The Distance Problem
The difficulties with alien contact
When it comes to space travel, there are many scientific hurdles that need to be overcome. Two of the biggest hurdles are that space is absolutely enormous and there is a universal speed limit. Because of these two factors, connecting two remote points in space will always be physically challenging, not just for us, but for any extra-terrestrial intelligence* that may exist as well.
[*] For the purposes of this article, intelligence is defined as life which has the capability of communication across vast distances, which requires the development and use of communications technology, or the ability to send and receive signals.
We know that any form of life in general is going to require some kind of energy. While rogue planets flung from their star system may still contain energy from their formation that could harbor life, it’s most likely that the energy which extra-terrestrial intelligence would use to evolve and thrive would come from proximity to a star. Hence, it’s a safe bet to guess that any form of extra-terrestrial intelligence that could visit us is going to be living around some sort of star, whether it evolved on a planet, a moon, or an asteroid. If there was any chance of travel between two star systems it seems like traveling between the two closest systems would be the best bet in terms of resources and time, but how far would that journey be?
Our closest neighboring star is a part of the Alpha Centauri system which contains three stars, Proxima Centauri, Alpha Centauri A, and Alpha Centauri B. Of the three, Proxima Centauri is the closest to us. Proxima Centauri gets its name from Latin roots, with Proxima translating to “next,” and Centauri coming from the system of stars it’s located in. Therefore, Proxima Centauri can be translated as the “next (star) in Alpha Centauri,” or more simply, the closest star to Earth.
Proxima Centauri is located 40,208,000,000,000km (forty trillion two hundred eight billion kilometers) away from us. To put that number into perspective, it would take you more than 1,274,987 (one million two hundred seventy-four thousand nine hundred eighty-seven) years to reach it if you counted one number per second.
The main issue with traversing large distances, such as between Earth and Proxima Centauri, is that nothing can travel faster than light, which is capped at 299,792,458m/s (two hundred ninety-nine million seven hundred ninety-two thousand four hundred fifty-eight meters per second) in a vacuum. Oh, and the closer you get to light speed, the more energy you require to increase your speed further, with the energy requirement trending toward infinity as you approach light speed. Thus, nothing with mass can even reach the speed of light. It would take light, the fastest thing in the universe, roughly 4.25 years to reach Proxima Centauri. In comparison, the fastest craft we’ve ever made, the Parker Solar Probe, is flying through space at around 192,227.2m/s, or less than 1% the speed of light. It would take the Parker Solar Probe more than 6,600 years to travel the same distance.
Any extra-terrestrial intelligence living around Proxima Centauri that wanted to reach us would either need lifespans drastically longer than ours, would need to send out multi-generational voyages, or would need to find a way to travel much faster than we’ve currently figured out how to do.
Another thing to think about is whether extra-terrestrial intelligence would even know that we existed as intelligent beings.
Because light takes time to travel, when you look at anything you’re technically seeing it not as it is now, but as it was in the past. When you look at your computer or phone screen to read these words, it takes time for light to go from the screen to your eyes, and then it takes time for your brain to process the information from your eyeballs. Technically, you’re seeing these words as they were ever so slightly in the past. The further the distance between you and the object you’re looking at, the further light has to travel, and therefore the further in the past you’re seeing it.
For example, it takes roughly eight minutes and twenty seconds for light from the Sun to reach Earth. That means if the Sun turned off like a light switch at this exact moment, we’d have no clue that it happened for about eight minutes before everything went dark. If it were then flicked back on, the first photons emitted from it wouldn’t reach us for another eight minutes.
Because of light’s travel time, photons bouncing off of Earth from 4.25 years ago would just now be reaching observers around Proxima Centauri. That’s not too long, so perhaps if there were intelligent extra-terrestrials around Proxima Centauri that were monitoring Earth, they would see us as we were just a few years ago. They would definitely figure out that we were intelligent beings by the signals that we have sent out. But, Proxima Centauri is just the closest star, and only one of an estimated 100–400 billion stars within the Milky Way galaxy. It’s likely that any intelligent life that has evolved outside Earth may be much further away from us than Proxima Centauri, and the further away from us they were the further in the past they would see us.
If they were looking at Earth from 1,000 light years away they would see us as we were 1,000 years ago. Assuming they could peer down with telescopes that allowed them to see us walking around on the surface, they would know that we had invented technologies like the wheel, windmills, and gunpowder. However, a telescope of this resolution is not physically possible, so directly viewing life on Earth would be out of the question from that distance. If they were searching for signals we have sent out, there would be none for them to detect since we didn’t even identify radio waves until the 1800s.
Detecting biosignatures in our atmosphere might tip them off to the idea that life exists on Earth (this is one method we’re currently using to detect possible life on planets around other stars), however, biosignatures are not smoking guns and they don’t necessarily say anything about the intelligence of the life that created them. At most, they may warrant sending a probe for further study since it’s unlikely they would spend the resources to send living beings on such a long and tedious journey based on a hunch. If they have sent probes, we have no scientifically-relevant evidence of such probes visiting us. Extra-terrestrials acting on biosignatures in Earth’s atmosphere also depends on being close enough for their technology to accurately detect them.
The main effect we, as intelligent humans, have had on our atmosphere is the introduction of large amounts of carbon dioxide (CO2). This increased in intensity very rapidly around 200-ish years ago when we began industrialization. Anyone trying to detect biosignatures from more than 200 light years away may see signs of life, but not necessarily intelligent life capable of modifying their atmosphere as much as we currently are. Anyone more than about 3.7 billion light years away would be incapable of detecting any biosignatures at all because that is the age we believe the oldest lifeforms on Earth to be.
Worm holes are often cited as a way to shortcut the distance between two points in space. It’s possible in theory, but we currently don’t know of any methods for creating and/or utilizing worm holes in a meaningful way for traveling long distances in shorter amounts of time. At this point in time, we haven’t discovered any, only theorized of their existence, and theorized wormholes come with a whole range of dangers. One of the main dangers is very short stability times before collapse. There are also questions to be brought up like “how do you know where the other side of the wormhole leads to before entering it?”
So, have intelligent extra-terrestrial beings visited Earth? Knowing that they would face the same challenges we do in traversing long distances casts doubt. Further doubt is cast by the lack of recorded evidence.
Most people in developed nations carry around devices in their pockets at all times that allow them to record high-quality picture and videos. As such, we would expect that there would be an ever-increasing amount of high-resolution video and picture evidence of our visitors, but this is not the case. Most images claiming to include crafts controlled by extra-terrestrials are grainy or blurry due to the limitations of past technology. Other images and videos taken more recently have been proven to be fakes, using photo and video editing software. Intentionally fake videos of extra-terrestrial crafts has even become its own genre of content creation.
One could argue that we have been visited in the past, but are no longer being visited due to one reason or another. This idea lacks concrete supporting evidence from a scientific standpoint. All we have to go off of is eye-witness testimonies and word of mouth, which do not hold up to scientific scrutiny.
Human memories are notoriously unreliable, and have led to many cases of wrongful conviction. In some cases, witnesses were 100% convinced that they saw something that was later proven to be false and have accidentally ruined the lives of innocent people without ill-intent. This is just one example of how the human brain can trick itself into believing something that never happened. Of course, we also have to acknowledge that there are many that will make extraordinary claims purely for the sake of attention, having no evidence to back up said claims. Therefore, the word of those that have claimed to have been abducted by or seen extra-terrestrials can be seen only as interesting stories, but cannot be put forth as scientific evidence without more to back up their claim.
One common argument to the ideas presented here is that intelligent extra-terrestrials will be more advanced than we are and will have the technology to bridge the gap. While we surely don’t know everything about the laws of physics, one thing that we do know very well is that they seem to apply everywhere in the universe. This means that the issues we face in locating and getting to other places in space will also be shared by any other intelligent life out there. Not only would they have to evolve to the point of intelligence, but they would also have to overcome the technological hurdles that we are currently facing when it comes to traveling long distances. They may figure out how to travel faster than we can, but our current understanding of physics tells us that faster than light travel probably won’t ever be possible and we’ve seen no proof of the existence of wormholes. Even extra-terrestrials will have to follow the universal speed limit, setting limitations on who would have the ability to contact us and how/when they would do it.
It’s important to keep in mind that Earth has existed for a fairly short period, cosmologically speaking. With the universe boasting an age of roughly 13.7 billion years and our planet being around 4.5 billion years old, Earth has only existed for roughly 33% of the time the universe has been in existence. 67% of the time the universe has existed after the Big Bang, it did so without Earth’s presence. It’s possible that life could have existed on other planets and went extinct before Earth was even formed. It’s also possible that life may not evolve on any other planets until after Earth is rendered uninhabitable or destroyed completely.
The problems of distance and time are just two of many possible answers to Enrico Fermi’s paradox, which asks: If there are so many chances for extra-terrestrials to exist, where are they? Why haven’t we found them yet?
Philosophically, the burden of proof states that it is the responsibility of the one making a claim to provide sufficient evidence, not everyone else’s responsibility to prove the claim wrong. Until sufficient evidence is put forward, evidence that can be irrefutably shown to be true and isn’t based on personal experience, we have to assume that we have not been visited by extra-terrestrials. It’s going to take a lot to prove to scientists that extra-terrestrials have made their way to Earth or that they exist at all. There will need to be multiple independent studies that each come to the exact same conclusions, leaving no other alternatives, and will most likely require some sort of physical evidence. We just don’t have that evidence yet.
This article is dedicated to David Andrew Taylor.
