In the last 40 years, astronomers have gathered more and more evidence that our moon came out of a scarcely-imaginable collision between a baby (100-million-year-old) Earth and another proto-planet named Theia. (Watch this video for a good explanation.) Just two weeks ago, astronomers at UCLA announced a clarification: Theia didn't hit Earth in a glancing blow, as previously thought. Instead, the two planets hit head-on:
“We don’t see any difference between the Earth’s and the moon’s oxygen isotopes; they’re indistinguishable,” said Edward Young, lead author of the new study and a UCLA professor of geochemistry and cosmochemistry.
The fact that oxygen in rocks on the Earth and our moon share chemical signatures was very telling, Young said. Had Earth and Theia collided in a glancing side blow, the vast majority of the moon would have been made mainly of Theia, and the Earth and moon should have different oxygen isotopes. A head-on collision, however, likely would have resulted in similar chemical composition of both Earth and the moon.
“Theia was thoroughly mixed into both the Earth and the moon, and evenly dispersed between them,” Young said. “This explains why we don’t see a different signature of Theia in the moon versus the Earth.”
So why am I reviewing catastrophic astronomical events? I'm reading Neal Stephenson's latest novel, Seveneaves, which posits (in its opening paragraph) the collision between our moon and what is probably a small black hole. Stephenson imagines what would happen from a serious, scientific perspective.
Seveneves isn't what you would call a character piece. I'm 45% through it, according to my Kindle, and thoroughly fascinated. But Stephenson is almost the anti-Ishiguro.
Another aside: I have to see the tidal bore in the Bay of Fundy someday. It just sounds so cool—especially in context.
This means I have some time to digest this over the weekend:
I might have a chance to read this weekend. Perhaps.
Here's the semi-annual Chicago sunrise chart. I'm posting it as a regular post in addition to posting it as a permanent page, to maintain deep-linking archiving. The previous post was here.
In just a few hours we'll see the latest sunrise of winter, until the days just before the change back to Standard Time in November. That will bring us something really rare: the latest sunrise in Chicago until November 2027, at 7:29am on November 6th. Thank leap years and orbital eccentricity for that. This statement holds true in all parts of the U.S. and Canada that observe daylight saving time until the first Sunday in November. The worst place to be that morning will be in the U.P. of Michigan, where the sun won't rise until after 8:30am. That's almost British.
||Latest sunrise until Oct 28th
||Earliest sunrise until Apr 17th
Earliest sunset until Oct 24th
||Daylight saving time begins
Latest sunrise until Oct 16th
Earliest sunset until Sep 18th
||7am sunrise, 7pm sunset
|| Equinox 23:30 CDT
||6:30am sunrise (again)
||Earliest sunrise of the year
|| Solstice 17:34 CDT
||Latest sunset of the year
||Equinox, 9:21 CDT
||Latest sunrise until 6 Nov 2027 (!)
Latest sunset until Feb 27th
||Standard time returns
Earliest sunrise until Feb 26th
||Earliest sunset of the year
||Solstice, 04:44 CST
You can get sunrise information for your location at wx-now.com.
...this app might be fun. CityLab explains:
Floating in space among the stars and planets are more than 2,250 satellites and “space junk” traveling at up to 18,000 miles an hour. Some are large enough to be seen with the naked eye—though you’d have to first figure out which ones are within your line of sight.
Luckily, there’s a map for that now, by Patricio Gonzalez Vivo, a graphics engineer at Mapzen who has a knack for turning pure data into mesmerizing visuals (like this one of New York City). His latest project, Line of Sight, traces the orbital path of more than a thousand of those satellites and predicts their current location using open-source data from tracking sites like CelesTrak andSatNogs. Plug in your address (or choose one of the pre-selected cities) to see if there are any satellites—shown as yellow dots—nearby. Or zoom out to watch all the satellites orbit the Earth at once in a dazzling visualization.
His city visualizer is also really cool.
A G3-class solar storm (i.e., a big one) is predicted to hit the earth tonight, generating category 7 aurorae, which are rarely seen on earth:
Auroral activity will be high(++). Weather permitting, highly active auroral displays will be visible overhead from Inuvik, Yellowknife, Rankin and Igaluit, to Portland OR, Cheyenne, Lincoln, Springfield, and New York City, and visible low on the horizon as far south as Carson City, Oklahoma City, and Raleigh.
Here's the prediction map from the University of Alaska at Fairbanks:
But here's the observed aurora right now:
So, while the aurora isn't yet visible in Chicago, the solar storm might propel enough material into our ionosphere that we could see some auroral displays in a few hours—or tomorrow. The prediction for Tuesday calls for displays overhead central Wisconsin which would be visible down to St. Louis, weather permitting.
The only place in Chicago dark enough to see them is the lakefront. Parker and I might have to walk over there tomorrow evening.
Updates as events warrant...
If you live in the parts of the U.S. and Canada that observe Daylight Saving Time, don't forget to move your clocks back an hour tonight. It couldn't come soon enough, though this is the soonest it can come under the 2007 changes to DST observance.
This morning's 7:22 sunrise in Chicago is the latest we'll have to endure until next November 1st, but tonight's 5:47 sunset is the latest we'll get to have until March 6th. Tomorrow the sun rises at 6:23 and sets at 4:45, as our available daylight shrinks from 10 hours, 24 minutes today down to 9 hours, 7 minutes on December 21st.
I'm not a fan of the 2007 changes. I like switching to DST in the spring and switching back in the fall, but I also believe that mid-October (or even the end of September as they do in Europe) makes a lot more sense. At least mornings aren't so gloomy in the fall. (Not a lot we can do about the post-7am sunrises from December 2nd through February 5th, but we expect those two months to be gloomy.)
Of course, I'm not in Chicago at the moment, and it's plenty sunny here...
The weather in Chicago cleared up enough that we got a great view of the total lunar eclipse last night:
For comparison, here is the full moon when Earth doesn't get in the way:
Note that it's a lot harder to photograph the moon when it's eclipsed. The full moon reflects 9% of the light falling on it, or about half as much as a standard gray card or green grass. So when shooting the moon, the correct exposure is surprisingly fast: about 1/250 at f/5.6 at ISO 100. Shooting the eclipse last night, I used 1/10 at f/5.6 at ISO-25600. And a tripod.
OK, so, astronomers predicted tonight's lunar eclipse about 6,000 years ago, but it was still bloody cool. I'll have photos tomorrow. Meanwhile, I am happy the clouds over Chicago parted long enough that I could see one great rock cast a shadow on another. It happens every six months, I realize, but it won't be visible again in Chicago for many years.
WGN's Tom Skilling is optimistic about seeing Sunday night's eclipse:
While the first vestiges of Sunday evening’s full moon will begin at 7:40pm, the partial eclipse stage is to be reached at 8:07 pm Chicago time moving toward the “total eclipse” phase at 9:11pm. The disc of the moon will take on a dim rusty-red cast in the total eclipse phase for 1 hour and 12 minutes (through 10:23pm Sunday evening). The partial eclipse phase is to be reached at 11:27 pm and the eclipse ends at 11:55 pm.
The early read is that the weather is going to cooperate in viewing the event from Chicago and the Midwest. Here, from the National Weather Service’s GFS forecast model is a forecast of the likely location of cloud cover at differing heights–and, finally, a composite of potential total cloud cover at 7pm CDT Sunday.
Here is the GFS model’s total cloud cover prediction. Sunday is likely to be an unseasonably mild late September day with brisk southerly winds likely to boost daytime temps across the VChicago area to around 80-degrees and to limit nighttime lows to the 60s.
Here's hoping. It should be an epic eclipse.
I hope Chicago has decent weather for the full moon 11 days from now:
It's coming Sept. 27 at 9:47 p.m. CDT.
For starters, it is what some astronomy enthusiasts call a "super" moon because it will occur when the moon is close to perigee, its nearest point to Earth in its elliptical orbit.
The moon reaches perigee Sept. 28, and it will be just more than 222,000 miles away at the time of the full moon. That is about 31,000 miles closer than lunar apogee, the moon's farthest point in its orbit.
The moon appears about 14 percent bigger and 30 percent brighter at perigee than it does at apogee, according to NASA. But it doesn't look dramatically different to the naked eye.
The full moon also comes with a full lunar eclipse, all of which will be visible from the eastern half of the United States, including Chicago. Such eclipses can give the moon a reddish tint, caused by light bending through Earth's atmosphere.
Here's the official NASA page showing just how disappointed we'll be if it's cloudy in Chicago.