I'm by no means a dinosaur expert, but I'd consider myself an enthusiast.

My favorite is the Carnotaurus. It's not quite as big as the classic T-Rex and has even tinier arms, but dude had bull horns on its noggin! And it'll still chase you down and gobble you up.

Everybody's got a favorite. And if you don't, find your poor lost inner child and ask them;

What's your favorite Dinosaur?

Hey everyone,

As a few of you may know, there was a paper released a few days ago claiming that an Room-Temperature Ambient-Pressure Superconductor (RTAPS) was created. You can see the original paper here: https://arxiv.org/abs/2307.12008

To bring things into perspective if this holds true we would likely dispense with energy and transportation concerns. It would be akin to the discovery of fire, penicillin or the transistor. A groundbreaking change. See here for a more detailed, bullish list of things it can help with: https://nitter.net/Andercot/status/1685088625187495936

There are many communities that are discussing this. The best summary I was able to find is here: https://forums.spacebattles.com/threads/claims-of-room-temperature-and-ambient-pressure-superconductor.1106083/page-17

There is still a very much active debate there (and elsewhere online) of people on the viability of the original people. Many are pessimistic that the evidence is scant and that the original publication does not hold its water. An interesting summary of the sentiment of a part of the community can be found through the (faux) betting market of Manifold here: https://manifold.markets/QuantumObserver/will-the-lk99-room-temp-ambient-pre

On the link above they are also diligently tracking any replication attempts. Currently we are at the stage were theoretical simulations have validated the possibility of the purported materials to be superconductors (https://arxiv.org/abs/2307.16892).

Finally, a nice replication attempt that tried to make the creation process better and demonstrated some of the effects required to prove superconductivity (scroll up): https://twitter.com/iris_IGB/status/1685804254718459904

This is very exciting, because even if some properties are valid, it gives a mjor boost to the whole field.

Ok ok disclaimer, I am a cosmology PhD candidate, don’t have the degree yet. However I do feel comfortable at this point calling myself a cosmologist (I think for the first time ever). In any case, with all the new people here, I think an AMA might be fun. I will try my best to answer all of the questions I get asked, but it may not happen quickly!

A bit about my research. I study the conditions in the early universe, specifically when the cosmic microwave background was forming, and I use CMB data to test our understanding of this era. The CMB formed roughly 300,000 years after the big bang, when the universe was 1/1000th its current size. The patterns that we see in the temperature fluctuations of the CMB can tell us a lot about the universe at this early time, and specifically we can try to use them to see if anything ‘unexpected’ happened at this time, like a hitherto undiscovered particle annihilating into ‘normal’ particles (for example).

Ask me anything about the early universe, or physics writ large, and I will do my best to answer!

I'm a big fan of nuclear fusion as a concept and hope to shift toward doing active research in the field at some point.

I'd like to open this discussion to talk about topics regarding nuclear fusion as a future energy source. To start, I'll lost a couple of ongoing fusion efforts I'm familiar with.

ITER:Of course the biggest fusion project is ITER, the massive multinational collaboration which is building a massive tokamak reactor in France. Unfortunately ITER will never produce power for average people, as it's purely a test reactor with no plans to be connected to the grid. The following effort to build a functional grid connected reactor, DEMO, isn't set to be built until at least 2050. This has resulted in a considerable number of private ventures trying iut experimental alternative approaches.

HELION:At the time of writing this, there's quite a bit of buzz surrounding Helion energy, both because of the ambitious timeline theyve recently proposed as well as the investment of Sam Altman of OpenAI fame. Helion uses an FRC topology, which I personally think is a really cool idea. Basically it's a tokamak without the physical shell around it, and is kept sustained by the internal plasma physics. Helion also has another interesting quirk, they are not pursuing the typical DT fuel strategy, but are instead planning to use DD fusion to breed He3 and use DHe3 fusion as the primary energy source. I think this is a good idea because DHe3 fusion is "aneutronic", whereas DT fusion produces high energy neutrons that are somewhat of an unsolved problem to deal with. I wonder though, how they intend to deal with the inevitable tritium pollution that DD fusion creates, and how they will separate that out before Iit creates neutrons anyway.

TRIALPHA:In addition, another major company TriAlpha Energy, also pursued FRCs, hoping to use an alternative proton-boron11 mix to achieve aneutronic operation. I think they've sort of pivoted toward being more a neutron source than working toward breakeven.

HB11: A recent proposed approach is HB11, which is also going for proton-boron fusion. Now with Tri Alpha this seemed really dubious, because hydrogen boron has a much lower cross section for fusion than other options, even the DHe3 that Helion is doing. In addition, boron has way more electrons than hydrogen, so a proton boron plasma has more electrons with causes more bremsstrahlung loss. HB11, however, thinks they can overcome this through high energy laser acceleration. They want to use a high power laser to shoot a fuel pellet into a target. This supposedly will work much better than heating the stuff, because the laser will impart a specific impulse and thus the thermal spectrum of the impact will have a much higher Q factor centered around the cross sectional peak. I'm not really convinced on this, just because I feel like that thermal spectrum would only last for the first few atomic layers of impact before it doesn't really matter amymore.

CFS: The next option I would consider to be one if the most popular fusion startups is Commonwealth Fusion Systems. They have what I'd consider the most conservative approach, they are attempting to build a Tokamak design like ITER, but hope to reduce the size considerably by taking advantage of advances in superconductor technology with REBCO tapes.

W7X:The next reactor type I'll mention was in the news a lot a few years back, the Wendelstein-7X in Germany. This is a stellarator design, the crazy twisted car wreck of a thing you may have seen before. The stellarator is shaped that way so that it doesn't require an induced current like the tokamak to have magnetic helicity, because the shape does that automatically.

ZAP:Another well liked dark horse is Zap Energy. They're not as flashy as the other reactors but seem to be working off solid physics that have been proven out over many years. They're trying to do sheared flow z-pinches, which is basically creating a lightning bolt that's perfectly straightened out and super dense.

DPF:One more somewhat obscure option is Eric Lerner's Dense Plasma Focus approach. I'm a little puzzled by this option because it seems to be the exact opposite of Zap, where they make an incredibly twisty lightning bolt instead of a straight one.

FUSOR/POLYWELL:There are a couple reactor types that get mentioned often but are more or less obsolete are the Fusor and the Polywell. A Fusor is a neat device that can be built to fit on a desktop and still produce actual fusion reactions, but has a fundamental design flaw of a physical electrode inside the plasma that introduces too much conductive heat loss. The Polywell is a more advanced concept thay tries to create a "virtual" cathode with orthogonal magnetic mirrors, but I think after many years of experimentation researchers were unable to validate the formation of such a virtual cathode.

NIF:One option that is sort of tangential is the NIF, which you might have heard technically produced more energy than it produced. I dont think its necessarily going to go anywhere, mostly because it's more a weapons program than an energy program, but I think the chirped pulse amplification technology they use is really cool.

GENERAL-FUSION:And finally I'd be remiss if I didn't mention the very highly funded and publicized General Fusion. I definitely give them points for pure childlike wonder. The original pitch was they were going to take a giant swirling tornado of molten metal, fire a ball of plasma into the eye of the storm, then smash the whole thing from all sides with a hundred giant hammers. To be honest is such a wild concept that I don't really know if it really makes any sense or if it's a fever dream. It's undergone a few revisions after finding out that certain parts of its concept just weren't going to work. This doesn't inspire a ton of confidence, but also shows flexibility in their thinking.

There's definitely lots of other companies with other variations, but this gives a general idea of the huge range of ideas and approaches being pursued. I think it's a really cool field to explore and I'd love to hear all your thoughts about it.

So, I have a casual interest, but I find them intriguing. I recently took a trip to Lassen National Park, and saw this boiling mud pool. https://imgur.com/n6dV92U. I am planning a trip next year to Pompeii and Herculaneum. Someday, I am interested in seeing volcanoes in Hawaii and Iceland and maybe more. I casually enjoyed HarryTurtledove's survival novels about Yellowstone erupting, although they are not great literature by any means.

What about you? Any cool experiences with volcanoes or bucket list plans that you would like to share? Do you know fun facts? Do we have any geologists in the room? Take this prompt in any direction you would like.

I'm creating the concept for a story called The Little Differences. It's about an accountant that, one day, out of the blue, notices that a certain calculation is producing a slightly wrong result. Barely noticeable, nothing world-changing,

He runs it on the computer, tries different software, a physical calculator... everything gives a result that's a little off. When he checks on paper himself, he gets the correct result. But, to his surprise, everyone else tells him that he's the one that's off, and that the incorrect result is actually perfectly sound.

I need something that makes sense, mathematically. The weird result must be something that really is wrong, and not just something that programs sometimes get wrong (I don't want it to be explained at all... I mean, the reason why it is occurring must not be something easily reducible to some well-known malfunction). But it must also be minor enough for someone to miss, something that wouldn't really cause much trouble in the real world (is that possible? IDK).

Lastly: it must be something that I'm able to explain (on some level) to a non-math reader.

So, Tildes math wizzes, what you suggest? :D

Hi all,

I am a PhD student focusing in cosmology. I wanted to up the science content here on Tildes, and I thought that one way to do so is to have an informal little Q&A session. As such, feel free to use this post to ask any questions you might have about cosmology specifically, and physics in general.

This may not be as exciting as some other science AMAs given that I am a rather early graduate student, so there may be a lot of questions I don't know the answer to. However, I'm willing to try my best and answer over the next few days, and to let you know I don't know if I don't!

A bit about myself: I did my undergraduate degree at the University of Chicago where I studied physics and mathematics, and then I was a student researcher in a computational cosmology group at a national lab. I subsequently enrolled at UC Davis to continue studying cosmology. Ask me anything about physics, cosmology, or high performance computing!

I also invite anyone else with expertise to chime in as well!

So, I just listened to a This American Life podcast called Ghost in the Machine. In one of the stories, a man decides to calculate, every week, the Average Family Location of his family. By that, he means: once you add everyone's coordinates for every coordinate in which they've been in that period, what city/location represents the average point between them all?

I decided to do the same for my family, which will be much easier because there are no touring musicians among us. The one complication is that a good chunk of the family is on other continents, and I wouldn't want us to "meet" in the middle of the ocean. So some approximation might be warranted.

I'd be happy if someone could provide me the math, I'm fairly confident I would be able to do it with a calculator or maybe put into some crude Python. I don't think I need to make a weekly report, since we're not that mobile. Maybe twice a year, or once every two months.

Thanks!

Edit: I don't know much math

Edit2: holy shit this is not simple at all! Now I feel kinda bad for throwing this problem at you guys. I really thought it would be quick and easy!

Curious if there are movements within the governance or research pertaining to the field that act to promote or suppress certain ideas? Was watching the “Infinity explained in 5 different levels” and thought… maybe there are trends for or against interpretations and/or abstractions that get a rise in people…

Do we have any mathematicians in the house? I've been wondering for a while why math is usually focused around real numbers instead of computable numbers - that is the set of numbers that you can actually be computed to arbitrary, finite precision in finite time. Note that they necessarily include pi, e, sqrt(2) and every number you could ever compute. If you've seen it, it's computable.

What do we lose, beyond cantor's argument, by restricting math to computable numbers? By corollary of binary files and therefore algorithms being countable, the computable numbers are countable too, different from reals.

Bonus points if you can name a real, non-computable number. (My partner replied with "a number gained by randomly sampling decimal places ad infinitum" - a reply as cheeky as the question.) Also bonus points for naming further niceness properties we would get by restricting to computables.

I've read the wikipedia article on computable numbers and a bit beyond.

I'm an intuitive learner. I learn by constantly asking questions, the answers to which i can then effortlessly remember. By messing around and seeing what happens, and then asking why. Lecturers have been enthusiastic about my approach but said I'm going to struggle because the school system in my country wasn't designed for people who learn like this. I want to kill myself.

The way I see myself learning stuff:

• Here's a fresh store-bought kombucha scoby
• Here's a scoby from the same store that I've been growing for 6 weeks
• If I sequenced the DNA from equivalent cells in each of these scobys, would I find any differences? Why?

The way we are actually expected to learn stuff:

• Listening to a lecturer talk for 12×2 hours, and/or reading the referenced literature. Anything mentioned could be on the test.

I have been trying to do it the mainstream way anyway, but I am getting such bad grades that I've had to re-take a year. Even if I found strategies to help me focus I'd still clearly have a competitive disadvantage to people to whom this approach comes naturally. This feels unfair since I know there is a way that I could learn about my field as effortlessly as other people do listening to these lectures.

How does someone like me succeed in academia instead of just scraping through?

I understand that my prefered methpd which I outlined is what you do at PhD level. I'm afraid that by force-feeding my brain all this information that it currently sees as irrelevant, I will kill my curiousity, which I don't want to do because it's the thing that's allowed me to get this far with practically no effort (I went through the archetypal Smart Kid thing in middle school).

For context, I'm in 1st year bachelor's biochemistry (repeating the year). Although I think that at least in my country, all university courses have the format I described.

Since I am also struggling with ADHD I honestly feel like giving up on Uni and going for some sort of apprentiship-style thing. I would like to have a degree though because it's sort of a requirement nowadays and I am genuinely interested in my subject area. Alternatively, what kind of professions seek my method of inquisitively deep-diving into stuff, as I described?