Does Life Exist Elsewhere in Our Galaxy?

Artist's Concept of Nearest Exoplanet to Our Solar System Around Epsilon Eridani
Artist's Concept of Nearest Exoplanet to Our Solar System Around Epsilon Eridani. NASA, ESA, and G. Bacon (STScI)

The search for life on other worlds has consumed our imaginations for decades. If you've ever read science fiction or seen an SF movie such as Star Wars, Star Trek, Close Encounters of the Third Kind, and many others, you know that aliens and the possibility of alien life are fascinating topics. But, do they really exist out there? It's a good question, and many scientists are trying to figure out ways to determine if there is life on other worlds in our galaxy.


These days, using advanced technology, we may be on the verge of discovering where else life may exist in our Milky Way Galaxy. The more we search, however, the more we realize that the search is not just about life. It's also about finding the places that are hospitable to life in all its many forms. And, understanding the conditions in the galaxy that enable the chemicals of life to assemble together in just the right way. 

Astronomers have found more than 5,000 planets in the galaxy. On some, conditions may be right for life. However, even if we find a planet that is habitable, does it mean that life does exist there? No.

How Life is Made

A major sticking point in discussions of life elsewhere is the question of how it gets started. Scientists can "manufacture" cells in a laboratory, so how hard could it really be for life to spring up under the right conditions? The problem is that they are not actually building them from the raw materials.

They take already living cells and replicate them. Not the same thing at all.

There are a couple of facts to remember about creating life on a planet:

  1. It's NOT simple to do. Even if biologists had all the right components, and could put them together under ideal conditions, we can't make even one living cell from scratch. It may very well be possible someday, but we're not there yet.
  1. We don't really know how the first living cells formed. Sure we have some ideas, but we haven't yet replicated the process in a lab. 

So while we know about the basic chemical and electromagnetic building blocks of life, the big question of how it all came together on early Earth to form the first life forms remains unanswered. Scientists know conditions on early Earth were conducive to life: the right mix of elements was there. It was just a matter of time and mixing before the earliest one-celled animals came about.

Life on Earth — from the microbes to the humans and plants — is living proof that it is possible for life to form. So, in the vastness of the galaxy, there should exist another world with conditions for life to exist and upon that tiny orb life would have sprung up. Right?

Well, not so fast.

How Rare is Life in our Galaxy?

Attempting to estimate the number of life forms in our galaxy is a bit like guessing the number of words in a book, without being told which book. Since there is a large disparity between, for instance, Goodnight Moon and Ulysses, it is safe to say that you don't have enough information.

Equations that claim to calculate the number of ET civilizations are met with staunch criticism, and rightfully so.

One such equation is the Drake Equation. 

It's a list of variables that we can use to calculate possible scenarios for how many civilizations nmight be out there. Depending on your particular guesses for the various constants, you could get a value much much less than one (meaning that we are almost certainly alone) or you could arrive at a number in the tens of thousands of possible civilizations.

We Just Don't Know — Yet!

So, where does this leave us? With a very simple, yet unsatisfying conclusion. Could life exist elsewhere in our galaxy? Absolutely. Are we certain of it? Not even close.

Unfortunately, until we actually make contact with a people not of this world, or at least begin to fully understand how life came to exist on this tiny blue rock, that question will be answered with uncertainty and estimation.

Edited by Carolyn Collins Petersen.

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Your Citation
Millis, John P., Ph.D. "Does Life Exist Elsewhere in Our Galaxy?" ThoughtCo, Jul. 1, 2017, Millis, John P., Ph.D. (2017, July 1). Does Life Exist Elsewhere in Our Galaxy? Retrieved from Millis, John P., Ph.D. "Does Life Exist Elsewhere in Our Galaxy?" ThoughtCo. (accessed March 22, 2018).