Are We Alone?

Are we alone in the galaxy, or might we have been visited by other civilizations?

by Brian Dunning

Filed under Aliens & UFOs, General Science

Skeptoid #272
August 23, 2011
Podcast transcript | Listen | Subscribe

Pioneer plaque
The Pioneer plaque
(Photo credit: NASA)

Radio telescopes scan the skies, and computers crunch the results looking for the patterns that might indicate an artificial signal coming from deep space. Alien hunters stand watch out in the desert, looking for lights in the sky flying over military bases. Both are looking for answers to the same question: Is our little civilization on our little blue planet alone in the galaxy; or are there others, like us, who want to meet us as much as we want to meet them?

Are there technological alien civilizations out there?

Most astrobiologists think so. The physicist Enrico Fermi, upon comparing the apparent lack of any evidence of visitation to the inevitably huge number of civilizations out there, once famously blurted out "Where is everybody?" The most famous attempt to answer this question is the Drake equation, when Frank Drake strung together seven relevant variables in 1961. Multiply them all together — the fraction of stars that have planets, the fraction of planets that develop intelligent life, the fraction of those who choose to send signals into space, and so on — and you'll get the probable number of technological civilizations out there that we might hope to meet.

The obvious problem is that our estimates on most of these variables are all over the map. At Frank Drake's SETI Institute (the Search for Extra-Terrestrial Intelligence), 130 scientists in every discipline imaginable pursue research in more fields than you could shake a stick at, all of which helps to refine our estimates on each variable. The best guesses these days run from around 1 to 10. But nobody at SETI pretends that we have a good handle on this. Frank Drake himself said the equation was useful only for "organizing our ignorance" on the question.

Do the aliens exist at the same time as us?

A factor that many people fail to consider is time. Think of the galaxy as a Christmas tree with blinking lights throughout its space. Each brief light pulse is the life of a technological civilization. While there may be many lights turned on at any one given instant, the chance of two adjacent lights being on at the same time is much lower. Even if we could look into the night sky and see a big bright indicator light for every world that has a civilization, remember that that information is hundreds, thousands, even tens of thousands of years old. If we launched a spaceship to any one of them, even if it could travel at some meaningful fraction of light speed, the chances of that civilization still existing by the time we got there are small.

Even civilizations that survive their nuclear age and manage not to kill themselves are still vulnerable to Mother Nature. Terrestrial killers like supervolcanos and pandemics, and cosmic killers like asteroids, novae and supernovae, can all destroy the hardiest populations. No civilization lives forever, and on a 14-billion year time scale, very few will happen to live side-by-side at the same time.

Could aliens get here?

The problems of interplanetary travel are well known. The distances, time, and energy requirements are all well beyond our current technology. These problems are equally difficult for the aliens. Even if we grant that their physiology may be well suited to multiple-century hibernation, the fact remains that interstellar space is a resource-starved desert and all the energy needed to decelerate must be brought with them.

We should also consider whether the visitation mission was one-way or round trip. Our Pioneer and Voyager probes are certainly only one-way. Building a vehicle intended to visit another star system and then return would be orders of magnitude more difficult. If it were intended to land, it would need to provide for re-entry for not just the lander itself, but also for an entire launch vehicle capable of taking off, breaking orbit, and returning. A far more plausible plan for a round trip vehicle would be orbital only, as this would greatly reduce the energy requirements for the return. But it also limits the science that can be done, and would not allow for direct contact.

Exotic science fiction solutions that avoid the problems of travel, like wormholes and space folds, have been studied and we do have a journeyman's understanding of them. Traversable wormholes — shortcuts from one point in space to another — have been theorized, but would require the use of exotic matter that has only been hypothesized. Folding or distorting space around you (called a warp drive in Star Trek terms) also has interesting real-life hypotheses, but the problems include absurdly immense energy requirements even to transport just a few atoms, and the self-defeating restriction that creating a warp bubble to travel 100 light years must always be preceded by preparations taking at least 100 years.

Of course, just because we haven't solved these problems doesn't mean no civilization can solve them. But while this special pleading is a philosophical possibility, it's not a practical possibility according to what we've learned so far.

This applies equally to the supposition that a civilization might have colonized its neighboring star systems, thus escaping cataclysm, and surviving and propagating indefinitely; but the problems of instellar travel and the relative scarcity of suitable planets make colonization just as unlikely as visitation.

Would aliens come in person, or would they send a robot ship?

Sending a robot ship is much more practical. It can deliver all the messages, greetings, and information that the living aliens could; it has no need to carry life support systems; and its much smaller size makes the energy requirements far more achievable.

Even if the aliens plan to travel in person, they'd probably do as we've done with Mars, Venus, the Moon, and all the other heavenly bodies we've visited: send robotic probes first. No lives are risked, and a better understanding of the environment can be learned before sending living beings.

What would the aliens do here?

The question of what aliens would do if they got here is pretty hard to answer. There's no way we can know, but we can guess based on what we'd probably do if we visited someone else. When we sent out the Pioneer and Voyager probes, we put as much information about ourselves as we could onboard: what we look like, where we are, and a golden record with some recordings of sounds on Earth. Our best guess is that visiting aliens would want us to know about them, and help us to reply.

A fringe belief here on Earth is that aliens have visited, but merely stacked some rocks into pyramids, or drew a pattern into a cornfield, then left. It seems unlikely that if we were to go to all the massive development and cost of deploying a probe to an alien civilization, that this would be the plan we'd choose. We'd want to know about them, and we'd want them to know about us. The mission most likely to be successful would be to simply land as much information about ourselves as possible. Visiting aliens would probably do the same thing; simply land information about themselves. No return, minimal risk of failure.

We would probably not expect to have the energy available for our probe to fly around, move rocks, or evade their version of fighter jets. Maybe later in our technological development we might; but our first attempts at contact were simply to send a golden record.

Would we know whether they'd been here?

This question is largely answered by whether the aliens' visit was one-way or round trip.

Let's say we detected an alien civilization, then decided to send a space probe. By the time the probe got there, a huge amount of time would have passed; and it's entirely likely that during that time, the alien civilization would have advanced enough to make our visiting probe obsolete. So it might be a pretty good gamble to not bother intending the probe to make a round trip, but rather to allow the alien civilization to respond with whatever newer technologies they'd developed in the interim.

Considering the cost (energy cost or financial cost), we could probably land dozens of one-way probes for what it would cost to develop and launch a single round-trip probe. These costs would be the same for aliens as well.

Tip Skeptoid $2/mo $5/mo $10/mo One time

Given the technological difficulties and greater energy requirements of a round trip probe, coupled with the probability that a one-way lander would be the better way to do science and invite a response, it's probable that we would know the aliens had visited us. Chances are we would have their probe on display in the Smithsonian, and would have followed the instructions on their golden record to reply.

We've never discovered an alien golden record, or a one-way alien probe, or any other evidence that we've been visited. So it appears that no aliens have yet visited us with the easiest, most probable option: a one-way unmanned robotic probe.

Could aliens skirt the problems of physical travel by visiting in some other non-physical form?

Some like to suggest that advanced aliens might astrally project themselves, or find some exotic non-corporeal way to visit. This might make interesting fiction but it bears little resemblance to what we've learned about the way the universe works.

In reality, there is a way to non-corporeally accomplish the most probable mission, to deliver information about your civilization to a neighbor. Don't spend trillions of dollars and hundreds of years to land a box of stuff; beam the information there now, at light speed, for minimal cost, via radio. Anyone intelligent enough to listen for signals has already thought about translation. There are universal and mathematical constants that can be used as reference points: the Fibonacci series, the value phi, atomic mass units, Avogadro's number, and so on.

All of which brings us back to our original answer: the least likely scenario is that we'll be visited in the flesh, and there's no evidence that's happened. What's more likely is that we'll be visited by a robotic probe, and there's no evidence that's ever happened either. The most likely scenario is that we'll hear from our interstellar neighbors on the radio, and for as long as we've been listening, we haven't heard that yet either.

And so, are we alone? I don't think so. We know these problems are really hard to solve. If any pair of civilizations out there has solved them, we weren't included in the party. That doesn't mean we won't be tomorrow, or next year, or in a hundred years. Keep an eye on the sky if you must; but if we're going to meet our neighbors, chances are it will be the radio telescopes that find them first.

Brian Dunning

© 2011 Skeptoid Media Copyright information

References & Further Reading

Gowdy, R. "SETI: Search for ExtraTerrestrial Intelligence." Astronomy: A General Education Course. Virginia Commonwealth University, 18 May 2008. Web. 10 Aug. 2011. <>

Lemarchand, G., Lomberg, J. "SETI and Aesthetics." Jon Lomberg, 19 Jun. 2005. Web. 9 Aug. 2011. <>

Matson, J. "Alien Census: Can We Estimate How Much Life Is Out There?" Scientific American. 10 Feb. 2009, Volume 301, Number 2.

Plait, P. Death from the Skies! New York: Penguin Group, 2008. 7-32, 67-101.

Press, W., Teukolsky, S., Vetterling, W., Flannery, B. Nature. Cambridge: Cambridge University Press, 1986.

Shklovskii, I., Sagan, C. Intelligent Life in the Universe. San Francisco: Holden Day, 1966.

Reference this article:
Dunning, B. "Are We Alone?" Skeptoid Podcast. Skeptoid Media, 23 Aug 2011. Web. 3 Sep 2015. <>


10 most recent comments | Show all 119 comments

direct physical contact would kill us or the aliens so probably best we don't meet

andy, glasgow
March 25, 2014 5:41pm

Aliens are the modern equivalent of god.

Belief in aliens is the belief in entities for which absolutely no evidence exists. At least the belief in god has some sort of basis in logic (the unmoved mover etc). But alien believers don't even have that. The two arguments I've heard are;

1. "There must be!"

2. "The universe is very big!"

Neither of these arguments hold any validity at all. However, when one points this out to believers of aliens they get hostile and aggressive, much like the fundamentalist religious person does when their beliefs are questioned.

Mike, Wirral/England
May 16, 2014 10:56pm

Well most people that I've spoken to in my lifetime that believed in aliens (and they were few) were not aggressive, and did not have any sense of religiosity about their beliefs.

Their experiences of contact in some way (usually observation of a saucer or some light that did not move in a "normal" manner) were quietly but firmly stated, with no requirement on my part to believe what they were saying.

My own observation of a brilliant green fireball in 1992 was an example of an object that was very much out of the ordinary, and was confirmed by at least one other person who I knew, from 20 miles away.

This article presents very reasonable assertions and facts, in my opinion, but they are still based on science as it stands today, and on what any aliens may do based on our own logic and motives.

In fact, as I've said before, any aliens that visited this planet may well have thought processes and motives that are "completely alien" to humans, so "what they may do, based on what we ourselves might do" remains pure speculation, an interesting point but not any reasonable argument for why they may not be here.

My belief is that the answer lays somewhere in the magnetic fields and disturbances that UFO's (not necessarily alien) have left, or caused by their proximity, and there is much for us to learn about possible parallel universes, where such aliens may come from.

Assuming they exist.

Critical thinking must be employed, given the thousands of unexplained sightings.

Macky, Auckland
April 1, 2015 3:31pm

I figure that anybody with the technology sufficiently sophisticated to get here is smart enough to go find nicer neighborhoods to visit.

Swampwitch7, Gainesville fl
June 23, 2015 9:10pm

I figure?

No Swampwitch.. they are after psychic energy (the stuff thats just way too hard for us too find) and "shifts in magnetic fields"..

Given that a goodly deal of "UFO" sightings are indeed flocks migratory birds flying around in the evening, the ones that are seeking magnetic disturbances are just "for the birds".

Ive seen astrologers try to pass this magnetic flubber off.. isnt it straight out of a mid 40's scifi magazine?

Nicer neighbourhood tho.. My protons are mightily insulted now!!!!!

(PS, those who want to revisit the rise of flying saucers you can usually pass a magic google over my text.. After all the Palmer and Shaver didnt have that chance when.. coughing it all up)

Mulga Gill, Sydney
June 23, 2015 10:24pm

Given that the UFOs I and others have seen were unmistakable aerial phenomena, there are several possibilities as to the origin of UFOs: 1) They are from a nearby origin, possibly from the earth itself. 2) The sightings are not from one, single origin, but are multi-original in nature; some from the environs of this planet. 3) Just as prehistoric man could hardly imagine the science of the present century, so also it is extremely hard to imagine the technological advances of of other civilizations, on or away from earth, or centuries ahead of us: it may be far beyond our science to date.

Steve Erdmann, St. Louis, Missouri 63111
June 24, 2015 10:18am

There are thousands of unexplained sightings of aerial phenomena. Doesn't prove alien presence, but should engender a true spirit of enquiry to those not engaged in the ridicule of anything outside their comfort zone.

There has been reported magnetic disturbances nearby some UFO's and they have also been tracked on radar corresponding to sightings by multiple witnesses at speeds far in excess of flocks of migratory birds, a fact still not addressed by one or maybe two scientists on Skeptoid, depending on how they feel on the day.

Macky, Auckland
June 25, 2015 1:05am

I rather subscribe to the theory of collective intelligence. That is social insects are less intelligent than non social insects that are otherwise similar. They depend on the group making the right choices. It must work after a fashion.

The shrinking brains of modern humans as compared to their paleolithic ancestors strongly suggests the same thing is occurring with us. The short fall in this is what occurred when the bureaucrats took over China and froze the society by stopping all innovation and locked everyone into a frozen class system. The same thing is clearly happening in all the western nations and with the world government movement is likely in time to become a planet wide feature.

What will you get? A highly stratified world wide society/government with the bureaucrats running everything and the vast majority locked into abject poverty completely at the mercy of government officials. Of course once it become corrupt enough it will come apart at the seems. A lot of people will die and the survivors will try to rebuild. This kind of society is unlikely to expand to the stars.

Dwight E. Howell, Lawrenceburg TN
June 27, 2015 9:09am

Flocks of migratory birds are not known to outfly fast jets, or perform high-speed right-angle turns, or suddenly fly straight up into the sky.

The closeted persons who continue to explain "most" UFO sightings in this manner have obviously never read up on UFO reports or the like, have never taken into consideration the number of unexplained sightings, or the numerous testimonies of either retired or current military personnel, commercial pilots etc, preferring to stick to their comfortable home-beliefs that anything outside the norm is explainable by commonly-known objects/birds/animals.

Should said persons ever step outside their comfort zone, and look up some data in the genuine spirit of enquiry, it should (should, that is) become apparent that there are some things flying around in our skies that nobody has successfully explained.

As I've said, doesn't prove aliens, but if another civilization from another planet was a few hundred years ahead of us in their science, or a thousand, space travel may well be routine, and they may have been visiting Earth for quite a while.

Only a possibility, one of many.

Macky, Auckland
July 26, 2015 1:54am

Serious research has been going on for years on such subjects as traversable wormholes, warp drives, laser propulsion, teleportation physics and advanced propulsion concepts/methods.

All of which are in the mainstream scientific domain, and promoted by respected and award-winning scientists.

In my opinion, it is only a matter of time before further breakthroughs occur that progress interstellar space-travel from the mathematical/theory stage to the actual physical reality.

The stuff of science fiction has often become scientific fact in the past, there is no reason to believe that the problem of travelling the vast distances between stars will not be overcome in the future.

In the course of an average lifetime of 70 years, mankind progressed from no heavier than air craft whatsoever, to walking on the Moon.

A civilization somewhere in our galaxy that has managed to survive its own power-brokers' machinations and who is even only a couple of hundred years ahead of us in their scientific progress (assuming they have proceeded along the same lines) should by now have solved the problems of space travel, and perhaps even that of time-travel.

Imagine if said civilization was not a few hundred years ahead, but a thousand ? Ten thousand ?

They could have been visiting Earth for ages, and have the technology to remain largely invisible to our senses and instruments, only being detected by radar often when their "flying" machines are sighted by credible witnesses.

Macky, Auckland
August 23, 2015 3:48pm

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