The Incredible Story of Black Holes: Einstein, Schwarzschild, and Beyond

#BlackHoles #Astronomy #SpaceScience #CosmicMysteries #EinsteinTheory #Schwarzschild #GeneralRelativity #SpaceExploration #QuantumPhysics #Astrophysics

What you’re about to watch dives into the most massive, most compact, and most bizarre objects in the universe: black holes. I will guide you through the monumental triumph of gravity over matter, showcasing these cosmic endpoints and their enigmatic horizons into nothingness. It was Karl Schwarzschild who in 1915, while solving Einstein’s field equations of general relativity amidst World War I, created the first mathematical solution defining the spacetime around what we now refer to as black holes. In 1939, J.R. Oppenheimer and Hartland Snyder expanded on this by hypothesizing that when a massive star exhausts its nuclear fuel, it could collapse beyond neutron degeneracy pressure, forming an infinite singularity—a black hole. This collapse marks the fate of stars more massive than a few solar masses. Black holes are not merely empty spaces but regions of extremely warped spacetime where gravity reigns supreme, and escape is impossible. The Schwarzschild radius, or event horizon, defines this region where the escape speed exceeds the speed of light. For a black hole with the mass of our Sun, this radius is just three kilometers. Beyond the event horizon lies the singularity, a point of infinite density and zero volume. As you approach a black hole, the effects of gravitational redshift and time dilation become apparent. Light escaping from near the event horizon is stretched to longer wavelengths and loses energy. For an outside observer, time appears to slow near a black hole, leading to the phenomenon where an infalling object seems to freeze at the horizon. Understanding the anatomy of a black hole revolutionizes our perception of space and time. The intense gravitational fields warp spacetime so profoundly that not even light can escape once it’s past the event horizon. This immense curvature means that space is effectively “longer” near massive objects. We detect black holes indirectly by observing their gravitational effects on nearby stars and the X-rays emitted by infalling matter. The first widely accepted black hole, Cygnus X-1, discovered in 1964, showcases these traits. With a mass of about 14.8 solar masses, it emits X-rays as stellar material from a companion star falls into its event horizon. Recent advances have also allowed us to peek into the heart of galaxies, revealing that supermassive black holes, millions to billions of times the mass of the Sun, reside in their cores. For instance, the black hole at the center of our Milky Way, Sagittarius A*, weighs around 4 million solar masses and influences the motion of nearby stars. Movies like “Interstellar” have brought these cosmic giants into popular culture, depicting the awe-inspiring effects of their gravity on light and time. However, our understanding continues to evolve with the study of phenomena like Hawking radiation, where quantum mechanics suggests black holes can slowly evaporate over incredibly long timescales. Black holes come in various sizes: stellar-mass black holes stemming from the collapse of massive stars, intermediate-mass black holes, which remain a mystery, and supermassive black holes dominating the centers of galaxies. These enigmatic objects are pivotal in our study of the universe, from the smallest stellar black holes to the mammoth supermassive ones, each contributing to our understanding of gravity and spacetime. Join me as we delve deeper into the fascinating world of black holes, exploring their formation, properties, and the profound questions they raise about the fabric of the cosmos. See you soon!

This is part of my complete intro Astronomy class that I taught at Willam Paterson University and CUNY Hunter.

WOOPS LIST:
1) Just after 43:00, I misstated that all the light of the universe would fall into a black hole. Of course, that's not true. I should have said: "As you get closer to the singularity falling straight in looking up, you see all the light of the history of the universe that crosses the event horizon of the black hole you're in." Remember that a black hole is a very small target, however, light does pass through the event horizon. If the universe were to live to, say, 100 quadrillion years, then all the light that would ever enter the black hole for all that time would be seen by you all in a moment.

0:00 Introduction
2:11 Karl Schwarzschild
4:48 Earth compared to a White Dwarf
5:57 The size scale of a Neutron Star
10:41 Escape Speed if you shrank the Earth
12:54 Schwarzschild Radius
16:36 The Event Horizon
29:18 Gravitational Redshift
31:29 Gravitational Time Dilation
36:24 Spaghettification
37:40 Gravitational Lensing
40:50 Spiraling into a Black Hole
43:42 What's inside a black hole?
46:44 Measuring Spacetime Near Massive Objects
55:58 X-Ray Binaries
56:59 Black Hole Candidates
57:55 Observational Evidence for Black Holes

[GypsySun-miwi]

Great lectures and I really appreciate the NO commercial interruptions.

[richardgraham]

I've watched this at least 50x, and still learn from it, as it takes awhile to mentally process. Darn interesting, and thanks for creating this content.

[Eztoez]

Absolutely brilliantly explained. What I love is that you take your time explaining things. Channels like Arvin Ash, Science Asylum, PBS Space Time, ParthG, etc are all great but they cram in complex physics topics in 8 or 15 minute videos. Hardly enough time to absorb what they're saying. I love your feature length videos. You explain things that the non expert can understand, yet detailed enough for those with a rudimentary understanding of physics to still find massively helpful. I've only just discovered your channel. Please carry on the good work.

[KF]

The part about space time itself flowing into the black hole does an excellent job in my mind at explaining why the light speed coming out from the gravitational area outside of the event horizon is slowed down. It's the speed of light minus the speed of gravitational attraction. That's super cool.

[CatFish]

Curious: everything being torn apart by tidal forces as it falls into a black hole. Is this true of fundamental particles too? Do single electrons experience tidal forces?

[jage]

Jack will never make it to the singularity. He (or whats left of him) will stay just below the event horizon while time rushes "above" him. Eons will pass in an instant, and eventually he will be ejected in form of hawking radiation, or be flung out at the definite "end of times" when enough mass has evaporated from the black hole, when the outward pressure wins over gravity.
I have absolutely nothing that supports this, just a gut feeling. ;)

[nfarnell]

First thing to say is beyond the event horizon reminds me of the first rule my economics teacher pounded into my head. You cannot use micro rules to solve macro problems! If space/time is the thing that every thing else is a Feature of, then when the denominator ( Time ) becomes zero all bets are off.. If the event horizon is in fact time equaling zero then there should be a thin shell ( Plank length or 2 ) of stuff falling at zero speed. Anyway thks Jason for taking the time to try and teach us, and forgive our assumptions.

[mikeclarke]

I really don't like physicist saying, "pass neutron degeneracy pressure the star will collapse all the way to a singularity". How do we know there isn't another stage, for example quark degeneracy or even Higgs pressure? Even better what if they DO assume it's at some finite radius and work a GR and QFT theory from that, does that help?

[RxTx]

Jason love you're lectures! They are rad although I'm not quick enough to understand or visualize ALL material! Still fun, on this lecture I was at wonder if Jack would not "feel" the gravitational tide ripping him apart. Wouldn't the gravity prevent the electrical pain signals also be torn towards singularity, never reaching his brain?

[reginaldbauer]

If mass is converted into a length and space is "longer" near massive objects, then how would you apply this concept to black holes? Also, if mass is the thing toward which spacetime is flowing, then what kind of spacetime flows (i.e. curvatures) are being produced by any given black hole? There must be some terminal point to a given black hole, albeit an immense distance (but not infinite), correct? Further, if space(time) flows faster than the speed of light, as suggested, since it is not a "thing" (without mass?), then spacetime is pure energy? Dark energy? And since black holes convert mass into energy (gravitational waves), then mass/matter is not lost to a black hole (nor lost to the universe) but is converted into a form of energy (i.e. the gravitation waves)?

[thetobi]

...for more than 3 years, YouTube waited to send me your way. I'm so glad it did! Near college level lectures explained just simply enough for most average folks to be awed while going in deep enough into the math and physics to still teach space nerds like myself :)

[raybo]

Great series of videos, thank you very much!

[jainalabdin]

I liked the analogy of spacetime flowing like water if you consider that with spacetime being flat rather than the usual depiction of it being curved. And this flow shows the direction of gravitational flow. One question I have is that can you have negative mass that changes this direction of flow? Or if you consider your typical spacetime picture of concave troughs caused by large masses, why don't we see convex peaks? Could such phenomena push spacetime flow as to account for the universes expansion attributed to dark energy?

[daremagare]

Well is than alright to assume that probably singularity is the most luminous object in the universe but in a region around it its gravity puls with such speed that exceeds even speed of light?

[WildGrapevine]

enjoying the videos Jason, thanks! so in this one, there seems to be a discrepancy in the equivalency principle, maybe just in the example. say there's Jill's lab free-floating in space. then there's Jack's identical lab free-falling towards an event horizon. wouldn't physics then be actually different in Jack's lab, so he could tell "uh oh, gravity gradient detected! lab falling into a black hole!, " because Jack would start to feel being stretched before his imminent spaghettification?

[amedeofilippi]

I wonder wether, at least for rotating massive stars, the constant angular momentum could lead, during the shrinking of the star, to a certain balance between increasing centrifugal force and gravitational force before reaching the Schwarzschild radius thus avoiding BH formation.

[ipsissimus]

If the gravitational energy density is high enough for spontaneous particle creation at the Schwarzschild radius, then this must also occur at smaller distances. Does this connection between massive energy density's and particle creation have any implications on the beginning of our universe?

[innertubez]

Why wasn’t the gravitational time dilation of the universe infinite at the Big Bang? Seems like that moment should have taken forever.

[kalles]

Well why do we see the bright accretion discs near the event horizon of a black hole, if the light coming from the infalling matter is so incredibly redshifted?

[මලින්දසමරසිංහ]

Wonderful Sir.very important and informative .thank you