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David Hall
2002-Jan-01, 08:29 AM
Interesting New York Times article today. It says that NASA research indicates that the human body can't adjust to even small changes to the 24 hour clock. This leads to fatigue problems and forbodes difficulties in space travel.

http://nytimes.com/2002/01/01/health/anatomy/01TIMI.html
(As usual, the NYT requires registration before viewing.)

GrapesOfWrath
2002-Jan-01, 09:55 AM
Didn't some of the original studies about diurnal sleep patterns (where they let people find their own pattern, without clocks, in a cave) find people tended towards 25 or 26 hour patterns? That seems to be at odds with those results.

The article says all the tests were done in low light conditions, and the non-24 hour cycle participants could not adjust their melatonin levels into sync. Hey, turn up the lights occassionally.

David Hall
2002-Jan-01, 01:51 PM
Yeah, I was wondering that too. I've read in other places that exposure to strong light 'resets' our body clocks. There may be more going on here than discussed in the article itself.

GrapesOfWrath
2002-Jan-02, 01:48 PM
Here is a short article from circadian.com (http://www.circadian.com/learning_center/biological_clock2.htm) that claims the natural human body clock is set at 25 hours, as has been verified from experiments in caves, and the Sun daily resets our clock to 24 hours. I remember scientific studies from 25 or 30 years ago, but I couldn't find a cite immediately.

But I did find this: Lackner, J. R., & Dizio, P. (1998). Gravitoinertial force background level affects adaptation to coriolis force perturbations of reaching movements. Journal of Neurophysiology, 80, 546-553. Are they saying that the Earth corliolis force affects our reach, or is it an artificial induced corliolis?

aurorae
2002-Jan-02, 08:25 PM
On 2002-01-01 08:51, David Hall wrote:
Yeah, I was wondering that too. I've read in other places that exposure to strong light 'resets' our body clocks. There may be more going on here than discussed in the article itself.


People that use bright lights to reset their internal clock, usually use them for an hour or so, and usually in the morning. The light seems to tell the body that that it is morning and time to be awake.

But shift work, and spending the night in a brightly lit environment, can mess up internal clocks and also cause other health problems. Here's an article on this from the National Cancer Institute:

http://www.jnci.oupjournals.org/cgi/content/abstract/93/20/1557

I've thought about my brightly lit neighborhood. I addition to trying to get the City Council to pass a lighting ordinance that requires full cutoff shielding (which could reduce costs and also improve astronomy), I've also installed double curtains on my bedroom window.

2002-Jan-02, 09:21 PM
On 2002-01-02 08:48, GrapesOfWrath wrote:
Here is a short article from circadian.com (http://www.circadian.com/learning_center/biological_clock2.htm) that claims the natural human body clock is set at 25 hours, as has been verified from experiments in caves, and the Sun daily resets our clock to 24 hours.


I have read that in several places, too. No explanation was given for why it was 25 hours instead of 24 hours. However, it was apparently reproducible.

I have a correlation, but no explanation. The 25 hour day corresponds closely to a lunar day. That is, if you are looking straight upward at the moon, you won't see it in the same position until about 25 hours have past. Similarly, tides tend to go in and out every 12.5 hours. The geography of the sea floor does shift the absolute time of the tides, but not the period.

In terms of evolution, or any other teological theory, there could be an adaptive value to being on a circidian rhythm that matched the lunar day.

As an additional correlation, the menstrual period averages once every 28 days. I know that the menstraul cycle varies alot. Yes, I know about women who live together synchronizing their periods. However, on average it is 28 days, the length of a true lunar month.


In terms of evolution, or any other teological theory, there could be an adaptive value to being on a menstrual cycle with a period of one lunar month. Perhaps it is related to the adaptive value of a 25 hour day.

Can anyone suggest some adaptive values for such behavior-correlations with the moon in human history?


<font size=-1>[ This Message was edited by: Rosen1 on 2002-01-02 19:43 ]</font>

aurorae
2002-Jan-02, 10:07 PM
On 2002-01-02 16:21, Rosen1 wrote:
I have read that in several places, too. No explanation was given for why it was 25 hours instead of 24 hours. However, it was apparently reproducible.


Well, the Earth used to spin faster, so the days would have been shorter, right?

So that doesn't seem to explain this at all.

Never mind.

Oh, for those looking for any information on light pollution, try:

http://members.aol.com/ctstarwchr/LiteLynx.htm#index




<font size=-1>[ This Message was edited by: aurorae on 2002-01-02 17:07 ]</font>

GrapesOfWrath
2002-Jan-03, 11:03 AM
Another good site is the International Dark-Sky Association (http://www.darksky.org) webpage.

I'm not sure why the "true" lunar month would be more important than the apparent lunar month, which is a couple days longer.

ToSeek
2002-Jan-03, 01:40 PM
On 2002-01-02 16:21, Rosen1 wrote:
I have read that in several places, too. No explanation was given for why it was 25 hours instead of 24 hours. However, it was apparently reproducible.


It's because we're originally from Mars!* /phpBB/images/smiles/icon_wink.gif




*Believe it or not, some people actually think this is so.

jkmccrann
2005-Oct-21, 02:22 PM
Yeah, my cousin's got a condo up on Olympus Mons if you're in the area!