Hello Earth!

Fewer than 600 people have ever seen our world from space and only a couple of dozen have travelled far enough away to seen the Earth as a planet against the infinity of space. All have found viewing their homeworld from beyond to be a profound experience.

This could be a scene from a science fiction film but this is real: astronaut Tracy Caldwell Dyson viewing our planet from 350 km up. She is photographed relaxing in the ISS's cupola. (Image credit: NASA)

Russian cosmonaut Vitali Sevastyanov (1935-2010), who flew on the Soyuz 9 and Soyuz 18 missions was asked by ground control whilst in orbit what he could see and he replied, “Half a world to the left, half a world to the right, I can see it all. The Earth is so small.” To see the Earth from space is a spectacular sight viewed only by an exclusive minority of the population. Many missions both manned and unmanned have travelled beyond the planet into the void of space and looked back upon the Earth. The majority of travellers venturing outside of our planet have viewed it only from low orbit as is the case for astronauts onboard the International Space Station (ISS). Only 24 men have viewed the Earth from outside low orbit as they journeyed to the Moon on the Apollo missions of the late 1960s and 1970s (nine missions, each with a crew of three went to the Moon but three astronauts, Lovell, Young and Cernan flew on two different Apollo missions). For all of those lucky men and women who have travelled great distances away from our planet, what was it like to look back at Earth?

"Say hi to the folks back home!" In a scene consigned to history, a Shuttle Orbiter departs from the ISS (Image credit: NASA)

Low Earth Orbit (LEO), that is, up to heights of 2500km (1553 miles) above the Earth’s surface, is where most artificial satellites circle the planet including the ISS which is located about 350km (218 miles) above the Earth. The Space Shuttle and Soyuz too are low orbit vehicles and used to travel and carry loads to and from the ISS. In low orbit, astronauts onboard the ISS are only able to view part of the Earth at a time. Despite only being able to view small sections of the Earth at once, sightseeing onboard the Space Station would be extremely rewarding. With the installation of the cupola on the ISS, astronauts are treated to a better view of the Earth. From this unique window astronauts can also witness shuttles docking with the station as well as serving as the main location for control of the Canadarm2, the 60-foot (18m) robotic arm attached to the Space Station.

From the ISS evidence of human activity is visible, at night cities can be easily spotted from the light pollution they create. Even during the day from low orbit, cities, major roads, dams and reservoirs can be seen. Humanity’s imprint on Earth is varied but allows observers in space to view man-made things in wonder.

This picture, apparently the first verifiable photo of the Great Wall of China made from low Earth orbit (indicated by red and yellow arrows), was taken by International Space Station Commander Leroy Chiao on Nov. 24, 2004. (Original image courtesy of Earth Sciences and Image Analysis Laboratory, NASA Johnson Space Center, modified by Armagh Planetarium)

One common belief of viewing the Earth from space or the Moon is that certain man-made objects are clearly visible. The Great Wall of China is often thought to be so large that it is the only object visible from the Moon. However this has become a space-based myth, generally it is very difficult to spot the Great Wall with the naked eye even from the ISS in LEO, never mind the moon! The material the wall is built with is very similar in colour and consistency to the surrounding land, making it quite difficult to observe this famous landmark. This theory of being able to view the Great Wall from the Moon is thought to have originated in the late 1930s, however when astronaut Alan Bean (b. 1932) travelled to the moon in 1969 on the Apollo 12 mission he said “no man made object is visible at this scale.” In 2003, Yang Liwei (b. 1965), China’s first astronaut has said although the scenery was beautiful he did not see the Great Wall.

Forty years ago, Harrison 'Jack' Schmitt was the first scientist on the Moon. Look how tiny the Earth is! (Image credit: NASA)

Those men who have travelled into the realm of space often have had quite profound realisations when seeing their home planet. James B. Irwin (1930-91) the 8th man to walk on the Moon on the Apollo 15 mission, described the Earth as appearing fragile and delicate, “as we got further and further away, it [the Earth] diminished in size. Finally it shrank to the size of a marble, the most beautiful you can imagine. Seeing this has to change a man.” Canada’s first female astronaut, Roberta Bondar (b.1945) travelled into Space on mission STS-42 in 1992, she said “To fly in space is to see the reality of Earth, alone. The experience changed my life and my attitude toward life itself. I am one of the lucky ones.” It is very difficult for the human brain to understand the huge numbers needed to explain the sheer size of the Universe. The realisation of this occurred for the Apollo 11 astronauts when they stood on the moon and blocked out the entire Earth with their thumb. It didn’t make them feel like giants but as Neil Armstrong described “very, very small.”

To experience the wonder of the Earth from space allows humans to witness the beauty in our universe. However, we don’t all need to leave the planet to appreciate the natural beauty of our home. The planet Earth is saturated with wonderful awe-inspiring sights, so take a little time out of your busy schedules to appreciate the gift from Mother Nature.

Martina Redpath, ESO (Image credit: Armagh Planetarium)

(Article by Martina Redpath)