Angular Diameter Turnaround
Angular Diameter Turnaround
[Cueball and a row of 7 spiral galaxies, the first 5 growing sequentially smaller and the last 2 growing larger] Angular Diameter Turnaround [A spiral galaxy emitting light and Cueball in a small circle with closely spaced grid lines, captioned "T=1b yr."] [A stretched truncated circle with widely spaced gridlines, with the galaxy at one side and Cueball on the other, and light following a curved path through the stretched space to Cueball, captioned "Now (T=13.8b yr.)". Cueball is thinking "Big!"] Illustrated using phones instead of galaxies (Brightness and redshift adjusted to keep phones visible) Things that are far away look smaller, but things that are really far away look bigger , because when their light was emitted, the universe was small and they were close to us. [numerous iPhones scattered in space, with numbers visible on their lockscreen. The closest is brightly lit and says "13 billion years after the Big Bang" on the screen. Subsequent phones behind this one are smaller, fainter and more red, until they reach "3" (the rest of the text is too small to read). From this point, the phones grow larger, although they continue to get fainter and redder. Subsequent phones show "2", "1", "500 million", "200 million", "50 million", "20 million" (which is larger than the original "13 billion years after the Big Bang" phone) and a very large, faint phone so big that only the word "thousand" is visible, with the rest of the screen obscured behind other phones or so large it extends off the panel]

This comic references multiple physics and maths concepts, including Angular diameter , Angular diameter distance , Redshift , and mobile phones , although mobile phones are not a core science at this time. [ citation needed ]
The comic shows the galaxies of the universe as Samsung Galaxy mobile phones, pairing the age we see them at from earth, the degree they are redshifted, and how much of the sky they take up, known as their angular diameter. The mobile phones that are closer and older have depleted batteries, whereas the batteries are full for those phones from which the light is still only beginning to reach us. This is how galaxies appear in the sky if they were phones that had batteries lasting billions of years, the light reaching us from deeper into the past as it comes from objects that are farther away. Phones at a low battery may be a reference to 1373: Screenshot , where Randall commented that it is hard to pay attention to any phone with a low battery as the need to charge it is so urgent.
An important takeaway from this comic is that the events that occurred at the very start of our universe are etched in our sky as if they are still happening now , in a detailed faint timeline, that we are still learning more and more from.  Using the mobile phone metaphor helps as, when the technology space was young and smaller there were mobile phones , such as the original iPhone ,  which one might still remember despite there being many more recent and better ones in a more crowded market space.
Randall's intent appears to be to highlight how just a few very distant galaxies occupy incredibly large proportions of the sky and are seen as they were at a very young age. Mobile phones have this similarity, of massive presence, relatively early stages of new technology, and bringing information from far away.
The large galaxies can be seen in dark red in the background as if the unimaginably ancient child galactic bodies are looming forebodingly behind everything else. The title text refers to galaxies falling into a pool of dilute blood as if the void beyond were hell.  This completely misses the point as to what redshift is, being an effect on the wavelength of light, rather than light being filtered through regions of infernal suffering or far galaxies being stained by the blood of the enemies of Android phones.
This physical concept has a lot of juxtaposition of things that usually contradict, and Randall has put energy into attempting to highlight that.
Katie Mack tweet: https://twitter.com/AstroKatie/status/1516548836709343238
Spacetime diagram possibly has reasonable visualizations of the kinds of relations bodies have when they are moving this far apart, including angular diameter distance. Simultaneity no longer exists at such distances. Distance is debated too, although that would be a different article.
[Cueball and a row of 7 spiral galaxies, the first 5 growing sequentially smaller and the last 2 growing larger] Angular Diameter Turnaround [A spiral galaxy emitting light and Cueball in a small circle with closely spaced grid lines, captioned "T=1b yr."] [A stretched truncated circle with widely spaced gridlines, with the galaxy at one side and Cueball on the other, and light following a curved path through the stretched space to Cueball, captioned "Now (T=13.8b yr.)". Cueball is thinking "Big!"] Illustrated using phones instead of galaxies (Brightness and redshift adjusted to keep phones visible) Things that are far away look smaller, but things that are really far away look bigger , because when their light was emitted, the universe was small and they were close to us. [numerous iPhones scattered in space, with numbers visible on their lockscreen. The closest is brightly lit and says "13 billion years after the Big Bang" on the screen. Subsequent phones behind this one are smaller, fainter and more red, until they reach "3" (the rest of the text is too small to read). From this point, the phones grow larger, although they continue to get fainter and redder. Subsequent phones show "2", "1", "500 million", "200 million", "50 million", "20 million" (which is larger than the original "13 billion years after the Big Bang" phone) and a very large, faint phone so big that only the word "thousand" is visible, with the rest of the screen obscured behind other phones or so large it extends off the panel]
