Newest solar midday is available in February
For you, if you happen to’re time-conscious … February 11 marks the most recent solar midday for all of 2023, and for your entire globe, by the clock. Nonetheless, solar midday isn’t a clock occasion, regardless that our clocks and calendars measure its continuous shift all year long. So what’s it? It’s a pure occasion. Photo voltaic midday – aka noon – refers to that passing prompt when the sun reaches its highest level for the day, halfway between dawn and sundown.
At solar midday, the sun is claimed to cross your meridian, as depicted on the diagram under. Irrespective of the place you reside worldwide, the sun can solely be at considered one of three locations in your sky at solar midday: at your zenith (straight overhead), south of zenith, or north of zenith. The noonday sun can solely attain zenith on the tropics. From northern temperate latitudes, the noonday sun is all the time south of zenith. At southern temperate latitudes, the noonday sun is all the time north of zenith.
The equation of time
We invite you to take a look at the graph under. It reveals what’s known as the equation of time. That’s a flowery identify for the discrepancy between solar midday and clock midday. Because the graph reveals, the most recent solar midday in February happens a stable 1/2 hour later by the clock than the 12 months’s earliest solar midday in early November.
Yearly, the most recent solar midday occurs on (or close to) February 11 and the earliest solar midday occurs on (or close to) November 3. That’s true regardless of the place you reside worldwide. North, south, east, west on the globe … doesn’t matter. For all of us, solar midday occurs over half-hour later by the clock on February 11 than it does on November 3.
Earlier than the appearance of time zones and standard time, the equation of time graph (under) utilized to wherever worldwide. In our day and age, the graph refers to locations that reside on the heart line of a given time zone. For instance, Denver, Colorado – at 105 levels west longitude – sits on the middle line of the Mountain Standard Time zone. So, in Denver, solar midday reads 12:14 p.m. by the clock on February 11, and 11:44 a.m. by the clock on November 3.
Elsewhere inside a given time zone, the usual clock time for solar midday differs. Preserve studying to know why.
The place are you in your time zone?
Earth is split into round 24 time zones, and every time zone is (in concept) 15 levels of longitude huge. As a result of Earth is a sphere, time zones are widest throughout on the equator. They cut back in width as you go north or south, till they attain to zero levels on the poles. In different phrases, the time zones meet on the poles. So, on the equator, a time zone is (in concept) about 1,035 miles (1,665 km) huge. By the best way, we hold saying “in concept” as a result of time zone borders sometimes aren’t straight traces. They’re typically drawn in a zigzag style to accommodate the boundaries of countries, states or provinces.
However for all of us – except you reside at Earth’s North or South Pole – your time zone has some width to it. And also you may need observed that dawn and sundown within the sky occur later (by the clock) as you go immediately west in a given time zone.
So it’s for solar midday. Photo voltaic midday comes 4 minutes later by the clock for each 1 diploma you reside west of your time zone’s jap edge. Photo voltaic midday comes 4 minutes earlier by the clock for each 1 diploma you reside east of your time zone’s western edge. Irrespective of. It’s nonetheless the case that – in any 12 months, and at any location – solar midday occurs 1/2 hour later by the clock on February 11 than on November 3.
By the best way, we emphasize we’re speaking about standard time. We’re not speaking about daylight saving time or summer time, wherein we faux that it’s one hour later than it’s.
However there’s no have to undergo psychological gymnastics to determine the clock time for solar midday in your location. Simply visit the Sunrise Sunset calendar site, enter your location, and take a look at the column marked solar midday.
On this approach, you’ll know your clock time for solar midday for any day of the 12 months.
Unequal size of solar days
The day – as measured from one solar midday to the following – not often equals 24 hours. The truth is, a 24-hour solar day occurs however 4 occasions a 12 months, on or close to these dates: February 11, Might 14, July 26 and November 3. Once more, we invite you to check the equation of time graph above. The 24-hour solar days solely happen on the turning factors above (February 11 and July 26) and under (Might 14 and November 3).
The sun and the clock solely agree 4 occasions a 12 months: on or close to April 15, June 15, September 1 and December 25. Take a look at the graph above and you may see that the solar day is shorter than 24 hours on April 15 and September 1, but longer than 24 hours on June 15 and December 25.
Shorter days at equinoxes, longer days at solstices
Earth-sun geometry dictates seasonal variation within the size of solar days. Photo voltaic days are lower than 24 hours lengthy for roughly 3 months centered across the equinoxes (March 20 and September 23). And solar days are longer than 24 hours for roughly 3 months centered across the solstices (June 21 and December 21).
Two causes account for the unequal size of the solar day. Firstly, the lean of the Earth’s axis causes the solar day to be greater than 24 hours lengthy across the solstices, and fewer than 24 hours lengthy across the equinoxes. However Earth’s eccentric orbit performs a task, too, both accentuating or lessening the size of the solar day.
Across the December solstice, the Earth is a few 3 million miles (5 million km) nearer to the sun than on the June solstice. So Earth travels most swiftly in its orbit for the 12 months in December and January. It travels most slowly in June and July.
Therefore, at and across the December solstice, the Earth should rotate farthest on its axis for the sun to return to its noontime place. That offers us the 12 months’s longest solar days across the December solstice: 24 hours + 30 seconds.
In distinction, the solar days accompanying the June solstice are significantly shorter: 24 hours + 13 seconds.
Imply sun versus actual sun
Briefly, the mean sun utilized by the clock is a fiction. The clock presumes Earth’s rotational axis stands upright as we revolve across the sun. The clock additionally presumes Earth goes across the sun in an ideal circle. Neither presumption is right. Earth’s rotational axis is titled practically 23.5 levels out of perpendicular to its orbital aircraft. And, as talked about earlier than, Earth’s distance from the sun varies by about 3 million miles (5 million km).
The mean solar day is 24 hours lengthy. However the true solar day (as measured by the sundial) varies in size all year long. The discrepancy between the clock and the sundial isn’t higher than 1/2 minute on any given day. Even so, the discrepancy accumulates each day for roughly three months. That’s why the most recent solar midday in February comes 1/2 hour later by the clock than the earliest solar noon in early November.
Need to know the time distinction between the clock and sundial for any day of the 12 months? Go to this online calculator and scroll right down to the equation of time column (first column). Moreover, you will discover out the solar day length underneath the fifth column.
Backside line: February 11 ushers within the newest noontime sun of the 12 months, by nature’s clock. And for folk residing on the Earth’s equator, this date additionally marks the day of the 12 months’s newest dawn and newest sundown.
