How fast we go affects how we perceive time. That lesson was implicit in the mathematics of Special Relativity, but at the speed most of us live our lives, easily describable in Newtonian terms, we could hardly recognize it. Get going at a substantial percentage of the speed of light, though, and everything changes. The occupants of a starship moving at close to 90 percent of the speed of light age at half the rate of their counterparts back on Earth. Push them up to 99.999 percent of c and 223 years go by on Earth for every year they experience.

Thus the ‘twin paradox,’ where the starfaring member of the family returns considerably younger than the sibling left behind. Carl Sagan played around with the numbers in the 1960s to show that a spacecraft moving at an acceleration of one g would be able to reach the center of the galaxy in 21 years (ship-time), while tens of thousands of years passed on Earth. Indeed, keep the acceleration constant and our crew can reach the Andromeda galaxy in 28 years, a notion Poul Anderson dealt with memorably in the novel Tau Zero.


Image: A Bussard ramjet in flight, as imagined for ESA’s Innovative Technologies from Science Fiction project. Credit: ESA/Manchu.

Not long after Monday’s post on fast spacecraft I received an email from a young reader who wanted to know a bit more about humans and speed. He had been interested to learn that the fastest man-made object thus far was the Helios II solar probe, while Voyager I’s 17 kilometers per second make it the fastest probe now leaving the system, well above New Horizons’ anticipated 14 kilometers per second at Pluto/Charon. But that being the case for automated probes, what was the fastest speed ever attained by a human being?

Speeds like this are well below those that cause noticeable relativistic effects, of course, but it’s an interesting question because of how much it changed at the beginning of the 20th Century, so let’s talk about it. Lee Billings recently looked into speed in a fine essay called Incredible Journey: Can We Reach the Stars Without Breaking the Bank? and found that in 1906, a man named Fred Marriott managed to surpass 200 kilometers per hour in (the mind boggles) a steam-powered car at Daytona Beach, Florida. This is worth thinking about because Lee points out that before this time, the fastest anyone could have traveled was 200 kilometers per hour, which happens to be the terminal velocity of the human body as it is slowed by air resistance.

So the advent of fast machines finally changed the speed record in 1906, and it would be a scant forty years later that Chuck Yeager pushed the X-1 up past 1000 kilometers per hour, faster than the speed of sound. I can remember checking out a library book back in the 1950s called The Fastest Man Alive. Before I re-checked the reference so I could write this post, I was assuming that the book had been about X-15 pilot Scott Crossfield, but I discovered that this 1958 title was actually the story of Frank Kendall Everest, Jr., known as ‘Pete’ to his buddies.


Everest flew in North Africa, Sicily and Italy and went on to complete 67 combat missions in the Pacific theater, including a stint as a prisoner of war of the Japanese in 1945. If there was an experimental aircraft he didn’t fly in the subsequent decade, I don’t know what it was, but if memory serves, the bulk of The Fastest Man Alive was about his work with the X-2, in which he reached Mach 2.9 in 1954. Everest was one of the foremost of that remarkable breed of test pilots who pushed winged craft close to space in the era before Gagarin.

But to get back to my friend’s question. Lee Billings identifies the fastest humans alive today as ‘three elderly Americans, all of whom Usain Bolt could demolish in a footrace.’ These are the Apollo 10 astronauts, whose fiery re-entry into the Earth’s atmosphere began at 39,897 kilometers per hour, a speed that would take you from New York to Los Angeles in less than six minutes. No one involved with the mission would have experienced relativistic effects that were noticeable, but in the tiniest way the three could be said to be slightly younger than the rest of us thanks to the workings of Special Relativity.

Sometimes time slows in the way we consider our relation to it. I noticed an interesting piece called Time and the End of History Illusion, written for the Long Now Foundation. The essay focuses on a paper recently published in Science that asked participants to evaluate how their lives — their values, ideas, personality traits — had changed over the past decade, and how much they expected to see them change in the next. Out of a statistical analysis of the findings came what the researchers are calling an ‘End of History Illusion.’

The illusion works like this: We tend to look back at our early lives and marvel at our naïveté. How could we not, seeing with a certain embarrassment all the mistakes we made, and knowing how much we have changed, and grown, over the years. One of the study authors, Daniel Gilbert, tells The New York Times, “What we never seem to realize is that our future selves will look back and think the very same thing about us. At every age we think we’re having the last laugh, and at every age we’re wrong.”

The older we get, in other words, the wiser we think we are in relation to our younger selves. We always think that we have finally arrived, that now we see what we couldn’t see before, and assume that we can announce our final judgment about various aspects of our lives. The process seems to be at work not only in our personal lives but in how we evaluate the world around us. How else to explain the certitude behind some of the great gaffes of intellectual history? Think of US patent commissioner Charles Duell, who said in 1899: “Everything that can be invented has been invented.” Or the blunt words of Harry Warner: “Who the hell wants to hear actors talk?”

The Long Now essay quotes Francis Fukuyama, who wrote memorably about the ‘end of history’ and French philosopher Jean Beaudrillard, who sees such ideas as nothing more than an illusion, one made possible by what he called ‘the acceleration of modernity.’ Long Now adds:

Illusion or not, the Harvard study shows that a sense of being at the end of history has real-world consequences: underestimating how differently we’ll feel about things in the future, we sometimes make decisions we later come to regret. In other words, the end of history illusion could be thought of as a lack of long-term thinking. It’s when we fail to consider the future impact of our choices (and imagine alternatives) that we lose all sense of meaning, and perhaps even lose touch with time itself.

We’ve come a long way from my reader’s innocent question about the fastest human being. But I think Long Now is on to something in talking about the dangers of misunderstanding how we may think, and act, in the future. By assuming we have reached some fixed goal of insight, we grant ourselves too many powers, thinking in our hubris that we are wiser than we really are. Time is elastic and can be bent around in interesting ways, as Einstein showed. Time is also deceptive and leads us as we age to become more doctrinaire than can be warranted.

Sometimes, of course, time and memory mingle inseparably. I’m remembering how my mother used to sit on the deck behind her house when I would go over there to make her coffee. We would look into the tangle of undergrowth and trees up the hill as the morning sun sent bright shafts through the foliage, and as Alzheimer’s gradually took her, she would often remark on how tangled the hillside had become. I always assumed she meant that it had become such because she was no longer maintaining it with the steady pruning of her more youthful years.

Then, not long before her death, I suddenly realized that she was not seeing the same hill that I was. At the end of her life, she was seeing the hill in front of her house in a small river town in Illinois. Like her current hill, it rose into the east so that while the house stood in shadow, sunlight would blaze across the Mississippi to paint the farmlands of Missouri on the bright mornings when she would get up to walk to school. When I went back there after her funeral, the hill was still open as she had remembered it, grassy, free of brush, though the house was gone. It was the hill she had returned to in her mind after 94 years, as vividly hers in 2011 as it had been in 1916. In such ways are we all time travelers, moving inexorably at the velocity of thought.