What is life?

stated clearly presents how to spot an alien according to NASA's definition of life NASA and other space agencies currently have hundreds of satellites multiple probes high-powered telescopes Rovers and even a manned space station out exploring the cosmos many of these tools are equipped with cameras and some with chemistry kits able to help us spot alien life so far the existence of alien life has not yet been confirmed but aside from little green men with laser guns as depicted in sci-fi what might aliens actually be like if we were to find a smear of strange goo on Mars for example would we even be able to tell if it were alive biologists have been asking these types of questions not about aliens but about unusual specimens found here on earth for well over a century suppose for a moment that while exploring in a cave you happen to discover two cotton white puff balls apparently growing on the side of a rock could they be alive fungus perhaps or maybe real-life tribbles to help solve these kinds of mysteries scientists have come up with various list definitions of life similar to this one here it's a series of traits that living things typically all have but that non living things normally lack these lists help us ask useful questions about puzzling specimens question number one do your mystery creatures grow well maybe two of them were found and one is larger than the other that said storms lakes crystals and fires can also grow but they don't really qualify as life now do they time to ask more questions can the puffballs reproduce so far you haven't witnessed it happen but there are two of them so again maybe that said fires can also reproduce by sending out a spark but we don't consider fires to be alive time to check a third item on our list are the mystery specimens made of cells almost all living things are except for viruses this by the way is one of several reasons that viruses are not considered alive by some biologists a thorough inspection under the microscope suggests that our specimen has no cells they might be buried inside somewhere but the puffballs themselves though they are somewhat soft appear to be made of flexible crystals rather than cells further testing shows that our specimens also seem to lack other traits from our list definition largely convinced that they are not alive you use a cup of coffee to bribe a geologist for a free consultation she informs you that what you have found are ouka night crystals your specimens are not living things while the list definition of life is not perfect we've already seen that it has trouble helping us categorize viruses for example it is fairly handy for people that study modern living creatures here on earth the list definition is not very useful however for at least two special groups of researchers EXO biologists people investigating the possibility of alien life in the cosmos and prebiotic chemists researchers looking into the idea that life on Earth may have naturally emerged from chemical reactions prebiotic meaning before life if aliens do turn out to actually look like monsters or little green men with laser guns they shouldn't be too hard to spot but most life-forms on earth are microscopic and tricky to detect what if alien life is - furthermore life-forms on earth are extremely complex this is even true for bacteria and archaea the simplest critters that qualify as life according to our list definition alien life and the first true life-forms that developed on earth may be far simpler but how much simpler without a clear and widely accepted definition of life researchers could waste a lot of time and effort debating the significance of a new discovery for example back in the 50s prebiotic chemist Sidney Fox once produced what he called protein I'd microspheres tiny orbs that act superficially like cell membranes when suspended in a solution full of other protein odes microspheres can grow and even reproduce by splitting in two because they can reproduce and because they could have easily formed on the early Earth after fox initially believed that microspheres were alive and represent what the first life-forms may have been like on our planet after years of investigation and intense debate for reasons we'll see here shortly researchers today no longer consider microspheres to be alive a similar confusion arose when the Viking probes sent to Mars in 1976 discovered strange chemical reactions initially thought to be signs of microbial life while some researchers still argue that life may have actually been found by those probes further research told us we likely just witnessed unexpected reactions caused by the strange chemistry on Mars to help unify our thinking and avoid both false positives and false negatives in our search for life in 1994 NASA put together a council to discuss the essential properties of living things the result of that meeting was the production of a single sentence a sentence now fixed in the minds of thousands of researchers and soon to be fixed in yours NASA's definition of life life they proposed is any self-sustaining chemical system capable of Darwinian evolution let me say that one more time life is a self-sustaining chemical system capable of Darwinian evolution not all scientists use this definition some feel it's a little bit too constraining but if we were to discover something native to Mars that undeniably fit this definition it would excite celebration from even the harshest of critics they defined life as a chemical system because all living things we know of and most all that we can imagine our made of diverse collections of molecules and are powered by a flowing tapestry of chemical reactions saying that life is self-sustaining means that within a specific environment living things can carry on without the supervision of say a chemist creatures may require distinct molecules and energy sources from their specific environments but as long as those are supplied life maintains itself under this definition it can be easily argued that viruses and even individual genes qualify as life forms from this perspective the cells that genes and by live inside can be thought of as their environments the cell itself of course is also a self-sustaining chemical system here we see layers of life inside of life a fascinating new way to think about biology finally to be considered alive a system must be capable of adapting through Darwinian evolution this requirement though argued against by some is extremely important because Darwinian evolution reproduction with heritable modifications acted upon by selection is the most powerful natural creative process ever to be discovered it allows organisms to accumulate adaptations over time and is a process that all life forms on Earth individual genes and viruses included have access to Darwinian evolution is what gave the eyeball its lens the bird its wings and the protozoan its flagella for Darwinian evolution to work a chemical system must be capable of reproduction within its environment offspring must be capable of some form of mutation or modification and when a modified individual reproduces its mutations must be passable to at least some of its offspring dr. Fox's microspheres may grow and reproduce but they cannot pass mutations to their offspring this means they do not have access to Darwinian evolution and because of this they will not accumulate positive mutations over time they are not expected to increase in complexity they do not qualify as living things it's important to note that NASA's definition of life is not written in stone future discoveries might force us to modify it or completely rethink it for now however many researchers find it incredibly useful as we continue searching for life in the laboratory and throughout the cosmos the definition helps unify our thinking quickly and affordably resolve debates and it guides the logic in the experiments we design I'm Jon Perry and that is life a self-sustaining chemical system capable of Darwinian evolution stated clearly this animation was funded by the Center for chemical evolution the National Science Foundation NASA and our very own viewers our viewers contribute to us on patreon.com forward slash stated clearly here you can see a list of some of their names good people right there good folks thank you special thanks to all of the scientists and philosophers that helped me write this script it really helped me dig into the science and make sure that I was teaching things correctly thank you I could not have done this without you if you enjoyed this animation make sure to subscribe to our YouTube channel like this video and share it with your friends on Facebook and Twitter and all the other places where you share stuff on the Internet so long for now stay curious you

Channel: Stated Clearly

Views: 277,361

Rating: 4.8513765 out of 5

Keywords: Alien, NASA, Life, Definition of life, orign of life, chemistry, life origin's chemistry, Jon Perry, Stated Clearly, Darwin, Evolution

Id: pbZ2MFAbGrk

Length: 9min 50sec (590 seconds)

Published: Tue Dec 05 2017

Reddit Comments

[u/AsmallDinosaur]

Hmm, would artificial intelligence qualify under the nasa definition?