Astrophysicists Put All Objects in Universe into One Pedagogical Plot

https://www.sci.news/astronomy/all-objects-universe-pedagogical-plot-12372.html

by bell-cot • 3 years ago

46 19 3 years ago

bell-cot• 3 years ago

"Everything" in the universe, ever, on a lovely Size vs. Mass log-log plot. Sci News' article is quite brief - check the American Journal of Physics article, linked at the end, for more.

wanderingstan• 3 years ago

The article: https://pubs.aip.org/aapt/ajp/article/91/10/819/2911822/All-...

Jun8• 3 years ago

“Humans are represented by a mass of 70 kg and a radius of 50 cm (we assume sphericity)” - classic assumption!

checkyoursudo• 3 years ago

Humans are growing generally more spherical, so the assumption is becoming more reasonable over time.

simonh• 3 years ago

Very nice. There was a gorgeous visualisation of the universe in terms of distance scale on Kottke a few days ago.

https://www.pablocarlosbudassi.com/2021/02/the-infographic-a...

Y_Y3• 3 years ago

Units of mass used: gigaelectronvolts (implicitly times c²), solar masses

Units of length used: centimetres, megaparsecs

When measuring the whole universe it's hard to pick a scale. Anyway astrophysicists are the worst for this. The rest of science is happy with SI(, or sometimes naturalized units when you're doing theory and dealing with integer qualities and numbers that you don't care about). But in astrophysics brightness is measured on a scale set by one of the Ptolemys looking at stars and literally eyeballing it. They'll measure mass in terms of energy, energy in "ergs" and do some godawful mix of imperial, metric and miscellaneous that makes electric charge something comparable to square root of energy times length.

pavel_lishin3• 3 years ago

Their car gets 40 rods to the hogshead, and that's the way they like it.

tzs2• 3 years ago

s/cars/container ships/

40 rods to the hogshead is 0.00198 miles per gallon (or 504 gallons per mile). Actually that is low even for a container ship but it is at least in the same ballpark.

I prefer to give fuel efficiency in fuel used for a given distance rather than distance for a given amount of fuel.

My car's fuel efficiency is 23 picoacres or 9.3 picohectares.

hirundo• 3 years ago

Why is it "Forbidden by Gravity" but the "sub-Plankian unknown"? I thought that the Plank length was a hard limit like the speed of light. Is that not true, and there theoretically are unknown features smaller than that?

icegreentea2• 3 years ago

Plank length is not a hard limit the same way speed of light is. Plank length is where we expect our current models to start producing nonsense, though we fully expect that 'things can happen at smaller than plank length'. The expectation is that there exists some future model that produces meaningful predictions at sub-plank length.

Whereas for speed of light, we currently expect no future models to produce meaningful faster than light predictions, and we fully expect to never find evidence of faster than light predictions.

codezero• 3 years ago

I studied physics (I wasn’t very smart) but it surprised me that the charge radius of protons and neutrons are smaller than that of electrons! Cool plot.

Also the paper this is from is linked at the bottom of the article but here’s a link: https://pubs.aip.org/aapt/ajp/article/91/10/819/2911822/All-...

Astrophysicists Put All Objects in Universe into One Pedagogical Plot

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