A Small Universe

https://arxiv.org/abs/2309.03272

by bookofjoe • 3 years ago

50 23 3 years ago

arxiv.org

hprotagonist• 3 years ago

where “small” here means the many trillions of stars in the observed universe.

pdonis• 3 years ago

Yes, still very big. You might think it's a long way round the corner to the chemist, but that's just peanuts to space.

zuminator4• 3 years ago

More or less, although the paper is talking about somewhere between "a few times larger than the currently observable size" (p.3) to "not more than a few orders of magnitude larger" (p.6) Either of which counts as "small" in comparison with the generally infinite size implied by current solutions of our flat curvature models.

(Totally unrelated question: How are you getting proper open-closed quotes?)

causality02• 3 years ago

generally infinite

How infinite is "generally infinite"? Are we talking infinite enough it's not productive to talk about its size, or so infinite there are physical copies of the solar system, earth, and everyone it it by sheer chance?

virtualritz• 3 years ago

Totally unrelated question: How are you getting proper open-closed quotes?

On a Mac you have them on some keys by holding down a modifier.

On Windows and Linux you need to use a utility of some sorts or modify key bindings for your desktop environment.

On Android you hold the resp. quote key on the virtual keyboard to get a selection of resp. quotes to choose from.

On that note: a good typographer will use single quotes for quoting ‘single’ words.

checkyoursudo• 3 years ago

“On my Mac, Swedish keyboard, it is option-shift-n and -m to get these quotation marks.”

Otherwise, the shift-2 quote marks are " straight. Mac English surely has them somewhere, but not necessarily those keys.

If you have linux, then you can use the compose key, like this (according to the internet, my linux box is 1000 km away right now so can't test)

[Compose] < " for “

[Compose] > " for ”

No idea about Windows.

tebruno99• 3 years ago

If you do not want to use key combinations all the time, and just want real quotes always.

macOS latest: Settings -> Keyboard -> Text Input area, hit edit next to input sources "use smart quotes and dashes", you can turn it off or choose which quotes you want to use.

previous macOS: Settings -> Keyboard -> Look around in here, there is a smart quotes & dashes or Replacements area you can choose the real quote characters.

anon____• 3 years ago

The galaxy is on Orion's belt.

aylmao• 3 years ago

This reference took me back, it's been a minute hahah

lainga• 3 years ago

One may also read https://phys.org/news/2023-09-case-small-universe.html to get an overview of what the mentioned "swamplands programme" is

zuminator4• 3 years ago

Nice summary, although it has a rather glaring "thinko" in an early paragraph, where it points out that, because of the age of the visible universe being around 13 billion years, a naive calculation of the universe's diameter would be 26 billion light years across, but that because of cosmic inflation, it's "46 billion light years across [sic]." That should be ~46 bly in radius, in other words, ~93 bly across.

mika69• 3 years ago

I never heard of the term 'swampland conjectures' before.. Any resources to dive in to this topic?

jug• 3 years ago

https://en.wikipedia.org/wiki/Swampland_(physics)

DrDroop• 3 years ago

I never heard of this either, seems like very speculative stuff, but interesting non the less: https://indico.in2p3.fr/event/24773/contributions/110484/att...

No idea what this tower of light is they keep talking about.

m3kw92• 3 years ago

It’s weird how they gauge big or small because what do you compare to the largest thing ever(excluding numbers to say this is small or large?

jakeinspace• 3 years ago

If I were still in middle school, I’d give you the perfect comparison point. Ostensibly I’m a mature person now.

qup• 3 years ago

that comparison point is getting pretty mature now, too.

zing

m3kw92• 3 years ago

Do it!

andrewflnr• 3 years ago

Small compared to infinity, mostly. Or maybe compared to the observable universe, i.e. how much stuff exists that we cannot see versus how much we can?

A Small Universe

Related Stories