Several Decades Ago

“Hello Arthur.” Frank Dyson greeted as he entered Arthur Eddington’s office in Cambridge Observatory in Madingley Road.
“Ah! Hello Frank. I am surprised. I thought you said you will be late to work today.”
“Yes I did”
“What changed your mind?” asked Arthur.
“The news about your experiment.”
Arthur smiled and said “Oh that! You heard it right.”

“Excellent! The theory of general relativity, which was understood by only three people in this world is finally proven to be right.” Frank said in jubillation and added “How is that for a press statement tomorrow?”
Arthur was confused and asked “Wait a minute. Who is the third one?”.
Both laughed and went to the sofas in his office.

“At least now the germans have something to be proud of.” Frank spoke as he was about to sit.
“Pardon?”
“That war is everyone’s fault.” Frank said. “That peace treaty in versailles an year ago. It was the worst treaty in the history of mankind. They are simply exploiting the germans just because they lost. I am happy that a german’s contribution to science may be used as a consolation to alleviate their pain and agony. I hope the Allied forces realize their mistake before someone in Germany ignites the revenge on all of Europe. I dont understand what happens to common sense once you become the head of a state.”

“Speaking of common sense. Can you please help me, using your common sense, to solve a problem before I publish the results?” Arthur was waiting for any silly word like this one to change the topic. He realised his mistake immediately after indirectly asking him to ellaborate on the ‘Germans being proud’ remark. Frank would have spoken for hours about the Great War otherwise.

“With pleasure.”
“Come here.” He pointed towards the table on which he was studying the photographic plates when Frank entered the room.

“Oh. The photographs of the eclipse?” Frank inquired.
“Yes. Look. I compared the normal photograph of the stars in this region with the photograph of the same region of the sky when its behind the sun during this may’s eclipse in Principe. So if Einstein was right, then the stars in the photograph during eclipse should appear slightly out of position when compared to the photograph of the stars of the same region taken any other time.”

“Out of position?” Frank interrupted as he was unsure on how to intepret Einstein’s claim of gravity affecting light rays.

“Yes because the light rays that were initially not coming towards the Earth would be bent inwards as they pass our massive sun. So they should appear a bit out of position than they usually are.” Arthur explained.
Frank nodded.
“All the stars appeared to have shifted by the amount Einstein predicted. But this dot here is a problem.” Arthur pointed to a dot on the photograph.

“That dot is..?” Frank paused to hear the name of the dot rather a star.
“I do not know.” Arthur said.
“A new star may be?”
“I highly doubt it.” Arthur added in reply to Frank’s confused look.”That dot was never there. I took six photographs of the region during other times and did not find this dot in any one of those photographs. In such cases, it should have been one of the seven planets. But it is not any of them.”

“Any idea how far it was?” Frank smiled with a curious look.
“Fortunately yes. You know that we took two observations: one in Principe, off the coast of Africa and another one in Sobral, Brazil. These two are more than four thousand kilometers apart. So with both these observation sites, we can form a triangle with this dot. I triangulated its position and found that its just two Astronomical Units away from us.”

“What!! Two astronomical units in the direction of our sun?” Frank was shocked.
Arthur clarified “That means, on the day of that eclipse, this unidentified dot is diametrically opposite to our Earth in our own orbit.”