‘That Hooker telescope of yours is quite spectacular. I can imagine how much fun young Humason and you have with it. Your tour was full of such lovely details too, just like your papers.’
Edwin Hubble laughed. ‘Come, come, Albert. This flattery doesn’t suit you. It would be an honour, if you would tell me what you really think of my work.’ He emphasized the word ‘really’.
It was a pleasant afternoon in January in 1931. Mount Wilson Observatory was playing host to a group of special guests. One of these guests, the most special one in the eyes of Hubble, was his respected colleague, the renowned scientist, Albert Einstein. The tour was done and the two scientists had some time alone. They had exchanged letters in the last decade or so but Hubble felt that many things had been left unsaid in the written word.
‘Well, you must know this already. But I did tell de Sitter long ago that the possibilities of an ‘expanding’ universe seemed quite senseless to me. I know you have proof but I still find it hard to make my peace with it,’ said Einstein.
Hubble was quiet. He put his coffee mug on the desk and walked to the windows of his office.
‘Look, Albert. We are over five thousand feet high. It’s such a nice day, that even the Santa Catalina Island is visible. It was a day like this, a beautiful Californian day with each star refusing to compromise on showcasing its brilliance, when I first discovered that the redshift of distant galaxies increased as a linear function of their distance. Of course I couldn’t believe it either. Our magnificent universe was expanding? It was a mad thought much bigger than any of us. How was I going to change people’s minds about what they thought they already knew? How was I going to tell people that the universe wasn’t as static as they had imagined? But despite these doubts, I was thrilled. It boggled my mind and ignited my imagination. I can tell you now that I am convinced, our magnificent universe is expanding.’
Einstein took a sip of his coffee. ‘We have to be a bit mad as scientists. I don’t blame you.’
‘Some would say that my madness was consistent with yours,’ said Hubble. ‘Well, all of your madness except the bit that came up with the lambda. Many people didn’t believe my discovery because it didn’t fit with your equations of relativity. The existence of your cosmological constant, lambda suggested the universe was static.’
‘If you recall, that crazy Belgian Catholic priest, Lemaître had proposed the same concept of the expanding universe. And his work actually fit quite well into my theories of relativity.’
‘Why then, were you so critical of a non static universe? You must have been aware that the only way people would believe Lemaître’s and my theories was if you got rid of the Cosmological Constant from your field equations of special relativity.’
‘I must admit that your proof of the redshift of distant nebulae has smashed my old construction like a hammer blow,’ replied Einstein. Hubble’s eyebrows shot up with expectation. Einstein went on, ‘When I first came up with the special theory of relativity, I was amazed, if I may say so myself, by their simplicity and beauty. But assuming the universe was not static; my equations were telling me that the universe would collapse into itself or keep expanding. I will admit that the constant lambda was necessary for the purpose of making possible a quasi-static distribution of matter.’
Hubble smiled his first smile that afternoon. ‘Am I hearing what I think I’m hearing?’
‘You will hear what you wish to hear, my dear Edwin. I have been thinking for a while now that the constant has to go. Everything points in the direction of an expanding universe. I will just have to admit to the world that I made an error in my calculations. I won’t deny that I’m a little pleased to have my symmetric equations of relativity back. You have my congratulations and my thanks for your persistence. I still need to think about eliminating the constant completely but I feel I’m moving closer in that direction.’ He looked at his pocket watch. ‘And now, it’s time to go. Thank you for a delightful time. I’m sure we will see each other again.’
The two men shook hands and walked out of the door together. The rest of the group was at the end of the corridor. Just as they arrived towards them, Hubble said in a quiet tone to Einstein, ‘I know what you always say, Albert, that anyone who has never made a mistake has never tried anything new. Your instinct is other worldly. As a universe, we might be expanding, and you will be right to dismiss your constant so we can share this discovery with the world and they will believe us...but…’
‘But, you wouldn’t be surprised if the cosmological constant came back again one day?’ Einstein laughed. ‘You certainly have a charming sense of humour, Edwin. But who is to say? You never know what can happen in this world, or where we are going.’
***
Hubble’s theories supported the scientist Lemaître in his claim that the universe is the ‘ashes and smoke of bright but very rapid fireworks;’ a spark that ignited the ‘Big Bang Theory’.
In 1998, many years after Einstein’s visit to Hubble at Mount Wilson and his dismissal of the constant ‘lambda’ from his equations of relativity, two independent teams of astronomers, the Supernova Cosmology Project and the High-z Supernova Search Team, announced a remarkable discovery - the rate at which the universe is expanding is accelerating. This discovery suggested the existence of ‘dark energy’ in the universe, something that could only be proven by re-introducing Einstein’s lambda back into his equations. Some might say that the cosmological constant had come back.
Note - Part 2 of an unusual project. My friend gave me the task of writing a fictional preface and epilogue to his PhD Thesis. This is the epilogue. He gave me a premise - the encounter between Hubble and Einstein where they conversed about the possibility that Einstein might have been wrong about his 'cosmological constant' in his theory of relativity which implied that the universe wasn't static, something that people had believed for centuries. By the time of this encounter, Hubble had proof that the universe was expanding.