Cosmic Distance Ladder: Other Challenges and Methods

To complete this series on the cosmic distance ladder we discuss some of the further challenges associated with light extinction and propagating errors in measuring distance. We also discuss how the use of other measurement techniques can help us gain confidence that all of our measurement techniques are actually correct.
Let us know what you think of these videos by filling out our short survey at tinyurl.com/ast.... Thank you!

[@neoloaded]

Thanks for posting this content. Wherever you are now, hope you are resolving deeper mysteries of the Universe.

[@mihaivisovan2407]

This was a great series! I came from studying astronomical distances on a course on brilliant and I wanted to go more in depth.
This was very clear, concise and well explained.
Keep going!

[@MrBebopbob]

Excellent series. Thank you.

[@PhysicistMichael]

For stars in the mid to outer parts of spiral galaxies it can take hundreds of millions of years to go through a full orbit, so this is really to slow to see in pictures.
However, we can look at the Doppler shift of stars on either side of the spiral; one side should be moving away from us, one side should be moving towards us, and this difference (and how it changes as you look at points further and further from the galactic center) gives us a good idea of the rotation rate.

[@MoshkitaTheCat]

Very helpful thank you very much for your hard work.

[@joaquinfabrega]

Great videos, I noticed the last video was around 9 years ago, I hope the author is well.

[@PhysicistMichael]

Thanks! The author is well and hopes to get back into producing new content hopefully over the summer (though I admit that's been the hope for a couple summers). At the very least, I'm planning on posting the session recordings I made for an online intro astronomy class last fall.

[@PhysicistMichael]

To answer your first two questions, I'm currently working on my doctoral thesis. As for whether that is all, I'm going to start posting more videos starting.... now

[@fredrickihlberg]

There's one thing I just can't get my head around. Maybe you can help me out here. When we measure distances, the result we get; is that the distance at this very moment or at some other time? The galaxy has had time to move far far away since the light that we see was emitted, not to mention the streching of space. The billions of years makes distances relative rather than absolute I feel.

[@paul1964uk]

How can you tell how fast (what is the period) a galaxy is rotating though. Is it by studying the appearance of spirals in their images?