What Is The Opposite Of A Shadow

On their journeying through space, the Earth and the Moon bandage 3 different shadows causing unlike types of solar and lunar eclipses. Why are there three shadows?

Illustration of the Moon's 3 shadows: umbra, penumbra, and antumbra. — The Moon'southward umbra, penumbra, and antumbra.

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Eclipse Type Depends on Shadow Type

If the Moon's shadow falls on Earth, we get to see a solar eclipse; the Globe's shadow falling on the Moon results in a lunar eclipse. Withal, there are different types of solar and lunar eclipses. A solar eclipse may be full, partial, or annular; a lunar eclipse may be total, partial, or penumbral.

The blazon of eclipse we feel depends on the type of shadow that is involved. Both the Moon and Earth cast 3 shadows:

an umbra,
a penumbra,
and an antumbra.

The umbra is the shadow's dark heart portion, while the penumbra and the antumbra are unlike types of one-half-shadows.

Shadow Experiments

To sympathize why the Globe and the Moon have 3 types of shadows, allow's offset on a smaller scale. The number and types of shadows created by an opaque object depend on its size in relation to the size of the calorie-free source. However, their absolute size is irrelevant, so a basketball illuminated past a large lamp produces the same shadows as the Moon illuminated past the Sunday.

And then imagine that you are in a windowless room with i light source and i round object that casts a shadow, say, a basketball. Both the light source and the basketball are at the same top as your caput. You are standing on the side of the ball exactly opposite to the calorie-free source, facing it, so the club is: light source – basketball game – you.

Illustration image — A punctual light source creates merely an umbra.

1st Experiment: Umbra Only

Rule: If the light emanates from a punctual light source, the object casts only ane type of shadow: an umbra.

Permit'due south say the low-cal source is a tiny flashlight pointing into your direction. If yous look into the direction of the lamp from behind the basketball, information technology is entirely invisible every bit the brawl blocks the view and the low-cal rays don't achieve you. The brawl's shadow is uniform, information technology but has an umbra.

If you move to the side, the flashlight immediately becomes visible as soon as you get out the shadow.

2nd Experiment: Umbra and Penumbra

Rule: If the calorie-free source is non punctual but has a larger area, a 2nd type of shadow appears around the object'southward umbra: the penumbra.

Now the low-cal source is a circular lamp that is a little smaller in diameter than the basketball. If you lot line upward with the lamp and the ball, no light is visible considering you are within the ball's umbra. Nevertheless, as you move to either side, part of the low-cal source becomes visible. That's the penumbra.

If you motion further to the side until you can see all of the lamp'due south surface, you accept left the penumbra.

3rd Experiment: Umbra, Penumbra, and Antumbra

Rule: If the bore of the low-cal source is larger than the diameter of the object, a 3rd type of shadow appears where the cone-shaped umbra ends: the antumbra.

In this experiment, the low-cal source is another round lamp, but this time it has twice the ball's bore. Imagine over again that y'all are looking at the lamp from behind the ball. As long as you are fairly close to information technology, the brawl'southward credible size exceeds the lamp's credible size. You are within the umbra, and the lamp is invisible.

However, as you move away from the ball, its apparent size decreases. At some betoken, the basketball will appear smaller than the lamp. A band of light will appear around the brawl as the outer rim of the lamp comes into view. You take merely entered the basketball's antumbra.

3 Shadows, half-dozen Types of Eclipses

Our solar system resembles the set-up of the final experiment. The Sun is a very large light source, its diameter exceeding that of both the Globe and the Moon. This means that, on their journeying through space, both objects produce all 3 types of shadows.

Depending on which shadow type is involved, nosotros can experience three dissimilar types of solar eclipses and three different types of lunar eclipses on World:

Umbra Eclipses

The umbral shadow can produce the post-obit eclipses:

Total solar eclipse – the Moon's umbra falls on the Earth's surface, and the observer is inside the umbra.
Total lunar eclipse – the Globe's umbra completely covers the Moon.
Partial lunar eclipse – the Earth's umbra covers but part of the Moon.

Penumbra Eclipses

The penumbral shadow is involved in these eclipses:

Partial solar eclipse – the Moon's penumbra falls on the Earth'south surface, and the observer is within the penumbra.
Fractional lunar eclipse – the Earth'southward penumbra covers the expanse of the Moon'south visible surface that is not covered by the umbra.
Penumbral lunar eclipse – the penumbra covers all or part of the Moon, the umbra misses it.

Antumbra Eclipses

The antumbral shadow tin just cause 1 type of eclipse:

Annular solar eclipse – the Moon'southward antumbra falls on the Earth's surface, and the observer is within the antumbra.

Topics: Eclipses, Sun, Astronomy, Moon, Globe