DaysOfAstronomy and donate as much as you can! Share the podcast with your friends and send the Patreon link to them too!  Every bit helps! Thank you! ------------------------------------ Do go visit http://www.redbubble.com/people/CosmoQuestX/shop for cool Astronomy Cast and CosmoQuest t-shirts, coffee mugs and other awesomeness! http://cosmoquest.org/Donate This show is made possible through your donations.  Thank you! (Haven't donated? It's not too late! Just click!) ------------------------------------ The 365 Days of Astronomy Podcast is produced by the Planetary Science Institute. http://www.psi.edu Visit us on the web at 365DaysOfAstronomy.org or email us at [email protected].