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This video covers the General theory of Relativity, developed by Albert Einstein, from basic simple levels (it’s gravity, curved space) through to the concepts of how curved spacetime is represented by psuedo-Riemannian manifolds with Lorentzian signature (that is, special relativity and minkowski space are the local tangent space), how matter and energy are represented by an energy-momentum tensor, and how these two together obey the Einstein Field Equations. The solutions to the Einstein Field Equations (including the schwarzschild metric, kerr metric, freedman-lemaitre-robertson-walker metric, etc) represent gravity around massive objects like the sun, earth, and black holes, but also the history and expansion and future evolution of the cosmos. The universe on a large scale is described by general relativity – on a small scale, quantum mechanics. And where they meet… there’s still work to be done.
REFERENCES
Wald’s textbook – General Relativity
Hartle’s textbook – Gravity: An Introduction to Einstein’s General Relativity
Carlo Rovelli History of Quantum Gravity: https://cds.cern.ch/record/442809/files/0006061.pdf
Leon Rosenfeld 1930 paper on quantum gravity: http://www.edoc.mpg.de/438547
Kerr Metric Solution – https://en.wikipedia.org/wiki/Eddington%E2%80%93Finkelstein_coordinates
Schwarzschild Metric – https://en.wikipedia.org/wiki/Schwarzschild_metric
Eddington-Finkelstein Coordinates – https://en.wikipedia.org/wiki/Eddington%E2%80%93Finkelstein_coordinates
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Minute Physics provides an energetic and entertaining view of old and new problems in physics — all in a minute!
Created by Henry Reich
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22 Comments
@ShokkuKyushu
02/15/2025 - 12:11 AM@MinutePhysics Question :does the escape velocity equation change when we talk about massive compact objects? The kinetic energy term of the equality cannot be (1/2)*m*v² ,(gamma -1)*m*c² is ,and is GMm/r² still valid?
@leonardoaraujo8364
02/15/2025 - 12:11 AMEste vídeo é uma bosta
@anonymous7-07
02/15/2025 - 12:11 AMSo nice.❤
@redalert2834
02/15/2025 - 12:11 AMYou forgot the 8th level in which Einstein's 1939 paper explaining why black holes don't exist, which was ignored until the Covid pandemic, and still is ignored, is correct – resolving the non-existent black hole information paradox (amongst many other cringeworthy paradoxes associated with black hole spacetimes).
@talonhackbarth7652
02/15/2025 - 12:11 AMSlowly descends into madness
@B_I_R_B1234
02/15/2025 - 12:11 AMThe title should be 'General Relativity Explained in 11 levels of difficulty'
@SpacetimeTraveler-p4e
02/15/2025 - 12:11 AMWhy is GR incomplete? Relativity describes the gravitational field have anything to do, necessarily, with quantum phenomena? Is electromagnetism incomplete because it doesn't describe the gravitational field?
@mehdizangiabadi-iw6tn
02/15/2025 - 12:11 AMWhere does Crow's gravity come from?
@mehdizangiabadi-iw6tn
02/15/2025 - 12:11 AMThe curvature pulls the object towards itself or makes it float
@recessiv3
02/15/2025 - 12:11 AMWhy does quantum entanglement break locality but not causality if space and time are linked?
@AjaySahai-y7o
02/15/2025 - 12:11 AMOne math is based on Einstein, the other math is based on a guy who took Acid to derive the wave function equation (Schrodinger). Thats probably why you can't reconcile the two.
@yoinch
02/15/2025 - 12:11 AMHow do I turn off the sound?
@kamal__6199
02/15/2025 - 12:11 AMHow would you explain it to a flat earth believer
@PhysicsLiteracyforKids
02/15/2025 - 12:11 AMThank you so much for all your work. I have used many of your physics videos for my classes. Little kids especially get a big kick out of them!
@jotindersingh8559
02/15/2025 - 12:11 AMWatched so many general relativity video. Never understood any of it. None
@namonef
02/15/2025 - 12:11 AMI have a question. What is the importance of unifying QM and GR? I mean, spacetime and massenergy is two different things, right? So why do we need to combine them both?
@tweedy151
02/15/2025 - 12:11 AMsomeone explain the bit from 4.00 please. Particularly around 4.12 'the centre of the earth accelerates us away from that stright line path' – how does it? I keep thinking i get it then i don't again.
@Fkd-About-Found-Out
02/15/2025 - 12:11 AMto unite general relativity and quantum mechanics you need to change the scale of the board, shrink down so a hydrogen atom is as big as a star, what would your universe look or feel like, even if it was an o2 environment you wouldnt breathe, you couldnt see normal wavelengths of light, would the universe be dark? or would the vibrating hydrogen atom look no different to a star, its electromagnetic wavelengths that were too small for us to measure could look just like normal photons and lightwaves thru a medium that wants to pull you in equal and opposite directions.
What keeps things spherical even on those levels, spacetime being curved.. even on those levels spacetime curves and ripples with information.. id love to experience it for myself.
Core from the north to south pole and jump in, you would find a weird point at the centre of the earth where the mass of the planet is pulling you out in equal and opposite directions. If you wasnt spherical you would spin like crazy.. but there is a Lagrange point right at the centre of our planet. not a gravity well.. not all things fall down, at a certain point there is enough mass pulling upwards, so why do we think there is a molten iron core again?
Time dilates on those scales, when the universe was small and hot, if you slow time down it could be cool to an inside observer. It would seem hot and dense to us, but its just illusions of expanding spacetime, it would be expanding in 3d so it follows the inverse square law, the more it expands the slower time looks, relatively speaking..
Scale and perspective change everything, a day for a fly that only lives a day will feel far different too the 100 year life we get, imagine your whole life is one day, you would swear it was always sunny.. we have a limited perspective, trying to understand the universe at 1 atmosphere and thinking about 70f or 20c is the normal for things in the universe. Change the pressure and density of the universe and different elements are stable, how can we judge how old the universe really is when we cant visualise how time dilates with the universe as a whole.. i bet if we figure that out we can make cold fusion happen, making fusion happen at room temperatures and pressure, now thats your holy grail, not dyson spheres, solar freeking roadways in space.. manipulating the fundamental forces like salting water to lower its melting point..
Radioactive decay is like water evaporating, its all probabilities. Once you get into a certain temperature it becomes inviting to evaporate, just how if the universe was a little warmer, lead wouldnt be the last stable element.. at the current pressure and temperature lead is where mass freezes and is no longer wanting to evaporate/irradiate.. but its all just energy fields and probabilities on different scales and perspective..
Watch clouds roll into a mountain like waves on the shore, just speed them up, watch the earth flow, just speed it up really fast, there is a layer of reality that changes what you might consider to be solid liquid or gas. just speed things up or slow them down, its all frozen if you go slow enough.. who says what the tick rate of the universe is. Zoom out it looks like an alloy or foam, how could we know what is really out past our reality, maybe this is all happening in a luke warm glass of water in some dudes flat, 6 billion years was just 2 weeks, but lucky he was a slob eh…
@dougkenny6548
02/15/2025 - 12:11 AMThis video made things as clear as mud.
@anwvererere
02/15/2025 - 12:11 AMboy how i miss seeing those Kristoffel symbols from uni 😀 ahahahahhaha. Jesus. Fuck tensor calculus !!
@robertwilsoniii2048
02/15/2025 - 12:11 AMPenrose 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.
@robertwilsoniii2048
02/15/2025 - 12:11 AMFlat space does not make sense. You cannot make or find any truly flat or straight materials anywhere in the universe. Perfect squares are not physically possible.