50 years ago today, as part of the first manned spaceflight program, John Glenn became the first American to orbit planet Earth as part of the Project Mercury space program. But why was the program named Mercury?
Though NASA claims the Mercury program was named for the Roman god of trade, thieves and travel (but more commonly known as the God of Speed) and not named for our solar system’s innermost planet, it’s difficult to deny the coincidence that not only is today the 50th anniversary of that first Earth orbit, but today also begins a three-week period when the planet Mercury is best viewed from Earth.
But it truly is coincidence. In 1962, the planet Mercury was in a similar elongation of its orbit but at the opposite end and a couple of days earlier in the cycle. As an example, today begins the three-week period in which Mercury is best viewed in the evening, low on the horizon of the western sky, whereas in 1962 the period of best viewing began a couple of days earlier and was best viewed on the eastern horizon near sunrise.
Compared to Earth, the orbit of Mercury is highly elliptical and one year (one complete orbit of the Sun) on Mercury takes approximately 90 days. This allows Mercury to come into this late-February optimal viewing only every six or seven years (1953, 1959, 1966, 1973, 1979, 1986, 1992, 1999, 2005, and 2019 are years with similar elongations to 2012).
Naming the Mercury Program for the God of Speed certainly makes sense. However, John Glenn — like he had nothing else to do — could’ve looked east while waiting for his 9:47 EST lift-off and seen Mercury low on the horizon around sunrise. So maybe it wasn’t a coincidence after all.
On Friday last week I wrote about viewing Mercury in the coming weeks. You can visit that posting here. As for the best Mercury-viewing weather, it’s a quiet week ahead but not without pockets of rain or snow. Fortunately, this viewing window is open for three weeks and the weather should cooperate at least some of the time for you.