Category Archives: science


I went (via Zoom) to a great lecture last night. Serafina Nance spoke to the The Calgary Centre of the Royal Astronomical Society of Canada on Tracing the Lives, Deaths, and Explosions of Massive Stars.

Supernovae are cosmic events of gigantic power. Their explosions can shine as bright as a galaxy, a pinprick of extraordinarily bright light in the night sky. What is less well-understood, however, is which stars reach the point of explosion and how they evolve to their deaths. Interestingly, their explosions provide astronomers with key tools to uncover fundamental aspects of our Universe. While we know that the Universe is expanding at an accelerated rate due to dark energy, the rate of the expansion of the Universe is not well-constrained. Supernovae provide us with independent ways to measure this expansion and work to resolve one of the most pivotal questions in astronomy: How fast is the Universe really expanding?
Continue reading

Significant Figures

I found this post on Facebook: Why is it important to know so many digits of pi?.

My comment:

As someone who started computing with log tables and slide rules, the first question I ask is how many significant digits do the other variables in your calculation have? The smallest such number tells you how many digits of pi you need. With electronic devices there is no harm in using more in your calculation, as many as your device has, but do not let that give you a false idea of the precision of your result.

I learned about significant figures in my high school chemistry in 1967-68. (Thank you, Mr. Wheeler!). Use of appropriate significant figures, also from a chemistry class, clearly explains the concept and its use in practice.

I only first saw Star Trek (TOS) after high school, in reruns. Thanks to that chemistry class I gag every time I hear Mr. Spock reporting some calculation to an absurd number of decimal places. His input data could not possibly be that precise!

Water on the Moon

It’s confirmed. There is water on the Moon. OK, what’s the big deal? Water is very common in the cosmos and has been seen on the moon before. The difference is that previously it had been been only in craters near the lunar south pole, perpetually in darkness. Now, as the updated NASA announcement said, NASA’s SOFIA Discovers Water on Sunlit Surface of Moon, which will be much more accessible to future explorers.

How significant this is remains to be seen, but it has provided Katie Mack with some inspiration.

Phosphine on Venus: Not so fast

Last month I posted about a Possible Sign of Life on Venus, which reported on Phosphine gas in the cloud decks of Venus. Earlier this month I mentioned More about phosphine on Venus. The story is not over yet.

A Question of Phosphine links to Re-analysis of the 267-GHz ALMA observations of Venus: No statistically significant detection of phosphine. This team re-analyzed the same data used in the first Phosphine gas paper, but came to the opposite conclusion. So it comes down to a very complicated question of statistical analysis.

Professor Coles also linked to A stringent upper limit of the PH3 abundance at the cloud top of Venus by another team which included Jane Greaves, first author of Phosphine gas in the cloud decks of Venus.

American Poison Gas in World War II



Evidence for Literacy in Ancient Judah

The Babylonians sacked Jerusalem and conquered the biblical kingdom of Judah in 587 BCE. Just before then, c. 600 BCE, Judah maintained a small military outpost at Tel Arad, about 20 miles south of Jerusalem. Written inscriptions have been found there on ostraca (pottery fragments), a common writing medium in the ancient world. The fort at Tel Arad was a small place, with a garrison of 20-30 soldiers. Yet a handwriting analysis of 18 incriptions shows that there were least 6 and perhaps as many as 12 authors of these texts. This indicates that literacy was not uncommon in Judah at the time, at least among the army. It was not the exclusive domain a few scribes serving the king.

Given a substantial degree of literacy, it is plausible that some of the books of the Hebrew Bible, e.g. Deuteronomy, Joshua, Judges, Samuel, and Kings, were in fact written down before the fall of Jerusalem and the Babylonian exile.


More about phosphine on Venus

Following up on Possible Sign of Life on Venus. After that announcement some scientists took another look at 1978 data from the Pioneer Venus Multiprobe. At the time nobody was specifically looking for phosphine, but a new analysis of the raw data supports the possibility that there is phospine in the atmosphere of Venus. Details at Is Phosphine in the Mass Spectra from Venus’ Clouds?.

This has happened before in astronomy. After both Neptune and Pluto were discovered, astronomers looked at old records and found that their predecessors had seen both bodies, but had not realized they were significant. In the case of Neptune one of those predecessors was Galileo.

Possible Sign of Life on Venus

Yesterday I got an email from Cosmoquest about a science press conference (“presser”) where a new discovery would be announced. With all the new distance-based communication technology anybody could watch, rather than just those in a select room, however large. The event was put on by the Royal Astronomical Society today. I watched it on the Cosmoquest Twitch TV channel. I had never heard of Twitch TV before.

The occasion was that

An international team of astronomers, led by Professor Jane Greaves of Cardiff University, today announced the discovery of a rare molecule – phosphine – in the clouds of Venus. On Earth, this gas is only made industrially, or by microbes that thrive in oxygen-free environments.

The discovery was made by spectroscopy using two different radio telescopes. The significance of this is that the production of phospine by purely chemical processes is very unlikely in the atmosphere of Venus. The team looked at every possible chemical reaction they could think up, and failed to find any that could come close to producing the observed amount of phospine.

Continue reading

Searching for Extraterrestrial AI

Looking for E.T.? Try His Artificial Intelligence Instead, Astronomer Says

The suggestion that artificial ET’s might more evident than biological ones is not new. Frank Tipler (before he went off the deep end) suggested in 1981 that alien civilizations might use von Neumann probes to explore a galaxy. He concluded that since we do not see such probes,
there are no ET’s in our galaxy. In science fiction the concept goes back at least to 1963, when Fred Saberhagen’s first Berserker story appeared.

Actually, almost all suggestion for SETI come down to Searches for ExtraTerrestial Technology. It will be a long time before we can find any other sign of intelligence out there.

Bok globules are another search target for sentient machines. These dense regions of dust and gas are notorious for producing multiple-star systems. At around negative 441 degrees Fahrenheit, they are about 160 degrees F colder than most of interstellar space. [Is this correct?-GTM]

This climate could be a major draw because thermodynamics implies that machinery will be more efficient in cool regions that can function as a large “heat sink”. A Bok globule’s super-cooled environment might represent the Goldilocks Zone for the machines, says Shostak.

The idea that Bok Globules might be linked to ET’s was anticipated by Fred Hoyle in his 1957 novel The Black Cloud. Early in the book some astronomers are looking at some images of the cloud (which turns out to be an intelligent and powerful life form). One of them describes it as “a fine example of a Bok globule.”

Solar Flares and Radioactive Decay

From Stanford University News and Symmetry Magazine (The latter has a small but important correction—See the 1st comment and the response)


Is this possible?

Researchers from Stanford and Purdue universities believe it is. But their explanation of how it happens opens the door to yet another mystery.

Also discussed by Jeff Duntemann.

The article mentioned the decays Silicon-32 and Radium-226, as reported in Evidence for Correlations Between Nuclear Decay Rates and Earth-Sun Distance back in 2008. Similarly, Perturbation of Nuclear Decay Rates During the Solar Flare of 13 December 2006 indicated a solar dependence on the decay of Manganese-54. The suggestion that radioactive decay rates might in some way depend on the sun is quite extraordinary, and has prompted the reanalysis of a lot of data. Evidence against correlations between nuclear decay rates and Earth-Sun distance looked at the decay of 6 other radioisotopes without seeing any such dependence. There is no obvious dependence on atomic weight or other systematic difference between the elements.

There are different types of radioactive decay. Radium-226 decays by emitting an α particle (a Helium nucleus: 2 protons and 2 neutrons) while Silicon-32 is a case of β decay (emission of an electron). Manganese-54 decays by electron capture, which is essentially time-reversed β decay. α-decay is a manifestation of the of the strong nuclear force, while β-decay is a weak interaction. If the solar effect is real, then affects two differenct fundamental forces of nature.

John G. Cramer, in Radioactive Decay and the Earth-Sun Distance suggested that

…the Earth’s orbit has a very small eccentricity, so the annual variations in R [the Earth-Sun distance] are small. A better way of testing whether radioactive decay rates depend directly on 1/R2 would be to monitor a radioactive decay process within a space vehicle in a long elliptic orbit with a large eccentricity, so that R has a very large variation. As it happens, NASA has a number of space probes that match this description, because many space probes, particularly those that venture into the outer reaches of the Solar System, are powered by radioisotope-driven thermoelectric power sources containing a strong radioactive decay source that produces enough energy as heat to power the vehicle. The power levels of such thermoelectric generators are carefully monitored because they constitute the principal power source of the vehicle.

This has been done. According to Peter Cooper, in Searching for modifications to the exponential radioactive decay law with the Cassini spacecraft

Data from the power output of the radioisotope thermoelectric generators aboard the Cassini spacecraft are used to test the conjecture that small deviations observed in terrestrial measurements of the exponential radioactive decay law are correlated with the Earth-Sun distance. No significant deviations from exponential decay are observed over a range of 0.7 – 1.6 A.U. A 90% Cl upper limit of 0.84 x 10-4 is set on a term in the decay rate of Pu-238 proportional to 1/R2 and 0.99 x 10-4 for a term proportional to 1/R.

Less technically:

Deep-space probes usually generate power from the heat emitted by a chunk of radioactive material-plutonium-238 for the Cassini spacecraft. Cassini journeyed as close to the sun as Venus and then far back to Saturn, spanning a much wider range of distances from the sun than Earth does during its yearly orbit. If the sun had an effect on plutonium decay, the fluctuations would have been much more substantial than those seen in Earth-bound experiments. As a result, Cooper reasoned, Cassini should have measured substantial changes in its generator’s output. It didn’t.

The Stanford/Symmetry article included something new. Peter Sturrock, Professor Emeritus of Applied Physics at Stanford, suggested is that some of the variation in the Radium-226 and Silicon-32 decay rates is related to solar rotation. From Evidence for Solar Influences on Nuclear Decay Rates

Recent reports of periodic fluctuations in nuclear decay data of certain isotopes have led to the suggestion that nuclear decay rates are being influenced by the Sun, perhaps via neutrinos. Here we present evidence for the existence of an additional periodicity that appears to be related to the Rieger periodicity well known in solar physics.

Links to the research reports can be found at Variability of Nuclear Decay rates. Search for “Research papers: PERIODIC VARIATIONS: SCALE OF DAYS OR YEARS” and “Research papers: NON-PERIODIC VARIATIONS:” Subheading “Of Cosmic Origin”. Thanks to information about current research in physics is easily accessible.

Peter Sturrock was my first course advisor when I was a graduate student in his department at Stanford, 1972-1975. At one point there I wanted to take a course in mathematical statistics. I was a little hesitant about this, since the subject is somewhat off the main direction of graduate study in physics. To my surprise, Professor Sturrock strongly encouraged me to do so. Whatever the conclusion about the relationship between the sun and radioactive decay may be, there will be a lot of statistical analysis along the way.