StrandedonEarth Posted March 13 Share Posted March 13 1 hour ago, Minmus Taster said: Holy s**t! The ones that are only a few km across should probably only be classified as captured asteroids. To be called a moon, it should be big enough to be spherical. IIRC that requires a diameter of about 100km… Quote Link to comment Share on other sites More sharing options...
Minmus Taster Posted March 13 Share Posted March 13 30 minutes ago, StrandedonEarth said: The ones that are only a few km across should probably only be classified as captured asteroids. To be called a moon, it should be big enough to be spherical. IIRC that requires a diameter of about 100km… Or we could differentiate major and minor satellites, we already do to an extent but we could create an updated definition similar to how we changed the criteria for planets vs. dwarf planets. I don't see why a satellite needs to be spherical to be considered a moon, that would exclude Phobos and Deimos along with several larger objects, like Proteus or Phoebe. Perhaps major moons could be the ones which dominate the space around a planet (such as the Galilean moons) vs objects which are dominated. Quote Link to comment Share on other sites More sharing options...
Terwin Posted March 13 Share Posted March 13 (edited) It is not hoarding if you have a legitimate need. Those rings are transitory, and Saturn needs those moons to capture and process fresh asteroids to replenish them. It is probably not reasonable to count the asteroids currently being processed into ring-fodder as moons however. Edited March 13 by Terwin Quote Link to comment Share on other sites More sharing options...
darthgently Posted March 13 Share Posted March 13 All I know is that if Pluto can’t be a planet then maybe some rocks orbiting planets shouldn’t be moons. Fair is fair. Dwarf moons? Quote Link to comment Share on other sites More sharing options...
Minmus Taster Posted March 13 Share Posted March 13 23 minutes ago, darthgently said: All I know is that if Pluto can’t be a planet then maybe some rocks orbiting planets shouldn’t be moons. Fair is fair. Dwarf moons? Fair has nothing to do with it, can't hurt a planets feelings, only peoples. This is merely a matter of arbitrary classification. Quote Link to comment Share on other sites More sharing options...
darthgently Posted March 13 Share Posted March 13 27 minutes ago, Minmus Taster said: Fair has nothing to do with it, can't hurt a planets feelings, only peoples. This is merely a matter of arbitrary classification. Lol Quote Link to comment Share on other sites More sharing options...
darthgently Posted March 13 Share Posted March 13 If Pluto were a planet, it would be the only planet in the Sol system with a moon whose barycenter was outside the parent body. So if any moon has a claim on being an unqualified moon it would be Charon. Or Pluto-Charon is a dwarf planet binary system? Pluto is a bit of a platypus. Quote Link to comment Share on other sites More sharing options...
Hum_bug Posted March 20 Share Posted March 20 BBC News - Dark Energy experiment challenges Einstein's theory of Universe https://www.bbc.com/news/articles/c4geldjjge0o Not a discovery yet but some scientists are getting excited Quote Link to comment Share on other sites More sharing options...
magnemoe Posted March 20 Share Posted March 20 On 3/13/2025 at 8:37 PM, darthgently said: All I know is that if Pluto can’t be a planet then maybe some rocks orbiting planets shouldn’t be moons. Fair is fair. Dwarf moons? Who is an fair question, Saturn is up to over 100 moons now and it will be many more once we get multiple probes in orbits, stuff down to meter size. So it need to be an cutoff size or all the particles in the ring is an moon Quote Link to comment Share on other sites More sharing options...
darthgently Posted March 20 Share Posted March 20 1 hour ago, magnemoe said: Who is an fair question, Saturn is up to over 100 moons now and it will be many more once we get multiple probes in orbits, stuff down to meter size. So it need to be an cutoff size or all the particles in the ring is an moon Some rough criteria: Definitely a moon: Big enough for a crewed lander to land on and enough gravity to drive a manned buggy around on. This will require crewed missions to many rocks to determine their moon status Probably not a moon: If an astronaut can jump into space from the surface, probably not a moon. If the rock moves more than the human when jumping into space zero percent chance of moonhood Quote Link to comment Share on other sites More sharing options...
JoeSchmuckatelli Posted March 21 Author Share Posted March 21 More 'dark energy' weirdness. Expansion rate not constant. Um. Lambda? "... data from the powerful Dark Energy Spectroscopic Instrument (DESI) add more evidence that the universe’s expansion accelerated faster in the past than it is doing now. DESI’s picture of “dynamical dark energy” will both delight and confound theorists, who have despaired at the lack of clues to dark energy’s physical cause but were not expecting what DESI is now seeing." https://www.science.org/content/article/mystery-force-behind-universe-s-accelerating-expansion-may-not-be-so-constant-after-all Quote Link to comment Share on other sites More sharing options...
darthgently Posted March 21 Share Posted March 21 (edited) 11 hours ago, JoeSchmuckatelli said: More 'dark energy' weirdness. Expansion rate not constant. Um. Lambda? "... data from the powerful Dark Energy Spectroscopic Instrument (DESI) add more evidence that the universe’s expansion accelerated faster in the past than it is doing now. DESI’s picture of “dynamical dark energy” will both delight and confound theorists, who have despaired at the lack of clues to dark energy’s physical cause but were not expecting what DESI is now seeing." https://www.science.org/content/article/mystery-force-behind-universe-s-accelerating-expansion-may-not-be-so-constant-after-all The angle that apparent expansion acceleration is caused by gravity induced time dilation that came up lately makes intuitive sense. It would certainly vary as mass distribution altered over time. Basically, as I understand it, time goes faster in emptier space so there is more expansion there. Not saying I truly understand it though Edited March 21 by darthgently Corrected expansion to apparent expansion acceleration Quote Link to comment Share on other sites More sharing options...
Deddly Posted March 21 Share Posted March 21 Quote Link to comment Share on other sites More sharing options...
AckSed Posted March 23 Share Posted March 23 https://www.universetoday.com/articles/the-worlds-oldest-impact-crater-has-been-found-in-australia 3.5 billion years ago; the Earth was barely a billion years old then, with a reducing atmosphere, and any life was aerobic. The reason it was searched for is as interesting: to find evidence for a theory that early impacts literally drove plate tectonics and made the starts of continents, maybe even extra heat for life. Quote Link to comment Share on other sites More sharing options...
AckSed Posted March 27 Share Posted March 27 PV Magazine is the last place I expected to find a discussion of a Dyson Sphere, but a German photovoltaic researcher studied a theoretical Dyson sphere made of nothing but PV cells by treating it as a "grey body" and came up with some unusual numbers. As Randall Munroe has said, one of the fun things about mathematics is that you can make the numbers bigger and no-one can stop you. tl;dr full coverage would become too damn hot for the PV (and for the Earth) to work at 1 AU, so you have to build smaller, and further out, and the numbers are still ridiculous: Quote [A] partial Dyson Sphere with a 2.13 AU radius, on which solar cells cover 22% of the sphere’s surface, would require 1.3 × 1023 kg of silicon. This partial sphere would raise Earth's temperature by less than 3K. Obtaining this amount of material, roughly the estimated silicon content of Mars, would still require planetary-scale mining but is at least within the realm of possibility using resources from terrestrial planets. If this Dyson Sphere operated at 85% of its theoretical efficiency limit, it could convert 4% of the sun's 3.9 × 1026 W luminosity into electricity, generating 15.6 YW. This would be enough energy to power interstellar spaceflight, providing the energy to accelerate a 1000-ton mass to 0.9c in just 7.5 ms. Additionally, the Dyson Sphere would produce far more energy than needed for terraforming projects. The energy required to vapourise Mars' CO2 polar cap (120–1000 MW-years or 1.1–8.8 TWh) would be generated in just 0.25–2 ns. Quote Link to comment Share on other sites More sharing options...
darthgently Posted March 27 Share Posted March 27 (edited) Not sure where to put this so here it goes Edited March 27 by darthgently Quote Link to comment Share on other sites More sharing options...
JoeSchmuckatelli Posted March 28 Author Share Posted March 28 Good for them! Quote Link to comment Share on other sites More sharing options...
AckSed Posted March 28 Share Posted March 28 I have not seen an article that sounded so much like technobabble before. It isn't, though. What it is is almost as unbelievable: a circuit using magnetic quasiparticles inside artificial garnet and formed by the amazingly-named "omega grid", and a genetic algorithm to inverse-design backwards from whatever component they want this circuit to simulate being. https://spectrum.ieee.org/custom-electronics-with-magnons So far they've had it act like a notch filter and a demultiplexer, but it could theoretically act like any component, and the current micro-scale circuit can store each configuration (in a separate personal computer) and switch between them in less than a second. Quote Link to comment Share on other sites More sharing options...
darthgently Posted March 28 Share Posted March 28 Not sure if a full black swan, but this will disrupt the compute and related markets like a benestrophic earthquake if it pans out. Catastrophic for some players certainly 34 minutes ago, AckSed said: I have not seen an article that sounded so much like technobabble before. It isn't, though. What it is is almost as unbelievable: a circuit using magnetic quasiparticles inside artificial garnet and formed by the amazingly-named "omega grid", and a genetic algorithm to inverse-design backwards from whatever component they want this circuit to simulate being. https://spectrum.ieee.org/custom-electronics-with-magnons So far they've had it act like a notch filter and a demultiplexer, but it could theoretically act like any component, and the current micro-scale circuit can store each configuration (in a separate personal computer) and switch between them in less than a second. Wow. It’s like the Moteys from Niven’s and Pournelle’s The Mote in God’s Eye made chips in their own image Quote Link to comment Share on other sites More sharing options...
JoeSchmuckatelli Posted Friday at 06:37 PM Author Share Posted Friday at 06:37 PM Isolated population living in the Sahara when it was wet and savanna like discovered. https://www.reuters.com/business/environment/sahara-desert-once-lush-green-was-home-mysterious-human-lineage-2025-04-04/ "... the Green Sahara people carried only trace amounts of Neanderthal DNA, illustrating that they had scant contact with outside populations. Although the Takarkori population itself disappeared around 5,000 years ago when the African Humid Period ended and the desert returned, traces of their ancestry persist among various North African groups today... " Quote Link to comment Share on other sites More sharing options...
darthgently Posted Saturday at 10:41 PM Share Posted Saturday at 10:41 PM Quote Link to comment Share on other sites More sharing options...
StrandedonEarth Posted Saturday at 11:09 PM Share Posted Saturday at 11:09 PM 15 minutes ago, darthgently said: That reminds me of an aurora I saw with friends while camping during the summer. It wasn’t as spectacular as some, just a green pulsing across the sky, covering around seventy percent of the sky. Just happily drunk, laying back on the middle of an abandoned road (a chunk of the old highway from before it was buried under the Hope Slide), watching meteors, satellites, and an eerie faint green sheet pulsing across the sky, with just the occasional howl of a car bulling through the air on the distant highway. Quote Link to comment Share on other sites More sharing options...
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