@DrPhiltill's Threads
I want to share a few pictures of the Kurdish children. My friend David Evans of Scotland regularly goes into Kurdish areas to organize “Space Days” to give the youth hope in the midst of endless war. I participated only remotely (by Skype) in this, but oh how moving! .../1
2/ David organizes these to have space scientists speak and answer questions with the older youth via Skype while teachers translate. David gives Space Bears to the younger children. ❤️😭❤️😭 
They have security issues because the Space Day events themselves become potential targets in the fighting. There are power outages and other logistical problems. David reports that the children are deeply moved.
@albiondumsday @Phil_9000 @esa No, I didn’t. I will have to go back and watch that to see the details!
By the way, it super annoys me that the illumination angle on the top of the lander (where landing pad lighting doesn’t disguise the sun’s angle) doesn’t match the illumination angle on the Earth. 🤷♂️🤦♂️
By the way, it super annoys me that the illumination angle on the top of the lander (where landing pad lighting doesn’t disguise the sun’s angle) doesn’t match the illumination angle on the Earth. 🤷♂️🤦♂️
@albiondumsday @Phil_9000 @esa Also, dust doesn’t billow like that in lunar vacuum. It shoots straight away into the distance at super high velocity at an angle low to the ground. There is no air to hold it up above the ground in billowing clouds.
@albiondumsday @Phil_9000 @esa Here’s the clip. The final few seconds shows the completely unrealistic billowing dust. But still, it is a thing of beauty with the waltz music. I love it.
Output from the “Extraction - Creating Value” session. #SpaceResWeek
About that ^^^ idea of re-using slag from terrestrial mines: the tech for lunar mining will be perfect for this, since it will be adapted to using crushed rock (like lunar regolith) of ordinary minerals (not concentrated ore) so this could solve a major enviro challenge.
And here are the recommendations from the Extraction breakout session. This provoked an argument since someone said the tech isn’t ready but others disagreed. In fact, I got to see the field test of these technologies in 2012. They *are* ready. #SpaceResWeek
Recommendations from the “Investment & Financial Planning” breakout session. (I wasn’t in the room so I can’t answer specific questions about this 😅)
Recommendations from the “Role of Government and Regulators” breakout session. IMO, if government took on a *greater* leadership role it could help us get beyond the limit of a single planet *sooner*, with immeasurable benefit for humanity & the Earth. #SpaceResWeek
Output from the “Prospecting - Proving Value” breakout session. Responding to these points, this one way that @NASA, @esa, and other national space agencies will play a major role securing the future health of humanity & the planet: by prospecting space resources. #SpaceResWeek
It’s a great point 👍, but there is a solution! The key is to bootstrap the industry in space building it a little at a time using resources that are already in space. Here’s a paper I wrote about how this can be done. ascelibrary.org/doi/abs/10.106…
2/3 For a version of that paper that is not behind a paywall, you can download it here: arxiv.org/pdf/1612.03238…
3/3 For a 3-part story where @howellspace interviewed me on this “bootstrapping” concept, here is part one. (Follow the links at the bottom for parts 2 and 3.) If we can convince policy makers to pursue it, I think it will greatly benefit our world.🌎🚀 universetoday.com/115926/buildin…
There's an unexpected connection to planetary science here. The exponential growth of Moore's Law has been consistent for so many decades, it demands an explanation. As John Nash was represented in "A Beautiful Mind" saying, "I need to look through to the governing dynamics." /1
2/ *Something* must be at work to cause this to have the *same* exponential rate for so many decades. To be this consistent, it can't be random. But what is at work? The mathematically obvious (but inadequate) answer is this equation. It predicts exponential growth whenever...
3/...whenever something reinforces itself. When the rate of growth of something is proportional to how much of it already exists, then it will grow exponentially. Like bacteria multiplying in sugar water. The more there are, the faster they reproduce. This is simple, but....
At least two folks pointed out this effect, which cools the air before it crosses the hand. Great point! And by the way, this effect was crucial for landing the Viking spacecraft on Mars.../1
2/ Research showed the rocket exhaust during Viking’s landing would blow too much soil and make too large craters. Since Viking had no rover, it would be unable to get away from those craters, and that would mess up the science. (Mock-up with Carl Sagan, here)
3/ So to reduce this effect they replaced the engine nozzles with these “showerhead” nozzles. These would create lots of smaller jets instead of one large jet per engine.
This girl has so many interesting physics ideas tonight. I have NEVER noticed this one and yet it is AWESOME!
If you blow on your hand with your lips pursed the breath feels cool, but with your lips open the breath feels hot. Anybody want to guess why? Try it!
If you blow on your hand with your lips pursed the breath feels cool, but with your lips open the breath feels hot. Anybody want to guess why? Try it!
At first I was tempted to think the breath cools down the same way rocket exhaust cools down as it squirts out the combustion chamber then speeds up in the rocket nozzle, but it can’t possibly be that because the kinetic energy of your breath is tiny compared to rocket exhaust.😂
3/ The rocket propellant burns in the combustion chamber on the left—very hot—then goes through the “throat” where it “chokes” at the speed of sound. Then it moves down the diverging nozzle on the right where it speeds up to supersonic speeds and cools down. (M is Mach number.)
My daughter asked why this motion starts with palm up but ends with palm down? HOW DOES THIS WORK? Why does it turn your hand over? And how can your arm move like this? 😅 There’s actually an answer for this in MATHEMATICS of all places. (Short thread) /1
2/ Math is amazing and can be used for just about anything. In this case we are asking about the rotation of solid objects. Each part of your arm has a location in three dimensions (x, y, z). In math, a list of numbers like this called a vector. (Credit: en.m.wikipedia.org/wiki/Euclidean…)
3/ When you rotate your arm, the position of the top part of your hand ends up different than it was at first. The same for almost every part of your arm. So the (x,y,z) values change for almost every part of your arm. We can mathematically change them all with 1 simple equation:
1/Since Elon Musk named his barges after Starship/Minds of the Culture series I am reading the series. The ideas of post-scarcity using space resources & artificial intelligence/robotics are right on, but I do NOT like the Orbitals people live in.(Credit: en.m.wikipedia.org/wiki/Orbital_(…)
2/ In the stories these orbitals are as wide in the short direction as the diameter of a planet so they hold vastly more people than a planet. Architects work with the AIs to design their geology: mountains, rivers... I didn’t realize I would dislike it until I read the stories.
3/ While reading about people living in these engineered worlds I kept feeling an entire dimension of our existence was missing. I realized it is the wildness of our planet. We get to discover it, and we fight to survive in it, but we didn’t make it and we don’t control it.
Good advice. Let’s say the cabin was pressurized at Sea Level then landed at Denver resulting in a pressure difference of 2.47 psi, over a doorway 6 feet high and 3 feet wide that results in 3 tons of force. Dang.
Gotta love airplane signage. Don’t smoke, but put cigarettes here. (Better than hiding them in the waste bin where they’ll light the paper towels on fire 😅)
I assume this isn’t like Star Wars where you can shoot a vent pipe and the entire Death Star freaking explodes.
By the way, here‘s another super-cool thing about this picture. Notice how the concrete on the Space Shuttle launch pad is disrupted? It wasn’t that way before the Shuttle launched. What caused it? The NOISE of the launch busted the concrete. /1
2/ What really happened was that NASA built the landing pad during the Apollo program by dredging the silty sand from the swamps on Cape Canaveral. They piled up the sand and put concrete slabs over it. That sand does NOT have great geotechnical properties, but it was available.
3/ The launch pads were later converted from Apollo to the Shuttle program. The Space Shuttle made so much vibration (i.e., noise) that it shook the entire pad including the sand underneath the pad. That caused the sand to slowly slump and slide downhill under the concrete slabs.
You’ve gotta love space art! I think this NASA artwork is telling what NASA plans to do 100 years from now (not FY20!), since it will be 100 years before the Moon looks like this. I mean—obviously—the Moon in this picture has a very thick atmosphere. We can tell because.../1
2/...the rocket exhaust is in a narrow column and it is emitting yellow light. Rocket exhausts look that way on Earth in our thick atmosphere, but on the Moon (like it is today) with no atmosphere the rocket exhaust spreads out to fill the entire hemisphere beneath the lander...
3/Because it spreads out so much, that means it gets very cool. The low temperature means that chemical reactions can’t occur any more, so it doesn’t produce light. And the gas molecules aren’t colliding so much that they vibrate then give off the vibration energy as light. So...
In general I agree: buying commercial is vastly better when possible because the gigantic consumer market creates better products than the super-limited government aerospace market. However, this robot uses pneumatic actuation—not good for the space environment. We need electric!
2/Researchers at @Caltech are building 100% electrically-actuated walking robots. It’s much harder than using pneumatics, because pneumatics give the joints a natural “compliance” like tendons & muscles. Electric motors don’t provide it, so software must be written to compensate.
3/ So far there aren’t any commercial companies building 100% electric walking robots. They use pneumatics instead because it is easier. This is why NASA has to take it on itself to drive that technology. This is a case where NASA can’t rely on the gigantic commercial market.
I LOVE the message of space resources, but I notice a few HORRIFYING things in the picture😉 First, the crater is a complex crater, not a simple crater, because it is multi-ringed & has a flat floor & a central uplift peak. These features only happen in craters bigger than 20 km.
2/ Compare the simple crater on the very bottom left edge of the picture. Simple craters are bowl-shaped with a single rim. They form when the crater is smaller than 20 km diameter. The complex crater is HORRIFYING because it provides a size scale to compare the footprints 😉
3/ Therefore we can tell that each footprint is more 20 km long. Therefore, these are not human footprints. These are GIANT extraterrestrial space invader footprints. This is a little distracting from the message of mining the Moon, since it implies we will have to fight giants.
@SB_AlphaCephei @cosmos4u @JoeWBowles Exactly, so it is important to understand WHY the definition was changed in the 1600s. They switched from a dynamical definition to geophysical because it promoted what was found to be the most important aspect of our solar system: that there exist other bodies like Earth. /1
@SB_AlphaCephei @cosmos4u @JoeWBowles 2/ When we examine how & why that happened we see it was NOT redefined from geocentric to heliocentric. That aspect was important but was NOT considered most important, because they realized these bodies don’t all orbit the Sun, but they are all geophysical so it unified physics.
@SB_AlphaCephei @cosmos4u @JoeWBowles 3/ They used to believe there were two separate physics: one for the heavens and another for the earth (“geophysics”). The heavens were inviolable & perfect while Earth was imperfect & changing but controlled by the heavens (hence astrology).
I bounced this off my colleagues & they didn’t like it, but FWIW: if the 100s of planets in our solar system are divided into 2 groups based on what planet growth stage they experienced, you get 11 in the top group (the oligarchs). Ceres is out, but Pluto, Eris & Triton are in./1
2/ The oligarchs of our solar system are: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, Pluto, Eris, and Triton. The other dwarf planets are all protoplanets (never were in oligarchic growth). Triton was an oligarch before being captured as a moon of Neptune.
3/ We don’t know if Triton formed closer or farther from the Sun than Pluto, so we don’t know where it goes on this list. We can leave it off the list entirely since it is no longer a primary (I.e., sun-orbiting) planet. Or it can be appended on the end? Or tied with Pluto as #9?
That brown dust blown by Starhopper is silt that was washed from the US Great Plains & Midwest down the Mississippi River then pushed by shore currents in the Gulf of Mexico along the coast of Texas to Boca Chica. Such transport processes don’t exist on the Moon. As a result.../1
2/...the lunar soil is “unsorted”, meaning that all the different sized particles are mixed together. The dust or silt-sized particles are mixed in bulk with sand, gravel, and rocks.
3/ We spent a long time trying to figure out which sizes of lunar soil get blown by a landing rocket. (Like in this view out the Lunar Module window in Apollo 15). We finally showed that all sizes are being lifted into the gas. For example...
Fun fact: “Protoplanet” literally translates to “first planet” or “primitive planet”. They are the first set of planets that formed in the solar system. Vesta, the 2nd largest asteroid, is believed to be a surviving protoplanet, but it is no longer round due to collisions. /1
2/ In the early solar nebula before there were any planets, dust grains joined together and grew slowly into planetesimals. It takes maybe a million years to get planetesimals about 1 km in diameter.
3/ After reaching about 1 km in size, their gravity is big enough to pull in the dust grains faster, so runaway growth begins. After about 10 million years, the planetesimals (icy ones in the Kuiper Belt) may reach, say, 300 km diameter. Then a different growth phase begins...
I strongly suspect this video is so cool because of the Nyquist-Shannon Sampling Theorem. What is that? I’m glad you asked! 🤓 1/N
2/ The theorem says (very loosely) that when you convert an image of a real object into a digitized signal, the digital samples have to occur at least twice as fast as the fastest thing happening in the real object. This is standard nerdism in engineering. en.m.wikipedia.org/wiki/Nyquist–S…
3/ A millipede is a real object. A video is a digitized signal. So if anything in the millipede is happening faster than the frames of the video (divided by two) then something BAD can happen. This bad thing is called... Aliasing! en.m.wikipedia.org/wiki/Nyquist–S…
I'm reading old sources to understand how & why moons have (always) been classed as a type of planet, how culture forgot this, and how culture intruded in science. Here's an interesting text on the types of planets from an 1897 textbook (Advanced Physiography by John Thornton.)
BTW, if wants to help the research and can translate Latin to English (better than Google Translate😭), this chapter 16 of Philosophia Naturalis, written in 1651 by Johannes Phocylides Holwarda, tells crucially how the "planet" taxon changed in the immediate wake of Galileo. 1/2
2/2 Here's a small sample showing how hard it is to translate texts similar to this one using automated methods. First, parts of the font don't copy-and-past correctly. Second, after fixing those by hand (as best I can), the automated translation is unreadable. Ackkkk!
Granular physics is awesome because non-intuitive macroscopic behaviors appear as the result of sand-grain-sized (mesoscopic) interactions. The existence of grain-scale physics makes granular matter different than ordinary continuum matter (solid, liquid, or gas). HT @IanMolony
2/ When I did my doctoral work in the physics of granular materials, this sort of non-intuitive sand experiment was all the rage. This particular experiment is new, demonstrating that there are still surprises to discover in physics!
3/ For another example of freakishly amazing granular physics, check out the three short clips of water drops landing in sand, here: pnas.org/content/112/2/…
I’ve resisted commenting on the tardigrades that crashed on the Moon, but this may be interesting so here goes. Fossil tardigrades have been found in 530 million year old rock. That means they have lived here during some large asteroid impacts. They live all over Earth and... /1
2/ I would guess that almost certainly they have been blown into space by some of these impacts. Around an impact there is a region called the “spallation zone” where the rocks are shocked only lightly and yet ejected all the way into space. The tardigrades in those rocks...
3/...would likely not be too mangled, maybe even survived, and yet they would be blown into space. Since the Moon is *right there*, a lot of these rocks and the tardigrades and other life would land on the Moon. So tardigrades have probably landed on the Moon before. However,...
Something I’m been thinking aboutf: the current lunar plans will be better if Lunar Gateway is given into propellant depot abilities. Each lunar landing will require four launches from Earth, two of them loads of propellant to refuel the 1st and 3rd stages of the lunar lander. /1
2/ So there is already going to be a lot of docking and zero-g propellant transfer at Gateway, anyway. Coordinating the timing of four successful Earth launches each time will be hard (including the humans in Orion and the non-reusable 2nd stage of the lander each time), but...
3/ it will be easier if Gateway has surge & storage capability for propellant. That would remove from the critical path of each lunar landing the 2 commercial launches of propellant along with their docking operations at Gateway. That’s big if even just 1 contingency is avoided.
