Orientation

June 14, 2018

 

NASA "Blue Marble" Shot (1972) by Apollo Astronaut Harrison Schmitt
 

The physicist Fred Hoyle predicted in 1948 that once a photograph of the entire earth was taken from outer space “a new idea as powerful as any in history will be let loose.”  His words were prophetic.  NASA’s famous “Blue Marble” shot, taken on the final Apollo manned moon mission in 1972, created a worldwide sensation when it was released.  Nearly 50 years later, it remains the only image taken by astronauts of the entire globe and is believed to be one of the most widely reproduced photographs of all time.  Our brilliantly illuminated planet, pictured looking up at Antarctica and the continent of Africa from below, does indeed appear like a giant blue glass marble set off against the inky blackness of space.  

The photo op had not been part of the original mission plan.  The shot was taken five hours into the flight, with the Apollo 17 spacecraft positioned so the entire planet was lit up as it sped toward the moon.  Astronaut Harrison Schmitt* seized the opportunity to take the earth’s picture with a modified 70-mm Hasselblad  – the only camera not stowed away for use later in the flight.  

The curious thing is that the photo was published upside down.  You would never know it to look at the image, because Antarctica appears at the bottom of the picture where you would expect it.  However, the spacecraft was oriented in such a way that the South Pole was actually at the top of the world and the Arabian peninsula at the bottom when the picture was taken.  The photographer was 28,000 miles from home in zero gravity and would have had no bodily sense of up and down.  There is, of course, no particular reason why north should always be up and south down. Presumably NASA decided to adhere to earthly convention so as not to confuse people.

Humans have been mapping our world for some 16,000 years, but only in last few centuries has north been consistently positioned at the top.  For example, although Christopher Columbus navigated by the North Star when he set sail for the New World, he thought of east as being the top of the world because he believed that was the direction of paradise.  North only took top honors starting with the Mercator map in 1569, which attempted to account for the curvature of the earth on a two-dimensional surface.  The map was especially useful for navigation, most of which took place in the northern hemisphere at that time, so it made sense to orient the map that way.   

To what extent is our basic orientation in space and time simply a matter of convention?  Granted, “up” and “down” are arbitrary designations if you are looking at a map.  But is there some fundamental alignment of direction with the sun and planets?  The answer is yes and no.  The planets all orbit the sun on the same plane in the direction of its rotation: counterclockwise when viewed from the sun’s north pole.  And the planets rotate on their axes in this same direction, with the notable exception of Venus and of Uranus.  Uranus rotates on its side, possibly because it got knocked off its pins after colliding with an earth-sized object long ago.  A collision may also explain why Venus’ north and south poles are essentially the reverse of most other planets relative to the plane of the Solar System.  The so-called ecliptic, which is defined by the orbits of the planets around the sun, is at a 63° angle to the Milky Way, and the universe as a whole appears to be a complete jumble.  If you whipped out your Hasselblad to take a 360° picture of the entire universe, there is no way you could determine which way is up and which is down.

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*Schmitt’s fellow Apollo 17 astronauts, Eugene Cernan and Ron Evans, also claimed to have taken the shot, but evidence suggests Schmitt, a geologist by training, was most likely the photographer.