
Planetary geophysicist who understands the gravity of a situation. Trying to follow Jesus. Associate prof @BaylorGeo, formerly @eapsMIT/@LamontEarth/@LPItoday
Waco, TX
Joined June 2009
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Peter James retweeted
This is the least surprising graph in the world if you understand how gradient descent works.
There’s a subculture of people striving for “Financial Independence / Retire Early” (FIRE). Some people yearn for freedom from their job so much that they would trade it for literal incarceration.
Peter James retweeted
NASA has selected three new science investigations through its PRISM program to prepare for humanity’s first lunar outpost, @NASAMoonBase.
From monitoring hazards to finding natural shelters and mapping water ice, take a look at the science paving the way for lunar exploration: go.nasa.gov/4iS0h7k

ALT A view of the Moon from space, showing its crater‑covered surface in deep shadow along the lower half and illuminated along the top. Just above the lunar horizon, a thin blue crescent of Earth rises against the blackness of space, creating a striking contrast between the gray, textured Moon and the glowing curve of Earth.
I told my wife (materials engineer) this was a SEM image. Her first comment was "I don't see a scale bar..."
Scale bars and axis labels matter.
science.nasa.gov/photojourna…
Peter James retweeted
Some thoughts on the Navier-Stokes news from a professor of aerospace engineering:
1) take a deep breath
2) posts indicating we "solved Navier-Stokes" are incorrect and overblown. A very specific mathematical proof involving a niche scenario for Navier-Stokes has *potentially* been shown (that a perfectly smooth incompressible initial condition with finite energy could produce a singularity--note the assumptions here piled on to an equation set that already involves some assumptions).
3) there is no general closed form solution for N-S and that's not what this news is about
4) this is more of a mathematical curiosity than anything else and could matter a lot to mathematicians but basically changes nothing in the way N-S are used in practice
5) there are already very useful exact solutions to Navier-Stokes that greatly simplify the equation set with the right boundary conditions/geometry like laminar flow through a pipe or a 2D Taylor-Green vortex
6) in aerospace, we already treat N-S as an approximation in many instances and are well aware of its limitations. we don't outright solve these equations anyway and regularly chop off terms or simplify parts (at the expense of accuracy) to make them easier to deal with.
7) to be honest I have never found this specific problem to be particularly interesting because we know a core assumption of N-S is a "continuum" fluid where you ignore molecules and assume hydrodynamic scales >>> molecular scales. We know a real fluid cannot have infinite velocity or energy. But clearly you can push equations outside of their bound of validity and make them produce funky results and singularities.
One thing about modern kid life is that there are animal trends. A few years ago, owls were everywhere in school: in books, in school handouts, and in cartoons. Then it was llamas. This year, the trendy animals are axolotls.
The technique of using gravity anomalies to calculate the density of a mountain was developed a century ago by L.L. Nettleton.
The first page of his 1940 book states that 10-15 years of oil reserves remain. I guess the lesson is to be humble about projecting into the future.
Peter James retweeted
Kind of wild that NASA has never operated a robotic rover on the surface of the Moon.
The funeral service for my department chair was lovely in the way that comes from the deceased loving Jesus and having tight-knit children and grandchildren.
His son noted “He gave the world what it needed: laughter, love, and a reason to get a good cup of coffee.” I love that.
The new crater formed by the Falcon 9 upper stage, via the Lunar Reconnaissance Orbiter narrow-angle camera
Fleming’s Lessons on the Globes (published 1844) ends with a section on “Uranography”.
Uranus is the Ancient Greek word for “heaven”, so uranography was a 19th century word for what we now call astronomy.
Crazy idea: if we could measure density with high enough precision, could you infer the gravitational constant? We know GM very well.
Experiments to measure G differ by about 0.5%, so you would need an uncertainty of <25 kg/m3 in the density measurements of the Earth.
🔔📜 IceCube paper submitted to PRD!
We predict that statistically significant data from the Upgrade will rule out a uniform Earth density profile in favor of the standard layered-density profile.
Story ➡️ icecube.wisc.edu/news/resear…
Peter James retweeted
Our team at @iaa_csic has captured the impact on the Moon of the upper stage of a Falcon 9 rocket. We attach a preliminary video showing the evolution of the ejected material. The black area corresponds to the lunar disk @SpaceX @JuanLuisRizos @elonmusk @tiempobrasero @A3Noticias @EFEciencia @europapress
When the GRAIL spacecrafts were scheduled to collide with the Moon, the GRAIL PI told us to not bother watching. She was right.
If you can barely see the Great Wall of China from space, why would you expect to see an empty washing machine smack the ground 1000x farther away?


















