Where highest woods, impenetrable
To star or sunlight, spread their umbrage broad. --Milton.
Hey, who turned out the lights? -- Milton Berle.
- Before discussing eclipses, it is important to understand
the nature of shadows.
- Solar Eclipses
- The Moon casts a shadow on the Earth.
- A total eclipse is only visible from a small fraction of the Earth's surface because the Moon's umbral shadow
covers a small area.
- You have to be at just the right location on the Earth to see a total
- The Moon's orbital motion combined with the Earth's rotation
sweeps the shadow across the Earth in a matter of hours.
- A total eclipse is visible for only a few minutes from any particular location.
- When the Moon completely obscures the Sun faint features, like Solar prominences and the Solar
corona (normally washed out by the Earth's bright atmosphere) come into view. The planets and the brighter stars also become visible.
- Here is a movie showing
a simulated solar eclipse produced by Pluto's satellite Charon. You will see
Charon casting its shadow on Pluto. If you are standing at a point
the shadow passes over you will see the Sun completely blocked. The
Sun is behind you in this simulation.
- Here is an example of a total solar eclipse
occurring on Jupiter. In fact this image shows three
simultaneous solar eclipses occurring on Jupiter!
- Lunar Eclipses
- The moon passes through the Earth's shadow.
- Lunar eclipses occur at FULL moon.
- The Earth's umbral shadow is large enough to cover the
- Lunar eclipses are visible from the entire night side of the Earth. Many people see them.
- It takes the Moon more than an hour to move through the Earth's shadow.
- The Earth's umbral shadow is not completely dark.
- Some light refracts through the Earth's atmosphere
into the shadow region giving the Moon a reddish hue.
- The combined light of all of the Earth's sunrises
and sunsets illuminates the eclipsed Moon!
- Every lunar eclipse is unique. Sometimes the Moon almost completely disappears. Sometimes it is bright orange.
- This movie shows
a simulation of Pluto's satellite Charon passing into Pluto's shadow and
thus experiencing a lunar eclipse. If you are on the
night side of Pluto you will see Charon pass into Pluto's shadow.
If you are on the day side of Pluto you will not be able to
watch this event happen. The Sun is behind you in this simulation.
- Eclipses do not occur at every New and Full Moon.
- The Moon's orbital plane about the Earth is tipped slightly relative
to the Earth's orbital plane about the Sun.
- Since the Moon and Earth are quite distant from one another
compared with their diameters (a fact overlooked by most people
of the preponderance of drawings showing them on top of one another)
the alignment must be precise in order for an eclipse to occur.
- Only twice a year are the Moon and Earth near the line which
represents the intersection of their orbital planes.
- This line is called the "line of nodes."
- Right now this alignment occurs in March and September.
- This website as well as this one, maintained by Fred Espenak, provides detailed information about past and future eclipses.
- The last total solar eclipse in Charlottesville occurred in 1506.
The next will occur in 2099.
- A random spot on Earth will experience a total solar eclipse about once in 400 years.
- Only two total solar eclipses will occur on US soil in the first half of this century. None have occurred in the last 25 years.
Updated February 10, 2010