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The sun-- an entity worshiped as a god throughout time
and across cultures.
The source of all life and sustenance
for our little blue space rock.
And also, a force of unthinkable destructive power.
But soon, humanity will reach out its collective hand
and come closer to touching the sun than we ever have before,
with the launch of the Parker Solar Probe.
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NASA put humans on the moon, sent probes throughout and even
beyond the solar system, and drove a minivan-size Rover
across the surface of Mars.
And now, NASA will once again attempt the impossible--
reaching for the one place in the solar system
we never did approach.
The Parker Solar Probe will fly within a hair's breadth
of the sun itself.
Will NASA succeed where Icarus failed?
The sun-- a vast ball of incandescent gas.
100 times Earth's diameter.
Powered by the giant nuclear furnace of its core.
The energy it pumps out equivalent to a few hundred
quadrillion nuclear power stations,
provide essentially, all of the energy
to sustain Earth's biosphere.
But that energy doesn't only come as life-giving light.
It also bursts from the solar surface.
Magnetic storms driving a constant stream of energy
and potentially, destructive particles.
The solar wind, whose origin we see as the solar corona.
The corona is deeply mysterious and difficult to study.
It's visible to the naked eye only
during a total solar eclipse.
We still don't understand exactly why
it burns at millions of Kelvin in temperature--
far hotter than the sun's surface below it.
And its mysteries are not idle curiosities.
Outbursts from the corona--
coronal mass ejections-- present an existential threat
to our civilization.
Humanity is heavily reliant on technology.
Tech that can be damaged or destroyed by solar activity.
In 1859, Earth's protective magnetosphere
was disrupted by a massive coronal mass ejection, dubbed
the Carrington Event, after British astronomer Richard
Carrington who observed it.
Charged particles traveling at nearly 1% the speed of light
bombarded the earth.
Auroras normally only visible near the poles
were witnessed across the entire planet.
The brand new telegraph systems across North America
or in Europe failed, but not before telegraph operators
received electric shocks from currents induced by Earth's
compressed magnetic field.
An outburst of similar size occurred in 2012.
It missed us.
If it had happened only one week earlier,
that "end of world" prediction based on the Mayan calendar,
may have been closer to the mark.
The total financial impact for such an event
has been estimated at up to $2 trillion.
In 1859, we were just beginning to emerge
as a technological species.
Now, such an event would take years or even decades
to recover from.
So maybe it's a good idea to learn more
about the sun's surface?
We already monitor it constantly with ground-based telescopes
and spacecraft orbiting the earth
or orbiting the sun at a safe distance.
So why do we need the Parker Solar Probe?
Well, because it won't just watch from a distance,
it'll get close enough to bathe in the source
of the solar wind.
The primary science objective of the Parker Solar Probe--
as stated by NASA-- is to trace the flow of energy
and understand the heating of the solar corona.
And to explore what accelerates the solar wind.
To do this, Parker is packed with four instruments.
There's the field experiment, which
is essentially, a magnetometer and voltage detector.
It'll directly probe the sun's electromagnetic field
and will connect the sun's magnetic activity
with the sources of the solar wind.
It will also measure the outward flow of the magnetic field
through the pointing flux, as well as the plasma density
and electron temperature.
Finally, it will detect radio waves
from processes responsible for the acceleration of particles
in the solar wind.
Hopefully, teaching us about how that acceleration occurs.
The solar wind electrons, alphas,
and protons instrument-- or SWEAP--
will directly detect the particles that
make up most of the solar wind.
The most common types are electrons, helium ions, AKA
alpha particles, and protons.
It'll make detailed measurements of their kinematic properties
like velocity temperature and density.
It will follow the flow of energy from the solar corona
into the accelerating solar wind and connect the solar wind
to its source.
Next up is the integrated science investigation
of the sun or ISIS.
It will capture the most energetic particles
of the solar wind--
charged particles like electrons, protons,
and heavier nuclei, measuring their energies
and mapping them back to their origin in the corona.
And finally, there's the wide-field imager
for Solar Probe or WISPR.
Really trying hard with these acronyms, guys?
This set of two telescopes will actually
produce images of the solar corona and surroundings.
From that close up, it'll achieve
unprecedented resolution of the solar wind,
including shocks and other interesting structures.
This will provide direct images of the plasma
that other instruments are sampling
from which 3D models of the corona can be made,
pinpointing the source of solar winds.
Together, these instruments work in tandem,
creating a complete picture of the environment
near the surface of the sun.
Of course, as exciting as all of this
is, the big question is, how do we make
sure the sun doesn't melt them?
While we've used heat shields before
on a spacecraft or rovers for entering atmospheres,
this one is different.
It'll need to withstand continuous exposure
over many orbits to solar radiation
and intense temperatures, upwards of 1,650 Kelvin,
while keeping the instruments at room temperature.
For this, a 4 and 1/2 inch the carbon composite heat shield
was developed especially for this mission.
Perhaps surprisingly, one of the biggest challenges
with this mission is getting the spacecraft
that close to the sun, even ignoring its ability
to survive there.
You'd think it'd be easy.
The sun's the biggest object in the solar system
and has the strongest source of gravity.
Why not just let the spacecraft fall towards it?
It's actually much more complicated.
To escape Earth's orbit in the outward direction, you first,
need to escape Earth's gravitational pull
and then, accelerate to achieve a larger orbit.
To move closer to the sun, you need
to first, escape the Earth and then,
lose speed, which can be even trickier than gaining speed
and requires just as much fuel.
Parker will use the same trick as many
of our outbound spacecraft, like Voyager or Pioneer--
gravitational assists.
But instead of sling-shotting around planets
to increase speed, Parker will do multiple flybys of Venus
to reduce speed.
At each pass, Venus will tug on Parker in just the right way
to reduce its velocity, causing it
to fall into a more stretched out elliptical orbit that
will take it closer to the sun.
Venus will end up traveling infinitesimally faster
as it absorbs Parker's orbital energy.
In total, Parker will do seven Venus flybys.
By the end of 2024, if all goes according to plan,
Parker will reach its closest approach
to the sun of 6.2 million kilometers.
That's seven times closer than any human-made object has ever
come.
While its orbital period will be the same as Mercury's--
88 days-- because of its eccentric orbit, Parker
will get roughly 10 times closer to the sun
than the closest planet.
There it will be traveling over a blazing 192 kilometers
per second.
It'll spin roughly, 11 days doing science
during each orbital cycle, while spending the other 77
days in the outer parts of its elliptical orbit, when it
will transmit data back home.
By mission's end, after nearly seven years,
Parker will have completed 26 close approaches
to the sun, five of which will be a relative hair's
breadth from the sun where it will
be bathed in the full force of the sun's violent outbursts.
There.
It'll gather the data we need to understand the corona
and the perilous solar wind.
Humanity has been planning a solar probe since:
the late '50s.
And the dream of flying to the sun
is as old as the legend of Icarus.
Icarus didn't fare so well, but Icarus didn't have a carbon
composite heat shield.
This time if our luck holds, we'll
come close to touching our home star
to unlock the mysteries of our closest stellar neighbor
in space time.
[MUSIC PLAYING]
Hey, guys.
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at the link below,
In last week's episode, we talked about Maxwell's demon--
the thought experiment in which the particles
in two halves of a box are sorted without using energy.
Thereby, decreasing entropy against the second law
of thermodynamics.
This was a surprisingly provocative subject.
Before I get to the many excellent questions,
let me rant a little.
I could not rant, but it's a long, hot New York summer here
and we have to turn the AC off when we shoot,
ranting just feels good right now.
So some folk-- not to be named--
objected to the thought experiment of the great James
Clerk Maxwell--
one of the founding fathers of electrodynamics
and statistical mechanics-- because demons don't exist.
Guys, seriously?
The demon is a metaphor.
It represents some physical system
that can detect incoming particles,
measure their velocity, and then open
the door based on a decision about that velocity.
Also, a couple of people thought that the whole thought
experiment was just stupid.
And they had a simple, obvious solution.
Like I said, I would never support the mindless appeal
to authority.
Just because it took 100 years and some
of the greats of physics to understand the Maxwell's demon
conundrum, doesn't necessarily mean that the solution
isn't obvious.
But you know, it's not a bad indication
that there might be some subtleties
that one's immediate gut instinct might miss.
Listen, don't be afraid to question the conclusions
of our best geniuses.
That's how scientific revolutions happen,
but also, don't be afraid to question your own instincts.
Physics is not intuitive and takes real methodical work
to verify those instincts.
So with that out of the way, several of you
had a very good insight.
Surely, when you open and close the gate to admit the particle,
you use energy.
And if energy is coming in from the outside,
then it's OK for entropy to decrease.
Actually, no.
It's possible to have a perfectly reversible gate.
For example, a compressed spring that when triggered,
opens and closes again, returning it
to its initial state.
It has to be the act of telling the gate to open and close
again that expends energy.
I'll address that in the next comment.
Which is this-- a number of very reasonably
point out that the demon or device doesn't really
need to remember anything to do its job.
It just needs to trigger to open the gate
and then it can forget.
But that's still a memory of one bit that needs
to be reset after every action.
Let's look at just one specific example of a gate.
Say you have this reversible spring-loaded gate.
In order to not continuously bounce open and close,
it needs a latch.
That latch can be thought of as a very tiny activation
energy that needs to be overcome to set the gate moving.
That energy can come from the incoming particle.
And it can be returned to that particle reversibly
by either the latch or the gate, depending on how you set it up.
So an incoming particle is detected
and the latch releases, the gate opens, closes,
and the particle passes through without losing any energy.
The only thing that remains is to re-latch the gate.
That also requires a tiny bit of energy.
You could have multiple latches in place,
primed and ready to lock whenever
they detect the gate closes.
But eventually, you'll need to reset them.
The resetting of the latches is not a reversible process.
Returning the system to its initial state this way
is analogous to resetting the memory of the demon where
the state of each latch is one bit of information.
Remember, Maxwell's demon is just
a metaphor for many potential types of physical gate.
Master Therion noticed that Maxwell's demon's memory
was in the Enochian alphabet of Dr. John Dee.
They fill it in the comment some nice discussion
of Judeo-Christian demonology, in which some of you
are surprisingly, well-versed.
A few of you even try to translate
using the standard Enochian to English table
and got complete gibberish.
Are you really surprised?
Did you think metaphorical physics demons are limited
to our paltry three dimensions?
That their writing is one dimensional?
Come on, people.