fwiw The Conversation is an online magazine that pairs academics/researchers with journalist editors. The academics do the writing, and their assigned editors offer tons of hands-on support to help the academics to directly communicate their research with the general public in an approachable way.
As a layperson I don’t want to be bamboozled by /woo/. Can any resident astrophysicists here on HN vouch for the quackery, or lack-of, in the linked paper?
Well, this is outside my area of expertise (more of an amateur astrophysicist), but I think it is a serious examination of a somewhat fringe idea. Basically, it is a theory paper asking the question of whether wormholes can explain the phenomenon, and if they were the cause, what would it look like?
I wouldn't take the idea too seriously (and the paper's conclusion seems more like a "no" than a "yes" to me), but it does appear to be a sound examination of the question (though, I would appreciate comments from someone with more knowledge of relativity).
I am by no means qualified to judge physics papers of any kind so take this with a grain of salt, but the invocation of Maxwell's Demon (a thought-experiment method of violating the 2nd law of thermodynamics) suggests it's presenting a pretty fringe idea I think. However, this supposedly happened prior to recombination and, if you can imagine it, I'm even less qualified to guess at the veracity of claims about that epoch.
> Frequency range: 800 – 1088 MHz
> Total integration time: 100 hours
but then
> We observed ORC 1 and ORCs 2–3 (Project code C3350)with the Australia Telescope Compact Array (ATCA)on 9–10 April 2020, at 1.1–3.1 GHz (weighted centralfrequency after the removal of radio frequency inter-ference = 2121 MHz), over a period of 2×12 hours
Do these spectral ranges represent the limits of the emission, or the limits of the instruments measuring it? Perhaps the emission is broad spectrum, and different instruments are picking up different parts of it?
The picture feels especially surprising because of the fuzzy contours and transparency that do not fit the sharp stars. Keep in mind that the image is a superposition of an image in some radiowave frequency range (fuzzy either because of different sensor/tech/frequency range), superimposed to a normal image in visible spectrum with very different actual resolution.
> The ghostly ORC1 (blue/green fuzz) on a backdrop of the galaxies at optical wavelengths.
Astronomical radio images are naturally overwhelmingly sharper than optical images, because radio telescopes today can have much larger apertures than optical telescopes.
The best-resolution optical images are made with two large telescopes and a temperature-controlled optical fiber from each one, arranged to interfere optically, yielding an image resolution equivalent to a mirror the size of the distance between the telescopes as the visual field is scanned on each simultaneously to sample pixels of the image, in sequence.
The electromagnetic interference operation must be conducted purely optically because we are not equipped to sample and record time-registered electromagnetic signals at 1 trillion samples per second. (Yet. It is possible in principle, it just hasn't been achieved.)
In contrast, output from radio telescopes can be sampled and recorded with careful time registration, and the samples interfered numerically, so signals from radio telescopes thousands of miles apart can be treated together, yielding images of overwhelmingly finer detail. Even when using just a single radio telescope, a reflector dish can be made much larger than any practical earthbound optical mirror.
So, if a radio-telescope image is indistinct, it is likely that the object imaged is itself indistinct.
The recent image of a black-hole accretion disc was composed from radio-telescope traces. No optical treatment could produce an image of such resolution.
>Astronomical radio images are naturally overwhelmingly sharper than optical images, because radio telescopes today can have much larger apertures than optical telescopes.
They can be higher resolution with very long baseline interferometry but I wouldn't say they are naturally higher. If I'm reading the article correctly these were collected by the ASKAP telescope array in Australia which has a resolution of 30 arcseconds at 1.4GHz [1], which is only about twice as good as the human eye.
To your point, though, when VLBI is used they can get ridiculous levels of resolution. M87 was imaged at tens of microarcseconds of resolution, which is 4-5 orders of magnitude better than any optical telescope in operation today.
Wanted to follow up to say how ridiculous a microarcsecond is. It's approximately equal to 5e^-12 in radians, which at this level is approximately the ratio of width to distance.
So, for example, it's like seeing a hydrogen atom from 7 meters away. Or a red blood cell from 400km away.
Light rays are effectively parallel at these colossal distances. Everything is in focus.
In fact, only 100 years ago this year was the "Great Debate" (https://en.wikipedia.org/wiki/Great_Debate_(astronomy)) about whether Andromeda and other galaxies were outside the Milky Way, or whether they were small internal nebulae.
To determine distances to things, we use the cosmic distance ladder (https://en.wikipedia.org/wiki/Cosmic_distance_ladder) which is rooted on very close stars whose parallax we can measure over the course of a year.
Thanks for the reply! If we are moving through our galaxy at 220 km/s how long would we have to watch one of these things to determine its precise location (assuming its close) or alternatively set a limit on its distance?
it's angular motion that you care about, so it could still be a long time. We can put some hard lower bounds on how close it could be, though. For example, it's probably not a wormhole mouth within a few ly of our solar system.
The first book is the slowest, the second is thoroughly entertaining, the third is a wild roller coaster ride across unfathomable time and space in a universe that doesn’t care.
There's barely any interesting development to the main character. Strike that. To any of the characters. It's as if the novel follows an emotionless robots without any real social connections at all.
The science story is ... okay-ish. There are some good ideas in TTBP, but all in all I'd rather slog through one of Greg Egan's more spaced-out maths novels.
Greg Egan has good stuff, though. Diaspora is a masterpiece.
>> There's barely any interesting development to the main character.
I thought the second and third book (The Dark Forest and Death's End) dragged on quite a bit, but the lack of character development is probably due to the fact that the author is not writing in the American tradition where a "character arc" is expected.
Think for instance of the two major works of European literature: the Illiad and the Odyssey. At no time is there any "character development" for Achilles, the main hero of the Illiad ("Sing to me, ô muse, the wrath of legendary Achilles"). He starts out as an egomaniacal, bloodthirsty asshole and he ends as an egomaniacal, bloodthirsty asshole. His best friend and lover dies because Achilles is an egomaniacal, bloodthirsty asshole; but does Achilles learn a lesson, say about violence, or egomania, or being an asshole? Does he "grow" and "develop" and "learn from his experience"? Hell no! He is Achilles, the demi-divine, nigh-indestructible death machine! He grabs his kit and goes out to take revenge for the death of his friend, every trait of his unhinged personality amplified ten-fold. He kills Hector and drags him behind his chariot, desecrating his body. He refuses to return the body to Hector's father, Priam, who comes to beg for it. He remains an accomplished asshole for the entire story. When he dies, everyone sighs a sigh of relief. Then Troy falls, by the cunning of Ulysses. The story is over. The hero hasn't grown, he hasn't learned, he hasn't been transformed by his experiences, there has been no character development- but there has been story development, aplenty.
Look also at Ulysses. I have no mean, righteous words for Ulysses. He uses his brain, although he has a momentary lapse of reason when he yells his name at Polyphemus, bragging that he is the one who blinded him, causing Poseidon to come after him to take revenge for his son. Ulysses and his men go through all kinds of epic, legendary encounters with mythic people and beasts, they even go down to Hades and speak to the shades of Achilles and other dead heroes, but there is again no discernible change to the character of Ulysses. He remains cunning, inventive, stoic, determined to return home, hunted by some gods, aided by others, a cursed leader who dooms his companions to destruction by the hubris of his deeds. But does he grow and develop? Not really and Homer doesn't spend much time discussing Ulysse's feelings, or his thoughts - he talks about his actions and through his actions we know what kind of man he is. When he finally gets home he murders all the suitors that beset his wife (and all the women of the house who so much as smiled at one of them), but is that act the result of something that happened in his journeys? Did he start as a peaceful, non-violent man, who learned to use violence in his long journey home? No. He is Ulysses, from start to end. And yet, again, look at the story! The character hasn't changed, but the story, it has moved forward, unstoppable. It is the story of an epic journey through a mythical land, but the man who started the journey is the same as the man who finished it.
I don't know when the idea of "character development became a staple literary cliché, but it is neither necessary to tell a good story, nor a universal characteristic of great stories. In my view, it's simply an easy trick to learn, a standard technique that everyone can master with some effort, either as a writer or a reader. But it should not be an expectation when reading a piece of literary work from an arbitrary place and time.
>> There's barely any interesting development to the main character.
>> the author is not writing in the American tradition where a "character arc" is expected.
My critique is less about a "character arc" and more about any interesting development to the character. Let's take the main character, Wang.
So apparently he works in nanomaterials and he gets drawn into the story because of his scientific education and mindset. We’re told that he’s an avid amateur photographer, but this is just a plot device that gets discarded after serving its purpose. This happens again to his family; they seem completely pointless from the start. His family consist of a wife and a son, are alarmed at Wang’s strange behavior when he starts freaking out about the countdown. But they never really matter again. In all the subsequent developments, Wang never considers his family again. It's been a while since I read it, but to me Wang especially seemed more like a camera rather than a real human person with connections to his family, peers, society. He sees interesting stuff, but it doesn't read like it is happening to a human.
"Sing to me, o muse, the blandness of ...eh.. Wang".
Thank for taking the effort of writing the lines about the Illiad and the Odyssey. I've never read them, but I think I would enjoy a oral performance like they were given when the story was initially crafted.
>> My critique is less about a "character arc" and more about any interesting development to the character. Let's take the main character, Wang.
Oh, I see! Sorry then :)
I agree that most of the characters in all three books are a little ...flat. But that's also part of what I say above, that the characters don't have to have "depth" for the story to move forward, and the story is often the main concern of authors who haven't had a particular kind of training in how to write.
>> Thank for taking the effort of writing the lines about the Illiad and the Odyssey. I've never read them, but I think I would enjoy a oral performance like they were given when the story was initially crafted.
That'd be really something. I wonder if there's any performance like that somewhere.
I thought it was just me. I bought all three in a box set because it was so highly recommended, this comment thread is the first I've read that's critical of it.
I have a hard time understanding how radio emissions can be visualised like that. The sensors are ground based, the emissions are detected on earth from a point source which given the distances are effectively parallel. Or is it a visualization of a circular cloud of point sources, in which case the detector resolution must be fantastic.
They get that resolution by having a radio telescope array with many sensors spread over a wide area [0]. An incoming wavefront will hit the different sensors at slightly different times, depending on the direction the wave is coming from. By combining all the sensors' data, you can calculate the intensity of incoming radiation from every direction in the sky. The resolution increases as you increase the horizontal distance between the sensors, because that makes it easier to resolve the arrival time differences.
Objects exploding outward into a vacuum can be spherical.
Stellar explosions happen all the time in many corners of the universe.
As material from a stellar explosion expands outward and impacts gases in the neighborhood, radio waves are emitted from the molecules energetically impacting each other.
Naturally, the shape of the region from which such radio frequency emissions would originate would correspond to the spherical shape of the explosion.
I don't know why this is being written up as something mysterious. OK, maybe I do know why. Clickbait. Any time you can make astronomy look like there may be a hint of aliens, it's tantalizing and leads to clicks. I don't blame the scientists for this… it's the news headline writers.
Unfortunately working in favor of the clickbait is the fact that certainly scientists won't say that the above simple explanation is definitively what is happening, because it hasn't been tested yet. But you can bet they are looking into simple possibilities like this. And no aliens or Dyson spheres are required.
> I don't know why this is being written up as something mysterious. OK, maybe I do know why. Clickbait.
It's being written up as something mysterious because they don't know what's causing it. Your claim that there is a simple explanation and that they're lying when they say they don't know the cause is not substantiated.
Being aware of and mentioning a simple possible and unproven explanation is perfectly compatible with not knowing whether the explanation is valid or not.
In other words you don’t have to know what caused it, to enumerate some possibilities.
I did not and would not claim that my simple explanation is true. Just that it could be, and that possibility is not being covered in the article, which instead opts for drama.
>Could they be supernova remnants, the clouds of debris left behind when a star in our galaxy explodes? No. They are far from most of the stars in the Milky Way and there are too many of them.
Note SNR explanation is ruled out exclusively because of ORCs' high galactic latitudes. Based on the appearance of these objects my bet is that they are high-latitude SNRs indeed.
The article says that we’re not able to determine distance or put a size on whatever is radiating this, but doesn’t put a clear lower bound on that. What is the closest that this could be that is compatible with the data?
Since they’re all expected to be emitting at roughly the same frequency (or at least we could assume for testing purposes) couldn’t we throw all their data into some maths to compare?
So far as I can see, the general consensus is “if they’re possible they’d form naturally, but they’re probably not possible”.
As for mechanism: quantum fluctuations might make Plank-scale wormholes pop into and out of existence all the time, the inflation period of the early universe might make those tiny ones into big ones, and if a cosmic string got into one that just might keep it from collapsing.
“ We still have no idea how big or far away they are. They could be objects in our galaxy, perhaps a few light-years across, or they could be far away in the universe and maybe millions of light years across.”
The article goes through a list of known cosmic phenomena trying to see if this observation can be explained by each, and concludes it’s unlikely. “Can’t be explained” clearly means “can’t be a explained by a known phenomenon”.
Human language is a beautiful and powerful and (sometimes) ambiguous tool. We could write everything in terms that are completely unambiguous —- like some awful formally-verified programming language —- so people on HN couldn’t possibly adopt an absurdist interpretation and spend time knocking it down. Or alternatively, we can just use common sense and the world can be a slightly more interesting and mysterious place.
Or we can attempt to preserve the meanings of simple words such as "can't" and "haven't" that exist for use in exactly these circumstances. They aren't hard words, and they have a role to play in even the most minimally intelligent conversation.
We should probably count ourselves fortunate that the title wasn't more directly contradicted by the first sentence of the article explaining it. I've noticed this a few times recently.
Sometimes things "can't be explained" with the current theories. We need new theories before we can explain things.
So, in this sense, I'd say it's correct to say that "things can't be explained".
I wholeheartedly agree that discoveries like these are fun. They challenge us to develop new theories, try to make new predictions and then prove these wrong. :D
There is a limit to what can be understood by our human minds. It is arrogance to assume that we are somehow the frontier and limitation of what intelligence is.
It is far likely that we are the fish in the koi pond. Absolute in our belief that there is no up or down, only forward, backwards and sideways.
So many weird things that we see in our dimension that doesn't make sense. Imagine if you picked up a fish and dropped it behind another fish. It is pure magic, teleporation, act of god to the occupants of the koi pond. It would never understand what is outside the pond and why.
Simlarily, it is the common belief that we humans are also those fish in the koi ponds, desperate to explain away and make sense of the unknowable.
Whatever limits we have as individuals are generally invisible to us. It’s fairly easy for us to see those limits in other humans. By extension I have no doubt other humans can see limits in my range of thoughts, and I expect there to be thoughts that no human is able to think.
I don't think worrying about limits is a good thing for us as individuals or as a species. Sure some things are harder to comprehend, but we haven't come across anything incomprehensible yet, let's cross that bridge when we get there.
Usually when I see "limits" in other people it's not so much that they can't possibly comprehend something, it's that it would take an impractical amount of effort and time to have them comprehend it. With better teaching technology it may be more feasible for them to understand these things that were incomprehensible to them, and if not there's always the next generation.
Part of the job mathematics does in science is developing tools for describing patterns - any patterns. We've also learned to deal with uncertainty, so we can now describe approximate, probabilistic patterns as well.
Thanks to this, if there's any pattern about a phenomenon to be found, we likely can describe it already; if not, there's no good reason to believe we won't be able to describe it in the future. That is the first step towards an explanation (second being tying the pattern to theories that fit other observable evidence, and that have predictive power).
If there's absolutely no pattern to be found in a phenomenon, then it implies the phenomenon doesn't have any consequences on anything - which implies it isn't even observable in the first place. From that follows it isn't even worth thinking about.
The greatest human invention is the ability to participate in a massive distributed consensus algorithm ("the zeitgeist"). Humanity as a whole understands things that no single human does.
Humans were also unaware of numbers and counting until we discovered/invented them in antiquity. We may be unaware of limitations that we have now, but we seem to be in a unique position in the animal kingdom to be able to overcome those conceptual limitations once a need for those concepts is identified.
That's why I mentioned the blocks. Everything can be explained. But we as humans in our current state can only understand a very limited portion of everything.
This all sounds very much like there is some reaaally simple solution and nothing fancy going on.
Expecially the "always circular" part threw me off. It looks like the blend effects you get when you make photos against the sun. There might be something similar with radio waves as well.
There are plenty of funny optical artifacts that can happen, and I guess they may have their radio equivalents.
Just today, when shooting our traditional New Year's Eve photo with my wife and kid - us with sparklers in hand - first few images were ruined by ghastly green circles appearing out of nowhere. After quick investigation with a flashlight, I realized that they're artifacts of a bright point light (like a sparkler) hitting the camera - I'm guessing an undesired reflection inside camera's optics. I wonder if something similar may be going on here?
I am asking from the perspective of having no experience. But the article doesn't seem to say that it couldn't be from a point-like source. Can you elaborate?
We can detect them spread out over an area, as shown in the article, not just coming from a single point each. If they were point-like sources, we would see them as a dot in the radio frequency data, like a distant star visually.
Yes, but the thing is we are viewing it at a single location (Earth), and it appears to come from an area, not a single point. The only way to get what we're seeing from a point source is for it to spread out in straight lines in all directions from the source point (as radio waves do, just like light), then somehow change direction towards us to converge back together here, appearing to come from multiple directions. That doesn't happen. (Gravitational lensing can change light's direction in some circumstances, but astronomers know all about that, so they'd give us that explanation if it made sense for this.)
For example, imagine looking across a dark room at a single LED, a point source. You see a point. But the LED is sending light straight in all directions, not just at your eye. The light going in other directions doesn't reach us, so we don't see that "area".
Imagine it's a white computer screen, an area source not a single point, and you can see the rectangular area. Every point on the screen is sending light spreading out straight in all directions, but for every point on the screen one of those directions reaches our eye, so we see the area. The light is coming to our eye from multiple directions, from the different parts of the screen, making the area.
Now imagine reflecting objects at various locations in that room, and an obscuring object in the line of sight so you can't see the LED directly. You can see light from that single point source from various locations in the dark room, but cannot see the origin.
That's what the GP is asking, I think. How do we know the patterns we see aren't reflections or interferences that could be traced to a single point source?
I don't think there exist enormous radio-reflecting objects in space, let alone ones that let through visible light perfectly. And there are many of these circles, so it seems unlikely that all of them could have their source obscured.
https://theconversation.com/wtf-newly-discovered-ghostly-cir...