Thursday, January 26, 2006

The Very Model of a Singularitarian

If you've read this blog before, you know I like to go off on speculation regarding an eventual Singularity (where technical and trans-humanist trends accelerate asymptotically, eventually changing so fast that an event horizon is created and the very nature of our existence changes in a way that we cannot imagine).

Well, Cory Doctorow on his blog today highlighted a new tune, "I am the very model of a Singularitarian" (to the tune of "I am the very model of a Modern Major General"). It's great - give it a listen!
I am the very model of a Singularitarian
I'm combination Transhuman, Immortalist, Extropian,
Aggressively I'm changing all my body's biochemistry
Because my body's heritage is obsolete genetically,
Replacing all the cells each month it's here just temporarily
The pattern of my brain and body's where there's continuity,...

Now Where Did I Put That Pill?

Memory is a tricky thing. I walk into a room and can't remember why I went there. Alzheimer's? Dementia? Or just distracted?

Recent research is making headway in understanding some of the mechanisms involved.

Here are some basics. In order to store long term memories, they must go through a period of consolidation. This is the period in which the short term memories are encoded for long term storage. In order to retain long term memories over time, we must periodically retrieve them, at which point they go through a period of reconsolidation.

Basically, this means that whenever you remember something, your brain must go through a process of storing it again in order to be able to remember it again. This is reconsolidation. However, whenever you store the memory again, it is possible for it to be associated with other inputs that weren't there the last time the memory was stored.

It is this reconsolidation process which allows memories to change over time. Sometimes, events and sensory inputs that are occuring at the time you remember and reconsolidate the memory get intermixed with the restored memory. Also, the brain tends to fill in missing information - in fact, this is one of the primary mechanisms going on all over the brain, all the time. When you recall an event, you may fill in gaps in the memory with something close to what happened, or what you think happened. These fillers can be heavily influenced by current events and triggers for the memory recall, and therefore the memory itself can change over time, sometimes morphing quite a bit in the process.

There have been advances in neuroscience which allow both the initial consolidation process and the reconsolidation process to be interfered with, either enhancing or disrupting the process. Most of the research has been done around fear based memories (in relation to PSTD), but other studies have indicated that the same mechanisms apply to other sorts of long term memories as well.

Someday in the not too distant future, there will be pills available to support mediation of all four of these states (enhancing or disrupting either the initial memory consolidation or the later reconsolidation upon recall). Applications are multiple.

Studying for your bar exam? Enhance the initial memory consolidation during the semester so that you can recall the material easily. (Although don't overdo it - unless you'd like the memories of your textbooks to overwhelm the memories of your childhood, your first girlfriend, the first time you, well, you know...)

Got a memory you'd like to lose? Take the reconsolidation inhibiters while recalling the memory - eventually, the memory will fade. (This latter will be particularly useful in PTSD patients, where every time the vivid, violent memories of the trauma consume their attention, then can lessen the future impact by interfering with the reconsolidation of the memory).

We're not quite at the level of Eternal Sunshine of the Spotless Mind yet, but we're getting there. What will this say about how we view continuity of self? What is it that makes someone who they are but their memories?

Wednesday, January 25, 2006

The Logic of Empire

An interesting article that was recommended to me from a friend provides interesting rational for why we went to war in Iraq. It also ties in to some of the best reasons I've heard yet as to why we've supported Saudi Arabia for so long - a country at once both one of the world's most ruthless dictatorships and also the primary source for Wahhabi Muslims (one of the most ultra-conservative, anti-pluralistic sects of Islam whose major goal is to convert or kill all non-Wahhabists, be they Sunni, Shia, or non-Muslim).

Fascinating reading. I really recommend you read it through when you get a chance, then come back to read the rest of this post.

I don't buy into some of the tenets of this article, but there are a few that resonate. It makes an economic argument that goes back to the time tested fundamentals of "follow the money," which is about the truest maxim there is for finding root causes for puzzling human behavior. It presents the cost versus return to the U.S. for its recent military actions in a much more convincing way than I've seen published before. It also helps me understand the possible motivation of Dick Cheney in so aggressively pushing this course of action, and it explains why Iran is starting to rise to the surface as the next major "rogue power," while North Korea remains on the side burner, the return to totalitarianism in the former USSR is brushed aside, and China is our best pal.

Is the U.S. and empire? I suppose that depends on your definition. Certainly the U.S. uses economic bullying and blackmail to get other countries to act in line with the administration's desires. (And if that doesn't work, the use of force has been known to be tried on occasion). But rather than use the term empire, I think a better analogy is a corporation.

I think a capitalist sovereign state acts much in the same way as a capitalist corporation, whose sole purpose is to maximize the return to shareholders. Being a shareholder in the U.S., I'm not necessarily opposed to this sort of action. I have to admit, I like having a standard of living that allows me to sit back in my Herman Miller chair pontificating via blog to an empty hall on my hot shit laptop. (It's good to be the king...)

But as with corporations, some behaviors lead to long term customer relationships, and some lead to dissolution when the customers go elsewhere. The corporation in its most extreme form, if viewed as an individual, would be diagnosed as psychopathic.

It probably wouldn't hurt to do a little dolphin friendly tuna fishing every now and then, even if just to keep the world's consumers from taking their business elsewhere.

Tuesday, January 24, 2006

Whose Life Is It, Anyway?

In 1997, the Supreme Court ruled that people have no constitutional right to die. I found this interesting, in that for the longest time it was my understanding that everybody died eventually.

I wondered - did this mean that all I needed to do was get a court injunction against dying, and I could live forever? If I did die, would I be committing an unconstitutional act? Would this be in fact High Treason, for which the penalty is Death?

My head started to hurt at this point, and I put it aside in my "Stupid Lawyer Tricks" basket (along with the time they legislated that pi = 3, made it illegal for frogs to croak after 11 PM, and other "that's why they're called the laws of physics, right?" items).

But I was forced to reexamine my assumptions when the Supreme Court this week upheld an Oregon law supporting physician-assisted suicide. I suppose to be accurate, I shouldn't say they upheld the law itself - they just found that Ashcroft couldn't go after physicians using existing federal drug law. (Huh. Ashcroft exceeding his bounds - imagine that...). Ironically enough, it was a "states rights" decision, which the Republicans have been lobbying for for years.

Scalia, always out there passing in the right lane, but usually with tight logical arguments, stated "if the term 'legitimate medical purpose' has any meaning, it surely excludes the prescription of drugs to produce death." I guess next death penalty case that uses lethal injection will really back him up against a wall.

Bush's PR spokespuppet said "The president remains fully committed to building a culture of life, a culture of life that is built on valuing life at all stages." Unless you live in a country we don't like. Or break one of many death penalty laws. Or try to get married in the wrong place at the wrong time.'s legal to kill others, including women and children. It's illegal to kill myself, regardless of quality of life and the inalienable right to the "pursuit of happiness". (Even more odd, since most religions believe that their "lives" get so much better after they're dead). And except in Oregon, it's illegal to ask anyone to help you end your life. (I assume this is to support the gun lobby's goal to sell more handguns for the use of blowing your brains out).

I clearly just don't get this Culture of Life thing.

(But hey - on my deathbed, I will achieve total consciousness, so I've got that going for me, which is nice...)

Monday, January 23, 2006

A Memory A Day

That's become a key part of my philosophy.

You're going to get so many days on this earth. Whatever you believe happens after you die, the only things you're going to take with you are your memories.

When a day is gone, it's gone -there's no getting it back.

So if that day goes by without a lasting memory, it was wasted. Pointless. You might as well have just lopped it off your lifetime and never lived it.

Lasting memories are formed when you meet someone new and interesting; when you do something new and interesting; when you do something you've done before, but better than you have ever done it before; when you create something original or beautiful.

(Sure, lasting memories are also formed when something shocking, terrible, or life changing happens to you. These form your character, and bound the quality of memories you can make later in life. Without the tough times, how would we appreciate the happy ones? Without the bad people, how would we recognize the good? Without pain, why would we ever seek to alleviate it in ourselves and others? These "bad" memories are what drive us to seek out and create the good memories.)

What memory did you make today?

Divine Inspiration For Sale

According to the London Times, the Pope has announced that hencforth, and retroactively, words issued by the Pope will be copyrighted works, subject to royalties paid to the Vatican for reprints. (Thanks, Boing Boing).

It seems The Holy Catholic Church is reverting back to practices made standard during medieval times, where the clergy would regularly require payment for blessings, trinkets, idols, and indulgences.

Now, if you want to hear the "good word", you're gonna have to pay for it.

As the prostitutes say, "Hey, a gals gotta work!"

Thursday, January 19, 2006

Staying the Course

Bin Laden released a tape today that essentially said Al Qaeda will continue its attempts to attack the United States, unless the U.S. pulled out of Iraq and Afghanistan, as well as "... give an apology to all the widows and orphans and those who were tortured. Then ... announce that American interference in the nations of the world has ended."

Of course, the Bush Administration promptly stated "we do not negotiate with terrorists" (unless it suits us, like with Quaddafi or Kim Jong Il), and that we would be staying in Iraq and Afghanistan indefinitely.

Now, if you were Bin Laden, what would you be trying to accomplish with this tape? We know he's not stupid - he's evaded capture from the largest manhunt in history for over 4 years now. He knows he can't speak for all Islamic terrorists, who operate in multiple isolated cells (al-Qaeda is basically a franchise - a brand name lent to Islamic fundamentalist terrorists around the world for the appearance of pan-Islam solidarity). His goal has always been the goals of Wahabi fundamentalism, which demands that all states and peoples who aren't Wahabi moslem (even mainstream Sunni and Shia) be converted or killed - starting in particular with war against the United States.

So what possible purpose would be served by this half-assed offer of peace?

Perhaps, knowing this administration, he knew that anything he would ask for, the U.S. administration would reflexively do the opposite.

He wants the U.S. in Iraq. He wants the U.S. in Afghanistan. Why? Because every day we're there, he is able to convince and convert more and more of the Arab world that his jihad against the U.S. is justified - the only way to get back their lands from the invader, the only way to avenge the killings of their innocents, the only way to achieve control over their own resources.

The largely secular Sunni based state that was Iraq was no friend of the United States. (Or at least, not since they invaded Kuwait - prior to then, we were great buds). But Iraq was no friend to Islamic fundamentalism either, and was in fact hostile to it (witness the war with Iran).

Bin Laden has managed to manipulate the largest, most powerful country in the world to achieve what he could never have achieved on his own - a united, extremist pan-Islamic state on the Arabian Penninsula.

(Side thought - Why do we keep doing this to ourselves? Supporting dictators and sham-democracies all over the world, from Saudi Arabia to Pakistan and Egypt, from Africa to South America, does not cause the populations of these areas to love the U.S. Most of the world sees our use of power as imperialistic and capricious, and as a result either hates or fears us. But they do love our McDonalds and Levis. Which of course engenders more hate and fear...)

Update: I just finished reading the full text of bin Laden's speech, and I'm more convinced than ever it was meant as a goad to piss off Bush and make him even more belligerent. And you have to ask yourself why.

Wednesday, January 18, 2006

No Second Chances

The universe appears to be a hostile place. There are a number of relatively frequent galactic scale events that, should they occur within hundreds or even thousands of light years away from earth, would likely cause a mass extinction event that would wipe humans from the earth. (Or, at a minimum, cause a regression in the state of our civilization back to that of early hunter-gatherer societies, since our domesticated food sources would also be devastated).

Even in our own solar system, there is some evidence for fairly recent catastrophic events that might have the same impact on our technology and agricultural levels.

And of course, there are also the local events on our little ol' earth. Most of these classic scenarios you've probably heard about - nuclear winter, biological pandemics, and other man-made disasters.

Now, some of you may take the long view, and say so what - if there are a few thousand humans left, then they will quickly (a few thousand years?) rise again.

But it doesn't appear that would be possible. Let's go ahead and say that one of these many events occurs and leaves behind a few hundred thousand humans. Let's say that they're not so widely scattered that some thousands of them couldn't get together to form a community. Let's also say that the knowledge of our current technologies survives, and is available to these folks.

The trouble is, there just won't be any natural resources left to actual construct a technological civilization again.

For a civilization which doesn't have much in the way of technology to access natural resources, those resources must be easily available using the tools at hand. This means that ores, chemicals, petroleum, and other resources must be essentially at the earth's surface. (Deep drilling, mining, and ocean based resources are all out of reach).

Let's look at this post-apocalyptic world, and see what we can find. Oil? Nope. While estimates of the world's oil reserves vary, the easy patches (like where Jed Clampett only needed to miss his shot at the possum to bring up black gold) are gone. Which not only means no easy, portable energy resource - it also means no plastics, polymers, and other materials out of which just about everything today is built.

How about other energy sources, like alcohol or steam? Well, to harness these, you need the products of an Iron Age. Uh oh. Most ready surface sources of iron ore were depleted long ago. But hey! We'll have all those old cars and building beams that we can melt and use, right?

Wrong. Iron (and steel, which is just iron combined with carbon) love oxygen - love it so much that it will combine at every opportunity, forming rust (iron oxide). The resulting rusty sludge that will seep back into the groundwater is iron oxide. It's possible to extract iron from iron oxide, but it's hard without electricity and other metals like aluminum or magnesium - and modern technologies.

Ok, then what about at least the Copper Age? Darn it - I just finished reading an article that we're already running out of copper too.

Aluminum, like iron, is fairly abundant. But to work it really requires a lot more energy than iron, usually only provided using lots of electricity. Which we don't have. Because of the lack of copper and iron to build wires and engines.

Anyway, you get the drift. We really have one chance to advance far enough technologically to get off this planet and spread our eggs out over more than one basket.

If we blow it, we won't get a second chance.

Tuesday, January 10, 2006

The Transparent Society

I'm reading more stories about the war being waged between privacy advocates and technology.

Some of these fights are the same fights that have been waged before - the controversy over the Bush administration tapping U.S. citizen's communications without a warrant is a repeat of the abuses fought in the 1970's.

But some of these fights are new. And what's interesting is the changing attitudes toward a certain acceptibility, even inevitability, of the loss of prior privacies.

The Rise of the Machines

It's true that technology continues to advance the means that can be used to gather information on individuals that previously would have been impractical or impossible, from cameras to mouse clicks. And this is increasing to the point where there may be some fundamental shifts in what is considered private.

A recent article in Wired covered various technologies in trial phases that provide lie detectors based upon the state of your brain patterns. You use different parts of your brain when thinking up a lie than you do remembering the answer to a question. Visibility into the brain itself may finally provide definitive answers to a person's veracity, just as DNA testing has provided definitive answers to paternity and presence at a scene.

(One of these technologies can even work at a distance, using infrared frequencies that penetrate the skull into the cerebral cortex layer of the brain. A subject may not even realize that an active, accurate lie detector is monitoring their every word.)

Other technologies include

  • cheap web cams that can run all the time, anywhere

  • cell phones that allow pictures and movies to be taken anytime, anywhere

  • genetic analysis of predisposition toward disease (or even predisposition toward violence and pathological behavior!).

  • database warehouses, web cookies, clickstreams allow collection of buying habits and preferences

  • RFID technology, credit cards, and loyalty cards that will allows the same level of tracking of all physical goods interaction in the "real" world

  • GPS technology that can combine with the above to track the whereabouts of anyone or anything at any time.

But there is a group who isn't worried about this increasingly monitored world.

Our Children.

The Goldfish Bowl

Kids these days are growing up with these technologies, and seem to have little to no expectation of privacy. In fact, an increasing majority of kids volutarily give up private information about themselves, their friends, and their lives using personal web sites (myspace, facebook, teenspot), podcasts, and videos posted to the web. Moblogs allow real time updates of activities and events for anyone to see.

And it makes me wonder about a future where everything is literally open to view by anyone. Is this necessarily a bad thing?

What if all activities - those of government officials, politicians, neighbors, yours - were available to peruse by anyone at any time? Privacy nightmare? Or would it be one of the most lawful, tolerant societies yet developed by man?

At first, you're probably thinking about all the things that you do that you really would be embarrassed to have other people see or know about. But guess what - all those other people have similar strange habit that they would find embarrassing.

With constant and ready availability to look at anyone doing anything at any time, in short order people may become inured to the peccadillos and foibles of others. It is certainly working this way with exposure to violence and sex in the media. Most people find blase a level of graphic violence and pornography that a generation ago would have caused granny to faint dead away.

Think about criminals, killers, and cops. No one could be above the law or beyond the law.

Think about government officials. They'd finally have one half of their dream, which is to look in and spy on anyone at any time. The other half, though, is every politicians nightmare - the truth, exposed for all to see. Deception, hypocracy, and double dealing would be readily exposed to those who cared - heck, we're already seeing some beginnings of this in the blogosphere, were bloggers fact check and expose those who cross the line.

Could this open information environment be abused? There is that possibility. The branches of our government could each declare themselves off-limits to the freedom of information (just as they already try to do today). But the environment for information freedom has a technology momentum of its own, whether we want it to or not. We could choose not to allow officials this power to escape observation. Escape from scrutiny would be difficult - gaps in coverage would be obvious, and questions about what happened in those gaps can be pursued.

Does government require secrecy in order to perform its function? (How would the military plan operations against enemies who can see what they're planning? How can spies meet with their handlers when anyone can see who they are?) Interesting discussion to have.

And it's one we should have sooner than later, because the train has left the station.

Edward Teller, whose conservative politics were slightly to the right of Attila the Hun, said this -
The best weapon of a dictatorship is secrecy; the best weapon of a democracy is openness.
Thomas Jefferson once wrote
Whenever you do a thing, though it can never be known but to yourself, ask yourself how you would act were all the world looking at you, and act accordingly.

Sunday, January 08, 2006

Mind Games

I've been taking a hiatus from working for about a month, and I've noticed that I'm not into playing computer games nearly as much as I was when I was working.

I liked a couple games in particular (Civ III/IV and Battlefield 2). When I had a ton of work to do during the week, I tried to find the time to play these in the evening. Sometimes this would involve foregoing that chore called sleeping (In case you've never played either, they both can require a fairly sizable time investment). I always thought "if I take some time off work, one of the things I can do is play these games all I want!"

Now that I'm not working, I find I'm just not that interested. I still spend some time behind the computer, but mostly reading and researching topics of interest.

I figure that the games were a mental break from thinking about work. The software business can be hard to leave behind when you go home for the evening - the mind keeps churning on the problems of the day. The games were a way of breaking out of the obsessing about work problems.

They weren't mindless games (particularly Civ), so it isn't "mindless entertainment" that my brain seeks when stressed. I suppose it is just a variation in the routine that I seek when trying to get a break.

And now that my routine is anything but, and consists mostly of things that are fun and interesting, the compulsion to break free with an intense game just isn't as strong.

I'm looking forward to a Star Trek future, where inexhaustible sources of energy and nanotechnology mean that anyone can have anything for next to nothing. Those that have something to contribute to society, still will. Those who don't, won't. But at least you won't have to deal with them behind the speaker at the fast food resturant.

Saturday, January 07, 2006

The Sim Within

I've posted before about the Universe As Simulation concept. Of those in the software industry that actually ponder such things, most subscribe to some variant of this notion. (To those with hammers, everything looks like a nail...)

In order to run a simulation the size of the universe, we would require processing power to represent approximately 1080 particles in a simulation (estimated number of particles in the universe) - let's say about 1090 bits. Should quantum computing make some headway, it wouldn't take an inconceivable number of qubits - maybe 300 to 400 - to represent this many bits in a superposed state.

Wow - only a few hundred qubits! Maybe we could actually find it in our power to simulate a universe ourselves. (Would the inhabitants of this simulated universe view us as gods?)

But wait - there's a flaw in this logic. If in fact we are able to construct qubit registers of that size that can run all these superpositions without decohering, then it would imply that the processing power is coming from somewhere outside this universe. (The easiest way to think about what is "outside" our universe is to use Everett's Many Worlds interpretation of quantum mechanics, where there is an infinite number of universes, one for every time a quantum event's probability wave "collapses").

So to really run a simulation of the universe as we really think it exists, we would need to have a very large number of separate universe simulations running at the same time, and somehow entangle the simulations all together such that quantum events could take place in all universes according to their probability distribution.

And by "a very large number", I mean a number that can break up a probability distribution fine enough to handle all the possible outcomes - so at least another 1090 simulations (each simulating 1090 particles).

Dang - so close to being supreme beings.

I was wondering, though. When we design and run a simulation, we do so for a couple of reasons. One is to attempt to model some "real world" process, so that we can better predict events yet to come. The other reason we run simulations is to find out the outcome of something that can't be known in advance.

So if the universe (or multiverse) is just a very large simulation, then who designed it? And what are they trying to find out?

Maybe we're just running in a simulation designed by ourselves many years in the future, where we're trying to simulate "the real world" to the point where we can make predictions about our future. (Good thing we have concepts like closed timelike curves to keep me out of infinite regressions - using this concept, it is possible that our future selves can build a simulation that would in fact have created their own origin).

Perhaps each universe in the multiverse is just another simulation run by beings who finally developed enough computing power to run a simulation of (at least) one universe.

Almost makes me believe in Intelligent Design.


Thursday, January 05, 2006

Mainstreaming the Media

I get news from both the web and a few "old media" sources (which includes the local newspaper, The Dallas Morning News, The Wall Street Journal, and US News and World Report).

I frequently read editorials which make a claim that goes something along the lines of "you won't see this reported in the mainstream media, but..." at which point they go on to hyperbolize about some pet peeve. (The most common occurences seem to occur in "conservative" columnists, such as Michael Barone and John Leo).

Do these guys think they're writing for some underground newspaper or something? The readership of these publications places in the top ranks of media news sources. If these pubs aren't mainstream media, then there is no such thing as mainstream media.

At best, this sort of writing is disingenuous. At worst, it is dishonest.

At either, it is certainly mainstream.

Also now mainstream is the use of "cultural elite" to refer to people who form opinions different than the conservative mainstream. I find this term in use starting in the last Bush administration in about 1992, and over the last decade it has taken firm root.

Definitions vary, but in general the cultural elite includes those who have educational levels beyond high school, who live in major metropolitan areas (typically on either coast), who have above average income, and in most cases who have some relationship to entertainment or the media.

One of John Leo's descriptions went
...more likely to live in upscale neighborhoods, have maids, own Mercedes and trade stocks, and less likely to go to church, do volunteer work or put down roots in a community... overrepresented in ZIP code areas where residents are twice as likely as other Americans to rent foreign movies, drink chablis, own an espresso maker, and read magazines such as Architectural Digest and Food & Wine.

So basically, the more educated and demonstrably successful you are, the more likely you are to be a part of the "cultural elite", and the more likely it is that your opinions are wrong. According to the now conservative mainstream media.

I did an analysis once of how the pervasiveness of strong conservative religions inversely correlates to standard of living, and I'm starting to understand some of the reasons why. Ignorance, intolerance, and hate are great foundations for a poor and miserable society.

I may not be part of the cutural elite, but I may start rooting for them as the underdogs in the culture wars.

Wednesday, January 04, 2006

Topical: Razzle Dazzle Redux

Cheney has gone on the offensive (isn't he usually?) to promote the use of wiretaps to intercept terrorist communications.

The trouble is, the true controversy isn't about how wiretaps help fight terrorism. It's about the rule of law, due process, and balance of powers.

Ever since the NY Times broke the story about the presidential Executive Order authorizing the NSA to tap all overseas communications between individuals in the U.S. with those outside the U.S., the administration has been justifying the use of this program to prevent and defend against terrorists.

And I agree with them. About the usefullness of this program to help in the defense of the United States. And so does the majority of those polled. Wiretaps, and the sharing of information between agencies, are very useful moves in advancing the defense of our country.

But the real issue, continuously left unaddressed by the administration, is why is the administration so afraid of getting warrants first for these wiretaps? What is their concern about oversight by the FISA court that was established the last time the executive branch exceeded its authority?

From what I can tell, the FISA court has rarely (ever?) denied an administration request for a wiretap warrant for intelligence. All the administration ever needed to was to present some smidgeon of cause for why an individual was suspect (and "making late night calls to Osama Bin Laden" was definitely enough justification). But there must be something that the administration is doing (or thought it might do) to want to bypass even this rubber stamp of due process.

Paranoid b.s. on my part? Perhaps. But then why not address the warrant issue head on? Why try to obfuscate the debate with more nationalist demagoguery about the need to fight terrorists with "terrorists bad, we fight terrorists, so we good" pedantry?

If "freedom's just another word for nothin' left to lose", then I guess we seem to be getting more free every day.

Update: Some very good fact checking work and consolidation has been done here.

The Lack of Time Travelers is Disappointing

Back in May, 2005, MIT hosted a Time Traveler convention, inviting any future time travelers to come back in time to attend their convention.

No one showed up.

Or at least, no verified time travelers showed up. Although there were plenty of attendees, none claimed to be an honored guest.

It wasn't until I had too much time on my hands this last week to be alone with my thoughts that it occurred to me that this is disappointing.

The question "If time travel to the past were possible, then where are the time travellers?" is a variation on the Fermi Paradox (If there exist technically advanced alien civilizations, then why haven't we met them?).

Categories of explanatory hypotheses for the Time Traveler paradox are:

  • a) Time travel to the past isn't possible

  • b) Time travel to the past is possible, but

    • b1) no evidence exists because the time travelers are exceptionally good at keeping a secret

    • b2) once one person goes into the past, the timeline is altered

    • b3) the travel can take place only to alternate versions of our universe (multiverse theory)

    • b4) humans never reach the point where they invent this technology

a) Time travel to the past isn't possible. It's tough to prove a negative, so we should keep attempting to "invent" time travel to prove this idea wrong. But this is the likeliest explanation, as you'll see when we examine all the ramifications of the (b) path. And this would be disappointing, because it would mean that there are limits to what we can accomplish, even with infinite time.

b) Time travel is possible. This would be interesting, and cool, if true. But the fact is that we haven't had anyone claim to be from the future in a verifiable way (ie, they regularly make accurate predictions as to events yet to come). And this would tend to discount the variants of this path.

b1) Time travelers are exceptionally good at keeping a secret. Please. There hasn't been a human being alive that could keep a secret that well. Even Deep Throat had to speak out from his death bed to let everyone know who he was. The trouble with just about every conspiracy theory is that in order to encompass more than a couple of people, it has to assume that every single soul in a large group of humans can keep from bragging about "I know something that you don't". Historical evidence weighs heavily on the fact that nothing stays a secret forever. Therefore, if we have had time traveler visitors in our past, the odds are that someone would have talked by now.

I'll grant you that if there have only been a couple of visitors, and only a few visits through history, it is possible that any leaks would have been disbelieved and lost. But this brings up a different problem, which is coming up with an hypothesis as to why, in however many millions of years that exists after time travel is invented in the future, only a couple of visitors ever took advantage of it, and only for a few times? I can only think of a couple decent ideas, which leads us to

b2) once one person goes into the past, the timeline is altered. If there is only one timeline for this universe, and time travel is possible, then this might explain why we haven't heard about any visitors. As I said above, one visitor's single visit could easily go unnoticed, even if they did blab. (Cassandra?) However, if such a visit alters the timeline, then it is statistically unlikely that the timeline would include the invention of time travel and the use of it by that same person. Which means that if time travel is ever invented again, it would be by somebody else, and the first traveler would be somebody else.

If the second traveler went further back in time than the first, then the timeline with the first traveler will no longer exist. so unless every subsequent time traveler only goes to a time after the first one (which eventually gets to be impossible, since you run out of timeline), then inevitably there will be time travelers going back to points in time prior to those visited by "prior" travelers. (The terminology is hard, since english isn't designed to deal with the concept of time very effectively).

So if time travel exists, and was invented and used, then eventually there is only one timeline that would settle out and be stable. This timeline is one where some single time traveler went back in time and no time travel was invented again after that time. Even if the invention of time travel "happened" multiple times, the first time history was altered to the point where time travel wasn't ever invented again, you would have this version of a timeline, "forever onward" so to speak.

So, if there is really only one timeline that can exist, then the only versions that can exist are either one where no time travel was ever invented, or one where it was only invented once and used once. I suppose this is a possibility, and would explain why we haven't heard from anyone travelers. But once again this is disappointing, because it means again that there are limitations to what we can accomplish in the future.

b2) However, say there was more that one timeline. In the many worlds theory of quantum mechanics, our entire universe is just one of an infinite number of universes. Each universe differs by the outcome of a quantum event, where there is a different universe for each of the possible outcomes.

Without doing the math, trust me that this is a lot of universes - more than we can reasonably imagine. And a side effect of the multiverse theory is that there can be universes "right next door" that represent everything the same way as this universe, except that there was a series of quantum events where you were translated from this universe to that one. (This is so because, if time travel were possible, and anyone ever did travel to the past, then there would have to be a version of the universe where this happened, and one where this didn't happen as well).

So perhaps we're just stuck in the one where this didn't happen. And even if we invent time travel in this timeline in the future, and use it to travel back to the past, then the universe we're traveling to is a different one than the one we're living in (since in this universe, no one magically appeared in the past).

But the odds are really against this, because the number of universes where time travel could be invented, and the number of times people would travel to other universes, is dramatically bigger than the instance of a single universe where this never happened. (like 1/infinity). So if the multiverse theory is true, then it is disappointing, because it means we're living in a real backwater universe, out of the mainstream of universes. And living in Podunk Universe is disappointing. (Although I suppose I could take some hope in the fact that, if we really are living in the one single one-in-infinity chance universe that has never had a time traveler visitor, we could still invent time travel in our future, and travel back into the past by visiting one of the other universes in the mainstream...)

But one-in-infinity odds are about as slight as odds get, and those are the odds that this explanation is correct. Which leaves just one other explanation...

b4) Humans never reach the point where they invent time travel technology. This could happen for any number of reasons (we go extinct before we get there; we have a catastrophe that doesn't make us extinct, but we regress too far technologically and since we've used up most of the readily accessible energy sources on this planet, we can't ever crawl back up the technology ladder again; the beings who invent and use time travel look nothing like us, so any visitor isn't one we would recognize or interact with).

Regardless of reason, it would be very disappointing if time travel really were possible, and humans never reach the point where we can invent and use it. Disappointing because most of the reasons that explain why we don't get there are not really attractive to me, as a human being.

So...having given this all of an hour's thought, it is possible that I missed some possible explanations for the lack of known time travelers in our past that are more optimistic.

If you can think of one, please post a comment - I'd love to hear I'm wrong on this one.