Open Questions in Astronomy - 15c - Intro to Astronomy Sessions
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- Опубликовано: 19 ноя 2023
- A VERY brief overview of just a few of the many open questions in astronomy.
Full Series Playlist: • Intro to Astronomy Ses...
Please note that this was designed as an introductory survey of astronomy course, mostly for non-science majors, and does simplify many of the topics accordingly. I encourage people who are just getting into astronomy to use this as a jumping off point for more in depth studies. I've tried to edit out specific references to my course (regarding assignments, tests, etc.) but I might have missed some. Finally, scientific fields are constantly advancing, with new data and studies resulting in our ideas being continually improved. This means some of the ideas presented here may soon be out of date, so I again encourage people to continue to investigate whichever topics are of particular interest to you.
Opening Image Credit: www.nasa.gov/feature/goddard/...
That anisotropy coming form galaxy spin axes aligning reminds me of how magnetic moments of iron atoms form magnetic domains in a bulk (non-magnetized) metal. There is clumping, but overall pointing randomly.
Ultra-diffuse galaxies (if that's really what they are) being a thing seems to support dark matter vs its alternatives, like modified gravity
Kind of bonkers that we've peered so far to the early universe yet our own sun still have secrets we do not yet know...
Same feeling when I read that the formation of lightning is still not fully understood
When you rub a balloon on your head and it makes your hair stand up... we don't really have a good model for why that happens (specifically why some materials are better at holding onto their electrons & removing electrons from other materials). There's quite a lot that you would think we've got covered, but we really don't.
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What is your favorite way to explain to your students why the universe seems classical to us yet on a subatomic level, « spooky » phenomena kick in like superposition and entanglement. Thank you very much.
I’m curious, what is your opinion on the status of physics (can be Cosmology, QM/GR, etc)? Sean Carroll recently made a 4 hour podcast called the Crisis in Physics, in which I would summarize his argument to be that there are open questions but there is no crisis in any area of physics. Some of the greats in physics believe there is some big gap in our understanding (Einstein, Dirac, Penrose, Smolin, etc).
Whether you call the state a crisis or open questions or business as usual (having questions and working to answer them) I think is more a question of personal temperament and marketing (note that I titled the video "Open Questions..." but maybe talking about a crisis might drum up more interest; not judging that fact, it's true even at scientific conferences). However, I would point out two things.
First, having these open questions and data that doesn't exactly fit all our models is one of the main things that drives scientific advancement. If everything was working, that would lead to stagnation and no further progress would or could be made. If we want our models to improve we need to have data that is not sufficiently explained by our current models. So this isn't an inherently bad thing.
Second, we only know about these gaps because of the advancements in both the observational and theoretical sides of physics. Ten years ago, we didn't have the problem with the Hubble constant, because we didn't have the high accuracy data to demonstrate that there's some disagreement in the varying methods. We need to look closely before we can find the cracks in our understanding, and then investigate further to determine whether those cracks are superficial or if they run much deeper. Either way, this is again how science advances.
@@PhysicistMichael Thanks! And I agree the word “crisis” is a bit dramatic. A better question might be: Do you think our main models of Cosmology, Matter, etc. need tweaks or an overhauls Did you see the somewhat recent interview of Jim Peebles on Brian Greene’s Channel? Considering Jim won the Nobel Prize in large part due to his lambda CDM model, I was pretty shocked to hear Jim say near the end of the interview that he encouraged students to try to come up with new models of space and matter. That sounds like a major overhaul to me.
@@timjohnson3913 I haven't had a chance to see that particular interview, but those teachers/scientists that I consider to be good will encourage others to try to find errors in current models and revise/replace them with better models, even if it overthrows a model that they developed.
I don't know if a tweak or overhaul would be needed, and I generally try to avoid making guesses unless I have a solid reason to back up my guess. However, we've come an incredibly long way in developing overarching models (QM, GR, statistical mechanics, etc.) that describe an incredibly wide range of phenomena with great success. If it's a major overhaul, it would still need to simplify to the same predictions that we get for ordinary systems in ordinary situations. And maybe that'll happen (it did in the early 1900's when the same could be said about how well classical mechanics was holding up, except for these little questions about black-body radiation and the speed of light).
But in order for that to happen, we really need more observational/experimental data. That's what the next (and final) video in this series is going to be about.
On the ultrahigh energy cosmic ray problem, is it possible that its interaction with the CMB somehow saps the energy from the CMB and boosting its own energy?
And the interaction of CMB with general free flying charged particles feels like something that can have an effect elsewhere
Interactions with the CMB should tend to remove energy from the cosmic rays. If the cosmic rays gained energy, that would run into some issues with entropy. If I have a system with a high energy density (the cosmic rays) interacts with a system with a low energy density (the CMB) energy will tend to dissipate to the lower energy system (this is glossing over some of the details of the 2nd law of thermodynamics, but approximately applies here)