The Daily Parker

Politics, Weather, Photography, and the Dog

Latest dawn in years

This morning's sunrise in Chicago, at 7:26, will be the latest until 6 November 2021. It is not the latest possible sunrise; that would be the one we'll have at 7:29 on 6 November 2027 (and had on 5 November 2016).

I do not really understand the law passed in 2007 that moved our return to standard time from October to November. Who wants to wake up before dawn? Not me.

Tomorrow the sun rises at 6:28. (I will probably do the same around 8.)

Falling into the sun is hard

In the geocentric model of how things work, it's really easy for you to fall directly toward Earth. This happens because you are already moving fast enough to have a very small delta vee with the surface at any particular moment. Not so falling into the sun, which is so hard, we only just launched the first probe that can do it on purpose:

The reason has to do with orbital mechanics, the study of how natural forces influence the motions of rockets, satellites, and other space-bound technology. Falling into the sun might seem effortless since the star’s gravity is always tugging at everything in the solar system, including Earth. But Earth—along with all the other planets and their moons—is also orbiting the sun at great speed, which prevents it from succumbing to the sun’s pull.

This arrangement is great if you’d like to avoid falling into the sun yourself, but it’s rather inconvenient if you want to launch something there.

“To get to Mars, you only need to increase slightly your orbital speed. If you need to get to the sun, you basically have to completely slow down your current momentum,” says Yanping Guo, the mission-design and navigation manager for the Parker Solar Probe. Based at the Johns Hopkins Applied Physics Laboratory, Guo has been working on the probe for about 17 years.

Probes bound for deep-space destinations like Mars can piggyback off Earth’s momentum to fly faster. For a spacecraft to launch toward the sun, on the other hand, it must accelerate to nearly match the Earth’s velocity—in the opposite direction. With the planet’s motion essentially canceled out, the spacecraft can surrender to the sun’s gravity and begin to fall toward it. But this is almost impossible with current rocket technology, so spacecraft have to get some help, in the form of slingshot maneuvers off other planets, called gravity assists.

Douglas Adams, therefore, was partially correct: generally speaking, if you throw yourself at the sun, you will miss (and wind up in a stable orbit). NASA has just started the process of hitting it.

That's not a moon, that's a--wait, no that's a moon

Astronomer Scott Sheppard has discovered 10 more moons orbiting Jupiter, bringing the gas giant's coterie up to 79:

Sheppard found them with the help of a ground-based telescope in Chile that had recently received an upgrade: a camera made for scanning the night sky for very faint objects. Sheppard was looking for Planet Nine, the planet some astronomers believe lurks somewhere at the edge of our solar system, jostling the orbits of other objects in strange ways. As the telescope gazed in the darkness way beyond Pluto, it ended up catching something much closer: a flurry of glinting, tiny objects near Jupiter, the smallest of which was about half a mile wide.

Sheppard couldn’t say whether these points of light were actually moons, at least not right away. To determine whether something is indeed a moon, astronomers must track the object for about a year to determine that, yes, its motions are governed by the gravitational tug of a planet. Sheppard says he couldn’t get excited about his findings in earnest until he observed the objects again a year later, this past spring, and his suspicions were confirmed.

If you came to this story expecting to find dazzling, close-up images of Jupiter’s newly discovered moons, we have some bad news: The era of discovering massive worlds around the gas planet ended more than 400 years ago, with Galileo. Like this latest batch, many of the moons astronomers have discovered around Jupiter in the past several decades have been smaller than cities. Their minuscule size has prompted some astronomers, including Sheppard and Williams, to wonder whether they should even bother giving them names. Williams says that discoverers of moons don’t have to name them if they don’t want to. Sheppard suggests perhaps it’s time to add another layer to our definition of a moon. “The definition of a moon is just anything that orbits a planet, so maybe once you start getting down to a kilometer or so in size, maybe we should start calling these things dwarf moons,” he says.

Now they just have to name all of them...

California may move to UTC-7 year-round

Governor Jerry Brown approved AB 807, which would put to the voters in November an initiative to go to "year round Daylight Saving Time:"

Wrote Brown in a signing message: "Fiat Lux!" (Let there be light.)

Assemblyman Kansen Chu, D-San Jose, who authored Assembly Bill 807, has called the practice of changing clocks twice a year, in the fall and the spring, "outdated." He argues altering the time by an hour has adverse health affects, increasing chances for heart attacks, workplace injuries and traffic accidents.

The ballot measure would overturn a 1949 voter-approved initiative called the Daylight Savings Time Act, which established Standard Pacific Time in California.

Should voters approve the ballot measure, the Legislature would then decide how the state's time should be set. Congress would have to sign off on Chu's main goal of establishing year-round daylight saving time.

If it passes, L.A. and San Francisco would see sunrises at 7:44 and 8:09, respectively. But sunsets would be 17:44 and 17:51. So...if you live in California, how would you vote?

Busy weekend; lunchtime reading

This past weekend included the Chicago Gay Pride Parade and helping a friend prepare for hosing a brunch beforehand. Blogging fell a bit on the priority list.

Meanwhile, here are some of the things I'm reading today:

Back to debugging service bus queues...

The Athropic Shadow

An article in this month's Atlantic points out that we humans can wonder how we got here only because we got here:

After all, there are 100-mile impact craters on our planet’s surface from the past billion years, but no 600-mile craters. But of course, there couldn’t be scars this big. On worlds where such craters exist, there is no one around afterward to ponder them. In a strange way, truly gigantic craters don’t appear on the planet’s surface because we’re here to look for them. Just as the wounds of the returning planes could reflect only the merely survivable, so too for our entire planet’s history. It could be that we’ve been shielded from these existential threats by our very existence.

“Observer selection effects are really the kind of effects where the data you get is going to be dependent, in some sense, on survival, or that you as an observer exist,” [Anders Sandberg, a senior research fellow at University of Oxford’s Future of Humanity Institute] says. “Now this gets really interesting and scary when we apply it to our own survival.”

“Maybe the universe is super dangerous and Earth-like planets are destroyed at a very high rate,” Sandberg says. “But if the universe is big enough, then when observers do show up on some very, very rare planets, they’ll look at the record of meteor impacts and disasters and say, ‘The universe looks pretty safe!’ But the problem is, of course, that their existence depends on them being very, very lucky. They’re actually living in an unsafe universe and next Tuesday they might get a very nasty surprise.”

If this is true, it might explain why our radio telescopes have reported only a stark silence from our cosmic neighborhood. Perhaps we’re truly extreme oddballs, held aloft by a near-impossible history—one free from lifeless water world.

We see this on smaller scales when, for example, extremely lucky people start to think they succeeded entirely because of their own efforts. But that's a different topic. Sort of.

Florida votes to secede from the Eastern time zone

Florida's legislature has voted overwhelmingly to change the state's clocks:

The Florida Senate passed the Sunshine Protection Act on Tuesday, three weeks after the state’s House of Representatives, and sent it to Gov. Rick Scott for his signature or veto. (Asked on Wednesday whether Mr. Scott would sign it, and why or why not, his press secretary, Lauren Schenone, said only, “The governor will review the bill.”) The margins of victory in both chambers were overwhelming — 33 to 2 in the Senate and 103 to 11 in the House — and the measure has considerable public support.

The problem? Florida doesn’t have the authority to adopt daylight saving time year-round.

15 USC 260a allows states to adopt year-round standard time, but not year-round daylight saving time. The Department of Transportation is in charge of what states go in what time zones.

In any event, what the bill's sponsors really want, but didn't know how to ask for, is to move Florida from the Eastern time zone (UTC-5 standard and -4 DST) to the Atlantic time zone (UTC-4 standard), and then exempt the state from DST. The intent is simply to put Florida on UTC-4 year-round.

What would that look like, though? From mid-March to early-November, it would look exactly the same, since they're on UTC-4 when on Eastern Daylight Time. Sunrises in would occur between 7:30am mid-March and 6:30am mid-June, sunsets between 7:30pm mid-March and 8:15pm mid-June.

In the winter, mornings would be pretty dark, but there'd be a lot of evening light. The sun would rise just after 8am on December 21st, but set around 6:30pm. In Jacksonville, way up north, the sun would rise about 20 minutes later. But farther west, in Pensacola, the sun wouldn't come up until 8:45am on December 21st, potentially obviating any benefit of the sun setting close to 7pm.

Note that Pensacola, at 87°11' W, is almost due south of Chicago. Miami (80°17' W) is nearly due south of Pittsburgh. But Florida's latitude reduces the differences between summer and winter daylight hours, compared with what we experience farther north.

Should Florida move to UTC-4? It might not be a bad move, if having daylight extend later in the evening makes up for the later sunrises. It would not, however, actually change the astronomical reality of how many hours of daylight they get.

We'll see if the Department of Transportation or the U.S. Congress gives them the authority to hop.