peace rally posters, a “Haight is Love” sign, FBI ten most-wanted posters torn down from a post office with photos of famous antiwar activists circled in blue magic-marker, a huge peace symbol in passion-pink. Some of the posters were illuminated with black light and luminesced in impossible colors. The air was musty with incense and the banana-sweet smell of dope. In one corner a record player played Sergeant Pepper’s Lonely Hearts Club Band on infinite repeat. Whenever one copy of the album got too scratchy, inevitably one of Dancer’s friends would bring in another. He never locked the door. “Somebody wants to rip me off, well, hey, they probably need it more than I do anyway, okay? It’s cool.” People dropped by any time of day or night.
I let my hair grow long. Dancer and Lisa and I spent that summer together, laughing, playing guitar, making love, writing silly poems and sillier songs, experimenting with drugs. That was when LSD was blooming onto the scene like sunflowers, when people were still unafraid of the strange and beautiful world on the other side of reality. That was a time to live. I knew that it was Dancer that Lisa truly loved, not me, but in those days free love was in the air like the scent of poppies, and it didn’t matter. Not much, anyway.
NOTES FOR A LECTURE ON TIME TRAVEL (continued)
Having postulated that all of space was filled with an infinitely dense sea of negative energy particles, Dirac went on further and asked if we, in the positive-energy universe, could interact with this negative energy sea. What would happen, say, if you added enough energy to an electron to take it out of the negative energy sea? Two things: first, you would create an electron, seemingly out of nowhere. Second, you would leave behind a “hole” in the sea. The hole, Dirac realized, would act as if it were a particle itself, a particle exactly like an electron except for one thing: it would have the opposite charge. But if the hole ever encountered an electron, the electron would fall back into the Dirac sea, annihilating both electron and hole in a bright burst of energy. Eventually they gave the hole in the Dirac sea a name of its own: “positron.” When Anderson discovered the positron two years later to vindicate Dirac’s theory, it was almost an anticlimax.
And over the next fifty years, the reality of the Dirac sea was almost ignored by physicists. Antimatter, the holes in the sea, was the important feature of the theory; the rest was merely a mathematical artifact.
Seventy years later, I remembered the story my transfinite math teacher told and put it together with Dirac’s theory. Like putting an extra guest into a hotel with an infinite number of rooms, I figured out how to borrow energy from the Dirac sea. Or, to put it another way: I learned how to make waves.
And waves on the Dirac sea travel backward in time.
Next we had to try something more ambitious. We had to send a human back farther into history, and obtain proof of the trip. Still we were afraid to make alterations in the past, even though the mathematics stated that the present could not be changed.
We pulled out our movie camera and chose our destinations carefully.
In September of 1853 a traveller named William Hapland and his family crossed the Sierra Nevadas to reach the California coast. His daughter Sarah kept a journal, and in it she recorded how, as they reached the crest of Parker’s ridge, she caught her first glimpse of the distant Pacific ocean exactly as the sun touched the horizon, “in a blays of cryms’n glorie,” as she wrote. The journal still exists. It was easy enough for us to conceal ourselves and a movie camera in a cleft of rocks above the pass, to photograph the weary travellers in their ox-drawn wagon as they crossed.
The second target was the great San Francisco earthquake of 1906. From a deserted warehouse that would survive the quake – but not the following fire – we watched and took
I let my hair grow long. Dancer and Lisa and I spent that summer together, laughing, playing guitar, making love, writing silly poems and sillier songs, experimenting with drugs. That was when LSD was blooming onto the scene like sunflowers, when people were still unafraid of the strange and beautiful world on the other side of reality. That was a time to live. I knew that it was Dancer that Lisa truly loved, not me, but in those days free love was in the air like the scent of poppies, and it didn’t matter. Not much, anyway.
NOTES FOR A LECTURE ON TIME TRAVEL (continued)
Having postulated that all of space was filled with an infinitely dense sea of negative energy particles, Dirac went on further and asked if we, in the positive-energy universe, could interact with this negative energy sea. What would happen, say, if you added enough energy to an electron to take it out of the negative energy sea? Two things: first, you would create an electron, seemingly out of nowhere. Second, you would leave behind a “hole” in the sea. The hole, Dirac realized, would act as if it were a particle itself, a particle exactly like an electron except for one thing: it would have the opposite charge. But if the hole ever encountered an electron, the electron would fall back into the Dirac sea, annihilating both electron and hole in a bright burst of energy. Eventually they gave the hole in the Dirac sea a name of its own: “positron.” When Anderson discovered the positron two years later to vindicate Dirac’s theory, it was almost an anticlimax.
And over the next fifty years, the reality of the Dirac sea was almost ignored by physicists. Antimatter, the holes in the sea, was the important feature of the theory; the rest was merely a mathematical artifact.
Seventy years later, I remembered the story my transfinite math teacher told and put it together with Dirac’s theory. Like putting an extra guest into a hotel with an infinite number of rooms, I figured out how to borrow energy from the Dirac sea. Or, to put it another way: I learned how to make waves.
And waves on the Dirac sea travel backward in time.
Next we had to try something more ambitious. We had to send a human back farther into history, and obtain proof of the trip. Still we were afraid to make alterations in the past, even though the mathematics stated that the present could not be changed.
We pulled out our movie camera and chose our destinations carefully.
In September of 1853 a traveller named William Hapland and his family crossed the Sierra Nevadas to reach the California coast. His daughter Sarah kept a journal, and in it she recorded how, as they reached the crest of Parker’s ridge, she caught her first glimpse of the distant Pacific ocean exactly as the sun touched the horizon, “in a blays of cryms’n glorie,” as she wrote. The journal still exists. It was easy enough for us to conceal ourselves and a movie camera in a cleft of rocks above the pass, to photograph the weary travellers in their ox-drawn wagon as they crossed.
The second target was the great San Francisco earthquake of 1906. From a deserted warehouse that would survive the quake – but not the following fire – we watched and took
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