- Good morning class, time
to put on your tinfoil hats! The question of whether or not
we are alone in the universe is something mankind has
wondered for hundreds of years. Is there life outside of Earth, and what would even make that possible? Well, the following theories explain why aliens are most likely out there. Here are 10 credible explanations why aliens likely exist. Number 10 is the number of planets. If we think of life as a phenomenon which requires a specific set of environmental factors to occur, then we can start to
work out the probability of alien life in the universe. Temperature, material elements,
chemistry, and stability, all of these things play their part. But the biggest number one factor necessary for life as we know it is to have a celestial
body, like a planet. You know, the perfect
neighborhood for life to evolve. Previously, we were not exactly sure that planets around other stars, known as exoplanets, actually existed. But, with the development
of the Kepler satellite, which can detect minuscule changes in a distant star's light when
planets pass in front of it, astronomers have detected
nearly 4000 planets so far. So, in other words, planets
are probably abundant, and that means that there
are plenty of places for extraterrestrial life to call home. You know, now that I think about it, an alien world would probably be perfect. Why would they wanna come here with all the farting cows? It's a thing, Google it. Number nine is the age of the universe. In case you didn't know,
the universe is about 13.8 billion years old. Our planet Earth has been around for about 4.5 billion years of that, with the oldest evidence of life being 3.9 billion years old. It wasn't until about 7 million years ago that the first hominoids evolved, and then finally, you
get us, the homo sapien, just a few hundred thousand years ago. But even within that
time, recorded history is only about 10,000 years old, probably because we didn't develop writing until about that time. Well, you know, that or there were numerous cataclysmic events that kept resetting our civilization. Mama, no! The point is, even if
it takes 4 billion years to get civilization, the
universe is way older than that. An extraterrestrial
species could've become technologically advanced
several times over during that time, so who knows how many alien cultures
could be out there? They're probably looking
at us right now like, "They're still using toilet paper? "They don't know about the shells." Number eight is the theory of panspermia. A big challenge in science
is to explore the conditions which led inanimate matter
to become self-replicating, evolving through natural selection. You know, that little thing called life. Most theories involve the
early Earth environment, but one theory is a little different. The theory of panspermia states that life didn't start on Earth, but
instead was brought here. Now hold on, before
you start to think that ancient aliens did it, panspermia actually refers to
the transference of bacteria. Microscopic critters were hitchhiking on an asteroid or comet,
which struck the Earth, depositing life into the seas billions of years ago. Furthermore, we know
that volcanic eruptions or large impacts could feasibly throw out rocky debris into space. This then spreads life
further from planet to planet. So, it could very well be that
we are the aliens ourselves, and that countless worlds have
been seeded, just like ours. Oh, I just realized what panspermia means. Get it, volcanoes just. That's inappropriate. Number seven are hydrothermal vents. We know for a fact that life arose at least once here on Earth, and we can speculate about other planets and say it's likely
that alien life exists, but we don't know that for a fact. However, by studying life here on Earth, we can increase our confidence. Now, there are many planets
that are nothing like Earth. In fact, most of them are quite different. Many of them are too far from their stars to have temperatures needed
for most life, like on Earth. In fact, some are called orphan planets and don't even orbit a star at all. But even these cold worlds may have life. You know, like ice people walking around. That's not what that means? Okay. Deep at the bottom of our oceans, there are hydrothermal vents, which spew heated gas and liquid from beneath the sea bed. Around this heat source, a rich
ecology of life has evolved without any sunlight at all. Astrobiologists hold out hope that even the remotest planets have such vents, and who
knows what creeps around them? It's like a little club
where all the alien life can get together and hang on the seabed. It's a lovely thought. Number six is the fertile solar system. We may not need to look very far to find extraterrestrial life if our own backyard is anything to go by. There are several
candidates for environments which could actually support life around our own solar
system, including Mars and the moons of Jupiter and Saturn. While so far, Mars seems barren, there are telling signs
that there may be life under the surface living in water. Around Jupiter and Saturn,
moons such as Enceladus, may have oceans of water underneath a thick crust of ice,
warmed by the tidal forces of the huge gas giants they orbit. Some people have even suggested that there could be multicellular life, such as fish-like creatures down there. If life has evolved several times across our own solar system, then this would again
support the hypothesis that the universe should
be teeming with life. You know, if there are infinite possibilities of civilizations, then that means that there
are infinite possibilities of what they could look like. Maybe they have hands
growing out their foreheads and something like that. It's gonna be a nightmare. Number five is the resilience of life. The universe is a hazardous place, filled with radiation and
extremes of temperature which would wipe out a
person in a blink of an eye. But, when you look at
the simple tardigrade, also known as a water bear, you realize just how resilient
life can actually be, even when faced with the
might of the universe. These microscopic animals
can survive in mud volcanoes, and at the bottom of the ocean, and can even withstand anything between minus 272 and 150 degrees celsius. It can even survive
without food for 30 years, tolerate 1000 times more radiation than any other animal,
and even survive in space. 30 years without food? I go 30 minutes without
food and I get hangry. And there are other lifeforms
called extremophiles, which can thrive in even
harsher environments. If life can be this resilient, then maybe there are all kinds of weird, almost indestructible creatures living out there in the vastness of space. And humans are definitely not one of them, because I just stub my
toe and I cry like a baby. Mm, fragile. Number four are the
building blocks of life. Knowing the building blocks of life can help us identify where it might arise. For example, scientists theorize that the molecule hydroxylamine is a building block of life. It's comprised of nitrogen,
hydrogen, and oxygen, elements which are common here on Earth. And astronomers have
detected it in abundance around a star just 1000 light
years from our solar system. So, it's very possible that where we find the building blocks of life, hopefully we can find life itself. But there are also scientific models based on hypothetical biochemistry that state that life on other planets may use different building blocks. We're carbon-based lifeforms because there's a lot of carbon on Earth, but perhaps on another planet, something like silicon is
the most abundant element, and therefore life could evolve from that. If that is the case, extraterrestrial life could exist in many more locations than we even imagine. Number three is natural selection. Evolution may mandate that there is extraterrestrial life out there, and not only that, but
that there must be life which has technology and uses
it to travel through space. Natural selection is the cornerstone principle of evolution. It's the idea of survival of the fittest, the idea that organisms
adapt to their environments and eventually thrive because only the genetic mutations
which make survival possible are actually passed on. We see it throughout Earth. Millions of organisms adapted to their surrounding environments. So, if we assume that some
form of natural selection leads to simple life elsewhere, then that same process will,
over billions of years, lead to creatures like ourselves who can change our environments. I would love to find out
that there are aliens that survived on a volcanic planet. Fire aliens! Sounds badass. Number two is technology is king. Okay, we are now heading
into some out-there ideas, but be brave and come
with me on this journey. I won't ask for much. Maybe your sanity, but that's about it. We are constantly innovating and creating new technologies, and those technologies then
lead to other breakthroughs. There is a philosophical concept that we are merely the
reproductive organs of technology, creating more of it until that technology can replicate itself
and head out on its own. Yep, hand over your sanity please. Arthur C. Clark explored this idea that space is so vast
that we wouldn't actually ever meet aliens, but instead, would encounter their technology. If there are aliens out there, they may be pieces of technology which replicate and explore the universe. In this way, one alien civilization could give birth to millions of others. And I'm fine with this, as long as they aren't the Terminator or the Borg. That would suck for us. And number one is the
strong anthropic principle. The strong anthropic principle states that the reason we exist in this universe is because our universe makes life likely. It's organized in such a way that all the laws of physics make sentient, intelligent,
technology-building creatures probable at some point. The mathematician James England has even developed a mathematical theory which states that life has to happen, that it's as miraculous as a rock rolling down a hill. It will happen because our universe has all the right
parameters to make it so. If this is the case, then it's very likely that we are not alone in the universe. And now you know, you may take
your tinfoil hats off, class. So, that was 10 credible explanations why aliens likely exist. But if you guys enjoyed this, remember to give it a big thumbs up. Also, be sure to subscribe to my channel, and turn on notifications by clicking the little bell beside
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watching and I'll see you on the other side. Time to take off!
