This seems like a very simple question. But as this video from vsauce shows, it’s anything but. This goes into things way past my middle school classroom, including general relativity, spacetime, and geodesics. Things are simplified in middle school, and it’s still a difficult thing for kids to get. More below the video.
In middle school we’re more interested in the Newtonian view rather than the spacetime view. For us, down is towards the center of the Earth. It’s the same for people on the other side of the Earth (say in Australia (I’m in New Jersey, USA)). For them, down is still towards the center of the Earth, but that’s in a different direction. My down and their down point in close to opposite directions. That’s because the concept of “down” is a local direction, not a universal one. My down is different from the down of my friend who lives in New Zeeland. This can be a difficult thing for 13 year olds to understand. It helps to show it on a globe, with little stick figures drawn on a folded up sticky notes.
NASA’s Kepler satellite has found an Earth size planet in its star’s Goldilocks Zone. This is the first habitable zone Earth size planet found so far; all the previous ones were much larger than Earth. Kepler-186f orbits a star about 500 light years away in the constellation Cygnus. The star (Kepler-186) is an M class red dwarf. The planet is on the outside of the habitable zone, so it’s probably fairly cold, but that really depends on the atmosphere. So far all we really know about the planet is that it’s just a little larger than Earth, and is probably rocky (not a gas giant). Due to its orbit close to the star, it probably has a long day, as long as our week or month.
Kepler-186f orbital characteristics
Update 21 April 2014
This link on How close are we to finding extraterrestrial life? has some good notes on the types of planets Kepler has found and how new telescopes will help the search.
We’re finally back to the moon. The Chinese have sent a lander to the moon. Congratulations! I’m glad we’re back; I just wish it hadn’t taken so long.
At 8:11 AM EST, the Chinese moon lander Chang’e 3 and rover soft landed on the moon in the Bay of Rainbows map here. This is the first soft landing in 37 years. Chang’e 3’s solar panels have been deployed, and soon the Yutu rover will roll out.
Also, on this date back in 1972, Gene Cernan left the last footprints on the moon from Apollo 17. And, back in 1546, Tycho Brahe was born.