@@flux.aeterna The inventer struggled for long time to make such a shape. One morning he was stirring his coffee and saw the surface of the coffee had the shape he needed. So insted of pouring the polymer into still molds, he poured it in spinning molds.
I don't think this is true. Don't know where you have this from, but I looked it up and every mass production facility uses the standard mold & extrusion process.
The reason the spinning cup of water makes the shape of a perfect parabola is because the water at the center is almost stationary while water at the edge is moving very fast as the centrifugal force gets larger as you go farther from the center. If you go twice as far out, the water moves twice as fast so the slope of water increases linearly as it goes farther from the edge. And a parabola is the shape has a slope that changes linearly.
@Yulenka- The speed of what? Im not sure I understand your question. The cup is spinning, because of that, that water is being pushed towards the outside because centrifugal force. But the relationship of the slope of the water leaning against the glass wall in respect to it's distance from the center is linear, so it must make a parabola.
@@maxhagenauer24 I followed your explanation until "the water moves twice as fast so the slope of water increases linearly as it goes father from the edge". I understood that the speed increases linearly, and that linear slope increase makes a parabola, but I don't know how the latter follows from the former. Why couldn't the speed increase linearly in a different shape?
Most really large glass mirrors are spin cast these days. You can reduce the amount of glass needed by 80%, which makes it lighter and less prone to distortion under its own weight.
@@adammontgomery7980 Yes, it does form a parabola which vastly reduces the amount of work you need to do to get a perfect figure. The only problem is you need a very big oven that can be spun at high temperatures for weeks.
They actually use this technique for making the concave primary mirror for large telescopes. The glass is spun up in a device while it melts and the temperature is then gradually decreased over quite a few days until the whole unit is at a safe temperature that it won't crack or warp. Maintaining the precise rotational rate is absolutely crucial. There is an excellent video online that films the interior of one of these devices as the primary is being made. It's in fast forward and is an astounding piece of footage. .
This isn't a new technology, lol. It was invented in the 1800s. And think about what you just said. How exactly you do you think a handheld camera would work using this? Lol. You can't aim these anywhere but up. They work perpendicular to gravity. They wouldn't work in something you were trying to constantly point everywhere in whatever direction you want. Not to mention it needs to spin....
The best part of a gallium mirror is that it self repairs. Lets say you dropped a wrench in it, you could pick up the wrench and the gallium liquid will just regulate. No cracked matter. The problem here would be contaminates from touching the gallium.
@@HandsomeBastard In photography, it would likely cause clarity issues if contaminates were to be on the surface. Similar to a smudge on a mirror. I'm not an expert, but I would assume they attempt to keep that gallium as pure as physically possible.
@@canadianman000 Yep, I remember reading about filtering it somewhere, but that definitely works too > Not mentioned in the article is the ease of cleaning mercury, particularly since all common objects float on it. The container is stopped, and a lead-weighted rubber tube is used to drag debris and mercury oxide to an edge of the puddle, from which the debris is aspirated away. The mirror is then restarted.
This procedure of spinning is also used to create some parabolic glass mirrors. The crucible where the glass is melted is spun at slow speeds to give the mirror a parabolic curvature.
The mirror lab at University of Arizona does this, but only to rough-in the mirror shape. They still need to polish the mirror surface before metalizing it. (According to their website, they've made 8.4meter mirrors this way.)
@@Sembazuru This is actually where I learned about this! I believe the University of Arizona Mirror Lab now has public tours available again (they had been stopped for a while during COVID, I believe), so if you (or anyone reading) ever happens to be in Tucson, Arizona, you should definitely take a tour. It's an incredibly impressive lab!
Thank you for sharing this knowledge! I wasn't aware of math, I didn't even know the word parabola. 74 years old and still learning! I'm so lucky to have this wonder-filled life.
Well, there isn't a lot of drawbacks, just one - since it's always centered around the center of gravity, it basically cannot move in any direction. So you can only observe what's directly up (and thus it can't track any celestial objects)
@@FourOneNineOneFourOne the maximum size of the lens is limited too, because the rotation required to produce a smooth mirror with no blemishes or turbulence would be too high to be able to be maintained. Also, some liquid metals that are used contain Mercury or thallium making them somewhat toxic to be exposed to.
@@spiderdude2099 I think they've already made some pretty large liquid telescopes. You're right about the toxicity. The largest telescopes don't use either one because it's just as difficult to have it made out of mirrors, although they only capture radio and microwave frequencies.
The trick would be to use a flat mirror to bend the light from Mercury to reach the mercury, since Mercury would never be directly overhead, and the mercury mirror couldn’t be tilted.
@@ezekielbrockmann114Yes, you can tilt a liquid mirror that is designed to be tilted, but you’ll then need to calculate and subtract the warping created by unequal gravitational impact across the mirror’s surface. The impact of local gravitational variances across a perfectly “horizonta”l* mirror is so small as to be negligible at this scale. You’d have to get much, much larger for local gravitational variances to be meaningful. *perfectly tangential is more appropriate than horizontal, as we are talking about a tangent plane intersecting with the surface of the curved Earth. I chose to use horizontal for the clarity of the concept, though, as most people will understand that from regular experience, rather than what “tangential plane to a sphere” means.
they also make large glass mirrors the same way, except they rotate moltenglass and continue rotating until it cools and solidifies - then it is polished and coated
It can be done. I read an article in Scientific American back in the '90s with instructions. At the time they recommended using a record turntable that is designed to spin at a consent speed for a long time.
@@seno7904 Resins are like a glue, so they cure over some period of time depending on what type you're using. Also, the viscosity doesn't effect how much force it takes to spin, since the entire container is moving along with the liquid inside. I don't see how it would get harder to turn as it starts to set up, or why it would have to happen quickly, so long as you have something that could spin it at a constant speed until it hardens.
@@ctdieselnutI’m not entirely sure, but I’d think that you would need to spin it faster as it hardens to keep the same shape due to the viscosity making it not flow as easily upwards at the edges
As long as it doesn't slow down the resin wouldn't suddenly change shape thus a constant speed until the resin is fully cured is all you need despite any changes in viscosity
The Palomar Observatory 200 inch telescope has a mirror made of Pyrex glass (a new invention at the time) and as the glass was melted into the mold, they spun the mold to create the parabolic lens they wanted. Then they polished the glass before applying the reflective coating. Then it was polished again. The level of polishing that mirror initally had before installation was so percise that if you made the amearth as polished as the mirror, Mt. Everest would be 6 inches tall
This is actually done when casting large glass mirror blanks. The desired final figure is usually not quite a parabola, and error is induced anyway when the glass cools and changes phase, but it greatly reduces the time needed to grind and polish to the final figure.
No! That's a common misconception. It decreases performance and contrast, but the speck will be out of focus. It takes a lot of dust or a lot of light to be noticeable.
This is incredible. There's nothing more fascinating amd satisfying to me than an extremely elegant, simple solution to a seemingly very complex problem. This is also a fantastic scientific example of something Bruce Lee said that changed my entire outlook on intelligence: "Simplicity is key to brilliance." A very complicated solution that works is still very complicated, not easy to replicate, often unreliable because of how complex it is, etc. But to have the intelligence to find a solution based in simplicity is actually a higher pursuit, in my mind. Anyone can Jerry rig some overcomplicated solution, but simplicity and elegance are actually harder to come by sometimes because they take such creativity, skill, and depth of understanding.
@@stephenbeck7222but this case does have an outward tension in the form of a centrifugal (inertial) force, and it grows as we travel towards the edge, allowing the edge to “hold” more liquid than the middle
It's a parabola for the same reason objects in free-fall follow a parabolic path: whenever a bunch of particles are given some energy to spend (in this case, energy due to rotation) and are simultaneously under the influence of gravity (and perhaps some other hydrostatic forces), the resulting distribution of those particles will minimize one ubiquitous and well-understood quantity. In the case of a particle in free-fall, the energy to spend is kinetic energy, and that quantity to minimize is the difference between its kinetic and potential energies.
you could - spin UV-resin in a cup to create the lens shape you want and then coat with conductive link and then Plate with silver to create a cheap lens.
last year i had seen a project by first year students in imperial college London utilising this to create their own telescopic mirror. thank you for reminding me of and explaining this to me!
I’m interested to hear about the longer term costs. Obviously as stated on the surface level it’s cheaper, but how does the instillation of a large enough engineered surface to move all the liquid, compare to that of the mirror, or the price associated with keeping the liquid moving the entire time the telescope is in use
It's no big deal. It's just a turntable, and it doesn't even need to be precise as the surface of the liquid will always form a parabola with respect to gravity. Also, the turntable doesn't have to rotate very quickly because the parabola needed is shallow. The only thing that would need to be kept consistent is the rotation speed, but that's easy to do given the amount of mass involved. The drawback of a telescope like this is that it can only be pointed straight up.
@@robertmiles9942the rotation has to be very precise, any unbalanced "wobble" would completely ruin your mirror surface. Remember to work they need to be "smooth" to less than the wavelength of light you're trying to capture IE a perfect parabola accurate to around 15-20 billionths of a metre, millionths of a millimetre. So yes any vibrations/wobble is going to ruin your telescope... There's a reason grinding telescope mirrors is expensive and difficult.
The biggest problem isnt making your spinning mirror, that's hard but not as hard as the next part. A spinning liquid mirror is centred looking straight up, unless what you want to look at is straight up that's going to be a problem. In any other direction you're going to need a series of moving mirrors and motors etc to redirect the light from where you're looking to your nice spinning mirror. And all wavefronts need to reach that mirror at precisely the same time.... That is very very non trivial task.
There was a mad scientist/ inventor column called Daedalus each week in New Scientist when I was at school in the 70’s. This idea came up one week. No idea if it was original though. I particularly liked their idea of sinking battleships by injecting very small bubbles in the water to reduce the density.
I like how he's low-key using a container with a rectangular footprint to show the parabolic shape in 2D-like way (the rotating blue liquid) before moving on to the more application-friendly usage (with cylindrical containers). Just goes to show how he's a great science communicator. 🤩 👍
Liquid lenses but not by rotation but by electric current are already common in the manufacturing industry, really fast focusing abilities and changing they focal length
I think if you just blast the bottom/side of the bowl with a hair dryer or space heater it'll prevent that film from forming and yield a clearer reflection.
It's funny that Feynman's stance (and forehead?) are so recognizable that you immediately know it's him in a picture where the lens was very much not focused on him.
I saw this being used on Mythbusters on the episode about Archimedes heat ray. The first half of the episode was talking about how the mirror that focuses the light could have been made, and then a segment on looking for fans that would like to do a competition on making one. There was a large scale and a small scale competition. For the small scale competition, they had two teams, one girls and one boys, and the boys team first used the spinning liquid technique to create a parabola for their mirror. However, that didn't work out and so instead they used a mirrored film stretched over a vacuum chamber, which also makes a very effective parabola.
I love how you tell me the equation in the same way you'd tell me where the fruit is at the store.... like I completely understand what's happening 😅 thank you
Spin mercury in a cryogenic condition to simulate the temperature of space. Heat it to make it flow and cool it to let it freeze solid, use its reflective metalic surface to your advantage
And they wouldn’t be prone to lens damages like glass telescopes, right?
correct! And no color aberrations like in glass lenses.
just if someone spills their coffee in it.
Someone trips and falls onto it. An inconvenience with gallium, but god help them if it's mercury. @@lolwtnick4362
Definitely!
@@ActionLabShortsDo you think they are the future of telescopes?
Wizards and their scrying bowls.
Scry 2
24825d11h
248,2,5d11h
😆
Scry harder.
This is also how contact lenses are made, they spin a liquid polymer as while it's becoming solid.
Wtffff this is black magic
@@flux.aeterna The inventer struggled for long time to make such a shape. One morning he was stirring his coffee and saw the surface of the coffee had the shape he needed. So insted of pouring the polymer into still molds, he poured it in spinning molds.
The more you know 🌈
@amurape5497 if that's true that's a great story. I will look up later to see if it is! Thanks for sharing!
I don't think this is true.
Don't know where you have this from, but I looked it up and every mass production facility uses the standard mold & extrusion process.
The reason the spinning cup of water makes the shape of a perfect parabola is because the water at the center is almost stationary while water at the edge is moving very fast as the centrifugal force gets larger as you go farther from the center. If you go twice as far out, the water moves twice as fast so the slope of water increases linearly as it goes farther from the edge. And a parabola is the shape has a slope that changes linearly.
Nice
Coriolis force
What is the connection between the speed and the slope though?
@Yulenka- The speed of what? Im not sure I understand your question. The cup is spinning, because of that, that water is being pushed towards the outside because centrifugal force. But the relationship of the slope of the water leaning against the glass wall in respect to it's distance from the center is linear, so it must make a parabola.
@@maxhagenauer24 I followed your explanation until "the water moves twice as fast so the slope of water increases linearly as it goes father from the edge". I understood that the speed increases linearly, and that linear slope increase makes a parabola, but I don't know how the latter follows from the former. Why couldn't the speed increase linearly in a different shape?
"Whoops, I spilled my mirror."
Nobody expects the Spanish Inquisition.
.
Whoops, I swallowed mercury 💀
@@AlexGeek it wasn't mercury, I'm afraid
@@Pootie_Tang It was Uranus
@@Unwanted_truth_ I wondered what was that itch I feel
Well, gallium isn't as bad as mercury@@Pootie_Tang
Most really large glass mirrors are spin cast these days. You can reduce the amount of glass needed by 80%, which makes it lighter and less prone to distortion under its own weight.
Does the molten glass form a parabola? I guess some polishing and aluminizing would give you close to a perfect mirror.
@@adammontgomery7980 Yes, it does form a parabola which vastly reduces the amount of work you need to do to get a perfect figure. The only problem is you need a very big oven that can be spun at high temperatures for weeks.
There is a good video about spin casting the mirrors for the Giant Magellan telescope at the University of Arizona.
and it's also 5000% more likely to break 😂
The back of the mirror is cast into a honeycomb shape to further reduce it’s weight.
They actually use this technique for making the concave primary mirror for large telescopes. The glass is spun up in a device while it melts and the temperature is then gradually decreased over quite a few days until the whole unit is at a safe temperature that it won't crack or warp. Maintaining the precise rotational rate is absolutely crucial.
There is an excellent video online that films the interior of one of these devices as the primary is being made. It's in fast forward and is an astounding piece of footage. .
how has this dude not ran out of science experiments
Science is a hydra - at the current stage, every answer creates at least two more new questions.
Amazing. Using physics to prevent manufacturing flaws in the lense, while also being able to adjust it on the fly.
I saw this without reading the title. I thought "how nobody havent used this yet on a telesc... oh they did"
yeah, except you can only use it at zenith (pointing straight up)
@@mariusflorea1984but in space there is no up, right? So it could still work outside of earth’s environment
@@redwiltshire1816 yes, but also 0 pressure and gravity to keep the liquid flat
@@mariusflorea1984 what if you apply pressure to the liquid keeping it in place then spin the liquid
Parabolic mirrors are really good at reflecting sunlight and cooking food
well, concentrating light is the point of those
are you talking about the solar death ray guy?
@@Nimpp he uses a big fresnel lense from an old tv, but there’s a couple different types of solar cooking contraptions
@@noobartz0890point 😂
Who would win, the entire Persian naval fleet, or one glass bowl
Just finished hand grinding/polishing my own 6" glass mirror. Telescope optics are quite fascinating, thanks for the video!
imagine future photocameras using liquid spinning lenses, that would be cool
Or lasers. This could be the precursor to the Death Star.
A camara that can only point straight up.
or gravitational lenses containing thousands of galaxies
This isn't a new technology, lol. It was invented in the 1800s. And think about what you just said. How exactly you do you think a handheld camera would work using this? Lol. You can't aim these anywhere but up. They work perpendicular to gravity. They wouldn't work in something you were trying to constantly point everywhere in whatever direction you want. Not to mention it needs to spin....
@@klausolekristiansen2960 you can use a second, flat mirror, to make it point almost anywhere. But yeah, it cannot be handheld.
The best part of a gallium mirror is that it self repairs. Lets say you dropped a wrench in it, you could pick up the wrench and the gallium liquid will just regulate. No cracked matter.
The problem here would be contaminates from touching the gallium.
I too keep myself from sleeping with that same problem on my mind - what about the contaminants from touching the gallium.
@@HandsomeBastard In photography, it would likely cause clarity issues if contaminates were to be on the surface. Similar to a smudge on a mirror. I'm not an expert, but I would assume they attempt to keep that gallium as pure as physically possible.
@@STaSHZILLA420They can drain off the gallium for cleaning.
@@reddragonflyxx657 Alternatively, you can just cross the surface with a wiper. Should be enough to drag surface contaminated out.
@@canadianman000 Yep, I remember reading about filtering it somewhere, but that definitely works too
> Not mentioned in the article is the ease of cleaning mercury, particularly since all common objects float on it. The container is stopped, and a lead-weighted rubber tube is used to drag debris and mercury oxide to an edge of the puddle, from which the debris is aspirated away. The mirror is then restarted.
I have no idea what magic man is saying, but I like it.
Okay right?! 😆
Me too. But I now can somewhat joke about water making a cheaper glass material. A Did You Know trivia maybe.
Shatterproof too. Convenient.
great idea, if you can control the vibrations you can theoretically have a smooth surface down to the atom
Bro opened a portal 💀
Mirror portal be like: "You spin me right 'round, baby, right 'round
, like a record, baby, right 'round, 'round, 'round".
This procedure of spinning is also used to create some parabolic glass mirrors. The crucible where the glass is melted is spun at slow speeds to give the mirror a parabolic curvature.
shit that's ingenious
Look up any big mirror telescope or space telescope, they are never pure parabola because of third order coma aberrations.
The mirror lab at University of Arizona does this, but only to rough-in the mirror shape. They still need to polish the mirror surface before metalizing it. (According to their website, they've made 8.4meter mirrors this way.)
@@Sembazuru This is actually where I learned about this! I believe the University of Arizona Mirror Lab now has public tours available again (they had been stopped for a while during COVID, I believe), so if you (or anyone reading) ever happens to be in Tucson, Arizona, you should definitely take a tour. It's an incredibly impressive lab!
@@Sembazuru The Keck mirrors were made this way
Dang that’s crazy!!!! I feel like this could be used in a science fiction movie. Leaning over a pool of twirling liquid to look at your reflection.
Thank you for sharing this knowledge! I wasn't aware of math, I didn't even know the word parabola. 74 years old and still learning! I'm so lucky to have this wonder-filled life.
There are obviously a lot of drawbacks, so this approach is not super popular among astronomers. But it definitely has some cool benefits.
Well, there isn't a lot of drawbacks, just one - since it's always centered around the center of gravity, it basically cannot move in any direction. So you can only observe what's directly up (and thus it can't track any celestial objects)
@@FourOneNineOneFourOne the maximum size of the lens is limited too, because the rotation required to produce a smooth mirror with no blemishes or turbulence would be too high to be able to be maintained. Also, some liquid metals that are used contain Mercury or thallium making them somewhat toxic to be exposed to.
@@spiderdude2099 I think they've already made some pretty large liquid telescopes. You're right about the toxicity. The largest telescopes don't use either one because it's just as difficult to have it made out of mirrors, although they only capture radio and microwave frequencies.
@@FourOneNineOneFourOneso what are they using to make these liquid telescope mirrors if not gallium or mercury?
@@koriw1701That's something that's actively being worked on as they want to put one in space!
* That moment when you're looking at Mercury in a mercurial mirror.
The trick would be to use a flat mirror to bend the light from Mercury to reach the mercury, since Mercury would never be directly overhead, and the mercury mirror couldn’t be tilted.
@@gregswank4912 Couldn't it spin fast enough to aim just above the horizon?
@@ezekielbrockmann114Yes, you can tilt a liquid mirror that is designed to be tilted, but you’ll then need to calculate and subtract the warping created by unequal gravitational impact across the mirror’s surface.
The impact of local gravitational variances across a perfectly “horizonta”l* mirror is so small as to be negligible at this scale. You’d have to get much, much larger for local gravitational variances to be meaningful.
*perfectly tangential is more appropriate than horizontal, as we are talking about a tangent plane intersecting with the surface of the curved Earth. I chose to use horizontal for the clarity of the concept, though, as most people will understand that from regular experience, rather than what “tangential plane to a sphere” means.
they also make large glass mirrors the same way, except they rotate moltenglass and continue rotating until it cools and solidifies - then it is polished and coated
😮😮😮 the focused light LOOKS exactly like the stars in the firmament!
No it looks like a white light being reflected. Actual stars look very different
So it's cheaper to buy some mercury than to buy a massive mirror? Ferb I know what we're doing today!
that's not mercury but ok
@@vintage-radio Looks like mercury to me.
@@pandapip1 maybe it's because they're both metals that are liquid at room temperature
@@vintage-radio He used a glass beaker, so I don't think it's gallium.
@@pandapip1 fair enough. It must be mercury
Interesting! Wonder if this could be a method to make resin lenses at home without having to machine and polish them?
Possibly if you can flash freeze it into position otherwise as it hardens it will become harder to spin
It can be done. I read an article in Scientific American back in the '90s with instructions. At the time they recommended using a record turntable that is designed to spin at a consent speed for a long time.
@@seno7904 Resins are like a glue, so they cure over some period of time depending on what type you're using.
Also, the viscosity doesn't effect how much force it takes to spin, since the entire container is moving along with the liquid inside. I don't see how it would get harder to turn as it starts to set up, or why it would have to happen quickly, so long as you have something that could spin it at a constant speed until it hardens.
@@ctdieselnutI’m not entirely sure, but I’d think that you would need to spin it faster as it hardens to keep the same shape due to the viscosity making it not flow as easily upwards at the edges
As long as it doesn't slow down the resin wouldn't suddenly change shape thus a constant speed until the resin is fully cured is all you need despite any changes in viscosity
The Palomar Observatory 200 inch telescope has a mirror made of Pyrex glass (a new invention at the time) and as the glass was melted into the mold, they spun the mold to create the parabolic lens they wanted. Then they polished the glass before applying the reflective coating. Then it was polished again. The level of polishing that mirror initally had before installation was so percise that if you made the amearth as polished as the mirror, Mt. Everest would be 6 inches tall
Tried this outside now I can see the sun where ever I go.
There's a technique used to produce cpu with liquid too. Pretty neat using nature itself
Chill it while spinning it to hold the parabolic shape
This is actually done when casting large glass mirror blanks. The desired final figure is usually not quite a parabola, and error is induced anyway when the glass cools and changes phase, but it greatly reduces the time needed to grind and polish to the final figure.
Its been a very cool 10 year or so since i first seen your experiments and they never succeeded to bore me i wish you were my science teacher.
Very useful to be able to only point it straight up.
I had no idea that liquid mirrors were already a thing. I've only ever heard them talked about in hypothetical terms.
Just a small speck of dust in that telescope's mercury and a new galaxy is born outta nowhere.
No! That's a common misconception. It decreases performance and contrast, but the speck will be out of focus. It takes a lot of dust or a lot of light to be noticeable.
@JimmyCerra even with my home telescope, I can put my whole hand in the front and still not see it, although the image gets darker
Awesome. Among a world of crappy videos, you bump into this little gem. Thanks, man!
That guy standing at the edge tho 😳
do NOT take me back to algebra 😭😭
Good news! It's only algebra until you need to do anything with it. Then it's calculus
I wonder if such a telescope would be buildable at home 🤔
probably but wont be th3e cheapest thing for one to do. you can buy gallium.
bucket of spinning mercury at home sounds like a fun idea
@@Matthew_Removeafterwashing a little bit safer and easier to get gallium then mercury I would think.
Glass optics are probably cheaper at small scale
@@poscat0x04 probably but they didn’t ask if you can build one out at home but they asked if you can build one out of Liquid Metal
Love that your channel has become more and more advanced.
This is incredible. There's nothing more fascinating amd satisfying to me than an extremely elegant, simple solution to a seemingly very complex problem. This is also a fantastic scientific example of something Bruce Lee said that changed my entire outlook on intelligence: "Simplicity is key to brilliance." A very complicated solution that works is still very complicated, not easy to replicate, often unreliable because of how complex it is, etc. But to have the intelligence to find a solution based in simplicity is actually a higher pursuit, in my mind. Anyone can Jerry rig some overcomplicated solution, but simplicity and elegance are actually harder to come by sometimes because they take such creativity, skill, and depth of understanding.
So is that what I’m seeing in the sky?
No???
I would’ve thought the shape would be a catenoid like hanging ropes?
And the fact that you can change the properties of the lens is also very useful i would guess.
the physics is different from a line-mass held at two ends
Yes I think the difference with the catenary is the lack of outward tension force here. There is only gravity and a buoyancy force.
@@stephenbeck7222but this case does have an outward tension in the form of a centrifugal (inertial) force, and it grows as we travel towards the edge, allowing the edge to “hold” more liquid than the middle
It's a parabola for the same reason objects in free-fall follow a parabolic path: whenever a bunch of particles are given some energy to spend (in this case, energy due to rotation) and are simultaneously under the influence of gravity (and perhaps some other hydrostatic forces), the resulting distribution of those particles will minimize one ubiquitous and well-understood quantity. In the case of a particle in free-fall, the energy to spend is kinetic energy, and that quantity to minimize is the difference between its kinetic and potential energies.
you could - spin UV-resin in a cup to create the lens shape you want and then coat with conductive link and then Plate with silver to create a cheap lens.
last year i had seen a project by first year students in imperial college London utilising this to create their own telescopic mirror. thank you for reminding me of and explaining this to me!
I’m interested to hear about the longer term costs. Obviously as stated on the surface level it’s cheaper, but how does the instillation of a large enough engineered surface to move all the liquid, compare to that of the mirror, or the price associated with keeping the liquid moving the entire time the telescope is in use
It's no big deal. It's just a turntable, and it doesn't even need to be precise as the surface of the liquid will always form a parabola with respect to gravity. Also, the turntable doesn't have to rotate very quickly because the parabola needed is shallow. The only thing that would need to be kept consistent is the rotation speed, but that's easy to do given the amount of mass involved. The drawback of a telescope like this is that it can only be pointed straight up.
@@robertmiles9942the rotation has to be very precise, any unbalanced "wobble" would completely ruin your mirror surface. Remember to work they need to be "smooth" to less than the wavelength of light you're trying to capture IE a perfect parabola accurate to around 15-20 billionths of a metre, millionths of a millimetre. So yes any vibrations/wobble is going to ruin your telescope...
There's a reason grinding telescope mirrors is expensive and difficult.
The biggest problem isnt making your spinning mirror, that's hard but not as hard as the next part.
A spinning liquid mirror is centred looking straight up, unless what you want to look at is straight up that's going to be a problem.
In any other direction you're going to need a series of moving mirrors and motors etc to redirect the light from where you're looking to your nice spinning mirror.
And all wavefronts need to reach that mirror at precisely the same time....
That is very very non trivial task.
But they do have a lot of error due to external disturbances?
actually no. not sa good as some other microscopes but not that inaccurate at all
that focus point of light looks like a star
The focused light looks like a Star.
Wow… I learned a lot just now. Nice topic and good presentation. Thanks!
There was a mad scientist/ inventor column called Daedalus each week in New Scientist when I was at school in the 70’s. This idea came up one week. No idea if it was original though. I particularly liked their idea of sinking battleships by injecting very small bubbles in the water to reduce the density.
Action labs always takes it to the next level with the cool facts
Those rogue pixels on the left gave me a heart attack
Humanity does not deserve the creativity and knowledge and levels of explanation that this guy has for years. I always come out thinking like a genius
How do you come up with the ideas for your videos? The variety of weird phenomena you demo is just astounding to me
Also you can change the focal point that's a huge benefit over glass.
Thats such a cool fact about liquid mirrors in telescopes!
I like how he's low-key using a container with a rectangular footprint to show the parabolic shape in 2D-like way (the rotating blue liquid) before moving on to the more application-friendly usage (with cylindrical containers). Just goes to show how he's a great science communicator. 🤩 👍
I have learned so much from you and it just doesn’t stop
This is how disposable contact lenses are made. The outside curve is set by the mold and the inner curve is set by its spin.
Never would have known this
Now I do
Now I’m thinking of that “You spin me right round baby right round” song .
I had no idea. What an interesting piece. Thank you!
That point of light looks like 2D gravitational waves when it vanished
bro that’d be the coolest way to film a music video
Liquid lenses but not by rotation but by electric current are already common in the manufacturing industry, really fast focusing abilities and changing they focal length
This is a man who could accurately judge ones TMI!
This is probably the coolest video you’ve ever made
Wow! Thankyou, I did not know such telescopes existed! You really do learn something new everyday!
*Frodo falls backwards*
"I know what it is you saw."
The most informative video in the century.
I think if you just blast the bottom/side of the bowl with a hair dryer or space heater it'll prevent that film from forming and yield a clearer reflection.
There's also the ferrofluid ones with magnetic field modulation.
"Mirrors are more fun than television"
Props to anybody who gets the reference.
"We can get a focus point of light"
*Bursts into flames*
👍 An excellent and amazing video. Very nice liquid lens. Thank you very much for sharing.
starts a fight in a telescope and pushes my opponent into the mercury tray
Which genius came up with that idea, so simple in plain sight
Seeing Feynman in the middle of context is a flex for sure 😂
It's funny that Feynman's stance (and forehead?) are so recognizable that you immediately know it's him in a picture where the lens was very much not focused on him.
Fun fact, they use fluorite and other gemstones or minerals as well that is high on the refraction index
"So the focal length of this mirror is just the gravitational constant..." Then my brain kinda melted.
If I have to pay 6000$ I want to breathe underwater and talk with fishes
this idea hit me when I was in class 12,6 years earlier,,,and also using ferrofluid
This dude stays coming w the good stuff
Remember the surface of the liquid is always perpendicular to the net force acting on it
Dude achieved the golden spiral
The spinning gallium would go hard in a music video
Incredible! Thanks for sharing 👍🏻
I saw this being used on Mythbusters on the episode about Archimedes heat ray. The first half of the episode was talking about how the mirror that focuses the light could have been made, and then a segment on looking for fans that would like to do a competition on making one. There was a large scale and a small scale competition.
For the small scale competition, they had two teams, one girls and one boys, and the boys team first used the spinning liquid technique to create a parabola for their mirror. However, that didn't work out and so instead they used a mirrored film stretched over a vacuum chamber, which also makes a very effective parabola.
If you hang a chain it makes a hyperbolic curve. I bet that's also used to create useful shapes.
Sir you speak just like my father, your words are very wise. Thank you for giving this world who you are.
It’s a shame Isaac could not have seen this. But he saw his other visions come to life.
I love how you tell me the equation in the same way you'd tell me where the fruit is at the store.... like I completely understand what's happening 😅 thank you
That focal light looks a lot like a star 😮
They also used massive spinning glass kilns to make glass lenses as well
you make great science stuff 👍
Thanks for always teaching me more stuff man
I love that I know so many random things because of you 😂
Remember when your math teacher said you'll need parabolas? Yeah...
Science Hack to getting a cheaper mirror. Most helpful hack.
This is amazing! Thanks for sharing 🙏
Spin mercury in a cryogenic condition to simulate the temperature of space. Heat it to make it flow and cool it to let it freeze solid, use its reflective metalic surface to your advantage