Elon Musk says "cooling is actually much easier in space than it is on earth," and a big part of SpaceX's roughly $2 trillion IPO pitch rests on putting AI data centers in orbit. So I went to the blackboard to check whether this holds up. In this video I work through the physics of orbital data centers using nothing more than high school physics: how much solar power you can actually collect in space, where all the heat from the GPUs goes, and why the vacuum of space is a lot more like a thermos than a refrigerator.

We start with the case for space data centers (constant sunlight, no water use, no waiting on the power grid) and some practical problems that don't usually make it into the pitch, like the fact that you can't swap out a failed GPU in orbit. Then we figure out how much solar panel area it takes to run a single AI server rack, a gigawatt data center, and the terawatt of AI compute Musk has talked about launching. After that we get into cooling: why space being "cold" doesn't mean space is good at cooling things, how radiation compares to still air, fans, and water cooling, how big a radiator one rack needs using the Stefan-Boltzmann law, and how that stacks up against the radiators on the International Space Station.

The short version: the physics doesn't make orbital data centers impossible, but it makes them a lot harder and more expensive than the pitch suggests. As a result, I'm very skeptical that this will be possible on the timescale being advertised (claims like space will be cheaper for AI in the next 2-3 years, 1 TW per year launched, etc.).

Missed out on yesterday's full moon, (and probably today too) but still proud of this one from 28th September.

Captured using Nikon D5300, 300mm telephoto lens. 75 shots stacked on Autostakkert, best 72% on final stacking. This image is 100% zoomed and cropped to content, and some final touch in GIMP

This isn't my first attempt but this is the first time I used a decent tri-pod and software to stack and enhance the picture. Would love to capture Moon with a telescope to create the Mineral Moon. Appreciate any advice on how do I go on achieving that.

Link to the available report by ESO: https://www.eso.org/public/videos/potw2643a/

Study: https://iopscience.iop.org/article/10.3847/1538-3881/ae9763

A rocky lava planet once thought to be too extreme to have an atmosphere appears to be wrapped in one with a reflective layer of vaporized silicate mineral clouds, the same family of compounds that make up quartz and sand.

University of Waterloo Physics and Astronomy Professor Lisa Dang and collaborators used the James Webb Space Telescope(JWST) to observe the lava planet TOI-561 b for 37 hours, capturing nearly four complete trips of the planet around its star.

The paper, "A Highly Reflective Atmosphere on the Lava World TOI-561 b Revealed by JWST/NIRSpec Phase Curve," was published in The Astronomical Journal.

"We measured how the planet's brightness and heat changed throughout its orbit," says Dang.

"This technique, known as a phase curve, revealed that the planet reflects a significant amount of light from its star, and that heat is being redistributed around the planet instead of only on the sunlit side. Together, these point to the presence of an atmosphere."