Are Cosmic Strings Cracks in the Universe?
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- čas přidán 25. 05. 2024
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Reality has cracks in it. Universe-spanning filaments of ancient Big Bang energy, formed from topological defects in the quantum fields, aka cosmic strings. They have subatomic thickness but prodigious mass and they lash through space at a close to the speed of light. They could be the most bizarre undiscovered entities that actually exist.
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Someday I imagine myself in an interview and I'll say, "Well, I'm not a credentialed physicist, but I've watched a lot of PBS Space Time," and then I'll be hired on the spot.
Or at least in a Comfort Inn commercial
"I'm no expert... But I've seen one on TV."
Only thing that would be missing is the actual math.
Throw in a holiday inn express and you'll champion right through.
I'm not an actor, but I play one on TV🤔😅
As an old retired welding metallurgist it finally occurred to me on watching this episode that the topological defects you describe are very much like the grain boundaries that form when a weld or a freshly-poured steel ingot cool and solidify. So, more and more it seems that the early formation of the universe was more like a solidification/precipitation event, rather than a "big bang" from a single point. There are many other analogs between the universe formation mechanics you describe and solidification mechanics of metals - grain boundary energy, crystallographic phase orientation angles, and such. If I was younger I might almost feel compelled to investigate quantum mechanical relationships in metallurgical solidification phenomena - as it is, I am just happy to continue growing with your show.
it can still be perceived as a "big bang". imagine a drop of molten metal falling upon a hard surface from the perspective of the hard surface - the metal / heat spreads out in all directions, seemingly appearing at a single point, cooling at a rate consistent with the amount of material in any given area. areas where the metal is thinnest/shallowest cool fastest, others retain heat for longer. and as you say, grain boundaries everywhere.
Big brain analogy.
Grain boundaries are indeed one type of topological defect. Steve Mould has a video about this on his channel
@@cstockman3461 It’s not a defect. A string is not a defect. It’s a normal part of the universe.
Things tend to repeat themselves or mirror themselves in nature, we can understand the big picture by looking in the microscope.
This is shockingly comprehensible and well-explained, even for us non-physicists.
@Dan Nguyen You say that like you can ever completely know something, or like it's possible to be certain you completely understand anything. Knowledge is relative and fluid. Knowing the limitations of your understanding is a mark of intelligence. Every topic can be taught at varying and ascending levels of complexity. I am sure there are biological concepts I understand at a deeper level than the elementary understanding attained by scientists outside of the field, in just the same way that my surface-level understanding of physics is sufficient for me and my purposes. For me to go around saying that people only "think they understand" DNA transcription because they don't have an expert-level mastery of the topic would be as pointless and unhelpful as it is condescending and arrogant.
These videos are aimed at “non-physicists”
Holy Dunning-Kruger Batman!
@@donald-parker Did you read the comment thread? I'm not claiming to have anything beyond an entry-level understanding. I do not understand why y'all are being so elitist about this stuff. Science isn't about gatekeeping.
@Dan Nguyen Why do you even watch these videos if your goal is not to try to understand them? I mean did you just show up to belittle strangers on the internet?
The way Matt explains stuff always makes me feel like I'm in the future listening to someone talk about all this.
Science-Watch-Suggesss - want some?
Why in the future?
@@Neme112 Because it seems like the kind of knowledge on display is beyond the level that we know to exist in society, but in fact these understandings already do exist
Finally, a video that doesn't just explain what a topological defect is, but also explains which specific phases of what were transitioned between.
Agree, that's why I live pbs space time. They not only give broad explanation for a layman but also give some theoretical background. Episode about magnetic monopoles was also brilliant. The only thing I'm waiting for is how does the freakin' Z boson work. Anytime someone talks about weak force it is always through W boson. The only one explanation I found was when Susskind was giving lecture about Higgs mechanism but he called it 'ziggs'.
Back to the topic, shouldn't cosmic strings also have some form of event horizon and as a consequence emit hawking radiation?
@@oskarskalski2982 An episode on neutrino detection would be cool. As far as I know, neutrinos only interact via the Z boson.
I already have proof and also the machine tesla spoke of ..not the death ray that's silly ...but the oscillator machine the real one originally intended ... not the public available design ....don't belive me check out a few of my viedos ....
mind you its made literally bits of everything .....but is really easy to make one and works great once scaled ⚖to the right size.... but even with the one I have you could easily achieve free energy.... I don't have an efficient enough generator, for the size as there is not quite enough torque... and when you see the video you'll know why also it has to be primed and externaly started but once up to speed all is 100%+
@@EebstertheGreat czcams.com/video/uNf5O9UM5OI/video.html
@@EebstertheGreat czcams.com/video/yAP_dftHfJQ/video.html
The videos this channel puts out has kept me sane for the past two years. Can't thank you guys enough
In order to make a nice clear argument in support of string theory, scientists must make at least one video daily, extolling the virtues of a theory which can never be tested. If they were to miss a day for any reason, people might start thinking for themselves.
@@mrquicky so what are you saying exactly? I'm not thinking for myself because I watched a video that featured a mention of string theory in it?
@@mrquicky Can't be tested yet.
@@fgutz1970 maybe we should stick with experiments that CAN be performed.
@@mrquicky Huh. Well, Einstein had theories of gravitational fields and curved space time that weren't proven until after he was dead. Sometimes the theories come first and the ability to test them comes later. Restricting ourselves as you suggest limits the boundaries of creativity and imagination. The practical and everyday application of some of Einstein's theories are now used for things as basic as GPS satellites.
I can't explain how much I love this show. It's beyond my ability to convey.
Thanks PBS and Matt - you all continue to elevate us all above the minimums of our past.
Hey fam, I hope that you and your loved ones are well. I would like to ask you the most important question ever asked:
Who is Jesus? Not who is He to you. Rather, who is He really?
Jesus is the Son of God, who came to the world as a man. He lived a perfect and sinless life . Even though He was perfect and sinless, on the cross of Calvary God wrathfully punished Him for the sins of the world. 3 days later He rose from death. Now He is seated at the right hand of God, ruling as King over Heaven and Earth.
On the judgment day He will judge you, me and every human being that has ever lived. Those who believed in Him will enter eternal joy with Him, but those who did not believe in Jesus will be sent to eternal condemnation.
So turn from your sins and believe in the Jesus, that you can be forgiven for all your sins, because of His death and resurrection.
Acts 15:11
”On the contrary, we believe it is through the grace of the Lord Jesus that we are saved, just as they are."
Ephesians 1:7
”In Him, we have redemption through His blood, the forgiveness of our trespasses, according to the riches of His grace"
Ephesians 2:8
”For it is by grace you have been saved through faith, and this not from yourselves; it is the gift of God,”
John 11:25-26: "Jesus said to her, 'I am the resurrection and the life. The one who believes in me will live, even though they die; and whoever lives by believing in me will never die. Do you believe this?'
1 Corinthians 6:14: "And God raised the Lord and will also raise us up by his power."
Romans 6:9: "We know that Christ, being raised from the dead, will never die again; death no longer has dominion over him."
I don't speak English natively and I never converse with it with my family and friends, plus I fail math, physics, chemistry so badly at school-but I understand 60-100% of things explained in this channel, and I generally understand math better with English. This language is so efficient for such purposes and thus I can prove to myself that school _doesn't_ define my intelligence at all.
School is only supposed to teach you how to learn, how to think (not what to think), basic language speaking/writing skills, basic mathematical skills, basic societal group/obedience to social norms skills (yeah, they are skills). Like many skills, some folks are more talented than others in specific area, and thus, develop them more quickly and completely with proper education.
Children, like every other intelligent creature n the his planet, want to learn. School is supposed to give them the tools, skillsets, discipline (let a kid discover and then learn about what they are interested in, and they focus like lasers) and the encouragement to strive to better themselves, and their hey will. Children inherently want to be adults.
Funny how society don't want them to be, yeah? Almost like the corporatists know you cannot sell an adult anything they don't already want or need, but you can sell a child anything you want whether they need it or not.
Knowledge is power. Ignorance is slavery.
Is the Higgs phase angle something that could theoretically be measured? Or are cosmic strings the only indication of a change in phase angle?
I kind of got from this that they’re looking for that in the junctures, that they’ll see what they’re expecting there to look for elsewhere, but I was thinking the same question and might have just heard the answer I was looking for.
An angle between what and what? What sets the "zero degrees" mark that it would be measured from?
@@MultiSteveB A circle needs not start at any point for us to say that a certain point is 0. we can then assign + or - °s as we see fit.
If we can...
@@MultiSteveB I'm not sure what you mean. Are you saying you need a fixed point? Can't you simply set a fixed point? For example; suppose you have two points in space. Is there an experiment that could determine if the higgs phase angles at these two points are the same direction? Or are you saying that choosing a reference point for phase angle doesn't make sense in this scenario?
@@brandonmunshaw2854 the phase angle describes the angle away from 0°. You can arbitrarily assign *where* 0° is, because the universe doesn't assign one for you. So, there isn't a universal measure of phase angle. (If you had access to other higgs field regions in the universe, maybe you could determine their phase angle *difference*. But any assignment of value would be a human choice.)
This is one of my favorite videos from you all so far, definitely top 10! The fact that you wrap up seemingly separate concepts (vacuum decay, cosmic strings, and gravitational waves), and do so really elegantly, is that perfect blend of entertaining and educating.
FINALLY THIS IS THE THING I WAS LOOKING UP. One time I went down a Wikipedia hole and found this exact concept but when I went to search for it next time, no dice... I could've sworn I was searching for "cosmic strings," but even ignoring the stuff about string theory, I think all I got was micro-scale stuff... and I was like NO IT WAS LIKE A GIANT CRACK IN REALITY LIGHT-YEARS LONG AND I WANTED TO KEEP READING ABOUT IT but I never found it until now! Thank you PBS Space Time!!!
Maybe I was searching "cosmic threads"... whatevs.
That was one of the best Space Time episodes I've seen. Keep up the stellar work!
Pun intended?
@@goldenwarrior1186 No, just an astronomical coincidence.
Saw Prof Ed Copeland talking about this ages ago, interesting topic
Same. His extended interviews on sixty symbols are excellent.
@@iambiggus that's right!
Shout out to his mentor, Tom Kibble, for his work on cosmic strings.
I'm curious how these knots in the higgs field might interact with black holes? Would the black hole destroy the string, or would the cracked higgs field affect the black hole in some way?
We would probably need a theory of quantum gravity to know that. Not sure if Classical GR+QFT in curved spacetime cuts it.
@@codetoil if gravity could be considered a force I imagine all other forces are affected and stopped from transmitting information out of a blackhole meaning it at least gets snapped in half
i must wonder if some advanced civilization could manipulate massive objects as they fell into a blackhole in order to transmit information out of it using gravitational waves
@@NoSubsWithContent snapped in half or bent around it?
I guess, going way back to the Space Time video on blackhole Hawking radiation, we can sort of assume that 1) the string would get pulled in and treat the blackhole's space time like regular space time (so, it wouldn't break, but maybe swirl around "the" singularity/discontinuity in the black hole). 2) There would be a kind vibration on the cosmic string propagating from the event horizon, much like Hawking radiating, due to the Fourier transform of the string's "state" being different than if the black hole wasn't there. I don't know where the energy would come from to make it happen though.
Anyone else just love this guys voice when he explains stuff? I know he could narrate like any show on space or nature.
What happens when a cosmic string lashes through an solid object like the earth, or an neutron star? Or a black hole?? 🤔
If strings are discontinuities in the phase of the Higgs field that cannot smooth themselves out, how do they then vanish by radiating energy? I thought they only formed in the first place because they could not simply go away.
They can smooth themselves out via gravitational waves. It just takes a long time. In other words, we don't think there is a faster mechanism for them to evaporate. They formed and remain intact because not enough time has passed to erode them. Although, I'm not sure if non-loop cosmic strings will actually evaporate away, unless the nucleation bubbles somehow end up aligning themselves; does the mean-value theorem apply to this?
if you have a topological loop (like a vortex) you can gradually shrink it to zero radius and it would actually disappear. I guess they might shrink due to radiating their energy as gravitational waves.
only loops can disappear this way because they can shrink. a continuous string can only straighten out over time.
@@brandonmunshaw2854 wouldn't the non-loop cosmic string only evaporate if there is a complete alignment of the higgs field tho?
@@Alexander_Sannikov that was what I was thinking yeah. but I know physics will behave in stranger ways then simple vector fields, so I'm not quite sure
Pretty sure the cosmic strings can bleed energy by producing loops. Given their literally cosmic length, it probably takes far longer than the universe has existed to dissipate to nothing.
Dark matter. Galaxies then spin around them, and the string chains all the galaxies together, in the cosmic web, right?
This is one of the best, if not the best, descriptions I've run across about how cosmic strings came into being, what they do, and what we would need to see as evidence for them. Thanks for what you do, Matt, et al!
9:43 Whoever made this custom animation for a 15 minute long episode should get a raise
The visual of the cylindrical vortex finally made the strings concept click in my head. Calling back to the monopole made that one click as well. Thanks for doing such a great job!
Given how these cosmic strings behave and should affect space and gravity while also being not directly observable due to not existing in 3D space, I wonder if they'd be a candidate for explaining Dark Matter.
They aren't. We have yet to actually discover or detect dark matter (and it is still theoretical, if a very strong theory), but we do know a lot about the properties it has.
For example, it must be diffuse, and it can't interact with itself in any way other than gravitationally. Cosmic strings are basically the opposite of diffuse, and as discussed, they interact with themselves rather dramatically, chopping themselves into smaller bits.
The next logical question my mind jumped to was "What about those smaller loops, then?" But those would still be far too scarce and far too massive to act as dark matter (remember, only dozens in the entire observable universe, so even if each one split into a million smaller loops, they'd be ridiculously rare). Plus since they decay faster the smaller they are, if they did split up enough to be a plausible candidate for dark matter, they'd evaporate extremely quickly, which Dark Matter doesn't seem to be doing.
What _I_ wonder is if they could be the foundational building block of some supermassive black holes, jump-starting their growth and development...
@@barefootalien could they explain the great attractor instead?
@Barefoot Thank you! I was wondering this same thing, and you answered it perfectly.
Would the existence of these strings have had an observable affect on the structure of the matter on the largest scales? The diagram in the video reminded me of renders of the universe at the largest scale with tendrils of matter creating a connected web. I would think that because of their mass the cosmic strings would attract matter in the early universe and create a predictable pattern.
@@jameilious The great attractor is likely already explained as the Vela Supercluster - you can check out SEA's great video on it here: czcams.com/video/0w4OTD4L0GQ/video.html
What do you mean they don't exist in 3D space? They do.
I appreciate the detail they go into here.
But the real question is: Are cosmic strings a viable candidate for dark matter?
(I'm guessing not: these things being as dense as they are at a mars mass every 100 meters gives them a lot of the same problems as primordial black holes. If there were enough cosmic strings to make up dark matter, we'd notice the gravitational lensing.)
We do see gravitational lensing from dark matter. If you mean localized lensing, the theoretical primordial black holes would be too far apart and rare for that to be likely to get noticed. The constraints on primordial black holes leave us with asteroid masses as the only feasible mass range for them, and that's not massive enough to create noticeable local lensing.
My first thought with this was that it could explain the way that at the very largest scales, superclusters and what not, the universe arranged itself in a very similar way to that network of strings in a cube that they showed in the video. Maybe they just haven't been thinking big enough in their considerations.
That was my thought too. I'm surprised he didn't discuss the possibility that these cosmic strings could be what dark matter is. He did discuss the obvious confusion people might have between these strings and String Theory strings. But for things that may not exist at all, they seem to know an awful lot about what cosmic strings WOULD be like.
@@bxdanny There's also a vast gulf we don't know about them, though. Critical to the question of them being part of dark matter is whether or not they have an irreducible core size. If so, they are a great candidate for at least part of dark matter. If not, they aren't such a great candidate. (To be clear - the "how" of cosmic strings having no irreducible core size is over my head, as is why that matters. I'm going off what scientists weighing in on them as an option have written.)
EDIT: To be clear, though, as a topological defect, they don't so much "contain energy" as a massive object might, so I do see how they aren't bound by a conservation law. I just can't fathom the mechanism.
@@Merennulli Last time I checked, there was an on-going debate if dark matter really exist or if maybe just our gravitational formulas may be incorrect and just not work on a big scale. Lensing from dark matter would be a proof that it exists and I've never heard of any such proof up to now.
The real question I have is at what point do our existing forces break down into multiple even simpler sub forces and when will the universe expand enough to distribute that energy thin enough for that to happen naturally?
I wish Pbs would do a video on Julian Barbours Hypothesis. I know he published a book but I heard it is a horrible more philosophical than phisical reading.
How he exactly imagines that "reversing enthropy" and denying both Big Bang begining and heat death?
If there are "sub" forces that would mean that our Universe is in a false vacuum state and at a point, another quantum giggle could cause another vacuum decay event. There is no evidence that our Universe is in this "false vacuum state", as such our existing forces don't break down to other new ones.
@@BrokeLikeMcHammer My go to example is the electromagnetic field - the 2 forces are intrinsically linked so anywhere you have force acting one the other reacts to it. In theory if the other forces separated due to the early expansion of the universe, these ones could eventually do the same, changing the physics as we understand and use them. we are talking on timelines that make Heat death is a much more present and looming threat sure, but its interesting to think about anyway.
@@BrokeLikeMcHammer But it's exciting to imagine that we could cease to exist anytime by random fluctuation.
Although Nuclear War and Ukrainian Crisis is also sufficient
Just felt everything explain in that video sums too the breakdown being done I side a black hole .
We’re already in it .
Cmb is the event horizon and everything break downs toward lower vacuum energy Into to another blank hole .
I've been intrigued by topology for quite a while now. It seems like one of those math fields that has little to no real-world application... but when applications are found, it somehow is not surprising -- it's too beautiful and compelling not to be 'real' in some sense or other.
Topology is super useful in physics and is the basically the backbone for analysis
@@Tony-cm8lg I'd definitely be interested in seeing more videos about topology in physics. Everything I've seen and read about it has been in pure math.
@@paryanindoeur Topology enters the picture basically whenever you are doing anything that involves a notion of "closeness", i.e. can you descibe when things are close and can they separated in a way. Sounds super weird probably, but that is what point set topology is about. Then we have specific well understood examples of topology that give rise to incredibly rich theories. Originally, topological methods were developed to understand objects from geometry, but because analysis itself is way too "specfic" it seems like it is impossible to draw key distinctions.
It started with integration! Physicists and mathematicians alike tried to solve certain differential equations, but it turns out that there was something deeper about the underlying space on which you are sudying your fields. A fantastic example of this are Maxwell equations! Grassmann, Poincare, Cartan, de Rham and co. started developing a theory to understand this. Poincare started in analysis, but seemed to have gotten frustrated and attacked the problem from a different angle, i.e. he started thinking about loops in spaces and triangulations. He then invented homology, which is one of the big developed branches in algebraic topology. On the other hand, Cartan and de Rham pursued the analytic side of things and de Rham managed to prove that differentail froms, that Grassmann and Cartan developed, give rise to the same structure that Poincare's homology theory does!
In a vague sense, topology tries to abstract away very exact details about spaces and tries to focus on very important key disctincitons between them. This does NOT mean that we do not care about analysis anymore, but often some questions are so incredibly difficult and often you care about a certian "yes or no" question, so you want to do qualitative analysis, instead of quantitative. In fact, these days, topology is everywhere in math, to the point where one of the most essentail classes an undergraduate has to take is a beginner course in general topology. Studying graph theory? You can do topology on it. Studying how to provide good signal coverage for say LTE? Sheaf cohomology, a theory in algebraic topology, will save your day. Cancer research? Knot theory seems to be getting attention there. Doing algebraic geometry? Again, there is topology in there and homological methods appear, although in more abstracted algebraic ways. Smooth machine learning, where you want to teach the model to smoothly predict results? Yeah. A recent nobel prize has been awared for results in something called topological quantum condensed matter. There is also a super young field called topological data analysis. Some people are also working on trying to understand deeper philosophical ideas thorugh topology: e.g. Tai-Danae Bradley is doing some very interesting research in using category theory and topology to understand language, meaning and information.
But, classically, whenever your are doing analysis, there is a TON of topology. Like pretty much all the time, especially complex analysis, which is booming with geometry. Example, physicists love Lie Groups, because they perfectly describe continuous symmetries in their analytical models. Lie group theory involves quite a bit of topology, where in fact there is no upper ceiling, depending on how far you want to go. It was super useful to study lie algebras in the context of QFT, so physicists called them quantum groups(even though they are NOT groups lmao).
Yang-Mills, the theory that unifies electromagnetic and weak force, uses a lot of de Rham's ideas afaik and makes use of differential topology.
Hamiltonian mechanics are a geometrization of mechanics, where suddenly your mechanical systems isn't that "analytic" anymore, but becomes a question of geomtry, very vaguely similar to GR. The key mathematical context here is synthetic geometry, which is in a sense equivalent to contact topology. Lots of topology here as well and hamiltonian mechanics are at the center of modern physics. Also, noncommutative geometry is motivated by quantum mechanics and seems to be applicable there and it makes use of K-theory and foliations, as well as other topological theories.
Dynamical systems use tons of topology as well. E.g. control theory might make heavy use of foliations, which you can think of like a slicing of a space into leaves, which can be well understood. Some PDE's can be desribed in a way, where you are looking for a foliation that satisifes certain conditions.
I hope this convinces you that this is a massive field that has tons and tons of applicaitons.
Sabine Hossenfelder says that a theory that is beautiful is no guarantee of it being true or even useful.
@@Chris_GouletSabine says alot of stupid things, all theories are 'true' in their own 'universe of discussion' wether they apply to reality is not a guarantee but there is value in beautiful theories
I’ve been reading or hearing about cosmic strings for close to 20 years but this was the clearest explanation I’ve ever seen. I finally feel like I have some understanding of what they are.
Amazing, you've taken such a complex and abstract mathematical concept, and made it easy to visualize! Well done again :)
If Schrodingers Cat plays with these cosmic strings, how would we know?
Sounds a lot similar to optical vortices. With the phase and the result of "lines" in space. Lines of darkness that defines the phase of the light.
Eulers spiral man
Mandelbrot
1:16 That "PROBABLY" "Actually" exists... basically sums up theoretical physics of our time
Slight critic: animation at 2:40 really suggests that Big Bang had a point of origin, which probably doesn't help in an educational context.
A great video, as usual :)
This is yet another eye opening chapter in the saga that is the universe
Could cosmic strings explain the filaments and voids of the large scale structure of the universe, i.e., the ‘cosmic web’? Even if the strings have decayed, the gravitational effect of their high energy would have created over densities of regular matter (& dark matter) and thus self-reinforcing? Would it leave imprints on the CMB? Also, for that matter (pun intended), could cosmic strings be a dark matter candidate?
More like dark matter... definitely 😁
Not unless those loops split exponentially and we have tiny loops that still weight metric boat loads flying all over the place. But then I suspect we'd being seeing actual impacts, somewhere, someway.
@@WHYNKO Still need to find Dark Energy then. Seems there are far less candidates for it than Dark Matter, but solving one would make solving the other easier.
@@saran6777 no, cosmic strings as seeds of large scale structures have been largely ruled out sometime ago, due to their CMB imprints
Yes they should have an impact on the CMB but current observations place constraints on their masses because we haven’t seen them yet. And while they would have some effect on LSS formation, it would only be secondary. Original density perturbations from inflation is what seeded the cosmic web.
This channel routinely blows my mind in the best way possible. Thank you for the insight, both at a layman's level and a bit more technical. The latter I can't always follow fully, but you're very good at describing things so I at least can get the gist usually.
Thank you I've been trying to understand topological defects for 15 years as a laymen with some armchair understanding of physics and this is the best video I've seen to explain it while also keeping most of the important conceptual details (aside from the math I mean).
I am a bit confused regarding how a topological defect can "become weaker" and "evaporate". I thought the whole point of topological structures is that they are integer in nature: they either exists In some number or they don't, but nothing in between.
I don't think they can actually evaporate. But a string loop can lose its energy and shrink to Plank size. Another candidate for dark matter.
When a string loses energy it becomes straighter. When a loop loses energy it becomes smaller. Loops can smooth themselves out and vanish, but strings cannot.
Remember that a string is made from the cylindrical knot at the center of a rotating field. A loop would be the core of a torus. You can't straighten the field in one dimension to fix the string, but you can straighten it in two to fix the torus, because the ends of the field connect to themselves and can wrap around to unkink.
Someones grasping at straws. Your not alone in feeling frustrated.
@@stefanschleps8758 learn where the apostrophe goes, smart ****
The energy state becomes more uniform. That is what is being said. The string points to events that kept uniformity from happening. When a string dissolves uniformity has been achieved.
What lucid descriptions and depictions Matt and the Spacetime graphic artists provide! I get it! Thanks for making so much tractable to this lay audience of one!
It is incredible how you can make this concepts so clear and simple to imagine and understands.
This is the very first time I've completely understood the subject. I love this channel so much.
Would the cosmic strings follow the rules of Voronoi analyses, assuming spherical expansion of nucleation points? As in soap bubble interfaces.
and if they do, would there be any effect from crossing into a different Higgs Field area?
My best educated guess is: it would have looked somewhat like a 3D Voronoi diagram in the early universe, but a combination of cosmic inflation and the inhomogeneity of the universe warped them into a more irregular shape over time.
@@hyperduality2838 All I can say is, I hope you don't honestly believe all of that. Too many enthusiasts take a single concept from mathematics or physics and run with it, then dig themselves into a rabbit hole of false understanding. It seems you've done this with the concept of duality. It's a relatively important concept in differential geometry, but it isn't the be-all and end-all like you make it out to be.
Edit: for one thing, there is no such thing as a Higgs Fermion. Higgs particles are all bosons.
@@Nomen_Latinum Sci-curious layperson here
Shapes that look like like using a divided mouth bubble pipe
to add to a pile of bubbles, where they rearrange themselves
trapping concave sided cubes and pyramids in the pile,
or more like dish soap agitated
by strong hot water flow
and creating very tiny, tiny, small, and random larger bubbles in a foam?
Because I'm leaning toward the former
on the universal scale
and the latter on the quantum.
If the former is true,
Does that mean we could theoretically
'drip' a craft or probe along
the boundaries with a vibratory envelope
energy field tuned
to the precise balance of the tension barrier,
and get an assist in propulsion
by minutely adjusting
the topographical tuning of the field emitters
in sections like a jellyfish?
(Sorry. Everything universe oriented translates to sci-fi in my imagination).
Any illumination on the bubble portion of this would be helpful. :)
@@barbaralemons4741 I'm afraid I'm not far enough immersed into this field that I can give you a meaningful answer about the structure of the "foam". As far as the boundaries go, note that these topological defects are strictly one-dimensional and they only appear where three of these "bubbles" meet. On the 2D interface where two of the bubbles meet, the Higgs field would have smoothed out very quickly. So in practice, there are no clearly distinct regions of the Higgs field with well defined boundaries. Only (possibly) the cosmic strings themselves, which I guess in theory you might be able to get a gravitational assist of some form from - though it would probably go unwise to go near them considering how much energy they contain.
Beautifully explained. Thank you so much for your insights, Dr. O'Dowd.
One of the most fascinating videos I've ever watched. Thank you for this!
I like how I've watched so much of this channel I can now just sense when you're wrapping up the video without even looking at the progress bar
If they have prodigious mass, are cosmic strings a possible explanation for the missing mass in the observable universe (aka dark matter)? If not all, then some of it?
Hmm, "dark matter" seems to be evenly distributed where actual matter is not. Cosmic strings would have been detected everywhere then already.
But the vanishing loops could be everywhere, right?
Great question.
@@ClarezaMeridiana If vanishing loops are everywhere, then they would most likely be small. If they are small, they would have already vanished. So I believe the first reply to this comment thread is correct.
(however, I don't know the decay rate of these strings. So my hypothesis could be wrong.)
I was about to ask the same, highly energetic undetectable things in space look like great candidates for Dark Matter.
Bartender Matt teaching us to make clear ice
i like your clear descriptions and depth to my level of understanding. And I learn something every time. Thank you.
About your presentation: if the jiggle is random where does random come from? (momentarily stable at the top of the energy hill until slightest quantum jiggle)
This episode sounds like 10 episodes condensed into 10 minutes.
This is the first video I will need to watch a second time to understand what he is talking about:D
If we could surround certain volume or thing with temperature where higgs field would be zero. Could we move that volume or thing without any inertia? (Of course with wild assumption that thing wouldn't vaporize because of insane temperature).
While the Higgs field supplies mass to the elementary particles, any regular matter gets its mass from bond energies, mostly the strong nuclear force. And we haven't reached the power yet to overcome the strong nuclear force
No.
If we're trying to build a 'shell' around an object, that's like trying to move an icecube by surrounding it with red hot steel under the idea that steam is easy to move. You could move the shell, but the object will stay put and be destroyed when the shell touched it.
Filling the object with net-zero Higgs field would disrupt the very structure of matter in that volume. When the Higgs field is zero, photons don't exist, nor does electromagnetic charge. The object would indeed lose some mass, but also completely disintegrate.
This channel is very awesome with majestic content 🌍💯🤗
Back to a subject/video that I’m super duper lost at. Love it.
We are spoiled for choice in great science communicators on CZcams; and, a collab with Anton Petrov, Kyle Hill, or Hank Green would be so unimaginably awesome 👌(if you haven’t already).
Thank you PBS Space Time for all that you do 🫡🙏
Hello Matt,
Several questions to peak into a mystery at question 3... Thanks in advance!
1) The Higgsfield#-energy peaks in the vortex centers, who's points aligning as 'cracks' (cosmic strings) through space with high localized Mars-like mass. Wouldn't that result in very 'small', that is low NA, lenses? Hence possibly very tiny (in arcsecs) images, escially for relative large (in arcsecs) galaxies behind them, almost impossible (?) to see? How do these compare?
2) Could the radiated Higgs-energy for sibling-cosmic-string via gravitational (maybe) waving-at-us ;-), also loose energy (just like proposed in cosmic inflation) via particle creation? What would be the theoretical rate of this particle creation? Could this lead to the ever expanding space, hence 'growing Higgs-cracks', to keep producing fundamental particles like electrons and quarks?
3) And if that is likely, could this mean that our 'touchable' universe not only keeps expanding from the inside out (i.e. every 'poins' of space 'grows'), but also (re)populates Itself with new particles along these cosmic stretching cracks? Would this save 'us' from the big freeze?
Thanks again, and hopefully you find these questions as intriguing as probably many of us do. ^^ Love to see you a an ep. on that! :~D
...haha, or hire a PhD to dive in! (~;
Warm regards.
nick
The idea of vacuum decay reminds me a lot of certain events that take place in the 3 body problem trilogy. It's simply incredible to think that there might actually be a vacuum decay collapse headed our way at the speed of light, unstoppable, all destroying, unobservable...
Thank goodness the universe expands faster than the speed of light.
@@sagestrings869 if it's closer to you, then i don't think so
@@pursuitsoflife.6119 Its a big Universe, the chance of any vaccum bubble happening close enough to reach us is low... but never zero
@@sagestrings869 Right, but if it's close enough, that doesn't matter.
If it could happen it would've happened already.
If I could have explained these tough concepts as well as Matt I would have stayed a teacher. The SpaceTime team is remarkable, thanks for all the hard work
Really well explained video for such a complex topic! I wonder if the fundamental particles we're familiar with can be thought of as topological defects.
I've always wondered the exact relationship between spacetime and the quantum fields is precisely. Is spacetime a quantum field just like the inflaton field? Perhaps it's the grid upon which quantum fields exist within/upon/whatever, separate from them, almost like a bedrock for everything else. Or is it perhaps that spacetime is actually just the biproduct of forces acting upon one another, much like a waterfall is only as real as the particles and energies that make it up are real.
If anyone has an actual answer, even if it's just really well regarded speculation, I'd love to hear your thoughts.
That's the bajillion dollar question! We don't know yet, as our quantum theory is in conflict with general relativity. Matt sums it up in their video about Quantum Gravity, and also explores attempts at resolution in the vids about String Theory and Loop Quantum Gravity.
A question: At 5:22 Matt said the nearby points in the Higgs field "drag" on each other and "pull" each other to the same value. How does this drag/pull work? (Sounds like it's a force that I'm unfamiliar with.) What are all the properties of these "points?"
All points in the field are connected to all neighboring points. When the field drops at one point, it causes a wave that travels through the field. Watch the video on vacuum decay for more details.
Aiui, there’s a term in the Lagrangian density which is proportional to the Laplacian of the field, and this makes it so the there is more energy when larger regions have larger values of this Laplacian.
I used some fancy words there that you might not be familiar with.
“Laplacian” is basically like the second derivative, except for there being multiple input variables.
Another way to think of the Laplacian is, if at each point, you consider very small spheres centered around that point, and find the difference between the average value of the thing on those spheres, and the value at the point itself, and then divide all that by some power of the radius of the ball. (I don’t remember what power. Might be the square? Not sure.)
Consider a piece of metal where you’ve made part of it red how using a blowtorch. (Ignore losses of heat to the air or from radiating it etc.) Each little bit of metal has its temperature move towards the average temperature of the metal immediately around it. The rate at which it does this will be proportional to the Laplacian of the temperature, as like, the more it differs in temperature from the surrounding metal, the faster its temperature changes.
So, that’s what the
Ok, now, “Lagrangian density”,
this is just a thing that you integrate over space to find the energy.
So, because it takes more energy to like, have the Lagrangian density be bigger in more places, uh, that kinda drives how things change.
@@hyperduality2838 how many times do I have to tell you that you don’t know what you’re talking about/that that isn’t what duality means?
@@hyperduality2838 again, you don’t know what you’re talking about.
I love how the stock footage big bang used at 2:41 has fully-formed galaxies shooting out of it lol
I like that I’m finally starting to understand all this because of you and this channel do such a great job of explaining the pieces and the importance of each part of all theories. 🙏🏼 🇨🇦 ✌🏼
Don't get too excited. A giant chunk of theoretical physics is, you guessed it; completely theoretical.
Basically, these people are making 2nd and 3rd order assumptions from real data regarding things there is no evidence for or real understanding of.
There isn't much difference between this guy's rant and a religious sermon. There a physicists who would tell you that 50% of what he just said is fiction.
We don't know nearly as much as certain physicists want you to believe they know.
Until you mentioned that they emit EM radiation, I thought those strings would be a cool way to explain dark matter. But, if those strings have so much energy and are so tiny, couldn't they turn into tiny black holes?
I'm kind of guessing TBH but they probably don't collapse into black holes (in the way we normally think of blockholes anyway) for the same reason the early ultra-dense universe didn't. Their gravity is very strong but it is pulling equally along the length of the string so it can't collapse on any one point. At the scales these things supposedly exist on, even if they do have a start and an end point, the expansion of space itself over those distances may be enough to support it from collapsing into its centerpoint and keep it under extreme tension.
On the other hand, it's possible these things never got long enough to be supported by the expansion of space in the early universe and just collapsed into the supermassive black holes we see today. Of course the universe might have had both scenarios happen.
they don't emit EM waves. Only gravitational waves @10:27 and also he said they carry energy/mass per unit length @8:46 so smaller strings have less energy....
My logic goes as such, for a circular cosmic string energy(E) is proportional to(~) radius (R)
E~R (cosmic string)
condition for black hole--->
escape velocity= C
which becomes------>
M ~ R (black hole) from energy=0 at surface and M being mass of black hole
So As M ~ E therefore M ~ R (cosmic string)
the two graphs are linear with R meaning that at no point does a loop become "concentrated" enough to have M/R greater than the black hole limit cause its a constant value and evidently that value is mass of mars for every 100 meters, which isn't black hole worthy. the two lines meet at the origin at R=0 and E=0 and that's something I don't wanna even pretend to know anything about
I remember in a book by (IIRC) Feynman about how he was trying to figure out the math for a long thin object to gravitationally collapse, and just couldn't make it happen. It took gravity compressing in all three dimensions to form an event horizon. He was doing this with gas and topological defects are not exactly the same, but it sounds like similar principles might apply.
@@hyperduality2838 All this talk about sub-atomic particles and duality on a video dealing with both macro- and micro-scale cosmic phenomena is making me think that all the antimatter physicists are looking for is in something like a parallel universe that is still part of our own.
So do these things actually decay away? Or are they infinitely extended as they're stretched through space? Because if that's the case, and they have energy based on their length, doesn't that imply a theoretic source of increasing energy, generated by the expansion of space around imperfect vacuum decay?
And these broken, tiny loops that spiral off sound like they'd be very hard to observe chunks of gravity that would barely interact with particles around it.
So are these candidates for explanations of the "dark" energy and mass affecting the universe?
Its reasonable the energy decays, but the cosmological defect remains, at least until the next big vacuum decay event when the universe cools even more
Maybe I was misunderstanding, but I thought the energy itself WAS the defect? That the mass came from the fact that the sliver of space was stuck at a higher energy state than its surroundings because of the conflicting energy states giving it no true "rest" point. Without the defect itself decaying (which, I'll be honest, I have no idea what that would even look like) I don't know how the energy could.
@@Scarker the energy may decay only if the length of such a string decreases. It is most possible for loops. The smaller the loop the less its energy. It is hard to mathematically predict the behavior of a cosmic string loop that has a diameter equal to its thickness (a Plank length). You would need Grigori Perelman for such a calculation.
Yes, in an expanding universe energy will increase by some definitions. For example if 'dark energy' is the energy of empty space, it will increase without bound. (Though this is different from usable energy.) Zero-energy universe models counter this with gravitation's negative energy, giving the cosmos a net zero energy balance at all times.
This was one the best, and most awe-inspiring episodes of Space Time. Kudos!!! I hope cosmic strings are discovered in my lifetime 😊
Hi Matt and PBS Staff! First of all, thank you very much for all you.. each one of your videos is so full of incredible content and information, and Matt you are a great presenter! (:
I was reading around the internet about the research work of Yusef-Zadeh and his team at Northwestern University, they talk about incredibly long strands of cosmic ray electrons moving their magnetic fields at near the speed of light and it made me think about this last video on Cosmic Strings.. could those be the cosmic strings you were talking about here?
Thanks again for being such an amazing source of knowledge
When seeing visualizations of the universe on cosmic scale, filaments and large voids can be seen. Are cosmic strings a potential candidate for explaining the gravitational attraction and formation of these filaments?
These tend to form naturally, we see them, for example, in the structure of styrofoam and bubblegum. They arise when a medium expands but contains something that interacts attractively with itself. Rather than dispersing it tries to form strands to retain that interaction.
If, in the future we do find these "strings", would there be any possibility of harnessing that potential energy to maybe power a spacecraft? I'm thinking of an analogy like a tram car that doesn't have it's own power source, but when on the tracks uses it's connection to the powerlines to power it's motors. Could these cosmic strings one day be cosmic highways?
I think you'd want to be very careful about being near one. An invisibly thin cord with the mass of a planet every hundred feet that occasionally has near lightspeed kinks whipsawing up and down its length every now and again would be *remarkably* dangerous.
Cool idea. You'd have a spacecraft that was pulled along by a string.
@@Vastin That's the idea. Use that almost unlimited energy for yourself..
YES! Great video! More about the Higgs field and "cosmic gauge theory", please! :)
Finally an explanation on what the strings are "made of", or what causes them to exist.
Well done
Since they're 1-dimensional and gravitational, would one of these cosmic strings look like a really long black hole? And would one of the split children look like a dark torus?
@George Moore Ooh, that's an interesting idea! Galaxy filaments definitely look similar to the boundary of a voronoi texture (just like the expanding field perturbations would look like), and the black holes could be the split children of the string. Thing is, that would mean the string is causally disconnected from the rest of the universe.
They wouldn't look like a black hole. The energy density of these strings is the mass of Mars per 100 meters. The Schwarzchild radius of that mass is 0.000949 meters for a non-rotating object, less for a rotating object. They therefore will not have an event horizon which makes a black hole a black hole. They will still have gravitational effects and could cause gravitational lensing as mentioned in the video.
@@curtisshaw1370 They're 1-dimensional, so any radius (even 0.000949 meters) would be thicker than the string. It may be really tiny but it's still an event horizon
@@CyborusYT Except, that dimension doesn't exist. The closest analogue would be a Planck relic: a theoretical primordial black hole from the inflationary epoch that has lost most of its mass via Hawking radiation until it has an event horizon smaller than the Planck length, and assuming it doesn't evaporate completely, reaches an a point where it is impossible to lose its remaining mass. It has a Schwarzschild radius of the Planck length and a mass of the Planck mass, 0.0000217 g. For comparison, one of these cosmic strings would have a mass of 1.0224 × 10⁻¹³ g over the same length. I would recommend looking it up since any videos would probably explain it better than I could. This channel did a relevant video entitled "What If (Tiny) Black Holes Are Everywhere?" You might also want to watch What If Dark Matter Is Just Black Holes?" and "What Happens If A Black Hole Hits Earth?" for more information on substellar-mass black holes.
I admit, I made an assumption about what was meant when it was asked if it would look like a black hole. I assumed the question was asking if had the appearance of black holes that has been shown in many recent simulations and the Event Horizon Telescope image. First, I will address that assumption: It wouldn't look like a black hole; it wouldn't be perceivable. Its radius is less than the wavelength of any possible photon. If it managed to accrete any energy, it would immediately lose it as Hawking radiation (that is assuming a 1D object even can interact with a 3D one). It's total mass would still be too small to curve space time enough to create the effects we expect to see around a black hole: the shadow, the photon ring, seeing all sides from a single point, etc. Those effects are caused by an extreme curvature of space time, and such curvature requires an energy density these strings lack. It would cause some bending of light-microlensing-but not to that degree. Anyway, it's mostly guesswork until someone comes up with a theory of quantum gravity because current physics breaks down at the Planck length.
There are other ways to interpret that question, though. A lot of it would depend on the angle one was viewing the string and how "crumpled" the string might be. Depending on the distance, and the angle, the gravitational lensing of distant objects caused by the string might be confused with that caused by a black hole. Or a very dim galaxy. Or a planet. Given that people are ugly bags of mostly water, if someone got close enough to one of these strings, they would be, if not spaghettified per se, turned into a messy smear by tidal forces. From that person's perspective, it might be easy to confuse it with a black hole.
@George Moore Take the circumference of the galaxy. I assume you mean the Milky Way. Which circumference? The estimated diameter of the Milky Way's disk is 100,000-200,000 light years. Estimates of the Milky Way's dark matter halo go up to 2,000,000 light years. Given that the Andromeda galaxy is 2.537 million light years away, this led to a bunch of articles a few months back about how the collision of the Milky Way and Andromeda galaxies has already begun since their dark matter halos might already be colliding. Let's assume you mean the circumference of the Milky Way's disk using the 200,000 light year figure. That would give a circumference of 628,319 light years. Okay, the event horizon of a supermassive black hole. Which one? The event horizon of the a black hole is related to its mass. The supermassive black hole at the center of the Milky Way, Sagittarius A*, has an estimated mass slightly greater than 4.1 million masses of the sun. The calculated Schwarzschild radius would be 12,111,520 km, 0.081 AU, or 0.0000012802 light years. Its circumference would be about 0.00000804373 light years. If you replaced the sun with it, its event horizon would extend to about 26% of the way to Mercury's perihelion. On the other hand, let's look at the black hole at the center of Messier 87-the one that was famously "photographed" a while back. It is estimated to have a mass of 2.4 billiion suns. Its calculated Schwarzschild radius is 7,089,670,033 km, 47.392 AU, or 0.00074938 light years. If you were to replace the sun with that, its event horizon would extend almost to the outer edge of the Kuiper belt. Let's go with the circumference of the former. If you divide the circumference of the Milky way by the circumference of its supermassive black hole's event horizon, you get 4.90797531 × 10¹¹.
Perhaps you're thinking of mass. The Milky Way has an estimated mass of up to 1.5 trillion suns. If you were to create a black hole of that mass, its Schwarzschild radius would be 0.468 light years or about 11% of the distance to Proxima Centauri.
I suspect you're commenting on how much mass a string would have if you looked at it at a different scale. If you looked at a section of cosmic string with a length equal to the above cited circumference of the Milky Way, its mass would be 3.04 million masses of the sun which is less than the relatively diminutive supermassive black hole at its center spread over a much wider length. If we go in the opposite direction and measure its mass per Planck length you get 1.0224 × 10⁻¹³ g which is less than the calculated mass of a Planck relic black hole which has a calculated mass of approximately 0.0000217 g, or the Planck mass, in the same "volume." Which is really an apples to oranges comparison since were comparing a 1D object with a 3D object. That is assuming I didn't screw up the math which is entirely possible-there were a lot of zeros involved. Assuming Planck relic black holes account for dark matter, there'd be one per 30 km³. If that's the case, they pass through the Earth all the time with no ill effects.
Another thing to consider is that cosmic strings are strings, not singularities. There is not a single point towards which you must travel, at least until you reach a hypothetical inner horizon. A cosmic string has equal density everywhere. If one somehow found themselves inside one, they could travel in every possible direction. And yes, I'm being a bit facetious, but since you seemed to want to give a sense of scale, I figured I'd run with it.
Given their large mass, how close are cosmic strings to having an event horizon?
Pretty far, actually. They have an energy density of about 1 Earth per kilometer, whereas a 'black hole string' would have a density around 1 earth per centimeter of length.
Well, "pretty far" from time perspective. From moment (space) perspective - they are here. Time goes around and has run-out feature, but moment is here around us all the time (cosmic strings), take it and use it how much u want.
Fascinating, as always. Imagine the change that will occur on the day we discover a distant galaxy appearing as a sextuplet on some astronomer's lens.
Wow this area has been unclear to me for ages. Thanks for clarifying it in an intuitive manner.
Could the tiny "loops" that cosmic strings decay into, be a candidate for dark matter?
Cosmic sized strings with huge gravity, stretching through the entire universe... sounds familiar. Is it possible that they have something to do with cosmic filaments / web?
Not really, the cosmic filaments you're referring to relate to how matter clumped in the early universe, not the phase of the Higgs field. If I'm not mistaken they are also smaller in scale than cosmic strings.
@@Nomen_Latinum 'how matter clumped in the early universe' - yep, exactly! My immediate thought was that something made those clumps, and these strings sound like a cause. Or not, I dunno, ofc I'm not an expert, it's just an exciting idea. You might be quite right about size differences though, I have no clue.
@@balazsadorjani1263 It is pretty well understood why matter has clumped into filaments specifically, it's just a result of gravity working on a basically homogeneous universe with some small perturbations. We've done simulations that replicate the large-scale structure of the universe very well without involving cosmic strings. Look up the "Millennium Simulation" if you're interested.
What's not well understood yet is why the universe wasn't perfectly homogeneous to begin with, which is of course also related to how these cosmic strings came into existence. In a nutshell I'd say both cosmic strings and cosmic filaments are a result of this inhomogeneity, but one doesn't necessarily cause the other.
@@Nomen_Latinum Oh I see, okay. Thanks for the info! Great to learn stuff not just from videos, but from comments as well! Have a wonderful day, sir!
I like the little finger making an appearance at 3:17.
Dang it PBSST this is why I keep switching in my mind what I want to do as a career... that is a super cool and exciting topic(s)!
Thank you ;)
Is the Higgs field energy really perfectly symmetric in the field strength for all temperatures below the transition point? Could there be a small asymmetry at an intermediate temperature that makes the vacuum decay have a preferred orientation everywhere? Also if you cool ice slow enough, the nucleation time is much slower than the time it takes for domains to orient. How do we know the universe cooled fast enough (and uniformly enough) that there were multiple nucleation events?
As far as we can tell yes, there's only one transition point at an energy higher than our vacuum (and worryingly perhaps one below it.)
The cooling of the universe is more tricky. If it's infinite then no rate of cooling will be slow enough to avoid the formation of multiple domains. It's actually a similar issue to that of vacuum decay in our current universe. It's entirely possible that our whole universe is a single domain but it's also not unthinkable that domains formed on a much smaller scale. Perhaps one day we'll have solid answers to these questions.
Is a Cosmic String similar to a Quantum Filament?
"No, that's a completely different phenomenon, Counselor."
@@atmaweapon2803 I'm so glad you understood the reference. I read that in O'Brien's voice.
@@Aaron-Fife same! Was a good callback to to the previous episode with the cosmic string!
Another reason why TNG was so formative for me about cosmology - as a kid, I was like "cosmic string? Is that real...?" And I was off to the library. 😁
That's the coolest bit of cosmology I've heard in a long time.
Love this one! Exciting stuff!! Strings and super strings!! Pulsar timing arrays!! I wonder if James Webb will help find them.
Would cosmic strings exist in a universe with 4+1 dimensions, or 2+1 dimensions?
I'm pretty sure that most of the forces need at least 3 spatial dimensions to do anything and might not exist if we had 4 dimensions, so I don't think you can simply talk about the existence of these artefacts of the higgs force if the higgs force stops existing.
Good question!
I don’t know, but here’s my guess:
The topological defect being like a line relates to a continuous function from (3D space with a line subtracted from it) to the circle ( S^1 ) .
(These uh, happen to be homotopy-equivalent spaces, I think, so kinda can think of this as being about maps from S^1 to S^1 . )
Some of these maps can be continuously deformed to a constant map, but some of them can’t be, because they have a vortex-y thing.
If this was in 4D space,
Well, 4D space minus a line I think has a homotopy retract to 3D space minus a point, which in turn has a retract to the surface of a 2D sphere.
Any continuous map from the sphere to the circle can be continuously deformed to one which sends everything to the same point of the circle.
If I haven’t forgotten too much and confused myself, it follows that any continuous map from (the complement of a line in 4D space) to S^1 (the circle) , can be continuously deformed into a constant map.
As such, I believe that the topological obstruction in question wouldn’t be present, and so, if the shape of the potential of the Higgs field was the same, still having a local minimum shaped (topologically) like a circle, then you wouldn’t get such cosmic strings...
However! What if instead of subtracting a 1D line from the 4D space, we instead subtract a 2D plane from the 4D space?
In that case, I think the same thing could happen! Only, instead of having a vortex around each point of a curve, there would instead be a vortex around each point of a surface!
In 2D, I think it would just be around a point, as in the example with the hair.
In order to have things be around a curve in 4D, I think what you would do would be to make the value of some field (in place of the Higgs field) be 3D, and have the minimum value of its potential energy by a sphere.
Very much interested in other types of topological defects. I've been trying to visualize a cosmic texture (3D analogue of strings) for a while now and I can't seem to. I know that they are both diffuse and unstable. I also want to know why some scientists thought the CMB cold spot was a texture at one point.
If you'd like a textbook source to read more, the book "Entropy, Order Parameters, and Complexity" by James P. Sethna is available for free online (legally) here: sethna.lassp.cornell.edu/StatMech/. Chapter 9 is on "Order parameters, broken symmetry, and topology," and is essentially what you're asking about. That chapter seems to focus more on condensed matter than cosmology, but the book is meant to be general (it's not specifically about materials science), and it looks like at least a few of the cited sources are relevant to cosmology and/or particle physics.
What a fantastic video. Well done PBS spacetime
I have ADD its so hard to process this kind of presentation. I love space talk I love learning .
i've just been thinking this whole time, if cosmic strings existed and had mass that great, could they potentially be what we've described as dark matter for so long? or is that even more missing mass from yet another source?
Dark matter must be much, much smaller. It seems to clump up around individual galaxies, giving them the extra mass we observe.
Well if these cosmic strings exist, as mentioned, they will have more specific gravitational signatures than what we see from... whatever dark matter is *for the most part*
That is to say, most of the effects we've observed from dark matter shouldn't be from the cosmic string. However that doesn't mean that all of the effects we attribute to dark matter are not because of strings. Basically, these cosmic strings are not *the* or *the main* cause of most effects of dark matter we have measured so far.
I'll admit one area of this I'm not understanding is if these macroscopic cosmic strings have all decayed to microscopic levels. If that's the case to me it would seem it would be harder to tell if dark matter is strings or not. Still, I'd bet there's a way to distinguish some difference mathematically. For instance the estimated total mass of observed dark matter vs the estimated total mass of the cosmic strings in our observable universe, if there's a huge difference, dark matter still probably isn't mainly microscopic strings.
Also if I'm not mistaken these cosmic strings whether macro or microscopic should not pass through normal matter like dark matter seems to do. If a cosmic string passed through one of us it would slice through us easier than a knife through butter.
@@nerfheardingfuzzball wouldn't it make sense for galaxies to form around these cosmic strings though? and maybe the supermassive black holes in the centers of most galaxies are formed where they form because theres a cosmic string on that exact spot, the singularity of the black hole? that much extra mass could surely attract more gas, form a supermassive star, and collapse into a black hole that grows way faster than most, since it has its own gravity AND the strings gravity to pull matter towards it. there could be cosmic strings woven through the centers of every galaxy even
@@ok-jq1jh ohh i didnt realize the strings had physical properties too, i thought they only affected gravity like dark matter, which is why i thought the two could be related.
I find it difficult to imagine the decay of such topological structures. If we describe these cosmic strings with loop functions, what would the function look like near the limit of its decay? Would it simply shrink to a single point?
yeah. i think the tension of the string would be defined by the gradient of the phase angles around it. so when it decays, the gradient of the angles become lower? the limit would probably when the gradient is so low that all of the remaining energy is able to propagate to its neighbours and becomes a gravitational wave. the end result would probably be that all of the higgs phase angles about that point become aligned. i don't know if the arclength of the loop would actually change through that process though?
i think the string isn't really a physical thing as much as it is a *difference* in force. as a difference in force, it should be able to radiate into gravitational waves entirely and fully decay, right? isn't it just the same concept as diffusion?
@@Deltexterity not sure what you mean by “a difference in force”.
They would have their own temperature, gaining ability to cool as they shrink in size. They would likely decay into particles. Perhaps the universe is such a decay event since the question of scale is not settled.
[Disclaimer: I don’t know quantum field theory.
I have some understanding of functional analysis and like, calculus of variations, but I don’t really know what I’m saying here.]
I think the idea is that the energy is proportional to the length of the vortex (or, uh, maybe multiplied by the number of times it wraps around, if that’s possible?) , and so if you continuously deform it in a way that decreases the length, then that should decrease the energy. And like, the gradient of the energy with respect to the length should be approximately constant, and that constant value is the force, the tension, that it is under.
But that’s just thinking about like, straight segments of it, and when like, the radius of the loop that the string makes is comparable to the radius of the vortex that comprises the string, I would imagine that some stuff happens.
Like, the bump at the middle of the potential isn’t infinite in height, so like...
hm, I guess probably there would start being more energy attributable to the second derivative of the value of the field being nonzero, and like, eventually things in the middle would go over the hump?
I’m going to get some paper.
Edit: upon getting some paper and spending probably over an hour trying to compute the Laplacian in a dumb coordinate system, I did not make any substantial progress in understanding the dissipating.
Wow, this episode gives a lot of intuition on the topic.
Some questions popped into my head:
1. How these cosmic strings are expected to interact with a regular matter, except for gravitationally attracting it? And in the first place, is it "usual" gravity or should it display some special properties?
2. Could it be that their enormous mass created convenient conditions for the condensation of some black holes, maybe supermassive ones?
3. When loops are detached from a string, do they shrink over time? And can they shrink to zero, or some remnant should remain?
4. This direction of vacuum decay. Is it a direction in 3D physical space, or some kind of parameter space?
5. Also just a guess, but I really wonder. Could it be that in the first moments there were nucleation points all over the place on the microscale, and strings desperately reconnected each other until vacuum stabilized on the macroscale? Something like a self-organizing process, maybe? Is it actually possible to make a computer simulation and see what happens?
very well explained, thank you!
First
Agreed, I'm view number 3 and yours was the only comment. It's true folks.
Second! 14 sec after upload!
Ok
@@obionedogan nope I was at 13
Well done
Great episode!
"The first bawlings of the baby universe" I think that's a really nice turn of phrase!
And quite Sagan-esque as well.
Fantastic explanation. Simply Superb.
My favorite video in this series to date
Very interesting, you challenge the mind of people with your videos.
I rarely know much about what’s going on here, but I like it!
This is always so educational and well-structured. Although I very much likened the idea of this kind of thing, I was somewhere lost in the end, because it got a little abstract for me. But I think, thats just my limited imagination. :D
Impressively detailed & yet comprehensible video. Excellent, thankyou.
A couple of questions:
• How sure are we that Cosmic Strings have survived to our epoc? You explained one method for these Strings to break into loops of various sizes & decay. How rapidly does this decay occur over cosmic timeframes?
• If Cosmic Strings are possible, how about Cosmic Bubbles? Small volumes of proto-Space-Time which are divided from our much colder, condensed Universe by walls of Cosmic String material, having formed at microscopic scales, before being stretched out by the expansion of our Universe.
• What would happen should a Cosmic String intersect with a large mass of Baryonic Matter? Would it instantly destablise, converting it's immense mass into energy? Or is it more likely to act like a Cosmic Garotte, slicing through entire planets as it speeds through the Universe - it's gravity pulling & stretching stars like taffy?
• Could Cosmic Strings be stabilised? Would sending inverted waves along their length to negate the natural, loop-forming, destructive waves prevent intersections?
• The Higg-Field variances that you described as nucleation points, creating regions of space-time with identical "Higgs Angle". Could these be detected? Would high-energy experimentation, such as that done with the Large Hadron Collider, potentially create alternate "Higgs Angles" (compared to our local Space-Time)?
• If one dimensional artifacts like Cosmic Points, & two dimensional artifacts like Cosmic Strings & Cosmic Walls, were created by the Big Bang, could three dimensional artifacts be created? (If the initial Singularity existed in a four - or higher - dimensional state.)
what an episode, thank you guys
Fascinating video, it give me the idea of building the most gigantic telescope ever, a black hole telescope that uses the gravitational lenses as primary mirror.
these videos are great thanks