The Trouble with Gravity: Why Can't Quantum Mechanics explain it?
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- čas přidán 17. 05. 2024
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REFERENCES:
Quantum gravity simplified: • Quantum Gravity: How q...
General Relativity simplified: • General Relativity Exp...
What does quantum mechanics mean? • What is Quantum Mechan...
Origin of space, time & gravity: tinyurl.com/y6n648ey
How to get rid of infinities? tinyurl.com/2q4j87yd
Why can't quantum mechanics explain gravity? tinyurl.com/y98fsgot
Why quantize gravity? tinyurl.com/2qhngh38
CHAPTERS:
0:00 - Deterministic to probabilistic universe
1:55 - Why must we quantize gravity?
6:22 - What is the central conflict with gravity and quantum mechanics?
9:09 - Why is quantizing gravity so difficult?
9:54 - Where do the infinities come from?
12:48 - String theory and LQG
14:10 - Great course on Wondrium! ow.ly/JFFE50L1hPw
SUMMARY:
In a classical universe, if we knew all the positions and velocities for all particles, we could predict the future and the past. Quantum mechanics is not like this. It shows that reality is not deterministic but is probabilistic. The precise location of a particle cannot be predicted in advance, even in principle. This is the most accurate theory we have. It can account for all the forces of nature, except gravity. Why is gravity so different? Why can’t gravity be modeled by quantum mechanics? Why is Quantum Gravity so difficult?
General Relativity is very accurate, so why must we quantize gravity? Because quantum mechanics works. And General relativity falls apart at quantum scales.
Quantum mechanics says that particles are not like little cannon balls but are like a wave described by a wave function. Particles are waves until some kind of interaction occurs, at which point the wave becomes localized like a particle. But prior to this, we can't predict the location of the particle.
But a photon or electron, just like any quantum particle must also have a gravitational effect because that's what General Relativity says. But if it's a wave prior to an interaction, and it could be anywhere until the moment we measure it, where is its gravitational effect located? General Relativity can't tell us where. We don’t know how this works because we don’t have a quantum description of gravity.
So the bottom line, we know quantum mechanics works well at the smallest scales. And we know that General Relativity works well at large scales. But the problem is that general relativity does not work at the smallest scales. This cannot be because gravity must work at the smallest scales, otherwise its cumulative effects would not work at large scales. This is why most physicists think General Relativity must be brought into the fold of quantum mechanics.
According to Quantum mechanics, all interactions between matter particles are mediated by the force particles. And all these interactions happen with space and time as the background. Gravity doesn’t fit this picture because in general relativity, gravityis due to a warping, or curving of the background spacetime itself. There is no force-carrying particle in general relativity which mediates gravity between matter particles.
This does not mean that General relativity is wrong, it is just incomplete. Why is quantizing gravity so difficult? The short answer is because we get infinities when we try to incorporate gravity in quantum mechanics equations. Where are these infinities coming from?
When an electron and a positron annihilate to create an energetic photon, which then converts back to an electron and a positron, quantum uncertainty is such that the photon on its way to turning into an electron and positron, can convert to any one of a number of different number of particles, for example it can turn into a top quark and anti top quark which annihilates, or it can turn into an electron and positron and back into a photon, or something else.
And it can do this 10 times, 100 times, 1000 times, or an infinite number of times before turning into an electron and positron again. When describing this mathematically, we have to take all the momentums of all the particles and all potential interactions between the various particles into account. There turns out to be an infinite number of combinations of interactions . This is where the infinities crop up in the equations of quantum mechanics. However, this problem can be solved in quantum mechanics by something called renormalization.
#quantumgravity
But renormalization does not work with gravity because instead of just considering all the particles that the photon can turn into, and their interactions, we also have to take into account all the gravitational effects. But just because we can’t solve it does not mean that solutions don’t exist. They probably do, but a completely new approach is needed. Two popular approaches are Loop Quantum Gravity and String Theory. - Věda a technologie
Gravity always fascinated me because it's the only fundamental law that interacts with time. Unlike electromagnetism or the the strong and weak forces, we are living INSIDE gravity (spacetime), which might be why we can't properly study it, because we can't step away from it to analyze it objectively
Everything interacts with time.
@@lacommunautebienconnue349 What they meant is that gravity is not time-invariant like the other forces. Sometimes it's called a fictitious force like centrifugal force - real and measurable, but only a helpful tool and nothing more.
@@hyronvalkinson1749
Gravity isn’t a force.
@@lacommunautebienconnue349 If I shove you, that's a force. It's not a fundamental force and it's caused by other phenomenon entirely but it's still a force. You can still use Newtons to measure gravity
@@hyronvalkinson1749
If it’s not the same definition then it’s not the same thing.
This is by far the simplest and clearest explanation of this issue that I've seen or read, period. Excellent, easy-to-understand graphics aid comprehension. Great job.
There are many others. But your statement is accurate since you said "that I've seen". If you consider all the explanations, then this statement is no longer accurate.
it's entertaining... but i do not understand.
(where gravity is shielding from cosmic radiation gravity can never exeed the speed of light )
@@ThomasJr Can you provide some links or what to search for the other explanations you have in mind?
@@marcinha1973 Do a search for quantum gravity and pick the videos with the most views, such as > 100K. I watched many wonderful videos and even better than this one. Especially from professor Leonard Susskind, Dr. Sabine Hossenfelder, Dr. Don Lincoln from Fermilab, and Dr. Matt O'dowd from PBS Space Time.
Feynman was renowned for his ability to explain very difficult problems to others and so do you Arvin very well done.
I hope I live long enough to see quantum mechanics and general reality come together.
5:16 How would one even do a double-slit experiment with gravitational waves? Nothing blocks causality and it’s hard to articulate as an energy, though it does radiate 🤔
czcams.com/video/_iPJUAzKKLU/video.html
Yooo what’s up tay zonday
Test out heavy particles at ordinary vs. relativistic velocities? Might at least see time dilation effects 🤡
Arvin, you are absolutely my favorite science communicator. You don’t just make the explanations of the physics so clear, you also articulate the questions that demand more fundamental answers and the logic that gets us to new theories and solutions SO brilliantly. I learn so much from your videos, and the most valuable thing is how to *think* better. THANK YOU!
Glad you like them!
Honestly! I watch other channels like pbs and they are not as good at making things simple and easy to understand
@@ArvinAsh You should read Professor Basil J. Hiley. He was the collaborator with David Bohm only Hiley has now relied on noncommutativity to explain relativistic quantum physics. thanks
@@ArvinAsh what can be space-time like in our common day to day experiences? Gelatin
Gelatin is like membrane of string theory
Spacetime is ripple that is writing time code in particular fashion
CZcams algorythm doesn't handle videos above 15 minutes in length very well, unless you know what you are looking for you will go through a lot of trash and pseudo-science channels before Arvin Ash shows up, but by then you already know what quality is, or someone explicitly sent his link, word of mouth still works in the Digital World and Arvin's a diamond in the signal buzz.
I have been looking for something about this topic for what feels like forever! it felt like people would just say "it breaks down once you try to include gravity" and leave it at that-- thank you for such a clear explanation!
Arvin, the graphics on your videos and editing consistently impress me. I learn a lot more because of how skillfully you integrate the text with images.
The graphics for timespace are inaccurate. They show a 2D representation of a 4D phenomenon. Timespace forms spheres or shells around all matter that warps inversely when a heavier object enters the field of a lighter object. It's not a flat trampoline.
@@Scott-qe4wy I get what you said and have wondered about such representations. If imagining/rendering the 2D plane distortion across a third dimension can the spherical warping be be represented? It’s such a common demonstration of gravity, the rubber trampoline bowling ball demo in science museums…
It’s crazy how you don’t have at least a million subscribers, this video was very easily understood by me (a junior in high school with a C in physics), and very well put together as well.
He's almost there, don't worry
For anyone who's lost, the first question should be "Wth is Space Time, anyways?" Well, Let me help.
Space = Meters
Time = Seconds
Force = Meters/seconds squared.
The squaring of seconds makes it a curve on le graph.
Tada, Forces = Space Time Curvature. It's literally just a more confusing term to use to make everyone feel dumb
Welcome to Einstein did nothing useful 101 ( and anyone hero worshipping him is weird because ykno, he abused his wife who probably did the math and actual science for him, then he left her for his cousin. What a charming "genius")
@@rhyvehr I don't think your comment was on topic, warranted, or well explained.
Nobody in this specific comment section mentioned Einstein. Anything I could look up on the subject shows that while they did often work together, he credited her for her contributions. But again, I's irrelevant anyway because nobody mentioned them.
Second, nobody asked you to explain anything either, as nobody was lost. They were _specifically mentioning_ how the presenter did a great job of explaining, such that even a layman would understand.
So finally, why did you decide to post that?
@@josephdavis3472 "huh duh im finna protect einstein"
You're right, I'm sorry, I'm not someone with a C in physics. In university my physics mark was 40% above the rest of the class and my professor was like "what?"
Physics isn't difficult to comprehend, physicists are, and translating between the two is hard. Why did I excel? Because I translated the presented information into ideas I can grasp and then didn't bother to study *literally anything presented*. The biggest problem *with this content* is that this is all theory, most of it is going to be wrong within a matter of years because someone's going to have a new theory. And so without a *concrete comprehension of what's going on* people create *bullshit ones* and then *become superstars to everyone else* acting like they understand it *when they really don't*.
I'm unfortunately not everyone else. I'm someone who thinks firmly that those who have the ability to understand a concept, have the responsibility to help those who don't. I only actually watched to the point he mentioned einstein, and stopped watching, as that, to me, discredits the entire presentation because it's based off of flawed principles. Hence my explanation about einsteins theory of gravity and why it's bogus (because it wasn't actually a new idea, it was just rewording the definition of force) But you're right, here we go, i'm going to watch it. Yeah nope I can't do it, "cant predict black hole center blah blah blah"
Yeah, I'm sorry, but nobody's finna have an idea of what's going on inside a black hole until we have a way of getting sensors inside of it. What does that mean? This video is speculation about speculation about speculation. That's a few too many speculation ^ 2'd for me. And that's actually really important to realize, none of this is actually in any way accurate, it's just someones idea of what *may* be accurate *with our remarkably bad ability to observe the phenomena* and they never really tell you that.
And the mere fact that you right now, want to discredit the ideas i'm presenting because I used the word "finna" actually says alot about who *you* are, not who *I* am. And the fact that I know exactly what you were *finna* think right now is kinda sad, because you like to think of yourself as unique and smart and well thought-out, but you're well worded, not thought-out'. And now you're wanting to act like i'm being crazy for predicting that, and that's even funnier because you're still thinking you've thought anything this entire time.
@@josephdavis3472 Where'd you go man, I was actually really interested to see which angle you were going to take there.
This is one of the simplest explanation on this topic I have ever come across on internet. The graphics in video are super explanatory. In Physics, it is very important to have clear understanding of the most fundamental concept and your tremendous efforts to simplify such difficult subject are commendable.
I've been looking for a video like this for a few months now. I can't get enough of quantizing gravity.
Then you might like to see my theory…. 1st Page:
czcams.com/video/5kARrZl66xI/video.html
2nd Page:
czcams.com/video/T3oor9i-Eh8/video.html
3rd Page:
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Wow, that was an explanation of quantum gravity and its problems that even a lay person could understand. That was a super impressive piece of work!
I'm a physicist and I thought that was very well explained.
THANK YOU! Excellent explanation for people like me who doesn't know tons of physics (I'm a Pediatrician) but really like physics videos! Hope your Channel gets more subscribers, all of your team deserves it!
Check out the Fermilab youtube channel, also very easy to understand the basics.
Like others have already mentioned, I have never seen a simpler video that deals with heavyweight topics like quantum gravity. Arvin, you are gifted seriously. Your videos are simple and easy to absorb by total amateurs but at the same time it also serves the right amount of details. Great job! I had read about these topics on wikipedia but never did I ever feel complete in my understanding. After watching your vid, I am now in a position to speak one line or two on why gravity doesn't work at quantum scales and why do we even need to merge the two realms.
You explain very complex concepts in a way that is accessible to novice students. Great stuff!
I figured it out! Check out my theory on here! 🤯
All I can say is be glad the tens floated and saved the cyclic pi or the boat would be absent many more present day oars.
@@brendawilliams8062 Is it time for your medication?
"It is not incorrect,its incomplete" Sounds like me when i try to explain my math teacher why i deserve a point
Haha. Feel free to plagiarize that line my friend!
@@ArvinAsh When you steal ideas from one person, it's plagiarism; from many, research.
This is a great video Arvin, thanks! You always do such a great job of explaining things. I particularly like the fact that your graphics showed the Feinman diagram's with the gravity field distortions underneath them. I have heard similar explanations before but without that specific graphic, I did not grasp what the speaker was trying to say. Great job!
Small thing. I just learned yesterday that his name is spelled Feynman. I'd been spelling it as Feinmann too.
@@johnfitzgerald8879 lol
That was one of the most approachable explanations I've ever seen. I hope that this is found by people who are interested in quantum gravity or the tension between relativity and quantum theory.
It is a pleasure watching your videos for those like me with no major math or physics background. So clear and easy to understand. So inspiring.
Thanks.
Nothing I have seen brought me closer to an understanding like this presentation. Thank you.
Best explanation of gravity I have ever heard. Gravity may not have a quantum explanation as it is not a force.
I've been binging these science videos recently and have been learning a lot about quantum mechanics, general relativity, and physics. Thanks so much for this great information
Want to think outside the box? 😮1st Page:
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2nd Page:
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3rd Page:
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Amazing video. You explain things with so much clarity and in such simple to understand terms. You have a deep knowledge and understanding this subject and I'm thankful you took the time to break it down so well.
Wonderful presentation ..
Knowing something and teaching or explaining something are completely different things!
I really loved your explanation
Thank you!
If you can't teach it you don't know it .
@@Number6_ Not true
@@BrazilianImperialist Very true
@@jeanbriones1190 Not everyone has the skill to teach. That's a skill all on its own.
@@enzop2835 "If you can't explain it simply, you don't understand it well enough." - Albert Einstein
Damn, great video dude, it's all stuff we all mostly know too but its the way you pieced it all together for a decent explanation is what stands out. Thanks Arvin, keep it up
Arvin, this explanation was simply fantastic. Like others have said, the coupling with illustrations was fantastic and by far the simplest explanation. Thank you!
Once again, another fantastic video. You've done so much to help the public understand science, Arvin. Thanks! The perfect balance of not over simplifying and not making it a tangled web of maths. You treat your viewers like intelligent people.
Thanks for that. Yes, I try to treat viewers as intelligent people who don't need to be coddled with oversimplifications.
@@ArvinAsh If quantum mechanics is the correct one, then what does quantum mechanics say about gravitational effect of electorns or how they affect spacetime?
Am I wrong to say that quantum mechanics say nothing about how the quantum particles affect spacetime? NOTHING AT ALL.
And yet we always say that GR is not the correct, but we keep on a pedestal the QM.
Very very concerned about the bias in favor of QM
@@theodorei.4278 I think not. See time mark 12:02 of the video.
The video presents the problem in a nice visual. Energy bends space-time and space-time directs movement of energy. Mass is, of course, energy. I think that is the point of the problem. Feynman was able to find a solution to the infinity of the states between combination and decay of particles by eliminating many. When space-time is added in, all those possible virtual particle interactions between combination and decay also affect space-time. I am not entirely sure of the precision of the diagram, but it does show the virtual particles as bending space-time.
Simply, an electron has mass. Mass curves space-time. But, see, that's not really science. Science is calculating how much spacetime is curved as a result of the total energy and mass. Clearly, all mass, from that of a black hole to that of an electron bends space-time into a sphere around it, at some radius. But there is the catch, at what radius would a photon orbit and electron? I would be inclined to believe that the radius is less than that of some effective radius of quantum uncertainty. But then again, that's where it becomes science.
There is no "bias". QM and GR are both well established theories. But it is important to understand what a scientific theory is as it consists of a sub-theories, pieces that have different levels of strength. A scientific theory is a mathematical model that specifies the equivalence between different properties of nature. It is capable of predicting the outcome of an experiment. Type I parts of a theory have been experimentally demonstrated to be absolutely factual. Type II parts predict things that can be experimentally tested. Type III parts are inferences that can't be proven by some experiment as nobody has a clue how to even go about testing for that. Type IV makes predictions that are considered a bit difficult to believe, like anytime the math leads to an infinity.
The current problem is that we can't get the equations of GR to link up to the equations of QM. But we know that both are correct in terms of the scale in which they have been measured. GR must emerge from some aspect of QM, just as molecules emerge from atoms, classical thermodynamics emerges from atoms and molecules.
@@johnfitzgerald8879 once more you say that GR must coincide with QM at the quantum level. Be careful of the words you are selecting and the order you put them together, because you might sound biased.
If you want to be neutral then you should say that GR must coincide with QM but also the other way around, I.e. QM must coincide with GR at the macroscopic level ( and I dont mean newtonian, I mean GR ). Which of course QM does not, because if from QM you could generate GR then the problem would have been solved and we wouldn't talk about this.
So to wrap up, at best you can say BOTH theories are incomplete and they need to merge from one another.
The video and you do not say that, you just assume that QM is the only well established theory and everything else must abide by this theory, which of course is not.
So better talk about "General-Relativize" (if that is even a word) QM and not only quantized GR.
@@theodorei.4278 There seems to be a general lack of detailed understanding of how a theory works. A theory, like QM and GR, any theory in science, Newtonian mechanics, thermodynamics, is not an all encompassing. There is a scale of factuality and deduction, extending off into a degree of speculation and even sensationalized headlines. Knowing the difference is important. Generalized, sweeping, inspecific, fault finding statements of "It's all wrong and doesn't work cuz this" isn't functional.
This video is fantastic, well done! Gives an easy to understand frame work of the issue and what scientists are actually working on for a solution. Great graphics, too!
Love your videos. I read Wikipedia on these subjects a lot but sometimes a video, an animation, or just your patient laying out of the issues is so much easier to grasp than pages of mathematical machinery to a layperson like me. Thanks a lot Arvin and crew!
You're a great teacher. Thanks for making this!
Brilliant Arvin Ash as always - the reference to Wonderium even better - would strongly recommend if you can thread through your videos as a lecture series (over last few years) under different titles, that in itself too would be a great reference - amazing - appreciable efforts
He has a way. Almost as if I'm sitting around with friends and a couple beers saying whatever we think.
Wonderful video Arvin. Really helped me understand how complex gravity is.
Arvin, love the music selection! ❤ The subject matter is fantastic too!
Arvin Ash has some fabulous comtent. His upload about Maxwell's equations is amazing, too
Great video and very well explained 👏
This was really well explained from start to finish
Thank you for explaining this topic in such a simple way 👌
Amazing video. You made such a complex thing into something the every day person can somewhat understand. 10/10 GREAT JOB.
Looking at your animation of the double slit it made me think that a particle is an instantaneous "condensation" of the energy field foam into a point particle. I like this as a visualisation.
I have a friend that said once while smoked something in the direction of "of course, if you spend the energy of the particle to interact at one specific point, there's no more energy to be able to interact elsewhere". So serious.
Sort of like a how a wave crashes and the air and water at a moment are in a churn or mixing of the boundary layer (at fractally proportionate scales no less) only to coalesce into its separate constituent particles. Thus deciding its particle state. Literally from a wave function.
Nature speaks volumes if we stop and listen
You do an amazing job of describing these concepts, Arvin. Thanks! Dave J
Many thanks. Glad you enjoyed it!
Thank you for uploading this.
Best illustration and way of explaining qm
I have seen so far.
Thank you
Perfect visual representations along with the explanations.
Great explanation! Oddly enough, I'm reading about this very topic right now in Sean Carroll's "Something Deeply Hidden". I've peeked ahead and the next chapter has Feynman diagrams in it so I think there's a well-trodden path being followed here (I know that Sean is also going to discuss entanglement as the basis of proximity though, which is the bit that I'm curious about).
That's a good book. I'v read it, and even did an interview with Sean on my channel.
@@ArvinAsh I saw that interview, yes! His podcast is also great: he interviews some incredibly interesting and informative people.
This could be the best Video ever created in the universe. I'm not even joking. The most important problem, presented so that everybody can understand the basics. Also it's a peace of art.
Two things I do when watching Arvin speak:
1. Slow my watching speed to normal from 2x.
2. Constantly anxiously checking timeline if the video is not over
Such the power of soothing voice and simple explanations of complex topics. 🙏🏾
Arvin I rhumbly equest you to open a channel in Hindi, translate same content, so that a large number of viewers.from remote villages in India gets Science in its most accurately discussed form. They are mugging up Bhors model, yet cracking IITs.
Awesome information…..
I listen to your talks a lot….. you’re an excellent teacher (:
Excellent video Arvin. Really interesting. Regarding the disparity between the General Theory of Relativity and Quantum Mechanics (and I'm not a physicist and only have a very basic understanding of both), but relating particularly to the discussion on infinites and wave theory, could it be as simple as it doesn't matter what form the particle is - electron, proton, neutron, meson, quark, etc - it's simply the aggregate mass of that 'system' (or quantum object) if you have both particle and wave? Sorry if I'm completely off
I have never heard it explained like this. Thank you, it makes much more sense now. I think?
You helped me understand "renormalisation" for the very first time... great!
that explanation is really awesome
Your wonderful videos never cease to amaze me. Describing the indescribable is a tough assignment, and doing it with a language most of us don't speak. Fantastic! Thank you!
For anyone who's lost, the first question should be "Wth is Space Time, anyways?" Well, Let me help.
Space = Meters
Time = Seconds
Force = Meters/seconds squared.
The squaring of seconds makes it a curve on le graph.
Tada, Forces = Space Time Curvature. It's literally just a more confusing term to use to make everyone feel dumb
Welcome to Einstein did nothing useful 101 ( and anyone hero worshipping him is weird because ykno, he abused his wife who probably did the math and actual science for him, then he left her for his cousin. What a charming "genius")
I've tried for years to understand what they say (when we try to reconcile quantum mechanics with gravity, things go to infinity) but I didn't understand it, I wish I could see it in mathematical equations to understand it more
Also, I hope to understand the meaning of their saying ( gravity is non-normalization) with mathematical equations
thank you my friend
Big like for your big efforts!!
This video explains different interesting topics and their relationships in a very simply way. Thank you for that.
Quantum gravity is my future field of research. I intend to solve it, or die trying.
Hello from Kazakhstan. It is interesting that the highest theoretical physics, cosmology rests on one result of the experiment, we do not argue with such an outcome. But you can do the experiment in a new way and get even more additional results.
To test the modern theory, Michelson Morley's experiment gives the necessary results by 50%, with the experience of Zhavlan MASER, you can get all 97%. The Michelson-Morley experiment should use a solid-state continuous MASER, developed in England in 2018, as a light source. This experience can be used inside the vehicle while it is moving to determine the vehicle's speed relative to the DGF of the Earth's dominant gravitational field. The installation will almost also work as a traffic police radar, that is, the results will exceed the interference..
If you are at rest inside the DGP, then relative to you the speed of light is constant. If you are in motion in the DGF, then you break the symmetry and break the speed constant of light with respect to yourself. DGF - Dominant Gravitational Field.
When Arvin talk about his sponsors, his face changes with a bit of smile. 😆 I got you.
Love your videos.
WoW !!!
You explain so well 👏🏻👏🏻👏🏻👏🏻👏🏻
Outstanding, Arvin! As always.
This was so great I may be getting greedy, but I'll ask anyway: Would it be possible to go into more detail on how Feynman, et al, canceled infinities as part of renormalization?
@Opterongeek Or it's a mathematical tool by which to facilitate accurate calculations, one of the two.
@Opterongeek Are you saying that this gives you a right of ownership? Since you wrote some of these variables down, as you say, nobody else gets to comment on them, they're yours?
@Opterongeek How have all of us been treating you?
Thank you for this insightful video! I have one suggestion though. As you say, among people without a background in physics, one of the most common misunderstandings is that fundamental particles look like little billiard balls.
Wouldn’t it be better to use a random image/object, like a watermelon or a basketball or something, to make it clear that it is just placeholder an not an actual depiction?
I have no background in physics myself (just interested in learning about it), and it took me a while to realize that particles don’t really ‘look’ like anything in the classical sense of the word, and that depicitions are always schematic. In part this is because it’s kind of difficult to wrap your head around, but it was also because most science communicators keep using the same image of colored balls orbiting each other.
Thanks. It was Explained in a simple way… very hard for this kind of subject
When oscillating in a vacuum, the electromagnetic field at the nodes - Forms gravitational quanta, carrying with them the speed of light - This can be determined using a mobile, new - Michelson-Morley experiment, assembled from two non-circular fiber-optic gyroscopes - 6000. Kazakhstan device
Fantastic video. One thing I missed was how renormalization works. When learning about infinite divergent sums, I've learned of several different summation methods, such as Cesaro, Ramanujan summation and others. If I remember correctly, it was specifically Ramanujan summation that was used to renormalise sums in QFT. I'm curious how exactly it's used and in what specific problems it's used to remove infinities in QFT?
I don't know the exact mathematical terminology, but basically whenever you have a Feynman diagram with a loop you have to integrate over the possible momentum going around the loop. And this can go up to infinite momentum, which tends to cause the integrals to blow up. But what you can do is find another matching diagram which gives a contribution with the opposite sign, and then cancel out the infinities from the two diagrams. In practice what you usually do is put in a maximum momentum cutoff for these loops to keep everything finite, and then when you add the contributions from all the possible diagrams all the terms depending on the cutoff should cancel out.
@@Reddles37 Why does this fail for gravity?
Do we have to rule out the possibility that the space-time continuum is actually a wave form?.. If so, why? Isn't it the easiest way to explain the various fluctuations ascribed to various forces -and gravity too, as well?
Your videos, Arvin Ash, are surely "food for brains" and I thank you about it! Looking forward for your next, but I'd appreciate any reply to my question, too!
This explained the idea of the Graviton very well. I always thought, "It's just curvature! Curves are continuous!" But this showed me the biggest flaw: Superpositions! Where would the gravity of a quantum object emanate from? It could average out, but then measuring a quantum state could remove a gravity well from far away, which doesn't seem quite right. Thanks Arvin!
Once again, Mr. Ash, you have made clear to me what I've never quite been able to understand watching other videos. What the conflict is with relativity and the quantum world. Where the hell is it's gravitational effect. Well done. Again. No, very well done.....my friend.
I'm interested to know why we can't apply renormalization to gravity. My understanding is that renormalization discounts most virtual particle interactions because their statistical likelihood is so tiny they barely have any impact on the final result. Why doesn't that extend to those interactions' effects on space-time?
Renormalization might not be necessary if you have better number systems than the real numbers. In theory you can make a number line that can fit a copy of itself between any two (distinct)numbers without any distortion (just zoom-like rescaling), even between two numbers that are so close that their distance is smaller than any positive real number. That would allow you to fit the entire universe into a single point (well, in real numbers it would be a point, and from outside it would look like a point), but you could still walk around inside it, possibly not even noticing anything unusual.
Love how my knee jerk reaction is "I can solve this!".
Really shows how little I know.
Best explanation of the gravity of the situation.
I'm here again Arvin. Thanks for the explaining note. This looks very good. Cap.
Welcome back Captain!
@@ArvinAsh That was a great video. I feel you need a greater audience. I endeavour to spread the word. Thanks Arvin. Great to be back.
Thanks Arvin, I have asked that question for a very long time. How can gravity have a particle when its curvature? And finally you answered it and i totally understand. Which is saying alot about your skills. Im just going to say it, man i love you.😥
Thanks buddy. Love you back.
Hey why all planets are circular . Because they are supposed to be due to curvature of space time
Again another beautiful piece, Thank you.
Wow! What an excellent presentation in a way I can understand!
Ok I have a question that probably is dumb but still it's stuck in my mind... What happens if we consider the mass/energy spread out along the wave function?
The problem is that there is no mathematical description of that. The wavefunction does not say that the properties of the object are spread out. Its norm only depicts the probabilities of what we we might find if we measure it.
Excellent Explained
This is probably the first explanation of the issues with gravity in GR & QP that not only mentioned that in GR gravity is not a force, but also went into a detailed explanation of what that meant and also covered some of the attempts at solutions to those issues.
Very well laid out discussion from beginning to end.
My thinking has always been that the most obvious reason that GR and Quantum Physics don't mesh is Time.
It's very prominent in GR and almost completely absent from QP.
It's all about space-time in GR.
In QP, there is no "time carrying" particle, but no one seems to notice.
Time is a dimensional aspect of where particles, or more precisely, localized anomalies in quantum fields, exist.
Without the dimension of time, I don't think you can have gravity, can you?
And while we're at it, what, exactly, are the fields of quantum field theory? They seem to be a more scientific sounding concept of the aether that Aristotle or Descartes described.
They seem to simply be taken for granted that they exist, and that's all.
Perhaps you could make a video describing that more thoroughly, too?
Thanks again for your very well-made videos.
you explain complex physics so simply well thank you please sir
Thank you Arvin sir, you make my understanding simple by putting Feyman Diagram into the explanation of gravity.
Beautifully illuminating representation of the problem. Also, I think I’ve figured it out. 😊
Share it with us please.
Good luck boy then
Great content! Thanks 🙏
When quantizing gravity physicists forget that at the quantum scale everything is probabilistic so you have to multiply each of those possibilities by its corresponding probability to get the expectation value.
I think trying to reconcile QM and GR is the wrong approach. QM is all about *matter-matter interactions* while GR is all about *matter-spacetime interactions* They're completely different things. Asking why the two theories aren't compatible is like asking why a ball dropped to the floor bounces but the same ball dropped in water sinks instead of bouncing.
Fluid dynamics
@@Casperdghost618 What?
Arvin, great video! Although pretty much all of your videos are very well done and informative, every now and then you conjure up one of a kind pinnacle performances. This video when coupled with the Loop Quantum Gravity (LQG) vs. String theory ST video is a double grand slam. I have watched/read countless videos/articles purporting to explain where it is that General Relativity (GR) and Quantum Mechanics (QM) are incompatible, most with condescending pats on the head and marginally appropriate metaphors whose connection with the topic is often more confusing than the original question. I mostly come away with a slightly out of focus understanding and the vague feeling that the answer was somehow just out of reach, like with QM itself. Maybe the answers were obvious to others, but having watched your two videos several times, I conclude, you have put your finger precisely on the jugular, explicitly listing concrete issues with crystal clear language and animation, and at a perfect level of abstraction. The fog is lifted, as one might experience the world anew following cataract surgery.
1. A QM wave (before measurement) is probabilistically dispersed in space, while in GR, gravitational sources are localized.
2. QM operates against the fabric of space-time while gravity in GR is the warpage of the fabric of space-time.
3. And, woven into the discussion, QM is quantized while GR is continuous (analog).
Personally, I suspect that the fundamental problem is with the continuous space postulate of GR. A solution to Zeno's various paradoxes supports the position that space is quantized as is clearly illustrated in the following video:
czcams.com/video/iU59S5JDpSU/video.html
Finally, midway through I picked up on the intuition that that final solution lies with somehow combining LQG and ST, with the strings, rather than the loops, perhaps forming the fabric of space-time.
Excellent job! Thank you very much!
Jack Hill+
Wouldn't that fabric itself require a background?
it is all just a simulation, and quantum phenomena such as planck lenghts etc are just limitation of floating point calculations
@@goldwhitedragon I can convince myself that the loops/strings would be the background with "nothing" beyond that, but this is just a mental model of how reality might be. And, envisioning exactly what the "nothing" would be is difficult at best and maybe impossible for humans to comprehend.
@@gierdziui9003 I agree that the simulation hypothesis is more likely than most people are willing to concede. And in the current era, most simulations are produced on digital computers so this is a natural metaphor for our age. But these simulations don't directly influence physical reality without a physical interface, i.e. airplane simulations don't actually fly nor do simulated tornados blow away buildings. Personally, I believe that infinities are a logical impossibility, at least in certain situations (i.e. Zeno's paradoxes or for physical movement generally), so that having a minimal unit of space-time is a logical requirement rather than a technical or mathematical issue.
@@jackhill2765 Yes, I agree that digital simulations are probably not a 1:1 transformation nor explanation why our world seems to have such boundaries - reality might be infinitely more complex than our computer simulations.
Things I think about the most lately are how exactly someone can determine they actually are in a simulation? Let's say i play a computer game and for a moment get into the perspective of the player. Let's assume the game is minecraft, for example. How can I determine that I am, in fact, in a simulated world? Looking for answers to this and by model-like analogy, I think we could try to answer quantum phenomena in simulation theory based research. So not really looking at our world as a digital simulation, but as "*a simulation*" and find out how that it is a simulation assuming we know how we can conclusively find this in games and other world symulators. For me, this is a really fascinating concept that I hope I will be able to research in the future. After all, finding the core of the simulation (if there is such) will automatically obsolete ALL current understanding in every field by essentialy comparing them to *magic that somehow works* instead of ojr current, really weird assumption, that math is even formulated the right way. I hope you get the point :D
thanks for explaining what "won't quantify" means as it's so often invoked in conversation without explanation.
This helps a lot. Thank you.
Why gravity must work at small scales ? Is it an assumption tht it should ?Also tht thing/assumption about cumulative effects must work at large scales ?
Because if it didn't, then how can we say it's a broad explanation of the universe? This is how theories must be, broad, unified, and applicable at all situations, not just certain phenomena
Even if gravity didn’t work at small scales, you would still need a theory to explain the emergence of large scale gravitational effects.
precisely!
All this makes me think...That theories come out of conscious minds 🙏🏼
So one day Science must proceed into the inner subjective world 🙏🏼
It seems to me that subatomic particles expand into a very large area when they have to move and all that expanded blob is their gravity combined and when they hit something or are stationary, they are forced to contract into a single point again. That's the reason why the point where they form on collision can't be determined. because of the large expanded size they can have any of their parts move faster or slower and have it's shape change while traveling and whitchever part gets to have a larger density at the moment of impact, the rest of it's body contracts over there. It feel to me that subatomic particles act a little bit like cells but unlike cells and other solid macro scale matter, the subatomic particles have huge spaces of influece where they can contract and expand. If there is such a huge amount of space between an atomic nucleus and the electrons around it then that way of organising may be even more extreme at the smaller scale. And that also coincides with the way bodies at the huge scale work. The sun and the planet are tiny dots compared to the massive patches of space between them and yet if you were to look at a huge distance you kinda see galaxies as compact bodies with very little space inbetween stars. That's an illusion given by scale or distance.
This is such a great video
Gravity is how grounded you are and what wonderful weather you have you can always ask mother for rain if you need it, but she may already know if she can have access to listen
Around 10:00 you show an electron/positron pair annihilating and sending a photon on its way. After splitting into various virtual particle pairs that recombine it ends up splitting into a real electron/positron pair. Question: how does the photon “remember” that it’s supposed to end up splitting into an e/p pair and not some other particle/antiparticle pair?
What the photon splits into generally depends on the energy of the photon, so if it has more energy than an electron-positron pair, could could transform into a heavier particle pair, not just electrons.
Gravity seems to be very different from the other fundamental forces. Could it be that it resists quantization so stubbornly because it’s not a fundamental force? What if it’s an emergent phenomenon that only takes effect at larger scales? Has anyone ever measured the gravitational effect of a single particle? Just genuinely curious.
If it exist at larger scales it must have a microscopical explaination for sure, everything you see is the sum of the effects at smaller scales. I think it cannot be mesured because it is extremly small.
Gravity is in the fabric where force particles exist. It takes two to tango for gravity to show up. Gravity is a by-product altered in fabric where force particles enter.
You are incredible Arvin! You are cool and you explain so well!
It would be interesting to hear your take on the EP=EPR hypothesis. Interesting idea that space-time may be an emergent phenomenon of entanglement.
The theory that locations in spacetime are only next to each other because they're very tightly entangled leads to the concept that you can change what's next to a given patch of spacetime by entangling it with a remote part of spacetime. Vacuum energy is spacetime maintaining locality by entangling with neighbors. To create a portal you could entangle 2 photons, leave 1 at a location, goto a different location, then use the 2 photons to entangle spacetime and create a portal. And if you believe in Remote Viewing, it could be a read-only version of Remote Entanglement, where one part of spacetime (or the beings there) could affect another part of spacetime.
@@StephenGillie You can't transport information through entanglement, so these "entanglement wormholes" are supposed to be non-traversable.
@@AlexanderShamov It feels like there should be some way, as though we just haven't figured out a clever way yet. Like we measure Z for a 0 and "anti-Z" for 1, where "anti-Z" might be halfway between X and Y. Though since point particles act like they are spinning spheres, maybe it's mathematically impossible to determine how one will respond to a measurement.
The one thing I still can't get my head around, even at a basic level, is the existence of virtual particles.
Every time I try to read about them, the info always says they don't exist except in the maths to fill in supposed gaps.
But then some black hole papers have suggested that Hawking radiation comes out of the event horizon via virtual particles failing to annihilate with its anti-particle.
So do VP exist or what? It is really confusing.
Keep digging on the Hawking radiation, I have seen (or read) somewhere that it has nothing to do with virtual particles.
Astrophysicists have been measuring massive amounts of energy and matter flowing rapidly away from the supermassive black hole in the core of our galaxy for quite some time now. Hawking came up with his Hawking radiation claiming pairs of particles were emerging just outside the event horizon of a black hole to try and explain the energy and matter observed to be moving away from the Sgr A* while keeping general relativity afloat as the prevailing theory. However, if nothing is able to escape the gravity of a black hole then why would anything be able to escape? So basically Hawking radiation violates Einstein's equations on gravity. In reality they were both wrong.
They both neglected to include the action causing gravity in their equations. If they had included the action then the massive amounts of energy and particles streaming away from the supermassive black hole would have been easily explained.
Research pair production theory. The particles don't come from nothing. When energy interacts with matter, external EM fields or comes to a rest relative to the body producing the EM field pairs of particles pop into existence. The energy according to the laws of conservation converts into elementary particles, a positive and negative particle. That's why it's called pair production because pairs of oppositely charged particles emerge out of the energy.
The virtual particle explanation of hawking radiation is just a simplification hawking came up with to explain it to laypeople, iirc he really regretted it for the confusion it caused. It is actually caused by (and this is yet another simplification) due relativity causing the measured zero point energy at the black hole and from an observer infinitely far away to be different. Hawking discovered it while trying to mix relativity with quantum mechanics and found Hawking radiation to be one of the consequences.
I understood that Hawking Radiation was virtual particles as well. Perhaps that has been updated.
Here is where we have to be careful. There is science established by experiment that is well established as being real. We can see the tracks left by particles in a cloud chamber and from collisions of the LHC and others. And, we have a successful theory that predicted them. There is an issue, we must take care of, that the theory is only solid on the grounds of what has been successfully observed. Anything else it predicts is not established and the theory could have some detail wrong. Theories of prediction are, as a requirement, simplified models of nature. The theories have their mathematical parts and mathematical models have a habit of producing equations where things go to infinity. Standard physics does this in places where there are oscillations. The equations would tell us that voltages go to infinity, bridges in the wind are driven to infinite amplitude swings, etc. That is generally where things blow up as nature gets more complicated than the basic theory. As far as we know, infinity exists only in mathematics. So far, aside from things just blowing up, Einstein showed that velocity doesn't go to infinity, only up to light speed. Einstein's General Relativity was curious in it's prediction of singularities when piling up more and more mass. The resistance to accept that is reasonable as we know nature abhors an infinity. Stars do resist infinities in nature as they start to collapse, they explode. That, despite their struggle against it, blackholes do exist and it is quite remarkable. Still, we actually don't know what is inside a black hole, so we don't know that it validates the singularity, only the run up to one.
The problem for us is we need to distinguish between what part of the theory has been measured to be real and what part is an unvalidated prediction of an otherwise well validated theory. In particle physics, there is some complaint of the theory predicting particles that don't exist. That's a tough logic statement there because simply we can only know what we found, not what we did not find. I would have to review the CZcams video that highlights this.
Heisenberg's uncertainty is clearly true, we have experimental evidence of it, right? Well, it explains a lot, that's for sure. And being what it is, the undeniable inference is that virtual particles blip in and out of existence. Have we measured them? And is there, perhaps, a difference between the context of a black hole and the context of Feynman particle transformations? The video says, "an infinite number of combinations of interactions".
And this is why the research still goes on. When it comes to physics, there are the two parts of it, what it is proven to predict properly and what is predicted that isn't experimentally verified. Really, what theoretical physicist are doing is trying to predict what the experimenters should be doing next. Whatever hasn't been proven to be wrong in a theory that successfully predicts everything that has been tested is assumed to be true until proven otherwise. The theory continues to be developed until it can predict something that experimenters can test for so the theory can be further validated or some element proven wrong.
Christian Thom's comment seems to suggest that virtual particles haven't been show to be real. Perhaps there is another explanation of Hawking Radiation that doesn't depend on VPs.
And while this idea of VPs in Feynman physics is certainly justified by quantum uncertainty, I don't know that has been proven. And seeing as it yields an infinite number of VPs and all these have to be accounted for and then renormalization applied to get rid of it, this seems to be an issue. And now we know that adding gravity in makes it worse.
Welp, there's what I got until encountering the usual "Brain.exe has stopped". Could be worse, I could be completely unable to remember I wrote it, like 10 Second Tom and 30 Second Clive.
@@johnfitzgerald8879 I liked your insights into this interesting subject. If you've ever watched Sabine Hossenfelder's videos you know that she acknowledged that particle physicists will say that a particle exists if it is useful to explain an observation. You are not going to see any traces of bosons or quarks in any cloud chamber.
I also don't like all the emphasis put on obscure experimental results like the double slit. The results are beyond weird but easily observed, so while "something" is happening there, I don't think this warrants so many outlandish interpretations. It's just an oddity of nature that you can conjure in this artificial situation in a lab. An example of taking a very structured experiment way too far concerns causation. You can isolate and explore the effects of one variable by controlling everything else, but this doesn't happen in nature. Outside of a lab, everything causes everything, but you will still have scientists try to say that their one variable "determines" what happens. They then use their memory to concoct intricate "chains of causation" that they believe are real as opposed to imaginary.
I see much of physics now consisting of these sorts of imaginary theories that are only loosely based on obscure experimental results that might not mean anything.
I’ve watched lots of videos and read Brian Greene’s books, and this is The Best description of the problem with gravity.
what a great video, incredibly well explained