Brian Koberlein

It's not an assumption, though. https://briankoberlein.com/2015/06/03/sizing-things-up/ > Basically if an object is changing brightness, it can’t do that at a rate faster than the time it takes one side of the object to know what the other side is doing. That time is limited by the speed of light, so if you know the rate at which brightness varies, you know the maximum possible size of the object. Since these objects are also greatly redshifted we have to account for that as well (high redshift means time dilation), but that’s pretty easy to do. So we can take our quasar and AGN observations and calculate a maximum size for each one. Taking data for various quasars, I’ve plotted how many are at each particular size. While they vary in size, the most common size is most commonly around 5 on this graph, which equates to 100,000 AU, or about 1.5 light years across.

Space is called space for a reason. I feel like even scientifically knowledgeable people have a hard time wrapping their heads around just how much space is out there. Here's a good place to start: https://joshworth.com/dev/pixelspace/pixelspace_solarsystem.html Signals diminish with the square of distance. SETI would never hear anything from other stars unless it was broadcast with insanely high transmit power or was directed right at us (and still very powerful). Nobody would do that unless they knew someone was here actively listening. https://briankoberlein.com/blog/et-phone-home/ So for example, to reach the Centauri system (the nearest star) with a signal as powerful as the signal Voyager sends to Earth would require a transmit power of over 100 megawatts at a minimum. That's just the nearest star. It gets exponentially harder as you go further out. For more distant stars you're talking gigawatts or terawatts or beyond. Even barring concerns about attracting attention, why dedicate that kind of resources to operate an interstellar border blaster if you don't even have a reason to think anyone's listening, and if you won't get a reply for hundreds or thousands of years?

I wonder if you just asked 1000 people to draw a spiral without any other context, would there be some handedness/chirality to the drawings? My guess is there would be. https://briankoberlein.com/blog/gripping-hand/ https://pubmed.ncbi.nlm.nih.gov/27852139/ https://www.jstor.org/stable/pdf/658702.pdf

Some info on the word metal as used in astronomy: https://briankoberlein.com/post/hydrogen-helium-metal/ The short answer is that the fraction of metal is so low, they don't care enough to call it something else.

The next part, linked now at the end, is also informative: http://briankoberlein.com/2014/08/20/already-know-quite-bit/ Especially for the graph taken from http://arxiv.org/abs/1112.1320

It's here: http://briankoberlein.com/2013/11/07/massive-issues/

First see footnote 1 of the first page of the preprint linked at the top. The authors are jumping the gun. That's fine for theorists, but bear in mind that they are literally in the dark on a number of telescopic observables, any of which would shoot down the idea in the preprint. Some of these are achievable by EHT. See e.g. Olivares et al. "How to tell an accreting boson star from a black hole" (2020) <https://discovery.ucl.ac.uk/id/eprint/10112389/1/staa1878.pdf> [pdf]. The exotic bosons available in a 3+1 spacetime have never been detected at energy levels low enough that one might expect them to be reasonably bound by the weak (yes, weak) gravitation required by the boson star to keep it supported against ultimate collapse by internal repulsive forces. Until such a discovery this is pretty fatal to the idea. Cold massive bosons are an idea for particle dark matter, incidentally. An example dark matter candidate is the axion. Axions have not been convincingly observed, and might not exist. A compact object made of essentially only axions could plausibly meet the criteria in the preprint linked at the top (cf their axion-motivated scalar field equation at eqn (9)), depending on details of heating during gravitational compaction. Also see e.g. Mohapatra et al., "Dense Axion Stars" (2016) <https://arxiv.org/abs/1512.00108> which is the preprint version of the PRL letter <https://doi.org/10.1103/PhysRevLett.117.121801>. There is as far as I know no clear mechanism…

I was working from the idea of a nyquist or sampling rate needed to "perfectly" reproduce a wave form. I know this works for lower frequencies but I have no idea how well it translates to something like optical frequencies/light. You can find frequency from speed / wavelength: f = v/l or in our case f = c / l since we're dealing with light. I was using 635nm as the wavelength (basically a red laser). That gives you: 3 x 10^8 / 635 x 10^-7 = 4.7 x 10^14 Which should be about 470 terahertz (4.72 x 10^14) give or take a bit. To sample that "perfectly" you'd need to sample at twice the frequency or about 940 terahertz or (9.4 x 10^14). As to your second question, I know that there are single photon detectors. Past that, you've got me. I don't know if that can be classified as "seeing" or not. As to size, there's https://briankoberlein.com/2015/04/14/thats-about-the-size-of-it/ but that might or might not make sense. That's about the limit of what I'm willing/able to say on the subject.