The question of whether or not life exists elsewhere in the universe is one that has fascinated people for decades. Countless forms of media have tackled this question, in fact the two highest grossing movies of all time, Avengers: Endgame (2019), and Avatar (2009) respectively have a strong focus on alien life. Anyhow, the realistic answer to this age-old question is most likely “yes, we just haven’t found it yet.” [1: “Top Lifetime Grosses.” Box Office Mojo, www.boxofficemojo.com/chart/top_lifetime_gross/?area=XWW.]
Now, it would be a drastic understatement to say that the universe is big. Research by NASA done in 2016 has estimated that there are around 2 Trillion galaxies scattered throughout our universe. Most of which have planets orbiting stars similar to our very own Milky Way Galaxy. Knowing this, the odds of Earth being the only planet in the universe that contains life are astronomically small. [2: Hille, Karl. “Hubble Finds 10 Times More Galaxies Than Thought.” NASA, NASA, 13 Oct. 2016, www.nasa.gov/feature/goddard/2016/hubble-reveals-observable-universe-contains-10-times-more-galaxies-than-previously-thought.]
So, assuming aliens do exist, multiple questions are still waiting for answers. Questions such as where we would be able to find them, how we could go about looking for them, and what signs we should try looking for. Luckily, all three of those questions have rather interesting answers as well.
Where Should We Search?
Given the incredibly large number of planets all throughout the universe, we would have to find a way to narrow the search dramatically. Otherwise it would be like searching for a needle in a haystack. Astronomers have determined that life most likely exists on planets that closely resemble Earth. Meaning planets that are not too cold, and also not extremely hot. If a planet were not in this habitable region of its stars orbit, water would be very hard to come by in its liquid form, believed to be necessary for life. This area between freezing cold and scorching hot is referred to by many as “The Goldilocks Zone”. Meaning the planetary conditions are just right. As observed from the Milky Way, planets like Mercury and Venus are too close to the sun for liquid water to exist. If there was any, it would all have evaporated by now. Likewise, planets from Mars to Pluto are so far away from the sun, that all water would be frozen into ice. [3: Dunbar, Brian. “Water: The Molecule of Life An Interview with Philip Ball.” NASA, NASA, www.nasa.gov/vision/universe/solarsystem/Water:_Molecule_of_Life.html.] [4: Ellerbroek, Lucas, and Andy Brown. Planet Hunters: The Search for Extraterrestrial Life. Reaktion Books Ltd, 2017, pp. 77 – 79.]
Finding planets like these may sound like an extremely difficult thing to do, but it has already been done before. In April of 2014, Astrophysicist Dr. Elisa Quintana led a team that discovered what the media referred to as an “Earth Twin”. This twin’s diameter being 10% larger than that of Earth’s, in addition to its slightly colder atmosphere, means it isn’t an exact copy of home. However, the exoplanet, or, planet outside of our Solar System still has all of the necessary requirements to sustain life similar to ours on Earth. This information is a very important leap and leads Dr. Quintana to believe that there may be even more planets like it.3 [5: Chang, Kenneth. “Scientists Find an ‘Earth Twin,’ or Perhaps a Cousin.” The New York Times, The New York Times, 17 Apr. 2014, www.nytimes.com/2014/04/18/science/space/scientists-find-an-earth-twin-or-maybe-a-cousin.html.]
How Should We Search?
NASA has developed a number of machines and methods over the past few decades dedicated to exploring our universe. While some of these telescopes, rovers, and techniques are designed to search for planets suitable for humans, the search for aliens goes hand in hand with that.
The NASA Kepler space telescope collected valuable information over the last decade that claims there are more planets throughout the universe than stars. Despite the telescope’s service no longer being required, the data it was able to collect just increases the odds of finding evidence of alien life tremendously, given the impressive number of stars we already know exist. Luckily, NASA isn’t done there. Using the spacecraft used for the Kepler launch, NASA has decided to use K2, another machine that will capture pictures of exoplanets scattered across the universe. [6: Johnson, Michele. “Kepler and K2 Missions.” NASA, NASA, 31 Mar. 2015, www.nasa.gov/mission_pages/kepler/main/index.html.] [7: , “K2 – Exoplanet Exploration: Planets Beyond Our Solar System.” NASA, NASA, 16 Nov. 2016, exoplanets.nasa.gov/k2/.]
One way to find life suggested by researchers at NASA would be by using rainbows. With the help of Sir Isaac Newton, we know that when you shine a white light through a prism, the light disperses into the six different colours of the visible light spectrum. Those colours being red, orange, yellow, green, indigo and violet. Identifying if there are any gaps present or missing in the spectrum, one can determine which elements are present in a planet’s atmosphere. The different gaps indicate different elements. For instance, one pattern could suggest the presence of oxygen or methane. Both of these elements on the same planet would be a strong sign that life at one point existed as they are both present on Earth.7 [8: “How Do We Find Life?” NASA, NASA, 2 Mar. 2020, exoplanets.nasa.gov/what-is-an-exoplanet/how-do-we-find-life/.]
What Are We Looking For?
As we can observe, there are different ranges of complexities of life on Earth. These levels of intelligence range from the bacteria living all around us, to human beings. The question of what level of intelligence we want to find is an important one in refining our search. The tiny bacteria floating in puddles is likely much easier to find than the type of beings that people most likely think of when they think of aliens. Knowing if a planet has liquid water on the surface, is a huge indication that it may at one point have been able to sustain at least the most basic form of life. Of course, this is because for all we know, water is an essential part of all life.
When thinking about highly intelligent life, a smart thing to look into would be Techno Signatures. Techno signatures are signs or signals that would let us deduce the presence of more technological life in the universe if we were able to observe them.8 We would likely have to actively be on the lookout for these signals because otherwise we could completely miss them like we did once in the past. In July of 2001, the entire Solar System experienced a burst of radio energy that lasted less than 5 milliseconds. If it weren’t for astronomer Duncan Lormier with the help of his students six years after the anomaly in November of 2007, the event likely would not have been discovered. [9: Mackintosh, Graham. “AI and the Detection of Extraterrestrial Life.” American Scientist Oct. 2018: 311. Print.]
In terms of looking for actual alien lifeforms, there is not much information to go off of besides ourselves, and how the media portrays them. Often when people think of aliens, they think of beings that look reasonably similar to humans. With the exception of movies such as The Blob (1958) or 2001: A Space Odyssey (1968), most films have extraterrestrial life similar to humans. Regardless of their physical appearance, there is a possibility that aliens are made up of completely different elements than humans.7 We may have come across this strong sign of life and never even realized it. [10: Dunbar, Brian. “Search for Life in the Universe I :: Astrobiology Magazine :: Search for Life in the Universe.” NASA, NASA, 7 Apr. 2015, www.nasa.gov/vision/universe/starsgalaxies/search_life_I.html.]
It would be pretty safe to say that Earth is not the only planet that holds life in the universe. Considering how many planets there are, and the technology that is available to us, it is only a matter of time before we get solid evidence of extraterrestrial life. Using the knowledge of the Goldilocks Zone will help scratch a large number of planets off of the list. Chances are if the planet has water in its liquid state, then the planet is in the zone. After that, the next step would be to find the elements that are present on each planet and compare them to our own. Finally looking for Techno Signatures will likely narrow the search down from there. There is no telling how long it will take, but if all of these methods of searching pan out the way we hope, there is a very high chance that we will find alien life if it does actually exist.