Listener Questions #24

Daniel and Kelly answer questions about Jupiter and circadian rhythms.

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Episode Transcript

Speaker 1 (00:07):
If the Earth and Jupiter were to collide, what would happen?
How would we die?

Speaker 2 (00:13):
Circadian rhythms are corrected using the Sun's light. If you
live at the bottom of the sea, how do you
get that right?

Speaker 1 (00:20):
How big a planet could we use rockets to escape?
If we'd evolved on Jupiter, would we be planet down apes?

Speaker 2 (00:28):
Whatever questions keep you up at night, Daniel and Kelly's
answers will make it right.

Speaker 1 (00:32):
Welcome to Daniel and Kelly's Extraordinary Universe.

Speaker 2 (00:37):
With an emphasis on Jupiter, it seems. Hello, I'm Kelly Wiersmith,
and I study parasites and space, and clearly Jupiter is

(00:58):
the best planet.

Speaker 1 (01:00):
Hi, I'm Daniel. I'm a particle physicist, and yes, Jupiter
has the most particles of any planet.

Speaker 2 (01:05):
And does that make it the best As a particle physicist.

Speaker 1 (01:10):
It makes it the mostiest? I guess you know. I
think people underestimate, like how much of the Solar System
is just the Sun in Jupiter? Like mostly it's just
the Sun, and then you want to add Jupiter, all right,
to round it up to nine to nine point nine,
and everything else is just details. We're really just here
in somebody else's party.

Speaker 2 (01:28):
Oh, man, that's a little it's a kind of a
bummer of a way to start our episode.

Speaker 1 (01:34):
We are all insignificant, No, I think it tells you
something though, when you look at the depiction of the
Solar System and all the planets are like big, and
obviously it's not the scale, but it tells you something
about what we find important. Right, Clearly, we are important
in the Solar System. So we zoom up. It's like
that cover of the New Yorker where they show like
a map of the United States from the New York

(01:56):
City perspective, and it's like mostly Manhattan and then like
a few details and that's ridiculous and you laugh at it,
But that's exactly what we're doing about the planets, right.

Speaker 3 (02:05):
Well.

Speaker 2 (02:06):
But you know, on the one hand, we've known about
Jupiter for much less long than we've known about Earth,
and you know, we're here on Earth, makes it easier
to study. I'm going to go ahead and stand down
on defensive Earth and the Earth centered view of the world.

Speaker 1 (02:20):
I'm the saying it's wrong. I'm just saying it reveals
something about our biases, right, the things we think should
be presented first.

Speaker 2 (02:27):
I grant you that, but there's probably, you know, solar
systems that are bigger than ours, and maybe we shouldn't
even be talking about our solar system at all. And
where do you stop, Daniel, Where does it end?

Speaker 1 (02:37):
It never ends, Kelly, There's no bottom to the philosophical
rabbit hole.

Speaker 2 (02:43):
Oh my goodness.

Speaker 1 (02:44):
But we love going down rabbit holes, especially rabbit holes
that you are interested in. So if you have a
question about the nature of the universe, or how something works,
or how little squishy critters make their lives, please write
to us with your question. We would love to answer
it here on the pod. And today we're answering three
super fun questions from listeners.

Speaker 2 (03:03):
That's right, so let's start with our first question from.

Speaker 1 (03:05):
Brad, A great question about Jupiter, of course.

Speaker 4 (03:09):
Hello, Daniel and Kelly. I have a question about planetary collisions.
Jupiter is classified as a gas giant planet and is
known to sweep up many stray masses flowing through our
Solar system. If something were to happen to cause Earth
and Jupiter to collide, what would happen at impact? Is
the mass of Jupiter large enough to spaghettify Earth and
destroy us like a black hole? Or is the likelihood

(03:30):
of a direct collision too small, and Earth would just
be ejected from the Solar System if we become too close.
Or is the surfaces of Jupiter really a gas and
Earth would just pass into the inside of Jupiter and
basically be absorbed, and Earth would just coast through a
dense atmosphere of gases and would eventually hit a solid core.
Thanks Brad from League City, Texas.

Speaker 1 (03:49):
So, Kelly, do you think Brad is a supervillain planning
to push Earth into Jupiter or threatened to?

Speaker 2 (03:54):
You know, I did wonder about that when I was
listening to this question. I'm a little concerned, and you
know what, a little concerned in general now that this
is something you know on my radar to worry about.
And then too, I'm a little worried about Brad in particular.

Speaker 1 (04:08):
A couple of red flags here. Yeah, I'm not sure
in his question if he's worried about this or excited
about it, He's like, let's do the experiment.

Speaker 2 (04:15):
Yeah, yeah, hard to say, hard to say. Maybe we
shouldn't give him the answer m exact.

Speaker 1 (04:22):
I worry about that. Like when the kid wrote to
me and asked me what it would take to blow
up Mars. I was like, hmm, should I really be
telling a ten year old how to destroy a planet?

Speaker 2 (04:31):
Well, but on the other hand, you know, you hope
they don't wield that sort of power, didn't do anything
about the information.

Speaker 1 (04:36):
Who knows what today's ten year olds will do in
twenty or thirty years.

Speaker 2 (04:40):
Right, that's true, that's true, and you'll beat a blame, Daniel,
accept that blame.

Speaker 1 (04:46):
But today we're here to answer Brad's question as a
hypothetical science question about something we hope will never happen,
which does reveal a lot of really interesting solar system physics.
So let's get into it.

Speaker 2 (04:57):
And I think we should probably start with what is
spaghetification because that is clearly one of the best scientific
terms our community has ever come up with.

Speaker 1 (05:05):
Absolutely. Spaghetification is usually used to describe what happens to
an object as it approaches a black hole, in that
you won't just fall in, you'll be torn apart into
spaghetti essentially before you actually fall into the black hole.
And this doesn't just happen around black holes. It happens
all the time in strong gravitational environments. In fact, it's
happening to you, right now, and it's happening to the moon.

(05:29):
It's the result of tidal forces. And the reason simply
is that the force of gravity depends on distance. So
if you're falling into a black hole or you're orbiting
a planet or whatever, and your feet are closer than
your head than your feet have a stronger gravitational force
on them than your head does, and effectively, that's a
force pulling your feet away from your head. And if

(05:49):
that force is strong enough, it will pull your head
off your body or your feet off of your head,
depending on your perspective.

Speaker 2 (05:55):
I'm going to be honest here, I feel like you've
sort of de excitified spaghetti cation for me by being like,
it's just a kind of title force. It's like, what's happening.

Speaker 5 (06:04):
To the moon.

Speaker 2 (06:04):
And I'm like, oh, but I'm spaghetific. That's not what
I imagined in my head.

Speaker 1 (06:08):
Uh, you're imagining some sort of black hole magic.

Speaker 2 (06:11):
Yes, yes, I thought this was a specific black holy
thing and that spighetification really, you know, required you to
be thin like a noodle.

Speaker 1 (06:19):
But okay, physics has been ruining things since fifteen eighty
four or whatever.

Speaker 2 (06:23):
Oh, and what happened in particular in fifteen eighty four.
Daniel I just.

Speaker 1 (06:27):
Made it that date. I was referencing one of Zach's comics.

Speaker 2 (06:31):
I can't remember what year he had on this or
why he picked it.

Speaker 1 (06:36):
I think it was supposed to be like Galleo's experiments
or Bacon or somebody like that. Anyway, the point is
that tidal forces are a thing. So if you approach Jupiter,
for example, then the difference in forces between one side
of your object and the other side of your object,
those are the tidal forces. And that's why we have
tides on the Earth, because the Moon pulls on one
side of the Earth more strongly than on the other

(06:56):
side of the Earth, making it a little bit of
a football, and the Earth it's the same thing to
the Moon, and that's why the Moon is locked in place.
It's called tidally locked because there's a little bit of
a football and it's hard for it to spin away
from having the point a bit of its football aligned
with the point a bit of the Earth's football.

Speaker 2 (07:12):
Okay, but so Jupiter is much bigger than the Moon,
so is you know you said that when the force
gets hard it could like pop a head off. Is
Earth's metaphorical head gonna pop off towards Jupiter or is
it just gonna get like weird tides.

Speaker 1 (07:27):
Yes, So there's a boundary called the Roche limit. If
you get closer than that, you get torn into pieces.
If you're further away from that, you don't. And that's
why some planets have rings and some planets have moons.
If your moon is further away than the Roche limit,
it stays together. Local gravity winds over the tidal forces.
If you get too close, then it gets torn apart
into a ring because the tidal forces overcome the internal gravity.

(07:48):
So that's the Roche limit. So what happens as the
Earth approaches Jupiter, Well, the roach limit for a solid
body like the Earth is actually inside the cloud tops
of Jupiter. Jupiter is a gas giant, and the outer
layer is like fifty kilometers of just clouds blow which
you have like gaseous hydrogen, and then liquid hydrogen, and

(08:09):
then this crazy helium neon rain, and then ocean of
metallic hydrogen before you get to the icy, rocky core.
So the Earth would sink into the clouds without getting
torn apart. It would get torn apart after it already
passes into the clouds.

Speaker 2 (08:25):
Okay, So at that point we are closer to Jupiter
than Jupiter's rings. Right, So Earth's not going to become
like a ring of Jupiter. It's going to get torn
apart and then rain down on Jupiter. Is Jupiter the
planet that has the diamond rain?

Speaker 1 (08:39):
I think that's Saturn. Ah, it is so disappointing thing. Yesh, Jupiter, yawn.

Speaker 2 (08:45):
Come on, Jupiter, step up your game man.

Speaker 1 (08:49):
All right. So now we have a collision of an
entire Earth, right, it's whole. It has not been pulled
apart by the tidal forces of Jupiter, and it hits Jupiter,
and Brad asks like, what's going to happen? And is
it going to pass in and be absorbed to hit
the solid core? And you're definitely not going to make
it all the way to the solid core because even
though Jupiter is a gas giant, it has like layers

(09:09):
and layers of hydrogen. That hydrogen is dense, and atmospheres
have friction. Even here on Earth, where atmosphere is pretty
low density compared to the Jovian atmosphere, you know, there's
re entry. If a rocket or an asteroid tries to
enter the Earth's atmosphere. There's a lot of friction from
the atmosphere and you get all this heat, and most
things that hit the Earth's atmosphere don't make it to

(09:30):
the surface. Same principle applies when the Earth hits the
Jovian atmosphere. Okay, and so what's going to happen is
you're going to compress the Jovian atmosphere, which is going
to heat it up, turn it into plasma, and that's
going to vaporize the crust and the mantle of the Earth. Yeah. Bad,
And so essentially a massive energy release. Here did a

(09:51):
little bit of the back of the envelope calculation, and
assuming that the Earth hits at like sixty kilometers per second,
which is, you know, fast but not super fast for
Solar system speeds, you're gonna release ten to the eighteen
megatons of TNT. Wow. And you might be like, I
don't know what that number means. Well, the Hiroshima explosion
was fifteen kilotons. This is ten to the eighteen mega tons.

(10:15):
So it's like so much bigger. And you know, I
mean the entire Earth is essentially a bomb, and a
lot of that mass is converted into energy. So it's
an enormous explosion. You're gonna get like a fireball rising
above the surface of Jupiter. It's gonna be much bigger
than the volume of the Earth. And you're gonna have
shock waves in the Jovian atmosphere which probably will last

(10:36):
for years. You may even leave a spot on Jupiter.
It's very unlikely you're gonna make it all the way
to the core because you've got lots of dense layers
before you get there. But yeah, it's gonna be a
huge impact. But remember Jupiter is huge compared to the Earth, Like,
it's so much bigger than the Earth that even though
this is an enormous amount of energy and would devastate

(10:56):
the Earth vaporized essentially, Jupiter is gonna mostly shrug it off.

Speaker 2 (11:00):
Oh man, that's a little insulting. Every human I've ever
known or loved disappears and Jupiter's like, eh, okay. Well,
so say at this point, when this happens, we have
a self sustaining settlement on Mars. If the Martians were
like in the right position, could they see this or
would the act of Jupiter moving towards Earth have destroyed

(11:22):
Mars on the way or thrown Mars off orbit. This
is probably unfair. It's a totally different question. But am
I asking you anyway? Daniel?

Speaker 1 (11:29):
Oh? I see well, I was imagining that the Earth
is getting tossed into Jupiter. Read when Jupiter is like
bullying its way into the inner Solar system. Oh okay,
so the Martians have a nice view of Earth shooting
by and then they yeah, they could watch Jupiter as
it gets impacted. In fact, we had ringside seats to
a similar event in the nineties.

Speaker 2 (11:46):
And I think you told me that you were at
a telescope watching that, right, Yeah, I.

Speaker 1 (11:50):
Had a super fast camera hooked up to a telescope
to watch this collision. This is in the mid nineties
comet Shoemaker Levee impacted Jupiter and created all these fireballs.
Now the comet not nearly the size of the Earth,
of course, but still very very dramatic. And what happened
is that this comet, which used to be orbiting the Sun,
got captured by Jupiter. So now it was orbiting Jupiter

(12:10):
sometime in the sixties and in the early nineties it
passed very close to Jupiter, so Jupiter tore it apart.
It went within the roch limit, not actually within the clouds.
The roach limit weirdly and confusingly depends on the object,
Like if you're made out of diamond, then your rochal
limit is much closer. You have to get much closer
to get torn apart than if you're made out of
like cotton candy. Right, And so this comic got torn

(12:33):
apart into twenty one pieces, which they labeled ABCD all
the way up to w NASA.

Speaker 2 (12:39):
Very creative, of course they did. That was an opportunity
for creativity. So they had to pass it by and.

Speaker 1 (12:44):
Then it's swung around one more time, and over six
days in nineteen ninety four, each piece took turns smacking
into Jupiter. Wo really amazing, and everyone on Earth was
like turning their telescopes to it and watching these pieces hit.
And the biggest spot is the one where the g
fragment hit, and so you can imagine what that spot
might be called.

Speaker 2 (13:03):
I was just thinking that, but this is a children's show.

Speaker 1 (13:07):
Exactly, and created a huge dark spot. There was a
fireball and a dark spot the width of the Earth.

Speaker 2 (13:13):
Wow.

Speaker 1 (13:13):
Right now, this fragment is a piece of a comet,
which is tiny compared to the Earth, but it created
a big spot the size of the Earth that was
visible for a year. So we've seen this kind of
impact much smaller, So essentially you just scale this up
much more dramatically, but still small compared to Jupiter.

Speaker 2 (13:28):
Amazing. I wish I had watched them. That wasn't on
my radar because I didn't have amazing friends like you
back then. You wouldn't have let me go astray. But
that's all right.

Speaker 1 (13:38):
I was in college at the time, and I was
home over the summer doing a research project on plasma physics,
and we had a super fast camera that we were
using to image what happened when you drop a little
pellet of fuel into the fusion plasma. And the guy
I worked for also had a telescope and he was like,
let's point this thing at Jupiter. So he connected the
camera to the telescope, pointed to Jupiter, and we had

(13:58):
one of the fastest digital cameras around at the time
for scientific applications, so we were hoping to have like
the highest time resolution photographs of this impact. But just
as the impact was going to happen, it went over
the horizon, so we got pictures of the fireball rising
over Jupiter, but not the impact itself. But it was
a lot of fun anyway.

Speaker 2 (14:17):
So wait, this was ninety four though, is that right?

Speaker 1 (14:21):
Yeah?

Speaker 2 (14:21):
Okay, so I was twelve, so I probably I was
listening to Silverchair and I didn't care about anything other
than Silverchair.

Speaker 1 (14:30):
So important stuff, important.

Speaker 2 (14:32):
Stuff, ohs that way, at the time, the rest of us.

Speaker 1 (14:34):
Were learning about the future impact of Earth on Jupiter.

Speaker 2 (14:36):
But you know whatever, Well, I was having a good time,
so I wouldn't change it for anything, all right. Brad
asked if there was any chance we'd get ejected from
the Solar system, But you didn't mention that as a
as an option, so that's not something that would happen.

Speaker 1 (14:52):
It could happen, It depends on how accurately Brad and
his supervillain team aim the Earth at Jupiter. One possibility
is it hits Jupiter right. Another possibility is that it's
captured and orbit Jupiter. And this has happened to a
bunch of stuff. We think that many of the moons
of Jupiter didn't form with Jupiter but were captured by
it later. But it's a little bit unlikely because for
that to happen, you have to be only at the

(15:12):
right angle and the right velocity at the right location
to get the orbital mechanics to work out. So more
likely you're either going to hit Jupiter or you're going
to get ejected from the Solar System because you're going
to have a gravitational interaction with Jupiter, which is then
going to throw you out of the Solar System.

Speaker 2 (15:27):
All right, well, one way or another. I think someone
should be keeping a close eye on Brad and let's
see if our answer changes Brad's mind about whether or
not this is a good idea.

Speaker 4 (15:39):
Daniel and Kelly, I absolutely love this response. I assure
you that I am not a supervillain and have no
plans to destroy the planet. It sounds like we would
get to watch as we pass into the gas cloud
layer before we heat up and explode. I like to
know that we would at least have a little impact
on Jupiter. I think all we need to know now
is where Michael Bay wants to set up the camera

(15:59):
to catch it's the greatest collision of all the time.
Thanks for all y'all do.

Speaker 1 (16:22):
All right, we're back and we're answering questions from listeners.
Now we're going to take a break from Jupiter themed
questions and think about sleeping. Here's a wonderful question from
one of our Discord listeners. And if you're not on Discord, Colm,
join us on our Discord channel. We have lots of
fun conversations about science. We answer questions on there, other
people answer questions on there. We have wonderful moderators to

(16:43):
keep it a really happy fun family. Colm, join us
for science chats on Discord. You can find a link
on our website. Anyway, here's the question from our listener.

Speaker 5 (16:52):
In the episode about sleeping dreams, the topic of circadian
rhythms in various animals came up. I was curious how
circadian rhythms work in animals that never see the sun,
like cave dwellers or various deep sea creatures. Thanks for
taking the question, looking forward to the answer.

Speaker 2 (17:10):
Bye, all right, t to the j on Discord. I
gotta say, you know, this question came in and I thought,
all right, circadian rhythms. I'm a biologist. I should be
able to knock this answer out pretty quick. I don't
know anything about circadian rhythms. It turns out, oh no.

Speaker 1 (17:26):
This was biology is a big field.

Speaker 2 (17:28):
That's what I'm saying, but I really enjoyed the opportunity
to get to dig into circadian rhythms again. This is
one of the things I love about the questions we
get from listeners. There's so many things I thought I
understood and then they give me a chance to dig
into them, and I learned so much. So uh, circadian rhythms.
Circadian comes from the words circa diaz, which means approximately

(17:49):
a day. And I'm you know, I don't know, maybe
that's Latin. I probably pronounced it wrong, but you all
know what I'm saying. So it's all right. We're good
and nobody expects me to pronounce things right at this point.

Speaker 1 (17:58):
That's not what they're here for, Kelly, is not.

Speaker 2 (18:00):
What you're here for. So circadian rhythms are like internal
rhythms that happen on an approximately twenty four hour cycle,
and they're entrained or they're sort of like synced up
based on outside signals like light.

Speaker 1 (18:16):
But why do you say approximate? I mean, the earth
cycle is pretty crisp. Wouldn't we do best being closely
linked to it? Why are you saying approximate?

Speaker 2 (18:25):
Because you know it's just not perfect and some people
have cycles that are a little bit longer than twenty four.
Some people have cycles that are a little bit shorter
than twenty four. We think this contributes to why some
people are mourning people and some people are night people.
And then if you're talking about organisms other than humans,
you can get some other slightly different sorts of signals
that are approximately twenty four hours.

Speaker 1 (18:46):
So then what parts of the human body are affected
by it? Obviously you sleep in this sort of twenty
four hour cycle. Is there other stuff going on also?

Speaker 2 (18:54):
Yeah, lots of things. So like sleep is important, metabolism
is also important. Like your body temperature is impacted by
circadian rhythms.

Speaker 1 (19:03):
Right, metabolism, So that is that why I shouldn't eat
chips at ten pm?

Speaker 2 (19:06):
That could partly be it or be involved. I think
cortisol is to some extent involved in helping with digestion
and stuff, and so your cortisol kind of peaks at
times of day when you're like expected to be hungry
and expected to be eating.

Speaker 1 (19:20):
What's cortisol?

Speaker 2 (19:21):
Cortisol is a hormone that folks usually associate with recovery
from stress. So when you get stressed out by something,
your body releases cortisol, and then cortisol helps your body
sort of return to homeostasis or like a normal state
after you've been stressed out.

Speaker 1 (19:36):
Cortisol sounds great, as you can say more of that.

Speaker 2 (19:38):
Well, if you are, like, you know, running away from
a lion, cortisol is great, like it releases a bunch
of energy all at once that you can outrun the lion,
and then when you're in a safe spot, it helps
you sort of return to normal. But if your cortisol
level is elevated for a very long time, you can
start having diseases because you're constantly in a stressed out state.
So cortisol is more supposed to like get you out

(19:59):
of an intent hence acute situation, but if it's elevated chronically,
it can be bad. And there's a really interesting book
on this called Why Zebras Don't Get Ulcers by Robert Sippolski. Cool.

Speaker 1 (20:10):
All right, yeah, well, I wonder if zebra's go to
my physics faculty meetings if they feel stressed out and
need cortisol afterwards.

Speaker 2 (20:17):
Oh yeah, faculty meetings. I think what I'm stressed out
about in faculty meetings is that I could be spending
my time way better doing anything else. But you know,
I haven't had to go to faculty meetings for a while,
so that's great.

Speaker 1 (20:28):
Dark wasn't Today is not about silly arguments and physics
faculty meetings. It's about the rhythms of the body. So
you're telling us that these things happen and impact sleep, metabolism,
and temperature. But what's the mechanism for it? Like, what
is driving it?

Speaker 4 (20:40):
Yeah?

Speaker 2 (20:40):
Okay, So most of the work that we've done to
figure out the mechanism has been done in organisms like
mice and fruitflies. But here's how we think that it works.
How we're guessing that it works in humans based on
what we've seen in lab animals. So there's a little
part of your brain called the hypothalamus, and inside of
the hypothalamis there's a little region called the super chiasmatic

(21:00):
nucleus or the SCN. Because I'm not going to try
say that a bunch.

Speaker 1 (21:03):
Of times it sounds a lot like super cool, fudulistic,
expire audotious, but all right, yeah, I hear that every
time you say that.

Speaker 2 (21:09):
Now, okay, no one's going to be able to pay
attention to the rest of the episode. They're going to
be singing just like Mary Poppins, but try to focus people,
all right. So you've got the SCN, and the SCN
is connected to the optic nerves, and so optic nerves
these are the nerves that go to your eyes. And
so we've talked in the past about how your eyes
have specialized cells called rods and cones, and those help

(21:33):
you detect like patterns and colors and to see your world.
But you also have cells that just detect the intensity
of light, and those cells send information through your optic
nerve back to the SCN, and your brain uses that
information to tell the rest of your body how the
rhythm should be working. And so it does this by

(21:54):
either sending messages through the nerves or by directing the
production of hormones that will then go to the rest
of your body and talk to your cells and basically say, Okay,
hey guys, it's morning. And when it's mourning, your body increases,
its heart rate, increases, its blood pressure, increases temperature. Your
body is not making melatonin at this point. Melatonin is

(22:17):
associated with sleep. So this is generally how your body
collects the information about what should be setting the timing
for the rhythm. But each one of your cells also
has its own circadian clock.

Speaker 1 (22:30):
So we have these special cells in our eyes. Instead
of just using the information which already exists in the
rods and cones, we like evolve the separate pathway just
for this. Wow, this is pretty weird engineering.

Speaker 2 (22:41):
Well, but it's detecting something different. Your rods and your
cones are detecting like colors and you know, patterns of
like dark against light and stuff like that. These cells
are just detecting the intensity of the light that's coming in.
So you're like, oh it's dawn now, or oh it's noon,
and so it's detecting that.

Speaker 1 (22:59):
I feel like I could write a computer program to
extract the same information from the data produced by the
codes and the rods. But that's fine. Obviously the brain
is not engineered by physicists.

Speaker 2 (23:09):
And that's not how evolution works. Evolution doesn't say, Okay,
I'm going to start from scratch and come up with
the best system. It's like, well, what do I have
and how can I work with it?

Speaker 1 (23:16):
I just think it's a fascinating clue that something happened
there that this is what we ended up with. You know,
It's just another example of how like obviously this is
not well organized. Just what kind of worked? And so
do we know this because we've like done studies in
mice where we've like tweaked those cells or got rid
of those cells, or like shined light on those cells
or something, and it's changed the way the mice behave.

Speaker 2 (23:37):
Yeah, so if you mess up a mouse or a
flies SCN, then they'll start free cycling. So essentially they
won't show these twenty four hour cycles.

Speaker 1 (23:46):
They're not so xpl a doocious anymore.

Speaker 2 (23:49):
That's right, that's right. It's truly quite atrocious.

Speaker 1 (23:51):
All right, So that's wrong. Okay, that was pretty good.
That was really good.

Speaker 2 (23:58):
Grudgingly patting me on the back there.

Speaker 1 (24:00):
I was so excited about my next question. I didn't
registering a joke, but that was excellent. Yeah, ten points
for Kelly for everybody's keeping score. So you're telling us
that not only these light signals tell us when to
be fragilistic, but also the rest of our body responds
in some way.

Speaker 2 (24:17):
Yeah. Okay, So first I just want to mention real
quick that that organisms from bacteria to humans show these clocks,
and so this is like not every organism uses their
SCN and so this sort of like feeds back on
our conversation about how you just use what you have.
This has been going on for a really long time anyway.
So not every single cell has its own circadian clock.

(24:40):
I misspoke earlier, but many cells, even if you take
them out of the body and you put them in
like a petri dish, they will show like a twenty
four hour schedule for the activities that they do, like
they've repair DNA at a certain time, you know, stuff
like that. And so here's how we think that works.
So your cell is making a a protein called clock protein.

(25:03):
The clock protein at dawn moves into your nucleus where
the genetic information is stored, and it binds to literally
thousands of different sites on your DNA. And when it binds,
it's telling your DNA to start making certain things. And
it could be making certain hormones, like it can say, hey,
start making that cortisol. It could start doing you know,

(25:23):
whatever is needed to increase body temperature or heart rate,
et cetera. So thousands of things are turned on when
your clock proteins go in there and bind to lots
of different spots. Another thing that's being made. Though, during
the course of the day are proteins that will shut
this down. And these proteins are called period proteins, And
so the period proteins will build up over the course

(25:45):
of the day because the clock proteins said, hey, start
making these, and at some point they've built up to
high enough levels that now they go into the nucleus
and they pull the clock proteins off of the DNA
and that stops all of the stuff that the clock
proteins had been turning on and getting made. As the
night goes on, the period proteins break down and go away,

(26:05):
and then the next morning the clock proteins go back
in and the cycle starts again.

Speaker 1 (26:10):
So, like many clocks, you have some sort of process
which has a natural timescale built into it, right, and
so there is chemistry where things are slashing back and
forth and naturally at the same rate as our twenty
four hour cycle. Is that what's happening?

Speaker 2 (26:24):
Yeah, yeah, that's a good summary. And I saw you.
Yeah cool looking something up? Was I wrong about something
or was it unrelated?

Speaker 1 (26:31):
I was wondering if clock was an acronym for something
in a really tortured way.

Speaker 2 (26:35):
But oh, okay, right, I.

Speaker 1 (26:39):
Was hoping it stood for something ridiculous. Okay, because if
it was a physics acronym, it definitely would have a
ridiculous name.

Speaker 2 (26:45):
Got it anyway, So light is important for determining these cycles, right,
But it also is fine tuned by things like the
temperature you find yourself at when during the day you're eating,
and these cues are important for other animals as well.
So it's not just light, but light does seem to
be a super important factor.

Speaker 1 (27:02):
So it's interesting you have several different kinds of things
going on. Can they get out of sync or is
there something that tries to keep them in harmony.

Speaker 2 (27:09):
Well, so, once you develop a cycle, your body is
pretty good at keeping that cycle going. So like if
you stayed in a dark room for two days, your
body would still have some of its normal cycle. It's
not like it breaks down immediately, but over time, if
you deprive your body of that light queue or you
mess your cues up, then you can start having problems.

(27:29):
So for example, if you work the night shift, you know,
any of us who have had jet lag have had
like a temporary period where circadian rhythm was like something's
not right, and then it's had to get back to normal.
But being off of your normal circadian rhythm too often,
for example, working the night shift increases your risk of diabetes, obesity, depression, dementia,

(27:50):
and some kinds of cancer. So these circadian rhythms seem
to be important for a lot of reasons, at least
for humans.

Speaker 1 (27:56):
Wow, and how widespread are circadian rhythm that everything on
Earth has a circadian rhythm?

Speaker 2 (28:02):
Well, so like bacteria, humans, plants, lots of stuff has
circadian rhythms. But our listener had a really great question,
which is how on Earth do you have a circadian
rhythm if you live in a place with no light?
And so the three different situations that I looked into
where there's no light are if you are, for example,
at the North Pole during the time of year where

(28:24):
you don't see the sun. There's like, I think a
couple months where that's the case, if you live in
a cave, or if you live in the deep sea.
And then there's also organisms like naked mole rats that
live underground. But I think naked molerats can peek their
heads out every once in a while and see the
sun to help in train their clock, so they get
some light cues still, So let's start with if you

(28:45):
live far north. So one thing that's important to note,
which we touched on just a second ago, is that
clocks don't go away immediately just because you're in total darkness.
So at the start of the long night, they're probably
fine because their body hasn't like forgotten the rhythm yet.
And during the time of year when it's all light,
they're probably also fine because the intensity of the light

(29:09):
still changes over the course of the day, and your
eyes are focusing on light intensity, not just whether it's
there or not, so they can still keep their rhythms
at that time of year. But there is a point
in the winter where their clocks have not had appropriate
input for long enough because it's been dark for so long,
and they do seem to stop showing signs of twenty

(29:30):
four hour cycles if you look at the reindeer, So
it looks like at some point they do start free
cycling essentially and their circadian rhythms start to break down. Wow,
they don't seem to have physiological problems associated with that.
I'm not quite sure why, but it looks like they
do break down at some point, So.

Speaker 1 (29:47):
It's bad for them to be in the dark, like
it would be better if they got light occasionally to
sort of like correct their cycles or get them back
on track.

Speaker 2 (29:54):
Yeah, So I was trying to figure out the answer
to that, and I think that the answer is to
some extent that it's complicated. So, you know, part of
why we have cycles is that it helps us figure
out like when we should be eating and stuff like that.
And part of that, if you are a wild animal,
is about when your food is even available, right, But

(30:14):
if you're in the dark and all the other animals
are in the dark all the time too, you might
not need to have a circadian rhythm because it might
you know, if you're, say you're a fox living in
the Arctic circle, you want to make sure you're awake
at the same time as the bunnies. But if it's
complete darkness and everybody's free cycling, you don't really need
to get up at a certain time because the bunnies

(30:35):
could be out there at any time, and so it's
not a helpful queue anymore to like have your activities
sync to a certain time of day.

Speaker 1 (30:42):
I was wondering more about the internal stuff, Like you
mentioned earlier that if your rhythm gets messed up your
risk for diabetes and cancer and stuff. Is the same
thing true for reindeer when they're free cycling.

Speaker 2 (30:52):
Yeah, so I don't know the answer for reindeer, but
I did try to find the answer to that question.
I was able to find some information about blind cavefish.
So there are fish that live in caves that have
closely related ancestors that live outside of caves. Oh, okay,
And so you can compare you know, essentially these like
sister species or sibling species and see how they differ.

(31:16):
And the species that live in caves don't have shorter lives,
and in a lot of cases they have longer lives
than their surface living counterparts. Well, okay, and then let
me tell you about their circadian rhythms. That's the important
piece here. So people were trying to figure out if
cavefish have circadian rhythms, and they were trying to figure out, like, okay,
in the absence of light, how do you do that?

(31:39):
And so one idea they had was that maybe bats
that go in and out of the cave are what
they're queuing into. Because when the bats leave where they
come back, they poop in the water and that poop
provides food for a lot of cavefish, right, so maybe
that's what they're sinking to, but there was no evidence
that that was actually happening, So it looks like they're
not sinking to that.

Speaker 1 (32:00):
But there could be a lot of similar effects right
where things are happening outside the cave, and like even
the microbes in the air or something like that could
be affecting. You could be sensing indirectly the fact that
there's day and night outside the cave from inside the cave.

Speaker 2 (32:14):
Yeah, that's right. But so people have also brought the
cavefish into the lab, and when they bring them into
the lab and they expose them to normal light cycles,
they can develop circadian rhythms. So they still even though
they don't have eyes, they still must have like the
cells needed to detect light, and they can develop rhythms.
But it looks like various parts of their circadian clock

(32:36):
are messed up. So if you look at things from
the genetic level, it's kind of messed up, and it
looks like they also for the most part, are losing
their circadian rhythms in the cave, but that doesn't seem
to be shortening their lives.

Speaker 1 (32:49):
Wow, fascinating, Yeah, which.

Speaker 2 (32:51):
Is not what I expected. Like I spent a long
time being like, well, no, what is the queue? They
have to have circadian rhythms, And then I found a
review paper that pretty much was like, the rhythms kind
of seem to disappear in caves. They're just kind of
like moving around whenever and sleeping whenever.

Speaker 1 (33:05):
And that's okay, And that's okay.

Speaker 2 (33:07):
We're not judging.

Speaker 1 (33:08):
Teenagers everywhere are like see mom, it's fine for me
to stay up until two.

Speaker 2 (33:11):
Am, all right, and their rooms are kind of like
messy caves. And I see lots lots of points of
comparison here.

Speaker 1 (33:20):
All right, what about at the bottom of the ocean
where light doesn't filter down?

Speaker 2 (33:24):
Okay, so this is interesting. So after I had finished
the research on caves, my expectation was that animals that
live in the deep sea are also going to not
really show circadian rhythms because they're you know, they're down
in an area where the light isn't getting to But
I thought, well, you know, maybe there's still some cues,
Like a lot of the food that comes to the
deep sea comes from things just sort of like dying

(33:45):
and raining down, and I thought, maybe there's like a
daily pattern to how the food rains down. But this
is actually really hard to study.

Speaker 1 (33:54):
When the carcass snacks happen, that's really.

Speaker 2 (33:56):
Well, you know, I pay attention to snacks.

Speaker 1 (34:01):
Kids, dead bodies are falling, come on outside. What is
it like to be a parent at the bottom of
the ocean.

Speaker 2 (34:07):
I mean, when a whale falls down, it is like
buffet for months. The videos are messed up. But so
the way that folks tend to study this is, you know,
they either take the deep sea animals into the lab,
but if you bring them into the lab, you're often
like turning on lights to study them, and so now
they're in like a not natural environment. And you know,

(34:28):
labs in general are not like the bottom of the sea.
But another way that people study it is they will
put like essentially mobile labs. They'll lower them down to
the bottom of the sea and then they'll like take
pictures or videos and try to see if they can
detect cycles and what's happening down there. But another problem
there is that they turn on lights often when they
do that. Yeah, and so this stuff is hard to study.

(34:49):
But I found a study that did use cameras with lights,
and they found that a lot of species didn't show
detectable patterns, but it was also hard to get large
sample sizes. But they did find that there is a
kind of worm that lives in a tube and there's
a pattern to when it sticks its head out of
the tube to try to get food. They were looking

(35:10):
at different things that were changing in the environment, and
it looks like this behavior is correlated with the tides.
So you can still feel the tides at the bottom
of the sea. Oh wow, which is amazing. I didn't
realize that.

Speaker 1 (35:22):
Yeah, thank you Moon, and see it's all connected. Yes,
it turns out there is a through line for the
whole episode.

Speaker 5 (35:28):
That's orry.

Speaker 2 (35:28):
I guess. Spaghetification is kind of interesting, but I guess
so it's not just the tides, but the tides have
different temperatures, so it could be temperature that's queueing this.

Speaker 3 (35:37):
Yea.

Speaker 2 (35:37):
The tides also can bring food, so maybe it's the
food that's queuing the clocks. And this information is largely observational,
so there's still a lot that we have left to learn,
but some indication that tides can be what's impacting timing
in the deep sea and that's literally everything I know
about circadian clocks, because this is complicated.

Speaker 1 (35:57):
All right, So bottom line for us, what do we
know about how circadie rhythms work? And animals that never
see the sun.

Speaker 2 (36:02):
Sometimes you're poned and you can't create a circadian rhythm
because you just don't have the cues. Other times you
can find something that correlates with the light, or sometimes
instead of having a circadian rhythm, you have a circ
a title rhythm or something, and you're queuing in on
some other environmental thing that can help you maintain a

(36:23):
rhythm in your life.

Speaker 1 (36:24):
Well, I thought that answer was super colent, fragilistic. But
let's hear what our listener says and see if there
are follow up questions.

Speaker 5 (36:31):
Wow, thanks for answering my question. Never would have thought
that deep sea creatures could sense the tides all the
way down there. That's pretty cool.

Speaker 2 (36:59):
We are backed Jupiter, a fascinating planet that could kill
us all. Arthur, what do you want to know about Jupiter?

Speaker 6 (37:08):
Hi, Denim and Kelly. Nice to talk to you guys.
I have a rocket thrust issue.

Speaker 3 (37:14):
I know that we can't escape the gravity of a
black hole no matter how powerful our rocket is, but
I don't know the largest mass of a planet we
can escape from with our current technology.

Speaker 6 (37:27):
I mean, can an.

Speaker 3 (37:29):
Average space rocket lift off from jupter, from the Sun,
from a neutron star?

Speaker 6 (37:34):
I hope you have some funds are in this thanks.

Speaker 1 (37:37):
See, Jupiter is just so attractive gravitationally, people can't stop
thinking about it.

Speaker 2 (37:42):
It's beautiful also, all right.

Speaker 1 (37:47):
So Arthur is wondering about taking off from planets because
the more massive the planet, the stronger the gravity, the
harder it is to lift off of. And he wants
to know if an average rocket could actually get you
off of Jupiter or even more exotic and denser locations.

Speaker 2 (38:03):
So the first thing I want to know is I
can tell from the answer it's going to require math.
Did you do these calculations or is there a website
that has this information.

Speaker 1 (38:13):
There are a lot of websites that have this information,
but I never trust them because you can find mistakes
on those websites, which is the source of a lot
of mistakes in like chat GBT, because it just like
strips some from the websites and gives you the answer,
sometimes in the wrong context or whatever. So I always
double check these myself. All right, wow, so what matters
for lifting off the surface? You're probably going to think

(38:35):
escape velocity. And first I want to say it's not
about escape velocity, but then it's going to turn out
to be about escape.

Speaker 2 (38:41):
Velocity physicists, I know.

Speaker 1 (38:43):
So escape velocity famously is the speed you have to
be going so you can escape the gravitational pull of
an object. Right, So for example, if I'm standing on
the surface of the Earth, how fast do I have
to throw a baseball straight up so that it just
keeps going forever? That it's kinetic energy over comes the
potential energy, Well, that has to climb out of right,
So as you move up away from the Earth, you're gaining.

(39:07):
Potential energy has to come from somewhere. It comes from
your kinetic energy. If you have enough kinetic energy, then
you can go forever. Essentially, if your kinetic energy overcomes
the potential, well you have to climb. So you have
to go fast to escape the Earth. But the reason
that's not what this is about is that that's not how
rockets work. Right, Rockets you don't slingshot them from the

(39:27):
Earth in one push. I mean, people are working on that,
and it's hilarious, but traditional rockets.

Speaker 2 (39:32):
Wait, why is it hilarious and not inspirational?

Speaker 1 (39:36):
It's just like the grown up version of a nine
year old boy's idea for how to get to space,
you know, like, let's pull back a really big rubber band,
you know. I mean, I knew they're working on sentrifusions
and it's pretty cool, but it seems like impractical to me.
Also because the g forces are insane, so I think
you could probably launch like stuff into space, but not people.

Speaker 2 (39:56):
Anyway, that's my sense too. Yeah, you're launching stuff hard and.

Speaker 1 (39:59):
Payloads anyway, That's not how traditional rockets work. If you notice,
when a rocket takes off, it's not going super duper fast.
It's very slowly climbing, right, And that's because rockets don't
have a single hard push at the beginning where they
gain a lot of speed and then gradually lose it
as they rise. They have a continual force. They have
an engine on them, so rockets only have to go

(40:21):
non zero velocity in order to move up. Right, as
long as the force from the rocket is greater than
the force of gravity from the Earth, it's going to
be moving up okay, right, So it can move up
super duper slowly. It could take like a year to
take off from the planet, doesn't matter. It's not about
escape velocity. It's about putting enough energy in to overcome
the potential energy to the Earth, but doesn't have to all

(40:42):
be upfront. So that's why it's sort of not about
escape velocity.

Speaker 2 (40:46):
Okay. But so say you were lifting off at like
a foot per second, that would be much more energetically expensive,
wouldn't it, Because you're needing to like maintain the mass
you're trying to send up as you slowly go up,
And if you do it all faster, that's probably more efficient.

Speaker 1 (41:04):
It's more efficient. Yeah, And if you do it all
at once, just by giving it one big push, then
you don't need to bring any propellant with you and
you can just accelerate the payload. Right Whereas if you're
climbing up at a foot per second, yeah, you've got
to bring the rest of the latter with you essentially,
and you've got to lift that fuel. So we're definitely
going to.

Speaker 2 (41:20):
Get there, okay.

Speaker 1 (41:21):
So what we do need to do is think about
how much fuel we have to bring and how we
can overcome this energy, and so you have to calculate
how much kinetic energy do you need to overcome the
potential energy the Earth. It's not important that it albeit
at once, and rockets do it gradually. But the way
to calculate that is to calculate what they call the
delta V, the change in velocity that a rocket can provide.

(41:43):
And in the end, this turns out to be very
similar to the escape velocity, and it makes sense that
it's similar because they're both connected to essentially how much
energy you need to climb out of this gravitational well
and so. On Earth, the escape velocity is about eight
kilometers per second. That's how fast you would have to
throw a baseball or launch a payload from the surface.

(42:04):
But it's also very closely connected. We'll use the rocket
equation in a minute to how much fuel you have
to bring with you, and that's going to turn out
to be the limiting factor of whether you can lift
off the planet is can you practically bring enough fuel
to get this much delta V? So on Earth you
need like eight kilometers per second, and then you go
to the rocket equation. The rocket equation says how much

(42:26):
mass do you need to bring so that you can
do this, so you can climb out of this gravitational well,
because remember a rocket, what is it doing. It's throwing
stuff out the back. Right. The way it works is
it's conserving momentum. Imagine you like in a rowboat and
you have a pile of bricks. You throw the bricks
out the back of the rowboat. The bricks go backwards,
you go forwards. That's how a rocket works. It's throwing

(42:48):
stuff out the back. So you have to have that
stuff in the rocket to throw out the back in
order to propel it. It's helpful if that stuff also
has the energy you can use to push the propellant.
It doesn't have to be you can have those things
be uncoupled. But in a chemical rocket you have fuel
which is both propellant and the source of energy, and
the rocket equation tells you what your mass ratio is.

(43:09):
So on Earth, for example, you need a delta vive
about ten kilometers per second. That tells you your mass
ratio is nine, which means you need a nine to
one fuel to payload mass ratio.

Speaker 2 (43:20):
That's not great.

Speaker 1 (43:21):
It's not great. Yeah, if you have like one hundred
kilogram person and a thousand kilogram spaceship around them. You
need nine times as much mass in fuel to get
that thing into orbit.

Speaker 2 (43:32):
Wow. Yeah, how much worse is it for Jupiter? And
does it scale linearly?

Speaker 1 (43:36):
It scales exponentially, which is the bad news. Right, And
so say you're on a super Earth which has the
mass of like five to ten times the Earth, then
the escape velocity is like twenty five to thirty kilometers
per second. Okay, that's not so bad. It's three to
four times as much, but the mass ratio is ninety three.
It's ten times as bad as it is here on Earth.

Speaker 2 (43:57):
Ninety three to one, ninety three to one.

Speaker 1 (44:01):
So instead of having a nine to one fuel to
payload ratio, you have a ninety three to one fuel
to payload ratio. So now like your rocket is basically
just fuel, right, and that's just for a super Earth.
Now go to Jupiter. Jupiter is so massive that it's
escape velocity is like forty kilometers per second, and this
gives a mass ratio of more than one thousand Wow. Right,

(44:22):
so you'd need a fuel tank that's a thousand times
bigger than your payload. This is probably even an underestimate,
but essentially this is impossible for chemistry, right, The chemical
rockets cannot achieve this. And if you went to the Sun, right,
then the escape velocity from the Sun is four hundred
kilometers per second, and so now the mass ratios are
just astronomical. From a neutron star, the escape velocity is

(44:46):
four tenths the speed of light. And so I couldn't
even get my calculator to give me a number on this.
W was just so big. And so the bottom line
is that chemical rockets, where you have this fuel and
you're slowly climbing out of the gravitational well, well they
work pretty well if the escape velocity is low. Because
the mass ratio is pretty small, you can afford nine

(45:06):
to one, which sounded bad already to you, right, But
on a bigger planet like a super Earth, it's pretty
hard to use. And a Jupiter or the Sun or
a neutron star, it's definitely not practical.

Speaker 2 (45:17):
So what about like a project orion's style propulsion system?
So if you were exploding nuclear bombs out the back
of your rocket to send you up, could you get
off of Jupiter?

Speaker 1 (45:28):
Yeah? You could. This is limited to chemical rockets, right,
and you can have other strategies you could build a
space elevator, right. You could have nuclear propulsion, absolutely, and
especially if you're launching the nuclear weapons behind the rocket
somehow so that they don't have to come along with
the rocket, then you can escape this trap of having
to bring all of your propellant with you. Yeah. Or

(45:49):
if you have like a light sale with a laser
behind it, you can use that to lift off of
a planet. Or you could just build your thing in space. Anyway,
while you're building it on the surface of Jupiter. Doesn't
really make sense unless that's where your super villain hideout is. Oh,
which case, I have to wonder Jupiter doesn't get a
whole lot of light. I wonder how your circadian rhythms
are going in your supervillain layer one.

Speaker 2 (46:11):
You better hope that Bread isn't sending the Earth greening
into your your supervillain layer on Jupiter.

Speaker 1 (46:16):
Oh, maybe he's saving us, right, maybe he's using the
Earth that doesn't really work, using the Earth to crush
somebody else's supervillain layer.

Speaker 5 (46:24):
Yeah, not a.

Speaker 2 (46:25):
Great plan, Brad, not paying you to write that plot, Daniel.

Speaker 1 (46:31):
So yeah, chemical rockets work essentially only on smaller planets.
On bigger planets, you need other technologies, but those technologies
are not impossible. So I think if we did evolve
on Jupiter or on the surface of a neutron star,
technically it's still possible to get off of those, but
not with rockets.

Speaker 2 (46:48):
All right, let's see if Arthur has any follow up questions,
and maybe he'll tell us what his supervillain plan is.

Speaker 6 (46:56):
Thanks guys for the kind of answer my question. I
knew that enough from a bigger planet would be hard,
but I didn't knoww it would be almost impossible, at
least for chemical rockets, as you explained. I think that
this either puts a big as the risk on plans
for space exploration since the range of celestial bodies we

(47:17):
could visit would be very limited, or either forces research
for more efficient technologies. As you mentioned, all I have
to say about supervillains is that they love rockets these days,
so I do not doubt they have plans for this
massive loudness.

Speaker 1 (47:33):
Thanks a lot, all right, thank you everybody for sending
in your questions. Remember you can write to us two
questions at Daniel and Kelly dot org and send us
your thoughts about the universe, your musings, your wonderings, your
philosophical meanderings. Please, we'd love to hear from you.

Speaker 2 (47:46):
Can't wait to hear from you.

Speaker 1 (47:47):
Thanks, everybody, stay curious.

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