Hello, and welcome to Random Walk, a sciencey podcast where we take multiple steps of unit length, each with directions selected independently from the previous step. I’m your host Adam Fortais.
This week’s random walk is probably the first one I ever met. Brownian Motion usually follows a random walk. Allow me to explain.
This motion is named after the botanist Robert Brown, who first described the phenomenon in 1827, while looking through a microscope at pollen of the plant Clarkia pulchella immersed in water. In 1905, almost eighty years later, theoretical physicist Albert Einstein published a paper where he modeled the motion of the pollen particles as being moved by individual water molecules, making one of his first major scientific contributions. The direction of the force of atomic bombardment is constantly changing, and at different times the particle is hit more on one side than another, leading to the seemingly random nature of the motion. This explanation of Brownian motion served as convincing evidence that atoms and molecules exist and was further verified experimentally by Jean Perrin in 1908. Perrin was awarded the Nobel Prize in Physics in 1926 “for his work on the discontinuous structure of matter”.https://en.wikipedia.org/wiki/Brownian_motion
- Jessie D takes us deeper into the abyss of Subnautica on Gamer’s Guide to Ecology
- Looks like yuh brought a haggis to a clahmet fight. The biggest climate conference is underway, and they want you to know how much carbon you make by eating their food
- Genetic testing shows California Condor produced sons… and didn’t even need a father. A couple of virgin births, if you will. The segment is so fertile for jokes, but I promise I will abstain. And finally,
- Watching NASA play “Armageddon” starring Bruce Willis. You aren’t gunna want to close your eyes, you aren’t gunna wanna fall asleep etc etc etc, and you won’t want to miss a thing from this episode.
But first: This podcast is brought to you by scientificanada.ca . The goal of scientificanada is to get real science to real people, which we do by producing entertaining and informative content about research, academia, and being a curious nerd. A big part of our thing is finding and promoting new projects and new voices with financial support and expertise. If you have an idea for a project, we’d love to hear from you. Head to scientificanada.ca to see some of the shows and articles we’ve helped with, and if you want to discuss details, you can find me on twitter at AdamFortais or email me at email@example.com . Support for our projects comes from our generous and very very smart patreon subscribers. Find out more about how you can help us with our next projects over at patreon.com/scican . Thanks!
**Fade music out**
Block One (C): Gamer’s Guide to Ecology: Subnautica 2
So academic twitter has been on fire with news coming out of the COP26 meeting. It’s the world’s biggest climate conference, and I definitely had to look up the full name because, what is COP26? Here it is: 26th UN Climate Change Conference of the Parties.
So there are a lot of news threads to pull on here, and plenty of sources are covering it, one of which is Nature News. So, for now, I’ll leave coverage of all the promises and whatnot to them, but I would like to take a second to talk about one interesting aspect of the meeting.
COP26 is being hosted in Glasgow, and one of the cool things about travelling for conferences is getting to try the local food. This conference has taken a local approach, attempting to source much of its food from Scotland. It’s also made an effort to make its available menus heavily plant-based. The meat and dairy industry is a huge contributor to CO2 emissions, which has led many to reduce the amount of animal products in their diet. In particular, they advertise that about 42% of their menus are entirely plant-based.
The conference organizers are also trying to get a bit more quantitative with all of this. They have hired Swedish start-up Klimato to provide carbon costs associated with every menu option. Every menu includes the following quote:
“Today, an average meal has a carbon footprint of 1.7 kg CO2e in the UK. According to the WWF, we need to get this number down below 0.5 kg CO2e to reach the goals defined in the Paris Agreement. By including climate labels on our menus, we aim to make it easier to achieve this goal – together.”
Then, after each item on the menu, a CO2 value is given. Allow me to present some breakfast options:
Of course, these aren’t what I’d call full meals. Let’s compare a few other menus,
Here, everything is above the WWF-guided 0.5 kg CO2, even the plant-based tempura broccoli. However, the salad menu keeps every option below 0.5 (even the ones sporting chicken and fish).
The heavy hitters though, really smash the 0.5 target.
As far as “local cuisine”, they would be remiss to not offer haggis in some form. Here, they offer it in two forms.
Neeps and Tatties are turnips and mashed potatoes. Haggis, if you’ve never had the pleasure, is haggis, the national dish of Scotland, a type of pudding composed of the liver, heart, and lungs of a sheep (or other animal), minced and mixed with beef or mutton suet and oatmeal and seasoned with onion, cayenne pepper, and other spices. The mixture is packed into a sheep’s stomach and boiled. My mom is a fan… but I can’t help thinking about this Michael Meyers quote from his pre-Austin Powers role in So I Married an Axe Murderer…
It’s a mystery to me what exactly they do to make vegetarian haggis… Whose stomach do they boil it in?
Ok, so I love the idea. But of course, it’s not perfect. I would have preferred to see the bold choice of cutting animal products completely from the menu, provided they could do it in a way that satisfied everyone’s dietary requirements. I’ve linked to an article in the show notes that talks about why we should be disappointed with this effort. Some of the more salient points they bring up is, CO2 footprint isn’t everything when it comes to environmental impact. There are plenty of ways to disrupt ecosystems and damage the environment that don’t require CO2. It’s also worth asking how much of the carbon-expensive materials they stock at the conference, and where does it go if it doesn’t get used? I know the caterers have made a point of designing the menu to have a lot of ingredient overlap, but they would likely have had to place their orders and stocked all of their menu items ahead of time. Makes one wonder if ordering based off the CO2 cost means anything at all.
Overall, I think it was a great idea to use the menu as a way to emphasize that every decision has a climate implication. I guess I’m just a little bummed that they sort of stopped there. They could have really went for it and heck, maybe converted some meaters that there are plenty of satisfying alternatives they can supplement their diets with. Of course, the real kick in the teeth is how much air travel was a result of this conference. I’d have thought after 2 years of virtual everything, there would be enough motivation to move the show online.
Maybe next year.
Block Three (N): California Condors Are Capable of ‘Virgin Birth’
I haven’t seen a single Jesus Mary and Joseph reference in relation to this story, and I’m not going to be the first to do it. You’ll just have to make it up for yourself. A case of “virgin birth” has been reported in a California Condor lineage. These very endangered birds have been the focus of study and captive breeding since 1983 when they numbered only 22. They have grown in number to just over 500, but two birds in particular have been making news in the last few weeks.
By Stacy from San Diego – california condorUploaded by Snowmanradio, CC BY 2.0, https://commons.wikimedia.org/w/index.php?curid=8031347
SB260 and SB517, as they are known in the California Condor “studbook” underwent genetic sequencing as part of the breeding program, and to the scientists’ surprise, a big fat 0% of their genetic information matched with their supposed birdfathers. Rather, all of their genetic material appears to have come from the mother, implying that the mother’s eggs were able to self-fertilize in some way.
I was shocked to learn that virgin birth (aka parthenogenesis) is actually not all that uncommon in fish, amphibians and reptiles. But very rarely has it been seen in birds, although some cases have been studied in chickens and turkeys. This type of reproduction has been induced artificially in a few species including fish and amphibians. Also worth pointing out, another article in The Atlantic from 2013 reported on an “immaculately conceived” anteater… a reference to Jesus and Mary. Christian listeners will be quick to point out here that the “immaculate-ness” of Mary’s conception was not about sex but “sin”, but whatever, I’m sure the anteater lived a good life.
So, it’s kind of interesting, this information was discovered years after these condors died, and kind of as a fluke, by researchers going through the big ole DNA database of condors. It’s a testament to the value of keeping good lab notes, they were also able to connect the bird’s ID to physical descriptions of the birds. A quote from The Atlantic article, which I’ll link to in the show notes:
“But both of the condors did have some documented health issues. SB260, a male hatched at the San Diego Zoo Safari Park in 2001, died two years later after being released into the wild—he was always small and did not integrate well with the wild birds. SB517, a male hatched at Los Angeles Zoo in 2009, had a curved spine and trouble walking. He was never released into the wild and died in captivity at about age eight. (California condors usually live for decades.) “They certainly weren’t, shall we say, shining specimens of the condor,” says Demian Chapman, a biologist at the Mote Marine Laboratory and Aquarium, who has studied parthenogenesis. That’s not uncommon for parthenogenetic animals, also known as parthenotes.”
So how does parthenogenesis work? Now from wikipedia
“Normal egg cells form in the process of meiosis and are haploid, with half as many chromosomes as their mother’s body cells. Haploid individuals, however, are usually non-viable, and parthenogenetic offspring usually have the diploid chromosome number. Depending on the mechanism involved in restoring the diploid number of chromosomes, parthenogenetic offspring may have anywhere between all and half of the mother’s alleles. The offspring having all of the mother’s genetic material are called full clones and those having only half are called half clones. Full clones are usually formed without meiosis. If meiosis occurs, the offspring will get only a fraction of the mother’s alleles since crossing over of DNA takes place during meiosis, creating variation.
Parthenogenetic offspring in species that use either the XY or the X0 sex-determination system have two X chromosomes and are female. In species that use the ZW sex-determination system, they have either two Z chromosomes (male) or two W chromosomes (mostly non-viable but rarely a female), or they could have one Z and one W chromosome (female).”
So I would have thought these condors would be male, but condors have the ZW-scheme. So actually, all parthenote condors are male. It’s also worth noting that usually, in bigger animals like this, parthenotes don’t normally live very long. Although these birds didn’t live a full condor life, they made it further than one would expect! It’s also important to note that even though their physical issues sound like the kind of traits you would expect from parthenotes, we can’t say for sure that is what their problem was.
So, the researchers are digging into the full genome of these birds (did you know, a lot of genetic sequencing only looks at a small portion of the subjects genome? Places like 23 and Me and others use this partial sequencing technique, but there is a lot of other information that can be pulled through full sequencing). It’s really too early to say much definitively about this strange situation, so I’ll leave you with one more Atlantic quote;
But that doesn’t explain why some females go through parthenogenesis but not others. The poultry industry—which, given its interest in bird breeding, has extensively studied parthenogenesis—has found that a number of factors influence it in turkeys and chickens. One is genetics, says Ramachandran. Different poultry breeds have significantly different rates of parthenogenesis, ranging from 0.16 percent in Barred Plymouth Rock chickens, to 3 percent in commercial turkeys, to 16.9 percent in Beltsville small white turkeys. Poultry scientists have also succeeded in selecting for parthenogenesis, increasing the incidence in Beltsville small white turkeys more than threefold, to 41.5 percent in five generations. Environmental factors—like high temperatures or a viral infection—also seem to trigger poultry parthenogenesis.
Block Four (N): NASA crashes stuff into a meteor for a reason?
Remember that movie Armageddon?
Well, we are trying it. For practice. It’s not actually happening, but NASA wants to practice just in case. Just in case… To be clear, we aren’t drilling into it or planting a ‘nuke, we are just smashing a super expensive satellite into it.
Ok, let’s go over the mission.
Double Asteroid Redirection Test (DART) Mission: Schematic of the DART mission shows the impact on the moonlet of asteroid (65803) Didymos. Post-impact observations from Earth-based optical telescopes and planetary radar would, in turn, measure the change in the moonlet’s orbit about the parent body.
Credits: NASA/Johns Hopkins Applied Physics Lab
2-mass system, a big one and a small one. We’re going for the small one.
Total system mass and density is 5.278e11 kg and 1.7 g/cm^3 . The smaller mass (moonlet) is our target, which is 160 m in diameter (compared to the 760 m diameter of the main body). Assuming uniform density we’re talking something like 3.65e9 kg for our target. I couldn’t find the target’s velocity at impact, and since it’s orbiting the larger body, making contact at different points in the orbit will significantly affect its velocity at any moment. Let’s call it zero. This will give us a sense of the change in velocity the moonlet should experience.
We are launching a satellite that will pretty much completely disintegrate on impact. I couldn’t find the mass of the satellite, but if I remember correctly, they tend to be about the mass of a car? Let’s say 2000 kg. It should have a velocity of about 6600 m/s (or 24000 km/hr). So this gives us a momentum of about 1.3e7 N-s (or kg-m/s).
(Data from NASA)
So let’s assume all of that momentum gets transferred to the moonlet. If the moonlet were the same size as the satellite, we may expect it to go firing off at the same 6600 m/s the satellite came in at. But the moonlet is enormous in comparison. So, drumroll… what is the change in velocity we expect from the moonlet?
So… that’s really not a lot. About twice the speed of an ordinary snail. They are planning to send a follow-up mission to check in on things and see what happens, but I don’t have a good sense of how they will measure such a small velocity change. I have a few ideas though.
1) Re-measure the moonlet’s orbital period around the larger body.
Right now NASA has pretty good data on the motions of this system. They cite a distance between the two bodies as 1.18 km (no uncertainty, and I assume a circular orbit), and an orbital period of 11.92 hours. If the moonlet slows down by a bit (let’s assume the orbital distance stays the same for now, it’s a pretty good assumption anyway), then the orbital period will slow down. Measure the new period and bam, you have your change in velocity. Let’s put some numbers to it.
Orbital circumference = 2*pi*r =2*pi*(1.18e3 m) = 7.4e3 m = 7.4 km
Orbital velocity = distance/time = 7.4 km / 11.92 hours = 0.621 km/hr
**keep in mind this is not the absolute speed of the moonlet. The whole system is moving at some average speed, this is just the relative speed compared to its buddy.
So we can estimate the new orbital velocity will be something like, 0.61 km/hr. Retrace our steps a bit, we find an orbital period of …
12.1 hours … or 12 minutes.
Again, small change. But measure the time it takes for the moonlet to make 10, 100, or 1000 revolutions around its buddy, and we’re talking about a 2 hour difference, 200 hour difference, or 2000 hour difference. And the nice thing, at this point, we’d just have to hit our stopwatch and count.
2) The other idea they might consider is looking for a change in orbital distance.
This idea is kind of just another way to repackage the last technique. So, when one object orbits another steadily, it never falls to the surface. But that doesn’t mean gravity has stopped working on the system. There is still a constant gravitational attraction between the bodies, attempting to make them smash into each other. But the orbital velocity, which is always 90 degrees to the pull of gravity (assuming circular orbit) makes it so the moonlet keeps “missing”. I had a professor explain orbit as “falling to earth but missing the ground”. So if the moonlet is in a steady orbit and it gets a sudden increase in speed, you might expect to “miss the ground” by a larger margin than before. This is effectively increasing the orbital distance, or the distance between the two bodies. The opposite is true too. The thing that’s making you miss is its orbital velocity, so slowing it down should bring the moonlet closer to its big friend. There are more conceptual moving pieces to consider in this argument, but that’s the jist. If they have a clean way of measuring distances well, they might look at this option. But I think they typically USE the orbital mechanics to deduce distances a lot of the time. If I had to guess, they will do option 1).
So, when is all this happening? The mission launch is set for November 23, with the impact scheduled for September 2022. As far as media coverage, I’d guess we will hear about this one more time during a slow news week, maybe in the summer, and then get a whole bunch of Armageddon, Deep Impact, etc screenings at indie theaters. Not that those movies were particularly “good”… but hey, they are fun and come next september, will be timely.
That’s it for this episode. If you have comments or questions, find me on Twitter at AdamFortais or email me at firstname.lastname@example.org .
Find more of Jessie de Haan on Twitter @deHaanJ , and make sure to follow them on Twitch at justjessieD.
Our music was provided by my friends from the band Boonie. Find them at boonie.rocks .
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See ya later!