5 upvotes, 3 direct replies (showing 3)
/u/NikoSarcevic, my friend had an interesting question i couldn’t answer: is there a “minimum distance” required to see strong lensing effects? and could one ever see lensing effects with the naked eye? i studied lensing for a total of 2 weeks and the equations in my notes didn’t illuminate me lol. thanks!
/u/cosmo-ryan, what’s the current status in the hubble constant “crisis”? thanks!
/u/neildymium, how can i get started with machine learning and cosmology? i’m out of astronomy, but if i was interested in building a side project, let’s say. thanks!!
Comment by cosmo-ryan at 15/07/2022 at 23:15 UTC
4 upvotes, 1 direct replies
The Hubble tension is still as tense as ever!
We still don't have an agreement between early-time measurements of the Hubble constant and late-time measurements, and everyone's pretty sure that their measurements are accurate -- so something somewhere needs to give. Some recent research has said that changing physics at late times cannot resolve the tension, and similarly other research claims that changing physics at early times also won't resolve it. So it's got to be some new physics across both early and late times, or some systematic errors that we aren't aware of.
Gravitational waves are potentially the difference maker. We can measure the Hubble constant at late-times with them, and we expect their systematic errors to be independent of all other kinds of measurement. If we can produce an accurate GW measurement of the Hubble constant, then that should hopefully resolve things once and for all, but that could be a few years away yet!
Comment by neildymium at 16/07/2022 at 18:15 UTC
4 upvotes, 1 direct replies
Thanks for the question! I'd say the most accessible place to start with machine learning and cosmology is N-body simulations. These are large lattice simulations that are essentially virtual boxes with millions of particles in them, and the motion of these particles is calculated using state of the art code and machines. Using these simulations, we can make a lot of predictions about what the large scale structure of our universe should look like, and there are so many other useful applications.
The nice thing is that there are a lot of publicly availably N-body simulations that you can start working with right away! One project that comes to mind is CAMELS[1], I've included a link there to their home page, and here is a link[2] to their documentation.
1: https://www.camel-simulations.org/
2: https://camels.readthedocs.io/en/latest/
There is also a lot of machine learning applications in Astronomy, which more and more with time is entering an era of Big Data, and machine learning will be an essential tool for processing all this data. A great place to start with this is the Sloan Digital Sky Survey (SDSS)[3]. They host one of the world's biggest photometric catalogs of the night sky, and it's all publicly available for use. Hope that helps!
Comment by NikoSarcevic at 16/07/2022 at 20:35 UTC
4 upvotes, 0 direct replies
Hi!
I have to admit I need to look up more about your questions. I would say there has to be some limit since it is a geometrical thing in its core. I do not work in strong lensing so I will ask around and let you know. Fantastic questions all around!