This video by AlphaPhoenix is absolutely incredible! I do research in (nonimaging) optics and I am used to thinking about the propagation of light. Still, there is something amazing about seeing a real recording of the propagation of a real beam of light. I also love the fact that you see artefacts due to how long light from different parts of the scene takes to reach the camera
Readit Newshakonjdjohnsen commented on What the speed of light looks like [video] youtube.com/watch?v=o4TdH... · Posted by u/mrtksn
Thermophotovoltaics is really cool. It is an old idea but recently several groups (including the group behind fourth power) have shown much better experimental performance than before, towards the level where this is starting to look like a real solid-state heat engine.
The idea is to use a photovoltaic cell (“solar cell”) to convert thermal radiation to electricity. A regular solar cell has limited efficiency because the sun has a wide spectrum and a single material is not efficient across the whole spectrum. With thermophotovoltaics, the hot surface is so close to the cell that you just reflect the “bad” photons back to the hot surface to recycle them instead of losing their energy.
In theory, a more efficient alternative to a traditional solar cell is to use the sunlight to heat a surface to ultra-high temperatures and then run a thermophotovoltaic cell on that hot surface, but this is easier said than done.
As an outsider I do think it looks like the competitor Antora Energy has a simpler approach: instead of pumping the heat using high-temperature liquid (with lots of moving parts), they just use thermal radiation to transfer the heat inside their battery.
Yep, I suspect this is all marketing fluff and no substance. I see a lot of superlatives but no substantial technical breakthrough here.
I think there is at least some plausible interpretation of this that points to more than marketing fluff.
You want to count particles per volume of air, so conventional sensors use a fan to have a constant volumetric flow and then count particles per second to infer particles per volume.
The way I interpret the above marketing language is that they use the optical sensor not only to count particles but also to measure the particle movement and infer airflow. So as long as there is some natural movement in the air, they can measure both particle count and volumetric flow, and thus infer particles per volume.
hakonjdjohnsen commented on CARA – High precision robot dog using rope aaedmusa.com/projects/car... · Posted by u/hakonjdjohnsen
The linked page has that video embedded.
Yeah good point!
When I came across this amazing project and wanted to share it to HN, I was debating whether to post the youtube link or the project page. I decided to post the project page and mention the youtube link in the description for those who prefer video, but somehow that description got posted as a comment instead (not sure how that happened?). Anyway as you said the video is embedded in the project page so it wasn't really necessary
hakonjdjohnsen commented on CARA – High precision robot dog using rope aaedmusa.com/projects/car... · Posted by u/hakonjdjohnsen
See also the youtube video about the project:
https://youtu.be/8s9TjRz01fo
I found this presentation from the Disobey 2025 conference to be a really good and entertaining watch!
Last year the presenter also wrote a blog post about the attack, which received some discussion at the time:
Cool concept! I do research in solar concentrator optics, so I enjoy seeing such completely different applications of concentrated sunlight. Still, I am not fully convinced in this specific case. I wonder if it is not a lot easier to provide the missing spectrum ourselves instead of running fiber optic bundles from the roof?
If I understand correctly, your two main benefits are broader spectrum and lack of PWM flicker. Did you measure the spectrum of the light from the prototype monitor? The light goes through several filters - first I assume the daylighting system has an IR filter to prevent overheating. Then it goes through the LCD itself, and the color filter array in front. Are you still left with a lot of IR (or the frequencies are considered beneficial) after all this?