This one is a little different, plus it's kind of a long post. It also contains nerdy science stuff so give it a pass if this isn't your thing.
In May of 1985, cosmologist Stephen Hawking gave a public lecture at Fermilab (Enrico Fermi National Accelerator Laboratory) in Batavia, Illinois to about 150 audience members, mostly made up of other scientists. At the time, Hawking was well known by his colleagues as being among the top level of physicists, but was relatively unknown by the general public. He had yet to write his best selling book, "A Brief History of Time" and was known for his groundbreaking theories on black holes and singularity theorems.
Penrose–Hawking singularity theorems - Wikipedia
The subject of his lecture was his proposal that that there was no singularity at the beginning of the universe, contrary to the accepted Big Bang models of the time. This revision followed from quantum mechanics, in which general relativity must break down at times less than the Planck Time, hence general relativity cannot be used to show a singularity.
He further suggested that in the far distant future, the universe would stop expanding and then begin to contract again, under gravity, and eventually return to a state identical to the original Big Bang. He predicted mathematically that this contraction would be symmetrical in time to the earlier expansion, and that time would run in the negative direction with every event in the history of the universe repeating itself backwards.
I was a junior in high school in 1985 and something of a science geek. Our school "physics club" informed us about the lecture and a few of us attended the event at Fermilab, which was only about 20 miles away. We took seats in the back of the auditorium and waited until the scheduled start time for the lecture. Only about 1/3 of the 500 or so seats were filled. I remember Nobel prize winner Leon Lederman was there. One of my friends said he recognized a couple of other famous scientists but I didn't know who they were.
Suddenly a hush fell over the crowd and I watched in astonishment as a very frail man was being carried down the steps of the aisle to our left like a sack of groceries and unceremoniously dumped in the wheelchair in the center of the stage. Stephen Hawking had arrived.* One of his assistants settled him in and he began to speak.
This was just a few months before he lost his voice so he could still vocalize, but he needed an interpreter for his audiences to understand his words. He outlined his proposal about singularities and time symmetry and I discovered that the first two sentences would be the last ones that I would understand for the rest of his talk. His assistant wrote a multitude of equations on the board that were almost entirely Greek letters and other, unfamiliar hieroglyphs. Occasionally, the scientists in the audience would simultaneously get excited and start murmuring among themselves as Hawking made some point that apparently impressed them. My friends and I had no idea what was going on. After the lecture, Hawking answered questions from the audience and I didn't even understand these questions, much less the answers.
Despite that, I enjoyed the opportunity to be present there and only appreciated the significance of the event after Hawking's book came out and even years later when I leaned enough about cosmology to realize that this lecture was a significant milestone in the field of cosmology.
Interestingly, Hawking changed his mind only a year later and dismissed the idea of time running backwards. He is also now unsure about whether or not singularities exist as infinitely small and infinitely dense objects or if they have a finite size and density. Physicists are still debating this question.
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* The lecture hall had no provision for wheelchair access and no one had thought to check. When it was realized that the only way to reach the stage was down the steps between rows of seats, his two scientist friends accompanying him suggested they carry Hawking and his wheelchair separately. Hawking refused, claiming it was too undignified. His friends concluded there was no alternative so the picked him up out of his chair and carried him down the stairs despite his protests.