“There is a theory which states that if ever anyone discovers exactly what the
Universe is for and why it is here, it will instantly disappear and be replaced by
something even more bizarre and inexplicable. There is another theory which states that
this has already happened.” - Douglas Adams So, today we’ll be discussing some common
misconceptions about space, time, life, the Universe, and everything. Some of these
are pretty well known but have a twist, some are well known misconceptions but actually
wrong themselves, and some are sadly less known and we’ll be correcting those today. We have a
lot of topics to cover, from common misconceptions about space – that it is cold, or dark, or empty,
or quiet – to grander ideas like where the edge or center of the Universe are, its beginning
and end, and how we might travel around it, see new worlds around alien suns, and even
survive the death of the stars themselves. I feel obliged to say from the outset that this
episode is going to have a lot of “Actually” moments, where it might seem like a nitpick, and a
few probably really are, tastes vary and some are really there for completeness or a bearing on more
important misconceptions, or less well known ones, including how some of our worldview is constructed
around these concepts and is arguably flawed or at risk of being blinded to new evidence or correct
conclusions because of them. This episode is not about pointing out a few irrelevant technical
errors that really have no relevance to day-to-day life, and to poke at the realism of a given
work of science fiction – though we’ll do that too – but to suggest different ways of looking
at the Universe and our place in it, both now and in the future. And indeed many of these become
relevant in the very deep future, eons from now. The Youtube version of this episode has
been chapterized to make it easier for individual viewers to jump to specific topics
of interest, but as always, our episodes are written and created with the principal intent
of being watched as an episode, not a reference book. It’s going to be a longer episode than
most, so a drink and snack might be advisable. I thought we’d start off by quickly hitting
five big qualities of space that get assumed, one of which people get right but understandably
can’t really wrap their heads around, and four others that get misunderstood. Those five commonly
misunderstood qualities which I’ve listed are: That space is huge, that it has no
gravity, and that it isn’t dark, that it isn’t cold, and that it isn’t empty.
Everybody gets that Space is Huge, but trying to really wrap your head around just how huge is
just not doable. It is immense in a way that only numbers can describe, rather than experience, and
even those of us used to the math and scale have to constantly work not to make horribly off-target
speculations simply because of how non-intuitive everything is. Earth is huge, but understand
that if you’re on a tall hill or skyscraper being impressed by how much of it you can see,
that whole landscape or cityscape around you is maybe one single letter in the entire big
book of the planet’s surface, and your whole lifetime and the lifetimes of everyone you know
takes place during a period that’s only a page in humanity’s own history, itself barely a page in
this planet’s. There is no understanding of that immensity and yet the tiny flyspeck of your or
my existence against the story of this world is still big compared to the miniscule dot that our
world is in the crushing hugeness of this galaxy, which in turn is only trillionths the size
of the known Universe, which itself might be a speck against the great total of reality.
There is no managing something like that in the mind, and as we’ll talk about nearer the end,
the shadow of that immensity sits very heavily on science and science fiction, influencing
a lot of our perspectives, even while at the same time nobody ever really manages to truly
capture the colossal nature of space and time. Some of the other aspects of space aren’t so hard
to capture though. For instance, the confusion that space has no gravity is a big misconception.
When orbiting an object, whether it’s our space station around Earth or Earth around the Sun, the
nature of the mechanics involved are basically placing you in free fall, perpetually, but just
like when an elevator starts or stops, gravity isn’t in any way shutting off. On the space
station you’re only a few hundred kilometers up, the planet itself is thousands of kilometers wide,
gravity is only a few percent lower up there. It’s just that you are orbiting by constantly
being flung sideways as gravity pulls you down, and that is constantly changing the
direction that gravity is coming from, so when your speed is just right, and there’s no
air in the way, it allows you to essentially fall right back to the same spot, over and over again.
Air is critical here because orbit right over the Earth’s surface, and the air drags your speed
down. We only put satellites as high as we do because that gets them above the air drag. We
literally want them as low as we can possibly get them to, see our episode on Stratospheric
Satellites for more on that. Stop the space station though, with a magic hand, and you
will fall right to the floor. Nor is it really zero-gravity, there are lots of other forces and
minor variations, it’s just minimal and so we call it microgravity. Normal gravity, what we have
here on Earth, is 9.8 m/s² or 32 ft/s² and we call that 1 gee, much as we call Earth’s distance
from the Sun one AU, or Astronomical Unit. The Sun and Moon’s gravitational pulls on Earth
are what cause our tides, moving trillions of tons of water and ground along. If we froze Earth in
place and removed it, so just the Sun was pulling on us, it is just under a thousandth of a gee,
and on the Sun’s surface it’s 28 G, and the escape velocity from the Solar System from Earth’s
position is 42 kilometers per second, almost 4 times what the escape velocity from Earth’s
surface is. It’s more than 10 times that to escape to the galactic rim. There is no known natural
place where you can’t feel gravity or escape its effect, and even stuck at the center of a planet
or between two identical and massive objects, like a pair of binary neutron stars or black
holes, that merely means the pull of gravity is balancing out. The time dilation experienced there
remains enormous. As gravity slows the passage of time, the stronger it is in total, not net.
Much like gravity, there is no place free of light in space either. Space is not Dark, and
only in the shadow of a planet or moon is our Sun ever not shining all day, every day and it
is actually brighter than here on the ground, even at high noon, and perpetually so. Even
out on distant Pluto, during the day time you would have light comparable to modest room
lighting and much brighter than the full Moon. Out in deep interstellar space there’s an ambient
starlight that varies in intensity and spectrum, locally a bit over a percent of the Full Moon,
which means you could see enough to walk around, if clumsily without a flashlight, even on some
dead frozen rock in the Oort Cloud. Alternatively, inside star clusters or the galactic bulge it
might be hard to find any place that wasn’t at least full moon bright all the time, and
many places where darkness is only inside buildings or caves. The average color
of starlight in the Observable Universe is a shade of yellowish-white-beige
named Cosmic Latte, though for a time; from a miscalculation we thought it was more
of turquoise. Either way, there’s always light. There is also tons of radiation in other
frequencies, from radio and microwave up to X-Ray and Gamma. Most of the universe is
indeed darker than daytime or full moon light, but the notion that space is pitch black is wrong,
the darkest places are always those in shadow. Similarly, the notion that space is Cold
is also wrong, though that needs several qualifiers. First, cold is not really
a science term, as some measurement, but more of a relative state. Something is hotter
or colder than something else it’s compared to. What we have is temperature and total heat,
or thermal energy in something. The air in a hot oven is much hotter than a pot of boiling
water, but that water contains a lot more mass than the air in that oven has and any given
material also has a thermal capacity. Air has only about a sixth of the thermal capacity
of water, so raising the temperature of a kilogram of water by a degree takes six times
the thermal energy a kilogram of air does. There is also thermal conductivity, which is
how quickly something leaks or absorbs heat, Styrofoam is low and slow to change while metals
are quick, which is why you can keep your coffee warm in a styrofoam cup in the winter and not burn
your hand touching it, while touching metal can give you quick frostbite or burns in the summer,
even though they’re roughly the same temperature as everything else there. Space is not empty
but it nearly is, so we don’t really lose or gain heat by conducting it out of ourselves
there, or by convection, merely by radiation. This is why stars burn so hot, they are actually
very thin and cloud-like by and large, especially the large ones. Our Sun is only slightly denser
than water overall, only about a quarter the density Earth is, and its upper regions that
we actually see are even thinner than air, nothing like the implication we often have of
it being a big ball of fiery lava, and more on that later. But the Sun doesn’t really end there,
what we call the surface is just the photosphere, the place where most of its light comes from, it’s
not the hottest place or the end of the Sun and there’s no real definition for the end, it just
gets much thinner. Most of the matter in our solar system is far hotter than the hottest places on
Earth, and even our own core is not terribly hot. Gases have their temperature basically off of how
fast they are moving and what they are in terms of atoms and molecules, and so a place with
fast-moving gas might be so thin in density that you only had a few atoms per cubic meter,
and thus less heat energy than an ultra-cold cube of ice has, and yet its temperature might
be a million degrees. You could still freeze to death in it, as you radiated heat faster
than you absorbed sunlight or starlight, or for that matter cook to death, just depends
where you are. If we exposed you to the vacuum, then you would freeze only in the sense the liquid
state of matter, as opposed to solids and gases, which only exist where there is pressure, and the
range of temperatures they exist at narrows as pressure lowers, and widens as it gets higher.
Water freezes at 0 Celsius and boils at 100 Celsius at normal pressure, but boils at much
higher temperatures under greater pressure. You will actually get a mixture of both the
boiling and freezing of the water that’s in a human that is suddenly exposed to space, so it’s
not really wrong to say someone freezes in space, especially as if they’re decently far from a
star, the remaining water will stay that way, rather than boiling off, which is why
water ice is ultra-common in the outer solar system but not the inner, and is
why comets have those beautiful tails. It is actually kind of weird because we also tell
people that the Universe is cooling over time as it expands. And this is true if we’re talking
about the average temperature of a given cubic meter of empty space as opposed to the average
temperature of a given atom in the Universe. However, the actual average temperature of deep
space is much higher, about 2 million Kelvin, versus more like 200,000 10 billion years ago.
This might seem at odds with saying that the Universe is only about 2.7 Kelvin, way
colder than Antarctica or even Pluto, but that’s the temperature of the Cosmic
Microwave Background Radiation, or CMB, permeating everything and thus is the coldest you
can get anything down too, currently. Like a big hunk of metal floating in deep space that rapidly
radiated off its heat but was so big and dense that the occasional collision of a couple atoms
– even if they are millions of degrees – just doesn’t do anything to warm it. Nor is the CMB
the only type of ambient radiation out there, just a very old one that’s basically everywhere.
Which takes us to the misconception that Space is Empty, as there’s something like a half a billion
of those CMB photons left over from the dawn of the Universe passing through any cubic meter of
space at a given time, even in ultra-deep space, out in the cosmic voids between galactic filaments
and walls. Ignoring Dark Energy for the moment, there’s plenty of other random matter, even
out in those voids, indeed even whole galaxies, but inside galaxies the density of space is a
lot higher. It is ridiculously tiny compared to here on Earth, the densest known body in the
solar system curiously, but it is not empty and we have regions of space where the interstellar
dust and gas is a lot higher than in our solar system at large, millions of times so, and it
is much denser than the intergalactic void. Even beyond that though, if we block off
every form of radiation getting into some shielded volume and find and pull out
every single atom floating around, we still have the reality that what we normally
think of as reality but is actually built on a Quantum Universe. Everything going up here is
a statistical byproduct of Quantum Mechanics at that scale, and down there everything
is in a constant state of uncertainty, with packets of energy and matter popping
into existence and right back out again, after lengths of time so tiny, they
make a second look like untold eons. But just as billions of photons of light can zip
through a volume of space every second, each there for less than a billionth of a second, as long
as the light source is still emitting photons in that direction and at the same rate, that volume
of space being measured will still have a constant density of new migrant photons, like traffic on
a road, nobody lives there but it’s always busy. So too all these particles flickering in and out
of existence for fractions of an instant do cause a net density. And this is everywhere, all of the
time. So, even in a sealed-off vacuum, space is never really empty, and indeed when we add in
dark matter, which would casually pass through any shield more easily than a neutrino, and dark
energy, which seems to just add tiny packets of new space, which contains energy, everywhere all
the time, space can never be said to be empty. That won’t stop you from asphyxiating in space
though, as empty is pretty relative, but when it comes to the notion of exploding when you get
pushed out an airlock into a vacuum, that’s no more real than rapidly turning into a brittle ice
statue that would shatter moments later if bumped. Explosive Decompression was really popular in
science fiction and I’m glad to say has mostly been retired as a trope. Pressure differences
can be brutal but the force just isn’t there to tear you apart. It’s a difference of just 1
atmosphere, and you can experience the reverse by swimming down about 10 meters or 32 feet
underwater, go about 3 or 4 times deeper and get about 3-4 more atmospheres of pressure.
Normally space is basically 0 pressure and Earth air is about 1 atmosphere of pressure,
so that difference isn’t that much. Nobody is getting sucked through a bullet-sized hole in
the wall, maybe one that was almost as big as them would have enough pressure to squish them
through but otherwise they just plug the hole. Nor does all the air rush out in moments. Poke
a little hole in a space suit or space station wall and air will leak, but rather slowly, and
you can just put your finger over it or tape it. The water in your plumbing is often under
several atmospheres of pressure and yet a hole in a pipe can be covered and doesn’t rip
things open, you could put your finger over it with fair effectiveness. If you’re wondering what
a hole in a spaceship would be like to handle, grab a vacuum and turn it on and put your hand
over the wand, or a bike pump and put your finger on the nozzle and press the pump handle
about halfway down, compressing the air to about 2 atmospheres pressure. If you’re thinking
that a household vacuum isn’t a total vacuum, it’s probably also fair to point out that most
space missions are at partial pressure too, keeping the oxygen content of air high but going
low on nitrogen, to slow leakage. Leakage occurs at the rate of pressure difference, half
your pressure, half your leakage rate. There’s no noise in space
In space, all is silence, and everyone knows that and it's mostly right. Scifi
movies often ignore it to add in sound effects, and you can get some stirring battle scenes
as they switch perspectives from a loud battle setting to one of total terrifying silence, as
explosions dot the eternal dark void. And again, this one is mostly right but needs caveats.
First, sound is vibration and you will get it wherever there is a medium of matter to travel
through. So anything hitting or landing on your ship or station still causes bangs and clunks. If
you’re running around a voided ship or asteroid mine touching the ground, you’re going to
feel vibrations through it and thus noise. Plus there’s no real place that is a total
vacuum so there’s never really an absence of sound. There are plenty of places in the
Universe where the interstellar medium is a lot thicker than local space, and indeed you can
hear sound very high up in our own atmosphere, long after it would be unbreathable. We actually
have heard a black hole that was in a galaxy cluster with so much gas that it vibrated it, and
we can read that vibration electromagnetically and play it. It is decidedly eerie.
Black Holes Suck Speaking of black holes, the notion they suck
everything in and destroy all matter nearby is another case of ‘not exactly wrong but yet, very
wrong’ as naturally occurring black holes might be several kilometers across and absolutely fatal
to touch or get fairly close to, but they are basically harmless compared to the Supergiants
that formed them, millions of times brighter than our own Sun and many millions of Kilometers
wide. They’re safer to be near than a planet even, as you are only in danger from them from the
radiation they emit from slowly sucking in gas, or if you are so close that tidal forces will rip you
asunder, and both of those would be vastly closer to that black hole than you could normally be near
even a dim small star. They’re stealthy, to be sure, but you would detect the potentially lethal
radiation long before it got dangerous to you. So the idea that a black hole is going to sneak
up on your ship as it travels, even if for some reason you had no map to warn you, is just wrong.
So is the idea that you can’t escape a black hole. You don’t really fall into black holes anymore
than you do stars or planets, and indeed less so, since only the most highly elliptical orbit
would crash into a black hole event horizon. The entire reason they are surrounded by
radiation is because getting into a black hole is nigh impossible. Particles of gas and
dust fall toward it and generally miss, unless they’re almost perfectly on target, and then fly
away, and some enter an orbital pattern. They spin around that star and have gained huge kinetic
energy from the fall, and ram into each other, this causes a slow formation of an accretion
disc and bits of matter occasionally falling in, and is really no different than a
planetary ring, except higher energy. Your spaceship is either going to bend its
trajectory a bit when passing that black hole, or simply enter an orbit of that black hole,
probably a highly elliptical one. And most likely the former, as we tend to assume interstellar
vessels are moving around 10% of light speed, if not, much more, and even a 10 solar mass black
hole only has an escape velocity of 7% of light speed at a distance equal to the radius of our
entire planet Earth, which is more than 20 times its own radius of 30 kilometers or 20 miles,
which is just absurdly tiny in space terms. Moreover, it’s important to understand what
actually happens as a ship hits a gravity well… which is to say, it falls and speeds up. This
doesn’t make it harder to get out, it’s just like rolling down a hill then rolling up another,
you have all that extra speed helping you on the climb, plus no air drag slowing you… though the
accretion disc could serve that role of brake too. Also, you can then boost with your
thrusters a bit to get out of that orbit, just like if you were around a planet.
This is how slingshot maneuvers and the Oberth Effect work, letting a ship gain
speed moving around a massive object. If you dally too long though, you will get slowed
down by passing gas and dust, and get beat-up on by high-energy radiation – which can also slow
you, and then you might fall in or be ripped to bits, but you might also use that local matter and
radiation to power your way out of the black hole, and they might be a good place to refuel at
or set up interstellar space station hubs like truck stops. See our episode: Colonizing
Black Holes for more discussion of that. And if living and working near a black hole bugs
you, remember that you are living even closer to a big ball of molten radioactive matter with
a thin crust floating on it that we live on. Black holes may end up as the interstellar
travelers’ best friend, allowing course corrections and gravitational slingshots that
could never be done around any other body, at interstellar speeds and without crashing into
them or burning up. Don’t get too close though, they are only mostly harmless. If you fall across
the event horizon of a black hole, you’re stuck in there, even if you survived the trip, as this
is specifically the distance at which light speed equals the escape velocity of the black hole…
though that event horizon moves relative to you, and you’ll never actually reach it as you fall. If
you had some way to move faster than light speed you might get out, though it should be noted
that many FTL concepts, like the Warp Drive, would still be stuck in there, as their cheat
method of crunching and expanding spacetime fore and aft is ineffective against the black
hole’s own gravitational warping of spacetime. Nothing goes faster than light speed
The notion that nothing in the Universe can go faster than light is uncomfortably at odds
with the issue that most of the galaxies we can see are now moving away from us faster than light
speed, and yet there’s no contradiction. What we really mean is that if you’re trying to jog along
and keep up with a photon of light, you’re going to lose, or at best keep-up with it if you’re
another massless particle. However, space expands, and we assume bits and pieces of new spacetime are
constantly emerging randomly everywhere, probably as tiny subatomic bits at the Planck Scale.
If you imagine a very long measuring tape where people are quickly splicing in new bits
of tape between its end points, then the rate those folks work and how many of them there are
is going to control how fast that tape expands, and as it expands, more people can fit in
there splicing even more tape. It will grow, and once it is long enough, those folks will
be expanding that tape faster than a sound wave could carry the voices of any of those
people down the line to the guys on the end who now have to run away faster than sound.
This just scales up in space to light speed and the galaxies on the other end of our
measuring tape aren’t doing any pulling. They aren’t moving locally at any high speed, but
they are moving away from us faster than light, and we only see them now because the light from
them reaching us left back when they were closer and moving away slower. The rate is roughly 7% of
light speed for every billion light years between you and an object currently, double or half that
distance, double or half that expansion rate. And again, nothing is moving in the Universe
faster than light speed, it’s just over far enough distance that expansion is so fast
that nothing moving at light speed could cover all the new space emerging between it and its
destination as quick as that space is forming. The Edge of The Universe is
13 Billion Light Years Away This means then that the effective edge of
the Universe is 13 billion light years away, since things expanding away from us at light
speed would presumably have been doing so since the Universe formed 13 Billions years ago.
And everything about that statement is wrong. First, the current estimate for the Age
of the Universe is 13.8 billion years, rounding comfortably to 14, but for
a while the estimate was closer to 13 and that number got rather stuck into
common discussion, we should say 14. When I was a kid, back in the 1980s, the estimates
were generally 7-20 billion years old, and you’d see 20 in a lot of the texts of the time, and
that narrowed to 9-14 billion years in the 1990s. That was calculated off Hubble Shift and we
were finding stars that might be much older than 9 billion years by then too. You’ve probably
heard of stars estimated to be older than our Universe but almost all of that comes from having
stars with plus or minus a couple billion years on their age having their upper margin fall over
those same wide-margin of potential universe ages. Stars formed before the first billion years of
the Universe had passed. So, if your estimate is saying the Universe is 13-14 billion
years old and you’ve got a star calculating as 12-14 billion years old, there’s no real
implication you have a pre-Universe star there. However if light from such a star, one made just
after the Universe formed and 13 billion years ago, were to be detected today it would mean
it was 13 billion years old and that’s usually how astronomers will describe it. The photon
doesn’t have any sort of clock on it of course, but the longer and further it has traveled, the
more red-shifted it is, and we can make pretty good guesses off it and its companions as to what
wavelength it started off at, to see how much it red-shifted and thus get that age. It doesn’t mean
it left that star from 13 billion light years away though or that it’s that far away now.
That photon covered that much distance, but most of that distance didn’t exist when it
started toward us, and much of it emerged behind it afterward too, in terms of discussing how far
a star or galaxy is from us now, at this moment. And if we wanted to send a reply or ship to that
star or galaxy, it would be even further away and moving even faster away. Back when it left, that
star was probably less than a billion light years from where we were then, not that Earth existed
at that time, and now if we could just freeze everything, it would be around 45 billion light
years away, and the return message would take 45 billion years to reach that, again if we froze
universal expansion. But since we can’t, at least with current technology, if we tried to send a
signal to that spot, it would never reach it, as it is currently traveling away from us at
somewhere around 7 times the speed of light. The Universe has no Edge
What we usually call the edge of the Universe is the CMB or cosmic Microwave background radiation.
This is because the further back, or out you look, the more red-shifted everything is till it
gets kind of dark because there were no stars or galaxies yet, then we get to a period that’s
fairly high infrared because the Universe was still a pretty dense and warm place, and if you
go back a little further you reach a place where it’s dense and warm enough to resemble the light
from stars. Just a very hot plasma mostly made of hydrogen. It was even denser and brighter before
then but we can’t see there because light emitted from then constantly scattered and absorbed rather
than traveling very far before hitting something. There’s a critical point where things expanded
and cooled enough that hydrogen shifted to a less absorptive state and things were just
spread out more, and less likely to scatter, and this was about 380,000 years after the Big
Bang. This Surface of Last Scatter is as far as we can see with anything electromagnetic and thus
it gets dubbed the edge of the Universe a lot, and 380,000 years is very tiny compared to several
billion, so it’s close enough to the Big Bang, but if we ever get better at detecting
neutrinos we could probably look all the way back to the first minutes after the Big Bang.
And this edge is only in a temporal sense. We have no idea where or if the Universe has an edge,
only that we could never reach it without a faster-than-light spaceship, assuming space isn’t
infinite. Some folks would say that there’s no space beyond that edge. That might be the case,
but there’s no evidence for that. It’s one of those examples where folks are speculating and
extrapolating off mathematical models and logic, not data, and that’s not really science anymore.
It is entirely possible the big bang is merely a local event in a wider Universe or that the
Universe big-banged but was already infinite when it did so. We examined this more in our episodes
on the Big Rip and the Edge of the Universe. The Universe has no center
One of the governing principles of modern physics since Isaac Newton’s day was that the Universe
has no meaningful center and that we certainly are not the center itself. That is 100% at odds
with observable data incidentally. As we discussed a moment ago, we can see equally far back and out
in every direction till we hit a wall of cosmic microwave background radiation, that surface of
last scatter. This is literally a spherical shell around our planet that is expanding constantly
out from us showing ever more redshifted photons from evermore slightly further away.
We aren’t the Center of the Universe Since we can see equally in all directions back
to the Surface of Last Scatter, the default interpretation of that is that Earth is the Center
of the Universe, that is what the science says. We choose, from habit and logical extrapolation, to
assume that the Universe keeps going a long way beyond that and that either it is infinite, in
which case a center arguably doesn’t mean much, or if it is a big sphere, it’s one in which
we probably are of no place of specific note, and there may be places in the wider universe
where folks can’t see beyond a certain distance in one direction, or it may be that things curve back
on themselves, like the surface of a sphere such as Earth, or maybe the Universe is the surface
of an expanding 4D sphere, though probably not, or donut, or like walking off the edge of an old
video game and popping back in the other side. Key thing: We don’t actually know, but we got in
the habit of assuming ourselves no place special back in Newton and Copernicus’ day, and that was
very cosmologically and philosophically important to them at the time. Humanity and Earth are merely
mediocre and not special examples of anything, and that’s essentially the default opinion
of science, and perhaps ironically it is an opinion that is not scientific itself. It’s
merely a speculation, albeit a very sound one based on logic, but not physical data. It’s fairly
important though to be mindful of blinders because we discuss the Fermi Paradox a lot on this
show and the default view from the available evidence is that there are no detectable alien
civilizations, and that they probably don’t exist anywhere near us even on the galactic scale.
This is essentially the entire paradox, because if we’re not special and we’re not the
center of the Universe, it should be absurd to approach contemplating the Universe from that
perspective. It is probably no better an idea to assume Earth and humanity are tiny, mundane
dots on the cosmological scale, a pale blue dot, as to assume we’re the shining center of creation,
but more importantly we have a historic scientific basis for saying humanity isn’t central that
is improperly conflating our physical location with our metaphysical importance, and it’s rather
baked-into our thinking. It might be right too, but let’s poke at that notion a bit.
Earth Orbits the Sun To shift back home to Earth, we can continue that
notion of us not being the center of the universe by pointing out that the Earth doesn’t actually
orbit the Sun, nor does the moon orbit Earth, and nor is the Sun in any way the center of
our galaxy. Orbits occur based on all the mass in play in an area, and in our solar system
99.8% of that is in the Sun, 0.1% is Jupiter, and the other 0.1% is everything else, but mostly
Saturn. How in play stuff is at any moment is based on its distance too. It can be seen as
a quibble but if we’re contemplating life on other worlds, and how our early understanding of
the Heliocentric Model and Copernican Mediocrity Principle altered our worldview and philosophy
of science, we need to be mindful that other places aren’t going t2o see it that way.
Life that evolved on a planet around a close binary star system is in a good position
to spot that, those stars seem to orbit something themselves, that they cannot see, and
one can speculate how that might be impacting their early philosophy and religions. For our
near term purposes, we really need to finish getting away from the notion that Earth and all
the other planets circle the center of our sun, rather than orbit elliptically, as it
results in a confused view of things. Of course being aware the earth orbits
elliptically can cause confusion too, as folks often think Earth is close to the Sun
in Summer. In truth the seasons have virtually nothing to do with how close or far Earth is from
the Sun at any given moment, and Perihelion – when we’re closest to the Sun – takes place in Early
January, and early July, the height of summer, at least for the Northern Hemisphere, is our
aphelion, our furthest distance from the sun. Earth’s orbit is fairly circular as these things
go, and we define its normal distance from the Sun as 1 astronomical Unit or AU, but it gets as close
as .983 AU at Perihelion and 1.017 AU at Aphelion. That’s 3.5% further out than when closest, which
also gets 7% more sunlight than when furthest. This is hardly trivial, it’s just dwarfed
by the effect of axial tilt. Other planets with greater eccentricities – which is most of
them – would likely have a weather and seasonal cycle strongly affected by that eccentricity,
and even tidally locked planets around dimmer red stars can have significant seasons as a
result of that eccentricity, and made all the more weird by them potentially having orbital
years a few months or even weeks or days long. Speaking of Red Dwarfs though, we often hear
our Sun called a fiery yellow dwarf and that’s really wrong in every respect. To our eyes it
definitely has that golden shade but all stars are white light sources with a peak wavelength
of radiation, and our sun’s peak is a blue-ish green. Alternatively most of the photons coming
off of it are actually in the infrared. Indeed most stars emit the majority of their light in
the infrared range of the spectrum we can’t see, as did the typical incandescent light bulb. And
even the dimmest and coolest red dwarf is still as white a light as those old bulbs were. This isn’t
surprising as most stars are red dwarfs, though again, they don’t look red at all, and the entire
cataloging process is basically a flawed one of it being much easier to see big, bright stars.
The Copernican or Mediocrity Principle failed us there, we saw the abnormal giants most, brighter
than our own sun, not the normal stars, most of which are tiny and dim compared to our own.
A star’s visibility over distance is based off of its brightness, diminishing with the
inverse square of that distance, so one that’s a hundred times brighter is visible 10 times
further away. However, space is 3-dimensional, so that same volume of space contains 10-cubed
or a thousand times as many stars. Meaning that our early observation of the universe
contained virtually nothing but giants, and very few stars even as dim as our Sun, which
is bigger than 95% of all stars and 10,000 times brighter than the dimmest red dwarf, yet there are
stars a million times brighter than our own Sun. Needless to say, the Sun is not in any way on
fire either. While oxygen is the third most common substance on the Sun, there are no molecules;
everything is glowing hot plasma, cooling itself off by radiating waste heat as sunlight, and
fusion occurs deep below in the core, and very slowly too. Your typical ton of solar core matter
emits about enough power to run a light bulb, it’s just that there is so much of it and it
will keep doing so for billions of years before dying. And our Sun is short-lived compared to
most. It will live only 10 billion-ish years and the overwhelming majority of stars that ever
formed thus far in our Universe are still alive and kicking. Of the half a trillion or so stars
in this galaxy, perhaps 10 billion have become white dwarfs, just a couple percent, and only
a tenth of that, perhaps a billion total have gone supernova and become neutron stars, and
only about a tenth of that became black holes. Of course our Sun will die someday and this is
part of why we talk about wanting to travel to the stars and colonizing other worlds, and this takes
us to our penultimate misconception for today, that time on spaceships runs much, much slower.
Now, this isn’t wrong but there is a tendency whenever we see discussion of spaceships that
don’t have FTL for us to say they’re moving nearly at light speed, but the reality is that
in a No-FTL Universe, you aren’t likely to be plowing through space at 99.9% of light speed. The
energy needed for that, even ignoring practical engineering and the rocket equation, is literally
2000 times what it would take to move at 10% of light speed. And at 10% of light speed, your clock
is only moving half a percent slower than normal, or about 7 minutes a day or 6 months a century,
and at 1% light speed, it’s only 4 seconds a day that you’re saving, 26 minutes a year. That’s not
really letting you sneak away from the Grim Reaper by slowly crawling forward in time, and even at
99.9% of light speed, your clock is only moving 20 times slower than normal. You don’t even get down
to half normal time flow till 87% of light speed. Faster is always better if you’ve got the
energy and ability to do it, but when it comes to trying to escape local time, instead of
using more energy than the entire modern planetary economy uses in a whole year to accelerate
one person to a high time dilation rate, why not use that same energy to power that economy
and all its research labs and crack the secret of freezing and restoring people from Cryo? Or
maybe even some advanced type of stasis field? In the end, even though our Sun is
one of the shorter lived ones and stars will keep forming and living
for many trillions of years to come, they do eventually stop forming naturally,
and that takes us to our final misconception, that the Universe Ends when those last stars
do, and this is a dual misconception because it would seem very unlikely any natural stars will
even form in our galaxy a billion years from now, simply because a vast galactic civilization
isn’t likely to let them form. Artificial fusion, energy by dumping matter down black holes,
or by the slow evaporation of black holes, or even by vacuum energy, are all plausibly on
the table as superior ways to keep the lights on for your stellar empire than by actual
starlight. And that doesn’t even contemplate higher Clarketech options, which they would
have had billions of years to research before the cosmological event horizon sweeps away all
the stars from sight that you haven’t colonized. Indeed, as we saw in our civilization at
the End of Time Series, that time after the stars all burn out and all is swallowed
in darkness might be a far brighter, longer, and more populated era of civilization
than all those which came before combined. There are still so many things we don’t know about
the Universe, and likely many other misconceptions we have about it, but hopefully one of those will
turn out to be that in the end all must rundown and die from entropy, and that it will turn out
that the clock can be wound back up, or that the sum total of reality is far bigger than even
the seemingly endless enormity of our Universe. So it’s the end of another school year
and for a lot of folks it’s a time of transition in life.. we’re just not sure where
that’s supposed to be. I didn’t find my niche till I was in my 30s and these days there
really is no one-size-fits-all approach to pursuing or creating your dream job. To
find your niche, and to take advantage of the opportunities when they come up,
you need to explore and acquire skills. For me, when it came to making this channel a
reality, not just an occasional amateur hobby, that involved having to learn everything from
graphic design to marketing, how to edit audio, how to film on camera, how to do
animations, improving my writing, and many more. It was very daunting, but it was,
and is, doable, especially with a good partner, like Skillshare, and their community of
learners. Skillshare is a great resource for quality videos on those topics and many more, but
one that I’d particularly recommend is Danielle Krysa’s “Creative Breakthrough: 8 Exercises to
Power Your Creativity, Confidence & Career”. This channel has a lot very smart and creative
people on it, where coming up with a good idea isn’t the problem, it’s that roadmapping
to developing it into a success that is, and believing that you can actually do it.
Starting with the “Power of Aha Moments”, her videos on Skillshare help explore how to
move from that basic idea into the something more formed and practical. Along with how to manage
your creative talent to keep your confidence high, banish blocks and silence self-doubts.
Maybe you want to start a business or write a novel or develop a game or become a youtuber or
podcaster. Maybe you just want to learn to paint or take a better photo, no goal is too small.
Skillshare can even help you find more time for your goals by helping you with productivity and
time management, for which I’d highly recommend the videos there by my friend, Thomas Frank.
Take control of your future and make it a reality, and let SKillshare help you, try them out
today by using the link in this episode’s description. The first 1,000 people to use the
link will get a 1 month free trial of Skillshare. So we normally have our livestream Q&A the
last weekend of every month but I will be down in Frisco, Texas that weekend to help host the
International Space Development Conference, so the plan is to have the livestream next weekend,
Sunday May 21st, but I’m also going in for some minor surgery on my nose and tongue earlier that
week, so we might need to cancel and I’ll probably sound a bit different. Hopefully in a good way, as
that’s rather the point, it’s supposed to be the next step in fixing my speech impediment, but
the livestream is at the tail end of the main recovery time for the surgery so I might not know
till the last minute if I’m good to do the show. Speaking of the show this weekend is our Scifi
Sunday episode, on May 14th, where we explore the grim realities of super-urbanized Hive
Worlds, then we’ll have its companion episode, Hungry Aliens, on May 18th. And in two weeks,
on May 25th, we’ll talk about how to bend space and warp reality. Then we’ll head into June to
look at exploring and settling the Kuiper Belt. If you’d like to get alerts when those and other
episodes come out, make sure to hit the like, subscribe, and notification buttons. You
can also help support the show on Patreon, and if you want to donate and help in other ways,
you can see those options by visiting our website, IsaacArthur.net. You can also catch all
of SFIA’s episodes early and ad free on our streaming service, Nebula, along with hours
of bonus content, at go.nebula.tv/isaacarthur. As always, thanks for watching,
and have a Great Week!
