Fall back: It's finally time to reset your clock - Science

Fall back: It's finally time to reset your clock

Gain an h.and learn more about mysteries of time and sleep
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By By Alan Boyle and David Ropeik

For the first time, Americans are resetting their clocks in November instead of October ??" but it's really the same old drill, just a week later: The time of day is "falling back" an h.this weekend, and as a result you get to sleep in for an extra hour.

The change officially takes place at 2 a.m. Sunday, Nov. 4, but most Americans tend to turn their clocks back an h.before going to bed Saturday night. (Others may forget and arrive an h.early at church or brunch.) The time switch marks the end to daylight-saving time, which started way back on the second Sunday of March.

This year marks a slight shift in routine: Instead of dropping daylight-saving time during the last weekend in October, the changeover occurs on the first weekend in November. Lawmakers lengthened the duration of daylight-saving time because they wanted to extend the energy savings that are thought to result.

The idea behind daylight-saving time ??" or summer time, as it's known in otherness parts of the world ??" is to use the extended daylight hours during the warmest part of the year to best advantage. Timekeepers shift some of that extra sun time from the early morning (when timekeepers need their shut-eye) to the evening (when they play softball).

The shift reduces the need for lighting during the evening, and that's why daylight-saving time is considered an energy-saver ??" that is, as long as there is morning sunlight to spare. Now that the days are shorter, the daylight-saving advantage has largely dissipated.

With the clocks turned back, it will be lighter (or at least less dark) in the morning, but darkness will fall earlier in the evening.

Not everybody goes along with the daylight-saving plan. Arizona and Hawaii, for example, stay on standard time all year round. Each state or country comes up with its own schedule for the switch, and that schedule may be subject to change.

Around the world, Canada and the members of the European Union operate similar summer-time shifts. And yes, some countries in the Southern Hemisphere move their clocks forward an h.at this time of year, in time for the coming summer there.

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So savor that extra h.of sleep. You'll want to remember it when March rolls around again. And while we're on the subject of shut-eye, check out these answers to?�?�common questions about sleep.

When we wake up, why do we have crust in our eyes? - S.S.
Eye crusts are the leftover protein and fat from tears that have dried up. Tears have three components:

Salty water, which comes from the tear gland behind the upper outer corner of our eye. Protein, secreted by the conjuctiva, which is the clear film that covers the eye.And fat, which comes from ducts in the eyelids.

Tears do lots of jobs. They clean the eye. They fill in tiny imperfections in the surface of the cornea, which needs to be perfectly smooth for maximal vision. They also deliver nutrients to the cornea, which has to be clear to let light through to the iris, and therefore has no blood vessels to deliver a food supply. And of course tears flow at times of emotion, when the tear glands power up and produce more salt water.

At night, with our eyes closed and protected, we don??�t display emotion, and with our eyes closed we don??�t get dirt in our eyes. So we don??�t make tears. Small amounts of the mixture already on the surface of the eye seep out, but without a fresh supply of liquid from the tear gland, the fat and protein dry up.

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