Phil Metzger Profile picture
Dec 3, 2017 15 tweets 4 min read Read on X
Another story on forgotten requirements in the space program. During NASA’s Constellation program, we all knew the Apollo Lunar Modules had a requirement that they couldn’t land on terrain more sloped than 11 degrees. (Or was it 10.5? I’m no longer sure.) But nobody knew why. 1/n
2/n Even the lead designer for the Altair lunar lander told me that he didn’t know why Apollo Lunar Landers had that requirement, although he knew that it was in fact their requirement. It was another requirement whose rationale was long lost in the mists of time.

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More from @DrPhiltill

Jun 15
The thing is, at such an early time in human (pre-)history, they did not have standardized number systems. This led to the very long ages of kings that we see in the Sumerian King List. A few details on how this happened… 🧵/1
2/Today, most cultures in the world use base-10, and we use it for every digit in a number. The first digit is ones. The second is 10s. The third is 10x10s. The fourth is 10x10x10s, and so on.

In early Mesopotamian number systems, they did not use the same base for each digit. This example uses ones, then sixes, then 10x6s, then 3x10x6s.Image
3/ Making it more confusing, they had a different number system for each type of thing they were counting. So they had one system for counting people, another for counting sheep, another for counting bushels of barley, another for counting years, etc. The concept of “numbers” had not been generalized as an abstract concept. Numbers existed only as “numbers of sheep” or “numbers of bushels”. It is analogous to the English system of liquid measures, where the number of teaspoons, tablespoons, cups, gallons, etc., is a different count in each higher measure.
Read 14 tweets
Jun 12
I ran into an interesting story, and since I have much time on this cruise I will write it as a thread.

Teaser: The US owes its ownership of Alaska to one of “the Eight Beauties of Ancient China,” the concubine Chen Yuanyuan from the 1600s.

Here is the tale…
🧵 /1

shine.cn/feature/art-cu…Image
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2/ The first part of this story was likely embellished during the Qing dynasty but it is based in truth. When the Ming dynasty fell in the 1640s, a ruthless general of the peasant rebels, Liu Zongmin, took the concubine Chen Yuanyuan hostage and treated her abusively. Her lover (or husband), Ming general Wu Sangui, was of course humiliated and enraged!

Well, Wu Sangui was the general defending the Shanhai Pass at the eastern end of the Great Wall, responsible for keeping out the barbarian Manchu.Image
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3/ Rather than stay loyal to the failing Ming or join with the ascendant Chinese peasant rebels, Wu Sangui was driven to seek swift retribution against those who abused his beloved concubine. He made a personal pact with the Manchus and let them through the wall. They swiftly conquered Beijing during its time of chaos and established the long-lasting Qing dynasty.

Sui Tang Yanyi (a later Qing-era novel) probably exaggerated Chen Yuanyuan’s role in this, saying that “the empire fell for her beauty.” Nevertheless, she became legendary for causing the downfall of the Ming and the establishment of the Qing. But how does this relate to Alaska?Image
Read 12 tweets
May 18
1/ Let’s walk through a mining competition cycle. The students take their robots to the judge station for inspection and weigh-in. (More points awarded for lower-mass robots.) Image
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2/ They set their robots on the forklift platform to lift into the arena. Image
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3/ Robots are placed on the regolith in an orientation chosen randomly by the judges (so the robotic autonomy can’t be cheated).
Read 12 tweets
May 17
@bobster190 @DJSnM @WilliamShatner The paper has all the citations to other work inside it. I linked the paper because it wouldn’t make sense to duplicate that in a tweet. The paper wasn’t about Pluto. It was only about asteroids. We wrote a second paper that discusses Pluto and I think answers your objections. /1
@bobster190 @DJSnM @WilliamShatner 2/ That 2nd paper is here (no paywall so it is accessible):

It does discuss the arguments surrounding the IAU’s vote in 2006. I think we did a much better and more complete review of the issues than any other publication on the topic. Most other papers…sciencedirect.com/science/articl…
@bobster190 @DJSnM @WilliamShatner 3/ …include patently false information about why Pluto was voted down by the IAU. For example, the claim that asteroids were demoted because they share orbits is utterly nonsensical. Even a cursory review of the publication history shows this. Also the claim that the Moon…
Read 16 tweets
May 6
Here is something that hints strongly at how human scientists and engineers are already doomed by AI. 🧵

I noticed this tonight while using Grok for technical research. I asked it a complex question and Grok understood it completely and gave a sophisticated and highly believable answer, but when I asked for specific references so I can write it into a paper for a journal, none of the references Grok provided exactly support the answer it gave me. Instead, they hint at something deeper.

In this case, I am quantifying the loss of signal margin in a Moon-Earth communications link as a function of how many times you landed near the communication system so the rocket plume sandblasted the electronics' thermal coatings, causing them to operate hotter than designed. There is a real cost to sandblasting your hardware on the Moon, and I am trying to quantify it.

Grok gave me many quantified effects, including that the frequency oscillator will drift about 10 to 50 ppm per deg C of temperature rise outside its operating range and that the Signal to Noise Ratio of the overall communications link will drop about ~0.1–0.5 dB for small drifts (<10 kHz) in particular modulation schemes. This is a great result that I can use to quantify sandblasting damage on the Moon, and the result is totally plausible, but it doesn't appear in ANY reference that Grok provided. Nothing discusses this.

So I suspect Grok actually derived that relationship itself during the LLM training. I think the relationship is probably correct, because the many references hint around the edges of this relationship in the right magnitude. I think Grok noticed the patterns of many performance metrics including temperature, input power and frequency, outputs, etc., for many devices and how they are connected in typical systems, and it stored as a higher-level symbol the result that you get 10 to 50 ppm per deg C performance loss. I think it solved that during training as it sought the higher-order symbols to store everything it had learned. IOW, its learning process included a heckuva lot of valid inference on these technical issues, and it now knows more about the performance of communications equipment than even the published literature knows.

I asked Grok if this is true, and it says it is correct (screenshots).

/1Image
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2/ I then asked Grok to derive this relationship the same way it probably did during the LLM training, and it did. So now, if I want to use this key result in my paper, I have to use the many references that Grok used when it derived the relationship, and I have to show the derivation explicitly in the paper, or I can't publish it per the rules of scientific publishing (which of course were created in the days before reliable AI, and we still don't have totally reliable AI, but we can see it is coming fast).Image
3/ So here is the derivation, which it says replicates the process it did during its LLM training, which led it to believe in the quantified relationship between frequency shift and signal to noise ratio. I'm including this just to show its character. Image
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Read 4 tweets
Mar 14
I think it’s likely the Outer Space Treaty will be voided within the next few decades as nations will claim (effectively) national territory on the Moon and Mars.

Here’s why I think this…

/1 Image
2/
The OST is part of the International Rules-Based Order that emerged post-WW2. The IRBO was originally multipolar with the US-led NATO and Soviet-led Warsaw Pact. The collapse of the latter left the US as the main power wanting to keep the IRBO. China/the CCP hates this.
theguardian.com/world/2023/oct…Image
3/ The CCP claims the rules-based order was set up when China was weak so it is unfair and needs to be replaced. They are aggressive at claiming territory in their national interest, disregarding the existing rules-based order by rejecting rulings of the international court. lowyinstitute.org/the-interprete…
Read 10 tweets

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