Archive for October, 2022

Oct 13 2022

Another Possible Technosignature Falls

Published by under Astronomy

One day it may turn out that a potential sign of alien technology (technosignature) turns out to be just that. That is the best hope of finding evidence for life outside our solar system in my lifetime. But that day has not yet arrived, and another potential candidate (although this one was pretty weak) has found a natural explanation.

Of course no one knows, because we only have one example of life and a technological civilization, but if I had to guess I would say the universe is teeming with life. We’ve now confirmed what scientists long suspected, that our solar system is not unique or rare. Most stars have lots of planets around them, including rocky worlds within their habitable zone. Also, life seems to have arisen very quickly on Earth, as soon as the conditions were compatible with organic life. We may also find that life once existed on Mars, and may still exist in one or more ocean world, like Europa. Discovering even microbial life that originated independently from life on Earth would be huge – it would give us a second data point. It would confirm that life is likely everywhere it can form.

The probability, and therefore density, of technological civilizations is another matter entirely. It took the Earth about 4 billion years of tinkering with life before a technological species arose, and it happened (so far) only once. We have also not been around for very long, and there are many plausible scenarios by which our geological presence on this planet may be relatively brief. The famous Drake Equation mathematically frames the question, but that does not help us fill in all the variables. We simply don’t know. It is possible we are the only current technological species in the galaxy, or there may be hundreds, or even thousands. It also possible that ancient technological species, now long dead, have left behind evidence of their existence – their radio signals still streaming through space, or massive megastructures that reengineered entire stellar systems.

The reason I think finding such evidence is our best hope of detecting non-Sol life is that astronomers can search vast parts of the universe, and frequently detect even extremely rare situations and events. We have increasingly powerful and sophisticated instruments, like the James Webb telescope, that will help us find such things, if they are out there. Webb recently helped astronomers resolve an anomalous finding, although this one has a natural explanation (as all anomalies have gone before it, so far).

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Oct 11 2022

How Much Meat Should We Eat?

Published by under General

This is one of those complex questions that comes up frequently when talking about related issues, and it’s always challenging to give a short answer. Often there are unknown or speculative elements to the analysis, which make it difficult to have an objective or definitive answer. What I would like to do here is mostly frame the relevant considerations and give my current understanding of the evidence, with possible caveats. Obviously this is going to be a quick overview of a lot of complexity – I see it more as a starting point than a firm conclusion.

There are really four questions hiding in this one question about meat consumption, and I will address each separately. These are: health effects, environmental effects, ethical considerations, and local considerations such as cultural tradition.

Starting with the last item first, this can actually be the trickiest to answer. What should be our attitude toward populations with a deep cultural history that includes things like hunting whales or polar bears, using endangered animals parts for folk remedies, or destructive farming practices. Animal rights organizations try to walk a fine line:

“For those of us who are not members of those communities, it is not our role to decry traditional practices that have important cultural, nutritional, and other necessary value, particularly when they are used respectfully and humanely.”

But what about when their practices are not humane? And what is considered respectful? Often such considerations are tainted by a “noble savage” myth that such peoples always live in harmony with nature, but human populations throughout history have generally been disruptive to their environments. There is no perfect answer here. Those from developed nations do have little moral standing to lecture native populations about nature management. Often we are essentially asking them to change their practices to help solve a problem we created. But then again, should we allow whale species to be hunted to extinction because we feel guilty? It’s a no-win scenario. We just have to take a balanced approach that thoughtfully considers many factors, and searches for acceptable alternatives.

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Oct 10 2022

Nitrous Oxide as a Biosignature

Published by under Astronomy

I still find it amazing that we can look at an astronomical object light years away and determine its chemical composition in detail. This is referred to as spectral analysis – looking at either absorption or emission lines in the wavelengths of light. Isaac Newton was the first to demonstrate that white light from the sun is actually composed of the full spectrum of visible light, which can be separated by passing through a prism which bends light of different colors to different degrees, causing it to spread out into the familiar rainbow pattern. However, Newton was not the first to discover this effect, but prior to his experiments it was believed the prisms colored the light. Newton demonstrated that the colors were already there.

In 1802, William Hyde Wollaston improved on the prism design to produce more detailed spectra. He discovered black bands of missing wavelengths in the light. These are absorption lines – chemicals will absorb specific wavelengths of light depending on their chemical structure (corresponding to the orbits of electrons which absorb the energy of light to jump to a higher energy orbit), with the pattern of absorption lines being a signature of the specific chemical. There are also emission lines in which specific wavelengths of light are created depending on the source of the light. Therefore we can tell the chemical composition of a star by looking at its emission lines, and we can also tell its temperature as different elements and chemical have peak emissions at different temperatures. When starlight passes through a gas cloud and material in the cloud will absorb specific frequencies of light, telling us what it is made of.

Therefore, if an exoplanet with an atmosphere is discovered through the transit method (it causes the light of its star to dim when it blocks a small amount of it as it passes in front), then we may be able to detect some of the light from that star as it passes through the atmosphere of the planet. This requires high resolution imaging, but within our current capabilities for some exoplanets (and now extended with the James Webb Space Telescope). With spectral analysis we get information about the composition and temperature of the exoplanet’s atmosphere. Astronomers are most interested in using this method to look for signs of life (so-called biosignatures). What would a sign of life in a planet’s atmosphere be?

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Oct 07 2022

Chicxulub Impact Triggered Mega-Earthquake

Published by under General Science

At this point there is little question that a giant asteroid, 10 kilometers across, impacted the Earth about 66 million years ago. Evidence for this impact began with an iridium layer discovered at the Cretaceous-Paleogene, or K-Pg, boundary. Something deposited an unusually high level of iridium in a brief event all around the world. Later the likely crater resulting from this impact was found in Chicxulub, Mexico. Multiple other discoveries have supported this conclusion, including the fact that this impact was the likely cause of the dinosaur extinction. There was also massive volcanic activity at that time, and dinosaur populations may have been in decline, but that was likely a side show. The main event was the impact.

Such an impact would have released a tremendous amount of energy (10^23 joules), equivalent to a 100 million megaton bomb. There were multiple effects of that impact. One is that a lot of Earth crust material would have been melted and thrown up into the atmosphere, but at less than escape velocity so ultimately raining back down to Earth. Some of these molten droplets cooled into glass spherules as they fell, raining tiny glass beads onto the Earth – creating another geological marker for the impact.

The asteroid impact was essentially in the Gulf of Mexico, causing a massive tsunami that swept over North America. My favorite geological find resulting from this is at the Tanis site in Hell’s Creek. The massive tsunami washed lots of fish and other sea life across the continent, and deposited them in a valley, creating a large jumble of fossils all deposited at once. Scientists know they are from the day of the impact because the fish have glass spherules stuck in their gills – they breathed them in while still alive.

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Oct 06 2022

3D Printing Implantable Computer Chips

This is definitely a “you got chocolate in my peanut butter” type of advance, because it combines two emerging technologies to create a potential significant advance. I have been writing about brain-machine interface (or brain-computer interface, BCI) for years. My take is that the important proof of concepts have already been established, and now all we need is steady incremental advances in the technology. Well – here is one of those advances.

Carnegie Mellon University researchers have developed a computer chip for BCI, called a microelectrode array (MEA), using advanced 3D printing technology. The MEA looks like a regular computer chip, except that it has thin pins that are electrodes which can read electrical signals from brain tissue. MEAs are inserted into the brain with the pins stuck into brain tissue. They are thin enough to cause minimal damage. The MEA can then read the brain activity where it is placed, either for diagnostic purposes or to allow for control of a computer that is connected to the chip (yes, you need wired coming out of the skull). You can also stimulate the brain through the electrodes. MEAs are mostly used for research in animals and humans. They can generally be left in the brain for about one year.

One MEA in common use is called the Utah array, because it was developed at the University of Utah, which was patented in 1993. So these have been in use for decades. How much of an advance is the new MEA design? There are several advantage, which mostly stem from the fact that these MEAs can be printed using an advanced 3D printing technology called Aerosol Jet 3D Printing. This allows for the printing at the nano-scale using a variety of materials, included those needed to make MEAs. Using this technology provides three advantages.

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Oct 03 2022

Pangenome of the Domestic Silkworm

Published by under Technology

Recently scientists have published the complete pangenome of the domesticated silkworm (Bombyx mori). I thought this was intriguing for several reasons. First, I don’t think I have discussed previously here what a pangenome is. Second, I never thought about the fact that the silkworm is technically a domesticated animal. And third, silk is an important material that has been the focus of much scientific research, so of course I was interested in how this latest research might affect that.

A pangenome (I have seen “pan-genome”, “pangenome”, and “pan genome” – I’m just going to go with pangenome) is the complete genetic profile of a species (or more broadly, a clade) including all variants. So a pangenome of Homo sapiens would include a map of every gene that exists in people, not just a genome of one person.  This provides a more complete picture of the genetics of that species than a single genome would. A pangenome can also provide information useful for determining the evolutionary relationships among varieties of a clade. It can also be useful to track specific genes and the traits that they control.

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