Newest solar midday is available in February
For you, when you’re time-conscious … February 11 marks the newest solar midday for all of 2023, and for your complete 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 instantaneous 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 one in every 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 exhibits what’s known as the equation of time. That’s a elaborate title for the discrepancy between solar midday and clock midday. Because the graph exhibits, the newest solar midday in February happens a strong 1/2 hour later by the clock than the yr’s earliest solar midday in early November.
Yearly, the newest solar midday occurs on (or close to) February 11 and the earliest solar midday occurs on (or close to) November 3. That’s true irrespective 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 arrival of time zones and standard time, the equation of time graph (under) utilized to anyplace worldwide. In our day and age, the graph refers to locations that reside on the middle 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. Maintain 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 idea) 15 levels of longitude extensive. 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 idea) about 1,035 miles (1,665 km) extensive. By the way in which, we maintain saying “in idea” as a result of time zone borders sometimes aren’t straight strains. 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 japanese 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 yr, and at any location – solar midday occurs 1/2 hour later by the clock on February 11 than on November 3.
By the way in which, we emphasize we’re speaking about standard time. We aren’t speaking about daylight saving time or summer time, by which we fake that it’s one hour later than it’s.
However there’s no must 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 means, you’ll know your clock time for solar midday for any day of the yr.
Unequal size of solar days
The day – as measured from one solar midday to the following – hardly ever equals 24 hours. The truth is, a 24-hour solar day occurs however 4 instances a yr, on or close to these dates: February 11, Might 14, July 26 and November 3. Once more, we invite you to review 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 instances a yr: on or close to April 15, June 15, September 1 and December 25. Have a look at the graph above and you’ll 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. At the beginning, 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 yr 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 yr’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 actual solar day (as measured by the sundial) varies in size all year long. The discrepancy between the clock and the sundial is rarely larger than 1/2 minute on any given day. Even so, the discrepancy accumulates each day for roughly three months. That’s why the newest 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 yr? Go to this online calculator and scroll all the way down to the equation of time column (first column). Moreover, you could find out the solar day period underneath the fifth column.
Backside line: February 11 ushers within the newest noontime sun of the yr, by nature’s clock. And for people dwelling on the Earth’s equator, this date additionally marks the day of the yr’s newest dawn and newest sundown.
