The Star That Can't Exist
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- เผยแพร่เมื่อ 16 พ.ค. 2024
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The cosmos is littered with blue and red stars... but curiously no green ones. Why? Is this a fundamental constraint or merely an unlikely outcome? And what would it mean for humanity if we ever did detect a green star? Join us today as we explore this simple question with major implications.
Written & presented by Prof David Kipping
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::Music::
Music licensed via Creative Commons (CC) Attribution License (creativecommons.org/licenses/...)
► Brad Hill - Of Love and Loss [open.spotify.com/album/2oDAnU...]
► Joachim Heinrich - Cassiopeia
► Falls - Life in Binary
► Chris Zabriskie - Cylinder Five
► Falls - Ripley
► Indive - Trace Correction
::Film/TV clips used::
► Contact (1997) - Warner Bros. Pictures
► Avengers: Endgame (2019) - Walt Disney Studios Motion Pictures
::Chapters::
00:00 Prologue
00:59 The Dearth of Green Stars
05:25 Sponsorship
06:28 The Blackbody Approximation
10:51 Entering the Multiverse
13:04 The Viridian Flash
14:46 A Green Technosignature
18:37 Concluding Remarks
19:27 Outro and credits
#NoGreenStars #Technosignatures #CoolWorlds - วิทยาศาสตร์และเทคโนโลยี
Thanks so much for checking out our video, and thanks to our sponsor - head to www.Brilliant.org/CoolWorlds to learn more. Do you think civilizations might engineer the very stars themselves like this? Let us know down below, along with any other topics you'd like us to cover in the future.
IF enough copper could be added to the photosphere, would it radiate a greenish color? We live in a infinite universe, but our minds are infinite too. I'm sure it could be made, given enough resources?
Is there a way of artificially altering a star to become green? Maybe through adding an extra element? Removing an element? etc
Thanks so much .Thought experiments make physics more accessible to everyone.
We would have to be a type 3 civilization to manipulate/engineer stars. Don't you think? But who knows what we might be capable of in the far future.
Copper sulphate burns green but that would dissociate in a star!
There’s a really rare possibility for a single green star to spawn in the game Stellaris. There’s even a dedicated mention by the science vessel that finds it, calling it an impossible anomaly
Love me some Stellaris, excelent easter eggs
Stellaris is such a great game!
Diplomatic alert 🚨 war protocols initiated
A game?
This is a solid science video and some folks chime in with games?
@@dantyler6907 A game made by absolute science nerds, yes
I'm an art student and have never been very science savvy, but there's something about the content here that genuinely makes me want to learn. Thank you professor Kipping and team, you guys are fantastic communicators.
Considering you failed chemistry, art might be a better option
Snd u might never will🙈🦧🙉
@@yz250ftony Except yellow is one of the primary colors, not green, an art student should've noticed that. I'm surprised no one noticed that, maybe I'm the idiot here.
Given the fact that science is a part of everything, including art
@@yz250ftony tbf he got better at it, kinda
If I had a science teacher that came close to having as much enthusiasm as you I'd be a physicist today. Teachers should all teach like this. They should inspire a sense of wonder and deep thought. Keep up the great videos!
Then go be a teacher… talk Is cheap
@@kelly8431 Nah. Society is brutal on teachers. Who wants to handle that?
@@kelly8431 Yeah.. except I was only exploring a theoretical possibility that was completely separate from this reality. Fact is at 30 years old I don't think a career change with a pay cut would make much sense. Hence what I said. Unless you might have a time machine I could borrow?
Teacher in Training here. Sadly, in most modern societies, education simply doesn't have much time for this kind of in-depth analysis, speculation and discussion... I would LOVE to dedicate whole lessons to sidetracks like this, but the truth is, the curriculum is too overloaded to do so. I would be a BIG fan of cutting the curriculum down, trimming the fat so to say, so teachers have more time to discuss other interesting phenomena in class.
@@thegamesforreal1673 This is a part of why, despite being super interested in military history, and that I love explaining and showing that history to others, I don't want to be a teacher per se. Ironically, it is also a huge part of why I am such a history nerd, because my teachers would touch on subjects like Napoleon or Caesar, and I, wanting to know more, explore the internet for as much info as I can.
I'd like to argue that the green star technosignature would only work if alien civilizations had the same three cones, R, G, and B as us humans do. It's not guaranteed that they observe the same portion of the visible light spectrum as us.
I think the point is that regardless of how they perceive it (or if they perceive it--or indeed, what they call it) the electromagnetic wavelength of the light that we call Green (900 nm as stated in the video) cannot be a natural emission from a star, thus it's a techno signature if that wavelength is made overwhelmingly observable to distant observers. We can't perceive x-rays directly, but we can measure them and manipulate them, meaning an advanced civilization could do something similar even if they can't perceive the same visual space that our eyes can.
@@whyte2wolfI’m not following. I thought the video essentially said that stars with peak radiation at the green level exist (at 5500 degrees or whatever it was) but…
due to the shape of the black body radiation curve, even though the peak is at green light, you get so much blue/ red light ALSO that our brains see it as white. In other words…there are green stars out there, humans just see them as white stars due to the way we process combinations of spectra of light.
So imagine aliens w: brains that processed light differently - say they amplify the peak spectrum and de-amplify weaker spectra (so they’d have no concept of ‘white light’…wouldn’t they see plenty of ‘green’ stars?
@swainscheps In theory yes but as we've learned some theorys can be really hard to prove lol
@@swainscheps (Sorry if I got this all wrong I'm not smart when it comes to these things)
A star gives of multiple wavelengths of light wich our bodies percieve as white. If an alien species percieved this as green then the star would still be emiting the same amount of wavelengths. But if we encased a star to give of green light it would only be that certain wavelength of light. So the aliens would still be able to recognize that this is unnatural because a star simply can't emit that singular wavelength of light. It doesn't really matter what color it is percieved as since it is the wavelength that would be measured. (I don't actually know if it works this way but that's what I got from the video)
@nordiclight8453 pretty much the same thing as if someone is colar blind. Its a different color but its still the same thing. So they might see something else but for us it would still be green and for colorblind it could be red
The moment when a human being says something can't exist naturally, that's when the universe is like, "challenge accepted"
Call me silly/random,
but i just want to do my fellow Science-Lovers a Favor,
so excuse the Randomness but here you go,
have some warm Recommendations, cause the Learning never Ends!
-Veritasium.
-Oversimplified!
-It’s ok to be smart.
-Professor Dave Explains.
-Practical Engineering
-Michio Kaku.
-Kosmo.
-Legal Eagle.
-Cinema Therapy.
-And the arguably Best for Last: Hbomberguy! (The best at being Unbiased on all of YT.)
@@slevinchannel7589 merci
THANK YOU!!
@@slevinchannel7589 Hbomberguy is lame.
@My names Jeff
Lol, what?
I dont think he ever mentioned Religion on his history-channel?
The fluff?
Are we talking about the same channel, even? ??
Somewhere Kermit is sadly singing 'It's not easy being green'.
And the uk prime minister quoted him in a un conference... That is the definition of sad...
Ah how to make a green star, Kermit is singing twinkle twinkle little star.😂
Prof Kipping... Your story writing, narration and presentations are a magical gift of education to the public. Sincere gratitude to you sir.
Excellent video greatly enjoyed. I'm aware that purple/violet stars are highly unlikely due to both the extreme heats required, alongside the weakness in the human eye in seeing the violet spectrum, although it would be interesting to see if a ridiculously hot star could produce that colour.
I agree!
I wonder if a young neutron star could look violet, if you were close enough to look past the glaring jets and whatnot. But then again, you probably wouldn´t want to be that close to a neutron star. It´d probably fry you.
Actually, green can be quite nauseating. Once worked on a simulator. In testing the displays, we had people sit in front of a display as it was cycled through all the color combinations. Green actually made people feel nauseous. Now, in nature, we tend to like green. This is an interesting situation. Perhaps the green on the display was more intense and "pure". Don't really know.
Well, people do turn green when nauseous.
Eva Green is a star ;)
Green stars exist. Hollywood is filled to the brim with them. They´re the dying stars feeling jealous of all others...
because the green on your screen is so artifically fake compared to the real thing that it makes you nauseaus
Maybe green colour is not the problem, but with brightness added it could be.
Fascinating, being a former seafarer the “green flash” was often talked about. Now I understand it. Thank you.
Ive seen it too.
I've seen it from about 100 ft above the water on a cruise ship. Yet I fly often and in the many sunsets I've seen from altitude, often over land, I've never seen the flash there. I've also never seen it from the surface looking out at the water. I believe height has something to do with it.
It signals when a soul comes back to this world from the dead.
I really enjoyed this one! One thought when you had asked why an alien civilization might want to create a green star was that it might be useful as a light-house, a way to identify which star is 'home'. If a civilization could create such a megastructure, it might also be able to travel far from their home star, in which case, having a stable and easy way to pin-point where they are, and the way back, might be worth the investment for them. Maybe other techno-signatures exist that are easier, and cheaper to create. What's the cheapest and easiest one to create?
radiowave. you need to ask another question: What's the cheapest and easiest usable one to create?
Well, a civilization so advanced it can create a green star will probably have the technology to navigate in space without the need of "lighthouses" to show them where they are?
@@ztevie.j One day if their technology shrinks because of war or so. In Stories their Star could be passed down.
The smart civilization must have taken that possibility into considerance.
Such a cool thing to think about. I love the comment sections of these videos almost as much as the videos themselves.
QEC beacons. Use quantum entanglement to punch a hole through space faster than light and send a single through that is picked up by something as simple as a radio. Not cheap or easy to create, but a civilization that can master quantum entanglement can probably afford to create thousands easily.
What no one ever addresses is that our perception of a star's color is based entirely on the light frequencies our eyes absorb. Eliminate the red-absorbing cones, and the coolest stars we could see (yellow/orange) would appear green. Go the other way and eliminate the blue-sensing cones, and the hottest stars would appear green. Add a new color in near-ultraviolet, and we would no longer see blue stars as anything but white.
Learning about space, is what makes me smile, and Cool Worlds have the best ones.
I agree
Try melodysheep
Agreed. If I'm stressed I listen to one of these videos. Chill voices and smart info!
@@gabrielecoco5588 melody sheep is awesome!
Came here because Cool Worlds is the best. Left super happy to have discovered Melodysheep.
This technosignature was featured in Ken MacLeod's novel Learning the World, where humanity has cloaked so many stars in swarms of green habitats that to alien observers, they appear green and more and more do so as humanity's bubble expands.
Thanks for the recommendation! Just started reading the sample and it looks epic 👍
Same thing with Alistair Reynold's Galactic North, but the situation there is far more dire!
Any relation to Kevin MacLeod?
Also alluded to in several of Stephen Baxter’s books, most notably “Time.”
Loving the sci fi recommendations! 👍🙏❤️
This man is built like a tank, but has a soft and tender voice
Saw this video in the suggestions last night, added it for my watch later to catch today. The quality of the content alone give me no choice other than to subscribe. TH-camrs like you are rare, so worth to keep an eye on! Keep up the brilliant work! :)
The path down the color wheel (as temp goes up) was brilliant. Thanks!
Let's take a moment to appreciate that David gives us this amazing quality content for FREE.
... what, do you think they should charge us for it like some two-bit, profiteering corporation? the thing about information and facts is that they're supposed to be shared freely and without expectation of personal profit. that's what i do.
being that this is rare these days, i too agree with you. i thank this channel for its lack of commercialism. but they do fund this channel through t-shirt sales and, i'm sure, other products. but i can live with that. as long as they don't force commercials on me like so many other youtube channels do.
@@taylorbrock4635 ... uuhhh, ya, there is. they can profit all they want but they have no right to STEAL my money. they can steal your money instead.
but guess what. it doesn't work that way does it? when gullible, pro-corporate automatons like you allow the oligarchs to steal from you; you're allowing them to steal from me. actions have consequences and the consequenses of your gullible apathy is that I AM HARMED! and i don't appreciate that.
Nothing is free
@@darrenasquith1170 ... nothing is free under capitalism. yet, nothing costs anything in nature. go figure.
@@cjmacq-vg8um no shit? Lol what a fucking obvious statement to make.
New sub, glad this popped up as a suggested space video. The temperature vs color wheel was really interesting and although I can't do those formulas I understood by the shifting of the graph that green would be close or impossible to achieve. Thanks for the content! Great job!
Welcome to Cool Worlds
Exceptionally good and high quality video. This lecture blew my mind to bits. I need some time to recover and digest after this one.
Lots to love about Cool Worlds ! But for me it's the genuine humility shown by David , and the utmost respect he shows to his listeners ! One of the very best TH-cam channels !
P.S. That's not to mention the very high quality and creative standards he shows in his professional career !
Thinkers like David are much needed !
Call me silly/random,
but i just want to do my fellow Science-Lovers a Favor,
so excuse the Randomness but here you go,
have some warm Recommendations, cause the Learning never Ends!
-Veritasium.
-Oversimplified!
-It’s ok to be smart.
-Professor Dave Explains.
-Krimson Rogue.
-Practical Engineering
-Michio Kaku.
-Kosmo.
-Legal Eagle.
-Cinema Therapy.
-And the arguably Best for Last: Hbomberguy! (The best at being Unbiased on all of YT.)
Keep it up David, your work is amazing and inspiring.
Cheers 👍
See, this is why I love your channel so much, Prof. Kipping! You're out here answering questions I didn't even realize I had. Every video you upload takes me on such a journey
Call me silly/random,
but i just want to do my fellow Science-Lovers a Favor,
so excuse the Randomness but here you go,
have some warm Recommendations, cause the Learning never Ends!
-Veritasium.
-Oversimplified!
-It’s ok to be smart.
-Professor Dave Explains.
-Krimson Rogue.
-Practical Engineering
-Michio Kaku.
-Kosmo.
-Legal Eagle.
-Cinema Therapy.
-And the arguably Best for Last: Hbomberguy! (The best at being Unbiased on all of YT.)
your explanations and delivery is incredibly interesting and relaxing!! definetly subbing
Honestly you're an inspiration. Can't wait until I finish my own PhD and run a side youtube channel for informational videos and podcasts as a professor! Cheers!
Hey you don’t need to wait until you finish your PhD!
@@CoolWorldsLab that is true, and ideally I begin now instead of leaving it for the future. But right now it's a lot of work writing papers and taking courses, and I think it's better if I prioritize my degree. Either ways, this was an intriguing video, love your content!
yes, boring jabberman is so insire. let's all go take out loans to avoid having a real job so we can be grad students!
@@sumdumbmick What are you saying, being a proffesor isn't a real job? I'm not a student but getting a PhD is not easy lol, why are you assuming these people are "lazy"...
To Mick: Perhaps you are not aware that many doctoral students DO work to help them to survive and achieve their goals, whenever they can. Some can get teaching assistant positions, grants, or any type of part-time job(s) to help financially, or maybe a small loan to help. People who can even qualify for acceptance into their program of choice must be able to qualify. This means having high intelligence, undergraduate courses in their field, some experience, exams, and sufficient basic knowledge to qualify for the difficult road to success. With little spare time for relaxation or social activities, or even enough sleep, theirs is not a pursuit to be taken lightly. For several years, plus a published dissertation, they will literally work “their butts off” for their advanced doctoral degree!
Answering a couple of common questions! 1) Could a high velocity blue star get redshifted to appear green? No. If you take the relativistic Planck function from Lee & Cleaver 2015 (arxiv.org/abs/1507.06663) you can see this. For example, take an O3 blue dwarf of ~45,000K. To redshift enough so that it peaks in green, we need a speed of 0.97c receding. But, the resulting shifted Planck function *precisely* overlaps with the Planck function of a star at rest which peaks in green. So it looks just like a Sun-like star in color! 2) What about purple stars or other weird colors? Yes indeed a technosignature could really be any spectral function with no natural explanation. More broadly, one would look for unnatural combinations of bandpass colors (e.g. green star would appear via excess G-band magnitude). A Dyson sphere/swarm is a specific case of this, producing excess infrared flux. 3) Color perception? This video is made for humans (!), so by "green" I mean what we call "green". I can't really speculate about what an alien calls green, or really if that question makes that much sense to be honest.
Just what I was thinking
I'm not quite sure, but are there any other species even here on Earth, which perceivable EM spectrum overlaps with that of humans?
We might as well try looking for 10 nm bandwidth red star or a blue star... or in the X-ray band for that matter. The problem here is not the "absence of green stars". Nature DOES NOT KNOW of "green" in the first place.
Not to mention that for some species / AI that's actually a pretty narrow band, so they see stars in "all colors" just fine. No need to be so human-centric. So yes, "a techno signature could really be any spectral function with no natural explanation", and I believe it is VERY important to make that clear if not in the video itself, then at least in its description - not in some comment down below that nobody is going to find / read anyway.
Technically, “green” is a metaphysical perception, not a physical reality. Light exists; colors do not.
In that vein, it comes down to altering how the prefrontal cortex codes electrochemical signals coming from your photoreceptors.
@@josephcoon5809 In that vein, "light" also doesn't exist. There is no particular reason to isolate this very narrow EM band.
No. light is a physical entity; color is a symbolic language.
Light ceases to exist at the retina and becomes a cascade of electrochemical reactions until it is processed as color in the prefrontal cortex.
Sensory neurons are the demarcation between reality and virtualization.
The reason to isolate this particular range is because that’s where most of the radiance occurs.
Plants absorb two wavelengths of “blue” and two “red” for the most part to break the two bonds in CO2 and H2O. This would leave other wavelengths for visual cue usage.
Yours is one of the rare channels where I can confidently give every video a preemptive like, and your narration also has a nice asmr quality as a bonus.
The problem is in our eyes.
thanks for the fun and informative video. My only disagreement is with the claim that the physics of light says that colors are made from the primary additive colors, RGB. Visible light and RGB are determined and explained by human biology and our RGB retinal cones, not some property of pure physics like the blackbody radiation curve. I was always disappointed that science classes and physics books rarely explain this when they explain the “primary” colors.
Exactly. The universe we see is highly specific to the (typical) human visual apparatus. The universe doesn't have anything against green, per se, but simply against having too sharply defined a blackbody emission spectrum. If we happened not to have red retinal cone cells, but had ones sensitive to ultraviolet instead, then cool stars would appear "green" to us, hot stars would appear "ultraviolet" to us (barring atmospheric filtering, of couse), and blue stars would be "impossible". Or, if we happened not to have blue retinal cone cells, but had ones sensitive to infrared instead, then hot stars would appear "green" to us, cool stars would appear "infrared" and red stars would be "impossible". Of course, equipped with such alternative sets of visual apparatus, who knows what the subjective experience would be like. Who knows, in fact, whether different people with the same visual apparatus even have the same subjective experience. The point is, in order to explain objective scientific concepts in a clear and engaging way, we sometimes need to appeal to people's subjective experiences, and it isn't always explicit that this is being done.
The primary colors are red , yellow , blue.
Green comes next with orange.
@@shaquadradeloiserussell8659 wrong.
These are primary colors for pigments, which absorbs part of the wavelenghts. Used in printing and painting, they are actually cyan, magenta, yellow, black (and white for painting). Pigment colors are substractive, that's why you will never be able to get white by mixing C M and Y (you could theorically get black by mixing them, but in practice pigment absorption is imperfect so you get some kind of dark grey instead).
However concerning light itself, primary colors are red, green and blue. Light colors are additive, that's why you can get white by mixing them (that how your TV/monitor works)
@@theslay66 you cannot get black by mixing them.
"Black" as far as 'colors' go,
Has always been a very deep version of purple or red.
Wash brand new black curtains and watch the dye flood the washer.
Even when pure prismatic white light is refracted, it stil gives way initially to red , yellow , and blue.
You CAN NOT have green without blue and yellow.
@@shaquadradeloiserussell8659 Again, you can't have green without blue and yellow because of the substractive nature of pigments.
Let's take the CYAN pigment. Under a white light (so a balance of Red+Green+Blue light), the cyan pigment absorbs the Red light, diffusing only Blue+Green, which gives the cyan color.
Now let's look at the YELLOW pigment. It absorbs Blue light, and diffuses only Red+Green that we see as the yellow color.
Then let's mix CYAN+YELLOW. You get a mixture that absorbs both Red and Blue light, and only diffuses Green light. So it appears to be green.
See how it works ? The color of your pigments are an indirect result of them absorbing different wavelenghts of light.
As far as black, in case you're wondering, it's just the absence of light. A black material looks black because it absorbs all wavelenghts, whereas a white material will reemit all of them. That's why during summer you'd avoid wearing black because it's hotter.
Another great episode..
Dr. Kipping's passion for the subject matter is obvious, and he has what it takes to convey his knowledge in an effective, and interesting, way.
Thanks, Doc!
Your commentary in the cool rules and other TH-cam channels that I’ve seen you in it’s very informative scientifically accurate ingeniously thought out in the storytelling and your voice has a calming learning tone to it resonates at least here in eastern United States. I hope to continue hearing and seeing your documentaries and further videos in the up-and-coming years. Good luck with any and all future endeavors
New addict to your videos, most goes over my head, but I do learn a bit, enjoying listening to these vids while at work. Keep up the great work.
Amazing video!! I used to wonder a lot about existence of green stars in childhood. Feeling nostalgic right now 😄
It’s a beautiful question because it is indeed the sort of thing a child might wonder about the cosmos
Super amazing.
I just discovered this channel and subscribed at the speed of light. Excellently edited, written and narrated. It's awe inspiring, not sensationalist. It gives a glimpse of the immense scales, not just cheaply bombastic. Thanks for making the stars reachable to our minds eye.
Yeah I've been watching for almost 3 years. There's always an important point at the end of the videos
Thank you for another excellent video and classy responses to questioners, even to those who could be a bit less presumptuous and more polite with their questions. I made a financial contribution to Cool Worlds for good reason. Wish you continued success and always looking forward to the next video.
Great video presentation. thank you for all your hard work in preparing all the works you do.
This video is powerful.
In so many ways. I understand a lot of things that I’ve questioned previously. Thank you
Lovely video as always, thank you! As a skywatcher's side note, I would point out that anyone with a modest telescope can readily enjoy the ILLUSION of seeing a green star by looking at one of the many "color separated" binary stars such as Gamma-Delpini, Gamma-Leporis or Eta-Persei...sounds terribly obscure, but it's actually quite easy to look up and find stars these days. All three of these offer up a lovely orange vs. "green" (-ish) appearance at the piece, with only the Gamma-Del one requiring much magnification to separate visually (about 80x). They are SO pretty to observe. Clear skies! 🌠
I read sci-fi books called the Skylark series in high school written by E.E. Smith. The first was written in 1928, in it the total release of energy was accomplished by a catalyst painted on a metal and then given an electrical charge. They then used it to travel to other stars including green ones. Green because they were high in copper. Since copper burns green this made perfect sense to me then. In all the years since I hadn't thought of those books until now. Your explanation of the color of stars solidified knowledge I had but didn't put together and understood. Your channel is the kind of source that I tell my grandchildren about as an example to never stop searching for knowledge.
Really appreciate that you take the time to credit all the videos we produce at ESO.
And thank you for the great content.
Hi Luis! It’s great to see you on the channel! Let me extend a sincere thank you for the wonderful graphics you produce which we have often used! They’re beautiful and inspiring and we love sharing them.
@@CoolWorldsLab the feeling is mutual. We're happy to see the science and the videos we produce popularized by amazing channels like yours! Keep them coming!
Very well explained. A great teacher is someone that can take complex subjects and explain them in a completely understandable way. Well done!
Literally best real science channel on TH-cam. Not even close 😍
Means a lot to see comments like this 🤛
I agree ! One of the best !
Scientific or otherwise !
I agree.
This is mind blowing-- I love your videos so much. You really think outside the box man.
This is really cool! Thanks for posting all of these enlightening videos!
I entered the channel like 5 times this month to look for a new video and it just dropped - thank you, Universe 😂
Thanks Lucian! Took a few weeks off to recharge but lots of ideas to come soon
Yeah. I just looked and boom there it was. Lucky day
@@CoolWorldsLab Always worth the wait. Awesome vid! Excited for the new stuff 🔭
This is actually really inspiring. Since I started following this channel a few years ago, I've invested in a low-end telescope (still expensive) and find myself looking up into the night sky late into the night.
Big thanks to Professor Kipping and his colleagues 👏
Green wavelength is that middle child who has never gets to shine.
I’m so in love with this channel. Astronomy and philosophy combined perfectly.
Both go hand in hand.
Can’t wait to tell my son about this tomorrow! It’s gonna blow his mind!
Damn keep doing what you're doing, that's the best thing a dad can do. It's silly but I'm kind of tearing up a little
@@andrew7955 You’re absolutely right! I love learning with and through him. Long may it continue! The explanation was obviously way too advanced for him but it was fun simplifying it to a point where he could accept the statement and premise.
Show him DIRTH videos and let him decide.
Look who just made my day? The professor returns!!!
Haha happy to oblige!
I love you dude! You are my favorite channel to watch before I go to sleep, hoping my dreams have as much amazement
Idk why this channel doesnt have more subs. Super interesting topics presented masterfully.
Sir, the best thing about your videos, apart from the outstandingly researched and presented content, is the way you speak and present it in such an articulate language and exquisite vocabulary. Makes it a very present experience to listen
Agreed, and visually pleasing. 😉
I say "wow" at least once per video. Thank you!
This is the best explanation I have heard, ever!
What a marvelous explanation! Thank you.
This channel is just the chillest. I can just settle into the blankies, learn cool stuff and drift into slumber.
Awesome video...one of the most thought provoking pieces I've seen on TH-cam in a long time. It seems they wouldn't even need to wrap the star entirely...if they had a list of candidate star systems, they could float filters in the line-of-site. These filters need not cover the entire star image. Just a small patch of green on an otherwise black body radiator would be a dramatic signal!
I had already heard of this before, but not really with any kind of explanation that made it understandable why green stars aren't possible. This video was very informational.
Thank you so much for marking the sponsorship as a chapter. Im probably taking more time to write this than the amount of time I skipped, but I dont even mind. Just for that, you get a like.
I love this channel. Even after I've watched one of your videos multiple times, I will replay them for just the audio when I'm doing other things. They calm my mind. I am a Forestry professor at a university, and I think it says a lot when you can so capture the imagination and interest of someone from such a different scientific field. Keep up the amazing work.
I love this guy so much. This channel produces some of the best videos on TH-cam, no debate.
Thank you so much for your work and videos.
Sometimes I just lay down, listen to your voice without even looking at the screen, and let my imagination fly.
You have a great voice and pace, you should consider some sort of audio books!
Thank you to you and your team for all the work you do.
That was amazing! thank you for that insight. :)
Always a joy to watch, you bring a poetry to astrophysics unlike anything I've heard since Carl Sagan. Thank you.
This is one of the best astronomy channels out there, it really deserves more attention!
One thing I started thinking about when you mentioned the Green Flash effect - in our atmosphere, the Sun normally appears yellow despite being white, and I assume that's partly due to what comprises our atmosphere, and partly due to the angle of the Sun, and partly due to how thick our atmosphere is, and partly due to the light emitted by the Sun. Which is a *lot* more levers than just temperature, and it makes me wonder if you could fiddle with those combinations finely enough to make any color you wanted on a planet with an atmosphere...
It's possible I assume, with some 'green filaments' being the filter color, it might just be.
"in our atmosphere, the Sun normally appears yellow despite being white" -- I dispute that. I myself have never, ever, seen our Sun as 'yellow'.
We're taught from childhood that 'the Sun is yellow', yet I defy you to actually look at it and see it as that colour. (a) During most of the day, you'd go blind trying that; (b) the only times you can comfortably look directly at the Sun are when it's shrouded in clouds (which are themselves white coloured, because the Sun is white, not yellow) and during sunrise and sunset -- when it appears *red* .
Coupled with that is the reality that our eyes are actually incapable of seeing 'yellow' directly. I wrote a post on this not long ago: pendantry.wordpress.com/2021/06/29/is-it-actually-true-that-seeing-is-believing/
@@peNdantry I've glanced at the Sun during the day before and it's always looked yellow to me *shrug*
It's more of a morning and afternoon thing, if that's any help - at high noon it's probably about as close to white as it can get I imagine, but as it gets nearer the horizon (and further on the other side), there's a pretty substantial window of time where it transitions toward red by way of yellow. Certainly not by way of green that's for sure!
@@z-beeblebrox If you believe that you've 'seen' a yellow Sun in the sky, you need to look again; I believe that you are mistaken. I've just been outside, and have seen the full moon. It is clearly white, without even a hint of yellow. Its light is reflected sunlight from the Sun. If the Sun were yellow, the moon would also be yellow... no?
@@peNdantry No, because the sun is yellow due to Rayleigh scattering inside the earth's atmosphere, and the moon is in space, AWAY from the Earth's atmosphere. The only time the earth's atmosphere affects the moon is during a harvest moon, when the light from a sunset passes just by the edge of the earth and directly hits the moon, acting like a gel filter. Since light from the afternoon sun can't hit the moon without impossible angles, that's the only coloration the moon can receive, since in the vacuum of space the sun is white.
Thanks for this wonderful video, very informative as always on this channel. A small remark though: alien natural vision (if they have any) is probably not sensitive to the same spectrum of electromagnetic radiation frequencies as humans are, and if they are, they probably don't see colours in the same way that we do. “Green” is a purely human perception of a phenomenon whereby a light source (or lit surface) emits more electromagnetic radiation of ~550 nm (‘green’) wavelength that at 650 nm (‘blue’) or 450 nm (‘red) - irrespective of the amount of radiation emitted outside our visible spectrum (400-700nm). So, I doubt that alien would create a beacon by artificially filtering out 400~500nm and 600~700 nm radiation simply to make the 500~600 nm range relatively prominent. While they could indeed filter out some frequency range to make the start look unnatural, they could filter out any range, including outside our visible spectrum. So overall, the probability that (1) there are adanced aliens civilization in compatible space-time locations, (2) they want to make a beacon out a star and (3) they choose to do this by filtering out red & blue light, is in mho quite low... So, I won’t be expecting green stars anytime soon - unless it's humans from the future who used time travel to tinker with a star in our past.
I’ve always been interested in astronomy. One of my favorite classes in college was a stellar evolution class. And it has literally never crossed my mind that we don’t have green stars…cool video!
Fascinating stuff, thanks David. I’ve been trying to film a green flash for a few years whenever the opportunity pops up (not often enough when I’m home in England ;)
That was a particularly lucid presentation and I learned a lot from it. Perhaps creating a Green Beacon from the Sun doesn't require wrapping the entire sun. Just making a big enough device/filter/lens close enough to a Sun to transmit/produce a strong enough green light signal would be enough for an advanced civilization to detect it.
I really enjoy this type of video - Learn some cool science, and conjecture about how what is known can be used. I hope you'll continue to make more videos like this. Thanks 😎
11:30 ahaha that meme of the brazilian actress never gets old XD I bet its the reflect of many of us when watching all those formulas. Love the content, just subscribed.
I've been intrigued by the quality of research that goes into each video. Keep it up!
Now, any chance you cool guys and gals at Cool Worlds Lab are investigating the Grand Solar Minimum that we are just now entering for the next 30+ years (2020 to 2053)?
I LOVE this channel so much! I can’t help but feel a similar sense of familiarity to listening to/watching Carl Sagan. You can’t help but be mesmerized. You are both incredible educators, reaching lifetimes of individuals, spanning across our world & maybe, one day, the universe & beyond. 🌏🌎🌍
Life was so boring before this video. Thank you, this made my day. 🧡
Life’s more fun when you think about the universe sometimes…
Surely you have no life
@@CoolWorldsLab YES, Ofcourse it is..!!
@@CoolWorldsLab will there be purple stars?
This video made me click subscribe button before i reached half of it. Its so well made. I am looking for more!
Don't stop this format!
I work with a lot of people. Rarely do I come across a coworker that shares the same passion for the cosmos as I do. My love for astronomy started when I was a child. I loved NASA, our Solar System & using my imagination. Today I got to discuss the upcoming James Webb telescope with a coworker. I love talking about space as it really is the final frontier!
🔭🪐☄️🛰🌎🌒☀️🪐🌌
Beautiful narration, beautiful voice and amazing video!
17:18 I expected this video to be bad honestly, but I quite enjoyed it. Thanks for making it :)
Your voice and accent are very calming and relaxing 😎
Could humans have developed vision in the "visible spectrum" precisely because our sun's emissions are relatively flat (and peak) in that area?
And relatedly, the green technosignature is only obvious and simple to us humans only because it's in the middle of our visible spectrum. For an alien civilization with a different star and vision system, they might focus on another part of the spectrum instead.
Yes. That’s also why chlorophyll is green, because it’s the peak of our star’s emissions.
An alien whose visual band began or ended at green would see many green stars, just as we see blue and red ones because they are the ends of ours.
@@piedpiper1172 No, I think you are misunerstanding the actual physics at play here.
@@shrimpflea Some Stars peak emissions are outside of our visual range. Either below (red stars) or above (blue stars).
If you imagine a creature whose visual band ends at the wavelength we call green, rather than having it basically in the middle of their visual range, that is the wavelength they would see for a star at that end of their vision.
For example, imagine their visual range began lower in red than ours does, but ended at its highest in green. So they seem from infrared to green. A star that is blue to us would be producing light mostly in their “ultra green” (beyond green) band.
This is without a doubt the best explanation of this that I've seen. That said...
Could you have a star surrounded by a gas that absorbed most light except for green? maybe that gas formed from an unusual elemental makeup of the star or material in the surrounding nebula? Could something like that last a significant amount of time compared to the star itself?
Edit: you covered this too, it would be very unlikely to be natural. Neat!
@Peter from NZ interesting thought, but I’d guess that water is too heavy to support a planet large enough to make a vapor cloud that can blot out a star - the planet would probably just attract a big gas shroud of its own and end up as a gas giant. Generally speaking, this would be hydrogen, not oxygen.
What makes Dr. Kipping’s videos so effective isn’t so much that it’s presented in an understandable way. Lots of science communicators can do that. The real key is that even though in videos like this he’s demonstrating the impossibility of something we’d all like to experience, he knows how to take care of our emotional intuitions well enough that we no longer feel as much intrinsic desire to subconsciously reject what he’s saying. Most people explaining why you can’t travel FTL sound like a parent explaining to a child that humans can’t fly. It’s intrinsically negative, and in that example ignores the emotional desire to fly anyway. Dr. Kipping subconsciously makes us open to understanding his concepts by stroking the desires they put out of reach. The other key is that he does a really good job of incrementally addressing all of our mental attempts to find workarounds.
Are our dreams of green stars other universes?
I've been watching your incredible videos for some time now and keep revisiting this one. In my opinion, this video may be one of the most important ones you've done to date.
Thank you for these videos. They're very important to me and I'm sure many others. A beautiful escape from a stressful life. Peace.
I like the idea about making and looking for techosignatures, and artificially learning how to make a green star would be awesome, but it's simplistic to assume that an alien would make a green star for us to find. Their visible band of light may be different from ours. The laws of physics are the same anywhere in the universe, so it is plausible that a totally separate life form could evolve similar mechanisms to sense its environment, but even IF a powerful technological spacefaring species saw this phenomenon with starlight, they would then make a "green" star based on what THEY see, and so, we should just look for a star whose light signature is compressed towards a particular wavelength.
"The laws of physics are the same anywhere in the universe" this is a statement that cannot be made. we have no experience outside of our own solar system, and virtually none outside of our own planet. without any way to actually test the "laws" of physics around even our own galaxy, much less between galaxies or in other galaxies, we have absolutely no idea if these are actually universal laws.
@@FingerinUrDaughter The video covers this starting at about 10:45. You could pick different values for the Planck and Boltzmann constants or speed of light and the shape of the BB emission spectrum stays the same.
It’s unfair to say we don’t know what’s going on in the rest of the universe. One of the earliest confirmations of relativity came from the sun bending light from distant stars. We can detect all manner of weird objects/events from black holes and pulsars to gravitational waves precisely because we can apply universal laws and extrapolate what happened at mind boggling scales of mass, velocity, pressure, distance and time. There are limits (Dark energy? Dark matter?) but we’re not ignorant.
Great! I watched the video last night (Germany) an I had a really close look to the sunset a few hours ago: I really could see the green flash without any optics - with just my eyes! Just 2 seconds. First time in my life! Never thought about it. Never realized before. From now on I will always try to see the green flash. Thanks for this video!
Lucky!
This video literally blew my mind for some reason.
great explenation! Thank you
This is amazing. I'd never read a good explanation why the sunset doesn't go through a phase of green before
Thank you for another video
👍
I just have to say I love the idea of a beacon of sentience.
Great video.
Incredible as per usual!
Thank you so much for this informative video and all the others on your channel. Maybe i don't understand something correctly but i gotta ask one short question: why aren't we seeing green stars due to redshifting? Why isn't it possible for stars that emit blue light to appear green to the eye because of the doppler-effect? I am happy for an answer! Bye!
Exactly what I was thinking :))
Would be cool to make a fake star that emits green light
Where’s the star?
The star is real, the color isn't.
I don't know if you notices changes in the sky,moon, day, and night.. I think it happended a few days again. it is a bit odd a bit odd indeed.
As long as it doesn't involve Necrons.
Aliens: We do a little trolling
I never thought of blue stars, but it makes sense. There are blue flames, like from a gas furnace.
Great video as usual.
Thanks David
Well yea at the start I thought it was just a curiosity you know why no green stars but the further in the video the more it dawned on me that it could be used a as sign of something like a techno signature.
after explaining that 900nm < 10nm it clicked and I knew for sure you were going to mention it :D
Really loved this video
Dear cool worlds labs, I am extremely curious on your opinion and theories on the green pea galaxies. Though some of them might be very vibrant blue star galaxies there are some that are undeniably green. Love you guys and the channel, keep up the good work and would love to hear back from you.
Thanks, great information !