Why does collapsing a bubble with a sound wave produce light? | Hacker News Reader

Why does collapsing a bubble with a sound wave produce light?

akshatjiwannotes.blogspot.com

21 pointsakshatjiwan27 comments

Holy hypertext, this is a hard-to-read post.

Internet 5.0, every word is a link. Scrolling is done with your brain, clicking is done with by flexing your nostrils

Sneezes are security risks. Sounds neat

I sometimes wonder what people are thinking (or apparently not thinking) when they link to their personal sites and blogs and it's totally unreadable. I think they are so used to it they don't see any problems with it.

It looks a bit messy to me, neglecting usage of hyperlinks, but at the same time highly legible (does not mess with fonts, colors, or the layout too much), lightweight, works without JS, does not geo-block me or require to solve captchas, not paywalled, not blocked here, is straight to the point. So perhaps still more easily readable than most of the other submissions found on the HN front page.

Apologies. I write everything in plain text on my mobile and just copy paste it to blogger/fb. Most platforms automatically create clickable links (hn also does that) but apparently blogger does not do it.

I like full links on the post because it makes it easier to backup. If I embed them in anchor tags they'd have to be parsed from the formatted web page or I'd have to store data as an html file. I don't want to do that.

md is a good alternative and slowly I'm migrating my files to GitHub.

A lot of work goes into minimizing cavitation in marine systems as it tends to waste energy and cause damage to propellers. That being said, there has been a lot of research lately into using sustained cavitation to purify and distil water. The energy released can be enough to boil water, kill pathogens, and generate free radicals to further sterilize the water.

https://iwaponline.com/wst/article/86/2/302/89569/Hydrodynam...

> 1. How do you extract energy out of it? It's surrounded in a water bath that would evaporate leading to cessation of bubble formation.

Sounds like a perfect use-case for the tried and true steam turbine. You can never beat a steam turbine.

Steam is the medium, not a fuel. Low-temp steam just above the boiling point doesnt carry much energy. It would also be very wet, which plays havoc with mechanical systems. I dont see how this tech could ever produce the hot/dry steam needed for turbines.

Sonoluminescence is not power positive. Fusion would be trivial to prove with a neutron detector- so saying "theres debate" is arguably dishonest.

Sonoluminescence is weird and awesome enough as is: cavitation that produces light.

Researchers have reported neutron detection but these results have not been reproduced and some scientists have attributed this detection to 'noise'. Bubbles are tiny they have very small amount of gas in them so detecting that is not exactly straightforward... I think

for example a in a 1um radius bubble the total mass of gas would be ~ 10^-18kg.

Personally I doubt fusion occurs inside bubbles. Even if we take the highest reported temp 30000K that's way below what's required for fusion.

Also bubble literature is full of fantastic claims—one that comes to mind is assertion that pressures of around 10Gpa can be generated which seems highly improbable because that's likely to induce phase change in the fluid.

However it's quite possible that I'm wrong. Because bubble science keeps on throwing new surprises.

Are you agreeing or disagreeing with it being trivial to check if theres fusion?

> However it's quite possible that I'm wrong. Because bubble science keeps on throwing new surprises.

Ultimately that's my assertion. No need for exaggerated/optimistic claims when something interesting turns up about it on a regular basis.

I'm disagreeing that it's trivial to check for fusion because of low mass of gas inside the bubbles and suggesting that it's unlikely that fusion would ever happen in a bubble because temperatures required for fusion are way higher than bubble cavitation temperatures.

Do you have any ideas on how detection can be made in a bubble radius of say 100um?

In laser fusion experiments the pellet size is in mm range and it's completely filled with solid/liquid hydrogen to achive high particle density.Thats not possible in a bubble.

The thing is even for something as well studied as sonoluminescence there is no scientific consensus. Literature is all over the place when it comes to bubble gas temperature during cavitation.

Lots of arguments and debates are ongoing in the community. I think that's what happened with fusion story.

https://en.wikipedia.org/wiki/Neutron_detection

Wouldn't fusion also mean net energy generation? Or at least much higher than inputs... So there should be lot more energy in system than expected.

Unfortunately, no- while atoms fusing has a fixed mass to energy conversion... getting them close enough that they'll fuse takes a lot of energy. The three hurdles to effective fusion are: 1) getting more energy from fusion than was spent making it happen 2) extracting the extra energy 3) (this never gets covered) avoid neutron flux turning the whole thing into radioactive scrap before it can pay for itself and storage.

National ignition facility (NIF) recently got exited about more energy out than they put in. They don't have a plan for #2 or #3- but as a research facility focusing on #1 thats OK.

Numerous tokamak designs try to handle #1 and #2, but handle #3 by putting rails into the reactor for robots to replace and repair things.

I'm very pessimistic about #3- nothing is immune to neutron damage from fusion, it's just engineering it to fail in a way thats useful. And, once the public accepts the problem, produces less nuclear waste than fission.

Collect it directly at the audio jack and skip the water-bubble-light chain entirely. You won’t get out more than the energy of the sound wave you put in, you’ll get quite a bit less actually.

This was a passion of mine decades ago, but Putterman's lab jump-started interest after the cold fusion debacles. Some fun videos and pictures on the lab website. https://acoustics-research.physics.ucla.edu/sonoluminescence...

I may not be a working professional in the field of physics - I only had a couple of classes in college - but I absolutely love physics! It seems like magic, and when you learn how it works, you feel like a magician. It's awesome!

It certainly is a great hobby. I'm not a physicist either but I keep reading papers and taking courses on YT about areas I'm interested in — Materials science,plasma, Electrostatics,fluids,thermodynamics etc.

Good thing is science doesn't change like tech. Once you learn something it's for life. No need to keep learning new frameworks/tools every year. It's stable and yet immensely flexible.

With AI research and studying has become a lot easier. Give it a try if you're interested.Now is a great time to start.

I suppose it would also produce nitrogen oxides.

Very likely. The hot plasma generated would form oxides when it's cooled. I read a few papers a while back focussed around generating ammonia and other nitrogenous compounds. I can't find the link to the one I read but apparently other researchers are doing something simillar

https://arxiv.org/html/2505.23850v1

In air bubbles NOx would be likely but it would probably lead to nitric acid production after reacting with water. Here's a paper by NASA that pretty much confirms your intuition

https://ntrs.nasa.gov/api/citations/20050215681/downloads/20...

Interesting. Nitric acid could be a chemical signature that could be measured, then. Maybe ozone also? I'm thinking equipment monitoring for cavitation.

Absolutely! Ozone is produced as a byproduct but I don't have any refrences at hand. More generally it can be said reactive oxygen species are produced as an intermediary that turn into several compounds as plasma is cooled.

Whatever gas you make bubbles from is going to be ionised(plasma is created during cavitation) and it's going to produce a cocktail of chemicals inside as it cools below ionisation temperature.

Many of these are shortlived eg oxygen reacts with hydrogen or nitrogen to form more stable compounds but some intermediaries can be stable and be detected.

The absolute max amount of nitric acid you can get for example is proportional to the amount of air dissolved in water. If you cavitate entire 1L of water max HNo3 you can get is about 20mg. Realistically it's not possible to cavitate such a large volume of water at once and there's a competition among reactants to form other products eg oxygen is going to used for hydrogen peroxide as well. Very sensitive instruments are used to detect these.

This is studied in sonochemistry —using bubbles to drive chemical reactions.Not enough for large scale production but small doses of chemicals — mostly radicals can be delivered by bubbles making it useful as a disinfectant.

Is there a better link?

Are Reddit posts allowed to be submitted to HN?

What?

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