Over Christmas, I was reading Carl Sagan’s novel CONTACT and enjoyed his thoughts on SETI—the search for extraterrestrial life. One of the points Sagan makes is that any alien intelligence would be far more advanced than humans and should have already colonized the galaxy.
Sagan’s reasoning is based on the fact that we have emerged rapidly as a technological/scientific civilization.
Within 10,000 years, we’ve gone from pushing rocks around the desert to build extravagant tombs to walking on our moon. Taking a longer view, our recent progress is even more impressive. For at least 1.8 million years, we have been using stone implements, hand-held axes that remained largely unchanged for 99% of that time. In essence, we were at a technological stand still until some point in the last 10,000 years. “We” stalled for longer than Homo sapiens have existed as a species! Then, in what equates to less than 1% of our tool-using history, BOOM… we’re walking on the Moon. That’s quite extraordinary.
And our progress continues to advance at an astonishing pace. In the last hundred years or so, we’ve banished such insidious diseases as smallpox and polio that plagued our species for thousands of years. We’ve travelled into space, explored the depths of our oceans, invented computers, cured diseases, transformed our economies, and in the midst of all this it is easy to see our progress as unrelenting, almost inevitable, but the truth is far different.
Although our progress may seem exponential and always positive, it is actually the result of overlapping technologies following what’s described as an S-curve of efficiency. Steam gave way to oil, as an example, while propeller aircraft gave way to jet engines. As one technology reached its peak, another newer technology took over, propelling us still further on. But is such technological growth sustainable? Are there physical limits?
Ah…. this is where the concept of SETI comes into the discussion. For over fifty years, we have wondered, “Where are they?” By our reckoning, the heavens should be buzzing with extraterrestrial activity, but all we hear is silence. Why? If we can progress so rapidly, why couldn’t anyone else? And given our rapid growth over what is an astonishingly small period of time, other intelligent species should have already had a good headstart on populating the galaxy, but there’s no one out there. Why?
One possible answer lies with the S-curve of engineering efficiency. There’s no way a steam powered car could ever outrun even a modest modern car, or a propeller plane a jet. Once these technologies reached their limit, they had to be superseded or the peak of efficiency would never increase.
The lower portion of the curve marks how our learning grows, and we begin mastering the technology and improving its efficiency, but eventually every technology reaches its limits—the point where no more efficiency can be gained.
When it comes to the universe at large, there’s two very pertinent limits. On the sub-atomic scale, the Planck length. On the large scale, the speed of light. It may be that these physical constraints simply cannot be overcome by switching from propellers to jets (or whatever the equivalent may be).
Breaking the speed of light is not simply an engineering problem as breaking the speed of sound was. As much as I love a good scifi book/movie, anyone that tells you the speed of light will one day be breached really doesn’t understand what they’re talking about. The speed of light is the speed of reality.
E = mc2 is the most famous equation in science, but it’s not the only way Einstein and the scientists that worked with him understood this principle. They also thought of it as m = E/c2. In Einstein’s words, “It appears far more natural to consider every inertial mass as a store of energy.” In other words, we can no more travel faster than the speed of light than light itself can travel faster than the speed of light.
What’s more, even if we could travel close to that speed, impact with dust particles, even with individual atoms scattered within the vacuum of space would be disastrous. At 99% of the speed of light, a single gram of “stuff” out there would generate the kind of energy unleashed at Hiroshima.
Stars are really far apart. Four light years is a deceptively simple way of saying 2.469e+13 miles. Travelling between stars requires enormous patience at sub-light speeds, and is grossly impractical, especially when you consider that whatever energy you put into starting your journey also has to be put into stopping at the other end.
Just as we’re currently struggling to justify a “space economy” any advanced alien civilization would struggle to justify an “interstellar economy.” There’s no doubt it could be done, but it is anything but routine. Any colonies would be effectively in a state of permanent isolation. Rather than being the nirvana of space travel, interstellar colonization may simply be a pipedream for all advanced civilizations.
The physical limits of technology is an interesting way to consider SETI, and may help explain the silence we observe. We may be bound to these islands in the sky we call stars.
Given the resourcefulness of humanity, I have no doubt we’ll one day develop generation ships, or automated ships that can grow-humanity-on-demand once they find a suitable planet, but the pragmatist in me outweighs the romantic. Such voyages will be extremely risky and highly long term propositions that may have minimal practical benefits, and perhaps that’s why we don’t see ET everywhere we look. They may be the exception rather than the norm. Perhaps there are dozens, even hundreds of advanced alien civilizations out there, but they’re isolated in far-flung regions and are unable or unwilling to venture between stars.