Looking up into the early evening skies tonight, in the southwest, one may see nothing but some stars, a moon, and a couple planets. But it won't take more than a minute for those who can see patterns to notice that there is something more going on here.

Right after sunset, in the 5 o'clock hour, look to the southern skies and see that the sun, Moon, and two bright dots form a sort of line across that part of the sky. The two bright dots are the superbright Venus, and dimmer Jupiter, nearer the Moon.

Notice also, in the next couple days, how the Moon seems to extend that make-believe line out across the southern skies. And, if they were bright enough, you would observe that both Neptune and Uranus are on that same line, over towards the southeast.
This imaginary line that circles the earth is called the ecliptic. Hugging this line one can find all the planets, the sun, and the
Moon. You will never find any of these solar system objects straying more than a few degrees from it.

What is this line? And what does it mean?

Pretend your favorite crazy uncle is in the middle of a lake, just bobbing gently up and down, dressed in an oversized, inflatable yellow bathing suit and pretending to be a sun. Around him at various distances are tiny family members, including you, swimming around him. None are flying overhead, none are diving below; they are all stuck on the same flat plane, the surface of the lake. From your perspective as a wannabe planet, your uncle and all the other wee swimmers around you can all describe a giant encompassing circle.

That is analogous to what our solar system is like. Only the planets are not floating on a lake to keep them all nicely leveled. But they are all on a disk-like plane on their trip around the sun. Why are they all that way? Here's what we think.

All those planets residing on the same plane going in the same direction is strong evidence that they all formed from the same whirling cloud of dust and gas sometime in the distant past. We see similar flattened disks choked with dust and gas around distant baby stars implying planets may be forming there now as you are reading this.

That ecliptic is not just pretty cosmic geometry; it is evidence for how it all started.

Until next time, clear skies!