Tonight is the night the Fall arrives! At 9:29pm, summer will officially be over as the equinox happens right on time. I have shared info below from the Wikipedia page on Equinox to answer all your questions. The past week has been incredible with hundreds of hummingbirds. I have been covered up with birds, bees, sugar water, guest birders and photographers witnessing this annual event at Kates Cabin Bird Sanctuary in Texas. I likely have the smallest hummingbird resort, but I have among the most guest hummers enjoying the water park and feeding stations. (Yes, Mom, you were right: If I build it, they will come!) Sadly, now right on time, they have gone.
From Wikipedia, the free encyclopedia
An equinox occurs twice a year, around 20 March and 22 September. The word itself has several related definitions. The oldest meaning is the day when daytime and night are of approximately equal duration. The word equinox comes from this definition, derived from the Latin aequus(equal) and nox (night). The equinox is not exactly the same as the day when period of daytime and night are of equal length for two reasons. Firstly, sunrise, which begins daytime, occurs when the top of the Sun's disk rises above the eastern horizon. At that instant, the disk's center is still below the horizon. Secondly, Earth's atmosphere refracts sunlight. As a result, an observer sees daylight before the first glimpse of the Sun's disk above the horizon. To avoid this ambiguity, the word equilux is sometimes used to mean a day on which the periods of daylight and night are equal.[note 1] Times of sunset and sunrise vary with an observer's location (longitude and latitude), so the dates when day and night are of exactly equal length likewise depend on location.
The other definitions are based on several related simultaneous astronomical events, and refer either to the events themselves or to the days on which they occur. These events are the reason that the period of daytime and night are approximately equal on the day of an equinox.
An equinox occurs when the plane of Earth's Equator passes the center of the Sun. At that instant, the tilt of Earth's axis neither inclines away from nor towards the Sun. The two annual equinoxes are the only times when the subsolar point—the place on Earth's surface where the center of the Sun is exactly overhead—is on the Equator, and, conversely, the Sun is at zenith over the Equator. The subsolar point crosses the equator, moving northward at the March equinox and southward at the September equinox.
At an equinox, the Sun is at one of the two opposite points on the celestial sphere where the celestial equator (i.e.declination 0) and ecliptic intersect. These points of intersection are called equinoctial points: classically, the vernal point(RA = 00h 00m 00s and longitude = 0°) and the autumnal point (RA = 12h 00m 00s and longitude = 180°).
The equinoxes are the only times when the solar terminator is perpendicular to the Equator. As a result, the Northern and Southern Hemispheres are illuminated equally.
|UT date and time of|
equinoxes and solstices on Earth
Length of equinoctial day and night
On the day of the equinox, the center of the Sun spends a roughly equal amount of time above and below the horizon at every location on the Earth, so night and day are about the same length. The word equinox derives from the Latin words aequus (equal) and nox (night). In reality, the day is longer than the night at an equinox. Day is usually defined as the period when sunlight reaches the ground in the absence of local obstacles. From the Earth, the Sun appears as a disc rather than a point of light, so when the center of the Sun is below the horizon, its upper edge is visible. Furthermore, the atmosphere refracts light, so even when the upper limb of the Sun is 0.4 degrees below the horizon, its rays curve over the horizon to the ground. In sunrise/sunset tables, the assumed semidiameter (apparent radius) of the Sun is 16 minutes of arc and the atmospheric refraction is assumed to be 34 minutes of arc. Their combination means that when the upper limb of Sun is on the visible horizon, its center is 50 minutes of arc below the geometric horizon, which is the intersection with the celestial sphere of a horizontal plane through the eye of the observer. These effects make the day about 14 minutes longer than the night at the Equator and longer still towards the Poles. The real equality of day and night only happens in places far enough from the Equator to have a seasonal difference in day length of at least 7 minutes, actually occurring a few days towards the winter side of each equinox.
Because the Sun is a spherical (rather than a single-point) source of light, the actual crossing of the Sun over the Equator takes approximately 33 hours.
At the equinoxes, the rate of change for the length of daylight and night-time is the greatest. At the poles, the equinox marks the start of the transition from 24 hours of nighttime to 24 hours of daylight (or vice versa). Far north of the Arctic Circle, at Longyearbyen, Svalbard, Norway, there is an additional 15 minutes more daylight every day about the time of the Spring equinox, whereas in Singapore (which is just one degree of latitude north of the Equator), the amount of daylight in each daytime varies by just a few seconds.
Link to Photo Album Gallery:
The Last Sunset of Summer
The Hummingbird Migration 2014
Good news: I had a feeling yesterday they were getting ready to go on to Mexico. I shot 10001 pics yesterday, the best day! I have averaged 500 pics a day since Sept 1, 2014. I tried to capture all parts of the migration and all positions of birds. At one point, there were over 400 tiny birds here! I will be editing and posting these pics for quite a while! Stay tuned!
...this is brendasue signing off from Rainbow Creek. See you next time! Happy Fall for All!!!!!!!!!!!!!!!!