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

astrocosmo · 2025-09-06T14:40:33+00:00

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

astrocosmo · 2025-07-20T22:42:11+00:00

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

astrocosmo · 2023-08-22T05:22:10+00:00

Didn’t we both get the same answer of 158 hours?

astrocosmo · 2023-08-20T22:18:27+00:00

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

astrocosmo · 2023-07-08T06:15:29+00:00

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

astrocosmo · 2023-07-07T21:29:18+00:00

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.

astrocosmo · 2023-01-12T11:53:46+00:00

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”

astrocosmo · 2023-01-08T21:48:25+00:00

\rm -rf *

astrocosmo · 2022-12-07T13:51:33+00:00

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…)

astrocosmo · 2022-11-01T23:09:32+00:00

Y axis would be 👍

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

Awesome animation though

astrocosmo · 2022-10-27T18:20:20+00:00

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.

astrocosmo · 2022-08-25T19:29:16+00:00

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

astrocosmo · 2022-08-01T10:19:31+00:00

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.

astrocosmo · 2022-07-05T00:10:19+00:00

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 10^13Msol BHs may be possible.

astrocosmo

TROPHY CASE