I've Heard That The Earth's Rotation Is Slowing. How Long Until Days Last 25 Hours?

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Clock-Crazy: Trouble getting it all done in 24 hours? The day's not getting any longer: Bill Varie/Corbis

We could all use an extra hour in the day, but clocks won't need to be extended anytime soon. The time the Earth takes to make a complete rotation on its axis varies by about a millionth of a second per day, says physicist Tom O'Brian of the National Institute of Standards and Technology. While some days are shorter than average, the planet's rotation shows a long-term slowing trend, ultimately leading to a longer day.

Scientists have reliable data on the Earth's rotational speed, based on observations of the sun's position in the sky during solar eclipses, going back some 2,500 years. Although the rotational rate hasn’t declined smoothly, over that period the average day has grown longer by between 15 millionths and 25 millionths of a second every year. Even at the faster rate, it will take 140 million years before the Earth's rotation slows enough to necessitate a 25-hour day.

You don’t need to worry about having to add another day to your calendar, either. Although the planet’s rotation around its own axis is lagging ever so slightly, we’re revolving around the sun just as quickly as ever, and showing no signs of slowing down.

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dodeka

from Laurel, MD

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Actually, if the day gets longer and the year stays the same, we'll have to take a couple days OFF the calendar. We'd have longer days, but less of them. With a 25-hour day, we'd lose more than two weeks!

365 days/year X 24 hours/day = 8760 hours/year
350.4 days/year X 25 hours/day = 8760 hours/year

365 - 350.4 = 14.6 days

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dodeka

09/30/08 at 12:10 pm

Actually, if the day gets longer and the year stays the same, we'll have to take a couple days OFF the calendar. We'd have longer days, but less of them. With a 25-hour day, we'd lose more than two weeks!

365 days/year X 24 hours/day = 8760 hours/year
350.4 days/year X 25 hours/day = 8760 hours/year

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I believe you misinterpreted the last paragraph, the author is no longer referring to the Earths rotation of it's own axis (which affects the length of a day), but to that of the Earth relative to the sun(which affect the length of a year).

The authors comment :
"Although the planet’s rotation around its own axis is lagging ever so slightly, we’re revolving around the sun just as quickly as ever, and showing no signs of slowing down."

Meaning, if the earth-sun rotation doesn't slow down, we wont be adding more time to the year in total, hence no more days(less days in fact, as you said.)

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No No No.

The earth's rotation around the sun continues at the same rate, which means the length of the year stays the same. 365 days.

But each day, Earth takes 25 hours to rotate around it's own axis.

This so the days are longer but the year remains the same. You now have 25 x 365 = 9125 hours per year, instead of the old 24 x 365 = 8760 hours.

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dodeka

from Laurel, MD

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steelwolf_sg said:
"This so the days are longer but the year remains the same. You now have 25 x 365 = 9125 hours per year, instead of the old 24 x 365 = 8760 hours."

Nope. The number of hours per year is staying the same:

The author said:
". . .we’re revolving around the sun just as quickly as ever, and showing no signs of slowing down."

__________________________________________________________

PKP said:
"Meaning, if the earth-sun rotation doesn't slow down, we wont be adding more time to the year in total, hence no more days(less days in fact, as you said.)"

Yes, that's my point exactly. However, the author's comment that our calendar wouldn't change is misleading. It would change. We'd have a 350-day calendar instead of a 365-day calendar.

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I wonder if Al Gore is going to create a documentary about this obvious threat to earth. He would propose that we realign all roads to the East-West direction and make them all one way. That way by with entire World driving in the same direction we could speed up the rotation of the earth and save us all.

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timias...thats the best joke i have ever heard about Al Gore. I just got done laughing my butt off, and I am still tickled.But the down side to your comment is that now you've given Al gore the idea. He will not ask you for your name for the patent or whatever.

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dodeka is right. OMG! We are going to lose weeks.

If we take the basic unit of time as an hour, then currently it takes 365 x 24 = 8760 hours to finish one orbit around the sun.

Since the orbit isn't slowing, it would still take 8760 hours to go around the sun even when the Earth has 25 hour days.

Thanks dodeka.

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