privong

> If you turned in an assignment written in pencil, it was legit for the teacher to use their eraser and give you an F for turning in empty paper. (They never did this but threatened it a lot).

I find this slightly amusing/ironic because many (most?) fountain pen inks are not waterproof. I had a sheet of paper that was full of (fountain pen written) writing on my desk when I spilled a glass of water -- after the paper dried there was hardly any evidence that there had been writing on the paper. I know that's not the parent's point, but something turned in that was written with a fountain pen would be easier to remove: a teacher would just need to dunk the paper in water!

> Radio astronomy was an accidental offshoot of this project: they noticed the reflected microwave signals from space came back with some extra noise...

Perhaps you're conflating Project Echo with Karl Janksy's Bell Labs research in the 1930s? Radio astronomy's "birth" is probably best set to when Jansky detected radio emission from the Milky Way in 1932-1933 while trying to identify the source of noise in wireless telephone transmissions.

Grote Reber picked up radio astronomy in the pre-war (WWII) years and then the advancement of RF technology for radar during WWII led to some further discoveries (e.g., radio emission from the Sun). After WWII, radio astronomy initially had good participation from radar folks.

Many national radio observatories were already in existence before Project Echo. Jodrell Bank Observatory (UK) was established in 1945. ASTRON (Netherlands Institute for Radio Astronomy) was founded in 1949. The US's Green Bank Observatory was created in 1956 and this led to the creation of the National Radio Astronomy Observatory in 1959. Parkes, in Australia, was completed by 1961.

Radio astronomy was well under way before Project Echo.

Active discussion here: https://news.ycombinator.com/item?id=44702782

> Does this project have some relation to LFE?

Can you clarify what "LFE" stands for? Do you mean "Lisp Flavored Erlang" or something else?

Indeed; Yggdrasil is also the name of a set of models of the emission from stellar populations:

https://www.astro.uu.se/~ez/yggdrasil/ReadMe.txt

https://www.astro.uu.se/~ez/yggdrasil/yggdrasil.html

> Unfortunately that comes with the baggage of terrible memory safety.

Isn't this unrelated to the parent post's thoughts about the benefit's of the C/C++ ecosystem (or lack thereof) for dependency management? I.e., a Rust-like language could still exist with a dependency management system similar to what C/C++ have now -- that isn't predicated on how the language handles memory.

"Hieroglyph" [0] was an attempt to address this and write positive science fiction. It was a project at ASU and a book[1] of short stories accompanied by a webpage with essays describing the genesis of the stories and responses to the stories. The book included pieces by Doctorow, Neal Stephenson, Bruce Ster­ling, and others.

I heard about it late last year and picked up a used copy. I ended up reading about 2/3 of the stories and, 10 years after the book's publication, my general feeling was:

1. The stories are overwhelmingly positive and sometimes compelling. But a decade later, the real-life uses of most of the technologies used a plot devices has fallen short of the aspirations in the stories. Reading the stories left me with a feeling of disappointment, seeing that we as a society opted to use most of the technologies in more negative ways (mass surveillance, continued indifference to the amount of carbon we are dumping into the atmosphere, etc.). As a result the stories also felt very naive.

2. The book contains copious links to essays that are hosted on the webpage [0]. They are all gone now; from what I can tell, none of the essays are available at the original URLs. There are also no redirects. The essays have disappeared.

I suppose point 2 is perhaps simply ironic and not much more. I am not sure how to take point 1 though; maybe it is just difficult to read positive predictions that turned out to not happen. Maybe they had an impact though, and things could've been worse in the absence of the books? I am not sure.

[0] https://hieroglyph.asu.edu/

[1] https://www.book-info.com/isbn/0-06-220471-8.htm

> they can probably measure continental drift (only joking)

They can! Continental drift measurements have been done using radio interfometry since at least the 1980s: https://www.nytimes.com/1983/07/05/science/science-using-new... (Though that 1983 article does suggest they were still working on the accuracy). Certainly radio interferometers can measure displacement of dishes after earthquakes.

> Magazines can make a similar comeback for niches like fashion and arts. But they will probably be funded rather differently from the ad-filled old media products.

This has been attempted in the outdoors world for 20+ years. E.g., Alpinist[0] and The Surfers Journal[1]. It works, kinda. Alpinist now has more ads and is a smaller physical size and lower-quality paper than it was at the start. I think it's also had a couple close calls with bankruptcy. I wasn't reading TSJ over a long enough time span to tell if they had similar issues.

[0] http://www.alpinist.com/ [1] https://www.surfersjournal.com/

> What I find scary is that developers see web apps (and hence the open web platform) as no longer fashionable, and instead focus on developing mobile apps (iOS and Android).

Based on my reading of the original article, I think your response here might be a bit tangential to the point about offline work? Web apps and mobile apps are both in practice largely the same in terms of who controls the computing resources -- they generally only work by speaking to the remote servers of the company.

But in detail, mobile apps seem like they would have a slight edge for promoting offline work. While they in practice "phone home" (or even store data remotely), they could in principle be written without needing to contact external servers and in a way that all data is stored locally.

I do agree that apps often attempt to silo users and can do this more effectively than webapps, but as used now, both are mostly online tools and so don't really address the question of tools that are usable offline.

> Any time he goes off on some wild tangent in his books, I assume it's because he just recently learned a lot about it and feels compelled to put that info somewhere.

Stephenson discussed this a bit in the Long Now launch event[0] for "Polostan" and more or less confirmed what you suspect. He also went on to say that he has learned to reel that in and avoid those "rabbit holes". He avoids such digressions in Polostan, in my opinion to the detriment of the book.

[0] https://www.youtube.com/watch?v=KTK1vuv96Rc

> Considering the three body problem and extrapolating I would expect star orbits in a galaxy to be completely chaotic on long time scales?

That's more or less captured by the loss cone calculation. On a very "long time scale" the loss cone will probably be occasionally replenished by stars coming in from scattering on larger scales, but the timescale for this to become significant for galaxies is substantially longer than the age of galaxies (and also longer than the Hubble time, which is the ~age of the Universe). So, at least from this back of the envelope calculation, that doesn't solve the final parsec problem.

See, e.g., https://www.astro.umd.edu/~richard/ASTRO620/Dynamics_Lec3.pd...

> I've been slowly gathering sources and information in the hopes of maybe writing a book about the Lisp Machines

I would love to hear more about this. I have a friend whose mother-in-law was involved in a startup that was selling software for LISP Machines back in the day. She's told me a little about it but I am seeing if I can get more info.

Would you be willing to keep me in the loop if you ever do get around to writing a book? Email is: accounts5 [at] [HN username, minus g].com

They've since updated it:

> Oct 8, 2024

Correction: there are up to 12 of the 7 meter diameter antennas.

It's not a dev environment, but when I have been observing at large (inter)national telescopes, there are often a variety of sound effects in the control room. These sounds often announce a change in status (e.g., observing script started, observing script finished, script failed, script added to the queue).

One example is the Atacama Large Millimeter Array, that in practice is three separate arrays of telescopes (an array up to 50 dishes that are 12 meter diameter, an array up to 10 that are 7 meter diameter, and another up to 4 dishes that are 12 meters in diameter) that are observing different targets at the same time. Each array has its own kit of sound clips and after a few sessions it becomes second nature to identify which array needs attention by the sounds coming over the speaker. "Uh oh, looks like there's gonna be trouble!" followed by another announcement that the script was terminated. Then the array operator works on recovery while I would see if the script should be re-started or if weather conditions had changed enough to warrant a different choice of observation.

Similarly, optical telescopes often have audible alerts when integrations have finished and the data are being read off of the CCD/sensor.

Direct link to the arXiv abstract page, where one can download the PDF: https://arxiv.org/abs/2109.05237

Here's one example, where they measure the separation of spectral features from the OH molecule in a fairly distant galaxy and use that information to put a limit on how much variation there could be in the fine structure constant over the past 2.9 billion years: https://ui.adsabs.harvard.edu/abs/2018PhRvL.120f1302K/abstra...

> The black hole “photo” was constructed using machine learning. I don’t know how it can reasonably be called a “photo.” And although I’m sure their work was reviewed, knowing the nature of computers and data, I wouldn’t be surprised if there were all sorts of errors in the construction of the model that produced that output. What makes the output correct anyway, the fact that it looks like what we expected?

The images of the EHT data were made using several independent techniques performed by different sub-teams who largely worked independently (e.g., [0] for M87). Most of the imaging techniques used are not machine learning approaches, but are rather standard imaging approaches, some of which have have been used for decades in radio astronomy (e.g., CLEAN). The fact that the images made from these different techniques look similar is what lends support to the idea that the "photo" is a reasonable representation. Sure, some images have been created using machine learning approaches, but other images have been done using well vetted approaches that are not machine learning.

But if one doesn't want to trust the imaging techniques, the size of the black hole shadow can be estimated directly from the radio telescope measurements. These are the "visibilities" (essentially measurements of components of the Fourier Transform of the distribution of radio emission on the sky) and the amplitudes of the visibilities (e.g., figure 2 of [1]) indicates that the brightness distribution of the source is approximately a thin ring, with the ring diameter setting the baseline length at which the amplitudes have their minimum.

So the basic result about the black hole shadow can be made from the visibilities themselves, without relying on the imaging. But the images of course make it easier to see some of the complexity (e.g., that the ring around M87 is not axisymmetric).

[0] https://ui.adsabs.harvard.edu/abs/2019ApJ...875L...4E/abstra...

[1] https://ui.adsabs.harvard.edu/abs/2019ApJ...875L...1E/abstra...

Distant objects do tend to look redder because of redshift, but the mottled pattern is a bit too regular to all be distant galaxies. It's more likely to be the noise in the data used for the red channel (likely the infrared Ks filter).

> If I zoom in, I see a reddish mottled pattern. Is that sensor noise, background radiation, or something else?

I assume you mean the pattern that is distributed across the general image? That's noise in one of the three filter images used to make the color image. 2MASS imaged in the J, H, and Ks filters (likely mapped to blue, green, and red, respectively). It could be that the choice of stretch is emphasizing the noise in that filter a bit more. Alternately, the noise there could be a bit higher (at the long wavelength end, Ks starts to cover a part of the spectrum where there's appreciable emission from a ~300K blackbody, i.e., the general temperature of things Earth).

> Similarly, if I zoom out to 30.39 angular degrees, there's a similar-ish green mottled pattern that's very prominent. What's that? It looks like it's got linear features, which might be a stitching artefact of some sort, maybe?

Perhaps regions where the image was made using only the H band from the 2MASS survey?

The background image is not data from Webb; it is a near-infrared image from the 2 Micron All-sky Survey (2MASS). See @skybrian's comment: https://news.ycombinator.com/item?id=40013769

> Is there any mechanical pencil that's meant to toss around in a bag and survive?

I'm not sure exactly what the failure mode is that you're experiencing, but the Rotring 800[0] is retractable. I've gotten a lot of use out of my Rotring 600 but wish I had bought the 800 to be able to retract and protect the lead sleeve.

[0] https://www.rotring.com/pens-pencils/pencils/rotring-800/SAP...

> I’ve had it bork my install so many times that in the end I spent more time recovering nextcloud than actually using it.

I had issues with upgrading a few times on a modest VPS, when trying to upgrade via the web interface. I've since switched to upgrading via ssh by running the `updater.phar` script[0] and haven't experienced an issue upgrading since.

I of course don't know if this would've avoided the issues you experienced, @josteink, but I wanted to mention it in case others have a similar problem to what I had.

[0] https://docs.nextcloud.com/server/latest/admin_manual/mainte...

Growing up, my brothers and I would play "I spy" by identifying a color. E.g., "I spy with my little eye something that is orange".

> I don't think the 39m primary E-ELT is designed to do full sky surveys. AFAIK it is to do targeted observations using multiple instruments.

Correct. I wasn't able to quickly find the maximum size of the FOV available at the E-ELT, but the FOVs of the first generation instruments[0] are not large enough to efficiently survey the sky. The largest FOV instrument for the E-ELT is 6.78arcmin across, compared to 3.5deg for the Rubin Observatory[1] (i.e., 960x larger area).

The E-ELT is large (39m diameter vs 6.5m effective collecting area for Ruben). So the E-ELT has a factor of 36 more collecting area.

However, the Etendue (collecting area * instantaneous FOV) of Ruben is 26x larger than that of the E-ELT. So for surveying a large portion of the sky to a fixed depth, Ruben is ~26x more efficient than the E-ELT.

[0] https://www.eso.org/sci/facilities/eelt/instrumentation/phas...

[1] https://www.lsst.org/scientists/keynumbers

In case folks are interested, the creator of this has recently made a new version, the "Lisp Badge LE": http://www.technoblogy.com/show?3Z2Y

Some previous discussion of the "Lisp Badge LE" on HN: https://news.ycombinator.com/item?id=37682273

@randomcarbloke probably means installing/soldering the components onto the board. E.g., https://www.digikey.com/en/maker/blogs/2021/how-to-populate-...

If they're ~identical construction and being mirrored so that they have the same write/read pattern history, it could trigger the same failure mode simultaneously.

> Possibly a dumb question: can the tension between the two rates simply be resolved because one method measures an old historical rate and one method measures the current rate

This is already generally being accounted for (assuming we have the correct cosmological model for the Universe). The CMB measurement is probing the Universe at an early state (when the Universe was ~380,000 years old) and the Hubble "constant", H(t=380,000 yr), was different at that point from what it is now, H_0 = H(t=13.7 billion years). The comparison to the current Hubble constant (e.g., determined from Cepheids) is made by evolving the CMB Hubble "constant" value to today, under the assumption of our best cosmological model model.

Of course, if we have the wrong cosmological model, then that could be a reason for the discrepancy, and that might point to "new physics". Alternately there may be some systematic in the Cepheid technique that is causing our H_0 estimate to be somewhat off.