{"id":23,"date":"2011-01-02T00:00:09","date_gmt":"2011-01-02T00:00:09","guid":{"rendered":"http:\/\/www.skycaramba.com\/blog\/?p=23"},"modified":"2011-02-22T04:25:22","modified_gmt":"2011-02-22T04:25:22","slug":"a-planet-stops-in-its-tracks","status":"publish","type":"post","link":"https:\/\/www.skycaramba.com\/blog\/2011\/01\/02\/a-planet-stops-in-its-tracks\/","title":{"rendered":"A planet stops in its tracks"},"content":{"rendered":"

For the week ending January 8, 2011<\/em><\/p>\n

Here\u2019s your chance to see a planet stop in its tracks and turn around. Well, not really. It\u2019s an illusion of perspective, like telephone poles next to the highway going by real fast while a hill out in the distance seems to go by real slow.<\/p>\n

Saturn will be in Virgo all year. But it\u2019s not holding still. Now until around January 22nd<\/sup>, you\u2019ll get to see Saturn heading eastward as it slows down, virtually stops, and begins going westward. The ringed planet will continue that apparent westward motion until the first week in June when it has a rendezvous with a star named Porrina. And then, you\u2019ll get to see Saturn slow down, stop, and reverse direction again.<\/p>\n

When you see a planet going eastward from night to night, it\u2019s in direct<\/em> or prograde<\/em> motion. That\u2019s an astronomer\u2019s way of saying the object is going in the direction it\u2019s supposed to. When it goes westward, it\u2019s in retrograde<\/em> motion. And for a few nights, when it\u2019s slowing down to change direction, the object is said to be stationary<\/em>.<\/p>\n

If you could stand somewhere outside the solar system and watch the planets going around the sun, you\u2019d see that each follows a path like a car goes around a race track. They speed up and slow down just a little as they make their circuits. But the only changes in direction are the continuous turns they make on the way around. They don\u2019t start off counterclockwise, stop, then go clockwise.<\/p>\n

The illusion of planets going stationary and going through retrograde motion happens because we don\u2019t have the up close perspective of a racing fan by the track. Imagine how things might look though if you could look at the race track edge-on from far away. The cars would be zipping back and forth, but you wouldn\u2019t see that they\u2019re going around anything. The distance would force your observation into a two-dimensional view. That\u2019s sort of what happens to us as we look at the night sky and see planets going back and forth.<\/p>\n

This month Saturn rises around midnight. If you look then, you\u2019ll see it in the east. If you wait a few hours (looking closer to sunrise), you\u2019ll see Saturn and Virgo higher in the sky. If you watch from night to night, you\u2019ll see Saturn slowing down almost to a halt in the middle of Virgo. Binoculars may help you appreciate this spectacle better, because you\u2019ll be able to see the dimmer stars that Saturn is moving in front of.<\/p>\n

The same illusory change of motion happens with all the planets. The race track analogy isn\u2019t complete without telling you this: we\u2019re looking upon the other planets not like a far off observer would look at the race track, but like a race car driver would look upon the other race cars in the race.<\/p>\n

Except, of course, we can take time to enjoy that view because we don\u2019t have to watch where we\u2019re going.<\/p>\n","protected":false},"excerpt":{"rendered":"

Well, not really. It’s an illusion of perspective.<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[1],"tags":[62,63,64,614,65],"_links":{"self":[{"href":"https:\/\/www.skycaramba.com\/blog\/wp-json\/wp\/v2\/posts\/23"}],"collection":[{"href":"https:\/\/www.skycaramba.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.skycaramba.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.skycaramba.com\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.skycaramba.com\/blog\/wp-json\/wp\/v2\/comments?post=23"}],"version-history":[{"count":6,"href":"https:\/\/www.skycaramba.com\/blog\/wp-json\/wp\/v2\/posts\/23\/revisions"}],"predecessor-version":[{"id":59,"href":"https:\/\/www.skycaramba.com\/blog\/wp-json\/wp\/v2\/posts\/23\/revisions\/59"}],"wp:attachment":[{"href":"https:\/\/www.skycaramba.com\/blog\/wp-json\/wp\/v2\/media?parent=23"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.skycaramba.com\/blog\/wp-json\/wp\/v2\/categories?post=23"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.skycaramba.com\/blog\/wp-json\/wp\/v2\/tags?post=23"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}