Archive for November, 2021

Nov 23 2021

DART Asteroid Deflection Mission Ready for Launch

Published by under Astronomy

Why is NASA planning on deliberately crashing a spacecraft into a small asteroid that poses no threat to the Earth? It’s a test of an asteroid deflection system – DART (Double Asteroid Redirection Test). Why the “double”? Most articles on the topic don’t say, and I had two hypotheses. The first is that the mission is targeting two asteroids, or actually a binary asteroid, Didymos (Greek for “twin”). Didymos has a primary asteroid that’s 780 meters across, and a smaller secondary asteroid 160 meters across that actually orbits the primary asteroid, and is therefore called a “moonlet”. However, the mission was originally supposed to be part of a pair of missions, with the second one by the ESA who were going to send their AIM probe to orbit and monitor Didymos during the DART mission. The ESA cancelled this mission, however, and now Didymos will be monitored by ground telescopes. But it turns out the “double” refers to the twin asteroids.

In any case, the purpose of the mission is to test out an asteroid defense system known as a kinetic impactor. The course of an asteroid can be altered by ramming something into it very fast. At first this seems like a crude method, but sometimes simple is best. The mission is part of NASA’s Planetary Defense Coordination Office. The European Space Agency (ESA) is also engaged in planetary defense, although their cancelling of AIM was disappointing. There are also international meetings on planetary defense, with calls for the USA, Russia and China to work together on this project. Russia, for their part, has proposed repurposing old ICBMs as asteroid busters. This would not be a kinetic impactor, but actually use nukes to blow up asteroids.

The DART mission is the first real test of an asteroid defense system. The spacecraft uses electric motors powered by solar panels, and will be going 6.6 km/s when it impacts the smaller Didymos asteroid. This impact will only divert the orbit of the asteroid by less than a percent, but that will be enough to change its orbit around the larger asteroid by several minutes, which can be observed from Earth. The craft is scheduled to launch tonight, November 23rd, at 10:21 pm PST aboard a SpaceX Falcon 9 rocket. It will intercept Didymos in late September 2022.

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Nov 22 2021

The Efficiency of Data Storage

Published by under Technology

As our world becomes increasingly digital, math becomes more and more important (not that it wasn’t always important). Even in ancient times, math was a critical technology improving our ability to predict the seasons, design buildings and roads, and have a functioning economy. In recent decades our world has been becoming increasingly virtual and digital, run by mathematical algorithms, simulations, and digital representations. We are increasingly building our world using methods that are driven by computers, and the clear trend in technology is toward a greater meshing of the virtual with the physical. One possible future destination of this trend is programmable matter, in which the physical world literally becomes a manifestation of a digital creation.

What this means is that the impact of even tiny incremental improvements in the efficiency of the underlying technology, computers, has increasingly powerful reverberations throughout our economy and our world. The nerds have truly inherited the Earth. This is why it is interesting science news that computer scientists at MIT have developed a tweak that may improve the efficiency with this computers store and retrieve data. William Kuszmaul and his team have demonstrated a way to improve what is known as linear probing hash tables. The underlying concept is interesting, at least for those curious about how the increasingly ubiquitous computer technology works.

Hash tables were developed in 1954 as a way for computers to store and locate data. When given a piece of data to store, the computer will calculate the “hash function of x, h(x)”. This will generate an essentially random number from 1 to 10,000. The computer then goes to that location in the sequential data array and stores the data there. If that location is already occupied by data then it probes forward until it finds an open slot and it puts the data there. When searching for the data to retrieve it does the same thing – goes to the assigned location and if the data is not there it probes forward until it finds it. If it encounters an open position first it concludes the data has been deleted.

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Nov 16 2021

Russia Shoots Down Satellite

Published by under Astronomy

In the movie Gravity (one of my favorite movies, highly recommended), the Russians shoot down one of their own satellites in order to test their anti-satellite system. The debris from this satellite crashes into other satellites causing a cascade of debris, which travels around the Earth eventually crashing into the ISS and a space shuttle in low Earth orbit. I have to point out that the orbital mechanics in the movie are terrible. One big problem is that objects in the same orbit are going the same velocity, by definition. So the debris would not have been flying by so fast. But putting all that aside, the core concept that space debris is a huge problem, and blowing up satellites in orbit is a horrifically bad idea, is valid.

Which is why it is head scratching that 8 years after Gravity came out Russia would blow up one of its own satellites in orbit in order to test its anti-satellite system. Didn’t anyone in Russia see this movie? More seriously, they should know that this is a terrible idea, contributing significantly to the problem of space debris. The US and other space-faring nations are not happy. In a state department release they said:

“The test has so far generated over 1,500 pieces of trackable orbital debris and hundreds of thousands of pieces of smaller orbital debris that now threaten the interests of all nations.”

The astronauts aboard the ISS had to shelter in capsules for safety as a result of the debris. Our goal is to reduce space debris, not significantly increase it. Russia is not the first country to do this. In 2007 China destroyed one of its defunct weather satellites, producing more than 2,000 pieces of trackable debris. After nearly 65 years of putting satellites into orbit, there are now over a million pieces of debris between 1 and 10 cm orbiting the Earth. NASA is tracking 27,000 pieces of larger debris. While space may seem big, low Earth orbit is finite and valuable real estate. Having more than a million pieces of debris flying around is a significant risk. They can damage satellites and threaten crewed missions, such as the ISS. In fact the ISS frequently has to adjust its orbit in order to avoid tracked debris.

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Nov 15 2021

What Came Out of COP26

Published by under General Science

The world met in Glasgow at the COP26 summit to see if politicians could put their heads together and work out a deal to limit global warming. The outcome was as much of a mess as you probably think it was. I suspect this is because their entire approach to the problem was flawed. That doesn’t mean it was hopeful or fruitless, just that it was highly problematic, and yielded highly problematic outcomes.

As an analogy, the psychological literature indicates that the best way to achieve a goal is not to focus on the goal but on the steps you need to achieve that goal. Richard Wiseman points this out in his book, 59 Seconds. Imagining yourself having achieved your goal is not helpful, and may even be counterproductive. Rather, you should outline the precise steps you need to take in order to achieve your goal. Chart a path, don’t just indicate your destination. I might humbly suggest that our world leaders would take this advice when they approach the problem of climate change.

As far as I can tell from all the reporting from COP26 (and the Paris agreement, and other climate agreements), the focus is primarily on the goal. We want to limit climate change to 1.5 C temperature rise above pre-industrial levels. That’s a great goal – now how are we going to achieve it? This latest agreement goes a bit further. It lays out several actual steps that are critical to achieving the temperature goal. One is to “phase down” coal. At the last minute India objected to the agreement to “phase out” coal and a watering down of the language was necessary to get an agreement. There was also an agreement to reduce deforestation, an admirable goal that is vital to tackling climate change.

While this language is one step closer to laying out actual policy changes, it is still not quite there. Politicians are straining to come up with language to portray the deal in a positive light, preferring the word “progress” over all others. But few are willing to use the word “success”, which is an indication that many think the conference was essentially a failure. But I think the failure was baked into the process. This is because you can’t just tell countries like India, who are banking on coal to develop their nation and reduce poverty, to phase out coal.

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Nov 11 2021

Current Warming Unprecedented

Published by under Pseudoscience

While the world debates how best to reverse the trend of anthropogenic global warming (AGW), scientists continue to refine their data on historical global temperatures. A recent study published in Nature adds to this a high resolution picture of average surface temperatures over the last 24,000 years, since the last glacial maximum. The study reinforces the conclusion that the last century of warming is unprecedented over this time frame, and does not reflect any natural cycle but rather the effects of human forcing.

To construct their map of past temperatures, the researchers combined two methods. They used a dataset of chemical analysis of marine sediments, which are affected by local average temperatures. They combined this with a dataset based on computer-simulated climate models. The idea was to leverage the strengths of each approach to arrive at a map of historical surface temperatures that is more accurate than either method alone.

Of course, no one study is ever the final word, but this reconstruction is in line with other research using independent methods and data. The authors also draw two other main conclusions from their data. There has been a debate about whether or not the last 10,000 years had a small warming trend, and this graph supports that conclusion. Further, the authors conclude that the main driver of the large warming trend starting around 17,000 years ago is the retreat of the glacial ice sheets, but that the main driver of the rapid warming over the last 150 years is increasing green house gases. The rate of this recent warming is also out of proportion to any natural cycle detected in the last 24,000 years.

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Nov 09 2021

Brain Stimulation for Cognitive Control

Published by under Neuroscience

A newly published study presents a proof-of-concept for using deep brain stimulation controlled with artificial intelligence (AI) in a closed-loop system to enhance cognitive control, suggesting it might be effective for a number of mental illnesses. That’s a lot to unpack, so let’s go back to the beginning. The most fundamental necessary to understand what is going on here is that your brain is a machine. It’s a really complicated machine, but it’s a machine none-the-less, and we can alter the function of that machine by altering its physical state.

This may seem obvious, but actually people are generally psychologically biased against this view. This may, in fact, be a consequence of brain function itself, which evolved to create a seamless stream of consciousness, an illusion of self unaware of all the subconscious processes that make up brain function. This is why we tend to interpret people’s behavior in terms of personality and conscious choice, when in fact much of our behavior is a consequence of subconscious processes. We are also biased to believe that people can think or will-power their way out of mental illness.

The more we understand about how the brain functions, however, the more it becomes apparent that the brain is just a glitchy machine, and lots can go wrong. Even when functioning within healthy parameters, there are many trade-offs in brain function, with strengths often coming at the price of weaknesses. We need to look out for our own interests, for example, but this comes at the price of anxiety and paranoia. But there are some brain functions that are so basic they are almost universally useful, and impairment of them can cause of host of problems. One such basic brain function is called cognitive control, which is essentially the ability to determine what thoughts and actions will be the focus of your brain’s attention.

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Nov 08 2021

Hypervelocity Dust Impacts

Published by under Astronomy,Technology

Space is an incredibly hostile environment, and we are learning more about the challenges of living and traveling in space the more we study it. Apart from the obvious near vacuum and near absolute zero temperatures, space is full of harmful radiation. We live comfortably beneath a blanket of protective atmosphere and a magnetic shield, but in space we are exposed.

Traveling through space adds another element – not only would radiation be passing through us, the faster our ship is traveling the more stuff we would be plowing through. Space is not empty, it is full of gas and dust. In our own solar system, most of the dust is confined to the plane of the ecliptic, in what’s called the zodiacal cloud. But of course, if we are traveling from one planet to another, that would be the plane we are traveling in. At interplanetary velocities, assuming we want to get to our destination quickly (which we do, to minimize exposure to all that radiation) our craft would be plowing through the zodiacal cloud.

We now have some measurements from The Parker Solar Probe regarding the effects of impacts with dust at high velocity. The Parker probe is the fastest human object at 180 kilometers per second. It is also the closest probe ever to the Sun and the one able to operate at the highest temperature. To accomplish this it must keep its heat shield oriented toward the sun. Meanwhile it is encountering thousands of dust particles, tiny grains between 2 and 20 microns in diameter (less than that standard measure of all things tiny, the width of a human hair). We now have data from the probe about the effect of these impacts. Dust grains are striking the probe at hypervelocity, greater than 10,800 km per hour. When they hit they are instantly heated and vaporized, along with a small portion of the surface of the probe. The resulting cloud of debris is also hot enough to become ionized, turning into a plasma. Smaller grains are entirely vaporized in less than a thousandth of a second. Larger grains also give off a cloud of debris that expands away from the craft.

The authors report that the effect of this is:

Some of the impactors encountered by Parker Solar Probe are relatively large, resulting in plasma plumes dense enough to (i) refract natural plasma waves away from the spacecraft, (ii) produce transient magnetic signatures, (iii) and drive plasma waves during plume expansion.  Further, some impacts liberate clouds of macroscopic spacecraft material which can result in electrostatic disturbances near the spacecraft that can linger for up to a minute, which is ~10,000 times longer than the transient plasma plume.

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Nov 04 2021

Securing Data with the Laws of Physics

Published by under Technology

Data security sounds like a boring topic. However, it is quickly becoming one of the most important technologies in our modern world. Our data, communications, and transactions are increasingly digital, and they are all vulnerable to hacking. It’s estimated that hacking costs the world about $6 trillion per year as of 2021, and increasing. Slightly more than half of data breaches are due to hacking (the rest to some form of social engineering, like phishing). Cyberwarfare is now the new warfare between developed nations, and critical infrastructure may be vulnerable to hacks. Companies are now under constant attack by ransomware. Individuals may have their digital identities stolen, losing their savings and disrupting their lives.

About half of the problem is individual behavior, and this can be mitigated through education, company and governmental policies, and improved tools. But the other half is not due to any failure of personal behavior, but rather to straight-up hacking. This problem requires new technology to fix (in addition to institution-level responsibility to secure systems as much as possible). One aspect of hacking-resistance is authentication – you need a code to get into a system. This is the focus of a potential incremental advance in authentication systems, but let’s give some further background first.

Authentication involves a prover and a verifier. They might, for example, share a code, and the prover needs to provide the code to the verifier to confirm their identity. The inherent problem with this system is that the prover, by necessity, has to give up personal information (such as their code) during the verification process, and this is a point of attack for a hacker. To solve this problem, in the 1980s, programmers developed so-called “zero-knowledge proofs”. The idea is that the prover can demonstrate they have the code without giving up the code itself, and so it remains secure.

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Nov 02 2021

Making Biofuel on Mars

Published by under Astronomy

NASA and China are both planning on sending people to Mars sometime in the 2030s. This is an ambitious goal and I would be pleasantly surprised if either hit that target. Sometime in the 2040s, and only if plans go fairly well, may be more realistic. There are many challenges to such a mission. NASA’s plan is to work out most of the technology by going back to the Moon first, setting up a semi-permanent presence there, and essentially using it as a stepping stone to Mars.

But Mars presents some of its own challenges, primarily, of course, the distance. Just getting to Mars and back is pushing the limits of how long astronauts can safely stay in space due to radiation exposure. There are no practical plans for shielding from cosmic rays (solar radiation is more manageable) and so NASA’s plan is just to keep missions within the three year safety window.

Another challenge Mars does not share with missions to the Moon is sourcing the fuel for a return trip. If you recall the rocket equation, the more fuel you need to get to your destination, the more fuel you need to carry that fuel, and so on. So small changes in weight and the needed change in velocity can lead to huge increases in fuel needs. We can get to the Moon with enough fuel to get back. We cannot get to Mars with enough fuel to get back. A mission to Mars will need to refuel on Mars in order to make the return trip. Robotic missions to Mars are one-way trips, so this has not been an issue before, but we would like to get our astronauts back home.

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Nov 01 2021

The Sri Lanka Organic Experiment

Published by under General Science

Cautionary tales are extremely useful, as long as we take the right lessons away from them. As the saying goes, the best way to learn is from mistakes, but even better is to learn from someone else’s mistake without having to commit it yourself (and suffer the consequences). Sri Lanka has now made itself into a cautionary tale, and I would like to amplify any learning that can come from it. The primary conceptual lesson here is that – when ideology trumps science, the outcome is likely to be very bad.

There is also a specific lesson here. Organic farming may sound good in principle (if you just listen to the ideological marketing), but in practice it is a disaster. Sri Lanka has decided to do what other countries have done before, namely impose from above a commandment on how to run an industry based entirely on the philosophical beliefs of the leader. Perhaps the most famous example of this is Lysenkoism in the former Soviet Union, where the archaic ideas of geneticist Trofim Lysenko were given official support and decimated Soviet agriculture, costing millions of lives.

President Gotabaya Rajapaksa of Sri Lanka has done something similar – banning agrichemicals in Sri Lanka and forcing all farmers to farm organically. The result was absolutely predictable, a crash in agricultural output. While Sri Lanka is a net food importer, they still are dependent on local rice and other staple crop productions. Their exports are also mainly agricultural, such as tea, rubber, and many spices. Some reporting has focused on the timing of the change, during a fragile recovery from a pandemic. Also some have pointed out that going suddenly full organic is a problem because most farmers don’t know how to do it, and there was no adjustment period.

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