WEBVTT - Could Alien Life Exist? 0:00:02.040 --> 0:00:08.399 Welcome to brain Stuff from How Stuff Works, Hey, brain Stuff, 0:00:08.480 --> 0:00:11.680 Christian Sager Here. The Milky Way is thought to hold 0:00:11.760 --> 0:00:16.479 at least a hundred billion planets. About seventeen billion of 0:00:16.520 --> 0:00:19.799 those are roughly the size of Earth. And check this out. 0:00:20.160 --> 0:00:24.440 One in every six of our galaxy stars have planets 0:00:24.480 --> 0:00:28.760 revolving around them. As far as confirmed planets go, though, 0:00:29.200 --> 0:00:32.880 as of this recording, NASA has confirmed nine hundred and 0:00:32.920 --> 0:00:37.360 sixty two of those one hundred billion planets. We used 0:00:37.400 --> 0:00:39.720 to think that they were rare, but since we launched 0:00:39.760 --> 0:00:43.480 the Kepler Space Telescope, we're finding more planets every day, 0:00:43.680 --> 0:00:47.120 especially ones with water on them. And what we've also 0:00:47.240 --> 0:00:50.320 learned is that these planets don't need to be as 0:00:50.400 --> 0:00:54.320 perfect as we once thought to sustain life here at home. 0:00:54.720 --> 0:00:58.080 We've learned that life is a lot hardier and exists 0:00:58.160 --> 0:01:02.560 in some extremely hard environments. All of this adds up 0:01:02.720 --> 0:01:05.560 to a lot more evidence that we aren't alone in 0:01:05.600 --> 0:01:09.000 the galaxy. While Earth is still the only planet that's 0:01:09.040 --> 0:01:12.880 proven to support life, we're actively searching for other worlds 0:01:12.920 --> 0:01:16.120 to join us. But to do that, first, we have 0:01:16.240 --> 0:01:21.360 to define what life actually means. And not everyone agrees 0:01:21.400 --> 0:01:24.520 on this topic, but let's try this one out. Life 0:01:24.520 --> 0:01:29.480 requires an organized cellular structure that functions in a relatively 0:01:29.640 --> 0:01:35.120 unchanging state. It's capable of reproduction, growing, taking in energy 0:01:35.160 --> 0:01:39.560 from its environment, and responding to stimuli, and it can 0:01:39.600 --> 0:01:43.440 adapt to the environment it lives in. Okay, and per 0:01:43.520 --> 0:01:49.280 Darwinian evolution, we know that similar organisms produce similar organisms, 0:01:49.320 --> 0:01:54.120 so for instance, a dog reproduces another dog, not a dandelion. 0:01:54.520 --> 0:01:57.520 And while there's variation from one generation to the next, 0:01:58.000 --> 0:02:01.920 some are more favorable than there's, leading to natural selection, 0:02:02.320 --> 0:02:06.120 which leads us to how tough we've discovered life can 0:02:06.160 --> 0:02:10.200 survive to be. Until around thirty years ago, we thought 0:02:10.280 --> 0:02:13.440 all life on Earth needed energy from the sun and 0:02:13.520 --> 0:02:18.239 couldn't survive in extreme temperatures. But we were so wrong. 0:02:18.800 --> 0:02:22.200 When we explored hydrothermal vents on the ocean floor, we 0:02:22.280 --> 0:02:27.600 discovered clams, crabs, and giant tube worms. The latter survived 0:02:27.600 --> 0:02:31.840 through bacteria in their tissue that helped them derive energy 0:02:31.880 --> 0:02:36.240 from the water, subsequently feeding the other animals. What this 0:02:36.360 --> 0:02:41.320 potentially means is that life could exist in similar extreme 0:02:41.440 --> 0:02:46.880 environments on other planets or moons. In other words, big 0:02:46.960 --> 0:02:51.320 things have small beginnings. Now we're taking a huge leap 0:02:51.360 --> 0:02:54.480 in the likelihood of alien life, and while people like 0:02:54.600 --> 0:02:58.600 Frank Drake and Carl Sagan have speculated how many civilizations 0:02:58.600 --> 0:03:02.000 could evolve out there, we still don't know the basics 0:03:02.040 --> 0:03:07.040 of what extraterrestrials require to exist. Yes, we can work 0:03:07.080 --> 0:03:10.440 from variable traits were familiar with from natural selection, but 0:03:10.919 --> 0:03:15.000 would they be bilaterally symmetrical like humans or more like 0:03:15.120 --> 0:03:20.000 bacteria or viruses. Scientists in the field of astrobiology have 0:03:20.120 --> 0:03:23.680 drawn a few guidelines to how aliens might work. They'd 0:03:23.680 --> 0:03:27.040 be governed by the laws of physics and chemistry. Their 0:03:27.080 --> 0:03:33.239 bodies would also require solvency, temperature, pressure, and energy. In addition, 0:03:33.440 --> 0:03:38.240 they would probably be comprised of complex molecules, including informational 0:03:38.280 --> 0:03:43.880 molecules like DNA that carry their genetic information. So, armed 0:03:43.880 --> 0:03:47.880 with these assumptions about alien biology, to next find alien life, 0:03:48.160 --> 0:03:51.280 we've got to go planet hunting. Traditionally, we've looked for 0:03:51.360 --> 0:03:54.960 something like Earth, rocky, watery, and orbiting a star and 0:03:55.000 --> 0:03:57.920 what is called the gold Delock zone because it's not 0:03:58.040 --> 0:04:00.480 too hot and it's not too cold. It's got to 0:04:00.520 --> 0:04:05.119 be just right. But we've discovered three things about planets 0:04:05.120 --> 0:04:08.640 that make it much more likely that there's life out there. First, 0:04:08.680 --> 0:04:11.240 of all, water is not as rare as we thought. 0:04:11.360 --> 0:04:15.800 Take Mars, for example, scientists found water there inn or 0:04:16.200 --> 0:04:21.400 Jupiter's moon. Europa it's a freezing atmosphere, less mess bombarded 0:04:21.440 --> 0:04:24.599 by radiation. But we also think it has a deep 0:04:24.760 --> 0:04:28.760 ocean under its icy exterior that could have hydrothermal vents 0:04:28.920 --> 0:04:32.880 similar to the ones on Earth, spewing chemicals and nurturing 0:04:33.000 --> 0:04:36.200 strange marine life. If we stick with the assumption that 0:04:36.279 --> 0:04:39.839 water is essential to life, then the necessary materials are 0:04:39.960 --> 0:04:44.200 all over the galaxy, and Europa could also prove the 0:04:44.320 --> 0:04:47.240 second thing we know about the possibility of planetary life 0:04:47.560 --> 0:04:50.719 that life is way more flexible than we originally thought. 0:04:51.160 --> 0:04:55.159 We found strains of bacteria surviving under miles of ice 0:04:55.279 --> 0:04:59.839 in Antarctica for thousands of years. Could similar microbes be 0:05:00.000 --> 0:05:03.920 on Europa or somewhere outside our solar system. If that's 0:05:03.960 --> 0:05:06.520 the case, then do we discard the notion of that 0:05:06.720 --> 0:05:11.120 Goldilocks habitable zone near the Sun. And the third thing 0:05:11.160 --> 0:05:14.000 we now know about planets is what we said at 0:05:14.040 --> 0:05:17.600 the top of the episode. There are billions of them. 0:05:17.800 --> 0:05:20.520 By measuring the light coming from each star and then 0:05:20.560 --> 0:05:23.320 waiting for it to temporarily dim, we pose it that 0:05:23.360 --> 0:05:26.680 there's a planet there eclipsing the star's view. Now, how 0:05:26.680 --> 0:05:29.920 do we see this? Well? With the Kepler Telescope spacecraft 0:05:30.000 --> 0:05:33.720 launched in two thousand nine, Kepler orbits our Sun using 0:05:33.760 --> 0:05:37.720 a photometer light meter to monitor more than a hundred 0:05:37.760 --> 0:05:41.320 and fifty thousand stars, looking for any changes in their 0:05:41.320 --> 0:05:44.919 brightness to identify an eclipse. That's where we get the 0:05:44.920 --> 0:05:49.799 potential number of seventeen billion planets from Scientists then compare 0:05:49.880 --> 0:05:55.159 Kepler's findings with spectroscopic data from ground based observatories to 0:05:55.240 --> 0:06:00.320 confirm planetary candidates. And soon there will be two new 0:06:00.400 --> 0:06:05.839 space instruments to bolster Kepler's findings. The Transiting Exoplanet Survey 0:06:05.880 --> 0:06:11.760 Satellite or TESTS will launch in scanning for nearby exoplanets, 0:06:11.760 --> 0:06:15.599 and the James Web Telescope, scheduled to launch in eighteen, 0:06:16.040 --> 0:06:20.159 is so powerful it could analyze these planets atmospheres for 0:06:20.320 --> 0:06:25.000 signs of life. Kepler's already discovered several planets with inhabitable 0:06:25.000 --> 0:06:28.960 Goldilocks zones, but they're not at all like Earth. Instead 0:06:29.040 --> 0:06:32.360 of water and rocks, they seem to be small cores 0:06:32.400 --> 0:06:36.559 surrounded by atmospheres of hydrogen and helium, which doesn't sound 0:06:36.640 --> 0:06:39.400 life supporting at all. But don't forget there are still 0:06:39.560 --> 0:06:42.479 several ways life could exist on planets we used to 0:06:42.520 --> 0:06:47.520 consider inhabitable. There could be life deep under a planets subsurface, 0:06:47.600 --> 0:06:51.279 like the bacteria in Antarctica or the nematode worms discovered 0:06:51.279 --> 0:06:55.559 three point six kilometers below South Africa's deepest gold wine. 0:06:55.960 --> 0:06:59.840 Or what if a planet had shifting habitable zones attributing 0:06:59.880 --> 0:07:03.960 to a wobbling planet. Moving clouds could reflect radiation back 0:07:04.000 --> 0:07:07.120 into space, or temperatures could rise and fall dramatically, but 0:07:07.240 --> 0:07:11.760 at certain latitudes heat would dissipate, allowing for liquid water 0:07:11.880 --> 0:07:16.120 to resist boiling. It's hard to know if photosynthetic life 0:07:16.160 --> 0:07:20.680 could survive such drastic changes, but maybe it's possible. I mean, 0:07:20.880 --> 0:07:23.480 then diesel survived on such a planet in the Chronicles 0:07:23.520 --> 0:07:26.600 of Riddicks, so you know, I'd say anything's possible. Even 0:07:26.720 --> 0:07:30.600 moons orbiting exoplanets could be habitable if they were large 0:07:30.680 --> 0:07:34.200 enough to hold onto an atmosphere. For instance, even if 0:07:34.200 --> 0:07:37.400 a planet within a habitable zone didn't have the right 0:07:37.400 --> 0:07:42.400 composition for life, its moon might have rocky, watery settings 0:07:42.440 --> 0:07:44.800 like Earth kind of like end or in the Return 0:07:44.840 --> 0:07:47.080 of the Jetta, you know, the one with the Ewoks. 0:07:47.520 --> 0:07:51.440 As we've seen, the previously established rules for life sustaining 0:07:51.480 --> 0:07:55.640 planets are diminishing as we gather more and more information 0:07:55.720 --> 0:07:59.280 about the universe. However, this brings up the Fermi paradox, 0:07:59.480 --> 0:08:03.960 established by Enrico Fermi in nineteen fifty. If alien life 0:08:04.240 --> 0:08:08.520 or even civilizations exist in the Milky Way Galaxy, why 0:08:08.560 --> 0:08:16.360 haven't we detected them yet? Check out the Brainstuff channel 0:08:16.360 --> 0:08:18.480 on YouTube, and for more on this and thousands of 0:08:18.520 --> 0:08:33.000 other topics, visit how stuff works dot com.