What are black holes?

The name Schwarzschild is actually cooler than you might think... it is not pronounced with "child" at the end (Like Mr. Lincoln and many others do) but rather "Schild" which is german for shield. And since "schwarz" means black, his name literally translates into "Mr. Black Shield". What a crazy coincidence that his...

You know, Dr Lincoln, I almost filed college physics 50 years ago, but I greatly enjoy your videos. Despite my ignorance, I learn something from every one.

Always a pleasure to get another video from Dr Lincoln. 👍

Fermilab putting out top shelf educational content for anyone to watch and understand. What a wonderful time we live in.

Please use SI / metric system in science videos

Could you show numbers in the metric system please?

@DrDon I wish I had a physics teacher like you in my schooldays I would have learned something then . I devour all of your little lectures (never to late) they`re excellent please keep on posting !!! thanks eric

Can't wait for the next black hole video, thank you Don!

Your presentations always give me a great understanding of the subject - with the least amount of effort on my part. Wonderful outreach teaching!

I see you have reuploaded. My question on the 1st upload about escape velocity decreasing inside the radius of the Sun was answered with this video. Thanks 😉

Note that the appearance of the singularity in the Einstein field equations is dependent on the choices of initial assumptions specifically it arises in the limiting case of the Schwarzschild or Kerr metrics which are particularly symmetric limiting cases assuming that the massive body is the only object in the universe. We thus know this is a limiting case as our universe doesn't just contain a single black hole so this doesn't mean it will be accurate at all distances all we can say with any confidence is that it holds remarkably well out to the distance of the photon sphere for supermassive black holes like the ones at the heart of our galaxy or M87. Interestingly recent work based on taking the limit of black holes going to one finds that hawking radiation does somehow escape likely via a mechanism linked to ER=EPR so clearly there is something special happens outside the Schwarzschild or Kerr metrics in regular unaltered general relativity. It doesn't tell us what it is but that there is something more and at the very least ER=EPR mechanisms appear to be a much more general thing that doesn't depend on the constraints of any additional extension to the theory of General Relativity. One potential theorem which may enlighten this discussion is the No big Crunch Theorem published by Matthew Kleban and Leonardo Senatore which at least in the case of very large Universes (in the limit of the size of the universe approaching infinity) that any arbitrarily non trivial universe can never have an universal inflection point in the direction of expansion which means that the Einstein field equations in order to be logically internally consistent (i.e. for information to be conserved) the metric tensor must always be fully asymmetric i.e. no terms within the metric tensor can ever be identically zero. https://iopscience.iop.org/article/10.1088/1475-7516/2016/10/022/meta One important consequence of this is that all initially expanding Universes must at large scales always expand forever that is to say that while the net effect of matter concentrating together may locally impede the expansion of space the resulting underdensities will always be enough to overcompensate this slowdown resulting in the overall expansion of the general unconstrained Einstein field equations always accelerating. Simulations show this is notably always true regardless of the initial choice of the cosmological constant and thus as such we can completely explain the acceleration of the observed expansion of the universe without needing any additional component of dark energy, its just the asymmetric off diagonal components to the metric tensor. We don't need to stop there however another consequence is that the lack of any global maximum on expansion means that the differential volume of the universe between any two time slices shares the same sign as those timeslices. If we recognize the speed of causality being finite and thus a finite volume which information on the universes initial conditions can propagate, as well as the need for said information to exist somewhere within any time slice of spacetime we can derive the associated gravitational path integration over time slices with a representative volume of that timeslice which can have interacted causally or the dot product of the path integration through the surface area of that timeslice which should correspond to the cosmological event horizon will always have an associated entropy based on the universes initial conditions. This means we get Hawking radiation by default within the unconstrained Einstein field equations whenever we explicitly enforce conservation of information. Note that this doesn't mean you can transmit information faster than light if anything it tells us the Einstein field equations exhibit informational symmetry which causes acausal correlations based on entanglements of past light cone interactions. That is to say General relativity if taken explicitly as Einstein derived with no prior assumptions is fundamentally superdeterministic and should always obey Bells inequality. Sadly this means Bells "free will" clause must always be violated else the metric tensor must be logically discontinuous i.e. information can not be conserved. Mathematically there is no way around this criterion it is a mathematical proof which applies to any system of differential equations organized like the Einstein field equations and can be shown to be a required symmetry of such a system under Noether's theorem. The mind trippy consequence don't stop there however as this nonlocality and causality together require there to be a minimum nonzero contribution to the metric tensor for every bit of information within the initial conditions of the universe in other words gravity self quantizes itself under the conservation of information. From a model perspective this tells us gravity at large scales must deviate from Newtonian gravity because these minimum contributions to the metric tensor don't dilute with distance and thus as the source proximity dependent effects drop off the nonlocal components begin to dominate. Those familiar with MOND may recognize some of these implications which suggests "dark matter" like dark energy may actually be some of the distant contributions of the metric tensor in this case the additional diagonal contributions to the metric tensor. However this only allows the quantization to consist of nonzero asymmetric terms meaning that quanta of spacetime must at least partly behave as Dirac spinors a.k.a. Fermions. All boson based models of quantized spacetime which assuming spacetime fluctuations themselves are the gravitational field means all bosons not based upon a separate quantum field are logically forbidden which may explain why efforts to find a gravitation have always failed. Perhaps this means the universe is built out of gravitinos? I don't know how to interpret the meaning of this but I do know that one mathematical consequence of this is that all quanta of the metric tensor must have a unique and distinguishable quantum state i.e. they must obey the Pauli exclusion principal. In other words the Cosmological principal was fundamentally wrong because it got the order of the Copernican principal wrong our local metric is unique but we are not special because every other place in the Universe is too. It also implies spacetime should become degenerate at some distance scale which given all our observations and a powerful enough supercomputer should be calculatable. And the best part of this is while it solves many mysteries in cosmology it effectively involves no new physics as it is just the properties which the set of all valid solutions to the exact nonlinear domain of the full unconstrained Einstein field equations must have in order to be internally self consistent. The con is of course we can't approximate the Universe at large scales as approximately the Friedmann Lemaitre Robertson Walker metric. But observations have already pretty convincingly cast doubt on that assumption best seen in Nathan Secrest et al 2021 which showed that the CMB dipole must contain a significant cosmological component meaning the CMB alone is enough to falsify the cosmological principal within the entire observable universe. https://iopscience.iop.org/article/10.3847/2041-8213/abdd40#apjlabdd40s4

I love it when Don pops up in my subscription feed!

Please use metric units, or at least provide both! Looking forward to part 2.

Can't wait the mind blowing clip!

Nice subject fermilab, keep m coming

This version made a lot more sense!

Great video thanks my friend

Excellent presentation

I always think about the inside of black holes as non-euclidean geometry. The thing may be bigger on the inside than its radius or observable "surface area" suggests.

Dr. Lincoln is the super star of physics communication