120-Year-Old Space Photos Found In Cardboard Box

How space photos from 1919 helped prove Einstein’s Theory of Relativity.

The inquisitive mind of astronomer Holder Pedersen noticed cardboard boxes from the old Østervold Observatory in the basement of the Niels Bohr Institute in Denmark.

Now retired, he still visits the University of Copenhagen to work on his own projects. In the basement making a cup of tea he saw some boxes and decided to investigate.

He uncovered century-old photos, dating back as early as 1885, taken at the Østervold Observatory are of Jupiter, phases of the moon and most interestingly a lunar eclipse from 1919. They had been stored there since the observatory closed in 1996.

Glass plates from 1909–1922 show the Moon in different phases.

In 1915 Albert Einstein announced his general theory of relativity. It describes the relationship between space, time, mass and gravity. If proved, it would mean, for example, that light from a distant star passing massive objects such as galaxies would be bent by the gravity of the object.

The problem with this theory was it was difficult to test. Arthur Eddington, one of the most prominent astronomers who discovered the link between the mass of stars and their brightness among other things, came up with a plan.

He realised the natural cosmic event of a solar eclipse, where the Sun moves behind the Moon, would provide the conditions needed to test Einstein’s theory. He travelled to Sorbal in Brazil to photograph the 29 May 1919 eclipse and the stars that could be seen close to the sun in dim light.

What he found, when the photo was compared to other images without the sun in front, was the Sun’s gravity did, in fact, bend light from the underlying stars, giving Einstein the first reliable evidence for his theory. While it is a copy of the original, the copy is still rare and historically interesting.

The solar eclipse from 1919, which the English astronomer Arthur Eddington used as evidence for Albert Einstein’s general theory of relativity.

Photos such as these were taken on photography plates which preceded film. They were used in astrophotography as late as 1990 because they do not deform during development and their rigid structure allowed for an even exposure.

The thin photographic plates are made of glass with photosensitive emulsion on its active face. The 16cm size is due to the focal planes of the major telescopes used at the time.

Astronomer Holger Pedersen

The images survived in the cardboard box because the plates are highly stable in environmental changes. However, they are fragile and the emulsion can introduce distortions of the image making the high quality of these image more impressive.

The Østervold telescope from 1895. It is a double-lensed telescope, where there was one for visual use and one for photographic recordings on 16cm glass plates. The glass plates are placed in the grey cartridge and then you look in the eyepiece up to the right.

More than 150 images were found, many taken by Carl Burrau who worked at the Østervold Observatory, and are irreplaceable. Holger Pedersen hopes to get funding to have the images digitised for the Natural History Museum of Denmark.

The vast changes in technology since then have expanded our horizons, our timelines of events and changed the way we view space, and our world. We now have people orbiting the earth at all times, and have equipment that takes photos that could not have even been dreamed about back then.

It makes me wonder what else has been stored in boxes, existence forgotten after so many years.

Images by The University of Copenhagen Faculty of Science / Website

Originally published on Bokeh.