Alan Lightman - Einstein's Dreams

The book is a collection of 3-4 page thoughts experiments involving time and human memory. Its back cover claims it's a "fictional collage of stories dreamed by Albert Einstein in 1905", but if Einstein could have peered into the future and had seen this book, he would have probably hanged little Lightman from the hour hand of a giant clock.


The thought experiments are set in picturesque Berne, Switzerland, in 1905. However, ideas are naively, narrowly and summarily explored, and inconsistencies abound. For example, in one story, time is stopped, and people only experience images: dinner on the table, the touch of a lover. But how would they evolve to experience any image at all, if time is stopped?

Another story, on the locality of time (p. 120), could explore the idea of connecting locations where time passes at wildly different rates via electrical or even radio signals (which had already gone commercial by 1905), but fails short.

The story on page 107, which asserts that time is discrete and stops every micro-second before resuming, but for a short enough interval that the pause is imperceptible. However, this misses a major point, discussed by Greg Egan's Permutation City: the rate at which consecutive quantum events occur in a closed universe is irrelevant for a consciousness existing in that universe. In other words if we simulate an AI in a computer, the speed of that computer doesn't matter for the AI (as long as it doesn't communicate with the outside world). Indeed, the AI could be simulated on an abacus and have the same perception of "time".

Good picks

The story titled "20 may 1905" (page 61) examines a world where people's memories are erased nightly:

When it is time to return home at the end of the day, each person consults his address book to learn where he lives. [...] Arriving home, each man finds a woman and children waiting at the door, introduces himself, helps with the evening meal, reads stories to his children. Likewise, each woman returning from her job meets a husband, children, sofas, lamps, wallpaper, china patterns. Late at night, the wife and husband do not linger at the table to discuss the day's activities, their children's school, the bank account. Instead, they smile at one another, feel the warming blood, the ache between the legs as when they met the first time fifteen years ago. They find their bedroom, stumble past family photographs they do not recognize, and pass the night in lust. For it is only habit and memory that dulls the physical passion. Without memory, each night is the first night, each morning is the first morning, each kiss and touch are the first.


Given the (necessary) superficiality of the thought experiments, the book is much better as material for finding out why various fantastic theories about time would be self-contradictory.

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