Editing 2004: Sun and Earth

{{comic
| number    = 2004
| date      = June 8, 2018
| title     = Sun and Earth
| image     = sun_and_earth.png
| titletext = But we don't need to worry about the boiling masses sandwiching the thin layer in which we live, since we're so fragile and short-lived that it's unlikely to kill us before something else does! Wait, why doesn't that sound reassuring?
}}

==Explanation==
This is one of a number of comics which describe everyday events in unusual terms, making them sound really weird. In this case, both the Sun and the Earth are "massive convective systems [blasting] huge plumes of heat", which contrasts sharply with the daily idea of the Sun being a ball in the sky and the Earth the thing under our feet.

{{w|Free convection}} is based on an difference in density.  What is colder is typically denser, so gravity forces it downwards, displacing what is hotter (and less dense) upward (This should not be confused with {{w|forced convection}}, which uses fans or other devices that are not practical to build on the scale of a planet). In the sun, most of the energy to drive this process comes from nuclear fusion, specifically the fusion of hydrogen into helium.  We cannot directly see inside of the earth{{Citation needed}}, but its core is known to be much hotter than its surface.

The magnitude of these systems gives you an idea of the size of the fluctuations you can expect. The sun is very massive, meaning the fluctuations in its convective or heat-dissipating behavior are very large. This is an instance of the {{w|Fluctuation-dissipation_theorem|Fluctuation-Dissipation theorem}}. These fluctuations take the form of a solar flare, as explained below. For a more thorough (but non-technical) explanation of the role of gravity and entropy in such systems, see [https://arxiv.org/abs/0907.0659 this]. 

The {{w|Sun}} produces great amounts of light and heat and blasts it towards us, which is why we can live on Earth. Since Ludwig Boltzmann pointed out the fact in 1875, people have been working on establishing exactly how such far from equilibrium systems as life might depend upon, or be formed by ([https://www.quantamagazine.org/first-support-for-a-physics-theory-of-life-20170726/ like this article]), such massive entropy gradients as between the sun and earth (or rather the sun and empty space). Main sequence stars like the sun transport energy by {{w|Radiation_zone|radiation}} and by {{w|Convection_zone|convective currents}} of {{w|Plasma (physics)|plasma}}, bringing the heat generated in the core of the sun to its surface.  These quickly moving charged particles create a massive magnetic field, which occasionally gets concentrated into a {{w|solar prominence}} which can snap, causing a large amount of charged particles to get shot into space as a {{w|solar flare}}.  If the Earth happens to be in the direction of the solar flare, we can notice all sorts of interesting and often damaging effects.  Thankfully, there are lots of other directions{{Citation needed}} for the sun to shoot solar flares, so they don't come by the Earth that often.

The {{w|Earth#Internal_structure|Earth's interior}} is also very hot. {{w|Mantle convection}} causes {{w|plate tectonics}} which is the main cause of {{w|Volcano|volcanic activity}} (next to {{w|Mantle_plume|mantle plumes}}), which essentially also consists of huge blasts of heat.

This could sound like a very bad scenario, but the title text reminds us that the real scenario we live in is far worse, as we are not likely to die from a Sun blast or volcano eruption. In doing this, he indirectly points out the hard truth about our lives: that they're limited and they're short, and it is far easier to die of because of other things. In this way Randall attempts to give the reader an existential crisis; he concludes that his statement did not help to reassure himself.

This comic was likely inspired by the recent eruptions of the {{w|Kīlauea}} and {{w|Volcán de Fuego}}. In contrast, solar activity is currently low, because the {{w|Sunspot#Solar_cycle|sunspot solar cycle}} is in the low end of the 11-year cycle.

==Transcript==
:[The entire comic is within a panel. At the bottom of the image a curved shape depicting a small part of the Earth's surface and labeled as "Earth" is shown. At the top a similar sized shape but opposite curve is labeled as "Sun". The surface of the Sun is seething while on Earth's surface a few plants, two birds, and Cueball together with Megan are visible.]

:[Two arrows pointing to the Sun and the Earth with a caption applying to both of them:]
:Massive convective systems which occasionally blast huge plumes of heat at us without warning through mechanisms we can't directly observe and don't really understand.

:Cueball: What a nice day!

{{comic discussion}}

[[Category:Comics featuring Cueball]]
[[Category:Comics featuring Megan]]
[[Category:Science]]
[[Category:Volcanoes]]
[[Category:Astronomy]]