Kind: captions
Language: en
the following is a conversation with
Alex filipenko an astrophysicist and
professor of astronomy from Berkeley he
was a member of both the Supernova
cosmology project and the high Supernova
search team which used observations of
the extra Galactic Supernova to discover
that the universe is accelerating and
that this implies the existence of dark
energy this discovery resulted in the
2011 nobba prize for physics outside of
his groundbreak can research he is a
great science communicator and is one of
the most widely admired Educators in the
world I really enjoyed this conversation
and I'm sure Alex will be back again in
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at Lex fredman and now here's my
conversation with Alex
filipenko let's start by talking about
the biggest possible thing the universe
sure will the universe expand forever or
collapse on itself well you know that's
a great question that's one of the big
questions of cosmology and of course we
have evidence that the matter density is
sufficiently low that the universe will
expand forever but not only that there's
this weird repulsive effect we call it
dark energy for want of a better term
and it appears to be accelerating the
expansion of the universe so if that
continues the universe will expand
forever but it need not necessarily
continue it could reverse sign in which
case the universe could in principle
collapse at some point in the Far Far
Future so like in terms of investment
advice if you were to give me and then
to bet all my money on one or the other
where did does your intuition currently
lie well right now I would say that it
would expand forever because I think
that the dark energy is likely to be
just Quantum fluctuations of the vacuum
the vacuum Zero Energy state is not a
state of zero energy that is the ground
state is a a state of some elevated
energy which has a repulsive effect to
it and that will never go away because
it's not something that changes with
time so if the universe is accelerating
now it will forever continue to do so
and yet I mean you're so effortlessly
mentioned Dark Energy do we have any
understanding of of what the heck that
thing is well not really but we're
getting progressively better
observational constraints so you know
different theories of what it might be
predict different sorts of behavior for
the evolution of the universe and we've
been measuring the evolution of the
universe now and the data appear to
agree with the predictions of a con
density vacuum energy a z Point
Energy but one can't prove that that's
what it is because one would have to
show that the numbers that the measured
numbers agree with the predictions to an
arbitrary number of decimal places and
of course even if you've got 8 9 10 12
decimal places what if in the 13th one
the measurements significantly differ
from the prediction then the dark energy
isn't this vacuum State uh ground state
energy of the of the vacuum and so then
it could be some sort of a a field some
sort of a new energy a little bit like
like light like electromagnetism but
very different from light that fills
space and that type of energy could in
principle change in the distant future
it could become gravitationally
attractive for all we know there is a
historical precedent to that and that is
that the inflation with which the
universe began when the universe was
just a tiny blink of an of an eye old a
trillionth of a trillionth of a
trillionth of a second you know the
universe went whoosh it exponentially
expanded that dark energy likee
substance we call it the inflaton that
which inflated the universe later
decayed into more or less normal
gravitationally attractive matter so the
exponential early expansion of the
universe did transition to a
deceleration which then dominated the
universe for about 9 billion years and
now this small amount of dark
energy started causing an acceleration
about five billion years ago and whether
that will continue or not is something
that we'd like to answer but I don't
know that we will anytime soon so there
could be this interesting field that we
don't yet understand that's morphing
over time that's changing the way the
universe is is expanding I mean it it's
funny that you were thinking through
this rigorously like an
experimentalist yeah but the what about
like the fundamental physics of dark
energy is there any
understanding of uh what the heck it is
or is or is this the kind of uh the the
god of the gaps or the field of the gaps
uh so like it there must be something
there because of what we're observing
I'm very much a person who believes that
there's all always a cause you know
there there are no um
miracles of a supernatural nature okay
uh so I mean there are two broad
categories either it's the vacuum Zero
Point Energy or it's some sort of a a
new energy field that pervades the
Universe the latter could change with
time the former the vacuum energy cannot
right so if it turns out that it's one
of these new fields and there many many
possibilities they go by the name of you
know quintessence and things like that
but there are many categories of those
sorts of fields we try with data to rule
them out by comparing the actual
measurements with the predictions and
some have been ruled out but many many
others remain to be tested and the data
just have to become a lot better before
we can rule out most of them and become
reasonably convinced
that this is a vacuum energy so there is
hypotheses for different fields like
with names and stuff like that yeah yeah
you know generically quintessence like
the Aristotelian fifth Essence but there
are many many versions of quintessence
there's K Essence there's even ideas
that you know this isn't something from
within this dark energy but rather there
are a bunch of say bubble universes
surrounding our universe and this whole
idea of the Multiverse is not some crazy
Mad Men type idea anymore it's you know
real card carrying physicists are
seriously considering this possibility
of a Multiverse and some types of
multiverses could have you know a bunch
of bubbles on the outside which
gravitationally act outward on our
bubble because gravity or gravitons the
the quantum particle that is thought to
carry gravity is is thought to Traverse
the bulk the space between these
different little bubble membranes and
stuff and so it's conceivable that these
other verus are pulling outward on us
that's not a favored explanation right
now but but really nothing has been
ruled out no class of models has been
ruled out completely certain examples
within classes of models have been ruled
out but in general I think we still have
really a lot to learn about what's
causing this observed acceleration of
the expansion of the universe be it dark
energy or some forces from the outside
or or perhaps you know I guess it's
conceivable that and sometimes I wake up
in the middle of the night screaming the
dark energy that which causes the
acceleration and dark matter that which
causes galaxies and clusters of galaxies
to be bound gravitationally even though
there's not enough visible matter to do
so maybe these are our 20th and 21st
century toic epicycles so toy had a
geocentric and Aristotelian view of the
world everything goes around Earth but
in order to explain the backward motion
of planets Among the Stars that happens
every year or two or sometimes several
times a year for Mercury and Venus you
needed the planets to go around in
little circles called epicycles which
themselves then went around Earth yes
and in this in this part of the epicycle
where the planet is going in the
direction opposite to the direction of
the overall epicycle it can appear in
projection to be going backward Among
the Stars socaled retrograde motion and
it was a brilliant mathematical scheme
in fact he could have added epicycles on
top of
epicycles and reproduce The observed
positions of planets to arbitrary
accuracy yeah and this is really the
beginning of what we now call forier
analysis right any periodic function can
be represented by a sum of signs and Co
signs of different periods amplitudes
and phases so it could have worked
arbitrarily well but other data you know
show that in fact Earth is going around
the Sun um so are dark energy and dark
matter just these Band-Aids that we now
have to try to explain the data but
they're just completely wrong that
that's a possibility as well and as a
scientist I have to be open to that
possibility as an open-minded scientist
how do you how do you put yourself in
the mindset of somebody that or majority
of the scientific Community or majority
of people believe that the Earth
everything rotates around
Earth how do you put yourself in that
mindset and then take a leap to uh
propose a model that the sun is in fact
at the center of this the solar system
sure I mean so that puts us back in the
shoes of cernus right 500 years ago
where he had this philosophical
preference for the sun being the
dominant body in what we now call the
solar system the observational evidence
in terms of the measured positions of
planets was not better explained by the
heliocentric Sun centered system it's
just that you know cernus saw that the
sun is the source of all our light and
heat oh wow
and he had you know he he knew from
other studies that it's it's far away so
the fact that it appears as big as the
moon means it's actually way way bigger
because even at that time it was known
that the sun is much farther away than
the moon so um you know he just felt wow
it's big it's bright what if it's the
central thing but the observed positions
of planets at the time in the early to
mid 16th century under the heliocentric
system was not a better match at least
not a significantly better match than
tmy system which was quite accurate and
lasted 1500 years yeah
yeah that's so fascinating to think that
the philosophical predispositions that
you bring to the table are essent so
like you have to have a young person
come along that has a weird infatuation
with the son yeah that like almost
philosophically is like however their
upbringing is they're more ready for
whatever the more the simpler answer is
right oh that's um it's kind of sad it's
uh sad from an individual descendant of
ape perspective because then that means
like me like you as a
scientist you're stuck with whatever the
heck philosophies you brought to the
table you might be almost completely
unable to to think outside this
particular box you've built right this
is why I'm saying that you know as an
objective scientist one needs needs to
have an open mind to Crazy sounding new
ideas and you know even cernus was very
much a man of his time and dedicated his
work to the pope he still used circular
orbits the Sun was a little bit off
center it turns out and a slightly
off-center Circle looks like a slightly
eccentric elliptical orbit so then when
Kepler in fact showed that the orbits
are actually in general ellipses not
circles the reason that you know he
needed tuob bra's really great data to
show that distinction was that a
slightly off-center circle is not much
different from a slightly eccentric
ellipse and so there wasn't much
difference between Kepler's View and uh
kernus is View and and Kepler needed the
better data uh tuo's toob bra's data and
so that's again a great example of of of
science
and OBS observations and experiments
working together with hypotheses and
they they kind of bounce off each other
they play off of each other and you
continually need more observations and
it wasn't until Galileo's work uh around
1610 that actual evidence for the
heliocentric hypothesis emerged it came
in the form of Venus the planet Venus
going through all of the possible phases
from new to Crescent to to quarter to
gibbus to full to waning gibbus third
quarter waning crescent and then new
again it turns out in the toic system
with Venus between Earth and the Sun but
always roughly in the direction of the
sun you could only get the new and
Cresent phases of Venus but the
observations showed a full set of phases
and moreover when Venus was gibbus or
full that meant it was on the far side
of the Sun that meant it was farther
from Earth than when it's Crescent so it
should appear smaller and indeed it did
so that was a that was you know the nail
and the coffin in a sense and then you
know Galileo's other great observation
was that Jupiter has moons going around
it the four Galilean satellites and even
though Jupiter moves through space so
too do the moons go with it so first of
all Earth is not the only thing that has
other things going around it and
secondly Earth could be moving as
Jupiter does and you know
things would move with with it we we
wouldn't fly off the surface and our
moon wouldn't be left behind and all
this kind of stuff so that was a a big
breakthrough as well but it wasn't as
definitive in my opinion as the phases
of Venus perhaps I'm revealing my
ignorance but I didn't realize how much
data they were working with yeah so
there's uh so it wasn't
Einstein or Freud thinking in theories
it was a lot of data and you're playing
with it and seeing how to make sense of
it so isn't it it isn't just coming up
with completely abstract thought
experiments yeah it's looking at the
data sure and you Newton's great work
right the prinkipia it was based in part
on Galileo's observations of balls
rolling down inclined planes supposedly
fall falling off the Leaning Tower of
Pisa but that's probably apocryphal in
any case you know um the the the
Inquisition actually did or the R
Catholic Church uh did did history a
favor not that I'm condoning them but
they placed Galileo under house arrest
yeah and that gave Galileo time to
publish to assemble and publish the
results of his experiments that he had
done decades earlier it's not clear he
would have had time to do that you know
had he not been under house arrest and
so Newton of course Very Much used
Galileo's
observations let me ask uh the old
Russian overly philosophical question
about death so we're talking about the
expanding Universe sure how do you think
human civilization will come to an end
if we avoid the uh the near-term issues
we're
having uh will it be our sun burning out
will it be comets okay will it be uh
what is it oh do you think we we have a
shot at reaching the the heat death of
the universe yeah yeah so we're going to
leave out the
anthropogenic uhle causes of our
potential destruction yes which I
actually think are greater than the
celestial uh causes so um so if we get
lucky yeah if we get and intelligent I
don't know yeah so no way will we as
humans reach the heat death of the
Universe I mean it's conceivable that uh
machines which I think will be our
evolutionary descendants might reach
that although even they will have less
and less energy with which to work as
time progresses because eventually even
the lowest mass stars burn out although
it takes them trillions of years to do
so um so the point is is that certainly
on Earth uh there are other Celestial
threats existential threats comets
exploding Stars the sun burning out so
we will definitely need to move away
away from our solar system to other
solar systems and then you know the
question is can they keep on propagating
to other planetary systems sufficiently
long um in our own solar system the sun
burning out is is not the the immediate
existential threat um that'll happen in
about you know five billion years when
it becomes a red giant although I should
hasten to add that within the next one
or two billion years years the sun will
have brightened enough that unless
they compensatory atmospheric changes
the oceans will will evaporate away you
know and and you need much less carbon
dioxide for the temperatures to be
maintained roughly at their present
temperature and plants wouldn't like
that very much so you can't lower the
carbon dioxide content too much so so
within one or two billion years probably
the oceans will evaporate away yeah but
on a sooner time scale than that
I would say an asteroid Collision
leading to a potential mass extinction
or at least an Extinction of complex
beings such as ourselves that require
quite special conditions unlike
cockroaches and amibas you know to
survive um you know one of
these civilization changing asteroids is
only one kilometer or so in diameter and
bigger and a true mass extinction event
is 10 kilometers or larger now it's true
that we can find and track the orbits of
asteroids that might be headed toward
Earth and if we find them 50 or 100
years before they impact us then clever
applied physicists and Engineers can
figure out ways to deflect them but at
some point you know some Comet will come
in from the deep freeze of the solar
system and there we have very little
warning months to a to a year what's the
Deep Freeze sorry oh the Deep Freeze is
sort of out Beyond Neptune there's this
thing called the Kyper belt M and it
consists of a bunch of you know dirty
ice balls or icy dirt balls it's the
source of the Comets that occasionally
come close to the Sun and then there's a
even bigger area called the scattered
disc which is sort of a big doughnut
surrounding the solar system way out
there from which other comets come and
then there's the orc Cloud
WT after uh Yan ort a Dutch
astrophysicist and it's the better part
of a lightyear away from the Sun so a
good fraction of the distance to the
nearest star but that's like a trillion
or 10
trillion comet-like objects that
occasionally get disturbed by a passing
star or whatever and most of them go
flying out of the solar system but some
go toward the Sun and they they come in
with little warning you know by the time
we can see them they're only a year or
two away from us and moreover not only
is it hard to determine their
trajectories sufficiently accurately to
know whether they'll hit a tiny thing
like Earth but outgassing from the comet
of um gases you know when the IES
sublimate that
outgassing can change the trajectory
just because of conservation of momentum
right it's the rocket effect gases go
out in One Direction the object moves in
the other direction and so since we
can't predict how much outgassing there
will be and in exactly what direction
because these things are tumbling and
rotating and stuff it's hard to predict
the trajectory with sufficient accuracy
to know that it will hit and you
certainly don't want to deflect a comet
that would have missed but you thought
it was going to hit and end up having it
hit that would be like the ultimate
Charlie Brown you know goat instead of
trying to be the hero right he ended up
being the goat what would you uh what
would you do
if it seemed like in a matter of months
that there is some nonzero prob ility
maybe a high probability that there will
be a collision so from a scientific
perspective from an engineering
perspective I imagine you would actually
be in the room of people deciding what
to do what uh yeah philosophically too
it's a tough one right because if you
only have a few months that's not much
time in which to deflect it early
detection and and um early action or key
because when it's far away you only have
to deflect it by a tiny little angle
yeah and then by a time it reaches us
the perpendicular motion is big enough
to you know to to Miss Earth all you
need is one radius or or one diameter of
the earth
right that actually means that all you
would need to do is slow it down so it
arrives four minutes later or speed it
up so it arrives four minutes earlier
and Earth will have moved through one
radius in in that time so it doesn't
take much but you can imagine if a thing
is about to hit you you you have to
deflect at 90 degrees or more right you
know and you don't have much time to do
so and you have to slow it down or speed
it up a lot if that's what you're trying
to do to it and so decades is sufficient
time but months is not sufficient time
so at that point I would think the the
name of the game would be to try to
predict where it would
hit and if it's in a heavily populated
region try to
try to start an orderly evacuation
perhaps but you know that might cause
just so much Panic that I'm how would
you do it with New York City or or Los
Angeles or something like that right I
might have I might have a different
opinion a year ago I'm uh a bit U
disheartened by you know in the movies
the um there's always extreme competence
from the
government competence yeah competence
right but we expect extreme incompetence
if anything right yes now so I'm quite
disappointed but sort of from a medical
perspective I think you're saying there
in a scientific one it's almost better
to get better and better maybe
telescopes and data collection to be
able to predict the movement of these
things or like come up with totally new
technologies like you can imagine
actually sending out like probes out
there to be able to sort of almost have
little finger sensors throughout our
solar system to be able to detect stuff
well that's right yeah monitoring the
asteroid belt is very important and 99%
of the so-called neear objects
ultimately come from the asteroid belt
and so there we can track the
trajectories and even if there's you
know a close encounter between two
asteroids which deflects one of them
toward Earth it's unlikely to be on a
collision course with Earth in the
immediate future it's more like you know
tens of years so that gives us time but
we would need to improve our ability to
detect the objects that come in from a
great distance unfortunately those are
are much rarer the the Comets come in
you know 1% of the collisions perhaps
are with comets that come in without any
warning hardly and
so so that might be more like you know a
billion or two billion years before one
of those hits us um so maybe we have to
worry about the sun getting brighter on
that time scale I mean there's the
possibility that a star will explode
near us in the next couple of billion
years but over the course of the history
of life on Earth the estimates are
that
maybe only one of the mass extinctions
you know was caused by a star blowing up
in particular a special kind called a
Gamay burst and the I think it's the
oriv I
solarian uh saluan or divis saluan
Extinction 420 or so 440 million years
ago that is speculated to have come from
one of these particular types of
exploding Stars called Gamay bursts but
even there the the evidence is
circumstantial so those kinds of
existential threats are are reasonably
rare the greater danger I think is
civilization changing events where it's
a much smaller asteroid uh which those
are hard harder to detect or or a giant
solar
flare that shorts out the Grid in all of
North America let's say now you know
astronomers are monitoring the sun 247
with various satellites and we can tell
when there's a a flare or a coronal mass
ejection and we can tell that in a day
or two a giant bundle of energetic
particles will arrive and twang the
magnetic field of Earth and send all
kinds of currents through long-distance
power lines and that's what shorts out
the Transformers and Transformers are
you know expensive and and hard to
replace and hard to transport and all
that kind of stuff
so if we can warn the power companies
and they can shut down the grid before
the big bundle of particle hits then we
will have mitigated much of this now for
a big enough bundle of particles you can
get short circuits even over small
distance scales so not everything will
be saved but at least the whole grid
might not go out so again you know
astronomers I like to say support your
local astronomer they may help someday
save Humanity by telling the power
companies to shut down the grid finding
the asteroid 50 or 100 years before it
hits then having clever physicists and
Engineers deflect it so many of these
Cosmic threats Cosmic existential
threats we can actually
predict and do something about or
observe before they hit and do something
about so it's it's terrifying to think
that people would listen to this
conversation it's like when you listen
to Bill Gates talk about pandemics and
his Ted Talk a few years ago yeah and
realizing we should have supported our
local astronomer more well I don't know
whether it's more because that's I said
I actually think uh human induced
threats or things that occur naturally
on Earth either a natural pandemic or
perhaps you know a bioengineering type
pandemic or you know something like a
super volcano right um there was one
event Toba I think it was 70 plus
thousand years ago that that caused a
gigantic decrease in temperatures on
Earth because it sends up it sent up so
much soot that it blocked the sun right
it's the nuclear winter type disaster
scenario that some people including Carl
Sean talked about decades ago but we can
see in the history of volcanic eruptions
even more recently in the 19th century
Tambora and other ones you look at the
record and you see rather large dips in
temperature associated with massive
volcanic eruptions well these super
volcanoes one of which by the way exists
under Yellowstone you know in the
central us I mean it's not just it's not
just one or two states it's a it's a
gigantic region and there's controversy
as to whether it's likely to blow any
time in the next 100,000 years or so but
that would be perhaps not a mass
extinction because you really need to or
or perhaps not a complete existential
threat because you have to get rid of
sort of the very last humans for that
but but at least getting rid of um you
know killing off so many humans truly
billions and billions of humans the one
there have been
ones tens of thousands of years ago
including this one um Toba I think it's
called where it's estimated that the
human population was down to 10,000 or
5,000 individuals something like that
right if you have a 15 degree drop in
temperature over quite a short time it's
not clear that even with today's
advanced technology we would be able to
adequately respond at least for the vast
majority of people maybe some would be
in these underground caves where you'd
keep the president and a bunch of other
important people you know but the the
typical person is not going to be prot
protected when when all of Agriculture
is is cut off right and when it could be
hundreds of millions or billions of
people yeah starving to death exactly
that's right they don't all die
immediately but they use up their
supplies or again this electrical grid
first toilet paper there you go stash
that toilet paper you know um or the
electrical grid I mean imagine North
America without power for a year right I
mean we've become so dependent we're no
longer the cave people
they would do just fine right what do
they care about the electrical grid
right what do they care about
agriculture they're hunters and
gatherers but we now have become so used
to our way of life that the only real
survivors would be those rugged
individualists who live somewhere out in
the forest or in a cave somewhere
completely independent of anyone else
yeah I've recently I recommend it it's
totally new to me this kind of
survivalist uh folks but there's a a few
show there's a lot lot of shows of those
but I saw one on Netflix and I started
watching them and
there's they make a lot of sense they
they reveal to you how dependent we are
on all aspects of this beautiful systems
we human have built right and how
fragile they are incredibly fragile and
yeah this this whole conversation is
making me realize how lucky we are oh
we're we're incredibly lucky but we've
set ourselves up to be very very fragile
and we are intrinsically complex
biological creatures that except for the
fact that we have brains and Minds with
which we can you know try to prevent
some of these things or respond to them
we as a living organism require quite a
narrow set of conditions in order to
survive you know we're not cockroaches
we're not going to survive a nuclear war
so we're kind of there's this beautiful
dance between um we've been talking
about a astronomy that astronomy the
Stars like
inspires everybody and at the same time
there's this pragmatic aspect that we're
talking about and so I see space
exploration as the same kind of way that
it's uh reaching out to other planets
reaching out to the stars is this really
beautiful idea but if you listen to
somebody like uh Elon Musk he talks
about space exploration as very
pragmatic like we have to if we we have
to
be he has this ridiculous way of
sounding like an engineer about it which
is like it's obvious we need to become a
multiplanetary species if we were to
survive long term so maybe both
philosophically in terms of beauty and
in terms of practical what's your
thoughts on um space exploration on the
challenges of it on how much we should
be investing in it and on a personal
level like how excited you are about by
the possibility of going to Mars
colonizing Mars and maybe going outside
the solar system yeah you know great
question uh there's a lot to unpack
there of course you know humans are by
their very nature explorers Pioneers
they want to go out climb the next
Mountain see what's behind it um explore
the oan depths explore space this is our
destiny to go out there and and of
course from a pragmatic perspective yes
we need to um plant our seeds elsewhere
really because things could go wrong
here on Earth now some people
say that's that's an excuse to not take
care of our planet that well we say
we're elsewhere and so we don't have to
take good care of our planet no you know
we should take the best possible care of
our planet we should be cognizant of the
potential impact of what we're doing
nevertheless it's prudent to have us be
elsewhere as well so in that regard I
actually agree with Elon uh it'd be good
to be on Mars that would be yet another
place for us to from which to you know
explore further would that be a good
Next Step would you say well that's the
good it's a good next step I have happen
I happen to disagree with him as to how
quickly it will happen right I mean I
think he's very optimistic now you need
Visionary people like Elon to to get
people going and to inspire them I mean
look at the success he's had with
multiple companies uh so maybe he gives
this very optimistic timeline in order
to be inspirational to those who are who
are going out there and certainly his
Success With You know the rocket that is
reusable because it landed upright and
all that I mean you know what that
that's a GameChanger sort of like every
time you flew from San Francisco to Los
Angeles you discard the airplane right I
mean that's crazy right so that's a game
Cher but nevertheless the time scale
over which he thinks that there could be
a real thriving colony on Mars I think
is far too optimistic what's the biggest
challenges to you one is just getting
Rockets not Rockets but people out there
and two is the
colonization like what do you have
thoughts about this um challenges of
this kind of prospect yeah I haven't
thought about it in in great detail uh
other than recognizing that Mars is a
harsh environment yeah you don't have
much of an atmosphere there you've got
less than a percent of Earth's
atmosphere um so you you to build some
sort of a dome right away right and and
that that would take time you need to
melt the water that's in the permafrost
or have canals dug from which you
transport it from the from the polar ice
caps you know I I was reading recently
in terms of like what's the most
efficient source of nutrition for humans
that were to live on Mars and uh people
should look into this but it turns out
to be insects insects yeah yeah so you
want you want to build GI colony of
insects and just be eating insects have
a lot of protein right a lot of protein
and they're easy
to like you can think of them as farming
right but it's not going to be easy as
easy as growing a whole plot of potatoes
like in the movie The Martian you know
or something right it's not going to be
that easy but you know so there's
there's this thin atmosphere it's got
the wrong composition it's mostly carbon
dioxide there are these violent dust
storms the temperatures are generally
cold you know you'd need to do a lot of
things you need to terraform it
basically in order to make it nicely
livable without some Dome surrounding
you and if you and if you insist on a
dome well that's not going to house that
many people right you know well so let's
look let's look briefly then you know
we're looking for a new apartment to
move into so let's look outside the
solar system do you think you've you've
spoken about exoplanets as well do you
think there's um possible homes out
there for us uh outside of our solar
system there are lots and lots of homes
possible homes I mean they're there's a
planetary system around nearly every
Star you see in the sky and one in five
of those is thought to have a roughly
earth like Planet you know and that's a
relatively new yeah it's a new discovery
I mean that the Kepler satellite which
was flying around uh above Earth's
atmosphere was able to monitor the
brightness of stars with exquisite
detail and they could detect planets
crossing the line of sight between us
and the star thereby dimming its light
for a short time ever so slightly and
it's it's amazing so there are now
thousands and thousands of these
exoplanet candidates of which something
like 90% are probably genuine exoplanets
and you have to remember that only about
1% of stars have their planetary system
oriented Edge on to your line of sight
which is what you need for this Transit
method to work right some arbitrary
angle won't work and certainly
perpendicular uh to your line of sight
that is in the plane of the sky won't
work because the the the planet is
orbiting the star and never crossing
your line of sight so the fact that um
you know they
found planets orbiting about 1% of the
stars that they looked at in this field
of 150 plus thousand
stars they found planets around 1% you
then multiply by the inverse of 1% which
is you know right 1% is about how many
what the fraction of the of the stars
that have their planetary system
oriented the right way and that already
back of the envelope calculation tells
you that of order 50 to 100% of all
stars have planets okay and then they've
been finding these earthlike planets etc
etc so there are many potential homes
the problem is getting there okay so
then a typical bright star serus uh the
brightest star in the sky maybe not a
typical bright star but it's 8.7 light
years away okay so uh that's that means
the light took 8.7 years to reach us
we're seeing it as it was about nine
years ago okay so then you know you ask
how long would a rocket take to get
there at Earth's escape speed which is
11 kilometers per second okay and it
turns out it's about a quarter of a
million years okay now that's 10,000
Generations okay let's say a generation
of humans is 25 years right so you need
this colony of people that is able to
sustain itself all their food all their
waste disposal all their water all their
recycling of everything for 10,000
Generations they have to commit
themselves to living on this vehicle
right I just see it happening what I see
potentially happening if we avoid
self-destruction intentional or
unintentional here on Earth is that
machines will do it robots that can
essentially hibernate they don't need to
do much of anything for a long long time
as they're traveling and moreover if
some energetic charged particle some
Cosmic gray hits the circuitry it fixes
itself right machines can do this
uh I mean it it's a form of artificial
intelligence you just tell the thing fix
yourself basically and then when you
land on the on the planet start
producing copies of yourself initially
from materials that perhaps sent or you
just have a bunch of copies there and
then they set up you know factories with
which to do this I mean this is very
very futuristic but it's much more
feasible I think than sending Flesh and
Blood over Interstellar distances a
quarter of a million years to even the
nearest Stars you're subject to all
kinds of charged particles and radiation
you have to you know Shield yourself
really well that's by the way one of the
problems of going to Mars is that it's
not a three-day Journey like going to
the Moon you're out there for the better
part of a year or two and you're exposed
to lots of radiation you know which
typically doesn't do well with living
tissue right or living tissue doesn't do
well with the radiation okay and and the
hope is that the robots that AI systems
might be able to carry the carry
the the fire of Consciousness whatever
makes us humans yeah like a little drop
of whatever makes us humans so special
not to be too poetic about it but no but
I I like being poetic about it because
it's a it's an amazing question you know
is there something Beyond just the bits
the ones and zeros to us you know it's
an interesting question um I like to
think that there there isn't anything
and that how beautiful it is that our
thoughts our emotions our feelings our
compassion all come from these ones and
zeros right that to me actually is a a
beautiful thought and the idea that
machines silicon based life effectively
could be our natural evolutionary
descendants not from a DNA perspective
but they are our creations and they then
carry on that to me is a a beautiful
thought in some ways but others find it
to be a horrific thought right exciting
to you I it is exciting to me as well
yeah because to me from a purely an
engineering perspective it's I believe
it's impossible to create like
whatever systems we create that take
over the world it's impossible for me to
imagine that those systems will not
carry some aspect of what makes humans
beautiful yeah so like that a lot of
people have these kind of paperclip
ideas that will we bring will'll build
machines that are cold inside or
philosophers call them zombies you know
they're they're that
naturally the systems that will out
compete us on this Earth will be cold
and non
nonconscious not capable of all the
human emotions and empathy compassion
and love and hate every the the
beautiful uh mix of uh what makes us
human but to me intelligence requires
all of that so in order order to
outcompete humans you better be good at
the full picture right so artificial
general intelligence in my view
encompasses a lot of these attributes
that you just talked about yeah
curiosity inquisitiveness you know right
it might look very different than us
humans but you have some of the magic
but it'll but it'll also be much more
able to survive the onslaught of
existential threats that either we bring
upon ourselves or don't anticipate here
on Earth or that occasionally come from
Beyond and there's nothing much we can
do about a supernova explosion that just
suddenly you know goes off and and and
really if we want to move to other
planets outside our solar system I think
realistically that's a much better
option than thinking that humans will
actually make these gigantic Journeys
and you know then I do this calculation
from my class you know Einstein's
special theory of relativity says that
you can do it in a short amount of time
in your own frame of reference if you go
close to the speed of light but then you
bring in eal mc^2 and you figure out how
much energy it takes to get you
accelerated to close enough to the speed
of light to make the time scales short
in your own frame of reference and the
amount of energy is just unfathomable
right we can do it at the large hron
collider with with protons you know we
can accelerate them to
99.9999% of this speat of light but
that's just a proton we're gazillions of
protons okay and that doesn't even count
the rocket that would carry us the
payload and you would need to either
store the fuel in the rocket which then
requires even more mass for the rocket
or collect fuel along the way which you
know is difficult and so getting close
to the speed of light I think is not an
option either other than for a little
tiny thing like you know Yuri Milner and
others are thinking about this this star
shot project where they'll a little tiny
camera to Alpha centuri 4.2 light years
away they'll zip past it take a picture
of the exoplanets that we know orbit
that three or more star system and uh
say hello real quick say hello real
quickly and then send the images back to
us okay yeah so that that's a tiny
little thing right maybe you can
accelerate that to they're hoping 20% of
the speed of light with a whole bunch of
high-powered lasers aimed at it it's now
clear that other countries will allow us
to do that by the way but that's a very
forward looking thought I mean I very
much support the idea but there's a big
difference between sending a little tiny
camera and sending a payload of people
with equipment that could then mine the
um the resources on the exoplanet that
they reach and and then go forth and
multiply right well let's let's talk
about the big Galactic things and how we
might be able to leverage them to travel
fast I know this is a little bit science
fiction
but you know know uh ideas of wormholes
and yeah the ideas at the edge of black
holes that reveal to us that this fabric
of SpaceTime is
uh could be messed with yeah perhaps is
that at all an interesting thing for you
uh I mean in in your in looking out at
the universe and studying it as you have
is that also a possible like a dream for
you that we might be able to find Clues
how we can actually use it to improve
our transportation it's an interesting
thought I'm certainly excited by the
potential physics that suggest this kind
of faster than light travel effectively
or you know cutting the distance to make
it very very short through a wormhole or
something like that possible no well you
know col me not very imaginative but
based on today's knowledge of physics
which I realize you know people have
gone down that rabbit hole
you know aury ago Lord Kelvin one of the
greatest physicists of all time said
that all of fundamental physics is done
the rest is just engineering and guess
what then came special relativity
quantum physics general relativity how
wrong he was so let me not be another L
Lord Kelvin on the other hand I think we
know a lot more now about what we know
and what we don't know and what the
physical limitations are and to me most
of these schemes if not all of them seem
very far-fetched if not impossible so
travel through wormholes for example you
know it appears that for a non-rotating
black hole that's just a complete no-o
because the The Singularity is a
point-like singularity and you have to
reach it to Traverse the Wormhole and
you get squished by The Singularity okay
now for a rotating black hole it turns
out there is a way to pass through the
Event Horizon the boundary of the black
hole and avoid the singularity and go
out the other side or even Traverse the
the doughnut hole like singularity in
the case of a rotating black hole it's a
ring Singularity so there's actually two
theoretical ways you could get through a
rotating black hole or a Charged black
hole not that we expect charged black
holes to exist in nature because they
would quickly bring in the opposite
charge so as to neutralize themselves
but rotating black holes definitely
reality we we now have good evidence for
them do they have Travers ible wormholes
probably not because it's still the case
that when you go in you go in with so
much energy that it it it either
squeezes the Wormhole shut or you
encounter a whole bunch of incoming and
outgoing energy that vaporizes you it's
called the mass inflation instability
and it just sort of vaporizes you
nevertheless you know you could imagine
well you're in some vapor form but if
you make it through maybe you could you
know re form or something so it's still
information yeah it's still information
it's scrambled information but there's a
way maybe of bringing it back right but
then the thing that really bothers me is
that as soon as you have this
possibility of traversal of a wormhole
you have to come to grips with a
fundamental problem and that is that you
could come back to your Universe At A
Time prior to your leaving and you could
essentially prevent your grandparents
from meeting this is called the
grandfather Paradox right and if they
never met and if your parents were never
born and if you were never born how
would you have made the journey to
prevent the history from allowing you to
exist right it's it's a it's a causal
it's a violation of causality of cause
and effect now physicists such as myself
take causality violation very very
seriously we've never seen it you took a
stand yeah I mean you know I mean it's
one of these right Back to the Future
type movies right and you have to work
things out in such a way that you don't
mess things up right some people say
that well you come back to the universe
but you come back in such a way that you
cannot affect your journey um but then I
mean that that seems kind of uh
contrived to me or some say that you end
up in a different universe and this also
goes into the the many different types
of the Multiverse hypoth esis and the
many worlds interpretation and all that
but again then it's not the universe
from which you left right and you don't
come back to the universe from which you
left and so you're not really going back
in time to the same universe and you're
not even going forward in time
necessarily then to the same universe
right you're ending up in some other
universe so so you've you what have you
achieved right you you've traveled you
traveled you uh you ended up in a
different place than you started in more
ways than one yeah and then then there's
this idea um the aluer drive where you
warp space time in front of you so as to
greatly reduce the distance and you can
expand the space time behind you so
you're sort of riding a wave through
SpaceTime but the problem I see with
that beyond the Practical difficulties
and the energy requirements and by the
way how do you get out of this bubble
through which you're you know riding
this wave of space time
miguelier acknowledged all these things
he said this is purely theoretical
fanciful and all that but a fundamental
problem I see is that you'd have to get
to those places in front of you so as to
change the shape of SpaceTime so as to
make the journey quickly but but to get
there you you got there in the normal
way at a speed considerably less than
that of light so in a sense you you
haven't saved any time right you might
as well have just taken that journey and
and gotten to where you were
going yeah there's a right you what have
you done you it's not like you snap your
fingers and say okay let that space
there be compressed and then I'll make
it over to Alpha centuri in the next
month you can't snap your fingers and do
that yeah and but yeah we're sort of
assuming that we can fix all the
biological stuff that requires for
humans to persist uh uh persist through
that whole process because ultimately it
might boil down to just extending the
life of the of the human in some form
whether it's through the robot through
the digital form or through or actually
just figuring out genetically how to
live forever CU that Journey that you
mentioned the long journey might be
different if somehow our understanding
of genetics of our understanding of our
own biology all that kind of stuff would
uh that's another trajectory if you
could put us into some sort of suspended
animation you know hibernation or
something and greatly increase the
lifetime and so these 10,000 Generations
I talked about what do they care it's
just one generation and they're asleep
okay long nap so then you can do it it's
still not easy right because you got
some big old huge colony and that just
through E equals MC squ right that's a
lot of mass that's a lot of stuff to um
to accelerate the Newtonian kinetic
energy is gigantic right so you're still
not home free but at least you're not
trying to do it in a short amount of
clock time right which if you look at
eal mc^2 requires truly unfathomable
amounts of energy because the energy is
sort of it's it's your rest mass m c^2
divided by the square root of 1us v^2
over c^2 and if your listeners want to
just sort of stick into their pocket
calculator as V over C approaches
one that one over the root of 1us v^2
over c^2 approaches Infinity MH so if
you wanted to do it in zero time you'd
need an infinite amount of energy that's
basically why you can't reach let alone
exceed the speed of light for a particle
moving through a pre-existing space it's
that it takes an infinite amount of
energy to do so so that's talking about
us going somewhere what
about one of the things that inspires a
lot of folks including myself is the
possibility that there's other that this
this conver