When Today is Tomorrow

Tomorrow, Alrica and I are leaving Puebla. And then we are going to do something we've never done before. We're going to cross the International Date Line. It's true, we've been to East Asia before and to Australia. But when we did that in our travels with the kids, we traveled east to get there. (We left Sofia, Bulgaria and flew into Osaka, Japan. Though along the way we had a big layover in Doha, Qatar and another layover in Tokyo, Japan. You can read about that and about my big feet in a post from June 2016 linked here.)

But here's my confusing question. Are we crossing the International Date Line tomorrow? Or are we crossing it the day after tomorrow? There is one reason that I don't know enough to answer this and another reason that even if I knew enough, my answer could, in a sense, be wrong no matter what answer I gave.

That was about as confusing a paragraph as I could have written. So let me clarify.

The first point is this: I don't know when we will cross the International Date Line. We have a very long layover in Los Angeles. We won't fly out of LAX until just a few minutes before midnight. So from the point of view of California, there is no way we will reach the International Date Line on Wednesday.

But, keep in mind, we will be flying west. That means we are flying back in time. (On the clock, not time travel.) We're going against the spin of the Earth, moving into time zones that will be, when we take off, even further from midnight, earlier. Now, if you think of the plane traveling in a straight line southwest across the Pacific (it is heading to Singapore) then it seems clear that we won't reach the International Date Line before midnight, whatever the local time is. The plane can't possibly fly faster than the rotation of the Earth, right?

But I have another "keep in mind" for you: A straight line on a flat map is not the path a plane takes. The shortest distance between any two points on a globe is an arc of a great circle. This means the plane will take some path that would look like a curve on a flat map. I looked it up, and it is a curve on the flat map, which looks like it goes northwest first and then southwest. But it does not go over the west coast of the USA, nor does it go over Alaska. It doesn't even go over Japan, but it will go right over the Philippines. But the point is that as you go closer to either the North Pole or the South Pole, time zones are a lot narrower east to west. So it would be possible for a plane to go faster than that bit of the Earth was rotating.

In this particular case, I don't think we go that far north. So I suspect that from the local time on the clock point of view, it will already be early morning Thursday when we cross the International Date Line.

This brings up the second question. Should I say we cross it on Thursday? Or should I say we cross it on Friday? If you were in a boat just east of the International Date Line and you saw the plane go overhead, you would say that happened on Thursday. But if you were in a different boat (I don't know how you are in two boats at once) just west of the International Date Line and saw the plane pass overhead just a few minutes after the first boat, you would say that happened on Friday.

Normally, when you cross a time zone line, your clock jumps ahead or back by one hour. But in this instance, the clock is going to jump ahead 23 hours! So I suppose there is a chance, albeit small, that we could be crossing on Thursday on both sides! If it were between midnight and 12:59 AM Thursday from the point of view of the first boat which is east of the International Date Line, then it would be between 11:00 PM and 11:59 PM Thursday from the point of view of the second boat which is west of the International Date Line. (Oof, my head already hurts from thinking about this.)

Most likely, there is going to be a discrepancy between what the captains of the two boats would say when asked which day the plane passed overhead. So which answer is the right answer? i guess both.

I acknowledge that the International Date Line is one of those lines made up by humans. If you look at it on a map, you see it isn't even straight. Fortunately, the Pacific is vast and doesn't have a lot of large landmasses in it. But there are some, and so the line was drawn with zigzags to accommodate this. For example, the Aleutian Islands, part of Alaska, stretch into the Eastern Hemisphere. But no one wants part of Alaska to be on a completely different day that the rest of Alaska, so the date line stretches around the Aleutian Islands.

This Aleutian Island fact, by the way, is a bit of a sore point for me. I was in a trivia competition with my coworkers. The question asked which U.S. State was furthest north? Which was furthest south? Which was furthest east? And which was furthest west? Our team answered Alaska, Hawaii, Alaska, and Alaska. And the person running the contest counted us wrong saying the answer was Alaska, Hawaii, Maine, and Alaska. You don't get to argue with the trivia master, but he was WRONG! (For example, if you look up the longitude of Amchitka Island, Alaska, it is 179.0409 degrees EAST! That's way way way further east than anything in Maine. That's way further east than anything in China too.)

Okay, rant over. Back to the essence, the invention of time zones, which was a brilliant idea, necessitates that there be somewhere that two different days come together. There has to be one line which, when crossed, changes your clock by 23 hours. So the International Date Line is all tied into how we keep track of time. (Which is also invented by humans. I mean, the 24 hour solar day is a real astronomical phenomenon, but that we broke that into 24 pieces, well, that was a human idea.)

When we crossed the Tropic of Capricorn in Namibia, I got a picture of the kids and I at the sign. (And wrote a blog post about it.)

Adorable children at an exciting location

When we visited the Equator in Ecuador, I got a picture of Alrica and I at the line. (I wrote a blog post about that too.)

Ripped apart by the Coriolis effect?

Clearly, I am not going to be able to get a picture of myself at the International Date Line. Because, I will be on a plane, yes, but also, it's water there. And I doubt there's a sign or a painted line. Those wouldn't hold up well in seawater.

I know people say "Pics or it didn't happen." But this time, it is going to happen. And for some irrational reason, I'm excited to be able to say I crossed the International Date Line.