We Can't Explain Spiral Galaxies - The Winding Problem

For some recent review articles on spiral galaxy structure see:

00:00 Introduction
03:16 The discovery of spiral galaxies and the winding problem
07:29 Density wave theory
08:57 Stochastic Self Propagating star formation (SSPSF)
10:39 Swing amplification theory
12:49 Why none of these ideas explain spiral structure fully
19:44 Bloopers

Video filmed on a Sony ⍺7 IV

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👩🏽‍💻 I'm Dr. Becky Smethurst, an astrophysicist at the University of Oxford (Christ Church). I love making videos about science with an unnatural level of enthusiasm. I like to focus on how we know things, not just what we know. And especially, the things we still don't know. If you've ever wondered about something in space and couldn't find an answer online - you can ask me! My day job is to do research into how supermassive black holes can affect the galaxies that they live in. In particular, I look at whether the energy output from the disk of material orbiting around a growing supermassive black hole can stop a galaxy from forming stars.

[michael.a.covington]

I'm so old that I went to a lecture by Bart J. Bok -- over 50 years ago -- and he put up a slide of NGC 4038/NGC 4039 (the pair in Corvus) and described it as "two spirals having a fight of some sort." I've never forgotten that phrase, nor the slight Dutch accent in which it was delivered.

[nkronert]

I'd say that the easiest way would be to observe galaxies in detail over hundreds of millions of years. That will surely make everything clear 😊.

[PaulGAckerman]

In this episode Dr Becky becomes Dr Seuss. One spiral, two spiral, red spiral, blue spiral.

[MrVontar]

Traffic jams are actually caused by cars following too closely, so whenever a car merges or switches lanes, if there isnt enough space then it causes the cars to brake. Then since there is a limit to how much space you may gain back, the cars cant accelerate to make up for the lost time. In fact, since the cars do end up trying to make up for the lost time, instead of fixing the problem by leaving 20 feet between vehicles, they actually make it worse because now they have to constanly stop as they reach the vehicle in front of them. Then they must break again, so each series of breaks is like a traffic jam. In general, if you actually have to break in a traffic jam then that means you are going too fast most of the time.

[PersonalStash]

My old boss used to say, "You don't tell them what you can't do", or in your case, don't know. Just make something up until you figure it out, like you always do.

[oldguysrule]

Enjoyed the traffic jam analogy. Very helpful. Had not thought of spiral arms as anything other than an actual structure

[martynspooner]

I cannot even tell anybody how much this complete layman enjoyed this episode. Thankyou.

[erikdevereux]

I had Alar Toomre for MIT course 18.03 Differential Equations in spring 1982. It gave me a huge jolt to see his work on galaxies cited here! I remember well Prof. Toomre showing us videos of galaxy collision simulations that explained the formation of elliptical galaxies. Thanks so much for this!!

[stephenwatts]

I have a busy lifestyle. Lifelong interest in astronomy, but do not have the time. Dr Becky allows me to keep up with the amazing stuff. The universe is incredible. Thanks Dr Becky.

[paulkinzer]

It's pretty clear that this topic excites you, Dr Becky. And your enthusiasm is infectious. Thanks, as always, for packing so much into such a short time.

[cabbage]

I tell you, if my teachers made physics as fun as you make astronomy, I'd have taken that instead of biology. Your excitement and curiosity is infectious.

[marknovak]

Spiral galaxies are a sign we still have much to learn about the universe.

[markharwood]

Brilliant. Dr. Becky's enthusiasm really is infectious.

[jaimecastells]

Thank you Dr. Becky! More please, ma'am? Seriously, your in-depth understanding of this topic begs for a series of deep dives. Pretty please?

[ptimal]

There's an overwhelming pull to ponder the nature of the universe. All of the different galaxy forms, it's amazing. Reminds me of maybe looking at the many different versions of cat, or particle, or molecule.

[finlandtaipan]

What is funnier than a "messy" looking galaxy? A "Messier" object of course. Ok, that was my daddy joke of the day.

[backwashjoe]

Haven’t seen DrBecky this animated with her hands in a long time! Love the passion and enthusiam! :)

[inquisitivedelamorean]

I love the background setup. And very engaging video too... structures of galaxies have always fascinated me a lot. Thank you.

[FandangoJon]

I could sit and listen to several more hours of this topic and love every minute of it. More, please! Spin away! 😵‍💫

[zen]

One of your best videos ever! Amazing ideas and theories - and beautiful galaxies too. Please make a 6 hour video just slowly showing hundreds of beautiful spiral 😊