![Page 1: Eclipses Understanding Shadows · Eclipses Understanding Shadows An eclipse occurs when one astronomical object casts a shadow on the other. Solar Eclipses – The Sun casts a shadow](https://reader033.vdocuments.net/reader033/viewer/2022052612/5f11fb445d33d514892e1dfd/html5/thumbnails/1.jpg)
1
Eclipses Understanding Shadows An eclipse occurs when one astronomical object casts a shadow
on the other.● Solar Eclipses – The Sun casts a shadow on the Earth
● Lunar Eclipses – The Earth casts a shadow on the Moon
![Page 2: Eclipses Understanding Shadows · Eclipses Understanding Shadows An eclipse occurs when one astronomical object casts a shadow on the other. Solar Eclipses – The Sun casts a shadow](https://reader033.vdocuments.net/reader033/viewer/2022052612/5f11fb445d33d514892e1dfd/html5/thumbnails/2.jpg)
2
The Geometry of Shadows
A shadow created from an extended source of light (e.g. The Sun) has two parts.
● A dark umbra (“A”) in which all light from the Sun is blocked
● A less shaded penumbra (“B”, “C”, “D”) where part of the light from the Sun is blocked.
![Page 3: Eclipses Understanding Shadows · Eclipses Understanding Shadows An eclipse occurs when one astronomical object casts a shadow on the other. Solar Eclipses – The Sun casts a shadow](https://reader033.vdocuments.net/reader033/viewer/2022052612/5f11fb445d33d514892e1dfd/html5/thumbnails/3.jpg)
3
Moon Phase and Eclipses
Because of the required alignment between Sun, Moon, and Earth eclipses either happen at Full or New Moon
● For a total solar eclipse the Moon is New.
● For a total lunar eclipse the Moon is Full.
Not to Scale!!!!
![Page 4: Eclipses Understanding Shadows · Eclipses Understanding Shadows An eclipse occurs when one astronomical object casts a shadow on the other. Solar Eclipses – The Sun casts a shadow](https://reader033.vdocuments.net/reader033/viewer/2022052612/5f11fb445d33d514892e1dfd/html5/thumbnails/4.jpg)
4
Why Eclipses are Rare
The Earth and Moon, when seen to true scale, are tiny compared to their separation. Alignment must be nearly perfect.
● The tilt of the Moon's orbit hinders that alignment.
If this figure were true to scale the Moon would be twice as far from the Earth!!
![Page 5: Eclipses Understanding Shadows · Eclipses Understanding Shadows An eclipse occurs when one astronomical object casts a shadow on the other. Solar Eclipses – The Sun casts a shadow](https://reader033.vdocuments.net/reader033/viewer/2022052612/5f11fb445d33d514892e1dfd/html5/thumbnails/5.jpg)
5
Why Eclipses are Rare
The Earth and Moon, when seen to true scale, are tiny compared to their separation. Alignment must be nearly perfect.
● The tilt of the Moon's orbit hinders that alignment.
![Page 6: Eclipses Understanding Shadows · Eclipses Understanding Shadows An eclipse occurs when one astronomical object casts a shadow on the other. Solar Eclipses – The Sun casts a shadow](https://reader033.vdocuments.net/reader033/viewer/2022052612/5f11fb445d33d514892e1dfd/html5/thumbnails/6.jpg)
6
Why Eclipses are Rare
The Earth and Moon, when seen to true scale, are tiny compared to their separation. Alignment must be nearly perfect.
● There are two times a year, separated by 6 months, when the shadows line up.
![Page 7: Eclipses Understanding Shadows · Eclipses Understanding Shadows An eclipse occurs when one astronomical object casts a shadow on the other. Solar Eclipses – The Sun casts a shadow](https://reader033.vdocuments.net/reader033/viewer/2022052612/5f11fb445d33d514892e1dfd/html5/thumbnails/7.jpg)
7
Solar Eclipses
Solar eclipses occur when the Moon blocks the Sun from view.● The Moon must be New.
● The total eclipse can be seen from a limited set of locations.
![Page 8: Eclipses Understanding Shadows · Eclipses Understanding Shadows An eclipse occurs when one astronomical object casts a shadow on the other. Solar Eclipses – The Sun casts a shadow](https://reader033.vdocuments.net/reader033/viewer/2022052612/5f11fb445d33d514892e1dfd/html5/thumbnails/8.jpg)
8
Solar Eclipses
The tapering umbral shadow of the Moon just barely reaches Earth (sometimes it doesn't – an annular eclipse)
● The Moon's umbral shadow is small – covering a couple of hundred miles at best.
![Page 9: Eclipses Understanding Shadows · Eclipses Understanding Shadows An eclipse occurs when one astronomical object casts a shadow on the other. Solar Eclipses – The Sun casts a shadow](https://reader033.vdocuments.net/reader033/viewer/2022052612/5f11fb445d33d514892e1dfd/html5/thumbnails/9.jpg)
9
Solar Eclipses
The Moon's orbital motion and Earth rotation sweep the shadow across the Earth in a matter of hours.
● Locations along this eclipse path experience “totality” for a few minutes at best.
![Page 10: Eclipses Understanding Shadows · Eclipses Understanding Shadows An eclipse occurs when one astronomical object casts a shadow on the other. Solar Eclipses – The Sun casts a shadow](https://reader033.vdocuments.net/reader033/viewer/2022052612/5f11fb445d33d514892e1dfd/html5/thumbnails/10.jpg)
10
Solar Eclipses
The Moon's orbital motion and Earth rotation sweep the shadow across the Earth in a matter of hours.
● Locations along this eclipse path experience “totality” for a few minutes at best.
![Page 11: Eclipses Understanding Shadows · Eclipses Understanding Shadows An eclipse occurs when one astronomical object casts a shadow on the other. Solar Eclipses – The Sun casts a shadow](https://reader033.vdocuments.net/reader033/viewer/2022052612/5f11fb445d33d514892e1dfd/html5/thumbnails/11.jpg)
11
Solar Eclipses
Despite the short duration and remote location, people go to extremes to view eclipses.
● Phenomena that are usually washed out by the blue sky become visible – the solar corona and solar prominences.
http://www.mreclipse.com/
![Page 12: Eclipses Understanding Shadows · Eclipses Understanding Shadows An eclipse occurs when one astronomical object casts a shadow on the other. Solar Eclipses – The Sun casts a shadow](https://reader033.vdocuments.net/reader033/viewer/2022052612/5f11fb445d33d514892e1dfd/html5/thumbnails/12.jpg)
12
![Page 13: Eclipses Understanding Shadows · Eclipses Understanding Shadows An eclipse occurs when one astronomical object casts a shadow on the other. Solar Eclipses – The Sun casts a shadow](https://reader033.vdocuments.net/reader033/viewer/2022052612/5f11fb445d33d514892e1dfd/html5/thumbnails/13.jpg)
13
![Page 14: Eclipses Understanding Shadows · Eclipses Understanding Shadows An eclipse occurs when one astronomical object casts a shadow on the other. Solar Eclipses – The Sun casts a shadow](https://reader033.vdocuments.net/reader033/viewer/2022052612/5f11fb445d33d514892e1dfd/html5/thumbnails/14.jpg)
14
![Page 15: Eclipses Understanding Shadows · Eclipses Understanding Shadows An eclipse occurs when one astronomical object casts a shadow on the other. Solar Eclipses – The Sun casts a shadow](https://reader033.vdocuments.net/reader033/viewer/2022052612/5f11fb445d33d514892e1dfd/html5/thumbnails/15.jpg)
15
![Page 16: Eclipses Understanding Shadows · Eclipses Understanding Shadows An eclipse occurs when one astronomical object casts a shadow on the other. Solar Eclipses – The Sun casts a shadow](https://reader033.vdocuments.net/reader033/viewer/2022052612/5f11fb445d33d514892e1dfd/html5/thumbnails/16.jpg)
16
![Page 17: Eclipses Understanding Shadows · Eclipses Understanding Shadows An eclipse occurs when one astronomical object casts a shadow on the other. Solar Eclipses – The Sun casts a shadow](https://reader033.vdocuments.net/reader033/viewer/2022052612/5f11fb445d33d514892e1dfd/html5/thumbnails/17.jpg)
17
![Page 18: Eclipses Understanding Shadows · Eclipses Understanding Shadows An eclipse occurs when one astronomical object casts a shadow on the other. Solar Eclipses – The Sun casts a shadow](https://reader033.vdocuments.net/reader033/viewer/2022052612/5f11fb445d33d514892e1dfd/html5/thumbnails/18.jpg)
18
![Page 19: Eclipses Understanding Shadows · Eclipses Understanding Shadows An eclipse occurs when one astronomical object casts a shadow on the other. Solar Eclipses – The Sun casts a shadow](https://reader033.vdocuments.net/reader033/viewer/2022052612/5f11fb445d33d514892e1dfd/html5/thumbnails/19.jpg)
19
Note the nearly identical eclipses 18+ years apart. The Moon's exact position repeats relative to the Earth and Sun every 18 years creating a family of eclipses – the Saros cycle.
![Page 20: Eclipses Understanding Shadows · Eclipses Understanding Shadows An eclipse occurs when one astronomical object casts a shadow on the other. Solar Eclipses – The Sun casts a shadow](https://reader033.vdocuments.net/reader033/viewer/2022052612/5f11fb445d33d514892e1dfd/html5/thumbnails/20.jpg)
20
Solar Eclipses from Charlottesville?
You have to wait several hundred years on average for a total solar eclipse to happen at your location.
● Partial eclipses, which cover more area, are common however.
![Page 21: Eclipses Understanding Shadows · Eclipses Understanding Shadows An eclipse occurs when one astronomical object casts a shadow on the other. Solar Eclipses – The Sun casts a shadow](https://reader033.vdocuments.net/reader033/viewer/2022052612/5f11fb445d33d514892e1dfd/html5/thumbnails/21.jpg)
21
Eclipses in the Next Century
![Page 22: Eclipses Understanding Shadows · Eclipses Understanding Shadows An eclipse occurs when one astronomical object casts a shadow on the other. Solar Eclipses – The Sun casts a shadow](https://reader033.vdocuments.net/reader033/viewer/2022052612/5f11fb445d33d514892e1dfd/html5/thumbnails/22.jpg)
22
Eclipses on Other Worlds
The outer planets have lots of moons...
![Page 23: Eclipses Understanding Shadows · Eclipses Understanding Shadows An eclipse occurs when one astronomical object casts a shadow on the other. Solar Eclipses – The Sun casts a shadow](https://reader033.vdocuments.net/reader033/viewer/2022052612/5f11fb445d33d514892e1dfd/html5/thumbnails/23.jpg)
23
Lunar EclipsesThe Earth casts a shadow on the Moon
● To be specific the Moon moves through the Earth's shadow
![Page 24: Eclipses Understanding Shadows · Eclipses Understanding Shadows An eclipse occurs when one astronomical object casts a shadow on the other. Solar Eclipses – The Sun casts a shadow](https://reader033.vdocuments.net/reader033/viewer/2022052612/5f11fb445d33d514892e1dfd/html5/thumbnails/24.jpg)
24
Lunar EclipsesThe Moon takes a couple of hours to cross the Earth's shadow.
● The Earth's umbral shadow is large enough to consume the whole Moon.
![Page 25: Eclipses Understanding Shadows · Eclipses Understanding Shadows An eclipse occurs when one astronomical object casts a shadow on the other. Solar Eclipses – The Sun casts a shadow](https://reader033.vdocuments.net/reader033/viewer/2022052612/5f11fb445d33d514892e1dfd/html5/thumbnails/25.jpg)
25
Lunar EclipsesEverybody on the night side of the Earth can see the eclipse.
![Page 26: Eclipses Understanding Shadows · Eclipses Understanding Shadows An eclipse occurs when one astronomical object casts a shadow on the other. Solar Eclipses – The Sun casts a shadow](https://reader033.vdocuments.net/reader033/viewer/2022052612/5f11fb445d33d514892e1dfd/html5/thumbnails/26.jpg)
26
Lunar EclipsesThe Moon takes on a reddish hue during the total eclipse because of light refracted through the Earth's atmosphere.
● This is the combined light of all of the world's sunrises and sunsets!
The View from the Moon
![Page 27: Eclipses Understanding Shadows · Eclipses Understanding Shadows An eclipse occurs when one astronomical object casts a shadow on the other. Solar Eclipses – The Sun casts a shadow](https://reader033.vdocuments.net/reader033/viewer/2022052612/5f11fb445d33d514892e1dfd/html5/thumbnails/27.jpg)
27
![Page 28: Eclipses Understanding Shadows · Eclipses Understanding Shadows An eclipse occurs when one astronomical object casts a shadow on the other. Solar Eclipses – The Sun casts a shadow](https://reader033.vdocuments.net/reader033/viewer/2022052612/5f11fb445d33d514892e1dfd/html5/thumbnails/28.jpg)
28
Annular vs. Total Eclipses
The Moon follows an elliptical orbit.● When it is close to the Earth it easily covers the Sun (total eclipse) when far
away its angular size is smaller than the Sun's (annular eclipse).
![Page 29: Eclipses Understanding Shadows · Eclipses Understanding Shadows An eclipse occurs when one astronomical object casts a shadow on the other. Solar Eclipses – The Sun casts a shadow](https://reader033.vdocuments.net/reader033/viewer/2022052612/5f11fb445d33d514892e1dfd/html5/thumbnails/29.jpg)
29
Annular vs. Total Eclipses
The Moon follows an elliptical orbit.● When it is close to the Earth it easily covers the Sun (total eclipse) when far
away its angular size is smaller than the Sun's (annular eclipse).
![Page 30: Eclipses Understanding Shadows · Eclipses Understanding Shadows An eclipse occurs when one astronomical object casts a shadow on the other. Solar Eclipses – The Sun casts a shadow](https://reader033.vdocuments.net/reader033/viewer/2022052612/5f11fb445d33d514892e1dfd/html5/thumbnails/30.jpg)
30
Annular vs. Total EclipsesSo much Sun is visible during an annular eclipse that none of the spectacular solar eclipse phenomena is visible.