We Can't Measure* Distance In Outer Space!

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Then watch my next video early: nebula.tv/videos/scienceasylu...
We can't measure the distance to astronomical objects directly, so we have to be creative. That's why we need the cosmic distance ladder. It's a serious of techniques we use to calculate astronomical distances indirectly.
Nick Lucid - Host, Writer, Editor, Animator
Em Lucid - Producer
Nora Bailey - Researcher, Fact-Checker
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VIDEO ANNOTATIONS/CARDS
Black Hole Misconceptions:
• What Most People Get W...
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RELATED KZbin VIDEOS
SciShow Space on Distance Ladder:
• The Cosmic Ladder That...
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HUGE THANK YOU TO THESE SUPPORTERS
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SOURCES
Radar Ranging:
doi.org/10.1016/0019-1035(73)...
ilrs.gsfc.nasa.gov/science/sc...
Parallax:
doi.org/10.1167/9.1.10
sci.esa.int/web/gaia/-/53278-...
www.esa.int/Science_Explorati....
doi.org/10.3847/1538-3881/aacb21
Cepheid Variables:
astro.wku.edu/labs/m100/PLrela...
www.atnf.csiro.au/outreach/ed...
doi.org/10.17226/9585
doi.org/10.1086/126870
Type 1a Supernovas:
arxiv.org/abs/0705.0726
doi.org/10.1086/186970
doi.org/10.1146/annurev.aa.30...
arxiv.org/abs/1608.04192
Cosmological:
astro.ucla.edu/~wright/CosmoC...
arxiv.org/abs/astro-ph/9905116
doi.org/10.1093/astrogeo/aty268
iopscience.iop.org/article/10...
arxiv.org/abs/2208.13642
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LINKS TO COMMENTS
• JWST had a Turbulent H...
• JWST had a Turbulent H...
• JWST had a Turbulent H...
• JWST had a Turbulent H...
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IMAGE/VIDEO CREDITS
Apollo Retrorefector:
commons.wikimedia.org/wiki/Fi...
www.nasa.gov/image-article/re...
Deep Field Flythrough:
svs.gsfc.nasa.gov/31035/
Gaia Animation:
www.esa.int/ESA_Multimedia/Vi...
Milky Way (Artist Rendition):
images.nasa.gov/details/PIA10748
Type 1a Supernova:
svs.gsfc.nasa.gov/13852
commons.wikimedia.org/wiki/Fi...
Barred Spiral Galaxy (NGC 1300):
images.nasa.gov/details/GSFC_...
Redshift Cube:
svs.gsfc.nasa.gov/14105/
Redshift Zoom:
svs.gsfc.nasa.gov/14301/
Galaxy GLASS-z12:
commons.wikimedia.org/wiki/Fi...
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TIME CODES
00:00 Cold Open
00:22 Introduction
02:05 Radar Ranging
04:17 Inverse Square Law
04:57 Stellar Parallax
08:46 Standard Candles
10:58 Cepheid Variable Stars
12:58 Type 1a Supernovas
15:15 Cosmological Redshift
18:37 Summary
19:44 Nebula Ad
20:52 Outro
21:05 Featured Comment

[@ScienceAsylum]

Get Nebula for 40% off with my link: go.nebula.tv/scienceasylum Then watch my next video early: nebula.tv/videos/scienceasylum-this-important-principle-is-always-explained-wrong

[@aaronmicalowe]

Light trying to get to us as space expands is like swimming against the current as you try to get to an island.

[@ZX81v2]

You two work well together :)

[@gabrieltelleslinsgoncalves6836]

Great theme.

[@trevinbeattie4888]

Thanks for the reminder, Nick. I’ve been subscribed to Nebula for a while, so I added your channel just now and am looking forward to your next video right after I finish the latest one from Extra History. 😊

[@ffggddss]

Note about the Correction: This is due to the stellar magnitude of an object being greater when the brightness is lower, which is counterintuitive until you realize what was meant by "magnitude" when its use for stars was invented. The number isn't the amount, it's the rank. "Stars of the first magnitude" meant the brightest ones; "Stars of the second magnitude" meant the next brightest ones; etc. Once instruments came along that could measure amounts of light, we could make stellar magnitudes into numbers with fractions, not just integers. The format of this video is perfect. You get discussion and reaction and interplay of ideas. Splendidly done, both of you! Fred

[@ElectroBOOM]

This was illuminating! Thanks!

[@ScienceAsylum]

Thanks Mehdi!!

[@totrantien]

Hi Medhi and Nick , let's you guys collab about the Peltier cooler, how it works at quantum level? @ElectroBOOM @ScienceAsylum

[@oliviervancantfort5327]

Especially the standard candles 😂

[@CliffSedge-nu5fv]

Many candela of illumination!

[@priyanshuprakhar5517]

Pun intended...😆

[@paradox7358]

"Space is big. Really big. You just won't believe how vastly, hugely, mind-bogglingly big it is."

[@lococomrade3488]

I once heard it was like.. literally physically impossible for humans to even be capable of thinking of both *the infinite* and literal *nothingness.* I have no proofs or references for this statement.

[@aaronmicalowe]

RIP Douglas Adams. Went far too young.

[@robo7856]

Like minecraft innit

[@alexpotts6520]

I mean, you may think it's a long walk down the street to the chemist's, but that's peanuts compared to space.

[@sirartichokedarlingtonbanf1892]

Not bad for a Golgafrincham B Ark descendant. o7

[@angryginger791]

It's so awesome to have a partner who likes listening to you nerd out and actually takes an interest in the things you love.

[@47f0]

Over half a million subs? He pays her.

[@ScienceAsylum]

@@47f0 I'm sorry that your marriage is so empty that you think I have to pay my wife to be a quality partner 😢

[@47f0]

@@ScienceAsylum - Nah. I just think you're lucky enough to be married to someone smart enough to get paid.

[@jayde4872]

@@47f0dude, why are you acting like blud can’t find love? Quit being a hater.

[@47f0]

@@jayde4872 - My wife loves me. When my back was blown she tied my shoes. When she helps me on one of my accounts, she gets paid. It's not that freaking deep.

[@andrewmat]

I'm always surprised about how big the universe is. "It is so far that distance doesn't make sense anymore" is mind blowing

[@metamorphicorder]

Thats what Douglass adams was trying to say.

[@Secret_Moon]

You might be more surprised. For context, let's say if the Earth was as big as a water molecule, then the observable universe was as wide as the Pacific Ocean... times 1000.

[@mrgalaxy396]

I don't really like that description "so far away it doesn't make sense". It's still the same concept of distance we always use, it's just that at after some point we can't reliably measure it anymore and we have to use other metrics that approximate what we want to know, which is the distance itself. That's what redshift is for. You can say it's hard to imagine things being that far away, but it doesn't stop making sense. M said it best, it's "far far away".

[@simesaid]

​​​@@mrgalaxy396well, yes _and_ no. Yes, of course we can approximate distances in space, and those distances do have at least some meaning to them. But then we can measure the velocities of certain objects also, but it's still not possible to say that some object has an _absolute_ velocity, to state that it is travelling at a _defined_ speed. This is because all _relative_ speeds are, as their title suggests, subjective in nature. And as such they hold no objective meaning. All velocities are relative. Ergo, talking about absolute velocities is meaningless. And so it is with distances. Beyond a certain point (determined by an observers light cone - as defined within special relativity), talking about absolute distances simply ceases to become meaningful. Or, in other words, distances become meaningless. As stated in the video, we can determine the redshift of light that has travelled to us from the very early universe, but this is a _relative_ measurement. It is observer dependent. For the light itself _no time whatsoever_ has passed since it began it's journey. _We_ see the photons redshifted, however, the photons do not see _themselves_ redshifted. Redshift is a relative phenomena. And as all relative measurements are subjective, rather than objective, in nature, measuring relative distances is ultimately as meaningless as measuring relative velocities. I remember feeling slightly sick when I first learned this. It was as though the floor had just dropped away... was _nothing_ really... well, real, I wondered? It's one of those cases where the more you know, the more you know you don't know, I guess. Sorry. Anyway, I'd still prefer to know that I don't know, rather than to remain ignorant even of my ignorance. As Aristotle apparently said shortly before he died, *"All I know is that I know nothing."* Anyway, have a great day!

[@billyswong]

@@mrgalaxy396 The suggestion that distance in the conventional sense no longer make sense, is that when light take so long time to travel from that star to Earth, we can no longer form a meaningful objective reference frame to put the Earth and that star in the same reference frame. We don't share the same clock. Our times don't tick together in sync.

[@markmidwest7092]

Your videos with you and your wife, the banter you guys have and the questions she asks, really are the highlight of my day. You guys are great together.

[@ScienceAsylum]

Thanks 🤓

[@marcon33]

She is nice!!!!

[@JohnVance]

This is just a fantastic way to learn, it's like hanging out with the friends who are smarter than you.

[@FullModernAlchemist]

I absolutely love how pragmatic her observations are. Like “stars existed back then why didn’t they name it standard stars?” That’s such a good point. 😂

[@angrymidget4728]

I absolutely LOVE these discussions! The questions she asks as a non-expert in your field really makes these videos feel more 'interactive' considering she is also acting as a sort of 'stand-in' for us viewers in 'real time'. I don't watch podcasts generally, but I would *sooo* watch one of you two as you guys discuss and explore each other's specialties/fields of expertise!

[@idontwantahandlethough]

oo you're totally right! Well said :)

[@Goku17yen]

very well put

[@christianosminroden7878]

This video shows once again that having a co-host or guest who is really smart, genuinely curious and generally knowledgeable but, due to their specialization in an entirely different field, has little to no idea about the topic at hand is always a huge plus for educational content. 😊

[@k-d-n]

This was very fun. I really like these conversations with Ms. Science Asylum.

[@mavadelo]

I love episodes where you explain things to your wife. Gives such a great vibe. Emily reacts with the things I would have wanted to ask. Much love to you both.

[@tmrogers87]

This channel is amazing. Nick is batting 1.000 on teaching me concepts in unique ways that provide huge insight other educators seem to take for granted. Love it!

[@ScienceAsylum]

Glad you enjoyed it! 🤓

[@kindlin]

I wonder if 1 other important part that I felt was only glossed over at the end, would help you. Namely, that none of these things is measuring a distance, not even RADAR. But even at the Type 1a scale, distances can be interpretation dependent, and each of the various methods has there own uncertainties. So, stating the measured value and while using what method is really the best way to talk about any of these kinds of things, and any kind of local distance, like kilometers or whatnot, is a simplification, tho useful in some contexts. This realization that nothing is a distance outside of very nearby astronomical objects was very eye opening to me. I think this was a Vsauce shorts video.

[@vladpetric7493]

I hope your chemistry is the same in real life, you two are lovely.

[@ScienceAsylum]

If soulmates exist, her and I are it.

[@jeff5683]

I think I love these videos because you are kindly explaining a complex piece of your mind with someone you love who hasn't been exposed to the knowledge you gained to build the understanding in your mind. It's unique, wholesome, and educational.

[@justalonesoul5825]

Erathostenes be like : "Young man, I kind of started all this astronomical measuring stuff more than 2000 years ago! Measuring Earth itself with shadows of a stick, and clever assumptions! A century you say... This is outrageous!" 😄 1st time viewer on the channel, very pleasant discussion, and thank you for the refresh on the topic 😊

[@JayKnight]

I really like this format, the "on the shoulders of giants" progressions, where you start where things makes intuitive sense and take the baby steps to reach the stuff that feels absurd.

[@jakebrookesactor]

I am an actor, and I was amazed at your presentation of distances. You have a great format of discussion. I mean, I couldn’t put my phone down!

[@KnowBuddiesLP]

Yay! An episode with M! Love the dynamic you two have and great way to deliver information, learned a lot this episode, haven't heard of half of the ways to measure before. Thanks for the lesson as always !

[@ScienceAsylum]

Glad you enjoyed it!

[@Schulstand]

Somehow I never encountered an explanation for jumping from paralax to cepheids and supernovae, this is the most helpful. Keep making those videos, they're the best at filling those gaps in a public/popular understanding of physics and astronomy

[@ffggddss]

A cool nugget on optical parallax of human eyes, which I've actually done, as a kid: If you get or make a periscope, you can use it to amplify your binocular vision by increasing your effective interpupillary distance. Just hold the periscope horizontally, looking into it with one eye while the viewing opening extends out away from the other eye. With both eyes open, you get enhanced depth perception! Thanks for another cool vid! Fred

[@david94549]

Interesting. How about using two periscopes, one for each eye 👁️😎👁️

[@ffggddss]

@@david94549 Much harder to keep the two images coalesced, and so, not worth it. Unless you go to more trouble to make the instrument into a single large piece, which will then need 4 mirrors altogether, instead of just 2. But you can get the same parallactic baseline either way, so long as the overall horizontal distance is the same, between the 2 "viewing apertures." Easier just to get a pre-made periscope and use it on one side.

[@david94549]

@@ffggddss yeah I was tired when I commented this last night, now I realise you can just use a longer periscope to further increase the depth perception

[@ffggddss]

@@david94549 Don't fret that; it was a perfectly reasonable suggestion, one that had occurred to me at the time, but that I just didn't have the materials or patience to implement. And I think that if you wanted to maximize the parallax amplification, that would be the way to do it. It would just be more trouble to build. I guess it would look somewhat like binoculars - at the eyepiece end, at least. And one really rigid bracket or beam to mount the 4 mirrors on.

[@jamesgornall5731]

Oh my God that's horrible, like having an eye on a stalk ffs I have to try it

[@limbridk]

I wanted Nick to tell her about the ant on the elastic, and how it gets to the end. When they were talking about light trying to get to earth but space was expanding.

[@DataIsBeautifulOfficial]

You lost me at Cepheid variables

[@j9dz2sf]

Some additional information is necessary. In particular, why the luminosity period is related to its absolute luminosity. Which physical phenomenon explains that?

[@ScienceAsylum]

@@j9dz2sf This was just a general overview. I plan on doing a couple deeper dives: one on Cepheids and one on Type 1a 👍

[@manskiptruck]

@@j9dz2sfit’s called the Leavitt Law. Basically, some awesome person Henrietta Leavitt was tasked with looking at light curves of these Cepheid variable stars and she noticed a relation between the period of the stars and the brightness

[@musashi939]

This one was completely new to me. The other steps before and after I was aware of. Although I thought the type 1a supernovae was the standard candle. Maybe I missed that part but the video made it like that the supernovae is already beyond the standard candle. But cepheid variable. Never heard that term before. Cool. At least now I have the whole laundry list of methods we know how to measure distance.

[@Secret_Moon]

@@j9dz2sf Well, without explaining the mechanism underneath, we can still easily calculate based on anecdotal evidence. We have many Cepheid Variables within the range of the Stellar Parallax. So by using the Stellar Parallax, we can calculate how far they are, and thus how bright they actually are. Using that, we can correlate between how fast they pulse and how bright they actually are. It's just lucky that from all the Cepheid Variables within the Stellar Parallax range that we measure this way, it shows these 2 factors do indeed correlate with each other, so this is proven. Then, by measuring how fast the Cepheid Variables beyond the Stellar Parallax pulse, we can reverse calculate how bright they actually are, and by comparing it with how bright the stars appear to us, using the inverse-square law we can calculate how far they are from us.

[@MrPooPooJohn]

These are my favorite episodes! You guys are great on camera together.

[@cubeflinger]

Husband and wife making measuring jokes. Immediate like

[@ScienceAsylum]

😆 We're such nerds.

[@cubeflinger]

@@ScienceAsylum beautiful nerds :)

[@CosmoTechChronicles]

Your attention to detail is remarkable. From the visuals to the audio quality, everything is top-notch. Your commitment to delivering a polished product really sets you apart. Kudos on the excellent production!

[@ScienceAsylum]

Thanks! I work really hard on these.

[@pathwaytousername]

I'm glad you explained each layer well enough for most people to understand. They all sound a lot simpler, and still somehow work!

[@ScienceAsylum]

It's one of the benefits of having my wife there 👍. My training is classroom teaching, where it's common to adjust in the moment based on immediate feedback. When I make a normal-style video, I have to guess and hope, which doesn't always work out.

[@geemcd]

​@@ScienceAsylum Guess and hope has resulted in some of the best science education on here! ❤

[@ScienceAsylum]

@@geemcd Thanks! My experience definitely makes me a better guesser. To be fair though, I do miss the mark _occasionally._

[@Hydroverse]

Nice to see you and your wife doing a video together. Great video!❤

[@ScienceAsylum]

Thanks 🤓

[@muhsin_5693]

Watching all the way from Nairobi Kenya 🇰🇪 … amazing work you guys are doing! Keep up the good work!

[@truthbetold2567]

The back and forth between you two make for my favorite shows.

[@skan5728]

Not sure I'm a fan of this scripted conversation format, although other formats would make the video unnecessarily longer

[@ScienceAsylum]

@@skan5728 These conversation videos are _not_ scripted.

[@suomeaboo]

I knew that the effect of parallax decreases for things farther away, but I never made the connection that depth perception also decreases. This channel never fails to give me new connections to things I already knew, and I love it very much.

[@Nefville]

Your wife is great, hope to see her back! I also wanted to mention how well this format works for educational content. I don't know what you call it, in the movies its the _fish out of water_ character but more specifically I would call it the teacher/ pupil format. If there is one way that helps me understand complicated topics where I cannot readily ask a question myself, this is what works the best.

[@j_mase]

It is so great to be reminded how intelligent humans are, even back when we were using the parallax method for measuring. Your explanation of how we are now able to obtain distances beyond our galaxy cluster was enlightening! Thank you! On another note, I’m going to start using the standard redshift distance numbers to let my friends know when I might arrive when making plans 😂😂🤓

[@axel07121]

I wish i had a science teacher like you back in the days when I graduated from high school. You have an unique way to keep up the listeners attention and also explain complicated things very easy and understandable.

[@JeremyPickett]

"Starts to siphon off mass from their their companion", "Which one", "The white Dwarf". ...I love both y'all even harder.

[@DanielRichards644]

it's also worth noting that due to the ladder of calibration there is the potential for stacking tolerance issues (like at which decimal point you stop at in a calculation of each rung on the ladder) that could potentially invalidate every "measurement".

[@euromicelli5970]

Well done! I’ve seen the distance ladder exclaimed a hundred times. Almost always some important detail is left out because the presenter instinctively thinks it’s obvious, but it’s only obvious if you already know it. This is one of the few times I’ve seen someone touching all the key points: how there is no way to measure directly and we need indirect methods. How each method has limits. How each method works. The _absolute importance_ of the range overlap between methods, so that we can calibrate each subsequent method by measuring the same-ish distance by both a shorter-range method we already trust, and the next longer-range method. The only nick-pick (no pun) I have is that you didn’t go into how we know about the cepheid variable period/luminosity relationship, which I think is a lot of fun.

[@ScienceAsylum]

Thanks for the high praise! Also, we did talk about everything in much more detail, but a lot got cut for time. I plan on doing a couple deeper dives: one on Cepheids and one on Type 1a 👍

[@aviecenna8579]

One thing I couldn't follow was the explanation for the red shift. I would imagine that, like brightness, you would need to know the original frequency of the light that was emitted to calculate how much it had red shifted. Did they also have a standard candle for red shift?

[@brothermine2292]

It left out how the diameter of Earth's orbit around the sun is measured. (6:59)

[@euromicelli5970]

@@aviecenna8579 you’re absolutely right. And we do have a standard candle for redshift because each chemical element emits precisely in the same exact colors, always and everywhere. This is actually trivial to do compared to cepheids variables. We take precise spectroscopic measurements; we see where the emission lines actually fall in the spectrum for these faraway objects, and we know where they are _supposed to_ fall (because “hydrogen always emits light like hydrogen does”), and so we literally calculate how much the observed spectrum needs to be shifted back towards the blue until it matches what is supposed to look like

[@euromicelli5970]

@@brothermine2292 oh, you’re right. But I suspect that’s a whole video on its own

[@MurseSamson]

Always great to see you two talking, great educational video as always. ☕ Appreciate you Nick!

[@Krish-jm6ve]

This video is abridged and concise version of a 2+ hr video. SO much content squeezed without any deviations. Well Done Sir !!!

[@ScienceAsylum]

Thanks! 🤓

[@potawatomi100]

Your lovely wife is a positive contributing 😊❤element to your programming. Emily Rocks!

[@ashutoshtiwari3129]

I love how the complexity level suddenly drops down to our casual approach of measuring distances.

[@upandatom]

I love this wife reacts series! I always learn so much from you guys :) And it's so cool to see how knowledgable you are Nick, totally unscripted, you just know so much!

[@ScienceAsylum]

Thanks Jade! Sometimes I feel trapped in my normal format. With these conversations, I get to let loose and nerd out.

[@potawatomi100]

Emily is a great addition. I very much like it when she contributed.

[@werdwerdus]

i love these explainer type videos with your wife. she is educated enough that you don't have to explain every little thing and you can focus more on the relevant information. keep it up!

[@arondaniel]

Love the episodes with your wife! She has the right level of knowledge & intuition to clarify these concepts.

[@chuckoneill2023]

Almost first. Lovely to see your wife in the episode. Your coupleness is adorable.

[@beckywaytoomuch]

Really happy to have found this channel. And thank you for the Nebula recommendation! Knowing there's an online community that talks about the stuff I think about, and in the way I think about it is so cool. Thanks for making content!

[@MiguelGarcia-zx1qj]

I knew (mostly) every think about the astronomical ladder, but I was delighted to listen to your explanation; very clear and very comprehensive 😍

[@GoldSkulltulaHunter]

Amazing video, as usual! Working from first principles to explain complex topics is always very satisfactory, and you've done it brilliantly.

[@MartiniFabio87]

M asks exactly the questions that I, as a non physicist, would ask. I love your chemistry! Keep up the excellent work!

[@apple54345]

I love this channel so much simply because I've watched you from your infancy and now to see how far you've come.. Just watching you I have such a proud grin on my face. I feel like a parent. Even though I've had no input in your success. You're great. I'll leave it there.

[@timlash]

Really nice video. Best description of the distance ladder I've ever come across. The collaboration with your better half was very effective! Thanks.

[@shocktocker8282]

You & Emily are awesome. Want to see more of Emily. I really ENJOY the science you teach, and the way you explain it makes it learn able and entertaining! Keep up the good work.

[@mrwillard95]

Your videos have always been great and I'm really liking the casual discussion/explanation of these topics you and your wife have. It makes the highly complicated information more digestable and less "intimidating" for laymen like myself.👍👍

[@ScienceAsylum]

Glad you like them! 🤓

[@calyodelphi124]

I couldn't wait to see/hear Nick bring up Cepheid variables! 😄Also, it's awesome to see Em tag team the outro! I love this format of one grilling the other on their chosen subject, and I think it'd be awesome to see Em nerding out about biology while Nick grills her on the chosen topic. 😉

[@lyledal]

These conversations are some of my favorite videos of yours! Thanks for them. They're REALLY helpful!

[@jonh8488]

This is the most interesting video you have published, and I have seen lots of your uploads :)

[@paulgee4336]

Thank you for doing this video. "Suddenly" it all makes sense. Now I can't both help but wonder why, and be "perturbed" about it, that this was never adequately explained in any of my astronomy courses, or in any books I've read. I guess I didn't read the right books.

[@richardcoppin5332]

Wow. You are probably the first science communicator I've heard that had stated so efficiently that the distance is the distance that the light had traveled.

[@richtheobald4390]

Really enjoyed listening to this! Great chemistry on camera with the two of you. Thanks!

[@vincentpinto1127]

Nice technical conversation! Well done to both of you!

[@ScienceAsylum]

Thanks!

[@dietricha.schmitz811]

LOVED this video. Best explanation I have ever heard of the whole subject.

[@johnmcnulty6171]

I love moments when I learn something profound that changes my perception of nature. So the distance we measure light travelling wasn't the actual distance of the object when that light started its journey - because of expansion. Seems so obvious, but that had never occurred to me before. And the way we calculate distances was fascinating to learn. Thanks Nick for expanding my world yet again !

[@patrickhayden7206]

I love watching you two together. As much as I love you in front of your bookshelves. Seeing things like the Shadowrun books and gaining a little insight on you. Have you considered more videos of the two of you playing off each other? Maybe adding clones of your wife with your clones ;-). Great video.

[@saelesbonsazse9919]

You're amazing. Your wife is amazing. You both make us feel part of the conversation! Thank you a lot!!

[@HossLUK]

This may be one of my favorite science videos I've seen. I already knew the majority of this stuff separately and relatively knew how they work, but i always got confused when it came to understanding them collectively and how they all apply to one another. This video essentially just bridged the gap of my knowledge and understanding that i was lacking in order to actually understand it. Thank you very much for making this amazing video. You certainly earned my subscription.

[@ScienceAsylum]

Glad you enjoyed it.

[@peterp-a-n4743]

_Stellar_ work, Nick! This was really exciting and informative!

[@ScienceAsylum]

Thanks! 🤓

[@X3MgamePlays]

This is a perfect video. Everything got covered. Everything got linked. AND, you mentioned that galaxies where closer than the light shows. This is something that a lot of other scientiests forget to mention and thus the viewer thinks the distance in light years was the actual distance. Finally someone mentioning that this is only the distance the light has crossed. Cheers

[@ScienceAsylum]

Glad you liked it 🤓

[@PollyMatthew]

That was one of the best explanations of the subject, or similar related ones, I’ve seen in a long time. Made me so proud of science, rational thinking, knowledge and understanding.

[@eigenchris]

Great video! I particularly liked the Cepheid variable section as I wasn't too familiar with how those worked. Neat to see how it "stacks" on top of stellar parallax.

[@ScienceAsylum]

Thanks! 🤓 I thought it was an important video to make.

[@michaeljoefox]

9:36 I love how he starts talking thinking he’s going to argue then realizes he’s talking to his wife and knows better. Thank you Em, this made my night.

[@Billy_Bad_Ass]

Wouldn't a really long ruler work (preferably marked in metric)? It might take a few years to measure out a parsec, but I think I could do it.

[@ScienceAsylum]

The mass of that ruler would get big pretty quick, like to the point that it has its own gravity and is no longer reliable.

[@o11k]

@@ScienceAsylum Just use carbon fiber bro

[@canuckprogressive.3435]

@@ScienceAsylum It would turn into a spherical ruler, right?

[@wally7856]

@@canuckprogressive.3435 ... and then eventually a black hole

[@benjaminnevins5211]

Gravitational slide rule? That would be a science project @@ScienceAsylum

[@Mr.Unacceptable]

The trip is not frustrating for the photon. The trip is instant, traveling at the speed of light. but mostly because photons don't have feelings.

[@michaelblankenau6598]

How can it be instant when light still travels at a specific speed ?

[@Mr.Unacceptable]

@@michaelblankenau6598 Relativity. The same way the guy on a train sees and hears differently than the guy standing still as the train passes. Moving at the speed of light means also there is no time. Very tough to get your head around. Keep thinking about it and you will eventually understand it. But a wise man once said if you think you understand it you really start to realize you don't understand it and it's true. You have more questions.

[@Jackiee_Chann]

Good to see another video from you Nick!

[@ScienceAsylum]

Workin' hard over here.

[@IllIl]

Why do I sit grinning at the monitor the whole time you two are chatting? This is such a fun format for going through topics. Thank you! Man, the point about the original distance being shorter than the distance the light travels completely blew my mind - had never thought of that! And that point about us already using time to describe distance ("20 minutes away") such a cool observation.

[@viniciusnoyoutube]

Explain how gravity works to her and us.

[@init_yeah]

Space expands faster than you can measure it 😊

[@ScienceAsylum]

True.

[@k39716]

I can say it again and again. Your way to explain and visualize is just simply THE. BEST. WAY for understanding. Thank you a lot!

[@playgroundchooser]

You two are so freekin awesome together! Love it! And I would watch a 2 hour video on the nuance of why Type 1A Supernovae are only "about" 1.4 SM. 😊

[@lordaizen8004]

You're wife is SOO witty 😂 hilarious 👍👍

[@brichan1851]

These videos are awesome. I love how informative every example is. Thank you for all of the work you do for us.

[@frederf3227]

This is an excellent format. Further your partner and you NAILED the questions AND answers each step of the way. I always thought when you're in the 50-100% of the size of the observable universe area in terms of distance just quote the fraction to the edge of the observable universe (or surface of last scattering or whatever). I know it's not linear but what you gunna do.

[@B_Van_Glorious]

You and Em saying Ahoy is the most stupid adorable thing. My wife and I watched it 3 times back to back just dying. You look like you can't help yourself but say it back, Nick, and I can respect that. You two are awesome. Keep doin you.

[@timmo971]

I like this new format… like just explaining something one on one. It works.

[@grovermatic]

Your extensive references in the doobly-doo are such a breath of fresh air!

[@ScienceAsylum]

You're welcome. I try to focus on actual scientific papers as much as possible.

[@NewJak14]

This was so well explained!!! Great work, thank you!

[@nickverbree]

Always love these more conversational videos!

[@QuadThumbs]

Absolutely fantastic Video! I really love the back and forth between you two!🎉🎉

[@AlexandarHullRichter]

I believe the reflectors we put on the moon are retroreflectors, like the ones that come on an ordinary bicycle, but bigger. They are geometrically designed to reflect any type of light back to the exact direction it came from, so you don't need as much light to be able to see them. The channel Technology Connections did a great video on retroreflectors.

[@zaugitude]

Great video! I knew the basic bits of using SCs and IA supernovas to measure distance but this really connected the dots. CheerZ!

[@hotflashfoto]

I like how the two of you interact so well and respect each other's intellect. Keep up the good work! And thanks for explaining why my ladder doesn't reach the roof without using radar, or something like that. LOL

[@canuckprogressive.3435]

That was really interesting. I knew most of it already but the part about red shift not giving the distance then or now but only the time of light travel blew my mind a little bit.

[@Jay_kay_bee]

Oh, i like this question and answer format!

[@Muhahahahaz]

I was vaguely aware of this before, but this is a great explanation! Now all the pieces make sense 😊

[@martifingers]

This could not have been better explained. Like being in the company of two very bright friendly people who care about knowledge and really want to share what they know or are discovering.

[@robertstrickland2184]

Thank you so much for this video. I would describe myself as passionate about space even though I don't have any formal training. This wonderful explanation of how we got the distance of space around us right and what we used and how we used it is awesome.

[@SSMLivingPictures]

This was a fun watch, you two are a great team.

[@martinheljedal7670]

Awesome! I've been wondering about this for a long time, thanks for a really great explanation!

[@calebcourteau]

I’ve been taught the wrung concept before, and understood it, but this was some amazing review. Probably the clearest presentation of these concepts I’ve ever seen.

[@personalaccount1515]

Normally I enjoy the content of the channel, but I especially enjoyed today's chapter. Thank you.