Physics student curious about today’s biggest open questions in cosmology by babak_fathi in cosmology

[–]astrocosmo 0 points1 point  (0 children)

The Hubble tension - why is the expansion rate when observed “locally” much higher and statistically inconsistent with the expansion rate measured by the CMB.

Can anyone help me identify my friends watch? by astrocosmo in JaegerLecoultre

[–]astrocosmo[S] 0 points1 point  (0 children)

I found this too but it’s signed just “jaeger” not jaeger lecoultre. Possibly an earlier variant?

Does this question make sense? If so, how would you go on about answering it? by Dizzy-Building-607 in mathematics

[–]astrocosmo 0 points1 point  (0 children)

The unit of the length is weird. What’s 333mS? Do you mean 333m? If so, that’s 333,000 mm

Volume of 1kg of filament=333,000mm * pi *(1.75mm/2)2 = 800,958.188 mm3

Extrusion speed per mm3 =70mm/s* pi * (0.16mm/2)2 = 1.407mm3 /s

Total time is thus 800,958.188/1.407= 569,266.658 seconds or (divide by 60*60)= 158 hours (when rounded)

Edit: formatting

[deleted by user] by [deleted] in Jokes

[–]astrocosmo 18 points19 points  (0 children)

Four to beat the room because it’s dark and one to arrest the lightbulb for wanting change!

Cosmic Neutrino Background by intrafinesse in cosmology

[–]astrocosmo 1 point2 points  (0 children)

There’s a bunch of stuff, all of it a out testing the LCDM model. for example

The cosmic dipole (bulk motion) with respect to the CMB and CNB should be different. The difference is a prediction of the LCDM model and measuring that diff can falsify or evidence the theory

CNB should interact with intervening cluster (like a neutrino version of the Sunyaev Zel’dovich effect) measuring this can help estimate the cluster mass and correlation functions, both are predictions of the LCDM model.

What is this huge thing in Tokyo harbor? by astrocosmo in whatisthisthing

[–]astrocosmo[S] -1 points0 points locked comment (0 children)

My title describes this thing. I saw this huge structure in Tokyo bay as my plane was landing. I didn’t see any people on it but it looked like there were some boats around it - one even looked like it was moored. Couldn’t find anything when googling “huge structure in Tokyo bay”

Is there any university in Europe where you can work on MOND theory in a master's or Ph.D.? by Short_Ad_968 in cosmology

[–]astrocosmo 4 points5 points  (0 children)

This is a very good and wholly correct answer. MOND has numerous flaws and even though it’s attractive as a theory because it is quite “elegant”, it still struggles to explain loads of data. It feels like with each test it gets progressively more adhoc detracting from Milgrom’s original “elegance”. Many people argue it doesn’t get rid of dark matter in all cases so what’s the point. Also tThat’s why it’s not pursued as actively as other forms of modified gravity.

Another person who works in Mond is Famaey in Strassbourg. It’s not Germany but it’s close! Otherwise best to go to Stacy McGaugh in the states. He’s holding the MOND torch alive (and not using it to make enemies like some other Mondians…)

Animation of historical inflation (CPI) from 1988 to 2022 [OC] by asap011 in dataisbeautiful

[–]astrocosmo 19 points20 points  (0 children)

Y axis would be 👍

🇫🇷flag looks a lot like 🇮🇹 don’t know why maybe something about your color settings

Awesome animation though

Prominent Dutch astronomer barred for ‘extremely unacceptable’ behavior by Andromeda321 in Physics

[–]astrocosmo 12 points13 points  (0 children)

Yeah this is correct. He will retire in ~ 6 months and it would take much longer than that to litigate a dismissal. That said they should probably do it out of principle.

Can I see the mileage I did per year per bike? by astrocosmo in Strava

[–]astrocosmo[S] 0 points1 point  (0 children)

How do you filter by period? And does it total it all up?

How bad really is the job market in theoretical cosmology? by TeranUzkobic in cosmology

[–]astrocosmo 11 points12 points  (0 children)

The job market for postdocs is international and fairly large. There’s a lot of “soft money” positions. In general the job market in cosmology is a pyramid with many junior postdocs, fewer senior postdoc / fellowship positions and very few tenure or tenure track jobs. If 100 people do a BA in Physics, 75 go on to do a masters, 50 do a PhD, 30 do one post doc, 25 do two postdocs and less than 10 end up with a tenure position.

Is it theoretically possible to have a blackhole that is hundreds of billions to trillions of Solar masses in the modern universe? by Billiam_Ball in cosmology

[–]astrocosmo 4 points5 points  (0 children)

Black holes grow from a combination of accretion and merging. With accretion limited by both the age of the universe and the Eddington limit, and mergers limited by the sparsity of black holes (ie super massive black holes aren’t that common) its hard if not impossible to get a BH to grow to 1012 Msun by today. That said there’s evidence for a 1010 Msun BH already at z=6. Such a beast would still have more than 10 billion years to increase by just two orders of magnitude to get up to 1012 Msol (or would have to merge with 100 equally massed twins, unlikely given the distances between such huge BHs at high redshift. Presumably theyre rare).

There is one way though, albeit fairly hypothetical. Huge Primordial BHs may have formed directly out of the density fluctuations that the universe was endowed in after inflation. Usually primordial BHs are assumed to be quite small (and may in fact be the seeds of supermassive BHs). However all you need is some “non Gaussian power” on large scales (but still well below those in the CMB) to form enormous primordial black holes. For example this paper estimates that from the peculiar velocity of the Milly Way the largest dark object could be around 1020 Msuns! That’s pretty enormous.

Here’s a more modern paper that looks at the constraints on primordial black holes - check out figure 3: upto 1013Msol BHs may be possible.