Editing 1371: Brightness

{{comic
| number    = 1371
| date      = May 21, 2014
| title     = Brightness
| image     = brightness.png
| titletext = Recently, some exoplanet astronomers have managed to use careful analysis of reflected light to discover Earth during the day.
}}

==Explanation==
{{w|Exoplanets}} are planets outside of our solar system, and exoplanet astronomers are astronomers who attempt to discover and study such planets.

[[Megan]] is using a common exoplanet {{w|Exoplanet#Indirect_methods|discovery technique}} to discover a planet around a nearby star. When a planet passes between an observing astronomer and a star, the planet will block some tiny part of the light coming from that star, causing it to appear dimmer for some amount of time. The {{w|Kepler (spacecraft)|Kepler telescope}} used this technique to find evidence for exoplanets.

But here Megan is standing on the surface of the Earth at night, looking at the ground, and therefore presumably looking in the direction of the sun. By observing that it is completely occluded at night, she correctly concludes that the Sun is orbited by at least one planet: the Earth. This is obviously an absurd usage of that method. Reasons include the fact that exoplanets are not big enough to block out all of their stars' light when seen from Earth,{{Citation needed}} making what Megan says a massive understatement, and that the period of the brightness oscillations would correspond to the length of a day, not a year as it would for exoplanets.

The title text alludes to using more complicated techniques to observe light reflected by small planets like the Earth, for example by detecting {{w|Methods of detecting exoplanets#Polarimetry|polarized light}} reflected from the planet's atmosphere. In some sense, observing the light that reflects off of the Earth during the day is in fact how we see everything around us. It also implies that astronomers, who because of their career choice are more likely to work at night, might be completely unaware of Earth's existence in the daytime and thus surprised to "discover" it from their nighttime work.

The title text may also be a reference to [[1231: Habitable Zone]] where an astronomer is messed up by someone who puts a mirror in front of the telescope.

More details at: {{w|Methods of detecting exoplanets}}.

==Transcript==
:[This panel is white on black, instead of black on white. Megan is standing staring at the ground.]
:Megan: Based on this decrease in the star's brightness, I believe it is orbited by at least one planet.

:[Caption below the panel:]
:Exoplanet astronomers at night

{{comic discussion}}

[[Category:Comics with inverted brightness]]
[[Category:Comics featuring Megan]]
[[Category:Astronomy]]
[[Category:Exoplanets]]