Editing 2707: Astronomy Numbers

{{comic
| number    = 2707
| date      = December 5, 2022
| title     = Astronomy Numbers
| image     = astronomy_numbers_2x.png
| imagesize = 593x315px
| noexpand  = true
| titletext = I adopted a cat that weighs 12 solar masses. Laser pointers love chasing it.
}}

==Explanation==
{{incomplete|Created by a CAT-LOVING LASER POINTER - Please change this comment when editing this page. Do NOT delete this tag too soon.}}
Space is big.  Vastly, hugely, mind-bogglingly big,[https://www.goodreads.com/quotes/14434-space-is-big-you-just-won-t-believe-how-vastly-hugely] and the things that are in space can also end up being very big themselves. As a result of this, most quantities in astronomy can vary by huge scales. For example, Earth has a mass 10^23 times more than the average human, and the Sun is 10^5 times more than that, which itself is 10^12 times less massive than the Milky Way. The same applies to speeds, distances, and time, which can often be measured in terms of light speed, light-years, and millions (or even billions) of years. Because of this, it's a truly unusual occurrence for anything in space to end up in the fairly narrow range of scales of mass, size, speed, or time that humans can easily grasp.

Ponytail, a scientist apparently researching something related to Earth's orbit, remarks that she finds it “suspicious” when reasonably human-scaled numbers come up. She then extends this paranoia to things that should be measured in regular numbers, such as the weight of cats. The vet (Megan) is seemingly used to this problem (perhaps she gets a lot of physicists) so restates the 12 lb weight of Ponytail’s cat in solar masses, which sounds more correct to the astronomer.

Although the Earth's orbital velocity around the Sun is far above any "normal" scales (around 30 kilometers per second or 108,000 kilometers per hour), Earth has a pretty circular orbit around the Sun so most of this speed ends up being tangential (sideways) rather than radial (towards or away from) the Sun, which is the value relevant for Ponytail's calculations. On January 1, Earth's radial velocity is close to its smallest value because we reach our closest point to the Sun in the first few days of January each year (in 2023, it happens on January 4) so by January 1, it's nearly come to a standstill before it starts traveling away from the Sun again. On the other hand, by April 3, 2023, Earth will be receding from the Sun by almost 500 meters per second or 1800 kilometers per hour, a slightly less normal speed for the average person to encounter in everyday life.{{citation needed}}

65 miles per hour is approximately equal to 105 kilometers per hour, although the even more typical scientific value (in {{w|International System of Units|SI}} derived units) would be 29 meters per second. 3 × 10^−30 solar masses is approximately equal to 6 kilograms or 13 pounds (consistent with the 12 pounds, or slightly under 5.5 kilograms, of the original figure) and is normal, if perhaps slightly overweight, for a cat.

The title text suggests that laser pointers "love chasing" a new cat with a weight of 12 solar masses (an inversion of the typical cat behavior of [[729: Laser Pointer|chasing laser pointer dots]]). 
All gravitational fields bend light towards their center, a 12 solar mass object would bend quite a lot.  A Laser pointer pointed at such a cat would bend towards it or "chase" it.  In fact, 12 solar masses, would have a Schwarzschild radius of around 36 kilometers, so a regularly sized cat that size would very definitely be a black hole, drawing all light within 72 kilometers around it into its singularity.

Another interpretation of the title text is that Randall has (presumably) accidentally adopted a distant star instead, which astronomers usually take a liking to pointing laser pointers at during both star parties & normal parties they were unwisely invited to. Assuming Randall's 12-solar-mass cat goes through similar life cycles to a 12-solar-mass star, his cat will probably end up living a violent, short life of just a few million years before expanding into a red supercat and exploding as a feline supernova, which might explain why astronomers are so interested in pointing it out.

==Transcript==
:[Ponytail is standing in front of a whiteboard writing on it with a pen, while Cueball looks over her shoulder from behind her. On the board is an almost circular ellipse with a cross that centers on a dot towards the left side of it. On the right side there is a small circle on the ellipse's line. There are several lines of wiggles representing unreadable text. To the left of the ellipse there are two lines near the top of and four near at the bottom of the ellipse. Ponytail is writing a fifth line below these almost under the ellipse. At the bottom to the left there is a rectangular frame with a line of text beneath it and at the bottom left corner there is a line forming a half closes rectangle around two dots.]
:Ponytail: …And we need to correct for our elliptical orbit. On January 1<sup>st</sup>, Earth will be approaching the sun at a rate of ...let's see...
:Ponytail: 65 miles per hour.
:Ponytail: Weird. Okay.
:Cueball: Weird?

:[Ponytail has turned towards Cueball, the pen is no longer in her hand and the white board is no longer shown.]
:Ponytail: I get suspicious whenever I see a normal number in astronomy. We're not supposed to have those. Feels wrong.
:Ponytail: Scales should all be incomprehensible.

:[Megan in a lab-coat raised her hand palm up towards an animal carrier cage standing on her desk. The cage has a handle and five air holes are at the top. Behind two of them something black inside the cage can be seen. Ponytail is standing on the other side of the desk looking at Megan. Above the top of the panels frame there is a panel with a label:]
:Earlier, at the vet:
:Megan: Your cat weighs 12 lbs.
:Ponytail: Ridiculous, nothing weighs "12". You must mean 10<sup>-20</sup>? Or 10<sup>40</sup>?
:Megan: Fine. Your cat weighs 3x10<sup>-30</sup> solar masses.
:Ponytail: Okay. Better.

{{comic discussion}}

[[Category:Comics featuring Cueball]]
[[Category:Comics featuring Ponytail]]
[[Category:Comics featuring Megan]]
[[Category:Astronomy]]
[[Category:Cats]]