Light: Crash Course Astronomy #24
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- Опубликовано: 31 май 2024
- In order to understand how we study the universe, we need to talk a little bit about light. Light is a form of energy. Its wavelength tells us its energy and color. Spectroscopy allows us to analyze those colors and determine an object’s temperature, density, spin, motion, and chemical composition.
Check out the Crash Course Astronomy solar system poster here: store.dftba.com/products/crash...
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Chapters:
Introduction 00:00
Light is a Wave 0:31
Electromagnetic Spectrum 1:32
How is Light Made? 3:19
Atomic Structure 4:47
Spectroscopy 7:14
Redshift vs Blueshift 8:26
Review 9:50
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PHOTOS/VIDEOS
Wavelengths imagine.gsfc.nasa.gov/educator... [credit: Imagine the Universe! / NASA]
Observatories across spectrum imagine.gsfc.nasa.gov/Images/s... [credit: Imagine the Universe! / NASA]
Red hot spiral hotplate freefoodphotos.com/imagelibrar... [credit: freefoodphotos.com]
The Crab Nebula en.wikipedia.org/wiki/Nebula#/... [credit: NASA, ESA, J. Hester and A. Loll (Arizona State University)]
Building the Space Telescope Imaging Spectograph imgsrc.hubblesite.org/hu/galle... [credit: NASA]
VST images the Lagoon Nebula en.wikipedia.org/wiki/Lagoon_N... [credit: ESO/VPHAS+ team]
Jupiter www.nasa.gov/images/content/41... [credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute]
Venus en.wikipedia.org/wiki/Atmosphe... [credit: NASA - NSSDC Photo Gallery Venus]
Ring Around SN 1987a, image 1 www.spacetelescope.org/images/... [credit: Jason Pun (NOAO) and SINS Collaboration]
Ring Around SN 1987a, image 2 www.spacetelescope.org/images/... [credit: George Sonneborn (GSFC) and NASA/ESA]
I feel more enlightened after watching this. It really shed some light on this topic. Perhaps I am slightly brighter today than I was yesterday. It kinda turns me on
This dude knows whats up
I'm blinded by your comment
🌟
hm so you can shag to that
Hans Martin Vatnan
Keep the puns light, buddy. You don't wanna overexpose yourself.
That must have been the best explanation of electron shells I heard so far.
I love this show. Thanks to everyone who keep this going.
InfraRaven Thank YOU for watching :D
-Nicole
What about the photoelectric effect that proves light is a particle. Please do a video on that. Love the content btw.
i thought light was a duality and not a wave. it exists as both a particle and a wave
it does. here is a picture: www.nature.com/articles/ncomms7407
harly haze yes it is both a particle & a wave...
This just became my most favorite episode of all crash course series. Analogies are perfect. So simple to understand.
You just did an entire video on light without mentioning photons. I'm impressed.
Been watching CrashCourse since highschool and now that I'm a teacher, I still love coming back to these videos :)
This ten-minute video made me understand atomic structure where two semesters of chemistry failed. Thank you, Crash Course! Love what you do!
Omg I want that periodic table at 5:22 as a poster on my wall... Make it happen plesh!!!!
P.S: You explain how light is emitted faster than my physics teacher did... OVER ONE YEAR .__.
Jordan O'C Apparently you can make it happen yourself: store.dftba.com/products/crashcourse-chemistry-periodic-table-of-the-elements
Penny Lane Awesome! Thank you for the link :)
@@unvergebeneid thanks penny lane.
@@kitty.miracle It's a poster. A physical thing. Of course it isn't free.
You just said everything I was thought in a month
Taught*
Seems I wasn't taught enough English
Amar Duratovic CONFIRME...no wait...sorry.
You have just disproved it
Amar Duratovic 6 comments! Double Illuminati CONFIR, DAMMIT! Sorry, again.
MOAR.
Just binge watched all episodes(up till light, which is the last episode as of now), took notes, googled stuff I didn't understand, fast forwarded stuff which I knew well and re-played stuff that was awesome.
WANT MOAR!
Awesome job :D
This episode was so awesome.
Well.... They're all awesome...
But this episode was awesome
I also thought the one on the left was darker
This was the hardest to grasp episode yet, but a fantastic and critical one. Also the Green brothers on the moped was awesome.
I have been using Crash Course videos in my daughter's history, science and A&P classes for the last two years. This teacher is the best. He explains the information about light with just the right balance of energy and calm (he is very easy to follow, others tend to go too fast for even me to understand 🤯). Well done.
What is (visible) light? It is a wave, period. At last, somebody who can explain this clearly. Inspired by the video from Phil Plait, I would highlight the following:
Photon:
Each photon is an oscillating wave which push and pull the electric field as it propagate in free space - creating local increase and decrease of electric field pressure - the same way as sound wave propagating by pushing and pulling on air molecules.
Fourrier Series for light
Our eye perceive exactly one octave, the red being equivalent to bass and blue equivalent to higher pitch instrument. According to Fourrier series, any wave that is not sinusoidal (produced by an object circulating around a sphere) can be simulated by adding a few sinusoidal wave which have integer multiple of the fundamental. For example, a square wave at 60 Hz can be simulated as follow:
a*60 Hz + b*180 Hz + c*180 Hz
where a, b and c is the intensity (how loud the volume is set) for each of these frequency. Changing these coefficients (and adding also the even numbered) would produce saw tooth or any other waveform. Brief, when a wave is not a pure sinusoidal shape, then it contains harmonics, which is small amount of wave with frequency exactly double, triple, etc.
The color detectors in our eye may react when a wave of exactly double or half the frequency hit them. That may explain why light going up after blue appear as purple ; the red detector become activated.
What are electrons
Atoms are not like as small solar system with proton/neutron in the center and electron rotating around like the planets around the sun. The electrons are "something" which wiggle randomly "around" very fast, like a bouncing rubber ball inside a metal or glass sphere .
Humming bird vision
The uncertainty principle is related to our incapacity to figure out how much faster this "thing" called electron oscillate compared to our measurement devices. Predicting where is an electron with the present technology is like asking to a human to predict the location of the wing of a hummingbird. We just see a blurry cloud. But a hummingbird eye and brain is about 10 time faster than our visual system, so they see the beating of their wing when looking at them self in a mirror.
Dangerous cliff
Our distant ancestors, the Jellyfish, wisely selected the visible light to get the 4K clear vision that we enjoy today. Like all engineering decision, this choice represent a compromise between conflicting factors. Using a lower frequency, like the infrared, give more blurry picture, as any desert snake can tell you. Using higher frequency gives more clear picture, but can be used only on clear day time. Furthermore, the ultraviolet light (and X ray and gamma ray) is ionizing. It's energy is so high that electrons are kicked off atom and long molecules chain break apart. With UV light, the DNA data bank receive kicks in the teeth and cells forget how to behave politely in pluri-cellular society, which is perceived on the macroscopic scale as cancer.
This is one of the most informative and accurate videos on the physics of light that I have seen, and I've seen quite a few from private youtubers and universities. I'm happy that he did NOT mention photons, or particle properties of light, but just the wave properties, he is more correct then other people. That being said the video is not 100% accurate
One of the best educational videos I've ever seen. Love you, CrashCourse team!
Was the left one slightly darker?
FunkyHonkyCDXX nope exact same ... after the compression of youtube..
FunkyHonkyCDXX That is what I perceived also, but ***** is most likely correct.
boomstick900 i thought the one on the left was slightly darker too but then i checked and they were the same
FunkyHonkyCDXX Any perceived difference is likely a mix of the background around them being slightly different and us looking /really hard/ for a difference and fooling ourselves.
Ath Athanasius I had a feeling it was the background causing an illusion. Thanks!
I'm excited about the next episode! Distance throughout the universe has always fascinated me. Thats for your expertise, Phil!
This was very enlightening.
+Endrank luvs da 4 loco How nice of you :)
flash of briliance
how puny
This is great for homeschool. Cool demonstration with the electric stove
8:36 was a beautiful performance.
That was very well explained, I am learning about spectroscopy, and this video helps me to understand the concept better. Thank you
Thanks Crash Course! My middle school child has learned so much from this. Without this she wouldn’t have been able to learn as fast as she did!
Finally, glad that I have a clue now on how does scientists find what's in an object billions of miles away! Thanks a ton for making it so easy to understand.
Everything mentioned I already knew, but it was illustrated in way that made me appreciate the science so much more. Love the staircase analogy!
Just a small correction: we didnt evolve to see the light which the sun emits most strongly (it emits electro magnetic waves outside our visible spectrum too, and granted it is not as strongly, it probably would be useful to see and differentiate the wide band of IR that the sun emits, which is much wider than our visible spectrum); we evolved to see the light frequencies that water lets through instead of absorbing. Considering where we come from, there wouldnt be much point, evolutionary speaking, to waste energy on being able to detect light waves that wouldnt penetrate water anyway. So water is very much the key in the evolutionary "decision" for what light we can see, and not what light is "emitted the strongest by the sun". If we had evolved on land instead of water, then no doubt our visible spectrum would look different and be expanded a fair bit into the IR section.
that all makes sense but it cannot be the reason we as humans don't possess the ability to see outside the visual spectrum because mantis shrimp have 16 different types of photo-receptors and they evolved underwater so that isn't the reason we as humans don't have the same ability.
How do you explain the Mantis shrimp? Or bugs? Also there's no definitive reasoning that can be proven by experiment, so unless something is an important distinction in the subject at hand... astronomy.
@@madLphnt I understand your point, but why don't MOST animals have 12-16 color receptors and eyes that can individually perceive depth? We all started underwater, yet the mantis shrimp seems to be the only animal to have evolved this incredible ocular trait.
I suspect the answer lies in evolutionary pressure. We didn't evolve more complex sight, because it was good enough just seeing the spectrum it did. In fact, many animals beyond old common ancestors may have gained or lost photoreceptors. We've gone this long without seeing the near-infrared spectrum, what advantage would it really have for us now?
The mantis shrimp lives in shallow tropical and subtropical waters, meaning they ARE exposed to UV, and likely some near-IR as well. Although far-IR hardly penetrates water at all.
They also see polarized and circularly polarized light, of which the latter is almost unheard of. Clearly, judging by the the other animals in the same environment, it's not a requirement of catching prey. So it's likely a sexually advantageous mutation (like blue eyes, not actually advantageous, but attractive), which became used in communication, and later helped sexual selection.
The fact we're discussing this at all is proof that genetic mutation can offshoot real freaking hard in one direction. Many other animals can see, but the mantis shrimp just sees better than the rest. Likewise, a large number of animals can think, and even communicate concepts to their kin (like corvids), yet we seem to be the only animals capable of communicating incredibly complex ideas.
I'm fairly confident that even if you could communicate in the language of corvids, you could not explain trigonometry to them.
shut up
GroovingPict not reallu
This dude is such a great communicator.
my mind is always blown when I learn how it is we know things about our universe. Science is awesome
I wish this guy was my teacher at college...
I love how Phil injects his love for this stuff into every word he says.
Also, Crash Course just taught everyone a month's worth of college Gen Chem in ten minutes, and it actually made sense. I love you guys!
Phil really knows how to cast light on issues. He is very enlightened in the field of astronomy. He also makes it fun to learn about astronomy, with his lighthearted jokes. Thank you for helping lighten the burden of everyday life with your entertainment. Boom.
Best lectures in this channel comes from this guy
Easy simple and can draw some light on complex subjects without letting much-needed information slip
This episode was very illuminating.
Hahahaha ha ha...
Phenomenal content. I am in awe by the quality of how well this is written, animated, narrated and directed. I will be showing this to my students.
Now I finally get how astronomers can tell if some nebula has this certain element when you can't touch it. At first I was very speculative and kinda think "They can't be right, they're just assuming." Well THIS clarified TONS of stuff for me.
I swear to god this series is the best thing ever.
I don't know if you are going to read this Phil, but anyways I would like to thank you very much for this series. You managed to make astronomy more interesting to the masses, and you did it by not making it too hard to understand. I am a civil engineer and I love astronomy,physics and math. So I felt very happy to see this, and I hope we have more episodes of Crash Course Astronomy. (also recomended to some friends interested in astronomy to watch this ASAP!)
A big fan of yours,
André Gomes
0:19 The first thing I thought of for that hint: He's obviously waving and waving is a form of greeting someone, saying hi is also a form of greeting someone, and if we look up high, we see the sun, and the sun produces light?
I don't think you're right. Light is a wave, so he 'waved' his hand, get it? c:
Adrian Ulloa I think he was trying to convey a joke.
Kevin Blake I couldn't even think about the meaning of that hand waving because after "how does light get made" I was still trying to picture a couple of photons awkwardly having The Talk way too late with their kid after like 5×10^16 m: "If a wave and a particle love each other very much ..." "God, mom! I've _seen_ electrons transition to lower energy states before, you know."
Kevin Blake Half life 3 confirmed.
@ 7:32 photoshop tells me that those are the exact same colour youtube processing does this sort of stuff to preserve bandwidth
I could see the difference in the red squares. The square on the right of the screen is about 1 shade lighter. Maybe 2.
ha I though I was alone
I could too, time for feeling special
I couldn't...
lol
My computer says both are RGB 229,0,3
12 years of public education in the sciences... and only today do i finally make the connection that the entire EM spectrum is essentially ALL light... thanks phil!
godddddd...jesus.........i'm living for these 3 channels...1..crashcourse....2....it's okay to be smart....and 3...kurzgesagt in a nutshel.......................love these 3 channels............guys keep making more stuff like this ,,,i feel so powerful and enlightened when i watch these kind of videos.............much appreciation,,love and respect from india,,,
At the quantum level though, light is actually a particle... and a wave.
I didn't know the cat was dead ubtill we got to the vet's...
***** an electron you mean not light
Thats probably being saved for Crash Course Physics
Dany J. No he means Light, Photons behave like particles with wave properties, or more like a wave with particle properties. really cool when you get in to it, and it was the only thing i was bumbed was missing from the video, but for astronomy the particle properties of light are no where near as important as the wave properties.
Gabriel Soos in case of light i wouldn't consider it cool, it's just that something is missing in the whole process and we'll understand it one day whatever other physicists say without physical evidence in my book light should always act as a wave. in case of an electron it has mass so its wave like behavior is actually much more interesting to get into
I've never seen a video that explains this more beautifully. I just wish he had went more in depth on photons.
CrashCourse This is one of the most concise, thorough explanations of the wave nature of light I've ever seen, with just enough mention of the actual structure of atoms to highlight how integral spectroscopy is to understanding the universe.
Outstanding work, Phil and all the CC team!
It's insane thinking about how we are just extreme luck and that if a certain chemicals never existed we may never of existed. Keep up the good work Crash Course :3
phil you are an absolute legend ! your passion & enthusiasm is INCREDIBLY infectious !
I'm french, and I understand better the crashcourse's videos that my lessons in french at high school. Thank you! :)
I love Crash Course Astronomy. It reminds me of things that I've learned but forgot and teaches me new things that are awesome.
Episodes like this are the reason I love CC Astronomy.
Phil, keep up the excellent work. You are awesome.
Its really amazing . This lecture has proved very useful in clearing my concepts and many doubts as well. I really felt educated on the subject. Thanks a lot and stay blessed.
There is so much information jam packed in this episode. I will have to watch it again.
Most informative ten minutes of my life.
This is the best video on RUclips for this subject, and I've watched many. Thanks!!
This has been my favourite crash course yet! It has just been so immersive and entertaining.
The best explanation of light I have ever seen. Thanks Professor Plait.
I already know a lot of this stuff, but this series is so well made, I can't help myself but watch it. Phill is so charismatic, you can't not love him. Wish bloke like him taught in my class, I can guarantee a lot more of my former class mates would have been into science.
this guy is amazing. i should start crashcourse astronomy even though im not studying anything envolves with astronomy.
his just brilliant.
7:13
Soooooooo many puzzle pieces just fell into place.
I'm rewatching these series. And I just remembered how eye opening about science this particular episode is. Very, very great one. So much so, I've spent my last 2 hours, maticilously translating it to a very good Turkish. People should watch this in every possible language.
I just rewatched this. Being in physics now, learning about electricity and magnetism, really opens my eyes to this video. Awesome!
Wow, just wow!
This is getting better and better.
Thank you Phil and the whole CrashCourse team for all the videos.
This video is enLIGHTening. Heheh.. Sorry everyone..
Casey Edwards pun racoon is proud
Cmon man lighten up why you gotta be so dark...sorry couldn't resist
Casey Edwards that pun was great soon it will be universal(was that even a pun....sorry)
Casey Edwards No forgiveness...
Now that's what I call a.... Shitty joke! (sorry)
Thank you very much, Phil Plait and the others at _CrashCourse_ Astronomy, for making this video! Honestly, I knew most of the physics of light and the Doppler effect from elementary school but I did not realise the importance of light in astronomy. Literally everything we do in astronomy and everything we know about the Universe depends on light/radiation in one way or the other.
I do have a question after watching this video. You said that an atoms of an object emit different wave lengths of light, containing different levels of energy, depending on how hot the object. How can we differentiate between a cooler object which emits a shorter wave length than a hotter object of another element? What happens when wave length and the element compensate for each other? How can we tell the difference between a hotter object that of element A from a cooler object of element B if they emit the same wave length of light?
sir today i have learned a lot from you. Thanks a lot. look forward to learn more.
Loved this episode!! One of my favs.
A lot of stuff that I didn't know.
Thanks for this amazing channel.
the crash course astronomy intro is my favorite. Thoughtbubble Phil just looks so dang happy and cute!
funnily enough, Phil looks a lot like my favorite uncle, who speaks with a south african/british accent, and taught me lots of what I know about astronomy and even gave me his old telescope :D
This was more helpful than going to lecture for a month, thank you so much
This was a brilliant episode. Very well written. Thanks for making it!
This series is AWESOME!!! I never knew how interested I was in astronomy until discovering this series. I’m totally blown away by all the great info in this course! Really wish they would’ve taught this interesting stuff in high school. 👍
wow, this episode just blows my mind. To think we can actually understand the universe because of a simple quirk of nature about how electrons work.
So clear and succinct! I love the host! Slow, clear and engaging!!
His approach and his scripts are awesome. Really knows what are the keypoints and how to present them.
The guy on the motorcycle looked like hank green
it is John and Hank Greene
It’s from the movie dumb and dumber
This blew my mind... wow
+Nao R :D
I have watched almost every video of every series of C.C. and the Astronomy series is by far my favorite.
This episode was especially awesome because it helped me appreciate how astronomers gain knowledge of the universe. The visuals and explanation of light, atoms and their correlation were the best I've seen.
This is amazing. By figuring out the mechanics of light, humans unlocked the mysteries of the universe. Also, the way light takes time to move, it can show us the past. Once the James Webb Telescope is launched into space by NASA, it will allow us to look back at event in our universe which happened over 13 billion years ago, to the very origins of creation. It truly boggles the mind
Its a course in astronomy. I just came here 24 videos ago to learn about right ascention and declination.
I love crash course!!! They make everything so much easier and interesting!
I love this Crash Course so much! Astronomy, guys. It's the best.
This was perhaps the best video of this series. Using light to reveal the secrets of the universe is probably the biggest wow factor for me on the subject, and this video was done well.
"Can you tell the difference between these two squares?"
Me: yeah
"Your eyes probably can't see a difference..."
Me:🤔
Lizzy Burt I saw the difference as well lol
Yes, the left one was brighter red.
7:35
Is it weird that I can somehow tell that the box on the left is a darker shade than the box on the right
opposite
AJ Nur it’s actually the opposite yeah. At first glance the right one looked (very)slightly darker
Just wanted to thank you for this video which has clarified a lot of information that I sort of knew and understood but then structured it into a coherent logical sequence. Crash Course is phenomenal for those that wish to learn more about...anything really. Merci beaucoup !
This show is the best. Thank you all who were involved in it. This is why the internet is so cool. I would have never learned so much about space in such a fun way.
How can light be real if our eyes arent real?
- Jaden The Philosopher
Husein Ali Your forgot to use more capital letters!
HRCFre4k Worse, he forgot an apostrophe. Even worse, an extra "r" has crept into your sentence.
Husein Ali Jesus Christ he makes real philosophers look bad.
What Is The Second Word Of life As Life Sees Itself?
-Jaden Smith
Husein Ali A lightswitch
***** bad day?
How does the electron decide whether to stay on their step or go down and emit energy?
Meditation
Simply one of the best channels on RUclips, period.
dude,you taught this concept in such an awesome way.it took my teacher a month to finish this,you taught this only in a matter of minutes
I learned a lot from this video
I want that periodic table, where can I download it?
Daniel Nuske No download link, but a poster is available at www.dftba.com/crashcourse
CrashCourse Hello
because of my internet speed i want to download your videos only for my self and watch it over & over. can i?
(I have a software for downloading videos)
+CrashCourse
Is the electron concept on the stairs how plant grow? Because you said they need light and energy to jump up the stairs
+CrashCourse Omg No way! I want one! I hope it has oxidation states too... That would be helpful.
+Melissalynne7 Snipping tool is better imo, although I suppose you can take a screenshot first and then use it on the screenshot.
Man science is so much more fun when you aren't forced to do it for school.
Was not prepared for the cuteness of the periodic table. Elatedly surprised!
"here"s a hint" then proceed to wave. fucking brilliant, i laughed more than i should have ^^
The square on the left was a bit darker of a shade, or at least that's how it looks to me without looking at rgb values.
Ben Toth opposite
I agree i took many science classes in college including physical chemistry, chemistry, physics. That was by far the best explanation i have ever heard.
One of the best explanation I've heard so far, thanks!
Dammnn!!
Watched this at 2am here, who knew science could be this interesting 😂
Thanks to Phil! And cc.
So.. u could technicly find out
length, distans, mass, health, etc
About any person only by capturing, analysing and seeing their electro magnetic lights?
Not really health.
I don't think you can find out the mass either.
Broken soffa How about by seeing how it distorts light patterns ?
MrATN800 That would require a VERY VERY specially designed experiment, but yes technically you could determine a persons mass if you knew the vector of a light source and could measure the incredibly small amount of deflection a human sized mass would bend it.
just wanted to be in this thread until someone could answer or explain your question
Because of certain circumstances, I had to join my current courses two weeks late. I spoke to my astronomy professor about how I was worried I would fall behind, and told him I watched these videos, and he spoke very highly of Crash Course. I missed an A on our first exam by 2/96 points
Awesome explanation of light - particularly admired the graphic, explanation of the role of the electron and, as always, Dr Plait's enthusiasm and captivating delivery.