“Your assumptions are your windows on the world. Scrub them off every once in a while, or the light won’t come in.” -Isaac Asimov

Just like every week, we’ve had a slew of new stories to share with you here on Starts With A Bang! It’s been great fun to put these stories together, to share a new corner of the Universe with you, and to explore what’s going on at the frontiers of science together. Want to take a look at everything that’ happened, in case you missed anything? Let’s take a look:

Do you want a fun announcement? I bet you do! For those of you excited about my upcoming book, Treknology, I’ve just finalized that I’ll be at two days of the official Star Trek convention in Las Vegas next month, on August 3rd and 4th, and if you’re there, make sure you come and see me and say hello!

And finally, it looks like there are some problems with a couple of plugins on Scienceblogs: Jetpack (for anyone on the back-end) and Wordfence (for anyone trying to comment). Until the admins get things in order, the best I can recommend is to wait ~10 minutes and try and comment again if you get blocked. With that out of the way, let’s all enjoy the best of our comments of the week!

If you remain outside the event horizon of a black hole, escape is possible; if you fall inside, is there any possible way out? Image credit: The Simpsons / Fox / Treehouse of Horror; deviantART user 15sok.

If you remain outside the event horizon of a black hole, escape is possible; if you fall inside, is there any possible way out? Image credit: The Simpsons / Fox / Treehouse of Horror; deviantART user 15sok.

From Naked Bunny with a Whip on falling into a black hole:
“ES: Are you telling me that your ship must be torn apart by the event horizon’s existence.
NBwaW: No, I was asking why that isn’t the case.”

I want to paint a picture for you. Imagine you’re crossing the event horizon, and part of you is inside and part of you is outside. You’re in free-fall, so in theory, you can’t tell the acceleration due to gravity apart from any other type of acceleration. But you also have this issue that any particle inside the event horizon that emits a boson, even a massless virtual boson, will have that boson be directed towards the central singularity. So why can inter-atomic forces still work? Or inter-particle forces, for that matter?

It’s because there aren’t just two options. (This is the same problem with every Socratic dialogue; the answer isn’t always A or B, Socrates, and you don’t prove A by showing that B is absurd.) The setup implies that either these particles go to the singularity, or they escape to outside the event horizon. Clearly, that latter option is absurd, and so you might think that going to the singularity is inevitable. But what if there are other particles inside the event horizon, too? Is it possible that a particle falling towards the singularity, when it emits a photon, has that photon encounter another particle that’s also falling towards the singularity before it reaches the singularity?

Yes, yes it is. That’s the resolution. Either you tear something apart (i.e., your tether goes “snap”), or you go to the singularity, or you run into something else that’s also inside the event horizon, including something that’s been newly pulled inside the event horizon. Don’t underestimate option C!

The fabric of the Universe, spacetime, is a tricky concept to understand. But we're up to the challenge. Image credit: Pixabay user JohnsonMartin.

The fabric of the Universe, spacetime, is a tricky concept to understand. But we’re up to the challenge. Image credit: Pixabay user JohnsonMartin.

From Elle H.C. on what spacetime is: “At LIGO we can eventually reduce and escape as much noise as possible by setting LISA up in space, but for the LHC there’s no escape.”

So it occurs to me, as we retread this ground again, that you are of the mindset that spacetime fabric is a thing, rather than nothingness itself. We can create visualizations of it; we can write down the laws that govern it; we can quantify the interrelationships of its various components. But it’s not a physical thing that you can poke holes in or tear apart; it’s a mathematical structure that’s well-defined, and the conditions where that structure breaks down — Planck scales — are also well-defined. The LHC doesn’t reach those scales, so we’re positive that we’re fine. Your analogy isn’t applicable here.

The fabric of spacetime, illustrated, with ripples and deformations due to mass. Image credit: European Gravitational Observatory, Lionel BRET/EUROLIOS.

From Pentcho Valev on what science is and isn’t: “This is wrong. Logic comes first – a physics theory should be DEDUCTIVE (general relativity is not). If the theory is not deductive, it is an empirical model that can be endlessly adjusted, and looking for supportive evidence makes no sense.”

You are entitled to your wrong opinion. But it is wrong, as I’ve explained to you; you cannot demand that the logical structure you would impose on the Universe describes the Universe. The Universe is full of examples of things that “make no sense” actually, physically happening. Do please stop spamming my blog with the same screeds, or I’ll have to ban your commenting privileges.

Kasim and Axil: you aren’t far behind.

If you allow a quantum wavefunction to spread when it’s near a false vacuum in inflating space, it could expand for an infinite time into the future, which is the idea behind eternal inflation. Image credit update: Narlikar and Padmanabhan, retrieved from Ned Wright, edits by me.

From CFT on whether it could be infinity: “Sir, you yourself play pretty fast and loose with the whole ‘infinite’ concept yourself.”

I suppose I can count on you to tell us all how to make cosmology great again?

An artist's impression of the three LISA spacecraft shows that the ripples in space generated by longer-period gravitational wave sources should provide an interesting new window on the Universe. Image credit: EADS Astrium.

An artist’s impression of the three LISA spacecraft shows that the ripples in space generated by longer-period gravitational wave sources should provide an interesting new window on the Universe. Image credit: EADS Astrium.

From rich r on something I’m not used to: “By the way Ethan, I love the your articles and writing. As an engineer i have just enough science background to be dangerous and your topics keep my interest and keep my brain bubbling!”

What is this, unequivocal praise? Damn… I don’t even know what to do with myself. Thank you. This may be the antidote I need to some of the frustrations of working hard with little thanks. A little thanks goes a long way!

Oh, I know how to fix things! Let’s address only the comments, for the rest of the Comments of the Week, that have something relevant to say about the physics/astronomy/science that we’re talking about!

The pattern of weak isospins, weak hypercharges, and strong charges for particles in the SU(5) model, also known as the Georgi-Glashow charges. Image credit: Wikimedia Commons user Cjean42 under a c.c.a.-s.a. 3.0 license, created from Garret Lisi’s Elementary Particle Explorer.

From Anonymous Coward on low-energy signatures of new high-energy physics: “Besides proton decay (which is so far coming up empty), are there other low-energy consequences to GUTs and string theory and these other attempts to stretch the frontiers of physics? Only neutrino physics so far seems to be yielding any results that go beyond the Standard Model.”

Yes! And it’s thanks to the non-observations of many phenomena that we can constrain GUTs, string theory, and other beyond-the-standard-model (BSM) physics. For example, flavor-changing-neutral-currents are predicted in many BSM models, where a charm quark could decay to an up quark… but such decays don’t happen. Neutrinoless double beta decay is a feature of a neutrino extension… and that’s not observed. Baryon and/or lepton-number violating interactions should be seen… and they’re not. There’s also the “doublet–triplet (splitting) problem” arising in GUTs, the prediction of additional Higgs particles, and those are unresolved, too.

Yes, I would agree: dark matter, dark energy, and the neutrino sectors are the best evidence we have for BSM physics. But there are other outstanding problems to solve, like baryogenesis, the strong-CP problem, and the hierarchy problem, among others. There’s no doubt new physics out there, but whether further unification is part of the solution is not yet known.

Images from the Hubble Space Telescope show the Great Red Spot shrinking in extent and changing in shape even from 1995 (top) to 2009 (middle) to 2014 (bottom). Image credit: NASA, ESA, and A. Simon (Goddard Space Flight Center).

From dean on getting data from Juno’s flyby of Jupiter: “How long is required for the data to arrive back here?”

Not long! The other eight non-visual instruments sent their data with higher priority, and it was less than 48 hours before the JunoCam images came down. Lucky for you, I got my hands on them pretty fast and you can see them here!

Three members of the Star Trek crew beaming down off the ship. If a planet-to-ship transport of quantum information has been successful, could human beings be next? Image credit: CBS Photo Archive / Getty Images.

Three members of the Star Trek crew beaming down off the ship. If a planet-to-ship transport of quantum information has been successful, could human beings be next? Image credit: CBS Photo Archive / Getty Images.

From Naked Bunny with a Whip on how transporters work in Star Trek: “Transporters break the subject down and beam its atoms along with a reference pattern to the destination, where the original is put back together. The process is spelled out in chapter 9 of the TNG tech manual in excruciating detail.”

What’s been interesting in learning about all the various incarnations of Star Trek, from the various series to the technical manuals, is how contradictory the various explanations are. This makes a ton of sense, of course, since for the most part these were dreamed up as “we need to make this happen, let’s come up with an explanation that sounds plausible.” And so the term Treknobabble was born.

Early incarnations refer to a matter stream; in other series, there is no matter stream and the information is simply stored in the pattern buffers.

What about actual physics? If you have the full quantum state of a macroscopic system encoded, and particles like electrons, protons, nuclei, etc., are identical to and indistinguishable from one another, does it matter which particles are used? The “you” of today has no atoms in common with the “you” of 10 years ago, yet it’s still identifiable as you… isn’t it? The “you” a minute after you become a corpse (someday) and the “you” the minute before have virtually the same composition, yet one has the “you-ness” of the living you and the other doesn’t. So what is it that defines who you are? What you are?

Book cover for my new book: Treknology. Image credit: Voyageur Press / Quarto Publishing Group.

These are among the fun issues I get to explore in Treknology, in the context of the full suite of science as is known in early 2017. I like to think this is what sets it apart from any other treatment of the physics of the Star Trek Universe ever created… and if you get yourself a copy, I think you’ll agree.

Combining Juno’s three main images of the Great Red Spot and enhancing the color and contrast has yielded a spectacular view of the Great Red Spot. Image credit: NASA/JPL-Caltech/MSSS/SwRI/Kevin M. Gill.

From PJ on the first images of the Great Red Spot: “Interesting to note the ‘surface’ of the GRS is much lower than the average surface of the planet. This may indicate some form of subduction caused by the cyclonic action of the spot.”

It’s a very complex system, and whether what you say is true or not depends on what you mean by “surface.” The great red spot is much colder than the rest of the planet, which we have learned from infrared observations, and therefore it should be higher in altitude than the rest of the cloud-tops. The GRS’s cloud-tops are about 8 kilometers higher in altitude than the other, surrounding clouds.

But in the upper atmosphere above the cloud tops, there’s excess heat found over the GRS. (Way over, by the way: like around 800 kilometers up.) What gives? It’s possible that there are pressure waves rising from the spot itself, causing this heating phenomenon. This is part of the mystery that Juno’s other 8 instruments will help solve. In the meantime, let’s enjoy the pictures and marvel at the possibilities!

The two main models for Type Ia supernovae. Image credit: STSCI, NASA; NASA/T. Strohmayer (GSFC)/D. Berry (Chandra).

From Michael Richmond on a Universe without deuterium: “Suppose two 3-solar-mass stars form in close proximity. One evolves into a white dwarf after a common-envelope phase, the orbit shrinks, mass transfers from the main-sequence star to the white dwarf, and *poof* Type Ia supernova. The ejecta from the explosion contains plenty of heavy elements.
Why wouldn’t this scenario create the makings for some planets, even without Type II SNe?”

I mean, that is a possibility. Also a possibility: that two white dwarf stars collide somewhere in space. Or inspiral and merge. Your scenarios are realistic and would happen in a Universe with no deuterium.

But they would take a long time, and they would also produce very, very small amounts of heavy elements compared to the type II supernovae we have, compared to neutron star-neutron star mergers, and compared to the very large numbers of type Ias (relatively) that we have today, due to stars up to about 8 solar masses. As it is, Type IIs are about four times as common as Type Ias, the vast majority of Type Ias had higher-mass progenitors than we can have without deuterium, and the siphoning mechanism you describe would have to be very efficient and long-term to trigger a supernova with such a low-mass white dwarf to start with.

I (crudely) estimate a metallicity about two orders of magnitude less than the Universe we have at present. We might get planets, but they’re going to be very different than the ones we know today!

Image credit: Wikimedia Commons user 28bytes, via CC-BY-SA-3.0.

From Omega Centauri on what elements we’d get: “Though the cosmic abundance chart would be different (would there be Gold and Uranium, or would things stop after Iron?”

Oh, you’d go up past iron without a problem. As you say, Type Ia supernovae get you produce the full gamut of these heavy elements through the r-process, and once you get the initial seeds of these heavy elements, you can then form new stars that produce planetary nebulae.

The Butterfly nebula, perhaps the most beautiful of them all: Planetary Nebula NGC 6302. Image credit: NASA, ESA and the Hubble SM4 ERO Team.

Neutron-capture elements, through the s-process, can fill in the gaps and create significant amounts of elements all the way up to lead/bismuth. The abundance will be low, but the elements will be there. If the rules of fusion were different.

The timeline of our observable Universe’s history, where the observable portion expands to larger and larger sizes as we move forward in time away from the Big Bang. Image credit: NASA / WMAP science team.

And finally, breaking my rule, here’s dean: “Very interesting.
Related note: ignoring science deniers like PV is getting difficult.”

Yup. And if people keep beating a dead horse, they’re going to be doing it somewhere else on the Bulgarian internet.

Thanks for a good week, everyone, and see you back here on Monday for more!

Comments

  1. #1 Elle H.C.
    July 16, 2017

    @Ethan,

    “Your analogy isn’t applicable here.”

    What analogy? That quote was about (escaping) the noise and how LISA in contrast to LIGO can be set up in Space to detect GWs, away from all the noise; while the LHC is all about creating as much noise possible (luminosity), so you’ll never be able to detect light GWs at that facility, because you can’t escape ‘the noise’.

    BTW I never wrote about SpaceTime: “that you can poke holes in or tear apart

  2. #2 Pentcho Valev
    July 16, 2017

    From Pentcho Valev on what science is and isn’t: “This is wrong. Logic comes first – a physics theory should be DEDUCTIVE (general relativity is not). If the theory is not deductive, it is an empirical model that can be endlessly adjusted, and looking for supportive evidence makes no sense.”

    Ethan’s reply: “You are entitled to your wrong opinion. But it is wrong, as I’ve explained to you; you cannot demand that the logical structure you would impose on the Universe describes the Universe. The Universe is full of examples of things that “make no sense” actually, physically happening. Do please stop spamming my blog with the same screeds, or I’ll have to ban your commenting privileges.”

    The words “Einsteinian” and “logic”, combined, form an oxymoron. No need to ban me – I’m leaving your blog.

  3. #3 Simon Morley
    United kingdom
    July 16, 2017

    Spacetime isn’t a ‘fabric’, its an abstract framework (and a mass noun).
    Space references existence, time references change. Hence spacetime references everything, past, present and future.

  4. #4 Michael Mooney
    July 16, 2017

    Ethan from week #168 comments on relativity critics:
    ” I’d rather you just knock off the bad behavior and continue to help everybody learn.
    But I will give you an opportunity to defend your viewpoints: what would it take to convince you that Einstein was right about special and/or general relativity?”

    So I gave my most succinct criticism yet “defending my viewpoint” and specifying “what it would take.” No reply in this weeks post but now I get the prompt “Your access to this site has been limited.” Can’t reach week #168 comments. Let’s see if this comment posts.

  5. #5 Ponmon
    Seattle
    July 16, 2017

    Ethan this was such a wonderful read, I have no idea what any of it meant, but I am vibing with you now at the end of that. I happened here from anothe link. Would love to pick your brain about the physics of sound if you ever get the inkling.
    Shine on my friend!

  6. #6 Elle H.C.
    July 16, 2017

    @MM #4,

    “… but now I get the prompt “Your access to this site has been limited.” Can’t reach week #168 comments.”

    Your not alone, this ‘prompt’ was already addressed by me and others, at the following topic, but for some reason it’s not being fixed … or it’s being overlooked.

    http://scienceblogs.com/startswithabang/2017/07/07/is-it-possible-to-pull-something-out-of-a-black-hole-synopsis/#comment-581167

  7. #7 PJ
    Perth, West Oz
    July 16, 2017

    @4 & 5
    That is the Wordfence Ethan was referring to near the beginning of this session. It’s not aimed at anyone in particular. Seems it may have been resolved since I can access this site once again.
    🙂

  8. #8 PJ
    Perth, West Oz
    July 16, 2017

    Damn, not resolved! Just got clobbered again!
    🙁

  9. #9 Elle H.C.
    July 17, 2017

    @PJ

    “Damn, not resolved! Just got clobbered again!”

    Deleting the cookie from ‘scienceblogs’ in your Preferences seems to solve the issue.

  10. #10 Adam
    USA
    July 17, 2017

    “I want to paint a picture for you. Imagine you’re crossing the event horizon, and part of you is inside and part of you is outside. You’re in free-fall”

    Wasn’t the original thought experiment talking about something being held up by a tether?

    “But what if there are other particles inside the event horizon, too? Is it possible that a particle falling towards the singularity, when it emits a photon, has that photon encounter another particle that’s also falling towards the singularity before it reaches the singularity?”

    If I could ask:

    How would something outside the event horizon detect additional forces from force mediating particles from inside the event horizon that can’t get out? Even if the outside particles send some down, nothing’s coming back in the other direction.

    How would particles inside the event horizon that emit a force mediating particle that hits something further inside detect additional forces if the return particle can’t get back up to it?

    Basically, I’m not getting the Option C listed here. If a particle emits a force mediating particle, and the force mediating particle crosses or goes deeper into an event horizon, even if it hits some other particle in some random location, how’s the original particle going to know?

    Am I missing something obvious? Is a return force mediating particle not required?

  11. #11 Sinisa Lazarek
    July 17, 2017

    @ adam

    check my reply to you on comments of the week 168

  12. #12 Adam
    USA
    July 17, 2017

    @ Sinisa Lazarek

    I appreciate you trying to answer my question, but I think you’re in the same boat I am… an enthusiast who is trying to piece together a view of black holes (in this case) without being an astrophysicist.

    In this case, I think every time the question has gotten answered in the past wee or so, the premise has changed a bit, and for some reason, that’s affected the tack the answer has taken.

    In this case, I’m just concentrating on the original premise of a close up view of a ship somehow holding it’s place against gravity, lowering a tether past the event horizon. Not that looking at it from far away isn’t interesting too!

    Of your reply to my email, here’s the part that is problematic:

    “And if the BH is super massive and event horizon large, and gravitational gradient between nearby slices of space-time shallow enough… you don’t get disintegrated just by crossing it.”

    I think it forgets that although the gravitational gradient might be shallow in that case, the overall strength of the gravitational field is still so strong, that beyond that point not even light can escape.

    In fact, the way I understand it, as you go in, every one of your slices is affected by an even stronger force of gravity. No particles and no information can travel outwards at the event horizon, and they certainly can’t the further in you go. They can’t even go sideways!

    So, long story short, I don’t think the gradient is the issue, even for very large black holes. Instead, it’s the whole ‘All null geodesics, or the path an object moving at the speed of light will travel along, will lead to the singularity at the center of the black hole’ bit that’s the issue.

    So, in the most recent of the posts dealing with this, #81, Ethan went from saying this in one paragraph:

    “So now, let’s come back to the tether example. Whenever any particle crosses the event horizon, it’s impossible for any particle — even light — to escape from it again. But photons and gluons are the very particles we need to exchange forces with the particles that are still outside the event horizon, and they can’t go there!”

    Which seems to say, “Okay, so the bits inside the event horizon aren’t yanking on the bits outside”. But then in the very next sentence and paragraph, he switches to:

    “This doesn’t necessarily mean that your tether will snap; it more likely means that the rushing ride towards the singularity will pull your entire ship in.”

    Which A: seems to contradict what he just finished saying, and B: changes the thought experiment.

    Then it switches again: “Sure, the tidal forces, under the right conditions, won’t tear you apart, but that’s not what makes reaching the singularity inevitable. Rather, it’s the incredible attractive force of gravitation and the fact that all particles of all masses, energies and velocities have no choice but to head towards the singularity once they cross the event horizon.”

    Now the thought experiment has changed again, and everything’s already inside the event horizon.

    Finally, up above, he says in his option C that once you’re in the event horizon, some particles might hit each other on the way down once inside the event horizon, but doesn’t explain how that would be able to propagate a force between the two if a return signal can’t be sent… and that’s exactly how the strong force uses gluons to hold quarks together in protons and neutrons.

    They way I’m seeing this, the instant an object crosses the event horizon, ‘poof’, no part of any atom of that object should be able hold itself together.

    I’m not pulling this out of nowhere… Ethan said that exact thing a few paragraphs up in #81. That’s why switching to saying that the tether would’t snap seemed so jarring at the end. I was hoping he would say that the tether wouldn’t snap, because in fact it had been disintegrating the whole time it was being fed into the event horizon!

    Anyway, long story short, the explanation took a weird left turn at the end there, and the third explanation above didn’t really help at all.

    I hope this gets an answer, or at least gets revisited by Ethan soon.

    Oh, also, sorry if this post has gotten a bit repetitive…. for some reason the comment boxes I always get are super tiny.

    Thank you very much for your time!

  13. #13 Adam
    USA
    July 17, 2017

    Hmm, sorry, looking at this post it is most definitely repetitive. I apologize for my wording choices!

  14. #14 Denier
    July 18, 2017

    @Ethan wrote:

    you are of the mindset that spacetime fabric is a thing, rather than nothingness itself. We can create visualizations of it; we can write down the laws that govern it; we can quantify the interrelationships of its various components. But it’s not a physical thing that you can poke holes in or tear apart

    That sounds an awful lot like you’re declaring LQG to be fiction. I knew you weren’t in that camp and in the past you’ve been very careful in your statements about our current understanding on the nature to space-time, but this new statement seems very sure of it being ‘nothingness itself’ or at least nothing other than a coordinate system. Has something changed?

  15. #15 Denier
    July 18, 2017

    @Ethan wrote:

    Is it possible that a particle falling towards the singularity, when it emits a photon, has that photon encounter another particle that’s also falling towards the singularity before it reaches the singularity?

    Yes, yes it is.

    You’re going to have to explain that one because what I’ve taken in until now says: No, no it isn’t.

    Gravitation bends the fabric of space. X, Y, and Z are not all perfectly perpendicular in the presence of a gravitational field. At the Event Horizon of a Black Hole the gravitational field is so intense the X axis (both ends) points directly toward the singularity, and the Y axis (both ends) points directly toward the singularity, and the Z axis (both ends) points directly toward the singularity.

    One you cross the Event Horizon, every direction that exists is toward the singularity. There is no sideways. There is no ‘away from the singularity’. Because X, Y, and Z are mathematically identical they do not exist as separate entities. There is only a single time-like dimension that goes from the EH to the singularity.

    Matter in that intra-EH dimension cannot emit a photon because there is no time for it to do so. It cannot increase or reduce speed because again there is no time. Mathematically for everything that has fallen beyond the EH, everything everywhere is outside its light cone and therefore any interaction would violate causality. Interaction can’t happen and that is the whole reason for the singularity.

    You seem to disagree and I admit that you know a whole lot more than I do about this stuff, so where is my thinking in error?

  16. #16 Michael Mooney
    July 18, 2017

    Ethan:
    “So it occurs to me, as we retread this ground again, that you are of the mindset that spacetime fabric is a thing, rather than nothingness itself. We can create visualizations of it; we can write down the laws that govern it; we can quantify the interrelationships of its various components. But it’s not a physical thing that you can poke holes in or tear apart; it’s a mathematical structure that’s well-defined, and the conditions where that structure breaks down — Planck scales — are also well-defined….”

    John Wheeler:
    “Mass tells space-time how to curve, and space-time tells mass how to move.” (Standard/ orthodox “spacetime.”)

    So… Which is it, “nothingness itself” (also a “glorius nonentity” as per Brown and Pooley) or a malleable medium as per Wheeler?
    If the later, HOW does mass “tell spacetime how to curve” and HOW does spacetime “tell mass how to move?” The mathematicians don’t bother to explain the physics/ mechanics of that as long as the equations are predictive of mass trajectories.

    Finally, (see my comments in week #168) I’m still waiting for Ethan to disambiguate the difference between apparent length contraction (re: differences in what observers see) and actual physical shrinkage of physical objects as promoted by SR.

  17. #17 Sinisa Lazarek
    July 18, 2017

    @ Denier re:#15

    you are mistaken about what happens beyond event horizon in terms of time and coordinates. Yes, all geodesics point towards singularity at R=0, but there is quite a lot of space between event horizon and center. check:
    https://en.wikipedia.org/wiki/Gullstrand%E2%80%93Painlev%C3%A9_coordinates

    especially the case of “raindrop”.

    …”The supermassive black hole at the center of Messier 87, a giant elliptical galaxy in the Virgo Cluster, is the biggest known black hole. It has a mass of approximately 3 billion solar masses. It would take about 3 hours for light to travel to the central singularity of such a supermassive black hole, and for raindrop, 5 hours.”

    there is “time” beyond event horizon… and all physical processes continue to happen. Yes.. you will eventually end up at r=0… but that doesn’t mean i.e. that no sideways motion is allowed. A poor analogy maybe.. but consider a scenario where you are at a surface of the ocean, above i.e. mariana trench and you strap a concrete block to yourself. You will plunge down and no matter how good a swimmer you are, you won’t be able to swim to the surface… but that doesn’t mean you can’t swim sideways while you are plunging down. The difference in BH is that even a sideways motion will lead to same point at r=0 (geodesics converge to it) but you can move sideways… your motion will be a sort of a parabola.

    • #18 Adam
      July 18, 2017

      @sinisa

      I think you’re conflating ‘sideways’ with ‘down, but on an angle’. According to Ethan, sideways, where you aren’t getting closer to the singularity inside the event horizon is impossible.

      @denier

      Although I don’t see why something couldn’t catch up with something else on the way down if it was going faster. I just don’t see how any collision like that would possibly affect something further out.

  18. #19 Sinisa Lazarek
    July 18, 2017

    @ adam

    I was replying to denier’s comment about there being no time and that x,y and z are all the same etc… i don’t know what his source is, but you don’t become 1 dimensional beyond the horizon.

    take for example a penrose diagram such ad this

    https://spinor.info/weblog/wp-content/uploads/2013/11/penrose-sli.gif

    nothing “dramatic” happens beyond EH other than singularity in finite future. but spacetime is just as on outside. all movement is allowed except going beyond c (more than 45′).

  19. #20 Sinisa Lazarek
    July 18, 2017

    p.s.

    this gives a pretty good explanation

    https://youtu.be/KePNhUJ2reI

  20. #21 Michael Mooney
    July 18, 2017

    My informed guess is that Ethan is way too busy to follow up on his invitation to us relativity critics: To say what it would take to convince us that Einstein was in fact infallible in his formulations of both GR and SR. (That he was “right,” anyway.)

    Just a guess. I am not a prophet.

  21. #22 Michael Mooney
    July 18, 2017

    @Denier #14: “Has something changed?”
    Surely you know by now that Ethan changes his mind from week to week depending on the latest science news feeds.

    I eagerly await his answer to my weeK # 168 “defense of my viewpoint” as a relativity critic (by his general invitation.)

  22. #23 Frank
    Omaha,NE
    July 18, 2017

    Here are my crazy thoughts on what is spacetime etc., if anyone interested:
    http://fb36blog.blogspot.com/2017/07/what-is-spacetime.html

  23. #24 PJ
    Perth, West Oz
    July 18, 2017

    @9 Seems the problem has been addressed; no more issue.
    Thanks for your solution, though.:)

  24. #25 Denier
    July 19, 2017

    @Sinisa Lazarek wrote:

    A poor analogy maybe.. but consider a scenario where you are at a surface of the ocean, above i.e. mariana trench and you strap a concrete block to yourself. You will plunge down and no matter how good a swimmer you are, you won’t be able to swim to the surface… but that doesn’t mean you can’t swim sideways while you are plunging down.

    You can swim sideways because sideways in the ocean is in your light cone. Such a move wouldn’t violate causality and be forbidden by the universe. Perhaps a more apt analogy would be that you can’t be plunging toward the bottom and decide to swim to November 5, 1955. There is no path to 1955 and so it is forbidden by the universe.

    I did read your link about the raindrop but I’m unclear as to who’s clock is recording the 3 hour and 5 hour fall. From the perspective of light time never passes and for an outside observer the raindrop never reaches the horizon.

  25. #26 Denier
    July 19, 2017

    @Adam wrote:

    Although I don’t see why something couldn’t catch up with something else on the way down if it was going faster. I just don’t see how any collision like that would possibly affect something further out.

    Think of it this way: You’ve got a rocket that is trying to maintain altitude above a black hole. The closer you get to the event horizon the more power is needed from the rocket engines to keep the rocket from falling in. At the Event Horizon the rocket engines need to be infinitely powerful to maintain altitude.

    Such engines aren’t possible but if your rocket had such engines, at another place and time such engines could impart infinite G’s of acceleration and could accelerate mass to the speed of light instantly. Alas those engine don’t exist, however the infinite G’s of downward acceleration toward the singularity your hypothetical rocket was trying to overcome at the Event Horizon do exist and your puny finite powered engines can’t stop your rocket from falling into the black hole.

    Infinite downward acceleration. Everything crossing the Event Horizon plunges downward at the speed of time. In fact there is a theory that our entire universe is the inside of a collapsed black hole and what we perceive as the flow of time is the downward fall along the collapsed dimensions of the space the black hole exists in. The theory is called the ‘Black Hole Universe’ and it isn’t that fringe of an idea.

    ‘https://www.technologyreview.com/s/419827/why-our-universe-must-have-been-born-inside-a-black-hole/

    ‘http://news.nationalgeographic.com/news/2014/02/140218-black-hole-blast-explains-big-bang/

    ‘https://www.insidescience.org/news/every-black-hole-contains-new-universe

    To answer your question as to why things don’t catch up, it is because everything that falls in is on a timeline. The future is toward the Singularity and the past is toward the Event Horizon with everything between the end points just flowing along a dimension that can’t be traversed at any speed other than what the universe has dictated.

  26. #27 Denier
    July 19, 2017

    @Sinisa Lazarek wrote:

    this gives a pretty good explanation

    https://youtu.be/KePNhUJ2reI

    That was a good link. Thank you for sharing. I did understand the arguments regarding the geometry of causality as one approaches a black hole but they glossed over the renormalization is barely a mention as to why. If fact they admitted there were other mathematical solutions that didn’t include it at all.

    In sticking to the math, I’ve got a thought experiment for you. Going back to your swimmer tied to the block who can swim sideways as he’s being pulled to the bottom. The shortest distance between 2 points is a straight line. If the swimmer does nothing and there are no currents, etc., the swimmer will fall straight to the bottom. If the swimmer tries to swim sideways, it won’t be straight sideways but the deviation from straight down will lengthen the path to the bottom. If you knew the deviation you could calculate how much energy the swimmer used to try and swim sideways.

    With something falling into the black hole, how much energy would be required to lengthen the path to the singularity? If your answer is anything other than infinite then please explain.

  27. #28 Sinisa Lazarek
    July 19, 2017

    @ Denier
    “but I’m unclear as to who’s clock is recording the 3 hour and 5 hour fall.”

    mmm.. good question. That didn’t cross my mind. I would assume (assumption being mother of all f*** ups 😀 ) that it would be a clock that’s just at the event horizon. I think that it’s just talking about distance between event horizon of such a massive BH and center singularity… several light hours.. i.e. distance between sun and earth being 8 light minutes.

    ” but they glossed over the renormalization is barely a mention as to why. If fact they admitted there were other mathematical solutions that didn’t include it at all.”

    yes.. i.e. Painlev metric (the raindrop article) is one of those other solutions, which doesn’t have singularity at event horizon. Szekeres being another… Those are all exact solutions to the field equations. Remember that in GR there are infinitely many valid coordinate systems to choose from. It is the problem with our knowledge (and equations being really hard) to find a metrics that give exact solutions. That’s why we have relatively few exact solutions. But those are the cases they are referring to. Kerr i.e. is another one, but for a rotating black hole and Kerr metric again has different properties and behaves differently then schwarzschild one.

    “With something falling into the black hole, how much energy would be required to lengthen the path to the singularity? If your answer is anything other than infinite then please explain.”

    Take a look again at the penrose diagram for the interior of BH. (this is for a non-rotating, non-charged one… schwarzschild solution). You still have your light cone preserved inside (45′ to left and right).. but now space and time coordinates are switched. This means that you can move sideways within your light cone, your cone hasn’t been changed to just a line, it still allows for degrees of freedom. But unlike in the swimmer scenario.. moving sideways will actually make you reach the singularity faster. But that doesn’t mean it’s not allowed.
    On the other hand, with rotating black holes.. things get more interesting and there are solutions where lots of funky things happen
    i.e.
    https://www.youtube.com/watch?v=mpODXb6O6-s&ytbChannel=Documentary%20Channel

    and skip to 27 minutes

  28. #29 Carl
    July 19, 2017

    An event horizon is the point where nothing can escape completely, i.e. escape velocity exceeds light speed.

    However, does that mean even the tiniest movement away from the center is impossible? If a flashlight were 1 cm inside the event horizon and an observer was 1 cm outside, I don’t understand why the observer couldn’t see the flashlight.

    Many discussions about the event horizon seem to talk as if it were a knife edge; I’ve never seen where that was authoritatively stated as what we understand.

  29. #30 Carl
    July 19, 2017

    … though in reading some of the recent posts, the descriptions are pretty clear that’s the case.

    Sigh, should wait longer before posting…

  30. #31 Denier
    July 19, 2017

    @Sinisa Lazarek wrote:

    Take a look again at the penrose diagram for the interior of BH.

    This is exactly the part I have a problem with. The Event Horizon is the edge of the penrose diagram. The only way the 90′ (45′ right and 45′ left) light cone is maintained as you approach the Event Horizon is by drawing a portion of the cone off the chart. That defeats the whole purpose of the chart.

    https://youtu.be/KePNhUJ2reI

    In the above link you provided they get around it by adding another penrose diagram (@ 6:55 mark). If this were the case it would mean the center of the black hole has no gravity as it would be in the direct center of the new penrose diagram with time and space at perfect Minkowski Space right angles.

    With regards to the penrose diagram, what I’m saying is there is no second penrose diagram and you don’t get to draw off the chart. Once you get to the line marking the edge of the diagram, the line is all there is. After crossing the Event Horizon X+, X-, Y+, Y-, Z+, and Z- are mathematically indistinguishable from each other and from the axis of r. Any move is a straight line move toward r0 and there is no way to deviate sideways on your way to r0.

  31. #32 Sinisa Lazarek
    July 20, 2017

    @ denier

    the penrose diagram you are referring to (the first one) is for the observer outside of BH, very far away. It’s a graphical representation of schwarzchild solution. Like it’s been mentioned before, schw. solution DOES have a singularity (coordinate singularity) at the event horizon. And is not a correct solution for someone falling in. And that’s what that first “quadrant” shows on it’s edge… extreme dilation (curvature) of both space and time. They are not drawing another diagram.. rather.. they are drawing another “quadrant”. I.e. the full penrose diagram looks something like this:

    https://i.stack.imgur.com/L1xWP.png

    “what I’m saying is there is no second penrose diagram and you don’t get to draw off the chart.”

    actually… yes there is, 3 more.. Think about i.e. carthesan cooridnates.. what we usually plot is positive x and positive y. But then we learn that negative x and negative y are just as valid and we get 4 sections.
    Further, the diagram is just 2d representation.. 1 coordinate for space and one for time… but space still has it’s 3 dimensions. A penrose diagram showing 3d space + time + curvatures would be impossible to draw

  32. #33 Sinisa Lazarek
    July 20, 2017

    p.s.
    for comparison check Kruskal-Szekeres diagram

    https://upload.wikimedia.org/wikipedia/commons/thumb/1/1c/Kruskal_diagram_of_Schwarzschild_chart.svg/512px-Kruskal_diagram_of_Schwarzschild_chart.svg.png

    notice the difference between the coordinates vs. schwartzchild one, here r=0 is a parabola

    “In general relativity Kruskal–Szekeres coordinates, named after Martin Kruskal and George Szekeres, are a coordinate system for the Schwarzschild geometry for a black hole. These coordinates have the advantage that they cover the entire spacetime manifold of the maximally extended Schwarzschild solution and are well-behaved everywhere outside the physical singularity.”

  33. #34 Denier
    July 20, 2017

    @Sinisa Lazarek

    I guess it is just the renormalization taking place at r=1 that I have a problem with.

  34. #35 Sinisa Lazarek
    July 20, 2017

    @ denier

    I understand your sentiment. i.e. in kruskal coordinates, at event horizon T=+/- X … time= +/- space … I guess from math perspective, this is infinitely better then getting 0 or infinity. It doesn’t blow up. What does time=space in real world mean is as confusing to me as is to you. But since coordinates are just tools of us to compute with… maybe it doesn’t mean anything physically other than “my god.. it’s full of stars”

  35. #36 Michael Mooney
    July 20, 2017

    See my comments in #16 then transpose Ethan’s latest definition of spacetime to Wheeler’s often quoted phrase and you get:

    Mass tells nothingness itself how to curve, and nothingness itself tells mass how to move.

    Now let’s do the same with his reply to me on his “What Is Spacetime” blog from last Jan:

    “You keep asking me to define something fundamental to the Universe — spacetime — (ed: nothingness itself) in terms of something else. What answer can I give you? Spacetime is spacetime. (ed: Nothingness is nothingness.) I can tell you what it (nothingness) does: it’s the relationship between distances and the speed of light in the Universe; its geodesics determine how every particle moves through it; it (nothingness) curves in response to matter and energy.

    But that’s like asking me, mathematically, what “1″ is. I can give you a definition, but you want there to be some sort of physical “entity” that spacetime (nothingness) is, and there isn’t. It’s (nothingness is) a property of the Universe. I can describe it, but I can’t ontologically define it in terms of something else. No one can.”

    So there you have it, science fans: the total lack of ontology to explain this nothingness which is “fundamental to the universe,” being curved by mass and which “tells mass how to move.”

    So glad to get that cleared up finally. Thanks, Ethan.

  36. #37 Michael Mooney
    July 21, 2017

    Frank,
    About your link on #23…
    You make a lot of assumptions, but one i agree with is,
    “I think Special Relativity is because flow of information about events is limited by speed of light for all observers.”

    They do in fact claim that simultaneity is relative to the observer… that there is no universal, ongoing NOW. “It depends on whom you ask.” (the “science” of philosophical idealism!)

    But, you buy into the whole “spacetime curvature” doctrine here:
    “…(positive) spacetime curvature around objects with mass…”

    Is “spacetime’ something or nothing?” Check in next week for the latest!