If you ask my personal opinion, I think
that alien life is probably pretty common in the universe. It's entirely
plausible that it exists within our own solar system,
perhaps on Europa one of the moons of Jupiter, which is thought to have a vast
ocean underneath it's icy surface. But by alien life, I mean life like bacteria,
molds, and other one celled creatures. I think complex intelligent life, like
mammals, birds, and lizards is probably very rare. And super intelligent
spacefaring life-forms, like humans, is probably exceptionally rare. But this is
not to say they don't exist. But whenever you read about alien visitations, or see
alien creatures in the movies, they're depicted as looking almost like humans.
They may just have bigger eyes, or bigger heads, or they look like some other
animal that we're already familiar with on earth. This is a good reason to be
highly suspect of any claims of alien visitations because aliens are highly
unlikely, or near impossible, to look anything like us.
Why?...because aliens on another planet would evolve in a completely different
trajectory, under a completely different set of environmental conditions, and
circumstances, and are not at all likely to look anything like us, despite what
you see in the movies. In fact, they may look so different, that we may not even
recognize them as life-forms at all. So if aliens really did visit us, what would
they really look like from a science perspective? The explanation is coming up
right now... Guys before we talk about life on other
planets, I want to tell you something great that's available right here on
earth, and that is Magellan TV. If you like my videos, then
you're gonna love Magellan TV. It's a new type of streaming documentary service
that I think you'll really enjoy. It was founded by filmmakers and
producers who bring premium in-depth documentary content. This video was
inspired in part by a documentary that I watched on Magellan TV called, "Aliens walk among us." It's hosted by none other than Captain Kirk of Star Trek, William
Shatner. Featured subjects on Magellan TV include history, nature, and of course,
science and space. You can watch it on any of your devices, as well as your TV
any time, without any ads or any interruptions, and in 4k. Magellan TV has
a fantastic offer right now for Arvin Ash viewers. If you use the link in
the description, you will get a free one-month trial. I highly recommend
Magellan TV, but be sure to use the link in the description. To understand what
life on other planets may be like, first let's look at the raw ingredients that
life has to work with in the rest of the universe, compared to our solar system.
The most common elements in the universe are, in order,
hydrogen, helium, oxygen, neon, nitrogen, carbon, silicon, magnesium, iron, and sulfur.
And in our solar system, it's almost exactly the same. So as you can see from
this chart, our solar system is essentially made of the same elements
that the rest of the universe is made of. So in that sense there's nothing special
about the elements available in our local group of planets, and our Sun. And
the most common elements on earth are iron, oxygen, silicon, magnesium, and carbon.
So Earth is composed more of the heavier elements than the rest of the solar system.
Why would this be the case? Earth has relatively modest gravity compared to
the Sun and some of the heavier planets, like Saturn and Jupiter. It's not able to
hold on to much hydrogen, helium and other lighter elements which tend to
float away from its gravity. It should not be surprising, then, that the lightest
elements, such as hydrogen and helium, would be more concentrated in the Sun and the
more massive planets, like Jupiter and Saturn. But the key element of
life is carbon. Carbon is the backbone of every known biological molecule. Carbon
can form four bonds with other atoms simultaneously. This makes it well suited
for long chains of molecules that serve life, such as DNA. Organic chemistry, or
the chemistry of life on Earth, is based largely on carbon. Is this unusual? Is
this what we would expect to see on other planets of the universe as well?
You might look at the composition of Earth and say, "well there's a lot more
silicon available on earth." And if you look at the periodic table, silicon is in
the same family of elements as carbon. So why can't alien life be based on silicon?
This seems plausible, but when you look more closely at the properties of
silicon, you realize why life chose carbon instead of silicon, even though it
is about a hundred and fifty times more abundant. The four bonds on carbon are
all about the same strength and stability. With silicon, the first bond is
stronger than the rest, so this causes instability of certain chemical
reactions with silicon. In other words, carbon is capable of forming large
complex chains of molecules like DNA. Silicon is not. It is unstable. So the
complexity required for organic chemistry with silicon is just not there.
Carbon is also such that its bond with other atoms, such as nitrogen, hydrogen, and oxygen is about the same strength. So it's relatively easy for carbon to react
with a variety of other elements. In other words, it is a more reactive atom
for chemistry. Silicon is just not as reactive with other elements, and not as
stable in large molecules. And given that life chose carbon, when silicon was much
more available to us on earth, advanced life based on silicon instead of carbon
is unlikely. besides carbon, what does life on Earth have in common? All life
uses liquid water as a solvent, and adenosine triphosphate, or ATP, to store
and release energy. It's likely that if life on other planets is based on carbon,
it will also need some type of energy molecule, either ATP or something similar.
But does it necessarily need water? Water is the most abundant compound in
the universe. This should come as no surprise, because it's made up of
hydrogen and oxygen, the first and third most abundant elements in the universe.
It's a good solvent because it's liquid over a large temperature range.
Everywhere there's water on earth, life is also there. So life based on water
could be quite common. Ao far, it would not be a bad bet to presume that
intelligent alien creatures on other planets could be based on carbon
chemistry, and water. This is not to say that chemistry could not exist in other
solvents, such as liquid ammonia, or methane, which is prevalent for example
on Titan, one of Saturn's moons. But from what is known about earthly chemistry, it
likely would not harbor complex intelligent life. Would aliens be in the
same environment as Earth?...Probably not identical. But temperature-wise, Earth is
unique in the solar system because it is the only planet or moon where water can
be found in three different phases, solid, liquid, and gas at the same time. So for
example, if you're sailing on a ship on a foggy day, and see an iceberg, you're
viewing water in all three phases at the same time. There is a critical zone, or
distance from the star where a planet is not so hot such as mercury, where it gets so hot that water boils away, but also not too cold ,where water freezes. This is
crucial for life because liquid water provides the medium, or solvent, in which
complex organic chemistry can take place. This can't happen in ice, and it so
happens that the boiling point of water, 100 degrees Celsius, is close to the
upper limit of organic chemistry. So if our planet was too hot, organic chemistry
would not work. But our alien planet could certainly have a different ratio
of water to land. And it could have a different gravity. According to the
latest Kepler data, there appears to be many more planets bigger than Earth than
there are the same size as Earth. So there's a larger prevalence of so-called
"super Earth's" in our galaxy. These are planets about 1.25 to 2 times the size
of Earth, and would have gravity about two times to eight times that of Earth.
But it's not known whether these are rocky planets, like the earth and Mars,
or gas giants, like Neptune or Uranus. So for now, let's presume that we would need
a planet similar to earth in size, and perhaps 0.9 times to 1.1 times the size
of Earth. Given the size of the galaxy, with 200 billion stars, such a narrow
range of planets would still be plentiful - in the millions. So let's look
at what life would be like on an earth-like planet, in the habitable zone of a
sun-like star, based on carbon chemistry and water. To do this, I've teamed up with
astrobiology authority, and zoologist Biblaridion. Check out their YouTube
channel Biblaridion for more stuff like this.
Here's him: We can be pretty certain that some of the tendencies we see in
organisms on Earth will be universal. Some life forms would gain energy from
star light, like plants, while others would survive by feeding on other
organisms, like animals. In the latter case, these life forms would need a way
of taking in nutrients and expelling waste, which may take the form of a body
cavity, with separate openings for feeding and excretion. More complex
animals will also have some way of sensing and reacting to their
environment, the analogs of eyes, ears and noses, which would form the equivalent of
a nervous system. In particular, eyes have evolved many times among completely
unrelated lineages. For example, the eyes of octopuses, scallops, insects and
mammals, are all thought to have evolved independently of each other, but still
serve the same essential function. So it seems likely that eyes might be common
on alien worlds as well. But alien eyes might be sensitive to different
wavelengths than our own, since they will adapt for the peek spectrum of their own
Sun ,which may be different than Earth's. So they might see the world in a very
different variety of colors than we do. They might be able to see into the
ultraviolet range, like many birds and insects, or to sense infrared, to detect
the body heat of other animals, like pit vipers or vampire bats. However their
eyes work, they would most likely need more than one, since having multiple eyes
would allow them to sense direction and depth. Animals on earth have anywhere
from two eyes, like in most vertebrates, to over a hundred, like in some bivalves.
Another trait found in virtually every lineage of complex animals is a
symmetrical body plan, whether it's radially symmetrical like
in starfish and jellyfish, or bilaterally symmetrical like in arthropod and
vertebrates. This symmetry is almost always accompanied by cephalization, the
concentration of the nervous system and the mouth towards one end of the body,
forming a sort of head. So it seems quite likely that like many animals on earth, a
complex alien body plan would exhibit some form of symmetry, and have a
distinct head-like region of the body that bears at least two eyes and a mouth.
When it comes to intelligent life as we would classify it,
the organisms would obviously need a large brain capacity and the ability to
learn new information to form a culture. They would need some way of transmitting
learned information from generation to generation, and to communicate and
cooperate with other individuals, like a language. Their language might not be
based on sound like human languages are, but perhaps involve other modalities,
such as movement - like sign language, pheromones, changes in skin color, or
texture, or even a combination of all of these. To build the tools and structures
necessary for an advanced civilization, they would also need a means to
manipulate the environment around them, such as limbs, or digits of some sort, to
handle objects and probably the ability to perform fine motor movements. These
need not be fingers, but anything that can hold objects, perhaps prehensile
tentacles, tipped with smaller digits. Do they live in the sea? In the clouds of a
gas giant? Or on land? Using our one data point of Earth, there is no complex life
that lives permanently in the atmosphere. And most intelligent species on earth
happen to be on land instead of the sea. You might say, "what about dolphins and
killer whales?" You have to remember that these animals were once land mammals (evolved on land). They went back to live in the sea. That's why they still need to breathe air. Does
living on land provides some kind of evolutionary bias towards higher
intelligence? According to physics professor Bernard Bates, at the
University of Puget Sound, aliens with advanced technology would have to be on
land because technology needs fire to kick-start it, by providing a survival
advantage, and a way to create advanced hunting tools. This can't happen in water.
Light from the sun also does not penetrate as deeply in
oceans. There's very little light beyond 200 meters in the ocean. So the energy
that ocean creatures have to work with is less than the energy available on
land. This makes it harder for larger, complex creatures to evolve. Once again,
here's Biblaridion: So if an alien species lives on land, it would also need
some means of terrestrial locomotion. Limbless creatures might slither like
snakes, or use muscular ripples like gastropods or worms. But on earth, both
vertebrates and arthropods independently evolved legs, which are much more
efficient and allow for greater speed and maneuverability, than other forms of
locomotion. So any land dwelling aliens would likely do the same, if they have
suitable structures available to adapt into walking limbs. Having evolved from a
4 fin ancestor, most vertebrates have four legs. Though some, like humans,
kangaroos, and dinosaurs walk on just two, while arthropods can have anywhere from
six to several hundred legs. However there is a trade-off here when
it comes to optimal limb configuration. the more legs an animal has, the more
stable it will be, but the more energy will be needed to power and coordinate
the limbs, making running less efficient, especially at large body sizes. It could
be that large active animals are biased towards a smaller number of legs, though
this is difficult to say with any certainty. This trade-off is especially
relevant to predators, which need limbs that have specialized for efficient
running to catch prey. Often predation also involves complex behaviors such as
stealth or cooperative hunting, which demands a greater intelligence. In humans,
the evolution of a larger brain occurred alongside a shift to a more predatory
lifestyle. So intelligent aliens may also descend from predatory ancestors, and
therefore, might tend to have a smaller number of walking limbs that are
designed for efficient high-speed movement. There are probably only so many ways an alien can efficiently see, eat, walk, and communicate. And natural selection on their planet would probably weed out inefficient body plans. How prevalent is
intelligent life likely to be in the universe? Dr. Yael Kissel, scientist at
NASA's Ames Research Center, and other scientists believe that most life in
the universe, as a whole, is likely to be
microbial. But does simple life like bacteria inevitably involved into more
complex intelligent life? Well it's important to realize that evolution
doesn't have any end goal. It simply selects for whatever traits provide an
immediate advantage. In fact, in some contexts, evolving to become more
intelligent might actually be a detriment to some species. For example,
predators such as wolves and big cats have achieved a relatively high level of
intelligence, compared to other animals. But if they became any more intelligent,
the enormous energy demands of supporting a large complex brain may
outweigh the benefits it provides. So further intelligence may not be selected
for. Human intelligence, which is far beyond any other living thing on earth,
and which needs to be supported by a huge energy investment, not only by our
metabolism, but also by our culture, and technology, may be an aberration and not
advantageous outside a very specific set of evolutionary circumstances. So we may
be an exception in evolution, or the result of a series of coincidental
mutations in our ape genome. But given the vast numbers of planets in the universe,
it seems that even if our intelligence is an accident, takes a long time, requires
circumstances like being just the right size planet, located at just the correct
distance from its star, having a large moon to balance our seasons, and being in
a stable part of the galaxy where we didn't get wiped out by a meteor or
gamma burst, we should still have company, intelligent neighbors somewhere!
They are likely, however, to be so far away that we may never actually
encounter them. Seth Shostak, astronomer the SETI Institute, believes that our
first encounter with aliens will likely not be with carbon-based life, but
silicon-based life. He says that because he believes that our first close
encounter will not be with biological creatures, but with their highly
intelligent machines, or probes, that use silicon chips for processors. They would
have sent these out to the far reaches of the galaxy. This makes sense if you
consider that this is also the likely evolution of us here on earth. We are
much more likely to send probes to our nearest neighbor, Proxima Centauri,
4.5 light-years away, for example, than humans. So the next time you see little
green men in movies, realize that this is probably fantasy. Life-forms that we
encounter would be completely different than us.
They might be little. They might be green. But they will almost certainly not be
men. Guys if you want more of this stuff, then check out the Biblaridion channel
at the link in the description. And if you like this video give us a like and
leave me a question, because I try to answer all them. I will see you in the
next video my friend...
