First of all, since all headaches go away eventually, whether yours goes away or not isn’t really the relevant question. It would be better to ask how quickly the headache goes away. But even this question is not necessarily good enough, because even if aspirin doesn’t relieve a headache fully, a significant reduction in severity is still worthwhile.

In light of this, you may decide that when you next notice having a headache, you’ll make a record of how you feel every half hour for the next two hours. You’ll write things like “dull, throbbing pain of low intensity” or “sharp, searing pain over one eye”.

Unfortunately, just examining how you feel after taking aspirin a single time probably won’t be adequate, since the aspirin may be more helpful some times and less helpful other times. For example, perhaps it works on moderate headaches but not on really severe ones, so if your next headache happened to be really severe, it would look like aspirin was useless. To solve this problem and give yourself more data, you might resolve to make these records of how you’re feeling for each of the next 20 headaches you get.

There is still a problem though, because these subjective descriptions of headaches are difficult to compare to each other. It you take aspirin and your headache goes from a sharp pain over one eye to an intense ache over the entire head, have you made things better or worse? It would be difficult to aggregate the information from these varied descriptions over 20 different headaches to make a final assessment of how well aspirin is working.

Analysis would be a lot easier if you scored how unpleasant each headache was on a simple scale from 1 to 5 (1 meaning slight unpleasantness, 3, moderate unpleasantness, and 5, extreme unpleasantness). That way, you can simply look at all the scores you got just before taking aspirin and average them together. You can then compare this to the average of the scores 30 minutes after taking the aspirin and 60 minutes after taking it. That way, you can see if the amount of headache unpleasantness you feel really does drop substantially after taking aspirin.

You are interested in determining how effective aspirin is at relieving headaches, but all you’ve done so far is measure how good it is at relieving your own headaches. Perhaps you are more or less sensitive to aspirin than other people, or perhaps your headaches are more severe and harder to treat than most other people’s. To solve this problem, you enlist 20 people who are frequent headache sufferers. You get them to agree that, over the next 6 months, any time they begin to notice that they have a headache they will record how they feel on your 1 to 5 unpleasantness scale. They will then take aspirin and record how they feel again 30 and 60 minutes later.

But what if people take different doses? You might think that the aspirin isn’t working for some of them, but it’s only because they haven’t taken enough. To fix this problem, you hand them each an identical bottle of pills and tell them to take two whenever they get a headache (the maximum recommended dose). This also has the added benefit that everyone will be taking the same exact brand. That way if you find out that the aspirin really does work, other people can try to replicate your results by using the same brand that you did. On second thought, you also provide everyone with a timer that measures 30 minute intervals, to help them be more accurate about making records of their pain at almost exactly 30 and 60 minutes.

There is still a problem though. You know that headaches often become less severe within an hour or so even when you don’t take aspirin. That means that even if someone’s pain score tends to have fallen 60 minutes after taking the aspirin, you don’t really know whether it is the aspirin that caused the reduction in pain or if the reduction would have occurred regardless. To remedy this, you come up with the idea of having only half of the people take aspirin when they have a headache, though everyone will still keep a record of their headache’s progression. Then, to see how well the aspirin worked, you can compare the average 30 minute and 60 minute scores of the 10 people who took the aspirin each time with the scores of the 10 people who didn’t take any aspirin. If the aspirin group’s pain fell a lot more than the non-aspirin group, then the aspirin probably was the cause.

But is it possible that the pain levels people record could be influenced by the act of taking a pill, independent of the chemical effect of the active ingredients? For example, what if, because they expect the aspirin to work, the people in the group taking the pills are more aware of signs of improvement? In that case, the aspirin would seem to work better than it really does. Or perhaps people’s expectations of improving could even influence how much pain they experience. Fortunately, these problems are easily remedied. Instead of giving half the group no aspirin, you instead give them pills in an aspirin bottle that look just like aspirin, but which have no effect on headaches. Sugar pills are a reasonable choice, because pretty much everyone has sugar in their diet anyway, and small amounts of it (like the amount in two little pills) won’t have any noticeable effect on a person.

This raises ethical considerations, however. You got people to agree to take aspirin, not to take sugar pills. That means that beforehand you’ll need to inform everyone that they might be getting aspirin, but they also might be getting sugar pills instead. You can’t let them know which they are getting during the six months that they are recording their results, but afterwards, you can let them know which they were on. You’ll also have to get them to agree to not take any other headache medication during the experiment, and to record any medication that they do happen to take, or else it might throw off the results.

So half of your group will be taking aspirin, and the other half will get sugar pills. But who should get which? If, for example, the 10 people getting the aspirin have headaches that naturally (without treatment) last much longer than those of the 10 people that aren’t getting anything, then the aspirin may seem less effective than it really is.  Hence, you don’t want there to be any substantial difference between the two groups. A simple way to help ensure this is to assign individuals to the two groups (i.e. the aspirin group or the sugar pill group) at random. It is even better if someone else does the randomization (secretly recording which person is assigned to which type of pill). That way when you talk to the subjects about the experiment, there is no chance that you accidently tip them off  (with body language, or otherwise) to which type of pill they are getting. Furthermore, when you analyze the final results, you won’t have any temptation (subconscious or otherwise) to make the data come out a particular way (since you won’t know until you are done which subject was taking the aspirin and which was taking the sugar pill).

Unfortunately, if you carried out this experiment multiple times, you should expect to get slightly different results. After all, the people you would be able to recruit might be different and so might respond differently to the medicine. What’s more, even if you used the same people each time, the intensity of their headaches might vary from one 6 month period to the next, which could also influence how the results turn out.

But, if the results fluctuate randomly, that implies that sometimes, just by luck alone, the aspirin might seem to be effective even if it is not. Likewise, it might seem to be ineffective, even if it does work. So whatever it is that your experiment shows, how can you be sure you are really getting the right answer? Well, since chance is involved, total certainty is not possible. But a statistician could easily calculate for you the probability that you would get results (in favor of aspirin working) that are at least as strong as the ones that you got, if in fact aspirin is no more effective than the sugar pill. If this probability is large, then based on your experiment you do not have sufficient evidence to conclude that aspirin is an effective treatment for headaches. If this probability is small (say, less than 5%), then aspirin very likely is effective. In order to increase the likelihood that the results of your test are conclusive, you would need only to increase the number of participants involved.

Hence, we see that in order to answer questions with a high degree of certainty, a well thought out methodology is necessary. Most elements of good study design become obvious when we reflect logically on the ways that data may mislead us. Whenever possible, experiments should be double blind with a placebo control. They should have large sample sizes, standardized dosages, a standardized (and predetermined) method for outcome measurement, and careful statistical analysis. Without all of these in place, experiments simply cannot be trusted (for reasons that become obvious, with just a little thought).

Keep the faith, don’t lose your perseverance and always trust your gut extinct.

Paula Abdul, Performer

I always trust my gut reaction; it’s always right.

Kiana Tom, Television Host

Intuition comes very close to clairvoyance; it appears to be the extrasensory perception of reality.

Alexis Carrel, Nobel Prize Winner (Medicine)

Before making a decision about whether to trust our gut, it seems like a worthwhile endeavor to first try to understand what exactly our “gut” is. There are a number of possibilities:

1. Sometimes gut feelings can be explained by our evolved instincts that are encoded in our DNA, which exist because they helped our ancestors survive in the world as it was hundreds of thousands of years ago. For example, we are likely to feel anxious when confronted with something unfamiliar (a large unknown animal, for example), or feel fear when we hear a loud noise. These sort of reactions are very useful at times, but typically only work well in scenarios involving danger or conditions that are similar to those that our prehistoric ancestors encountered. At a birthday party where balloons are being popped, a fear of loud noises is not useful. On the other hand, when walking in a canyon, a loud noise might indicate a cascade of rocks and a fear response might save your life.

2. In many cases our intuition is associated with our immediate emotional responses to stimuli. For example, we might get a positive feeling towards someone who has a warm smile, or feel negatively towards a person who is raggedly dressed. While our emotional responses clearly are important (e.g. it’s important to feel sympathy towards a friend when they look sad, and to feel fear when encountering someone who has hurt you in the past) they can also be distorted and counter productive. For example, many people feel slighted if a friend fails to return their phone call. However, one is likely to feel better about the situation (despite his initial emotional response) if he reminds himself that there are all sorts of reasons that a friend doesn’t return calls, including being temporarily busy or absent minded. On the other hand, those who trust in their initial response of hurt and anger (which might stem, for example, from a lack of confidence or insecurity) are more likely to blow up at the friend or act coldly during the next encounter, which could damage a generally fulfilling relationship. Unfortunately, it can be tricky to differentiate between emotional responses that are useful and improve our lives, and those that are based on misperceptions and are unhelpful. Both of these types of emotional responses feel equally real when you are experiencing them, and it is often only when we carefully scrutinize them from a neutral point of view that we can tell the difference.

3. Sometimes our “intuition” is based on repeated experience that we access automatically. For example, a surgeon might get an uneasy feeling during an operation, which could be triggered automatically when she notices similarities between the current patient and difficult surgical cases she has had in the past. Another example would be a painter who suddenly has an impulse to add more thinner to the paint he is using, which could be a subconscious reaction based on years of art making experience. Generally when we repeat similar tasks enough times, their execution becomes automatic and begins to feel like an instinct. We might then say that we have developed an intuition for effectively completing the tasks. These kinds of responses can occur much faster than those controlled by conscious thought, and thus can be very efficient and useful. Of course, if the initial learning phase that leads to one’s intuitions is not of good quality (e.g. we complete the task poorly while learning), the intuition will be of poor quality as well. Sometimes intuitions of this form are experienced in emotional form as an uneasy feeling, in particular when our (possibly subconscious) expectations (based on experience, training or practice) do not match what we see. A day trader, for example, might decide to sell a stock due to an uncomfortable feeling about it. In reality, what may have happened is that the stock chart had a pattern that did not conform to his expectations. This intuition can be quite useful since those cases that don’t match our predictions can be especially difficult, require special attention, and present unknown hazards.

4. Societal conditioning can create a kind of gut reaction that operates without conscious awareness. If we are told enough times when we are young not to trust strangers, then we may feel immediately distrustful when a stranger strikes up a conversation. The trouble with responses of this kind is that they are often formed without thought or careful reflection. For example, if we grow up in an area where a lot of racism is present, we might be told that certain races are inherently dishonest, and so could have strong intuitive reactions to people of those races based on this idea. Similarly, if we are taught to believe that black cats bring bad luck, we might start feeling uneasy in a house with a black cat. Since the ideas that society conditions us with may not be true, it can be very valuable to be aware of these automatic reactions and to carefully evaluate their logical and empirical validity.

5. Our brains are capable of forming very strong associations (between perfumes and people, for instance) and this can lead to what might be interpreted as “gut feelings”. For example, if we were attacked by dogs when we were young, we may feel anxious around dogs later in life, even when we know on an intellectual level that we are safe around them. Such associations clearly have a valuable survival purpose, but on the other hand, can push us into self defeating behavior (like refusing to visit the house of a friend because she has a dog). Our brain’s natural tendency is to be “better safe than sorry”, as your ancestors were very unlikely to die from forming spurious associations (such as that dogs are generally dangerous), but were at real risk of dying if they failed to form certain real associations (such as that wolves are dangerous).

As we can see, what people call their “gut” is most likely a hodgepodge of various brain activities, which include survival instincts, emotional responses, automatic recall of learned information, societal conditioning, and associations. It is not at all obvious that these systems will lead to good decision making in general. Each has its very important uses, as well as significant domains where it will fail. A business man cannot rely on fight or flight instincts when giving an important presentation, a person with an anxiety disorder cannot expect his emotional responses to be accurate representations of reality, a doctor cannot rely on his old impulses when learning a totally new surgical technique, and no one can expect that their society will condition them only with true information. Hence, to make truly good decisions, it is essential to evaluate your intuition to make sure that it is likely to be accurate in the situation at hand. Each time our gut tells us something, we cannot know whether to trust it until we understand where that feeling originates from.

1. Do terrorist groups want to nuke the United States?

It seems that yes, there are groups that would be willing to do this. According to the Report of the Commission on the Prevention of WMD Proliferation and Terrorism, “At the moment, al Qaeda is judged to be the sole terrorist group actively intent on conducting a nuclear attack against the United States.” Of course, it is impossible to rule out the possibility that other groups are also seeking to do this. I’m going to work under the assumption that Al Qaeda and those groups tightly connected to it are the only ones that would have the interest and/or capabilities of actually plotting such an attack at this time.

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2. Where would terrorists get nuclear weapons?

Genuine nukes of great destructive power are quite difficult to build, and cost estimates for building full scale weapons (of the 25-35 kiloton variety) seem to be > $5 Billion. Furthermore, such weapons would likely take longer than a decade to build from scratch (though these numbers are a bit old, so the process may have become cheaper as technology has progressed). Hence, it seems highly likely that if terrorists intended to use such a weapon they would steal them, buy them, or get them through strategic arrangements with governments that already have them. Of course, different types of weapons with different yields would have different costs associated with them, and the amount of time that it would take for construction depends on the scale of the project (with more resources and more scientists it would likely go faster). Some people fear that there may be poorly controlled nuclear weapon materials in Russia (such as bomb-grade uranium). Others fear that nukes could be stolen from Pakistan, in part because of the country’s potential instability, and also because it is possible that Al Qaeda is conducting operations there. Iran also could be a potential source of danger, in part because it is run by a religious zealot and it is unclear how far he would be willing to take his anti-American sentiments.

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3. What sort of weapons would terrorists be likely to use?

It would be far, far easier to attack the U.S. with a dirty bomb (a conventional bomb laced with radioactive material in a manner such that the material is spread by the blast) than with a full scale nuclear weapon since dirty bombs are so much easier and cheaper to construct or acquire. Such an operation would also seem to have a much greater chance of succeeding than use of a true nuclear bomb since it does not require recruiting high level nuclear scientists, massive deal making with large nations for supplies, or a laboratory which must be kept secret for a decade or more. The supplies for the construction of dirty bombs are relatively easy to obtain, though these weapons have far less destructive capability than true nukes. There has been at least one known plot (in actuality, probably more like two or three) to detonate a dirty bomb in the United States.

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4. If terrorists did choose to attack the United States with nuclear weapons, how likely would they be to choose Manhattan as their target?

It seems quite likely that if terrorists attempted a nuclear attack on the United States, it would be carried out in either Manhattan or Washington DC. Manhattan is an obvious choice because the County of New York is the most densely populated county in the country, so damage and chaos could be maximized , and because Manhattan has enormous importance to the U.S. economy. DC is also a natural choice because of the opportunity it might provide terrorists to disrupt government operations. That being said, the United States is a huge place, and it is possible that for logistical reasons terrorists might find New York difficult. If I had to put a probability on it, I would guess that there might be a 3 in 10 chance that Manhattan would be chosen as a target.

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5. If terrorists attacked Manhattan with nukes, how bad would it be?

The worst case scenario pretty much would be the detonation of a nuclear bomb (hidden in a truck or in an ocean shipping container). One source (a report by Ira Helfland, head of emergency medicine at Cooley Dickinson Hospital) estimates that a 12.5 kiloton bomb of this nature “smuggled into the port of New York aboard a shipping container and detonated at ground level” would end up killing approximately 260,000 people (about 52,000 of them would die immediately as a consequence of the blast, 10,000 would die soon after from direct radiation exposure, and the remainder would die from nuclear fallout). The study says that that several hundred thousand more would become sick from radiation sickness. There are about 1.6 million residents in Manhattan, which balloons to about 3 million during the day from people traveling into Manhattan. If we assume that the attack occurred during the day (when population densities are highest), and that in total 600,000 either die or get very sick, and that about 2.5 million people are in Manhattan at that moment (since some commuters will have left before the moment the attack occurred, or not arrived yet), then you would have about a 25% chance of dying or becoming seriously ill.

What about the case of a dirty bomb attack? In this case, it’s most likely that fewer than 10,000 people would die or become seriously ill, leaving a probability of less than 0.5% of sickness or death.

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6. What have known terrorists plots on the united states been like?

Since 9/11 muslim extremists have concocted at least fifteen thwarted plots to carry out terrorist attack in U.S. In fact, the true number is probably quite a bit higher than this. The plots that I was able to find by conducting a few quick searches were:

-Shoe bomb in plane.

-Attempted construction of a dirty bomb.

-Blowtorches to collapse brooklyn bridge.

-Attack New York Stock Exchange and construct a dirty bomb.

-Bomb subway station Near Madison Square Garden.

-Assassinate diplomat with grenade launcher.

-Attack national guard facilities, synagogues and other places in Orange County, CA.

-Plot to blow up wyoming natural gas refinery, the transcontinental pipeline, and the NJ Standard Oil Refinery.

-Potential planned attack on the U.S. Capitol and World Bank headquarters.

-Blow up Sears Tower and FBI offices.

-Attack underground transit links connecting to New Jersey.

-Blow up ten commercial airliners.

-Attack U.S. Army base Fort Dix in New Jersey with assault rifles and grenades.

-Blow up jet fuel artery that runs through residential neighborhoods at JFK international airport.

-Attack the Empire State Building and U.S. nuclear power stations.

Note that all of these attacks have been thwarted, either by the incompetence of the perpetrators, or by effective government work. The only “successful” attacks since September 11, 2001 (that might potentially be considered terrorist attacks) that I managed to find in my quick searches were:

-An Egyptian gunman opens fire at an El Al ticket counter in Los Angeles International Airport, killing two Israelis before being killed himself.

-Joel Henry Hinrichs III detonated a bomb near the packed football stadium at the University of Oklahoma in Norman, Oklahoma killing himself in the process.

-Mohammed Reza Taheri-azar, an Iranian-born graduate of the University of North Carolina at Chapel Hill, drives an SUV onto a crowded part of campus, injuring nine.

-An Afghani Muslim hit 19 pedestrians, killing one, with his SUV in the San Francisco Bay area.

-A man attacks Fort Hood with guns, shooting 44 people.

Something to notice here is that most of these attacks on the U.S. since 9/11 have failed or were foiled, and most of the ones that haven’t failed were relatively small scale. What’s more, all of the attacks listed are much, much less complex and difficult and expensive to pull off than building/acquiring, transporting and detonating a full scale nuclear bomb.

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7. What is the (very roughly) estimated probability that a person living in Manhattan will die or become seriously injured/sick by a nuclear weapon attack within the next ten years?

This estimate will of course be very crude and inaccurate, but here goes. First lets consider the case of a full nuclear bomb attack. If such an attack occurred in the U.S. and went according to plan, there might be something like a 3 in 10 chance that it would target Manhattan. The chance of death or serious injury depends a lot on the strength of the bomb, but if we assume a large bomb of about 12.5 kilotons this might give a person in Manhattan a 1 in 4 chance of avoiding serious physical harm. What would the probability be that such a plan would be foiled by the government or botched by the perpetrators? The odds seem very good of this happening, as a great number of much simpler attacks that would involve many fewer people have failed. In fact, only about 1 in 5 of the attacks I managed to find information about succeeded, and the ones that DID succeed were some of the very simplest to organize. I would guess that the odds of the success of a full scale nuclear bomb attack are something like 1 in 100. If this seems low, keep in mind that this figure has to take into account the odds that the terrorists fail to acquire or build the bomb despite their attempts, that they run out of funding, that their facilities are discovered and raided, that their bomb is discovered during transportation, that their bomb fails to detonate, that members of their team lose their nerve, that they can’t get the bomb into the U.S., etc.

The next thing to estimate are the odds that SOME terrorist group is actually attempting to plan an attack like this. The plot would be very difficult and expensive to pull off, but on the flip side, would be massively effective at injuring the U.S. (through death, illness, property damage, and widespread panic), so the difficulty might be balanced to some degree in the terrorists minds by the potential damage caused. The enormous potential cost of this project and the expertise required may well be prohibitive though, so I’ll place the odds that Al Qaeda or a closely linked group would pursue completing this project within the next ten years rather arbitrarily at 1 in 10. Here I am assuming that only Al Qaeda terrorist group would even be willing to attempt such a project. All in all, this very crude estimate indicates that the likelihood that terrorists attempt to attack the U.S. with a full scale nuclear bomb, actually succeed in this plan, carry out this attack in Manhattan, and kill any one particular Manhattan resident (chosen at random) is about 1 in 13,300 (over a ten year estimated period). To put this in perspective, the chance that you eventually die of a car accident (rather than other potential causes of death) is about 1 in 6,800.

On the other hand, dirty bomb scenarios are far more likely to be carried out successfully, and far more likely to be attempted (in fact, they already have been) but are unlikely to actually kill or seriously harm a randomly selected person in Manhattan. We can estimate that, once again, there might be a 3 in 10 chance that such an attack (if it occurred) would occur in Manhattan, that if it did happen in Manhattan each individual would have less than a 1 in 200 chance of incurring serious harm (let’s say for the sake of argument that the most likely number is something like 1 in 400), that such an attack might be planned twice in the next 10 years, and that the chance of success for such an attack might be 1 in 10. These give us odds that a single, predetermined person in Manhattan would suffer serious physical harm from a dirty bomb at about 1 in 6,600. This number is also on the order of the chance of eventually dying from a car accident.

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8. How much should we fear nuclear terrorist attacks if we live in Manhattan?

From the simplistic analysis carried out above, the answer seems to be that Manhattan residents (who plan on staying in Manhattan for just ten more years) shouldn’t fear nuclear terrorism all that much more than a randomly selected American should fear the possibility of dying of a car accident at some point in their life. One thing that may be worth pointing out is that even if a nuclear weapon did kill us, there is some chance (dependent on the characteristics of that weapon) that it would do so fairly instantaneously, meaning that we would be dead before having much opportunity to suffer or even notice, which seems a lot less horrible than a slow death by radiation poisoning. On the flip side though, if a nuclear weapon was detonated and did not kill or injure us, the psychological effects of such a disaster could still be great, potentially causing the death and injury of those people we know, and likely inducing panic.

While nothing is known for certain and this analysis is certainly flawed in a handful of ways, the chance of a nuclear terrorist threat does not seem high enough to warrant moving out of Manhattan if you derive significant value from living there. Moreover, if you have already decided that you are going to live in Manhattan, what is the use of worrying about death from nuclear weapons at all? It isn’t as though worrying is likely to make you safer in a significant way. There are many things that have the potential to kill us each day, and we tend to simply not think about them, so why should this be different? Sure, it seems scarier in some ways than car accidents, which feel more familiar, but car accidents (and tumors and strokes) can be just as horrible as death by nuclear bombs or dirty bombs. Living in fear will almost certainly reduce your quality of life without making you substantially safer, so the best thing is probably to learn to be okay with the fact that we will never be totally safe (from nukes or cars or the huge number of other things that might hurt us), and this is just a part of life.

If thoughts about nuclear weapons are something that you find you are upsetting yourself with frequently, you might try writing down answers to the following questions:

a) If I don’t worry about hundreds of other potential sources of death, then why should I worry about this one source, especially since it is quite unlikely to occur?

b) What advantages and disadvantages are there to my worrying about nuclear bombs (especially taking into account the fact that there is nothing I can do to prevent such an attack)?

c) Since death is inevitable, and often painful and unpleasant, is dying from nukes really such an especially horrible way to go?

d) What is a more productive use of our time, worrying about nuclear bombs or researching and implementing ways to mitigate preventable sources of death? (keeping in mind that most of us could eat healthier, exercise more, wear our seat belts more scrupulously, get more regular checkups, and do many other things that would likely extend our lives).

]]> http://www.clockbackward.com/2009/11/22/will-terrorists-attack-manhattan-with-a-nuclear-bomb/feed/ 4 http://www.clockbackward.com/2009/11/17/answers-to-frequently-asked-questions-about-religion-god-and-spirituality/ http://www.clockbackward.com/2009/11/17/answers-to-frequently-asked-questions-about-religion-god-and-spirituality/#comments Tue, 17 Nov 2009 20:47:43 +0000 ClockBackward http://www.clockbackward.com/?p=455 At first glance, it may seem obvious that the bigger religions are more likely to be the one true religion, but on the other hand, no religion represents more than 50% of the population today, so clearly whatever God or Gods are out there didn't care too much about making their message easy to discover. ... Either, they want to attain the reward their religion offers (e.g. heaven), they want to avoid their religion's punishments (e.g. hell), they want to avoid social ostracization, they want to be thought of as a pious and good person, they want to feel like a good person, they enjoy following the religious rules, or they feel like they owe something to their God or gods and follow religious laws out of a sense of obligation.

The Formation of Life

The theory of evolution tells us that given the right conditions (a sufficiently powerful source of energy, the right kinds of atoms, etc.) life can form through a natural and essentially automatic process. Scientists do not understand the precise details of how this occurred on our planet (which shouldn’t come as a surprise, given that the event happened billions of years ago on a microscopic scale during a time when earth had a very different chemical composition then it does today) but they do have reasonable conjectures. What seems very likely is that prior to life there existed what we might call pre-life: simple, self-replicating molecules, the first of which was formed by a lucky collision of atoms. These replicators would occasionally make errors while copying themselves, which most of the time would be disastrous to the reproductive capabilities of their offspring (destroying the possibility of further replication), but which every so often would lead to slightly more efficient replicators. Of course, copying requires the use of chemical materials, so the replicators would be in competition with each other for molecular resources. Over time, through the processes of natural selection, those replicators that were most efficient at surviving and copying themselves in the prevailing environment would spread wider and faster than the others. Over many generations, the lineages of replicators that survived would get progressively better suited for their environment, very slowly becoming what we would recognize as life.

If this process of life generation can spontaneously begin on earth, then it can occur on any other planet, assuming that the planet has sufficiently favorable conditions for a sufficiently long period of time. In particular, since the laws of physics on earth appear to be precisely the same as those that govern the rest of the universe, and since the universe looks to be approximately the same in every direction, we should anticipate seeing other earth-like bodies distributed throughout the universe (in terms of size, position within their solar systems, chemical composition, etc), and we should expect that these planets have a probability of developing life that is similar to the chance earth had. It may be possible that life could take forms that are difficult for us even to imagine, occurring on astronomical bodies that are not very much like earth at all, but since life occurred once on a earth-like planet, earth-like planets are our best guess for where we can expect to find alien life.

It is estimated that there are far more than a trillion planets†† in the universe, providing a staggering number of opportunities for life to begin. Furthermore, the universe is more than 13 billion years old†, so there has been an enormous amount of time for life creating processes to take place. Given enough planets, it is inevitable that at least one will be sufficiently like our early earth to house life. Given enough time, it is inevitable that life will eventually form on such a planet. Hence, the spontaneous formation of life on earth indicates that life very likely exists elsewhere in the universe, though estimating the actual probabilities involved is tricky. The question of exactly how much life has existed in our universe can be reduced to a question that can be studied empirically through scientific means. Essentially, one needs to calculate how many planets (or other astronomical bodies) in our universe today are likely to have undergone long periods during which conditions were suitable for life to begin. Unfortunately however, even with the best telescopes our ability to peer through the vast expanses of space is severely limited, and our understanding of planet formation and evolution is far from complete, so this question is unlikely to be adequately answered for a long time. Ultimately though, the question of the existence of aliens is a scientific one, and therefore we should expect scientists rather than philosophers to eventually have the greatest insight into its answer.

Traveling Through the Universe

Some people believe that intelligent life is unlikely to exist outside of our planet, because if it did, we likely would have encountered it by now. This belief reflects an ignorance of the incredible size and spaciousness of the universe. To give an illuminating example, suppose that humans were interested in traveling to the star (other than the sun) that is the closest to our earth. This star is Proxima Centauri (a red dwarf, it turns out), at a distance of about 4.2 light years from earth. That means that if a space shuttle traveled to Proxima and back at the speed of light, 8.4 years would have elapsed on earth by the time they returned. In practice though, the equations of Einstein’s theory of relativity tell us that it would take an infinite amount of energy to get a massive object to move at light speed. We therefore might employ the more realistic assumption that the space shuttle traveled at about 25% of the speed of light (or, as a physicist would say, 0.25 C). This would still be an incredible scientific achievement, considering that it is about 37,000 times the speed of the fastest plane. To get a space shuttle (weighing, say, 24,000 kg like some space shuttles do today) going at this speed would require a minimum (assuming perfect efficiency in converting potential energy to kinetic energy) of about 67 million terra joules (actually, slightly more, taking into account relativistic effects), which is approximately 280 times the energy released by the most powerful nuclear weapon ever created. Of course, naively setting off 280 nuclear weapons of this kind would be far more likely to kill all life on earth than to get an object close to the size of a space shuttle traveling at the desired speed. As a matter of fact, the process would have to progress rather slowly. Since the human body is limited in the amount of acceleration it can withstand (before blood pools heavily in the legs, and worse), it would take a minimum of 15 days of accelerating to get up to this enormous velocity (unless drastic means were taken, such as keeping the astronauts submerged in fluid during acceleration). In the end, even with the stupendous speed of 25% of the speed of light, a journey to Proxima and back would take over 33 years from the point of view of someone on earth, more than a third of a human life span, and long enough to ruin all of one’s personal relationships. And let us not forget, all this would get us is a roundtrip voyage to our second closest star! The universe is an extremely spacious place, and even for an alien civilization far more advanced than ours, it would take an enormous amount of time to explore even a single galaxy, let alone the more than a hundred billion galaxies that are thought to exist. Our own milky way galaxy is thought to contain approximately one hundred billion stars, and from the point of view of someone on earth, a traveler moving at the speed of light would take approximately 26,000 years to reach earth from our galaxy’s center. In particular, this means that aliens located at our galaxy’s center could not possibly be aware of the first human radio broadcasts for many thousands of more years. Finding alien civilizations, and exploring a galaxy is long, hard work!

There is an important point to be made about the way in which Einstein’s theory of relativity relates to travel at speeds approaching that of light. Because of an effect known as time dilation, time literally moves slower for a traveler that accelerates than it does for the people (or should I say creatures?) on the traveler’s home planet. At speeds like 25% the speed of light, the effect is a rather minor one, but at 99% the speed of light or faster it is very pronounced. In a sense, this provides a space travel loophole, because an alien could theoretically travel extremely long distances at close to the speed of light without aging very much (though, the rest of the universe would continue to age normally of course, so their loved ones would probably die off before they returned from their journey). For example, while a trip from our galactic center to earth would take about 26,000 years for a traveler moving at the speed of light from the point of view of someone still on earth, from the point of view of the traveler himself the journey would feel almost instantaneous. The trouble with using this method for space travel, however, is that the closer to the speed of light one wants to travel, the more energy is required to do so (with, as we have said, an infinite amount of energy being needed to travel at light speed exactly). Hence, time dilation comes at the price of dramatically increased energy requirements. It is also probably worth mentioning that a ship traveling at these sort of speeds would be insanely difficult to navigate. There would be very little time to change course to avoid any interstellar objects, and at the speed of even only 25% the speed of light, a rather small piece of rock or ice carries an enormously destructive amount of momentum. All this being sent, with phenomenal technology, an enormously plentiful energy source, lots of time for acceleration, incredibly good navigation systems, no desire ever to return home again, and a lot of luck, aliens might be able to get from planet to planet quickly without aging very much in the process. The amount of aging they would undergo on such journeys depends on how close to the speed of light they can get without destroying themselves or using up their energy source. A hypothetical method that has been proposed for achieving speeds close to that of light is the Bussard ramjet, which involves using powerful electromagnetic fields to harvest free floating space particles during flight, and converting them to energy with a fusion powered rocket.

What about traveling at speeds beyond that of light? Unfortunately, as far as physicists can tell, no object can ever go faster than light. Of course, we can never rule out the possibility that science not yet discovered will one day allow that possibility, but the extremely well validated theory of relativity currently denies it. That being said, there are at least a couple of ways that the light speed constraint can theoretically be circumvented without actually breaking the ultimate speed limit, but they may not be of any practical use.

Quantum theory predicts the existence of “wormholes”, which are essentially open passages that connect two points in spacetime. While wormholes have as of yet never been observed directly, they may exist at an extremely small scale, popping into existence for miniscule amounts of time and bridging together very short spacetime distances. Expanding or creating large wormholes, getting them to stabilize for reasonably long periods, and controlling which parts of spacetime they connect are currently very far beyond the scope of modern science. It could easily turn out that worm holes are essentially useless from a space traveler’s perspective, no matter how advanced technology has become. Some initial calculations done by physicists of what it would take to create a useful wormhole make demands that are probably beyond the scope of ANY civilization. Some physicists have argued that large, stable wormholes could already exist strewn throughout the universe, a consequence of the inflation of the universe after the big bang. While wormholes like these could potentially be useful for interstellar travel, locating them and actually getting to them could itself be extremely difficult, and since their pathways would already be determined they would not provide much flexibility to a traveler. It is worth mentioned that these strange tunnels can cut through time as well as through space, transporting a traveler into the past while at the same time altering his position (though a wormhole could not take you back to a time prior to when it was created).

Another, totally different way that the speed constraint of relativity is sometimes circumvented is through the phenomenon known as quantum tunneling, where tiny particles jump locations approximately instantaneously. Unfortunately though, this is inherently an unpredictable process, and therefore not useful for controlled traveling. What’s more, like worm holes, this phenomenon is only known to happen at miniature scales, far smaller than even a single celled organism. In the macroscopic world of massive objects like people and spaceships, quantum tunneling is never observed.

As we have said, if aliens managed to achieve speeds nearing that of light, they would be able to explore the planets of their galaxy without aging a great deal. However, from the point of view of planet earth the process would still be extremely slow (the aliens would experience time dilation due to their enormous acceleration, causing time to run more slowly for them than usual, but we would age at our normal pace). If, for example, there were aliens at the center of our galaxy traveling at almost the speed of light directly towards earth, they might find earth in what to them is a few years, but what for us is more than 500 generations. Hence, even if aliens knew where we were located, had a desire to get to us, and didn’t care about ever returning home (after all, their own civilization might be extinct by the time they returned) we would be waiting an enormous amount of time before they got here. By the time they arrived so much time would elapsed that our planet might be destroyed, or our technology might have become as good as their own (making us a potential threat). Unless an alien civilization was lucky (or unlucky) enough to have evolved on a planet very nearby us (by which I mean, within a few dozen light years), even discovering where we are located would be highly problematic. While it is true that the radio waves that we transmit travel at the speed of light, and might potentially be detected by another civilization, these signals grow dramatically weaker as they propagate away from earth, and by the time they are a hundred light years out may be extremely hard to detect (especially when mingled with many natural interstellar sources of noise).

It is probably worth mentioning that there are some reasons to think that aliens might not travel all that much around their galaxies even after they are able achieve speeds near that of light. For one thing, humans already have the technology to destroy all life on earth, and we aren’t yet anywhere close to having ships that can quickly carry humans through interstellar space. It may well be the case that most alien civilizations that exist destroy themselves long before gaining these capabilities. If, as seems to be the case, creating massively devastating weapons is much easier than near light speed travel, civilizations might generally not last long enough to travel. On the other hand, if near light speed travel is sufficiently difficult to achieve (requiring, say hundreds of thousands of years of research by modern humans), then species might tend to be destroyed by natural disasters (such as supernova) before acquiring the technology. What is more, it is interesting to consider the role that virtual reality would likely play in an extremely technologically advanced civilization. If essentially any experience can be had virtually, the need felt to travel outside of one’s own planet (let alone, to ever leave the virtually constructed world) may become limited. Once a civilization comes to construct and accept a virtual world that accurately simulates experiences, but in which one can create or do whatever one one wishes (perhaps even invoke pleasurable feelings upon command), how much time would creatures really choose to spend in the real world?

Aliens Here On Earth?

What is a person to make of the innumerable tales of alien abductions, alien autopsies, crop circles, and spaceship sightings that have been floating around since the 1940′s? While it is impossible to examine every single one of these cases (there are far too many), upon close examination every case that I know of that was thoroughly investigated did not provide solid evidence for alien life on earth. Most of the alien abduction stories come with no corroborating evidence whatsoever (only witness testimony), and most of them occur just after (or during) sleep. Hence, it is impossible to rule out the very mundane explanations of lucid dreaming, sleep paralysis, deliberate fraud, misperception, drug use, illness, and psychosis as explanations for these alleged experiences. Once the idea of aliens became popularized back in the 1950′s alien creatures began to appear in great numbers in people’s dreams and hallucinations. As far as crop circles go, those have essentially been debunked as the work of mischievous (and creative) humans. A number of UFO sightings have turned out to be either unusual aircraft (such as air balloons), normal aircraft flying in formation, normal aircraft with unusual lighting, meteorological events, or tricks of the nighttime sky coupled with human perception errors. While many UFO sightings have gone unexplained, a lack of explanation is a far cry from proving that aliens are here on earth as there are dozens of possible explanations for a person claiming to see moving lights in the sky. In order to prove a point, professional skeptic James Randi once claimed on a radio show to have just seen a UFO. People began calling into the show, claiming also to have seen the same UFO that evenining, unaware that he had made the sighting up. Unfortunately, even photos of UFO’s do not provide good evidence as they can easily be forged (in fact, many of them are known to have been), or are ambiguous as to their interpretation. As far as alien autopsy videos go, those I have seen are obvious or known fakes (like the alleged Roswell autopsy video). Essentially, there doesn’t seem to be any strong evidence behind the alien sighting phenomenon, and it is clear that there is an enormous amount of human psychology involved. Even if aliens are on earth, the vast majority of alleged alien sightings are undoubtedly not genuine. Until actual alien technology is found (that has a function or material composition unachievable with human technology), an alien is actually detained, or video of aliens is taken that could not have been forged using computer generated imaging, it is wise to remain skeptical of stories about aliens.

An important point to keep in mind is that the fastest way that aliens have to discover that intelligent life exists on earth is to detect the radio or microwave signals that we produce. However, if the alien’s home planet is hundreds of light years away then our earliest signals would not even have reached them by now! In particular, since the invention of radio is less than 150 years old, the only possible civilizations that could have discovered that there is intelligent life on earth must be within 150 light years of us. Even worse, if aliens travel at a maximum speed of 25% of the speed of light, the only way that they could have both detected our signals and traveled to earth is if they were within 30 light years of earth when we first started broadcasting, which is a very tiny sphere compared to the size of our galaxy.

Contacting Aliens

While it is very unlikely that aliens have arrived here already, if humans continue to exist for another one hundred thousand years (admittedly a somewhat dubious prospect), it would not be terribly surprising if contact with aliens occurred at some point, most likely through electromagnetic signals rather than through direct face to face contact. Astronomers have now broadcasted messages into space, designed specifically to be detected and interpreted by technologically advanced aliens. Because of their design, these signals are more likely to be detected and properly interpreted than ordinary radio or television broadcasts. Unfortunately, contact with aliens may well be a very bad idea from the point of view of human survival. While aliens could potentially be friendly, there is reason to expect the opposite. Evolution, wherever it occurs, is a highly competitive process, requiring creatures to kill each other for resources. As essentially all creatures on earth (including humans) have many selfish and exploitative tendencies, it seems likely that aliens will as well. Under natural circumstances, creature that are too altruistic tend to be taken advantage of by more selfish individuals, and hence weeded out of the gene pool.

If humans are detected by an alien civilization in the next hundred years, the aliens will almost certainly have far superior technology to our own (by the very fact that they are able to detect us at all), and therefore could likely annihilate us with ease if they felt we might one day be a threat. With sufficiently powerful technology, for example, they could launch a weapon at us at near light speed. By the time we could even detect such an object (if indeed we would be able to detect it at all), there would be little time for us to understand it or react to prevent our destruction. The sad truth is that much of the time when groups of humans have encountered those who are much less technologically advanced than themselves (but who, nonetheless, are in control of useful resources), the weaker group has been suppressed, enslaved, or annihilated. Just look, for example, at the colonization of North America and Africa by Europeans. Unfortunately, it is not terribly unlikely that aliens would be similar to us in this regard. Even if there were only a 30% that the aliens would decide to kill us all, would that really be worth the risk? One thing to keep in mind is that if aliens do ever receive our signals and choose to respond to them in kind, the wise thing for them to do would be to obscure the origin of their messages, perhaps by reflecting them off of astronomical objects (to avoid the danger that we one day develop technologically strong enough to harm them). Hence, it is unlikely that contact with advanced aliens will actually allow us to identify their location.

Conclusion

While technologically advanced alien life is quite likely to exist elsewhere in the universe, it seems that it would be very difficult for these creatures to travel to earth, and perhaps even detect our existence in the first place. Moreover, if they did try to travel to us, it would almost certainly take an extremely long time (from our point of view) for them to make the journey. Finally, if aliens do visit us, there are reasons to think that the visit may be hostile. Unfortunately (or, perhaps quite fortunately) our only interactions with aliens in the next hundred years will almost certainly be only in our imaginations.