It got serious for me at stage 4. I get inertia, I get the whole 'ball in the middle of a sheet' example, and I get that time is a series of snap shots, but WHY any of that stuff happens is totally beyond me.
3:20 is my favorite part because I love how he lists off the numerous observations that validate the model. It's the observations that make this a physics theory instead of just mathematics.
I've been studying this for years. This is by far one of the most accurate videos on the field. Level seven is the strict construction of the equations and their solution throughout classical differential geometry, tensor calculus, complex analysis, linear algebra, ordinary differential equations, partial differential equations and special functions among the classical fields. This is simply a compendium of what this is in its entirety. This is the field of Riemann Manifolds.
This is the kind of stuff that originally bothered me about science: that you have to keep coming back to a topic in order to learn the next stage as your level of understanding increased. Now, as a biology teacher, it is one of the things that makes science, and learning in general, fun. "Remember how you learned in middle school that plants make energy from sunlight? Well it's actually more complicated than that." "Remember how you learned in high school that plants make monosaccharides from sunlight? Well it's actually more complicated than that."
I take the view that this is because everything in science is an approximation. The approximations get more accurate, Newtonian gravity, general relativity, whatever quantum gravity might be, etc. but they never become statements about the state of being of nature. Only nature itself a knows how nature is. And science merely concerns what we can say about nature.
@@Cosmalano completely agree with your statement about us never knowing the absolute truth/ exact way something works. Personally, I would switch "nature" for "God" but to each their own.
@@tattwa1 Aw c'mon. God is just the standard thing we stuff in all the gaps of our knowledge. Each time we learn something new, we yank the god out of that gap and stuff it into the next.
Just ignore the word salad and listen to the stuff he says after that, it makes more sense; I feel he shouldn't have led with the proper scientific name
@Swastik Majumder nice! I also want to get into an IISER. I am going to give the entrance exam this year (again, as I didn't clear it last year), and I hope to get into an IISER!
@@pulkitmohta8964 I'm preparing for JEE Last year I qualified both exams but didn't took admission as I didn't got rank under 2000 I didn't took any formal coaching last time so I dropped and preparing
Not neccesarily. Anyone with a class in GR can understand most of it. PhD in Theoretical Physics is much more sophisticated it develops on already developed GR and Quantum fields theory for example trying to develop parts of string theory.
Ricci tensors, curvature scalars, antisymmetric tensor fields, Grassmann variables, Christoffel coefficients, diffeomorphism invariance, isotropic pressure in vacuum states with cosmological energy densities, nonlinearity distinguishment from e.g. Schrodinger's equation and Levi-Civita symbols.
@@TheShamansQuestion He wants to understand the things which he doesn't understand while neglecting the others. You want to understand the things you already understand but in as much more depth as possible while neglecting others..
@@srajanverma9064 very nice 👌🏻 you're right my want is there but I'd de-emphasise "want" and say it's more once I get knowledge, I can understand it deeply (and because I want to/go for depth), plus a sceptical, Socratic element of "I know that I know nothing" (but that is probably more relevant to "understanding" in this case, so might be wrong on that)
It takes at least a few hours to derive even the simplest solution (Schwarzschild solution) to the EFE by hand. A set of 10 highly coupled nonlinear differential equations makes even the most brilliant mathematicians cringe.
I once had a professor that said "Everyone should curl up with a warm drink and spend an evening deriving the Einstein Tensor for the FLRW metric by hand at some point in their life". Needless to say, I haven't done that yet.
3:44 That is NOT "the black hole at the center of the Milky Way" (Sagittarius A*) that is the black hole at the center of galaxy M87. They did consider imaging Sagittarius A*, but that was ultimately not their target. Edit: It turns out I do not know how to spell "Sagittarius."
@@GrayLynch No, that is a correction to a mistake they made in the video. In no way did I suggest that the video wasn't worth watching or is otherwise "ruined" as a result of their mistake; but if it were me and I made a mistake in a science education video, I would hope I would be corrected.
I had a discussion with a friend who's into conspiracy stuff, for shits and giggles mostly mind you, about how in a very special way, yes, you can say that the earth is flat. Twas a fun talk haha
It is just utterly mind blowing how much much Einstein figured out, in the era before powerful computers and such. An elegant set of equations that allow us to predict the past and future of the fucking universe??? Curvature of space time??? Time dilation??? I just cannot wrap my head around it !
This is to show difference between classical relativity having galilean transformation and theory of relativity or relativity having lorentz transformation. The wave equation is given by, c² d²/dr² = d²/dt², where c is speed of wave. Its possible solution is sinusoidal function, omitting amplitude and type of function here stating its phase function □ which determine value of wave function at given time and distance coordintaes is, □ = kr - wt Frame S is at rest and S' moving with speed v relative to S. Then solution of wave equation having phase as, □ = kr' - wt', for S'. As phase is constant for wave moving in frame, then for r'1, t'1 and r'2, t'2 phase difference is, □2-□1 = k(r'2-r'1) - w(t'2-t'1) = k◇r' - w◇t'=0 => ◇r'/◇t' = w/k = c' For wave in S' observed by S according to classical relativity, k◇r - w◇t = k(◇r' + v◇t') - k(c' + v)◇t' = 0, where w = kc' and r = r' + vt', t = t' So, ◇r/◇t = ◇r'/◇t' = w/k = c' = c Thus speed of wave in S' observed by S' and S is same according to galilean transformation. Now if phase of wave from moving source S' emitted wave and observed in S is given by, □ = kr - kct = kr - k(c' + v)t, where c = c' + v, according to galilean transformation and c' is speed of wave in S' or with respect to source and c is speed of wave in S or to observer at rest. Thus, w = w' + kv, where w' is frequency of wave emitted from source and w is frequency of wave observed by observer, this is doppler effect. So classical relativity inherently have doppler effect. Now according to theory of relativity having lorentz transformation, phase difference of wave in S' observed by S' is given by, □2 - □1 = k◇r' - w◇t' = 0 ==> ◇r'/◇t' = w/k = c' Phase difference of wave in S' observed by S is given by, k◇r - w◇t = k(◇r' + v◇t') - kc'(◇t' + v◇r'/c²) This shows that speed of wave is not same for both observers and in case of light it is, c = c' - v. For phase difference of wave emitting from moving source S' and observed in S at rest is, k◇r - kc'◇t ==> c = c' Thus wavefront of wave in relative measurement is spherical in classical relativity and elliptical as per theory of relativity. But wavefront of wave for moving source is spherical in theory of relativity and elliptical in classical relativity. Important thing is that due to spherical wavefront inspite of moving source, relative speed doesnt remain constant and heavenly bodies seems receeding. While wave front is elliptical in classical relativity so, speed of source is accounted. Also this is the reason why circular orbit seems elliptical.
1:20 that's a nice globe you got there. Me, an intellectual: actually, it's a pseudo-Riemannian manifold with Lorentzian signature,... But thank you! 😊
At the 3 minute mark I had to pause because I just got hit extraordinarily hard by the re-realization of the nature of existance and our place within existance itself. It was like a philosophical seizure that caused me to sit back in my chair and stare at the ceiling in AWE of whatever the hell it was I just experienced.
Great video. Your videos got me interested in general relativity six years ago, and to this day I’m still trying to become a mathematical physicist so I can study quantum gravity. ❤️
Penrose and Hammeroff's Orch OR is a pretty good candidate for a theory of everything. Where gravity causes an objective (probabilistic) collapse of superpositions in space(time), as Epicurus predicted in ancient Greece, these objective "chance swerves" explain conciousness (electron oscillations inside nueronal microtubles) and why all things don't free fall -- in other words, there is (and always has been) a connection between gravity and superposition. Namely, that g-forces snap superpositions into one (inertial) position in the same way that wings of a plane snap people up and keep them flying in the air rather than free falling.
So good. I've tried so many times to explain the way the ground pushes you away from a straight line and I've never once passed understanding across. Now I can link to this video with the clear diagram, and maybe in future, I'll succeed in showing the beauty of this idea to others.
@@ngiorgos I think Vsauce's "Which way is down" video does a pretty good job. It gets more obtuse near the end and doesn't even get as high-level as this, but I like it a lot.
@@TheBlueWizzrobe Yes, I loved that! And Veritasium's video "why gravity is not a force" is also an excellent presentation. But the best they can do is give an overview of the theory and some intuitive explanations. The maths are still untouchable, unfortunately.
The reason that this is difficult to comprehend is because we think of objects as travelling though spacetime, rather than being products OF spacetime. So, instead of you being a constant, travelling through an environment, what's really happening is the quantum environment manifests as the quanta that together make particles, conserving energy and momentum, effectively passing energy from one bit of spacetime to the next, rather like pixels that manifest as moving images. When these individual 'pixels' (or strings / membranes / e8 crystals / whatever they turn out to be) act they exert a pull on the fabric of spacetime, meaning that when many act together the pull is greater, and this creates the effect we know as gravity.
This is how I understand the shape of the Earth, in as simple a language as possible - Look at the Planet Earth as a sphere from outside, from inside it's a diameter...we're in the middle, the sky is the top, the bottom is the ground level area....the Earth goes round but easily seen moving in a straight line but somewhat curvy (if that makes sense). When the Earth rotates in space, different continents experience changes in the atmosphere like darkness, sun/solar radiation etc but, we only realise that, by looking at the sky when it changes.
I have been subscribed to this channel for quite some time now, I initially got interested because of my great physics teacher in high school. Back then I did not understand most of the videos at a deeper level (so the primary target audience). After 3 1/2 years of studying physics, I have my GR exam on monday and can happily say: I knew everything in this video! And it makes me glad to finally be at a point where I do understand this stuff at a deeper level. It took quite some time, but I got there. Of course I am still just beginning to be a physicist and there is MUCH I don't know yet and MUCH and I don't know that I don't know yet. And I am excited and looking forward to finding it out!
@@aemmelpear5788 Thanks. I'll write a program that simulates a non-linear mechanical system and analyse it's behaviour. What system in precise isn't clear yet. Writing simulations in non-linear physics is pretty much the profession I want to finde myself in some day.
As a physics major heading into my sophomore year, the feeling I get watching this video is roughly akin to the feeling I get at the top of the first hill on a roller coaster as I stare down the straight-vertical track…
Cool concept for a video. I especially enjoyed the "level 1 again" explanation of people's personal experience of gravity on earth in terms of your GR explanation.
Ricci tensors, curvature scalars, antisymmetric tensor fields, Grassmann variables, Christoffel coefficients, diffeomorphism invariance, isotropic pressure in vacuum states with cosmological energy densities, pseudo-Riemannian manifolds, nonlinearity distinguishment from e.g. Schrodinger's equation and Levi-Civita symbols.
Cool Video It's pretty simple to illustrate that standing motionless on the surface of the earth, your "straightest line through space time" runs through the top of your head, out your feet and straight to the center of the core. The 'weight' you feel is your body being in constant deceleration from its fall being blocked by all the matter beneath your feet. Another interesting thing about general relativity; if you put a clock on the surface and one at the core, the clock at the core would run more slowly as it is at the deepest part of the gravity well. For a body in rotation, like the earth, this variance in clock time produces a core which tears free of the surrounding strata and spins ahead. We call it a 'super rotating core' and it's what produces our electromagnetic field. It's General Relativistic Acceleration in the spin direction.
Why Euclidean geometry is general case and differential geometry is special case, which they say otherwise. Take an example of surface of sphere so radius become constant. Now line element is given by, ds² = g(ij)dx(i)dx(j) = r²d□² + r²sin²□d○², where □ is azimuthal angle or angle with one fixed axis of Euclidean space from 0 to pi, and ○ is polar angle or angle around centre of circle whose radius is projected by □. In sphere line element is given by fixed radius and fixed azimuthal angle, □. That is given by, ds = r×sin□d○ But it is good for fixed □, like arc of great circle at equator or small circle having fixed latitude. If there is arc part of great circle other than equator, the above relation can't calculate length. That is its azimuthal axis is tilted by some angle. Even if one previously transformed rectangular coordinates into spherical, it didn't calculate. To calculate above arclength, one has to use rotation matrix or change coordinates in Euclidean space or rectangular coordinates of plane having azimuthal axis. This shows that what they publicise that metric tensor free from coordinates is untrue. Problems are specific and they can't be generalized when speaking of geometrical measurements. Euclidean geometry is basis of space because it is not closed like other, so Euclidean geometry is generalized form and differential geometry is specific depends upon problem or surface encountered.
Thanks for summing all that up in a short video. I've seen a lot of videos explaining GR/SR on different "levels" and this gives me a nice feel on where I stand in my understanding of the subject.
I listened to a Great Courses lesson back in the 90’s and they completely left out the spacetime concepts of the second half of the video but said that at the quantum level special relativity rules still applied. So much has changed since just the 90’s. (Hard to believe the course was recorded nearly 30 years ago)
Just finished taking general relativity this quarter that passed, and I can honestly say that this is the hardest topic I've seen so far in my physics career, but also the most enjoyable.
3:41, correction: the famous photo of a black hole was from the supermassive black hole in the center of galaxy Messier 87 in the Virgo cluster (the Milky Way is part of this cluster). The black hole in the center of the Milky Way is not directly observable, and about a 1000x smaller than the one photographed in M87. Great minute summary of general relativity though!
so if space and time form a single geometry and we move in a certain direction in time, that means there is no force pushing us in either way on time axis. so if we can be pushed backwards or forwards in time axis...
You know what the insanely insane (and awesome) part of this video this? THERE'S MORE LEVELS! (For reference, I think I'm at 6.5, or at least between that and level 7. The idea of manifolds and tensors is something I have yet to understand, but I understood the rest of Level 7).
Him just throwing experimental proof after proof after proof of the theory of relativity and that it is genuinely true non-stop for so long and you're just thinking "Okay, enough examples, it's true" and he has as many more to mention; it just goes to so.
And this is why things get so specialized as you get higher in education. Monke brain no good at figuring everything out. Maybe one small thing, and have to spend a lifetime on it.
A year ago I could only understand upto level 3, but now after a year I can understand level 6 and 7 :D now I need to learn lots of differential geoemtry and tensor calculus and learn how to solve the einstien field equations
The picture of a black hole at 3:41 was not the black hole in our galaxy (Milky Way). It was in fact a picture of the black hole which is located in the most nearby galaxy (Messier 87). They couldn't make a picture of the black hole in our Milky Way, because it was too close and there was a lot of light pollution.
3:41 - You talked about direct imaging of the black hole in the center of our galaxy, but showed the black hole at the center of Galaxy M87 (a completely different galaxy) that was actually imaged. You might want to correct that.
From curve of matter irradiation of electromagnetic wave from cavity oscillator, Wein's displacement law shows at given temperature, frequency of maximum interaction of energy is at particular frequency. This means that there are no integral multiple of energy exchange as proposed in model of a particle in a rigid potential wall or box. So a given system can interact at multiple energy level is incorrect. Meaning of standing wave is equivalent to resonant frequency and that is characterstic of system. Any change in characterstic value is change in elements of system, thus a given frequency value can interact with given system. Mathematically it is possible that solution of differential equation permits integral multiple solution, but for fixed constraints of system only one is solution depending upon boundary conditions. So a given quantum system cant have multiple energy or quantum states. Further interpretations of quantum mechanics on some other time.
The final solution is the observation of the size and it's infinite expansion or constriction, for it is assumed anything can be infinitly large or infinitly small. This is the defining dimension that describes and encompasses both general and quantum theory.
My only problem with the end there was it seemed like the solution we are working towards is a very "in the box" one, like working harder not smarter. Wanted to use that as a jump point (not criticizing, I actually love it was there, gives something to talk about). If anything, the existence of Einstein's theory shows us maybe the way to go about creating theories is truly thinking outside the box (the box being our firm but unimaginative perspectives). I'm reading his book now (translated by Robbert W. Lawson, D.Sc. and you can really see how he came to the making of the theory. Not by trying to connect everything together like lines in a plane in a certain co-ordinate system, but instead by asking something like (am I even in a plane? Why am I so certain of the concept?). Question literally every concept we adhere to as true (like how he goes on about the different coordinate systems throughout time that largely base their "truths" on made up preconceptions), he talks about it literally in the first couple of paragraphs. As he says, "The important thing is to not stop questioning. Curiosity has its own reason for existing." The moment we accept whatever truths we're given by authorities or others, we succumb to its limitations instead of the limitless power that is our own imagination. "Imagination is more important than knowledge. Knowledge is limited. Imagination encircles the world." "Unthinking respect for authority is the greatest enemy of truth." So if we don't learn to take a step out of our perspective, we're kinda doomed to make slow, receding progress instead of a major jump towards reality. Fantastic video, very very humble in delivery and knowledgeable in the field.
Me: "I just finished a phD in theoretical physics and have a pretty solid understanding of general relativity. I think I know a lot about gravity now." Henry: "Think again."
Sun is emitting light and hot bodies glow light. But spectrum of sun is continuous which can be observed with crystal or cd. Different colors are in thick bands and not thin line. So how energy is quantized in hot solid bodies. By quantization means different colors are separated by dark regions which is not observed. Temperature of body can be calculated by light emitting from body of different colors and they do integration which is for continuous function. A circle is locus of points which are equidistant from a point called as focus or centre. Joining of locus is curve, where points are discrete but curve or function is continuous. So, do circles are continuous or discrete, continuous means curve is smooth. Similarly calculus is done with discretization of interval but on continuous function. Yes, quantum mechanics shows that wave seems as continuous but made of discrete small particles, operated as smooth. Similarly interaction of energy and matter is participated by discrete particles known as atoms but there is no restriction on amount of matter and energy, continuous.
@@justkirb6955 The "Einstein phenomenon" is a hoax, a pure propaganda. It's not hard to see how. Here's the short rundown. Special theory of relativity is the theory of transformations on a quasi-Euclidean space. More specifically, the spacetime is the Minkowski spacetime, and the transformations that leave it invariant are the Poincare transformations, the homogeneous version of which is known as the Lorentz transformations. One consequence of these transformations is the Lorentz-Fitzgerald length contraction, as well as the time dilation. That's it. This is special theory of relativity. Do notice that NONE of these bear Einstein's name. None. It's the work done by Minkowski, Lorentz, Poincare, and Fitzgerald. Oh, and Michaelson and Morley did the famous experiment. Now, general theory... when Einstein was toying with the Poisson equation on a flat background, having no idea whatsoever about the existence of Riemann manifolds, Nordstrom published a paper attempting to explain the motion of our moon by curving the spacetime and calculating everything with the Riemann formalism. All this happened before Einstein even heard about the existence of the Riemann differential geometry on curved spaces. What Einstein did was to consult his friend, mathematician Grossmann, who then lectured him on the Riemann spaces. One part there are the Biancchi relations, where the Biancchi tensor, made by contractions of the Riemann curvature tensor, is covariantly conserved, and these Biancchi relations serve as conservation equations of physics. This Biancchi tensor, Rij-Rgij/2, is nowadays known as the "Einstein tensor", even though it was Biancchi who invented it and proved the conservation. So, you see... it's a bloody hoax. If interested, I can check some books for references, for instance, "300 years of gravitation" has an interesting article on it. But, just by reviewing superficially these developments of relativity, one comes to immediately realize that Einstein had nothing to do with it. It's a hoax. The theory itself is correct, of course. But it has nothing to do with Einstein.
@@Kraflyn So basically, a classical instance of naming things wrongfully. I mean now that you explain it does make sense. Thank you for taking time out of your day to explain.
The R in FLRW is Robertson, not Robinson. Named for Howard Robertson, who among other things proved and reformulated the Heisenberg Uncertainty Principle.
What more observational anomaly than theory in relativistic gravitational theory is that inspite of big bang, orbits of planets are stable, atleast for many thousand years, also no detection of angular separation of stars. So meaning of stable orbits is that diagonal elements of mass-energy tensor are zero, because there is no expansion of orbits in radial direction. So i think there would no independent or orthogonal space-time coordinates, Theory could improve if they consider space and time coordinates differently. Time is part of space-time but not interfere length of coordinates of space. Thus space have 3 dimensions constituting volume and time is indicator of motion like orbit is clockwise or not and thus time in forward or backward direction. So space become a dimension and time another dimension of 2 dimensional space-time having volume. Other problem is that differential geometry or topology is construct based on idea or model which have flaws like length of curve is given in term of speed, so more curvature has less speed, but this is not as observed because distant orbits have same speed as nearer one, that is why different time period. It should be as, space is elongated and time is dilated so speed remain same, which is observable as distant orbits have bigger orbit and longer period. Relativistic gravitation was developed because in newtonian model not account for how everything starts from origin. It only account for stable orbit where orbital motion account for entropy or force in action. So what was before newtonian model could explain by relativistic gravity where diagonal energy have some value and cease at stability, it is transitory model.
At 3:42 you said we imaged the supermassive black hole at the center of the Milky Way. But we did not. As shown in your video above, we imaged M87 which is the supermassive black hole at the center of Messier 87.
Vantage point is, time measured of event happened in moving frame S' that was round trip of light in transverse direction of motion is t', c' = 2L/t' ---- (1), where L is length, and c' is speed of light in S' Relative time measured from rest frame S is t, c = 2L/t ---- (2) where c is speed of light in S From relativity, time is slow in S' measured from S so, t = t'# ---- (3), # is Lorentz factor From (2) and (3), c = 2L/(t'#) ---- (4), From (1) and (4), c = c'/# ---- (5) From (5), it is clear that speed of light, c in S is not equal to c' in S' and slower. Thus speed of light not remain invariant in relative motion. There is no constancy of light or either time is not different in relative frames. Time is no more local if speed of light to be remain same in relative motion. Similarly in longitudanal direction of light, relation between c and c' is given by, c = c'/(#^2) --- (6) Using above relations in case of Michelson-Morley's experiment's calculation, time measured in frame of interferometer for transverse direction is, t'=2L/c' similarly, t=2L/c=2L#/c' for longitudnal direction, t'=2L/c' and, t=2L×#^2/c'
There is no electron spin in electronic model of atom. That was induced for stability of matter due to orbits of charges. But electric force is countered by magnetic force at centre and thus there is no need of electron spin.
Wait, the drawing of the curvature of space time directing us into the earth and the earth pushing us away from the center of the earth and that is the experience we call gravity seems to indicate that the "force" of gravity is not straight down? Is that correct?
You know it's going to get serious when you're on 7 and the video is only half over
Though, most of the latter part is sponsor fluffing these days anyways, so, it's not really that more serious.
Or... there are a lot of ads.
not to mention he was like "ima speak a little slower now"
It got serious for me at stage 4. I get inertia, I get the whole 'ball in the middle of a sheet' example, and I get that time is a series of snap shots, but WHY any of that stuff happens is totally beyond me.
Hunter Humphrey
Serious = good in this case.
To quote Enrico Fermi: "Having listened to your lecture I am still confused. But on a higher level."
Man, if that quote doesn't describe my 400 level physics classes so well.
This captures my feeling precisely.
That's pretty much all learning though, just increasing the level you're confused at until you're the most confused one in the world
@@portobellomushroom5764 At that point, you're so confused that the only way for you to be not confused is to make new discoveries in your field.
@@YoshisaurUnderscore I think you mean the only way to be confused in new and interesting ways is to make new discoveries in your field.
"general relativity is a physics theory created by Albert Einstein"
Me: hold on smart guy, take it easy.
I must agree.
Gui
Let's start simpler...
a squared plus b squared equals c-squared.
@@ivoryas1696 woah there, shapes? i thought this was physics
@@fynexjeralt4186
Lmao, that's low-key how I felt entering Pre-calc 😂🤔😐
Hahahahahahahahahahaha 😂
3:20 is my favorite part because I love how he lists off the numerous observations that validate the model. It's the observations that make this a physics theory instead of just mathematics.
0:06 : What you study in class
1:53 : What you get for homework
4:30 : The exam
I can certify your comment. Its accurate
"You went over it briefly 3 years ago, so now in this class we only review it"
This is, indeed, correct.
This comment has to be pinned 😂
Its in the small text on the side that they never tell you to read or acknowledge at all in my experience
7 levels, in 6 minutes. Less than a minute per level. Truly living up to the name “minutephysics”
That's cool but also level 7 was about half of the video (2:58)
jan Melantu
"It's what I do."
I've been studying this for years. This is by far one of the most accurate videos on the field. Level seven is the strict construction of the equations and their solution throughout classical differential geometry, tensor calculus, complex analysis, linear algebra, ordinary differential equations, partial differential equations and special functions among the classical fields.
This is simply a compendium of what this is in its entirety. This is the field of Riemann Manifolds.
This is the kind of stuff that originally bothered me about science: that you have to keep coming back to a topic in order to learn the next stage as your level of understanding increased. Now, as a biology teacher, it is one of the things that makes science, and learning in general, fun. "Remember how you learned in middle school that plants make energy from sunlight? Well it's actually more complicated than that." "Remember how you learned in high school that plants make monosaccharides from sunlight? Well it's actually more complicated than that."
I take the view that this is because everything in science is an approximation. The approximations get more accurate, Newtonian gravity, general relativity, whatever quantum gravity might be, etc. but they never become statements about the state of being of nature. Only nature itself a knows how nature is. And science merely concerns what we can say about nature.
@@Cosmalano completely agree with your statement about us never knowing the absolute truth/ exact way something works. Personally, I would switch "nature" for "God" but to each their own.
@@adnanchinisi7871 God? lol
@@tattwa1 Aw c'mon. God is just the standard thing we stuff in all the gaps of our knowledge. Each time we learn something new, we yank the god out of that gap and stuff it into the next.
@@Cosmalano This is also one of the core tenets of Kants philosophy.
en.wikipedia.org/wiki/Transcendental_idealism
my two brain cells have been stuck on level 2 since past 5 years
Lol You'll get it.
@@anoushka6439 Oh, lah-di-dah, look at you with your extra smart brain cell that can do twice the work of normal brain cells.
man! you got the same image as mine!
yes
i am a kid
My brain cell went "kablooy" 🤯
glad rest of them made it through
Level 3: Okay, kinda get the main idea
Level 4: ｗｈａｔ
Not liked because number 69 likes
really
@@user-rc8bb7yb1e dude you have a cool name
Just ignore the word salad and listen to the stuff he says after that, it makes more sense; I feel he shouldn't have led with the proper scientific name
@@dsdy1205 Ikr but now I can show off to everyone by knowledge of a pseudo-riemannian manifold is
Nobody literally nobody:
1st year Physics Undergraduates:I'm gonna unite GR&QM
I'm also a first year physics UG currently at hansraj college. Delhi university
Which college you are from
@Swastik Majumder nice! I also want to get into an IISER. I am going to give the entrance exam this year (again, as I didn't clear it last year), and I hope to get into an IISER!
@@yashkrishnatery9082 what are you studying there?
@@pulkitmohta8964 I'm preparing for JEE
Last year I qualified both exams but didn't took admission as I didn't got rank under 2000
I didn't took any formal coaching last time so I dropped and preparing
@@pulkitmohta8964 at hansraj I'm studying nothing. I'm just focusing on JEE. I just took admission there as I was getting in almost all DU colleges
Level -1: falling Apple + head = ouch.
Newton level: fallin apple + head = gravitational universal law
@@Epilogue_04 Oh, what's Steven hawking Level then?
I like this level. And I'm hungry.
Lol
Level -1.5
ground = good
Not ground = ouch
Level 14 of General Relativity: Obtaining a PhD in Theoretical Physics
Not neccesarily. Anyone with a class in GR can understand most of it. PhD in Theoretical Physics is much more sophisticated it develops on already developed GR and Quantum fields theory for example trying to develop parts of string theory.
I have a theoretical degree in physics
@@qazwerty41339 I have a physics in theoretical degree.
Nicee
@@denverbeek I have theoretical in degree physics
05:09 „It is very high-level stuff“
Our math teacher when creating the tests: „Haha what did you say? Pathetic.“
I like your quotation marks
@@wellshit9489 I'm Russian so it explains everything
@@deadoira I wasn't being sarcastic dw, we have them in Iceland where I live too
@@wellshit9489 I know, just decided to explain :)
I'm level 7 for things that I know.
I'm level 0 for things that I understand.
Ricci tensors, curvature scalars, antisymmetric tensor fields, Grassmann variables, Christoffel coefficients, diffeomorphism invariance, isotropic pressure in vacuum states with cosmological energy densities, nonlinearity distinguishment from e.g. Schrodinger's equation and Levi-Civita symbols.
Is it weird that I'm the exact opposite: Level 0 for things that I know; Level 7 for things that I understand?
@@TheShamansQuestion He wants to understand the things which he doesn't understand while neglecting the others.
You want to understand the things you already understand but in as much more depth as possible while neglecting others..
@@srajanverma9064 very nice 👌🏻 you're right my want is there but I'd de-emphasise "want" and say it's more once I get knowledge, I can understand it deeply (and because I want to/go for depth), plus a sceptical, Socratic element of "I know that I know nothing" (but that is probably more relevant to "understanding" in this case, so might be wrong on that)
You just summed up physics
I like that you include geodesics, a major step in my learning.
Having solved the Einstein Field Equations for a physics final in college, fuck. That is all.
what topics do you go over before learning about Einstein's field equations?
@@abelnolan9378 differential geometry and differential equations, I believe
@@abelnolan9378 differential geometry, you will need tensors too, and a bit of classical mechanics and differential equations
It takes at least a few hours to derive even the simplest solution (Schwarzschild solution) to the EFE by hand. A set of 10 highly coupled nonlinear differential equations makes even the most brilliant mathematicians cringe.
I once had a professor that said "Everyone should curl up with a warm drink and spend an evening deriving the Einstein Tensor for the FLRW metric by hand at some point in their life". Needless to say, I haven't done that yet.
3:44 That is NOT "the black hole at the center of the Milky Way" (Sagittarius A*) that is the black hole at the center of galaxy M87. They did consider imaging Sagittarius A*, but that was ultimately not their target. Edit: It turns out I do not know how to spell "Sagittarius."
That’s what you got out of this?
@@GrayLynch No, that is a correction to a mistake they made in the video. In no way did I suggest that the video wasn't worth watching or is otherwise "ruined" as a result of their mistake; but if it were me and I made a mistake in a science education video, I would hope I would be corrected.
I immediately noticed that error as well.
Yeah but fan fuct: we do orbit the M87 black hole
@@alwaysdisputin9930 have you got a source on that?
Finally, I knew taking a course in differential geometry would be useful someday.
This is the ultimate video to confuse flat-earthers even more :-D
and round-earthers too
I had a discussion with a friend who's into conspiracy stuff, for shits and giggles mostly mind you, about how in a very special way, yes, you can say that the earth is flat.
Twas a fun talk haha
No. Flat earthers are immune to facts.
You thought the *Earth* is flat?! Well guess what, even space and time aren't flat!
still stomping on those ants? lol
Remember when math and physics had numbers?
.... yeah me neither
indices !
I'm firmly convinced taking a maths/physics course is about the most roundabout way of learning the greek alphabet.
I think I saw an 8 somewhere in the video, but it might have been an illusion
@@FranciT98 Hey, you do learn it pretty quickly.
Non-mathematicians: wait, it's not about the numbers?
Me: never has been (points gun)
It is just utterly mind blowing how much much Einstein figured out, in the era before powerful computers and such. An elegant set of equations that allow us to predict the past and future of the fucking universe??? Curvature of space time??? Time dilation??? I just cannot wrap my head around it !
This is to show difference between classical relativity having galilean transformation and theory of relativity or relativity having lorentz transformation. The wave equation is given by,
c² d²/dr² = d²/dt², where c is speed of wave.
Its possible solution is sinusoidal function, omitting amplitude and type of function here stating its phase function □ which determine value of wave function at given time and distance coordintaes is, □ = kr - wt
Frame S is at rest and S' moving with speed v relative to S. Then solution of wave equation having phase as, □ = kr' - wt', for S'.
As phase is constant for wave moving in frame, then for r'1, t'1 and r'2, t'2 phase difference is,
□2-□1 = k(r'2-r'1) - w(t'2-t'1) = k◇r' - w◇t'=0 => ◇r'/◇t' = w/k = c'
For wave in S' observed by S according to classical relativity,
k◇r - w◇t = k(◇r' + v◇t') - k(c' + v)◇t' = 0,
where w = kc' and r = r' + vt', t = t'
So, ◇r/◇t = ◇r'/◇t' = w/k = c' = c
Thus speed of wave in S' observed by S' and S is same according to galilean transformation.
Now if phase of wave from moving source S' emitted wave and observed in S is given by,
□ = kr - kct = kr - k(c' + v)t,
where c = c' + v, according to galilean transformation and c' is speed of wave in S' or with respect to source and c is speed of wave in S or to observer at rest.
Thus, w = w' + kv, where w' is frequency of wave emitted from source and w is frequency of wave observed by observer, this is doppler effect. So classical relativity inherently have doppler effect.
Now according to theory of relativity having lorentz transformation, phase difference of wave in S' observed by S' is given by,
□2 - □1 = k◇r' - w◇t' = 0 ==> ◇r'/◇t' = w/k = c'
Phase difference of wave in S' observed by S is given by,
k◇r - w◇t = k(◇r' + v◇t') - kc'(◇t' + v◇r'/c²)
This shows that speed of wave is not same for both observers and in case of light it is, c = c' - v.
For phase difference of wave emitting from moving source S' and observed in S at rest is,
k◇r - kc'◇t ==> c = c'
Thus wavefront of wave in relative measurement is spherical in classical relativity and elliptical as per theory of relativity. But wavefront of wave for moving source is spherical in theory of relativity and elliptical in classical relativity. Important thing is that due to spherical wavefront inspite of moving source, relative speed doesnt remain constant and heavenly bodies seems receeding. While wave front is elliptical in classical relativity so, speed of source is accounted. Also this is the reason why circular orbit seems elliptical.
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1:20 that's a nice globe you got there.
Me, an intellectual: actually, it's a pseudo-Riemannian manifold with Lorentzian signature,... But thank you! 😊
..out of all of them......this made me laugh the most. Well done 😂
Nondegenerate symmetric metric tensor too. Establish the linear connection/Levi-Civita connection with use of Weyl spinors (helicity operators).
Dave P
_IQ +10_
Ok so basically its gravity
At the 3 minute mark I had to pause because I just got hit extraordinarily hard by the re-realization of the nature of existance and our place within existance itself. It was like a philosophical seizure that caused me to sit back in my chair and stare at the ceiling in AWE of whatever the hell it was I just experienced.
Great video. Your videos got me interested in general relativity six years ago, and to this day I’m still trying to become a mathematical physicist so I can study quantum gravity. ❤️
4:05 I finally understand how gravity works on our planet. Omg. That was the best explanation I’ve ever seen.
Penrose and Hammeroff's Orch OR is a pretty good candidate for a theory of everything. Where gravity causes an objective (probabilistic) collapse of superpositions in space(time), as Epicurus predicted in ancient Greece, these objective "chance swerves" explain conciousness (electron oscillations inside nueronal microtubles) and why all things don't free fall -- in other words, there is (and always has been) a connection between gravity and superposition. Namely, that g-forces snap superpositions into one (inertial) position in the same way that wings of a plane snap people up and keep them flying in the air rather than free falling.
So good. I've tried so many times to explain the way the ground pushes you away from a straight line and I've never once passed understanding across. Now I can link to this video with the clear diagram, and maybe in future, I'll succeed in showing the beauty of this idea to others.
the funny thing is, he's only explaining it for those who already know.
I wish it was possible to explain it for the ones who didn't know. I wish that every day
Skatheo
Well beyond around level 4, yeah, but it's seems pretty okay otherwise.
@@ngiorgos I think Vsauce's "Which way is down" video does a pretty good job. It gets more obtuse near the end and doesn't even get as high-level as this, but I like it a lot.
@@TheBlueWizzrobe Yes, I loved that! And Veritasium's video "why gravity is not a force" is also an excellent presentation.
But the best they can do is give an overview of the theory and some intuitive explanations. The maths are still untouchable, unfortunately.
I got to around level 5, then level 6 I only knew some of it.
The reason that this is difficult to comprehend is because we think of objects as travelling though spacetime, rather than being products OF spacetime. So, instead of you being a constant, travelling through an environment, what's really happening is the quantum environment manifests as the quanta that together make particles, conserving energy and momentum, effectively passing energy from one bit of spacetime to the next, rather like pixels that manifest as moving images. When these individual 'pixels' (or strings / membranes / e8 crystals / whatever they turn out to be) act they exert a pull on the fabric of spacetime, meaning that when many act together the pull is greater, and this creates the effect we know as gravity.
This is how I understand the shape of the Earth, in as simple a language as possible - Look at the Planet Earth as a sphere from outside, from inside it's a diameter...we're in the middle, the sky is the top, the bottom is the ground level area....the Earth goes round but easily seen moving in a straight line but somewhat curvy (if that makes sense). When the Earth rotates in space, different continents experience changes in the atmosphere like darkness, sun/solar radiation etc but, we only realise that, by looking at the sky when it changes.
It's not a question of "when? " my dear Reggie, but "where?"
It's the same thing with the concept of spacetime
No no both when n where n how much
It’s about whenere/ wheren.
Metaphysics: it's not a question of "what?" my dear Reggie, but "why?"
I have been subscribed to this channel for quite some time now, I initially got interested because of my great physics teacher in high school. Back then I did not understand most of the videos at a deeper level (so the primary target audience).
After 3 1/2 years of studying physics, I have my GR exam on monday and can happily say: I knew everything in this video! And it makes me glad to finally be at a point where I do understand this stuff at a deeper level. It took quite some time, but I got there.
Of course I am still just beginning to be a physicist and there is MUCH I don't know yet and MUCH and I don't know that I don't know yet. And I am excited and looking forward to finding it out!
Keep it up and thanks for your service to science :D
Same story here.
Such Videos brought me to physics. According to plan, I'll have my Bachelor in half a year.
@@fischmann1746 Then I wish you best of luck for your thesis! Do you already know in what area you will write it?
@@aemmelpear5788
Thanks.
I'll write a program that simulates a non-linear mechanical system and analyse it's behaviour. What system in precise isn't clear yet.
Writing simulations in non-linear physics is pretty much the profession I want to finde myself in some day.
@@fischmann1746 Sounds great! Computational Physics is also one of my favorite areas!
"very high level stuff" - like nobody has figured out how to do it yet
As a physics major heading into my sophomore year, the feeling I get watching this video is roughly akin to the feeling I get at the top of the first hill on a roller coaster as I stare down the straight-vertical track…
Cool concept for a video. I especially enjoyed the "level 1 again" explanation of people's personal experience of gravity on earth in terms of your GR explanation.
This video: There are 7 levels of understanding gravity.
Me: I can make it to level three, take it or leave it.
DW thats pretty good
M87 is not at the center of the Milky Way! It’s in another galaxy about 50 million lightyears away.
Loved the level 0, something Einstein did 😂😂
Ricci tensors, curvature scalars, antisymmetric tensor fields, Grassmann variables, Christoffel coefficients, diffeomorphism invariance, isotropic pressure in vacuum states with cosmological energy densities, pseudo-Riemannian manifolds, nonlinearity distinguishment from e.g. Schrodinger's equation and Levi-Civita symbols.
Cool Video
It's pretty simple to illustrate that standing motionless on the surface of the earth, your "straightest line through space time" runs through the top of your head, out your feet and straight to the center of the core. The 'weight' you feel is your body being in constant deceleration from its fall being blocked by all the matter beneath your feet.
Another interesting thing about general relativity; if you put a clock on the surface and one at the core, the clock at the core would run more slowly as it is at the deepest part of the gravity well.
For a body in rotation, like the earth, this variance in clock time produces a core which tears free of the surrounding strata and spins ahead. We call it a 'super rotating core' and it's what produces our electromagnetic field.
It's General Relativistic Acceleration in the spin direction.
Why Euclidean geometry is general case and differential geometry is special case, which they say otherwise.
Take an example of surface of sphere so radius become constant. Now line element is given by,
ds² = g(ij)dx(i)dx(j) = r²d□² + r²sin²□d○²,
where □ is azimuthal angle or angle with one fixed axis of Euclidean space from 0 to pi, and ○ is polar angle or angle around centre of circle whose radius is projected by □.
In sphere line element is given by fixed radius and fixed azimuthal angle, □. That is given by,
ds = r×sin□d○
But it is good for fixed □, like arc of great circle at equator or small circle having fixed latitude. If there is arc part of great circle other than equator, the above relation can't calculate length. That is its azimuthal axis is tilted by some angle. Even if one previously transformed rectangular coordinates into spherical, it didn't calculate.
To calculate above arclength, one has to use rotation matrix or change coordinates in Euclidean space or rectangular coordinates of plane having azimuthal axis. This shows that what they publicise that metric tensor free from coordinates is untrue. Problems are specific and they can't be generalized when speaking of geometrical measurements.
Euclidean geometry is basis of space because it is not closed like other, so Euclidean geometry is generalized form and differential geometry is specific depends upon problem or surface encountered.
What is General Relativity?
Level 0 answer: "posts this youtube link"
Thanks for summing all that up in a short video. I've seen a lot of videos explaining GR/SR on different "levels" and this gives me a nice feel on where I stand in my understanding of the subject.
This totally helped me understand. Great concept.
I listened to a Great Courses lesson back in the 90’s and they completely left out the spacetime concepts of the second half of the video but said that at the quantum level special relativity rules still applied. So much has changed since just the 90’s. (Hard to believe the course was recorded nearly 30 years ago)
4:48 'Nowadays' ends at 1997, wonder when the next breakthrough will b e
@@qingyuewu6429 It's a bot
I literally have to do a research paper on general relativity, thanks so much.
Just finished taking general relativity this quarter that passed, and I can honestly say that this is the hardest topic I've seen so far in my physics career, but also the most enjoyable.
3:41, correction: the famous photo of a black hole was from the supermassive black hole in the center of galaxy Messier 87 in the Virgo cluster (the Milky Way is part of this cluster). The black hole in the center of the Milky Way is not directly observable, and about a 1000x smaller than the one photographed in M87.
Great minute summary of general relativity though!
Isn’t the black hole image from M87?
It is, I think he was just trying to represent black holes in general
@@eduardonegrao8364 He said "direct imagining of the black hole at the centre of the Milky Way".
Getting to level 5: "Oh Jesus".
Level 2 : OK
Level 3 : Yes, made sense
Level 4 : What
Level 5 : *brain explode
so if space and time form a single geometry and we move in a certain direction in time, that means there is no force pushing us in either way on time axis. so if we can be pushed backwards or forwards in time axis...
So would combining general relativity and quantum mechanics get us the world formula?
T H E O R Y O F E V E R Y T H I N G
it will give us our world seed.
ScienceClic is an underrated channel that you should collaborate with.
yeah.. this is something I definitely have to research more for a better understanding
3:41 *black hole of a distant galaxy
Thanks!
You know what the insanely insane (and awesome) part of this video this? THERE'S MORE LEVELS!
(For reference, I think I'm at 6.5, or at least between that and level 7. The idea of manifolds and tensors is something I have yet to understand, but I understood the rest of Level 7).
Him just throwing experimental proof after proof after proof of the theory of relativity and that it is genuinely true non-stop for so long and you're just thinking "Okay, enough examples, it's true" and he has as many more to mention; it just goes to so.
"So if you combine both quantum theory and general relativity,you get Nobel Prize."🙄
I was sad to see that after all these years of studying I still can only explain the concept to others as level 2-3
And this is why things get so specialized as you get higher in education. Monke brain no good at figuring everything out. Maybe one small thing, and have to spend a lifetime on it.
A year ago I could only understand upto level 3, but now after a year I can understand level 6 and 7 :D now I need to learn lots of differential geoemtry and tensor calculus and learn how to solve the einstien field equations
The picture of a black hole at 3:41 was not the black hole in our galaxy (Milky Way). It was in fact a picture of the black hole which is located in the most nearby galaxy (Messier 87). They couldn't make a picture of the black hole in our Milky Way, because it was too close and there was a lot of light pollution.
Me: listening to this 🥴
Morty: now you know how I feel
3:41 - You talked about direct imaging of the black hole in the center of our galaxy, but showed the black hole at the center of Galaxy M87 (a completely different galaxy) that was actually imaged. You might want to correct that.
From curve of matter irradiation of electromagnetic wave from cavity oscillator, Wein's displacement law shows at given temperature, frequency of maximum interaction of energy is at particular frequency. This means that there are no integral multiple of energy exchange as proposed in model of a particle in a rigid potential wall or box. So a given system can interact at multiple energy level is incorrect.
Meaning of standing wave is equivalent to resonant frequency and that is characterstic of system. Any change in characterstic value is change in elements of system, thus a given frequency value can interact with given system.
Mathematically it is possible that solution of differential equation permits integral multiple solution, but for fixed constraints of system only one is solution depending upon boundary conditions. So a given quantum system cant have multiple energy or quantum states. Further interpretations of quantum mechanics on some other time.
maybe another species of intelligent life already 4 parallel universes ahead of us, humans.
The final solution is the observation of the size and it's infinite expansion or constriction, for it is assumed anything can be infinitly large or infinitly small. This is the defining dimension that describes and encompasses both general and quantum theory.
I can heart his mouth spit... the quality if this mic is amazing
Guess who's back , back again ...
My only problem with the end there was it seemed like the solution we are working towards is a very "in the box" one, like working harder not smarter. Wanted to use that as a jump point (not criticizing, I actually love it was there, gives something to talk about). If anything, the existence of Einstein's theory shows us maybe the way to go about creating theories is truly thinking outside the box (the box being our firm but unimaginative perspectives). I'm reading his book now (translated by Robbert W. Lawson, D.Sc. and you can really see how he came to the making of the theory. Not by trying to connect everything together like lines in a plane in a certain co-ordinate system, but instead by asking something like (am I even in a plane? Why am I so certain of the concept?). Question literally every concept we adhere to as true (like how he goes on about the different coordinate systems throughout time that largely base their "truths" on made up preconceptions), he talks about it literally in the first couple of paragraphs. As he says, "The important thing is to not stop questioning. Curiosity has its own reason for existing." The moment we accept whatever truths we're given by authorities or others, we succumb to its limitations instead of the limitless power that is our own imagination.
"Imagination is more important than knowledge. Knowledge is limited. Imagination encircles the world."
"Unthinking respect for authority is the greatest enemy of truth."
So if we don't learn to take a step out of our perspective, we're kinda doomed to make slow, receding progress instead of a major jump towards reality.
Fantastic video, very very humble in delivery and knowledgeable in the field.
Me: "I just finished a phD in theoretical physics and have a pretty solid understanding of general relativity. I think I know a lot about gravity now."
Henry: "Think again."
you lost me at level 3
Sun is emitting light and hot bodies glow light. But spectrum of sun is continuous which can be observed with crystal or cd. Different colors are in thick bands and not thin line. So how energy is quantized in hot solid bodies. By quantization means different colors are separated by dark regions which is not observed. Temperature of body can be calculated by light emitting from body of different colors and they do integration which is for continuous function.
A circle is locus of points which are equidistant from a point called as focus or centre. Joining of locus is curve, where points are discrete but curve or function is continuous. So, do circles are continuous or discrete, continuous means curve is smooth. Similarly calculus is done with discretization of interval but on continuous function.
Yes, quantum mechanics shows that wave seems as continuous but made of discrete small particles, operated as smooth. Similarly interaction of energy and matter is participated by discrete particles known as atoms but there is no restriction on amount of matter and energy, continuous.
This is the best thing I have ever seen.
"General relativity is a physics theory invented by Albert Einstein" :D :D :D :D :D :D :D :D :D :D :D No...
How so? Genuinely curious
@@justkirb6955 The "Einstein phenomenon" is a hoax, a pure propaganda. It's not hard to see how. Here's the short rundown. Special theory of relativity is the theory of transformations on a quasi-Euclidean space. More specifically, the spacetime is the Minkowski spacetime, and the transformations that leave it invariant are the Poincare transformations, the homogeneous version of which is known as the Lorentz transformations. One consequence of these transformations is the Lorentz-Fitzgerald length contraction, as well as the time dilation. That's it. This is special theory of relativity. Do notice that NONE of these bear Einstein's name. None. It's the work done by Minkowski, Lorentz, Poincare, and Fitzgerald. Oh, and Michaelson and Morley did the famous experiment. Now, general theory... when Einstein was toying with the Poisson equation on a flat background, having no idea whatsoever about the existence of Riemann manifolds, Nordstrom published a paper attempting to explain the motion of our moon by curving the spacetime and calculating everything with the Riemann formalism. All this happened before Einstein even heard about the existence of the Riemann differential geometry on curved spaces. What Einstein did was to consult his friend, mathematician Grossmann, who then lectured him on the Riemann spaces. One part there are the Biancchi relations, where the Biancchi tensor, made by contractions of the Riemann curvature tensor, is covariantly conserved, and these Biancchi relations serve as conservation equations of physics. This Biancchi tensor, Rij-Rgij/2, is nowadays known as the "Einstein tensor", even though it was Biancchi who invented it and proved the conservation. So, you see... it's a bloody hoax. If interested, I can check some books for references, for instance, "300 years of gravitation" has an interesting article on it. But, just by reviewing superficially these developments of relativity, one comes to immediately realize that Einstein had nothing to do with it. It's a hoax. The theory itself is correct, of course. But it has nothing to do with Einstein.
@@Kraflyn So basically, a classical instance of naming things wrongfully. I mean now that you explain it does make sense. Thank you for taking time out of your day to explain.
The R in FLRW is Robertson, not Robinson. Named for Howard Robertson, who among other things proved and reformulated the Heisenberg Uncertainty Principle.
What more observational anomaly than theory in relativistic gravitational theory is that inspite of big bang, orbits of planets are stable, atleast for many thousand years, also no detection of angular separation of stars. So meaning of stable orbits is that diagonal elements of mass-energy tensor are zero, because there is no expansion of orbits in radial direction. So i think there would no independent or orthogonal space-time coordinates,
Theory could improve if they consider space and time coordinates differently. Time is part of space-time but not interfere length of coordinates of space. Thus space have 3 dimensions constituting volume and time is indicator of motion like orbit is clockwise or not and thus time in forward or backward direction. So space become a dimension and time another dimension of 2 dimensional space-time having volume.
Other problem is that differential geometry or topology is construct based on idea or model which have flaws like length of curve is given in term of speed, so more curvature has less speed, but this is not as observed because distant orbits have same speed as nearer one, that is why different time period. It should be as, space is elongated and time is dilated so speed remain same, which is observable as distant orbits have bigger orbit and longer period.
Relativistic gravitation was developed because in newtonian model not account for how everything starts from origin. It only account for stable orbit where orbital motion account for entropy or force in action. So what was before newtonian model could explain by relativistic gravity where diagonal energy have some value and cease at stability, it is transitory model.
Correction: general relativity PRESENTED in 7 levels of non-explanation
Hey not everyone is gonna get it. I'm sure you're real good at other stuff. Practical hands on stuff. Like eating your own boogers...
@@littlenismo ouch, that was just unnecessary
Amazing video, but I hate it when text disappears too fast to be read. It's too fast here even when you try to pause and play.
I understood a lot more than I expected.
This is all wrong, everyone who's taken doctoral level physics classes know that e = mchammer^2
At 3:42 you said we imaged the supermassive black hole at the center of the Milky Way. But we did not. As shown in your video above, we imaged M87 which is the supermassive black hole at the center of Messier 87.
Great content! Hey, maybe someone commented before but i don’t see it. At 3:43… you say that M87 is at the center of the Milky Way. It’s not!
Vantage point is, time measured of event happened in moving frame S' that was round trip of light in transverse direction of motion is t',
c' = 2L/t' ---- (1),
where L is length, and c' is speed of light in S'
Relative time measured from rest frame S is t,
c = 2L/t ---- (2)
where c is speed of light in S
From relativity, time is slow in S' measured from S so,
t = t'# ---- (3), # is Lorentz factor
From (2) and (3),
c = 2L/(t'#) ---- (4),
From (1) and (4), c = c'/# ---- (5)
From (5), it is clear that speed of light, c in S is not equal to c' in S' and slower.
Thus speed of light not remain invariant in relative motion. There is no constancy of light or either time is not different in relative frames. Time is no more local if speed of light to be remain same in relative motion.
Similarly in longitudanal direction of light, relation between c and c' is given by,
c = c'/(#^2) --- (6)
Using above relations in case of Michelson-Morley's experiment's calculation, time measured in frame of interferometer for transverse direction is,
t'=2L/c' similarly, t=2L/c=2L#/c'
for longitudnal direction,
t'=2L/c' and, t=2L×#^2/c'
The universe doesn't OBEY the field equations. The universe is DESCRIBED BY the field equations.
Wasn't the imaging of the black hole from another close by galaxy and not sagittarius A*??
the black hole imaged was the one at the center of M87 not the milky way, it says it right in the title of the paper you showed
*nods head in blank confusion*
“Yep, those words you said... sounds about right”
Honestly, I have no idea how one could come up with something like this, especially these exact equations.
Level 8: becoming one with the universe ✨✨✨✨
There is no electron spin in electronic model of atom. That was induced for stability of matter due to orbits of charges. But electric force is countered by magnetic force at centre and thus there is no need of electron spin.
Wait, the drawing of the curvature of space time directing us into the earth and the earth pushing us away from the center of the earth and that is the experience we call gravity seems to indicate that the "force" of gravity is not straight down? Is that correct?
How do you explain tides using spacetime
This video is a masterpiece.
Wow, I am level 3 strong. I am proud. Kudos to those physicists out there working on these theories. Badass stuff!
i cant comprenhend any of this but it sounds cool so I watch it and just sit through all of these things that don't make sense