Editing 2643: Cosmologist Gift

{{comic
| number    = 2643
| date      = July 8, 2022
| title     = Cosmologist Gift
| image     = cosmologist_gift.png
| titletext = These neutrinos were freshly produced by a local source just 8 minutes ago
}}

==Explanation==

This comic shows a box labeled to indicate that it contains 30,000 fresh {{w|neutrino}}s and four zeptograms of {{w|dark matter}}. The box is intended as an inexpensive gift for a {{w|cosmologist}}. The gift giver didn't put those things in the box—both are simply passing through it, so the "gift" consists of exactly what was in the empty space it occupies. While the caption suggests this would be a good gift for a cosmologist, what they or anyone else would do with such a box is uncertain.

There are about a billion neutrinos per cubic meter throughout space, produced during the {{w|Big Bang}}.[https://physics.mit.edu/news/journal/physicsatmit_14_conrad/] However, the flux of "freshly produced" {{w|solar neutrino}}s at Earth is around 6.5&times;10<sup>10</sup>/cm<sup>2</sup>/s, yielding about 2.1 million per cubic meter, and implying the box is around 12 liters, three quarters as big as a typical {{w|breadbox}}.

Four zeptograms is a minuscule mass, equal to four sextillionths of a gram, the mass of about 200 carbon-12 atoms or around 20 to 23 {{w|amino acid}}s. There is an estimated 0.011 to 0.016 {{w|solar mass}}es of dark matter per cubic {{w|parsec}} local to the solar system,[https://iopscience.iop.org/article/10.1088/1361-6633/ac24e7/meta] or about 900 zeptograms per cubic meter, suggesting the box is closer to 4 liters. This discrepancy [[2035: Dark Matter Candidates|could imply Randall agrees]] with cosmologists who believe dark matter is partially composed of {{w|primordial black hole}}s,[https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.120.121301][https://www.sciencedirect.com/science/article/abs/pii/S2212686418301250?via%3Dihub][https://news.yale.edu/2021/12/16/black-holes-and-dark-matter-are-they-one-and-same][https://iopscience.iop.org/article/10.3847/2041-8205/823/2/L25][https://iopscience.iop.org/article/10.1088/1475-7516/2010/04/023] instead of being composed entirely of ubiquitous subatomic particles. This comic coincided with the [https://www.nasa.gov/image-feature/goddard/2022/nasa-s-webb-delivers-deepest-infrared-image-of-universe-yet first James Webb Space Telescope science image release to the public] containing {{w|gravitational lens|gravitationally lensed}} very distant {{w|quasar}}s and {{w|population III star}}s, the spectra of which can be used to test [https://twitter.com/SheerPriya/status/1546576050976870400/photo/1 certain hypotheses associated with dark matter being black holes.] A billion neutrinos have a mass of only about 2×10<sup>-12</sup> zeptograms, at about 0.1 {{w|electron volt}}s each.

The "local source" mentioned in the title text is a joke about the commercial value of fresh, locally produced items, but the comic means that the neutrinos come from the Sun. It takes solar neutrinos slightly more than 8 minutes to reach Earth once they're emitted, roughly the same time as photons take to make the trip. (This doesn't include the [https://en.wikipedia.org/wiki/Radiative_zone approximately 170,000 years] that energy takes to get from the Sun's core, where the fusion reactions occur, to where photons are emitted at its surface.) However, as the neutrinos are not slowed down inside the Sun and travel at about 99.9999999999% of the speed of light, they will have aged by less than a millisecond,[https://www.omnicalculator.com/physics/time-dilation] and so are technically even fresher than indicated.

==Transcript==

:[A picture of a box with writing on one side. The box's lid is slightly hanging off the right edge of the box so you can see inside. The inside of the box is black.]

:30,000 neutrinos
:<small>Freshly produced</small>
:Plus 4 zeptograms 
:of dark matter

:[Caption below the panel]: 
:Cosmologists are easy to shop for because you can just get them a box.

{{comic discussion}}
[[Category:Cosmology]]