Beamer

Woke up to it, been blaring along to the lyrics I barely understand all day, my neighbours probably think I am having some sort of episode.

Wiki has a helpful list. I like the Czech attitude, their space agency is just a department of their Ministry of Transport. Like, space, it's just another destination man. https://en.wikipedia.org/wiki/List_of_government_space_agencies I think you can pretty much follow the Pareto Principle there. 80% of the trash is from 20% of the countries who ever launched anything into orbit. French Guiana is part of France.

ArsTechnica did an enlightening story on the wormholes: https://arstechnica.com/science/2022/12/no-physicists-didnt-make-a-real-wormhole-what-they-did-was-still-pretty-cool/

What they actually did was create a quantum state that mimics the properties of a wormhole. No actual wormholes were involved. To me it sounds a lot like one of those "Look what we did, give us a grant! Blockchain! Metaverse! Crypto!" articles. As they described it: "a quantum system that exhibits key properties of a gravitational wormhole but was small enough to implement on existing quantum hardware." It goes beyond my knowledge of quantum computing to determine if it is actually some kind of breakthrough in that field but I'm pretty sure the assertion that "they created a wormhole" is just pertinently false. Edit: since CNN doesn't seem to link to the source, here's the abstract of the actual Nature article: https://www.nature.com/articles/s41586-022-05424-3

Sounds good to me, it should get us by until we find a Tetrahedral world that shouldn't exist. Not bad for a day's work. Of course the hard and time-consuming part is getting it past an international committee, which is probably why we have a definition that seemed barely sufficient half a century ago

Been playing some XCOM 2: War of the Chosen lately, not a new game, continuing a save game, classic difficulty, no mods. Just raided the first Chosen's stronghold in an absolutely brilliant fight, my squad of 6 wiped out a strong welcoming committee of 9 mobs in a single turn without any damage, it was one of those glorious moments. Made it out with 1 minor wounded and 5 tired but satisfied solders, 2 promotions including my first Colonel. I've been playing the UFO/X-COM/XCOM series since the Amiga days (1994), it's one of those games I always get back to.

Seems pretty comprehensive, although I'm missing fall-backs for binary star systems Anywhere you say "orbits a star" I would go for "... or the barycenter of multiple stars" or some such.

First time the Chinese Tiangong Space station has had a hand-over from one crew to the next, it is assumed that from this point forward it will remain permanently occupied. https://www.theregister.com/2022/11/29/china_tiangong_crewed_handover/ https://www.wsj.com/articles/chinas-latest-rocket-sends-new-crew-to-finish-tiangong-space-station-11669747788

According to some 'reputable' news sources, we already do!

I can't remember exactly the last time I saw snow. Living in The Netherlands which is at that point where winters get just cold enough to get a few weeks of ice and snow... or at least it used to when I was younger. I remember throwing snow balls as a kid, going to the (natural) ice rink with my parents, having a day off from school to go ice skating, not a chance of that these days. Amazing to think there are 25 year old people now who have never witnessed a Elfstedentocht...

Yep, that's what I get when posting at 4 AM Awesome image, don't think I had seen the colorized version before. I must admit I was slightly disappointed when it turned out not to be aliens... again

Not all that new, but off an on. Lately I've been doing a round of XCOM2 (sometimes you want to kill some LGM the old-fashioned way ), which drastically reduces the amount of time I spend posting in the "What did you do in KSP today?" thread, which in turn gives me more time to sleuth the science forums for interesting topics.

Well I guess I am a bigger proponent of rigorous definitions than most astronomers. I'm a database specialist by trade, a lot of my work revolves around trying to bring structure into badly indexed data. And that, my astronomer friends, is a BAD index But I suppose they don't worry about the fact that they have to revise the definition every X years or so, that's for people like me to fix afterwards. There's a clear natural index which flows from the orbital mechanics. Planets orbit stars, moons orbit planets, moon-moons orbit moons. If you want to add a mass limit on top of that, sure no problem, over X mass follow the above, under X mass call it a dwarf-something or make up names like 'comet' or 'asteroid' or 'ring system', those are just attributes of each specific body. But the (c) rule always seemed pointless and useless to me. It's a moment in time, maybe it hasn't had the time yet because it migrated orbits or is still young. And of course there's the Uranus/Pluto problem. What about Jupiter, aren't the trojan asteroids considered 'in the neighborhood'? Is that a rigorously defined volume in astronomy anyway? Worst of all it doesn't say anything about the body, it tells you something about its neighborhood, it's in the wrong table! And there are almost more exceptions to it than confirmations of it. No idea why that's there. As for (a), I'm not an expert in the lingo, perhaps they mean 'Sun' as in "central star of a solar system". Do astronomers refer to the Sun as 'Sol'? The fact that it's spelled with a capital makes me think they mean "our star" which is just a revision waiting to happen.

If they grew up there I would assume they would have evolved in a way to deal with it, and perhaps even take advantage of it. It would provide some interesting options for navigation. Imagine living on a world where you could determine your altitude simply by measuring the angle of the ground with the gravity-normal. Global navigation on Earth required the development of extremely accurate clocks as well as many observations of stars. On a Platonic solid you'd have a much easier job as there is the extra information of the angle between the horizon and the direction of gravity. On a sphere that angle is always 90 degrees, so it doesn't give you any information (other than that you are, in fact, on a sphere, dear flat-earthers ), but on a Tetrahedron it would tell you how far away you are from the center of one of the polygons.

If we ever encounter a planet in the shape of a Platonic solid I suspect it will quickly go the way of the dodo Pluto That quote is from a NASA site anyway, they tend to simplify stuff for the general public (makes sense of course, their target demographic is "The American tax payer" rather than "Professional Stargazers"). The literal quote from the IAU's resolution is thus: (1) A planet1 is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (c) has cleared the neighbourhood around its orbit. Source: https://www.iau.org/static/resolutions/Resolution_GA26-5-6.pdf So it looks like they accounted for SmartSes when it comes to (b) The more interesting part is (a) I think. I guess an exoplanet is not considered a planet but is a class by itself, which seems a bit heliocentric and silly to me. By 2006 we had found a good handful of them so it's not like they didn't know exoplanets existed.

Depending on who you ask, it may have happened one or multiple times during the Proterozoic eon. Not since the Precambrian no, but the first land life emerged well before that (In fact I think by now they've pushed it back to 2.7 billion years ago which would put it well into the Archean eon). Snowball Earth is a bit of a bad name, the important part about these periods is that enough potable water is locked in ice that there is no precipitation. That doesn't necessarily mean that the entire earth is covered in snow and ice. There may still be open stretches of ocean and land, as long as the temperature is low enough. If it happened again I think complex life would stand a pretty good chance. The oceans under the polar caps are full of life happy as pigs in mud. Thermal vents have complex life forms around them. Plant seeds and fungal spores might survive long periods of freezing. Hot water springs might even provide small biomes for fresh water aquatic life. I don't think we'd have to go back all the way to single cellular life after such a period, but your garden variety mammals would definitely be out of the picture for a while :s When it comes to human-like intelligent life though, who knows. I certainly believe we would try. We can create energy from the sun, wind, geothermal, plenty of energy to create our own biomes. Food would be an issue, it would all have to come from hydroponic gardens (lab grown meat?). If it happened 'right now' we'd be in trouble but 100 years, 200 years from now? I think it would still beat living on Mars To tie it all back to the original question, I think it would be unlikely for complex life to evolve and thrive on a desert planet. Once it's started on a planet to the extent it has on present day earth however, I can certainly see it surviving their planet turning into a desert, especially if it's the space-faring type of life from sci-fi books and movies rather than just microbes or 'cow and chicken'.

Titan has lakes, rivers and clouds, they're just not made of water but of methane. Although rain was not directly observed AFAIK, if there are clouds, rivers and lakes it stands to reason there's a rain cycle involved. On Titan, the 'ground' is mostly made of water ice, the methane cycle plays on top of that. Venus of course has clouds. It also has a rain cycle, although the general consensus is it never reaches the surface in liquid form. However since there have been suggestions about life in Venus' atmosphere I didn't want to outright group it with desert worlds. Its atmosphere is so dense and material-rich you could argue its a biome by itself where life could conceivably persist and perhaps even originate. But looking purely at the surface you could certainly argue its a desert world, it doesn't change the odds all that much The gas and ice giants are just nasty. As beautiful as Clarke could make it sound, I don't think there are ever stable enough conditions for life to get a foothold. It's not that the materials are not there, but its all so turbulent that if you were to 'inject' some form of life that could survive in the local conditions where you injected it, it wouldn't take more than a day for it to end up in conditions that would outright kill it.

But erosion doesn't limit itself to the top of mountains, quite the opposite in fact. The further you go down a slope the more water and debris from higher up will stream over it. It would just eat away at the slopes and the tops would collapse as the slopes became to steep to support their integrity. You would need some active process to 'top off' the mountains and slopes to combat this. On earth mountains form due to plate tectonics and volcanic activity, those processes require a molten core which would cause your body to become spherical. A totally rigid body would just wear down, it would have no active geological processes to keep its shape.

Earth has technically been a desert world at several periods in its past (after the start of life). There are a couple of definitions of a 'desert'. The biological one is typically centered around the hostility to life. Needless to say if you take this definition it would be unlikely as the definition itself is specifically centered around "hostility to life". The geological one typically mentions the lack of precipitation caused by extreme heat or cold and/or the absence of abundant surface water. By this definition, Antarctica is a desert, and the entire Earth was a desert planet the few times in its past when it froze over completely. Of course life was quite simple during those times and it's possible biogenesis couldn't occur on such a world, but once life gets a foothold it is very good at hanging on. We have a considerably large sample of planets and moons in our solar system. Virtually all of them are desert worlds. As far as we know only one of them carries life, I'd say it can't be a coincidence that this is also one of the very few rocky bodies that isn't a desert world. The only other ones I can think of are Venus and Titan. The idea that you need a world with water on it to have life isn't based on a sample of just 1, it is based on a single positive in a large sample of different worlds. Of course the final word on whether there's microbial life elsewhere in the solar system isn't out yet, we still have quite some sub-surface work to do to be certain, but so far the results are pretty bleak. The universe at large doesn't seem to be very kind to life.

Don't shoot the messenger, but... https://solarsystem.nasa.gov/planets/in-depth/ So regardless of how it came to be, or if it once started out as a natural planet, once you make/magic this thing, it is not technically a planet anymore... It would have to be fairly light to stay in its 'sculpted' shape, and any sort of atmosphere or surface water would wear down the sharp edges within no time (geologically speaking) and fill up the 'valleys' with sediment quickly (valley being the center of the polygon). If you want a KSP example look no further than Gilly, although not nearly as regularly shaped as a Pythagorean solid you can imagine it being more regularly shaped and standing on the surface of it wouldn't be all that different. You'd effectively have 2 'biomes', the low lands and the high lands, with an arbitrary cut-off point somewhere in between. As we all know, when it comes to launching a rocket from Gilly it really isn't worth it to stumble/bounce yourself to a high point first, the gravity is so low on such non-spherical bodies that you'd just pretty much jump off into space. For the heck of it let's say we have a planet sized body made out of nanobots that actively kept themselves in such a shape (and we disregard the enormous amounts of waste heat of all the work needed to fight gravity, which I have no doubt would melt the entire thing). I think the interesting thing about it would just be to walk from the center of a polygon to its edge. You'd be walking on a perfectly flat surface, as far as the eye could see, yet with every step you took away from the center of the polygon it would feel like you're walking up a steeper and steeper incline. I think it would be very disorienting, possibly nausea inducing... but only if the body was small enough to actually notice a difference in the direction of gravity after a short distance. I think that's kinda the problem with the idea. If the body is so big it has enough gravity for normal surface travel, then it is probably also big enough for local differences in gravity to be unnoticeable at typical surface traveling speeds. If OTOH the body is small enough to notice the gravity shift over short distances, then its gravity would be so low that surface movement was just a series of ballistic trajectories (like 'driving' on Gilly or even walking on Minmus) and it probably wouldn't bother your sense of balance and direction any more than being in free fall would. Note on Donut-shaped planets, Sixty Symbols did an episode about that:

The Otrag ( http://www.astronautix.com/o/otrag.html ) was designed to use parallel staging, making it look a lot like a KSP asparagus creation, however afaik it was never intended to pump fuel between the stages. Although its engines racked up an impressive 1 million plus seconds of static firing and there were over a dozen successful test launches, the project was eventually cancelled. It was meant to have its stages in concentric squares so that each square further out would have enough trust to lift the whole thing. Once the outermost square of boosters was discarded, the next square would take over and the staging would work its way to the inner core like that. The way it would have discarded its stages would have made it at least appear very much like a KSP asparagus staged rocket.

Web is mooning the MAZ: "After several months of discussions, NASA optics and micrometeoroid experts working on the James Webb Space Telescope have figured out how to reduce micrometeor damage to the $10 billion machine: turn it around." https://www.theregister.com/2022/11/21/nasas_jwst_meteor_avoidance_plan/

I think you're missing the extent to which this research goes. Phrases like "blocking the sun" is exactly the kind of rhetoric that is used to scare politicians into blocking research, and it's complete nonsense. Nobody is blocking the sun, we're talking about small scale research into regulating the amount of sunlight that reaches the surface or the atmosphere of the earth. The particular project that scared the UN into this treaty in 2010 was a proposal by NASA to do some small scale experiments with reflective dust in low earth orbit. It would have had zero effect on the global climate, it would have been a short duration experiment, and it would have given us a lot of useful data, not only about how effective (or ineffective) such measures could potentially be but also on the effect of sunlight on cloud formation and wind patterns. I don't subscribe to the notion that simply 'bettering our ways' with regards to pollution is going to save us. All the data we have says that it most definitely will not. And it irks me greatly that people keep pushing that nonsense. We're way to far down the slope to just 'stop being bad' for the environment. The amount of damage we have already done requires active regulation to solve, reducing our climate footprint can only prevent future damage, not repair past damage. Until people start realizing this, we will keep sliding down the slope until we hit the bottom hard enough to form a crater. Edit: It is worth considering that the situation we find ourselves in is in itself the result of large scale global geoengineering, albeit unintentional, and without knowledge. Research into actively altering the climate stands to also give us a lot of knowledge in how to prevent altering it unintentionally.

I suspect there will be plenty of "our song" entries to this thread eventually, so as a committed bachelor I'll throw in mine for a bit of variation I fell in love with Tom Waits in the late 80s and have been following him ever since. Unfortunately he retired some years ago, but he left a legacy of around 2 dozen albums, all of which I own, many on multiple media formats. I was fortunate enough to see him live in 1999 in the amazing setting of the Royal Opera House in The Hague, one of the best concerts I have ever seen. There are many songs of his that resonate with me, but this one I definitely count as a personal 'anthem':

Thanks to the ban on research, we don't have reliable data to make that assertion. What is stupid is acting without knowledge, and by extension blocking the gathering of said knowledge. Given the fact that a) all stars are variable, even stable ones like our sun, and b) our civilization requires stability to survive, it seems only inevitable that we will eventually start regulating the amount of energy the earth receives from the sun. Better we know how to do that safely before we actually start doing it.