Why Do Spinning Liquids Make Great Telescopes?
HTML-код
- Опубликовано: 3 дек 2022
- Why Liquid Mirrors Make Great Telescopes
Shop the Action Lab Science Gear here: theactionlab.com/
Checkout my experiment book: amzn.to/2Wf07x1
Twitter: / theactionlabman
Facebook: / theactionlabofficial
Instagram: / therealactionlab
Snap: / 426771378288640
Tik Tok: / theactionlabshorts 
Наука
At 2:17 and 2:23 I accidentally say it backwards. I should have said the faster I spin it *the shorter* the focal length not longer. Shorter focal lengths give the wide angle view.
Why are telescope mirror & mirror blank so expensive ?👍
Glass: "Am liquid"
Gallium: "Yeah, but yur too thicc"
Glass: **sigh** "I feel invisible sometimes"
Gallium: "Need a hug?"
Mercury: "Ew. Get a room."
And that, children, is why gallium coats glass and mercury is toxic.
Also, formula on 3:28 is wrong!!! Always, check your intuition. I know, you just c/p from wikipedia, but it is also wrong there. Much more intuitive is this: *Correspondingly, the dimensions of a symmetrical paraboloidal dish are related by the equation: 4FD=R^2 (therefore F=R^2/(4D)), where F is the focal length, D is the depth of the dish (measured along the axis of symmetry from the vertex to the plane of the rim), and R is the radius of the dish from the center.*
BTW, I really like your channel!!!
Can you freeze the Galium while spinning for a fixed mirror in frozen state ?
This is how the 'star wars' satellite mirrors worked.
I visited the mirror making lab at the University of Arizona and they actually use this exact technique to speed up the manufacturing process. They pour liquid glass into a rotating mold, and as the glass cools it forms a more or less perfect parabola. They then use traditional sanding techniques to grind out any imperfections until the mirror is basically perfect
Yeah, I wish I could have been there when they made the GMT mirrors.... When I was i Tucson in 1999, I missed out on the Magellan II mirror....
I was about to ask why they don't just rotate a hot liquid metal/glass until it cools and hardens to make large mirrors, but I guess they actually do, cool!
Genius idea. Though that makes me wonder, they probably need the glass to be uniform thickness, so while they're spinning the thing to shape it, they need a mould under it which is equally perfect... How do they make that? Same process but with a different material?
Cool
@@redryder3721 Nah, they just need it to be close enough because they compensate for thermal expansion by making it a little bit thicker that way they won't have to make a perfect parabolic mold.
That demonstration with the blue water in a parabola was really cool
.
.
.
.
.
This principle has revolutionized the production of very large telescope mirrors. Most 8-meter mirrors (that's huge professional-size) are made by rotating the furnace with the molten glass and slowly cooling it down. The mirror blank then solidifies into a paraboloid. It still needs some grinding, but the process is many times cheaper than traditional methods.
One quibble: faster rotation results in a shorter focal length, not a longer one.
Never seen a scientist with man ban, what the hell? Am I still alive?
The amount of knowledge humanity already possesses about the cosmos is both humbling and awe inspiring
There is a similar technology called liquid lenses. There you have two transparent oils with different refractive index in an electric field, and based on the voltage the interface between the two oils bends differently and acts like a lens. This was used in some early autofocus webcams back in the day.
Cooll that you remember that. I also read about them many years back. I was always wondering if they where ever used.
If only we could use that technology in glasses...
What happens if the spinning is done in free fall? There is no force of gravity in free fall.
With sun light you can start a fire
@@davidmudry5622 then there is no parabola, and after a long time eventually surface tension dominantes, forming a somewhat round blob.
Sooo jealous of the fact kids of today get to have this guy be a thing! The content he covers, as well as the simplistic yet somehow still extremely informative without being dumbed-down method in which he presents it, is all very captivating and attention-grabbing. Give this guy a catchy stage name and a show on PBS, he could easily be this generation's Bill Nye-Already is, if you ask me.
Not that he could ever replace Mr. Nye, but it would've been killer to see these things when I was a kid.
*Bursts into room* "MOM, WE NEED SOME GALLIUM!"
My fingers are crossed that I can get my son or daughter into this channel.
It’s a great channel that’s for sure
I think he can be pretty complicated, but I’m in yr 9. Despite this, I do agree that his content is interesting and informative
When I was in grade 6, I spent my whole day as a kid watching these kinds of videos but I haven't watched content creators like him, backyardscientist, etc.
Well they have to be interested in science first. I mean who doesn't like science? Star Trek is the best.
"Bill, Bill... " Always knew I would be educated while the teacher had the moment off. Definitely suggest ActionLab to my sister for educational purposes for her children.
After reading about liquid metal telescopes in a science magazine about 40 yrs ago, I obtained and kept a 10 lb bottle of mercury around hoping to one day build one. As I got older, my sense of responsibility outpaced my scientific ambitions and I took it to a mercury recycling center.
still do it ......with gallium.
This comment had no business making me as sad as it did.
Feel the irony. They'll sell it, make products, CFL bulbs and stuff ending in waste. It was probably safer with you.
Quitter! ;-)
Another advantage is that any dust would go to the edge of the spinning mirror due to the radial force :)
Here is something useful and important to know 👉 The Connections (2021) [short documentary] 🔥
oh thats nice , din think bout that
Will it though? Other matter is competing to get to the edge.
@@JasonMitchellofcompsci I don't know for sure, but since there is no flow going on, just stationary liquid, the force alone would *probably* make any dust that's floating on the surface to slowly float away to the edge.
At least that's my hypothesis :)
Dust being lighter than liquid metal would tend to collect in the center and not the edge. Oxides would move outward if they are denser than the base metal.
The simplicity of explaining the complexity of scientific theories is what drives me towards this channel. Keeps the science kid in us alive even at my age. Thanks to the team at Action Lab.
Great video! Actually I knew about the parabolic shape of spinning fluids from my old text book in fluid dynamics, but that they in fact used this phenomenon in telescopes was amazing! Thanks for great video and explanation, keep up the good work! 🤓
I've never thought about the difference between lenses and mirrors before, but you're right. Light should reflect the same regardless of the wavelength, while different wavelengths refract differently.
This is super cool! I understand how it is simpler for this to be pointed straight up, but it would be really cool to see how it would look if you were able to put this in some ‘hypothetical’ centrifugal device, so that with a slow motion camera, and some clever stabilization, editing, it would be pretty cool to see if that could work.
I wonder if it would work in zero-g...
Nothing, just stick the rotating bucket on the side of a rotating circular turntable.
@@VikingTeddy gravity is why the liquid doesn't fly away. It's still a mirror if it's sloshing around in the air, but not a very useful one. Liquid metal in space would tend to form wobbly globules...like the thick stuff inside a lava lamp, but reflective.
As for the ideas to put the turntable on a turntable, you get uneven surfaces due to compound rotation, blurry (smeared) images of the moving target, or both. Photo exposures are fast OR crisp. It's very hard to get both. This is part of why movie footage and slow-motion is so heavily edited. Trying to do astronomy or see anything scientifically useful with this setup while inside a centrifuge would be a very expensive way to get blurry, streaked images. Cool effects...maybe?
James says they _have_ to be pointed straight up...because they really do.
I'm kind of curious if you could spin up your liquid telescope up to speed and get it to the right shape and then flash freeze it so you can then point it at other directions?
Most likely the expansion / shrinking of the material will not make this work. Unless you take that in account somehow by adjusting the speed
I don't think the surface is gonna freeze and remain shiny.
thats sounds like too complicated, just use electricity to give it a shape
What if the liquid was made in layers, each one made separately? This would prevent the imperfection of expansion and shrinking.
Also, you could make the layers and cover it afterwards, so the surface would always remain shiny, even when the base material isn't suitable.
Rather than freezing a spinning liquid metal, we might as well use a concave mirror made out of a metal like Stainless Steel, which I guess would technically be a frozen liquid metal 😂
Thanks for your channel! Seriously, you made my day!
Your explanations are superb!!
I’m pretty sure they do something like that for very large telescopes. They spin molten glass to get it into the general shape.
Dude your way too cool for school. I wish I had a friend like you that I could talk to about obscure concepts, philosophy, science and crazy
"what if's" that 95% of my social circle just doesn't get or see any benefits in discussing.... Just for shits and giggz. Even better then getting outta the house to try to find and experiment to demonstrate what ever it is we were talking about. Thanks for sharing your valuable time knowledge and positive energy with the world. I hope our paths crossed some day
Same here. Badly in need of a friend who has interest in physics, biology, geology, history etc. etc. that I have interest in. 😔
Hey @TheActionLab
It is stated in the beginning that focusing light from a large area onto a small one gives a magnified image.
This might need some correction. The animation for the telescope in shown in the first 10 seconds actually says that the ratio between the focal lenght of the parabolic mirror and the eyepiece gives the magnification.
Using a large diameter aperture definitely collects more light and phsically allows for higher usable magnifications for a telescope.
Hello! I love you and I've watched all you videos, and this one was at least top 5. Great stuff!!!!
Very cool! This actually answered a question I had prior when I saw someone doing a little spinning demonstration. So it is indeed a parabola, which makes perfect sense.
Very interesting concept! I've never heard of using a rotating metal to make a mirror.
I really enjoy listening to your awareness of things that are old.
I used this technique with epoxy resin to make a parabolic reflector for a microphone. The surface finish was not good enough for optical work but at audio frequencies it is perfect. Much like radio telescopes do not need optical finishes.
Great channel!
Could you make a lens by casting resin on top of spinning galium or mercury?
If you spin it and let it cool, will it keep the shape of the perfect parabolla or will it shrink and distort?
That's interesting !
My assumption are that it will shrink as it cools down thus making it loose its paraboluc shape
Also it mas shrink uniformly so the para bolic shape will be retained
Here is something useful and important to know 👉 The Connections (2021) [short documentary] 🔥
I really amaze how he come so interesting topics most of us naver heard before so frequently and explain amazingly
Thank you for sharing your content in both english, and Spanish.
A Mylar sheet with vacuum behind it is also a good way to make a parabolic mirror!
Not as good as the sides and the middle experiences different amount of stretching making the edges wavy. But depending on your quality needs you might find that if you oversize the dish the middle part might be good enough / large enough for your needs. Then you just mask out the bad parts.
Could you build a mirror like that using a low melting point metal, spinning it while in liquid state and then retire the heat source while still spinning, so it can retain the shape? Then you can coat that with any silvery sustance to make it reflective, just like mirrors are built out of regular glass.
Someone else here mentioned that that's actually a technique used in parabolic mirror production!
I tought the same thing.
Yeah for a low cost diy mirror you can probably use wax and then use electrolysis to nickel-chrome coat it.
I wonder how well it would compare to a bought mirror.
But you can control the temperature fairly well with an inexpensive heater in a closed room, bring the room to 40-45C and then pour the molten wax, then just let the room cool down naturally so convection is a non issue.
The problem with metal mirrors is that they don't last very long. You quickly get tarnishing of the surface and trying to polish it off will ruin the optical finish. Glass mirrors also tarnish, but they can be easily washed and recoated without causing damage.
I for the most part always enjoy your content.
Thankyou so much. Your videos are always calm yet interesting and entertaining. I don’t know why but I find the calmness soothing and you always help me sleep. Thankyou!
Just a thought. Maybe your light source could have been projecting a simple shape like a triangle or 5-point star to enhance the resolution of the object and demonstrate the affect of the imperfections of the gallium/turntable.
Ah true, that could also be a factor along with what he said.
i was just talking about this couple months ago, i didn't know it existed, but i understood huge problem with lens scopes, the light required to curve is solely dependent on the size of the IN lens and the distance travel length to its curve in point, so liquid could be the best replacement...man i felt genius , clearly didn't know it existed.
It was still smart to come up with the idea on your own. One time when I was trying to understand horsepower I got to the point where I thought “wait, doesn’t that mean that a horsepower measurement has to be at a specific RPM?” I was super excited to find out that I was right, because it meant I understood the physics enough to come to a correct conclusion. Not exactly advanced physics but I was pretty proud of myself haha.
I have came up with quite a few ideas but found out that others have done those way before. Like falling water display showing time etc, derived equations for time dilation and length contraction from specific relatives two postulates, laser oscilloscope, spin moulding some rings from polythene bags in a cotton candy spinner, electrolytic heavy isotope enrichment, And quite a few others. Btw i don't feel happy to find out that others have beaten me to the punch
That's amazing, thanks for sharing!
Hey man! Your content is brilliant amazing and awesome. It even uplifts the mood!
great demonstration!
would be interesting to use some epoxy instead of liquid metal. then coat it shiny after solidifying.
Interesting thought.
Can we mix the gallium or mercury with epoxy and spin it to the desired focus as it hardens?
It's the other way around: the faster you spin, the shorter the focal length.
Exactly. He wrote the mathematical relationship correctly at the end, but said it the wrong way around several times.
Here is something useful and important to know 👉 The Connections (2021) [short documentary] 🔥
You always have amazing content. One of my favorite channels to watch on RUclips. Thank you as always for your content💞😊💞🧐😌
This was AWESOME!! ❤️🙏🏻
Just a suggestion, can you pour a clear resin over the gallium while rotating so it's cure and keep the gallium in the parabolic shape so it can be used in telescopes without need to be kept rotating?
@@markh.876 What if the gallium floats over the resin as it may be heavier because it's a metal, leaving just a shiny coat at the surface of contact between the resin and the gallium after the curing of the resin🤔🤔
@@markh.876 Or just spraying any reflective coat to the parabolic shape cured resin which was left cured while rotating with the same method
@@markh.876 that’s why ppl use phase conjugate mirrors. So the outbound distortion cancels the in bound.
There are lenses made out spun epoxy that hardens while spinning that are thin metalized.
At that point, just spin the liquid glass. I'm pretty sure parabolic mirror manufacturers already do that.
I remember watching another video on making such a telescope. They mentioned the best place for it would be a moon base. To get around the limited directionality.
Hmm. Wouldn't 20x stronger tidal forces on the surface of the moon warp the lenses too much?
and the sticky dust...
@@CanalTremocos I'm pretty sure tidal forces on the moon from the earth can be ignored since there's only 1 side facing earth all the time. Also for dust...there are materials which are impermeable to solid matter but allow light through them.
@@CanalTremocos or it sounds like you're confusing tidal forces with gravity, one maybe caused by the other but only gravity gets stronger the closer you are. The tidal forces stays the same unless the object actually increases in mass.
great video, zero BS. thank you James. good job.
This was so innovative and mind blowing !
I once built a 12 inch telescope with my bare hand using mercury and glass. I used 2 glasses rubbing against each other for building a curved shape. It took me months to finally create one and man that was so satisfying!
Have you experienced mercury poisoning?
@@kriptomavi presumably the mercury was not internal, which is where it's poisonous. Check out Cody's Lab for some great mercury experiments (like floating an anvil...yes, iron floats) and debunking some of the phobia. He is very careful with it in order to keep from contaminating his property, but touching with unbroken external skin for short periods is not generally dangerous. Breathing, eating and contact with cuts or abrasions would be a potential problem.
It feels like you move the complexity of grinding perfect glass into the complexity of the engineering of a perfectly balanced rotating mechanism that needs to run for the lifetime of the mirror. But if people are building these things I assume its worth it.
Very Timely - you've answered my question of how liquid mirror astronomical telescopes work -- old git, UK
Hey Action Lab,more good material as always. By the way, you are slowly getting a cool Ronin Toshiro Mifune hair style now.
As someone who is into astronomy, I really hope someone can figure out how to make high quality mirrors for a cheap price, it's the main thing that makes the hobby so damn expensive.
For Newtonians which are not too small, it is usually the equatorial mount (I don't like Dobsonians).
This has been known for quite a while. Thought to do it some years ago, but didn't get around to it. So you might want to try using a casting epoxy resin, have the front surface aluminized and a protective overcoat applied.
wont be good for optical applications but will be good for other light focusing applications - more expensive, involved, and time-consuming, than alternative methods (like mylar pulled into shape by a vacuum)
What about using the mylar as a - ve mold for resin bu pushing insted of pulling it?
Cool video! I learned something new today, thank you.
Wild dude! Thanks!
Do they not use a prism to get total internal reflection when they are making a telescope as we will get 100 % of the image instead of some of them being absorbed by the mirror
It's really complicated , first , same concept of lens telescope applies , the weight of such a large prism would weigh down the shape and ruin the magnified image as it will be out of focus , second, the earth's atmosphere makes images kinda distorted no matter how accurate your mirrors are , for this reason , the mirror telescopes mirror is set on top of servos that can slightly flex the mirror to compensate for it. Check out the new series of extremely large ground telescopes using mirrors ,
how does such a telescope look like? Maybe they use both, the big one to focus the light, then prisms to redirect it?
Maybe it’s because the light need to get into the prism to have a total reflection and get out of it. Since we can’t ensure that light will always be perpendicular to the surface of the prism, the process of getting in and out will separate light into different colors.
Why don't they just use a plastic reflecting surface
Here is something useful and important to know 👉 The Connections (2021) [short documentary] 🔥
4 minutes and 20 seconds 🗿
lol
Imma smoke Rightttt at the end 🤣🤣
🗿🗿
Share to the left…..
Puff... What?
Did you try this in the vacuum chamber after editing this kickass episode??
Also a great way to distort time and gravity...here on earth that is ? Make a shiny mirror resin that's partially transparent / translucent and let it cure while it's spinning... Add small amounts at different speeds so each cone gets smaller or larger depending on cadence/rpm . After they cure stack the inside each other (Matryoshka Dolls)...... have a look?
You see London , you see France you might see ??
One of our favorite episodes of all time on this awesome channel!
Thanks for good old science mixed with passion and creativity.
You rock
This channel never ceases to amaze me 👏👏👏👏 I love every single video and I love learning from them. A big hug from Argentina 🇦🇷👏
i would use mercury but lets try something a little less toxic
i have here hydrochloric acid
Next step: Convert this liquit (doesn't need to be a mirror) into a smooth/"flat" solid while it is in shape to create a molde. Then create a negative modle from that to create a perfekt mirror everytime. Is that possible?
Pour some UV sensitive resin on top of the spinning gallium and then hit the resin with UV for around 10-20 seconds until cured. The cheap $20 curing lights on amazon will work for curing, and they have the 3d printer resins.
What they actually do is just spin a furnace holding a glass blank up to the speed needed to make the parabola they want, then cool it down slowly to avoid flaws, before grinding any imperfections and then buffing it to reflect.
And that's a gross oversimplification of how to make a telescope mirror.
You are a Wonderful Genius. Much Love and Respect to You.
Great work!
Largest liquid mirror telescope is being built in India...
1:28 super simple
I'm glad that this is a real science video :)
Wow, I was just explaining this to a guy last week. He was showing one of those great big stone bowls from Japan. Thanks good video.
Thanks for the info Samari Jack.
Very interesting, thanks!
Awesome content as usual 👌👍🙏🙏😊
Absolutely amazing 👍
Thanks for verifying exactly what I imagined might work. Cool video.
Very interesting thanks, never disappointed.
Good idea, Good innovation !!!
Thanks , I was very confused and irritated with my gallium, what to do with it , but now I finally found this video, 👍👍👍
Vacuums have been used to bring spherical mirrors into a parabolic shape, as has gluing rubber to the back and pulling the rubber back with an attached bolt, putting the spherical mirror under tension.
Great video! More optics experiments
awesome! very excited!
I love these brain stimulating video's. Thank you sir for help making this planet a bit less dull.
I love the simplicity of the solution
I love this video. Thanks
Would it be possible to run a turntable in a cold environment, allowing the liquid to freeze while in that shape? I know machinery can be temperature sensitive, but even gallium should freeze/ solidify at a reasonable if chilly room temperature, iirc? And you'd want to do so slowly, to prevent bubbles as much as possible, I guess.
This was a great learn
Refractive lenses in telescopes are constructed with 3 different lenses (usually air gapped) ground specifically to bring the 3 primary colors (red green and blue) to the same focul point.
The mineral fluorite is used in the manufacturing of these (high end quality) lenses to redruce the dispersion of light.
1:15 - That also bent in the sides because of the curve on the sides of the container, it's like the perfect Pringles chip mold.... LoL
Excellent!
Thank you 👍
Great video!
I enjoyed this and the transparent sodium video
When I was younger.. about 30 years ago... I wanted to make a mirror from slow curing epoxy and to spin the bowl with epoxy I wanted to use gramophone... Unfortunately the cost of the needed epoxy was to high for a young me :) Happy to see the same experiment here.
we can try freezing the metal it is spinning, and store it in low temperature so that we need not to keep only upright
distortion driven by gravity field uniformity (spherical source approximating point source) and atmospheric resistance? thanks for the video. spinning fluid lenses are so neat.
Use liquid nitrogen or even just dry ice to freeze the gallium/mercury when it's at an appropriate focal length, then stop the rotation and use it as a parabolic mirror that stands up to any orientation of the gravitational field as long as you keep it frozen. You could even ship it to space frozen and only keep cooling it in order to avoid it melting from radiant heat sources like the sun and stars.
There is something like: Gallium Liquid Mirrors
Oh man, this one was awesome
You could stabilize it in space by having something rotate the liquid mirror around an axis (Like swinging a water bucket upside-down 🪣)
Genius, thank you.
In the Dune novels by Frank Herbert there was mention of binoculars using a special optically clear oil lens which was oil that was sealed in a tube and shaped in a suspensor field to form a lens of unmatched precision and clarity.
Why not use some sort of resin with a tuned speed per desired parabola, once activated and spun it should harden in the "formed" shape then coated with a reflective surface?
3:18 This is Exactly how Stars Shine and scatter but always stay constant ! Oooh ! This answers a massive Qualitative Question
I've grown to really like this guy. Wish I could chat and learn
bwahahha i love your videos man, but i swear to god all it took was me to read the subtitles on the preview video to know this was one of your videos
I had the this idea back around 2005, don’t know how far this goes back, but cool that I was right.
if you were to spin this whole spinning setup around a focal point which was made of 45 angled mirrors pointing out, could you make a similar setup that can be aimed in non-up directions? I guess you'd have to spin it pretty fast in order for the impact of gravity to not distort the image too much