Are we alone? Recent amazing
discoveries have given us more hope than ever that our
universe is full of life. So why don't we see it? [MUSIC PLAYING] Why don't we see
alien civilizations? We've asked this question
before here on "Space Time," and if you haven't
seen that episode you should check it out. But today we'd like to go deeper
because it really does seem like there should be aliens. The Kepler Space
Observatory has told us there are a couple
of hundred billion nice, watery planets in the Milky Way
and probably billions of them are Earth-sized planets
around sun-like stars. Many of them have
been around long enough to produce
a civilization that could have easily colonized
the entire galaxy by now. So why is the Milky
Way so un "Star Warsy?" This genuine oddity is referred
to as the Fermi paradox and the resolution
for it has to be that there's some
sort of great filter that either makes
intelligent life extremely rare in the first place or
that wipes out, essentially, all advanced
civilizations before they get to the galactic
empire stage, whether by a nuclear war,
environmental catastrophe, accidentally making
a black hole that swallows the planet, et cetera. Personally, I'm not buying it. I just don't think that there's
an inevitable great filter still ahead of us. As we saw in a
previous episode, we're not so far from building
starships ourselves. Surely, some
civilizations must make it through these growing pains
and manage to reach the stars. So where are they? Well, there's another deeply
sad and deeply inspiring possibility. Humanity may be one of the
very first interstellar species in the history of the galaxy. But before we get all emo,
let's science this right. We know of exactly one
instance of intelligent life happening, the case of Earth. And as if it wasn't hard
enough to do statistics with a sample size
of one, we also have to deal with a
massive selection bias. Of course we're going to
observe at least one instance of intelligent life happening
because we are that one instance. In a way, it doesn't matter
how improbable sentience is. As long as it
happens once, it will be there to observe itself. Here we're touching on the
anthropic principle, which states that an
observer will always observe a universe that can make
observers or a planet that can. We'll talk about the
cosmic implications of this more in another
episode, but for now we need to acknowledge
that this selection bias allows that life could be
extremely rare, or even unique. Given that, can we even begin
to assess the likelihood of life out there? Yeah, we can science anything. So let's dig into whether
we should really expect to see a Salarian Empire. Let's take the knowns. Now, Earth certainly
required a number of very special
conditions to build life and it's hard to know how
essential each of these was or how frequently
these conditions are met through the galaxy. I'm going to avoid
details of the biology here because we
can say a lot just based on how much
time it took to get through each step on the path
to building technological life. We can crudely summarize
the big leaps that lead up to intelligent life
as one, assembly of self replicating RNA
from organic molecules; two, RNA based
proto-cells; three, DNA and the first actual cell-- this
is the moment of a biogenesis, life from not life; four,
increasingly complex single cells; five, the first
multicellular organisms so plants, animals, et cetera; and
six, the first intelligent life form capable of counting
to six on You Tube. Now, the crazy thing,
the thing that I find the least intuitive,
is that the first three steps in that chain
combined-- the appearance of true cellular
life-- happened faster than any of those later steps. so fast, in fact, that
it seems hard to believe. And in fact, so fast
that our galaxy probably should be brimming with
at least simple life. Let me explain. See, around four
billion years ago, pretty much just after the
Earth had first cooled down from being a giant
hellish magma bowl, we think that it
totally got pounded by a meteor storm that
lasted a couple of hundred million years. This is the late
heavy bombardment, and it probably
obliterated the surface. We think we know this
because we flew to the moon and found evidence of it. Up until recently, the
earliest known evidence of life dated to roughly
3.5 billion years ago, fossilized blue green algae
beds-- stromatolites-- found in Western Australia. The place was covered in
this greenish-purple slime that reeked of rotten eggs. Yeah, the beach was
horrible back then. Basically, Earth was once
a giant slimeball planet. And it looks like Earth
went from magma ball to slimeball in less
than 300 million years. What? That seems crazy fast. But it also suggests
that this first step, the genesis of life, is
not the great filter. But wait, the abiogenesis
thing gets even weirder. See, nature has provided
us with a perfect time capsule for studying
the very early Earth, zircons-- super hard silicate
crystals whose formation can be dated precisely by
the ratio of decaying uranium versus lead decay
product locked inside. And get this, just
recently a zircon was found containing the
possible signature of life and dated at 4.1
billion years ago, from before the late
heavy bombardment. That little crystal
contains what looks like biogenic carbon. That's a fancy way of saying
there's too little carbon 13 compared to carbon 12. See, photosynthetic
finds C12 a bit yummier, and so it absorbs more of
that than the heavier C13. Pretty much all carbon
enters the biosphere from the photosynthesizing
bottom of the food chain. Any carbon that's been
through living systems will have the same C13
light isotopic ratio that we see in this zircon. Now, there are other
nonbiogenic explanations, but this is extremely suggestive
that life was abundant on Earth remarkably soon after it
first coalesced from stardust and that life either survived
the late heavy bombardment or formed again after that
or the late heavy bombardment never happened. That's actually a
possibility, too. But either way, it
looks like Earth became a slimeball teeming with
life in a crazy short amount of time. How on earth did this happen? Two options. One, given the right
conditions the genesis of life happens like that, and two, it
didn't happen on Earth-- life was seeded from space, an
idea called panspermia. Look, there's no question
that lots of rock gets ejected into space
after meteor impacts and can move between planets. We've found plenty of
meteorites originally from Mars. A lot of the ejecta
from Earth is going to be swarming in bugs. Could similar
bacterial astronauts have once survived an
interstellar journey to Earth? Some bacteria are
certainly hardy enough to survive launch and landing. This has been tested. If these bacteria
were frozen solid, they could plausibly survive
a very, very long journey and you only need one out
of billions to make it. Maybe the solar wind
pushes infested material into interstellar
space so that tens of thousands, even millions,
of years later a single bug winds up on a brand new planet
and boom, instant slimeball. Questionable, but it
would mean that life only needs to evolve once from
scratch in any given galaxy. Now, this should
be very testable. Earth was infested
fast, so that means this stuff should be out there. Mars must have been
hit when it had water. Did it go slimeball? There should be something
like stromatolite fossils on its ancient surface. We haven't seen them yet,
but they'd be hard to spot. These cosmic cooties should
be findable in space, too. So either fast abiogenesis
or panspermia, one of them must be true. However, both suggest
that the galaxy should be teeming with slimeball
planets filled with life. Now, that's exciting. We don't have a telescope
to find them yet, but we could soon. These planets will
have atmospheres driven by biotic processes. If we could analyze
light passing through these
atmospheres, we would see signatures of
oxygen, ozone, methane, nitrous oxide at concentrations
impossible without a biosphere. Properly fund NASA and
its terrestrial planet finder and we could find
extraterrestrial life within 20 years. So it's entirely
possible that we'll soon discover that the galaxy
is filled with life. But this just makes it
weirder that the Milky Way isn't swarming with
ancient alien civilizations. There is a filter, but it's
not the genesis of life. The clue might be that the
Earth stayed a slimeball for nearly three billion years. The first multicellular organism
turned up only 600 to 800 million years ago
and life as we know it quickly exploded after that. Was this a random lucky event
that we just had to wait for? No, multicellular life evolved
independently dozens of times. It just took a really long
time for those single cells to become complex enough
to form large collaborative structures capable of
collective reproduction, i.e. plants, animals, a species
capable of making the Kerbal Space Program. And speaking of space
programs, technological life took a little while
longer, but not really so long on the overall
scale once we had complex life. After the Cambrian Explosion, it
was only around half a billion years to go from
jellyfish to moon landing. Of course, maybe the
emergence of intelligence is a random and unlikely
event, and this one is the hardest to assess. However, it's worth
noting that we do have other
species on Earth that seem to be moving down the same
big brain path independently of humans. So what is the great filter? Maybe it's just time. If life is common, then of the
billions of Earth-like planets in the galaxy, only
a tiny fraction needed to have a small
head start on us in order to have produced the
Federation of Planets and Stargates and stuff by now. So what if humanity
started early? Of all of the sun-like
stars and Earth-like planets that will ever form over
the full past and future history of star formation in
our universe, Earth is early. It's part of the
first 8%, according to recent Hubble Space
Telescope based calculations. We have emerged in the
epoch of life in a universe abundant in the rich resources
of past supernova explosions, but after the violence of the
starburst and quasar epochs. It strains
believability to imagine that life didn't or
won't happen elsewhere, but it is possible that we
are a very early outlier and that any other civilizations
are so distant as to not yet be apparent. Is humanity a first
generation intelligence, one of the species that
will watch and maybe guide as other intelligent life
emerges throughout the galaxy? Well, there's something to work
towards on the next episode of "Space Time." Last week we talked about
Miguel Alcubierre's warp drive. You guys had a lot to say. Let's do it. A lot if you noticed
my mistake in saying that Miguel Alcubierre is
Spanish, rather than Mexican. That was my mistake. We cram a lot of details into
each episode of "Space Time" and sometimes things like
this do slip through, so thank you for catching it. Miguel Alcubierre was, in fact,
born in Mexico and, in fact, educated up to
master's level there. Eric Vilas wonders
what it would look like seeing an
Alcubierre warp bubble race by from the outside. This is tricky. The bubble would
definitely leave some sort of light signature because
light inside the bubble can traverse the walls in any
direction besides forwards and our negative mass matter
may also end up on the outside. Because the bubble
is superluminal, any light that we see
would trail the bubble just like the sound of
a supersonic jet. Ahead of the bubble,
you'd see nothing unless it stopped, in which case
all the photons and particles that are captured on its journey
would blast you into oblivion. Now, a few of you took
issue with my statement that it's never aliens. And fair enough, it's never
aliens until it's aliens. The point of this philosophy
is that the alien hypothesis is a bad place to start
because you can explains almost any weird natural phenomenon
as having been produced by a super intelligent,
extremely high tech civilization with
inscrutable motives. Really anything. It's a week hypothesis
until you've generally ruled out everything else or
you actually see the mother ship and take an unsuspiciously
blurry photo of it. So Nate asks if we can please
do another challenge episode. Absolutely, we'll do one soon. [MUSIC PLAYING]
and some more info on the Fermi Paradox
Ayy lmao
Quick reason and what they touch on a bit...we just started looking with tools that are inadequate for looking for signs of life. Also the universe is so big life could be common but so far spread out that we may never see or touch another alien life without some science fiction warp drive or wormholdes...assuming those are even possible...if they arent the chance of ever running into another life form is almost zero.
That would fit Fermi Paradox: Intelligent civilizations are too far apart in space or time and It is too expensive to spread physically throughout the galaxy.
If we aren't the oldest or one of the oldest intelligent life forms and there are more that are vastly older and advances then its reasoned there would be a lot more older than us. The older they are the more likely the ability to break the limits of distance like warp-drive are less likely, as if even one found it and has spread they spread so rapidly that the evidence of life would most likely be detectable on a macro scale (reading the space for light, radio waves or any patterns).
So if it is possible to break the distance problem then they have achieved it recently and isn't common therefore we are among the oldest or most advance or its not possible to break that limit and we will never be able to close the distance gap to discover new intelligent life.
It's pretty amazing that humans are intelligent enough to understand that. And it's pretty amazing that I use an apostrophe while I type on my computing mechanism sitting on a bed created by a company I have never heard of for the purpose of fighting the pains of gravity while I sleep at night.
Better question would be:
Why haven't they found us?
One redditor(cant remember username) put it very aptly "Its like looking at a single drop of the ocean and wondering where the dolphins are."