Why Do Spinning Liquids Make Great Telescopes?
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- Опубліковано 28 вер 2024
- Why Liquid Mirrors Make Great Telescopes
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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.
That demonstration with the blue water in a parabola was really cool
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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.
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.
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.
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
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. 😔
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.
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
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.
I've read a proposal to install a mercury liquid mirror telescope inside a Moon crater! It would gather insane amount of light, which would be very beneficial. Only downside is that it can only be pointed straight up.
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] 🔥
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?
0:51 you can get a 6 inch f/8 parabolic for around 160$ from a good supplier. The atmosphere itself will limit you before a ok mirror will.
Things do start to get insane when you want a hyperbolic mirror though.
Hey Action Lab,more good material as always. By the way, you are slowly getting a cool Ronin Toshiro Mifune hair style now.
In theory you could spin molten glass and solidify it while under the spin. I realize that would introduce some ripples in the final parabola, so it would need further grinding with traditional methods. The question is, would that be more cost effective, than griding the mirror from the scratch?
That's how large monolithic primary mirrors are often cast today.
How about cool it down while rotating. When it freezes, you can use it vertically. Or heat some other metal when rotating. Thus, it can keep the shape in room temperature.
A 6" parabolic primary in borosilicate costs ~$150 with aluminum coating. If you're going for a slower small scope, a spherical primary is just as good and costs under $100 for primary and secondary from China. They're not expensive and especially in that size are fairly easy for an amateur to make.
If the gallium were to slowly solidify, would that keep the shape it had as a liquid or would it become distorted?
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
Seems like you could use a centrifugal force in place of the gravitational one... of course then you'd have something spinning perpendicular to the centrifuge and you'd only get an intermittent image as the mirror briefly lined up with the "eye piece" in such a setup
But ya, it seems like you could make one of these that was not bound by the direction of the force of gravity
I think this would be good for radio telescopes as well, perfect metal will reflect radiowaves to a monopole antenna at the focal point.
Can you price a 1000 ft bowl of gallium?
This reminds me of the concept of a black hole, kind of the mechanics of what's going on anyways
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?
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.
the reason why they are not used is because they have to be pointed straight up. which means making a fully functioning telescope requires either making it a straight telescope that can't move from its point of origin in the sky or using it in space where gravity wont affect it much and allows the same effect to occur within a enclosed space. Either way construction out ways the benefits in both cases even though glass mirrors are expensive the material required to create the telescope isn't where as for liquid you would need to create a custom built telescope to attach it which can be expensive.
I've seen something similar done with an emergency blanket stretched over a barrel. Suck all the air out of the center and the emergency blanket will turn into a concave mirror.
How is that remotely similar?
@@BariumCobaltNitrog3n perfect concave lens to focus light. That could be turned into a telescope.
@@GeneMatheney Not a lens. A mirror. Used for cooking not astronomy. Made of plastic not glass or metal. Vacuum not gravity.
@@BariumCobaltNitrog3n You are correct, my mistake. If you pull the fabric tight enough before you apply the vacuum it will be a mirror finish. I don't know if the reflection quality would be good enough but it would be interesting to experiment with.
@@GeneMatheney The space blanket is designed to reflect radiant heat, infrared, to keep a body warm without losing heat to convection, so reflect some visible light but mostly heat (for starting fires), so isn't that great for telescopes. They can be used for sound though, picking up bird calls at hundreds of yards away.
I think I saw one guy inflate the blanket instead of vacuum, then covered it with spray foam insulation. When it hardened, the backside was a decent mirror but had some wrinkles.
With Gallium, you could spin it to exactly what you are looking for and then carefully cool it until it solidifies. Then you would have a perfect mirror as long as you keep it reasonably cool
I for the most part always enjoy your content.
The air-bearings that support these things are more interesting than the mirror.
I count myself lucky to have bought a set of mirrors from a shipment of telescopes that were damaged during shipping. I made a wonderful 6" f5 Dobsonian for under $125. Unfortunately I've since moved to a part of the U.S. that has no idea of what darkness actually is.
So the liquid mirror when spinning becomes a near perfect parabular and focuses the light accordingly? Awesome!
So a way to produce good parabolic mirrors would be to spin molten metal and keep them spinning until they cool down and become solid
Very interesting. This is one I can actually understand as the equations aren’t necessary to see what’s happening 🤪
My daughter did that for her science fair project back in 1978.
Thanks for your channel! Seriously, you made my day!
Would love to see @MarkRober making an actual telescope using lots of gallium/mercury
You should try freeze the gallium while spinning I wonder if it will stay shiny
Wild dude! Thanks!
How about creating the parabolic surface by spinning and... freezing it to incline the mirror? If not working, could it be at least a techique to create jigs for big mirrors? That reminds me of Spanish architect Gaudí and the way he designed some arches using Mother Nature to do the hard work...
I doubt you could freeze it uniformly and instantly. If it doesn't freeze uniformly, you'd get ripples, steps and other defects in the surface.
They do that for some telescopes. You have a large furnace with a pool of molten glass and you spin it while slowly cooling it down. This is called spin casting.
@@GordonWrigley Fascinating. Did not think that could be done. But perhaps that's just for the rough initial shape? I guess they still have to grind and polish to get an optically useful surface?
this was a question in my book pathfinder.
In the Dune books they often refer to "oil lenses" in telescopes, I feel I finally understand what that was about
1:30 : g isn't the gravitational constant, it's the gravitation. G is the gravitational constant
If liquid metal mirrors only work pointing straight up, I hope we don't waste building them longitudinaly, and put as many as we can latitudinally.
if only you could freeze out all the angular momentum and just have a solid to mold other mirrors with
SUPER COOL. Seems obvious after you see it, but never thought of it.
Can you cool the gallium while spinning and keep the shape? Then maybe polish it.
Could be used as a self healing lens. Could help against cracks.
This reminds me of the movie 'A Bug's Life'
Put the project in a sandbox to remove vibration.
The explanation of the need for parbolas would have probably been better by mentioning the concept of spherical abberation, not chromatic. Still a very nice demonstration of the concept though. Like the recent content.
Why don't they spin some type of binary liquid that hardens over time, then let it harden while spinning, and then coat it with reflective aluminum?
I thought you were going to cool the gallium until it became solid while having a parabolic shape.
This reminds me of skin walker ranch when they are looking through some telescope and notice a beam of light on the mountain and an invisible object over the area where the beam is shining.
Why not spin molten glass in order to get the parabolic curve, then keep it spinning as it cools so it retains its form?
Dear Action Lab, i have a recurrent idea about a space telescope.
One made of only two slices of a giant mirror with like 200m diameter. The two slices, with an amplitude of like 2-3 degrees, rotate and collect the light for differente places in different moments. A software will eventually compose the full 360 degrees image.
Having only two slices and not the entire mirror we could build and send it to space easily.
In yuor opinion would this solution simulate the entire mirror?
Hi can you make 1 video about flames....
-different colors
-Which flames are the hottest
-which burns longer
Etc.
Cool video! I learned something new today, thank you.
I remember reading somewhere that a system like this is used to extend the range of lasers
Couldnt you just wait for the gallium to solidify?
Is gallium or mercury affected by magnetic fields? Could you substitute gravity with a big electromagnet?
That's exactly what I thought too. Unfortunately those two metals are not magnetic. Maybe some special ferromagnetic liquid (with high reflectivity) will do the job, cause ordinary ones are black. They can reflect too, but not much.
So... Could you freeze the gallium or other liquid metal with liquid Nitrogen. To hold the shape.
ITT: "Has anyone ever thought about spinning it up and then let it cool?"
Good idea, Good innovation !!!
Robert Williams Wood did it about 90 years ago. I read about it in school. (Google Translation from Russian )
Couldn't you let the liquid freeze while turning and have a mirror that is solid so you can point it to wherever?
You need to remove the Established Titles ads from your old videos, or make an announcement that that ad was a scam.
It's ok to admit you were scammed, too.
You can take their money and get out of the contract, because they lied.
Idea;
Is it possible to mix gallium with another liquid to separate it, like oil and water, and placed inside a rotating drum to angle the telescope?
If the liquid is inside a sealed clear container with no air and placed on a roller to rotate ut at a fast speed, will it work?
Its not warped because of bubbles. Its warped because your motor and the plate is wobbling and the bowl is not uniform or centered correctly. Has nothing to do with bubbles.
Just freeze the gallium and you can rotate the mirror
min 03:28 :You say that you calculate the focus with the formula f=g/2w² , and you call g "gravitational constant". It's a mistake: that letter "g" is the "acceleration of gravity in the Earth (9.81 m/s²), no the "gravitational constant" (6.67·10-11 Nm²/kg²)
Surface tension breaks this concept
Nice video! Maybe by spinning the liquid on two different axes one could point the telescope at different angles instead of straight up.
Ah yes, thank goodness I have a large supply of gallium
I see Archimedes throwing a large pot full of mercury, using the sun.
distortion driven by gravity field uniformity (spherical source approximating point source) and atmospheric resistance? thanks for the video. spinning fluid lenses are so neat.
I guess if u cool it at the exact speed of your focal length homogenously meaning with the exact flow of heat necessary, u can stop spinning it and rotate it as u like.
Wanna try cooling the galium while spining to see if you can extract a solid mirror?
How does it work when the mirror's inclined to follow objects in the sky? Wouldn't this effect only work properly when the mirror is perfectly horizontal?
Does the liquid mirror necessarily have to always point vertically up? Can centrifugal forces help here? I have seen stunt bike riders drive around in circles on a nearly vertical wall. Also, how about space based telescopes that are free from gravity?
can you not let the gallium solidify and then have a solid mirror that you can use at any angle?
Bro could have even used vacuum chamber to remove bubbles from gallium (if he remembered his favourite tool)
What if instead of mercury or gallium you spin epoxy resin and and keep it spinning until it cures? Once cured, you can then coat it with reflective material and have a cheap mirror.
You said it is limited to looking straight up at 0 degrees, could you not correct for this by having a movable flat mirror or mirrors adjust it to other degrees? Granted it would restrict your field of view but it should be easy to do.
why not create a rough version out of clay or something .. then super heat metal like gold or silver spin it up into the shape u want and let it cool and solidify .. then u just need to lightly polish it and remove it out of the clay and place it in ur rig
I thought he was going to slowly reduce the temp of the gallium to get it to freeze in a parabola shape.
Why can't they use the same technique, but simply freeze the mirror in place. Or better again - use it with a preheated material and let it cool down while rotating, this way you could get away with much less sanding of the mirror.
This video inadvertently debunks flat Earth theory.
is it hard to make a perfectly flat mirror as well? Because you can use one of those to redirect the light towards the horizontal mirror, no?
Gad, what a genius! im in awe,
The length of this video: *NICE*
What would happen if you got the shape you wanted and then lowered the temperature to solidify the liquid?
What if, while spinning, you cool the galium. Would it keep its shape or would it distort?
and when you can mix a mirrored epoxy and spin it until its set then "voila"!
Can't they try to make it similar to the epoxy resin and let it harden while rotating and get a nice mirror for cheap ? If you can't harden gallium, a mirror from resin can be coated with reflected material later on.
awesome! very excited!
If you cool the gallium while it's spinning, will it freeze into a parabolic mirror?
Could they create a reflective ferrofluid held in place by a magnetic field but still be able to be rotated
Man, cant wait to use my large quantity of gallium i just have lying around to make a telescope
can you spin molten steel and then wait for it to harden?