Jim Mastro

Writing, and all things in between

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Is The Universe Hiding Something?

Not very long ago, astronomers and astrophysicists realized something was wrong with the Universe. The Universe is expanding, but the speed of that expansion is increasing. It shouldn’t be. The gravitational pull of the Universe’s mass should be slowing it down, or at least it should be maintaining the same speed. For it to be speeding up, something has to be accelerating it.

In addition, the stars on the outer fringes of galaxies rotate around the galactic center at a much faster rate than they should, based on the amount of matter in the galaxy (according to both classical and modern physical theory).

To explain the first of these phenomena, physicists have postulated that some sort of energy suffuses the Universe but is currently undetectable, and this energy is pushing galaxies apart at an ever increasing rate. They call it “dark energy.” To explain the second phenomenon, they postulate that there is another form of matter that is also currently undetected. This so-called “dark matter” surrounds galaxies and provides the additional mass (and gravitational influence) required to explain the curious motion of the stars.

Physicists have come up with a variety of hypothetical particles that they think could comprise dark matter. Some of it could be hot (i.e., fast moving), but if all of it were hot it wouldn’t explain the observed motion of stars and galaxies. So most dark matter theorists think at least 95% of it is cold, i.e., slow moving. Of this cold dark matter, they feel the most likely candidate is a “weakly interacting massive particle,” or WIMP. These WIMPs would rarely or never interact with regular matter, or even with other WIMPs, but they would form clouds whose gravitational attraction would form stars into galaxies and affect the stars’ rotational velocities.

Other possible dark matter particles might be self-interacting via dark electromagnetism that allows them to exchange dark photons and form dark atoms. The dark electromagnetism would not affect “normal” matter, but the dark matter would form disc-like structures alongside the disc of normal matter in galaxies, and their gravitational influence would also affect the motion of normal matter.

Several experiments are underway to try and detect at least some dark matter particles, especially WIMPs, but so far these attempts have been unsuccessful.

In reading about all this, I was struck by the idea that maybe physicists were bending over backwards to come up with increasingly complex theories to explain their observations when a simpler one might be better. In a way, it reminded me of the way astronomers in the 16th Century developed epicycles to explain the motion of planets in order to adhere to the notion that the Earth was the center of the Universe. When Copernicus showed that the Earth revolved around the sun and not the other way around, the motion of the planets was explained much more simply and elegantly.

Some physicists have made this same comparison, though they reject it because the idea of dark matter explains observations so well. Well, so did epicycles, at the time.

I think there might be another explanation that does the job without inventing a whole menagerie of new but undetectable particles.

For some time now, physicists have entertained the idea that we might live in a multiverse. That is, in addition to the universe we inhabit and which we can observe, there might be other universes, perhaps even an infinite number of universes. What if one of those universes were right next to ours? What if both our universes occupied the same meta-space, with gravitational effects from each one leaking across the dimensional divide to affect the other?

Current astrophysical theory makes this a possibility, and it doesn’t require conjuring up what seems to be a whole menagerie of semi-mythical particles and energies.


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The Missing Factor

Interesting things often happen to me in the transitional phase between sleep and wakefulness. In that twilight zone where I am neither fully asleep nor fully awake, it seems that the intuitive, creative side of my brain is most active. During that time, solutions to vexing problems (usually related to a writing project) come to me, seemingly out of the blue. Other thoughts also occur to me, often regarding subjects I wasn’t even aware I was thinking about.

That happened again just the other morning. But before I reveal it, a little background.

Whether or not life is inevitable, given the right circumstances, is a problem that has vexed biologists (and philosophers) for some time. Since we only have one example – Earth – it is impossible to draw any firm conclusions. That is one reason why so much effort continues to go into searching for evidence of life beyond our planet. Much of this effort is directed at Mars right now, but there is also considerable effort to identify Earth-like planets around other stars. In addition, the Search For Extraterrestrial Intelligence (SETI) project continues its decades-long search for signs of another civilization. If any hard evidence of extraterrestrial life were to be found, even simple, unicellular life, it would change the equation dramatically.

So far, however, there has been nothing firm. So scientists are forced to base their conjectures on what can be found here, on our own planet. That evidence is certainly suggestive. Bacterial and other unicellular life has been found thriving in such unlikely places as undersea thermal vents, near-boiling hot springs, within rocks in Antarctica, in perpetually dark and frigid Antarctic lakes, and even miles underground. If life can exist in those places, it seems it can exist anywhere.

Many of these places are proposed as the place where life may have originated, since many of them mirror conditions on our planet when it was very young, with its extremes of temperature and anoxic, even toxic, environments. Other scientists propose that life originated elsewhere and the Earth was seeded by bacteria hitching rides on comets and meteors. Recent evidence that some bacteria can survive prolonged exposure to the frigid airlessness of space gives credence to that view. However, that doesn’t solve the problem of how life originated. If it didn’t evolve here but was simply introduced here, it still had to evolve somewhere. Claiming that Earth was seeded just kicks the can down the road.

Nonetheless, based on the foregoing, it seems increasingly likely that life is indeed inevitable. If and when we do discover extraterrestrial life, that argument becomes much stronger. We may be forced to conclude that the physical laws that organize our universe make it impossible for life NOT to develop.

That’s where the “missing factor” mentioned in the title of this post comes in. It was this thought that suddenly occurred to me in my half-awake state: If the physical structure of our universe does indeed make life inevitable, then physicists must take that into account. No theory meant to describe our physical universe could be considered complete without factoring in its propensity to produce life. In other words, the inevitability of life might be as fundamental to the structure of our universe – and as fundamental to the equations that describe that structure – as the relationship between matter and energy or the existence of photons and neutrinos.

I encourage physicists to develop such a theory. Like any theory, for it to be valid it must make predictions that are testable. Equations could be developed that would predict under what conditions and how frequently life would form, based on the known physical structure of the universe. We will continue to search for extraterrestrial life, and sooner or later (if our civilization survives long enough), we will either discover enough of it to confirm the theory, or we will find nothing at all and the theory will be ruled invalid.

I predict the former.

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Have They really Been Here Before? Part 1

I have long been fascinated by the way events (even apparently minor events) can reverberate through time, affecting subsequent events hundreds, thousands, or even tens of thousands of years later. A recent example is when 19-year-old Serbian nationalist Gavrilo Princip assassinated Archduke Franz Ferdinand of the Austro-Hungarian Empire in Sarajevo, Bosnia on June 28, 1914, which triggered World War I. Events following that war led directly and (in retrospect) inevitably to World War II, which led directly to the Cold War and all the little proxy wars, coups, assassinations, and CIA covert operations to “stop the spread of communism” that the Cold War engendered. The consequences of all of those things affect us even today, particularly in the Middle East. One person’s actions, one bullet, literally changed the course of history for the entire world, resulting in millions of deaths — and the count keeps rising.

Granted, this example only covers decades, but I’m certain it would be easy to find single events hundreds or thousands of years ago that have led directly to the way things are today.

It is precisely this concept that I explored in the Children of Hathor trilogy. In that story, all the hundreds of human races in the galaxy are descended from an extinct progenitor race, the Hathor. 800,000 years ago. a single action by a single one of these Hathor altered the course of history for every race in the galaxy. As a direct result, some of those Hathor-spawned races visited Earth thousands of years ago, helped elevate early humans to civilization, and interbred with them. Now those actions have directly affected the life of 12-year-old Jason Hunter, and his subsequent actions define the future course of galactic civilization, affecting hundreds of worlds and trillions of people.

When I set out to write the trilogy, I was of course aware of the many books that claim ancient aliens visited Earth. I’m not sure I bought it, but it was a fun concept to explore in fiction. Since them, however, I have read some of these books, and I’m beginning to wonder if maybe there isn’t some truth to the idea. I’m beginning to wonder, in fact, if there isn’t as much truth as there is fiction in my trilogy!

Now, before you think I’ve gone off my rocker, let me first say that much of what is written in the aforementioned books is horse hockey. That is, the writers almost invariably take a few tantalizing facts and use them to launch into absurd flights of fancy. One book made the claim that the “starmen” were wise and benevolent, that we were a carefully watched colony, and that soon they would return and peace and beauty would reign over the Earth, or some other such nonsense. Even if aliens did visit Earth in the past, there is no reason to assume that they were any more selfless and benevolent than the Spanish Conquistadors. Why should they have been? The people here must have seemed to them as primitive as subsistence hunters in the Amazon jungle seem to us. They would have been as likely to enslave early humans as raise them up.

As for the notion that these aliens will return, well, that sounds just like the South Pacific cargo cults, or, frankly, any religion that insists its god or prophet or whatever will return someday soon (always soon!) to save us. These aliens, if they existed, might well be extinct by now. In fact, I’d lay heavy odds that they are. We’re talking thousands of years! If Earth history is any guide, no civilization lives for more than a few hundred years, tops. Odds are pretty much even that our “modern” civilization won’t survive for more than another century or two, based on how we are trashing our planet and how we are ever so eager to kill each other.

Still, there seems to be some pretty good evidence that human-like aliens did visit Earth millennia ago, and that their presence dramatically affected the development of human civilization. For all we know, there could be a vast galactic civilization composed of hundreds of races, just like in my trilogy, and we are no more aware of it than small Amazonian tribes deep in the jungle are aware of Western Civilization. Nor would those galactic races be any more aware of us than we are of those hidden Amazonian tribes.

It’s a tantalizing thought. In my next post, I’ll talk about some of the evidence that makes me think this is possible. And I’ll talk about why I think it’s premature to insist that space travel between star systems is impossible.


Is the Universe Conscious?

I am certainly not the first to pose this question. Philosophers and physicists have been asking it, and often answering in the affirmative, for quite some time now. In fact, here are three quotes from physicists that broach the subject:

“Physicists are being forced to admit that the universe is a “mental” construction. Pioneering physicist Sir James Jeans wrote: “The stream of knowledge is heading toward a non-mechanical reality; the universe begins to look more like a great thought than like a great machine. Mind no longer appears to be an accidental intruder into the realm of matter, we ought rather hail it as the creator and governor of the realm of matter. Get over it, and accept the inarguable conclusion. The universe is immaterial-mental and spiritual.”  – R.C. Henry, Professor of Physics and Astronomy at Johns Hopkins University

“As a man who has devoted his whole life to the most clear headed science, to the study of matter, I can tell you as a result of my research about atoms this much: There is no matter as such. All matter originates and exists only by virtue of a force which brings the particle of an atom to vibration and holds this most minute solar system of the atom together. We must assume behind this force the existence of a conscious and intelligent mind. This mind is the matrix of all matter.” – Max Plank

“It will remain remarkable, in whatever way our future concepts may develop, that the very study of the external world led to the scientific conclusion that the content of the consciousness is the ultimate universal reality” – Eugene Wigner

Certainly in my own philosophical meanderings I have considered the possibility that the universe itself is a conscious entity. Then I saw these rather intriguing images. Three of them are representations of neural connections in the brain, and the other three are representations (derived from the latest astrophysical research) of the large scale structure of the universe. See if you can tell which is which:

neural net1


neural net3


neural net2


Can’t tell? The last image is what brought this on. I saw it in National Geographic a few months ago and my jaw dropped. I had seen images of neural nets before, so when I opened the page and saw this image of the large scale structure of the universe, I could hardly believe it. Suddenly, the question took on a lot more relevance. I did a little more looking recently and found additional images.

Of course, it could just be coincidence. Perhaps all complex systems organize themselves this way. Still, it is intriguing, no? It is especially intriguing in the context of quantum entanglement (see here, here, and here). Theoretically, any part of the universe could communicate with any other part instantaneously, much like nerve impulses between neurons.

Which raises the question: could one of the concepts underlying the story in the Children of Hathor trilogy actually be true? Could the universe itself be composed of pure consciousness?

I’d like to believe it’s possible.

(In case you haven’t figured it out, the images alternate, with the first one showing the brain’s neural connections and the second the structure of the universe, and so on.)

Note: If you found this post interesting, you might also like an earlier post: A New Way to Look at Quantum Strangeness.

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Earth as seen from Antarctica

Some things take on a certain resonance when viewed from a windblown, polar desert. Since I arrived here at McMurdo Station a little over two weeks ago, the weather has been, shall we say, challenging. It has been an endless parade of storms, sometimes with wind in excess of 50 mph, frigid temperatures (-10F), and blowing snow. There have been times when I haven’t been able to see more than a few feet in front of me. One must be particularly vigilant for large vehicles (as in bulldozers and forklifts) and blowing debris in conditions like those.

It is here that I have just finished reading my signed copy of “Earth,” by David Brin. As I have come to expect from Mr. Brin, the novel is imaginative, thought-provoking, thrilling, and exceptionally well written. And frightening, because it invokes a future world that is all too possible. In fact, in some respects, I would say inevitable. It is perhaps because I read it in Antarctica that I have been pondering the future–both the fictional one as well as the impending real one–in rather stark terms. One cannot spend as much time as I have here in the bitter cold and desolation without coming to appreciate the generally life-friendly environment found elsewhere on our little planet. One also comes to an understanding, on a very fundamental level, that the rest of the planet could look like Antarctica–if not in frigidity, then certainly in desolation and lifelessness–if we’re not careful.

And we are not careful.

I have to wonder about us humans. Individually, we are rather smart. As a species, not so much. Oh, we are certainly clever. We invent all kinds of new technologies and modify our environment on a scale that has only happened once before in Earth’s history, when cyanobacteria changed the atmosphere from neutral to oxidative. But that took eons. We’ve made our changes in, literally, the blink of an eye. And the changes have not been good.

As a biologist, I understand the basic imperatives that motivate all living things: pass on DNA to the next generation; gather resources to facilitate this activity. The more resources, the better, in most cases. When humans take this to the extreme (which, frankly, most humans would do, given the opportunity), it’s called greed. But other animals are greedy too, when they have the option. I’ve had dogs who are never satisfied with the toys they have, they want all the toys in your hand or hidden in your pockets. Some animals, when given access to all the food they can imagine, will eat themselves sick. “More, more, and more” seems to be the default position.

I had hoped, once upon a time in my youthful optimism, that we humans would see the bigger picture and moderate that destructive influence. We certainly have the capacity to do so. We have the brain power. But we seem unable to harness that brain power to see the bigger picture and make decisions that will ensure our survival. Just the opposite, in fact.

Look at how fishermen have historically mismanaged the resources that provide their livelihoods. They will notice how a fish stock is diminishing, but instead of getting together and coming to an agreement designed to ensure the fish stock remains robust and sustainable, they try to outcompete each other to grab the last little bits, to get as much money as possible out of it before it’s gone. And then when it’s gone, they blame the seals, or the whales, or sport fishermen, or the government. The only reason some fish stocks still exist is because that government stepped in and imposed much-hated regulations. It is only because of those regulations that any fish are left at all! In some cases, the regulations came too late and certain fish stocks became economically extinct.

And now we have well-moneyed and powerful oil and coal barons who fight tooth and nail to maintain their lucrative industries, vociferously denying the negative impacts of their industries even as those negative impacts become more and more obvious. They have used their money and power to purchase politicians–purchase our republic, actually–essentially removing the only impediment to oligarchic control: a functioning, democratic government. They are not the only ones, of course. Pharmaceutical industries, agritech industries (like Monsanto), “healthcare” giants, and others have done the same, and their damage to our political and physical health should not be underestimated. But no other industry has the long-term, potentially devastating influence of the fossil fuel industry.

Sure, we are all guilty to an extent. Most of us drive cars, purchase consumer goods manufactured far away and shipped across oceans, and burn fuel to stay warm. But in many cases, we have little choice. Decisions made by industry and government limit our choices, even though we decry those limits and press for more reasonable alternatives. There are those who have sounded the alarm for decades. Thirty years ago I wrote an essay (published in the San Diego Union-Tribune) in which I offered this analogy: If you place a culture of bacteria in a petri dish and leave it to its own devices, one of two things will happen–the bacteria will multiply until all the food is used up, then they will all die, or, if they are of a particular sort, they will poison themselves with their own waste products, and they all die. Sometimes both things happen at once.

So how are humans different?

Clearly, we are not. That is glaringly obvious. Any living creature will multiply to the greatest extent possible, and it is only external factors (such as predators) that keep the population under control. We no longer have any predators, other than ourselves. But populations freed of predation will succumb to the bacteria scenario, or their populations will be brought under control by the two last-ditch methods the ecosystem has: mass starvation and density-dependent disease. It is the height of hubris to not understand, despite all our technology, that we are subject to the same controls. The current Ebola crisis is just the latest that mother nature has sent our way. It won’t be the last. (Unless, of course, the Ebola virus evolves the ability to transmit itself in the air while retaining its virulence.) And starvation, well, that’s where this conversation is now headed.

About 250 million years ago, at the end of the Permian, there took place the worst of several mass extinction events in Earth’s history. About 90% of all life, on land and in the ocean, perished. The event, which took a thousand years or so, was apparently caused by massive volcanic activity in the area now called Siberia. Volcanoes spewed huge amounts of carbon into the atmosphere, which warmed the globe by a process that any five-year-old can understand, but that which deliberately escapes the comprehension of certain rich and powerful (some would say stupid) people. Warming reached a point at the end of the Permian where pent-up methane was released from permafrost and from the deep ocean and polar seas. At that point, the feedback loop went into overdrive. The globe warmed as much as 10-12 degrees Celsius, drought ravaged the land, acidification ravaged the seas, and pretty much everything died.

That same process, which took place because of natural events over the course of thousands of years, is happening again. Only this time it is happening with a rapidity that ought to boggle anyone’s mind. It is a rapidity that is absolutely unprecedented in Earth’s history. It takes a broader perspective to see this, and humans seem generally limited in their ability to see beyond the next day, or the next quarterly report. But if you understand biology and ecology, if you understand geological processes, if you understand the grand reach of time that characterizes our planet’s history and development, it become very clear indeed. In the geological equivalent of a nanosecond, we are irrevocably altering our environment in a way that is making it incapable of supporting human life.

Brin’s book paints this kind of picture, but in that fictional account there is still hope. I am not so sanguine. I know what happens when a massive system is pushed out of balance. It seeks a new balance, and it reaches it sooner or later, but in most cases that new balance is dramatically different than the starting point.

Earth’s climate is just such a massive system, and massive systems have a lot of inertia. Like a huge freight train, it take a lot to get it moving, but once it’s in motion, it is not stopping anytime soon. We have put Earth’s climate into motion. The train has left the station. We might have been able to moderate the effects and stave off the worst of it a few decades ago, when wise and prescient people first sounded the alarm. That opportunity is lost. Researchers have already measured methane seeping out of permafrost, and people have seen methane bubbling up from the Artic ocean. Even knowing this, we continue to make the situation worse. Carbon emissions are predicted to increase by 2.3% worldwide next year and beyond.

At some point, they will begin to decrease, not because we have suddenly wised up, but because the effects of our foolishness and profligacy will finally start to be felt, in diminished economic activity, diminished food production, and diminished population. That point is coming sooner than anyone wants to believe.

People may decry what I am saying as “doomsday hysteria.” It is nothing of the sort. As a scientist and philosopher, I can look at what is scathingly obvious with a certain amount of professional objectivity. Earth has gone through this before, and she always recovers. After the devastating Permian extinction, it only took her a few million years to repopulate the globe with a whole new diversity of plant and animal life. She will do that again after we are gone.

And we will be gone far sooner than anyone wants to believe. It doesn’t take much to destroy a civilization, even an advanced technological one like ours. It has happened many times just in the brief span of human history. Take away food, and everything falls apart. I think human beings will be extinct in less than 300 years. Maybe a lot less. The victim of our own greedy, selfish stupidity, and mainly the greedy selfish stupidity of a relatively few people. All their money and power will do them no good at all when there is simply no food to buy. It is a shame that they cannot see that.

Still, it is sad, and I am profoundly disappointed. We humans held such promise. I think of the sublime miracle of consciousness, the very fact that we can be self-aware and can also look out upon the universe and be amazed and humbled and filled with wonder. I think of the miracle of love, which I have to believe goes far beyond the simple facts of procreation and hormonal influence. There is a spiritual component to love that far surpasses those biological imperatives.

I think of the sublime beauty of this planet, with its stunning diversity of life. There is certainly nothing like it in our solar system. And even though there are almost certainly other planets with life, there may be nothing quite like the Earth in the entire galaxy. What a shame to despoil such a place.

I also think of all the beauty we have created, and the noble and courageous things we have done. Art, music, individual acts of love and heroism. What other creature demonstrates these things? What other creature looks out upon a beautiful sunset with wonder and then feels compelled to paint it, or write about it, or compose a song to it?

I think of all the amazing things we could have done. We could have traveled to the stars! There is a whole universe to explore! Think of what we might have discovered! Think of what grand artistic and scientific and technological things we might have accomplished, if only we could have seen a little clearer.

Of course, people do and have done some terrible things, too, to each other and to the planet. There is no excuse for any of it. But the most terrible thing of all has been to kill our mother.

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A New Way to Look at Quantum Strangeness

So here I’m really going to go out on a limb. First, I want to make it clear that I am by no means a physicist. However, I do have a passing understanding of the most interesting (to me) major areas of that discipline: Relativity, Cosmology, Astrophysics, Particle Physics, and Quantum Mechanics. My understanding is not rooted in the arcane (and to me inchoate) mathematics involved, but rather in the overall concepts. It’s an understanding derived from reading numerous books on the subject, many of them written by physicists, including Stephen Hawking, George Gamow, Richard Feynman, and Michio Kaku.

You’ve probably never heard of the last one, but you should. His writing is clear and eloquent, and his ability to explain the densest, most arcane concepts is remarkable. I am currently reading his book, “Parallel Worlds,” which is concerned with the intersection of particle physics and cosmology. Physicists have understood for some time that you cannot begin to understand the unimaginably large without first understanding the unimaginably small. I have been interested in these subjects for as long as I can remember, certainly ever since high school. As an undergraduate, I took courses in astronomy and astrophysics, and had I not been a smidgeon more interested in marine biology (and had I been better at math), I might well have chosen physics as a career path.

So I am interested in the subjects for their own sake, because I am interested in all science, and because now, as a science fiction author, they give me great ideas that I can use in my stories. And I love ideas, especially big ideas. Here’s one I just came up with: Phased Uncertainty.

I’ll explain. In one of his chapters, Kaku was explaining one of the very strange things about the quantum world, in which particles can essentially be in two or more places at the same time. Electrons, for example, form an “electron cloud” around the nucleus of an atom. Their position at any given time is a matter of probability, but it is less a single point than a general area, and they can be in two places at once. But if you know the electron’s “position,” you cannot know its momentum, and vice versa. This is known as the Heisenberg Uncertainty Principle.

The big question is, if sub-atomic particles behave in this way, why don’t large objects? Why can’t a virus, to give Kaku’s example, be in two places at once? Richard Feynman solved the “how” of this question, but I’m not sure he solved the “why.” I mean, why don’t macro objects like viruses or tennis balls behave like sub-atomic particles? After all, they are composed of sub-atomic particles, each one of which is in a state of uncertainty where there is a small but measurable probability that it is across the room, or on the other side of the world, or on Mars for that matter. Individual particles can be as uncertain as they want, but once they are part of a larger object they seem to all agree to “be” in one particular place.

Here’s what I think. I think sub-atomic particles that are part of a collective object are in a state of phased uncertainty. Each one of them individually still has a vast set of probabilities, where they could each be in a million different places, but as part of a collective they have “agreed” to occupy a single “phase” wherein their greatest probability of existing in one spot is the same for all of them. All of their other probabilities are much smaller, but more importantly, they are out of phase. They are all over the place. One particle might have a slight probability of existing in the next room, while the particle next to it might have a corresponding probability of existing in the scientist’s shoe. In order for the entire object to suddenly be in another spot, all particles would have to “agree” collectively on a different phase. So, for example, Kaku’s virus is in one spot because all of its particles are in phase, such that each one has the greatest probability of existence at that one spot and all their other probabilities are both much smaller and out of phase. If they could somehow collectively decide to occupy a different spot, they would all have to simultaneously change to a different phase, such that their collective probability of existence is greatest somewhere else, on the other side of the petri dish, for example. Or in someone’s lung.

I don’t think this is impossible, though it is obviously highly unlikely. But what if there were some way of forcing it? What if you could alter the collective probability of an object, changing its phased uncertainty such that it is much more likely to be in an entirely different spot? This would constitute the perfect means of teleportation, though that word would be a misnomer, because you wouldn’t actually be moving a person or object (i.e., teleporting). The object or person would just suddenly “be” in another place (across the country, perhaps) because you’ve made it such that the object or person’s highest probability of existence is “there” instead of “here.”

I’ve never seen phased uncertainty mentioned anywhere, so this might be an entirely new idea. (Right! What’s the probability of that!) Any physicists out there care to comment?

In the meantime, you will see Phased Uncertainty in one of my upcoming novels.


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Time Travel

Time travel has been a staple of science fiction since, well, since H.G. Wells. Physicists have debated the real-world possibility of time travel for almost as long, ever since it has been shown that Einstein’s equations do not rule it out. However, one of the biggest objections to time travel (besides the “kill your grandfather” paradox) is that we don’t see time travelers. Even Stephen Hawking raised this objection, claiming that if time travel was possible we should be seeing tourists from the future. Since we don’t, it must be impossible.

There are two enormous logical fallacies in this line of reasoning. First, it assumes that time travelers would announce themselves as such, or at least that they would be obvious. This seems to me as a very naive assumption. Announcing that you have come from the future would be the dumbest thing you could do, in any era. In times of superstition, it would be a ticket to the stake, fire included. In modern times it would pit the hapless traveler against the avarice and ideology of those who would seek future technology to gain an advantage. Either that or the traveler (or his machine) would be hijacked for a trip to the past to change the hijacker’s current financial circumstances, or for a dozen other reasons. A time traveler who identified himself as such would be hard pressed to get out alive, whatever the year he or she popped up in.

The second fallacy assumes that humans will be around long enough to develop the technology, or at least that advanced technological civilization will be around long enough. There is no logical reason to make this assumption. In fact, based on the current state of affairs on this planet, humans could be extinct in very short order. Runaway global warming has caused the mass extinction of most of the life on Earth more than once, and it could do so again (this time thanks to us). Add to that the constant threat of nuclear terrorism and nuclear war, rampant pollution of the environment by toxic and carcinogenic chemicals, overpopulation, habitat and ecosystem destruction on a massive scale, and, of course, the ever present possibility of an asteroid or comet-induced extinction event, and it seems the likelihood of us surviving to the end of the century is not very great.

Time travel might very well be physically possible and technologically feasible, but if we don’t survive long enough to figure out how to do it, we’ll never know. And even if we do survive, no intelligent time traveler would ever reveal himself or herself as such. I think either of those is a more reasonable explanation for the lack of future tourists than to claim their absence is proof that time travel is impossible.