Sunday, 3 November 2013


A MOST intriguing celestial event will occur on the 3rd, which happens to be this Sunday. So I guess you can say I’m “ministering” today.

Anyway, rest assured there’s going to be “miracles” and “wonders” in the sky! The Sun and the new Moon always put on a good show: And Sunday’s hybrid annular-total solar obscuration should definitely keep the covenant—provided you can see it.

This proviso arises from the time of year the obscuration is occurring and the geography of the area. Much of the eclipse tract runs roughly along the seasonally enshrouded Intertropical Convergence Zone, which is hardly a celestial showroom.

Even under ideal viewing conditions though, it is only a partial obscuration we will see. Still, a half of an eclipse is better than none. What is more, Sunday’s event is Africa’s show. It is nature’s reward for visual deprivations, which Nigerians in particular, have suffered in the past.

The point of maximum visibility is off the coast of Liberia. But the tract also rushes through Sao Tome, Cape Verde Islands, Gabon, both the Congos, Uganda, Kenya, Ethiopia and Somalia. These are front row seats, where observers enjoy varying degrees of visual advantage—again, depending on the weather.

A part of the eclipse tract runs somewhat parallel to the equator (an imaginary line that divides Earth into equal halves), about 500 kilometres from Nigeria’s coast. This puts us in the bleachers, you might say, along with most of Black Africa.

Let me explain the disparity. Eclipses are the visual effects of shadows in motion. On Sunday, the Moon will pass between Earth and the Sun, blocking out solar radiation momentarily (totality is a minute and 39 seconds) and extending a cone-shaped shadow towards its parent body.

The Moon, like Earth, casts a shadow-within-a-shadow—a dark cone-shaped umbra, from which most solar radiation is excluded, and a lighter penumbra, peppered with stray photons. When I say “tract,” I mean the trail of the umbra: What astronomers call the “path of totality”.

Keep in mind that Earth is spinning on its axis, while the Moon whirls round-and-round the planet, completing a revolution every 27 days or so—a sidereal month. (The “months” you know, are the synodic or lunar month of 29.5 days, which the New Moon marks off, and the calendar months.)

The Moon’s shadow then, is in motion. The path of totality is a dark swathe pained across Earth’s surface by the tip of the cone-shaped lunar umbra. Its width averages just 160 km and is rarely more than 250. An observer has to be located within this dark band, in order to experience a total eclipse.

What this means, is that even in those countries that have ringside seats, most observers will not experience totality. They’ll see more than us—but something short of a total solar eclipse.

Now, here’s where things get tricky, especially when it comes to Sunday’s annular-total obscuration. Here too, is where “miracles” and “wonders” come into play. The miracle is that, although the Sun is 400 times bigger than the Moon, it also happens to be 400 times farther away from us (giving the Sun about the same angular size, as the lunar disc).

An object’s angular size is how big it appears in relation to a much closer object—such as a distant building, when measured against your thumb. The Moon’s orbit being an ellipse, its distance varies, causing its angular size to change.

“When the Moon is sufficiently close to Earth”, notes Collins Dictionary of Astronomy, “so that its apparent diameter exceeds that of the Sun, then the umbra of the Moon’s shadow can just reach the Earth’s surface.”

When the Sun is eclipsed Sunday though, the Moon will be emerging from apogee—the farthest point from Earth, with a diminished but growing angular diameter. So, in the early stages, it won’t cover the Sun completely.

Instead of touching the Earth, the shadow will dangle just above it! The result is a tentative annular eclipse, in which the darkened solar sphere has a brilliant ring (annulus) around it. Astronomers don’t consider such eclipses total.

But a great wonder is in the works. Sunday’s apparition will appear in the Atlantic, south of Bermuda, as an annular obscuration: Then pass over Gabon and cross Africa as a total eclipse!

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