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What time is it on the north pole? I mean, suppose I lived in Texas and I traveled straight north until I reached the north pole. I would look at my watch and determine what time I had arrived. But suppose just as I was mouthing the words, someone from New York arrived and said it was one hour later. And then I spin around and notice someone from California checking her watch, and she says it's two hours earlier. And then, because in hypotheticals like this anything is possible, someone from each of the 21 other time zones comes trudging up peering intently at his or her watch. Naturally, an argument ensues, but the results are inconclusive, basically on account of its being conducted in several languages. Who is right? --Ray A. Balestri, Dallas

Why, I am, Ray. I'm surprised you have to ask. Glad to get the north-pole situation cleared up, in any event, what with the S. Claus situation and all. As you rightly observe, polar timekeeping is a little weird, one of many anomalies arising from the imposition of a Cartesian coordinate system on a spherical surface (and how's that for slinging the ten-dollar terminology?). Polar joke: The winds at the south pole are very consistent--they're always out of the north! OK, so maybe it didn't make you spit out your soup, but they tell me it got big laughs at a recent colloquium of OAE's--Old Antarctic Explorers, as they coyly call themselves.

Although timekeeping reaches the point of crisis only at the poles, it's a hassle throughout the polar regions, since close adherence to the conventional time-zone system would require you to reset your watch every five miles on any jog through the ice fields. To avoid this, some clock of convenience is usually settled on. The nuclear submarine Nautilus kept Greenwich mean time when it sailed beneath the polar ice cap in 1958. (The commander of the vessel described the journey in a book entitled Nautilus 90 Degrees North, the title referring to yet another Cartesian oddity: the poles are the only places that can be definitely located with a single number, as opposed to the usual two for latitude and longitude. Babes are always impressed when you tell them this at bars.)

Most U.S. antarctic facilities keep New Zealand time, since NZ is the supply point. A geologist who's done fieldwork in the antarctic says his team occasionally shifted the schedule 12 hours so that during the "day" (this is the land of the midnight sun, remember) they'd be in the sun rather than the much colder shadow when working on a south-facing slope. You'll have to think a bit to understand why this is so, a useful exercise under any circumstances.

WHY YOUR EYES LIGHT UP

Regarding kaleidoscopic eye patterns [October 29], pressing your eyes with the heels of your hands does not produce "random nerve firing" as you state. Rather, it raises your intraocular pressure until it matches or exceeds the pressure in your retinal artery, at which point blood flow to your retina and the tip of your optic nerve ceases. (This is called ischemia.) When this happens, nerve impulses also cease flowing toward neural relays further back in your brain. Thus unconstrained (technically, "released") by sensory input, these higher relays take on a life of their own and generate the patterns you describe.

I hate to be a wet blanket, but pressing your eyes may precipitate blindness in older individuals with glaucoma or atherosclerotic vessels. Normal intraocular pressure is under 20mm Hg, while mean arterial pressure is about 100mm Hg. If the latter pressure is maintained for more than a few seconds in order to "watch the light show," the risk of retinal infarction (permanent death of retinal ganglion cells) swiftly increases in individuals of any age. Eyeball rupture is also a possibility, especially in individuals who have had eye surgery. My advice is that if you're under 50, don't do this beyond five seconds. --Richard Cytowic, MD, Washington, D.C.

If I understand you, Richard, I should have said "random neural relay firing" rather than "random nerve firing." I burn with shame at this error and promise not to let it happen again.

Art accompanying story in printed newspaper (not available in this archive): illustration/Slug Signorino.

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