Talk:2643: Cosmologist Gift

- The explanation mentions “Eight zeptograms” although Randall’s box says “4 zeptograms of dark matter.”

- The 4,800 daltons in the explanation is roughly the size of a small protein; for example, insulin is about 5,800 daltons.

- Randall’s box says it contains 4 zeptograms of dark matter. Could someone explain this? My incomplete (biologist’s) understanding of dark matter is that astrophysicists do not yet know what it is. So how could Randall claim the box contains 4 zeptograms of it?

Thanks!

Fixed; thank you. 172.70.210.125 01:18, 9 July 2022 (UTC)

Here's a more recent PBH DM source than those already cited which could comport with Randall's 0.4% DM particles implication, but doesn't do so explicitly. 172.70.206.213 02:35, 9 July 2022 (UTC)

With the math corrected per 162.158.134.89 below, the figure is 34% ubiquitous particles. 172.70.211.36 09:44, 9 July 2022 (UTC)

And this comic was the perfect birthday gift for me. 108.162.245.203 02:42, 9 July 2022 (UTC)

• How was the 23,000 neutrinos/m³ figure obtained? A flux of 7e10/(s·cm²), or 7e14/(s·m²), at a speed of close to 3e8 m/s, gives 2.3e6/m³. That would correspond to a box size of about 0.013 m³, or a bit larger than a typical shoe box. 162.158.134.89 07:19, 9 July 2022 (UTC)

Corrected. 172.70.211.52 09:40, 9 July 2022 (UTC)

To note {and I've summarised in an edit) that photons from the Sun can have been travelling for 100,000 years from its core to space, before their 8ish minute trip to the box (assuming you let them in, e.g. leave the lid off, or filter out all but the hard X-rays/etc), whilst neutrinos hardly notice so are 8 or 9 minutes old (before being adjusted for time dilation) regardless. And you can still put as much lead-lined wrapping paper on your present as you want, to keep it a surprise! 172.69.79.211 14:45, 9 July 2022 (UTC)