Why Do Spinning Liquids Make Great Telescopes?

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.

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

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.

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.

The amount of knowledge humanity already possesses about the cosmos is both humbling and awe inspiring

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.

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! 🤓

Another advantage is that any dust would go to the edge of the spinning mirror due to the radial force :)

Your explanations are superb!!

Thanks for your channel! Seriously, you made my day!

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.

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.

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.

I really amaze how he come so interesting topics most of us naver heard before so frequently and explain amazingly

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?

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.

Hello! I love you and I've watched all you videos, and this one was at least top 5. Great stuff!!!!

I really enjoy listening to your awareness of things that are old.