Thursday, September 16, 2021

SpaceX Inspiration4 Launch Replay

This is a complete replay of the Inspiration4 orbital flight preparations and launch, four hours and forty minutes in length, covering the flight through orbital insertion and separation from the booster's second stage. If you want to start at the launch, skip forward to the 4:16:26 point, one minute before liftoff.

Here is Scott Manley's preview of the mission.

Posted at 13:07 Permalink

Impact Observed on Jupiter

The impact occurred during a transit of Jupiter's moon Io (visible to the left of Jupiter in the photo above, along with its shadow on Jupiter's clouds), a photogenic event which a number of amateur astronomers were imaging at the time.

Posted at 11:06 Permalink

Wednesday, September 15, 2021

What Can You Get for £0.12 in Today’s Britain?

Posted at 12:17 Permalink

Tuesday, September 14, 2021

SpaceX Starlink Group 2-1 Mission

I have cued the video to start one minute before launch: scroll back if you wish to watch from earlier in the countdown. This was the tenth successful launch and landing for Falcon 9 first stage booster B1049, the oldest booster currently in service, having made its first flight on 2018-09-10. This booster joins B1051, which achieved the milestone of ten flights on 2021-05-09, meeting the original design goal of ten flights per booster. Elon Musk has said that SpaceX will continue to inspect and re-fly boosters, building experience in long-term re-use. I suspect that “fleet leaders” with the greatest number of flights will be reserved for in-house Starlink missions, where a loss due to unanticipated aging issues would not impact an external customer.

Posted at 10:32 Permalink

Monday, September 13, 2021

From Egg to Monarch Butterfly

Here is the pupation process in real time,

And this is emergence of the mature butterfly from the pupa.

At the end of this process, the wings are soft and will take a couple of hours to harden before taking flight.

Posted at 12:58 Permalink

What Really Happened to the Arecibo Telescope?

Posted at 10:35 Permalink

Sunday, September 12, 2021

IBM Patent Application for “Telum” Mainframe CPU Cache

The unusual “cache virtual memory” architecture of the next generation “Telum” processors for IBM's Z-Series mainframes was discussed here on 2021-09-03. IBM have filed a U.S. patent application, US 2021/0026783 A1 [PDF], on 2021-01-28 which describes the “black magic” behind how it maintains consistency and low latency with multiple levels of processors sharing cache and “borrowing” storage from one another.

Are my eyes deceiving me, or is the text in Figures 7, 11, and 12 actually Comic Sans?

Posted at 11:48 Permalink

Saturday, September 11, 2021

Narrowing the Search for Planet Nine


The existence of a giant planet beyond Neptune — referred to as Planet Nine (P9) — has been inferred from the clustering of longitude of perihelion and pole position of distant eccentric Kuiper belt objects (KBOs). After updating calculations of observational biases, we find that the clustering remains significant at the 99.6% confidence level. We thus use these observations to determine orbital elements of P9. A suite of numerical simulations shows that the orbital distribution of the distant KBOs is strongly influenced by the mass and orbital elements of P9 and thus can be used to infer these parameters. Combining the biases with these numerical simulations, we calculate likelihood values for discrete set of P9 parameters, which we then use as input into a Gaussian Process emulator that allows a likelihood computation for arbitrary values of all parameters. We use this emulator in a Markov Chain Monte Carlo analysis to estimate parameters of P9. We find a P9 mass of 6.2[+2.2−1.3] Earth masses, semimajor axis of 380[+140−80] AU, inclination of 16±5∘ and perihelion of 300[+85−60] AU. Using samples of the orbital elements and estimates of the radius and albedo of such a planet, we calculate the probability distribution function of the on-sky position of Planet Nine and of its brightness. For many reasonable assumptions, Planet Nine is closer and brighter than initially expected, though the probability distribution includes a long tail to larger distances, and uncertainties in the radius and albedo of Planet Nine could yield fainter objects.

Posted at 12:54 Permalink

Thursday, September 9, 2021

Were the Boskops, Prehistoric Hominids, More Intelligent Than Modern Humans?

And if they were, and evolution selects for intelligence, what happened to them? Maybe they invented socialism, let technological development stagnate and be regulated out of existence, then ceased to breed when the cost of forming families and raising children became too high for the young.

Posted at 12:47 Permalink

Wednesday, September 8, 2021

Why Cranes Collapse

Posted at 11:40 Permalink

Tuesday, September 7, 2021

Cutting a Torus with Three Planes

Posted at 10:29 Permalink

Monday, September 6, 2021

Simulating Biological Neurons with Artificial Neural Networks

Posted at 12:03 Permalink

Sunday, September 5, 2021

Single Event Upsets—Computer Crashes from Deep Space

Note that while error correction code (ECC) memory can dramatically reduce the vulnerability of computer systems to errors induced by cosmic rays or other exogenous sources (memory arrays are very dense and have few electrons per storage cell, and thus present both a large and soft target), the logic circuits within processors and other electronics remain at risk and, except for special-purpose and very expensive “radiation hardened” or multiple redundant hardware designed for aerospace applications, are not protected against upsets.

Single event upsets due to cosmic rays do not damage electronics: they just cause transient errors where the computer does something it isn't supposed to. This makes it extremely difficult to diagnose the source of the problem, and when something apparently inexplicable happens due to poorly designed and incompetently implemented software (for example, that intermittently operating system famed for its “blue screen of death”), its sloppy perpetrators sometimes blame it instead on “a cosmic ray”. It does happen, but usually it's crappy code.

Posted at 12:45 Permalink

Saturday, September 4, 2021

Why Are Scorpions Fluorescent?

Posted at 11:17 Permalink

Friday, September 3, 2021

Ridges on Coins, Neutron Star Collisions, and Isaac Newton

Posted at 12:28 Permalink

Thursday, September 2, 2021

Universal Equation for the Shape of Birds' Eggs

The paper, “Egg and math: introducing a universal formula for egg shape”, is behind a paywall, with the Wiley journal charging US$ 16 to look at it online for 48 hours up to US$ 49 to download a PDF. Nobody seems to have uploaded it so far to SciHub, so we'll have to wait until some public-spirited roadrunner with institutional access liberates it. There is, however “supplementary material” for the paper, in gnarly Microsoft Word format, which can be downloaded from the abstract page and opens in LibreOffice. This document provides sufficient information to figure out what they're doing and how to apply the model, although you'll have engage in a bit of reverse engineering.

Posted at 14:54 Permalink

Wednesday, September 1, 2021

Using Galactic Supernovæ as SETI Signal Beacons

The research paper is “Search for Galactic Civilizations Using Historical Supernovae”.


We study an interstellar signaling scheme which was originally proposed by Seto (2019) and efficiently links intentional transmitters to ETI searchers through a conspicuous astronomical burst, without prior communication. Based on the geometrical and game theoretic viewpoints, the scheme can be refined so that intentional signals can be sent and received after observing a reference burst, in contrast to the original proposal (before observing a burst). Given this inverted temporal structure, Galactic supernovae recorded in the past 2000 years can be regarded as interesting guideposts for an ETI search. While the best use period of SN 393 has presumably passed ∼100 years ago, some of the historical supernovae might allow us to compactify the ETI survey regions down to less than one percent of 4π, around two rings in the sky.

Posted at 13:52 Permalink

Tuesday, August 31, 2021

World's Shortest Scheduled Airline Flight

Ninety-one seconds from takeoff to touchdown. It's faster on days there's a tailwind.

Posted at 13:11 Permalink

L. Neil Smith, 1946–2021, R.I.P.


L. Neil Smith, libertarian, prolific author of science fiction and political and cultural commentary, founder of the Libertarian Enterprise, presidential nominee of the Libertarian Party of Arizona in 2000, died on August 27th, 2021.

L. Neil's work introduced generations of readers, including myself, to the promise of liberty, not as dry theory, but by following the science fiction maxim of “show, don't tell”, brilliantly illustrating genuinely free people and societies, and demonstrating how, by exercising their freedom and its inherent advantages in creativity, initiative, wealth generation, and adaptability, they can defeat the creeping grey poison of collectivism and have a tremendous amount of fun in the process.

Here is science fiction and fantasy author (and frequent contributor to the Libertarian Enterprise) Sarah Hoyt saying “Goodbye, My Friend”. Mike Glyer has posted a brief biography on File 770. The family has set up a memorial Web site where you can leave memories of Neil and his work and contribute to causes he supported.

I'm going to remember L. Neil by re-reading the two books that introduced me to his work and forever cured me of being what he dubbed a “nerf libertarian”, The Probability Broach (also available as a graphic novel) and The Venus Belt. If you've yet to discover his work, they're a fine place to start.

Here are reviews of works of L. Neil Smith that I've posted over the years.

Farewell, L. Neil, and thank you for the enjoyment, encouragement, intellectual stimulation and challenge, and all the laughs over these many years.

Posted at 11:03 Permalink

Monday, August 30, 2021

Google AI—“ High Fidelity Image Generation Using Diffusion Models”

Posted at 12:39 Permalink