The word “eclipse” is a general astronomical term that applies to any situation in which the view of one object is blocked by another, caused either by the second object’s shadow falling over the first, or by the second object coming in between the first object and the observer.
In general use the term eclipse usually applies to one of two situations: a solar eclipse, in which the Moon obscures our view of the Sun; or a lunar eclipse in which the Earth’s shadow falls over the Moon. The planes in which the Earth orbits the Sun and which the Moon orbits the Earth are at an angle to each other, which is why there is not a total solar eclipse once every month.
There are three types of solar eclipse:
- A total eclipse, in which the Moon appears the same size as the Sun and blocks light from it completely.
- An annular eclipse, in which the Moon passes between the Sun and the Earth but because of the relative distances of each it appears slightly smaller than the Sun, causing a ring of light to appear.
- A partial eclipse, in which the orbits of the Moon and Sun are such that the Moon only covers only part of the Sun.
A comparison of a total solar eclipse (left) and an annular eclipse (right). Only in the case of a total solar eclipse is the Sun’s corona (the white “cloud”) visible.
A diagram showing how the three different types of eclipse are formed.
There are also hybrid eclipses, which appear as total eclipses to some parts of the Earth and an annular eclipse to other parts. These are very rare, with the most recent in April 2005 and visible mainly from the Pacific Ocean and also Costa Rica, Panama, Colombia and Venezuela; and the next to occur in November 2013, visible from Central Africa (Gabon, Congo, Democratic Republic of the Congo, Uganda, Kenya, Ethiopia and Somalia).
I was surprised to find that the amount of time spent on the Moon by Neil Armstrong and “Buzz” Aldrin on the Apollo 11 mission was really quite small when compared with the time spent by astronauts on subsequent Apollo missions.
Only 12 people (all men, unfortunately) have ever set foot on the Moon. The person to spend the most time on the Moon is Gene Cernan, the commander of the Apollo 17 mission. He left the Apollo lander before the Apollo 17 Lunar Module pilot, NASA geologist Harrison Schmitt, and re-entered the lander after Schmitt. He is therefore also the last person to set foot on the Moon, all the way back in 1972.
Gene Cernan cruising the lunar surface in the lunar rover
Cernan also co-holds (with Thomas Stafford and John Young) the record for the fastest speed achieved by a human being, as the Apollo 10 probe on which he was a passenger reached a speed of 11.1 kilometres per second (24 790 mph) on its return to Earth after orbiting the Moon. The Apollo 10 Command Module is now on display at the Science Museum in London.
A footprint wasn’t the only thing that Neil Armstrong left on the Moon.
Amongst the list of things we have left on the Moon are four “defecation collection devices”, four “urine collection assemblies” (two small, two large) and four emesis (sick) bags.
If you’re interested – really, you are? – then check out Chapter 2 of Section VI of NASA’s Biomedical Results of Apollo report which – and I can barely believe I’m writing this – goes as far as to list the average mass of returned fecal samples.
The All-Terrain Hex-Legged Extra-Terrestrial Explorer (ATHLETE) rover is a next-generation robotic lunar exploration vehicle.
ATHLETE is designed to load and transport heavy loads across the rough lunar surface. Each rover can carry half a ton and multiple rovers can work together to transport heavier loads.
ATHLETE can roll and walk across the lunar surface and can even use a grappling hook to rappel down steep slopes.
There are some amazing videos of ATHLETE in action at its JPL homepage.