I feel like every time we see a Penrose diagram in Spacetime, it is slightly larger than the previous one.

I'm disappointed that the ring singularity wasn't called a "ringularity"

"Multiverse cartography..." This is gonna be one of those hard mode episodes, isn't it?

*Before watching* "Yeah, I think I'll understand a little of this..." *After watching* "I can feel the warp overtaking me... IT IS A GOOD PAIN!"

6:51 "Our balls, and the geodesics they follow, rebound and travel back out." -Matt O'Dowd, 2020

"this may sound fun, but there's the inconvinient fact of your utter obliteration" got a real chuckle outta me

This is an especially great video, even by PBS-ST standards.. I've been waiting for this one since pt 1, and it didn't disappoint. Love the stuff on the inner structure of the Kerr black hole especially, there's next to no information about this online that doesn't require a graduate-level (or higher) understanding of math/physics to even be able to read.

"Our balls, and the geodesics they follow, rebound and travel back out." Haha, you tease!

Can I get this Penrose diagram embossed on a towel? I'd like to pack as light as possible for the trip...

"Repulsive naked singularity"? Way to give the singularity body image issues, Matt.

I've been staying home, dealing with depression, everything is just kinda 'meh' in my life... And then this. No idea why, but I got so excited while watching this video! I muttered to myself multiple times in an effort to actually understand things, 'rewound' (is that word even used anymore?) probably a half-dozen times to make sure I really took in what was being said... This made me so happy. I'll never truly *understand* most of these videos, but it's so so fun to watch and think about anyways.

Am I the only one that laughed uncontrollably at "this may all sound fun but unfortunately theres the inconvenient affect of your utter obliteration" @11:10

You know you're in trouble when an astrophysicist calls you a nerd.

When travelling the Multiverse, always remember : Don't panic and always carry a towel.

Well, this was an unexpected place to come across a Mage: The Ascension reference. Thanks, Matt! We actually have a Kickstarter ending in about a week for a deluxe edition of our upcoming "Technocracy Reloaded," so please do check that out if it's the sort of thing that interests you.

This is absolutely wildly interesting and elegant, I can conceptually comprehend maybe 19% of the whole concept at this time in this version of this existence in this universe.

T-shirt idea (from 8:05) - "Naked Singularities are Repulsive"

*My Brain at the start of the video:* “Multiverse _[Captivating Scientific Gibberish]_ . In English this is *[Captivating Scientific Gibberish with a hint of English]!* ”

Question: So now that you've got this figured out for us, how about showing us what happens to matter and space time within these boundaries, but during a black-hole merger? Please and thank you :)

"nerdery".... as of today, definitely one of my favorite words! 🤓🔎

I just found out Matt O’Dowd is almost 50 years old. Which of the time machine options have you used to look 20 forever?

: Reads the headline: - yeah... I'll definitely understand this...

Thank you to you and your team for producing these videos! They've long moved past my understanding, but I enjoy them all the same! If we had physical access to a black hole what are some experiments that could be done that could advance our understanding of space time?

Kudos to the guy that went out and mapped the multiverse for us to see.

Matt: You're inside the inner erogsphere and could die. Me: Haha spinny lightspeed ship go brrrrrrrr...

Yes lads, good to see everyone checking in nice and early.

I love your visualizations and the sound design. Great work!

Good luck with that map, Google.

Don’t you mean “the multiverse of madness”? Also, I’m guessing the hitchhiker’s guide to the galaxy isn’t gonna help me with these new universes?

Episodes like these are what Space Time is all about (or what got me into watching SpaceTime).

“Let’s push a little harder and try to get through the ring”

It just feels like you're explaining how the universe is gonna start and end over and over again.

Wait, where is the bookshelf in this diagram? I need to float to behind the bookshelf...

Thanks Matt. I just watched a lecture by Sir Roger Penrose at Gresham College and had to watch your video again in an attempt to learn a bit more. Turns out quite a bit more. Thanks again for your time and work putting it all together.

Very interesting, informative and worthwhile video.

"Our balls, and the geodesics they follow." (6:51) I chuckled.

Haven’t watched it yet but I don’t get it.

You’re the man I learn so much from watching your channel. I am going back to college for physics. Thanks for the inspiration!

KZfaq why is this not trending? instead of cosmetics or personal life related vlogs!! this video is so well made and qualifies as good infotainment!!!

“When your balls rebound...let’s push a little harder” - not a TOS violation, I swear!

Nobody warned me that we need drugs to watch this episode.

Well, had to watch that one twice. Wow. Fantastic explanation. Thank you.

I BLOODY LOVE SPACETIME!!! You guys are brill!

*Takes plunge into black hole* God I wish that were me.

It's really strange watching videos from a channel for years and barely understanding a thing. But I have to keep watching, it's so interesting!

It's videos like these that make me love the Universe and it's rules because you can exploit them to do all kinds of weird things

mindbogglingly conceptual yet, startlingly intuitive

Last time I was this early, all fundamental forces were unified

When a topic on this show has a black hole and Matt talks about space and time switching. The end should be time-space instead of space-time

In the best scenario, it goes in a loop, and it's still infinite, but it ends up back in our universe at some point. Also, the thing about space and time switching roles creeped me out. I had dreams about it. Thankfully, I'm glad the ergosphere gave me a boost out of there in those dreams.

Can you guys do a video on naked singularities, or the anti gravity universe you get into by traveling through the ring's wormhole?

"Now you're thinking with portals"

9:55 The extra "l" stands for extra parallel.

so..when does Hollywood make a movie inspired by this episode?...what a wild ride that would be!

Great cartography skills. Recognized my home stright away just from the thumbnail! P. S. I believe i was lost once outside that map.

SPACETIME! Day saved! Edit: This broke my brain. More than any other PBS Space Time episode. I will have to re-watch tomorrow.

happiest moment of my day: seeing a notification from this channel

It's nice to have followed up all the videos leading to this one and joyfully understand 1% of this one.

Your explanation of complicated science would make a great setting for star trek episodes

Penrose has also recently extended the diagrams to the left and right, in the Conformal Cyclic Cosmology model. Are we going to have an episode on that?

We’re about 50 iterations off the Finite Central Curve.

Again I have the feeling that if I whatch it 100 times I will get it... So it is not possible a white hole existing or matter going trough it but is possible that the fabric of space itself can go through it? If that will be possible, it will make sense that the big bang could be a white hole that is accelerating the fabric of our universe by pouring "space" into our universe "from another universe" and we will never be able to see it because it is in our past? It's a total non sense I know just curious and ignorant. Great episode.

What does it mean to "fall" and "inside" mean when one crosses a black hole event horizon where, what was a space dimension intersecting the singularity, is now a time dimension that I presume now intersects the singularity?

This video turned me into an unstable genius

Sam: "DESTROY IT!" Kerr: "No."

This is among the trippiest videos I've ever seen . . .

Exactly: above the limited event horizon of physics is the spectacular ergosphere of Philosophy!

>”or maybe hufflepuff” If this guy isn’t ravenclaw, ravenclaws don’t exist.

When you think you understand, then you have to start watching all of the videos in the series again to figure out where you got lost.

This is... absolutely crazy. Spacetime/timespace-based reality... And thus, the opposite of gravity is intertia. And velocity is the quintessential component of existence - as a passionate driver, I love that.

this is my most favorite channel about quantum space time. Makes me feel like I understand it, even if I cant 😅 Still, a lot of fun to watch

i'm totally imagining a sci-fi civilisation that teleports "singularity-mills" directly past the inner horizon to extract energy from the inner rotation, which would somehow be entangled to some turbines outside the black hole to make energy None of it really make sense but it sound too cool so I need to create some lore around that. The madness of physics is just so much of a infinite well of inspiration

Lets take a moment to appreciate everything Penrose has done for the advancement of our understanding of space-time, and the surprises that he might still have up his sleeve in his ever-ongoing research.

One of the most interesting Concepts have had the pleasure to think on. Thank you..

Wow, super interesting! i've been thinking about this video for several days now

A note on the mass inflation instability: Out of the two perpendicular inner horizons in the diagram, only one has the instability if the black hole is not eternal. I.e. in a realistic scenario of a black hole which appears due to gravitational collapse, you can (sometimes) cross one inner horizon and get to the singularity without worrying about mass inflation. Also, at the horizon with the instability, backreaction seems to result in what is called a "weak" null singularity, "weak" because there are no divergent tidal forces and the geometry is extendable beyond it, so again not too much of a problem.

Sooooo technically i can with my trusty map get "back" to the origin universe by going forward until i find a replia of it due to being able to go forward to new universes for as long as i want ... Got it.... Thought experiments aside, how would all this look like if we hold to our "knowledge" of not being able to exceed the speed of light in the torus on the other side of the ring singuularity, does it only do away with the time travel or the entire white hole part?

~ A blackhole that has no spin or charge is basically neutral/static, it basically consists only of a mass constituent. A neutral/static blackhole is essentially a wormhole without an E.M. energy jet stream. ~ A blackhole that has spin or charge has motion due to induced energy, so it is not a neutral blackhole but instead a dynamic/energetic blackhole. It is essentially becoming a wormhole that has both motion & spin because of centripetal & centrifugal forces that are caused by induced energy, with more prominent Grav. blackhole & E.M. jet stream characteristics. ~ The more extreme the mass of the Grav. blackhole vs the more energetic the E.M. energy jet stream, the more prominent & extreme their mass/volume (density) characteristics become. ~ A neutral wormhole has a Grav. mass accretion disk & E.M. energy volume jet stream which are both in balanced density equilibrium. The matter mass vs energy volume ratio is balanced/equilibrated. A stable wormhole supports a peaceful existence for life. Our solar system is close to being in this state, therefore it supports life as we know it. ~ Inertial Permittivity x Potential Permeability = Static/Dynamic Kinetics. ~ (Grav. Mass Accretion Disk Blackhole) / (E.M. Energy Volume Jet Stream) = Static/Dynamic Density Wormhole.

"I've always thought of myself as more Order of Hermes" 17 min talking about black holes, relatively and the multiverse, not even a passing mention of sympathetic links, destiny or the spirit planes: You're not fooling anyone, Technocrat. Keep up the good work, though, this was very enlightening!

"Order of Hermes, or maybe Hufflepuff." Man, if you thought the Mage RPG folks were coming for you before...

Question: As black holes are said to evaporate (something that I assume also applies to Kerr black holes), and space and time switch places beyond the event horizon, would the effect of passing through the event horizon effectively be the process of this evaporation? As you (a 3 dimensional object) pass through the Kerr black hole and are annihilated by these incredible forces, some of this energy and information is deposited in the form of energy during evaporation. So the white hole is actually a mathematical representation of this process of energy conversion. In essence, the question I am asking is how much of this changes when not dealing with an eternal black hole? Is it simply interpretational or is it possibly completely different?

Ring singularity leading to the Bizzaro-verse... I freaking love this guy!! LOL

I've been really looking forward to the penrose diagrams, to mapping beyond the event horizon-your episode 'how blackholes spin spacetime' was a favourite of mine. So lucky to have this exceptional quality science channel available for free-thanks to sponsors. This channel and fermilab are the only ones I watch, with the latter always beginning with mathematical equations on a chalkboard-with a university lecture feel to it. PBS spacetime deals with more higher concepts-taking physics equations to their absolute extremes, and seeing what happens, in a way that is both accessible yet not watered down like other channels do-you include the meaty details incl equations. You amazingly achieve presentations that undergraduate and graduate physics students enjoy, amateur physics lovers, the complete astrophysics novice with reasonable intellect level,and ive even seen professors of physics to enjoy them. unfortunately like with fermilab there are always the few idiots who will write to fermilab every week claiming they have found something that proves special relativity wrong e.c.t. yet lacking the rigorous scientific education or ability to apply rigorous scientific method to even be in the discussion. Such people should be humble and engage with these high concepts with a childlike awe and wonder, with a desire to learn, reading up on more basic scientific principles-for example i am eager to have an intuitive grasp of the mathematical equations that come up in these video presentations and in the science journal papers i read every week, the latest being arxiv.org/pdf/1312.2007.pdf, and arxiv.org/pdf/quant-ph/0105101.pdf, that latter one is my favourite current physicist Yakir Aharanov. so i want to start calculus one, which physicist isaac newton is famed at having invented-allowing him to write his laws of motion, including his 'universal gravitation' and before that i am currently reading a comprehensive book on algebra, geometry and trigonometry-pre calculus to ground myself, as my maths level is embarrassingly low-maths is a use it or lose it skill, like foreign languages. an eight year would beat me at any maths in a test right now. My primary 'obsession' is with spacetime geometries, and the nature of time and time travel using quantum physic and SR plus GR.With the sudden surge in disinformation, a tactic for example disinformation is the primary technique deployed by the russian federation under president putin to toy with the west, with its russian state newspaper inventing a story about hitler's 'mein kampf' being more popular in latvia than harry potter. and this was payback for latvia being now a part of the west, a part of nato, which russia hates, and feels encroached by. And disinformation is rife from the American and British governments during this coronavirus pandemic. and from religious fundamentalists. That is why getting science from authoritative qualified sources is essential.

He is not a man. He's the holy Half-Dead who has seen the UnderVerse!

Been waiting for this episode a long time; seems you guys have a lot of stuff on your mind! Great video, by the way. Also, can you please print this map on posters? I would totally buy it, and so would other spacetimers. Edit: Also please print it on a towel as quite a few people want it. _(Insert reference to A Hitchhiker’s Guide to the Galaxy here)_

I love this series, including this one ...which is way beyond my understanding. I’m just trying to figure out if I need another beer or not.

Wow, this video is so well done !

This time I really do think you made everything up.

The Penrose diagram image at :40... I want that as a black light poster please.

VERY eye opening video. Thanks 😊 I totally forgot about penrose diagrams...

6:16 No, this is not correct. It's easiest to see this in the Kruskal-Szekeres coordinate or the Penrose diagram. Also, space and time do not change directions, this is just an artefact of a strange coordinate system being used (namely, the one that results from first arranging the yet unknown metric into a diagonal form which is done merely to make solving the Einstein equation easier, or even possible, in a closed form). Such coordinate systems are singular at the horizons and due to a quirk of the mathematics involved, the letters labelling radial and time directions end up being reused at the resulting disconnected patches. But this is just a bit of notational laziness. Hawking and Ellis in their book try to counter this by switching the letters "r" and "t" for the interior portion of the Schwarzschild metric, for example. 7:33 It does not "become" repulsive. The ring singularity is gravitationally repulsive on both sides of the disc. The mass is not "negative", it's just that the radial coordinate labels become negative. Same thing about the "nakedness" of the singularity: it is so on _both_ sides (once inside the inner horizon), not just inside the "negative space". 14:15 This is very commonly asserted but it's just not true: Einstein was very likely not even aware of the Michelson-Morley experiment (USA was a scientific backwater then). His motivation was different: he was trying to resolve the infamous conundrum of Maxwell's equations not being true in a uniformly moving system. Since Newtonian mechanics obviously is not like that, and mechanics was supposed to be an effect of the microscopic electric and magnetic forces, this drove everyone crazy. His 1905 paper was in fact about justifying why the electromagnetic fields E and B were _physical_ after a Lorentz transformation (before him everyone assumed that those transformations were only mathematical curiosities). This was _the_ main conclusion of this paper in which he demonstrated how this reality of the transformed fields resolves the magnet-and-coil paradox he sets up in the introduction to the paper. But, as it very quickly turned out, probably within weeks of the publication, it was the first, kinematical (introductory) part of the 1905 paper that was the smoking gun (special relativity). So today hardly anybody even _reads_ the actual main (second, electrodynamical) part of the 1905 paper.

I've always been a time traveller. Going at a steady pace of one second per second.

Does this mean that I can now get in my spaceship and start my promising career as a space cartographer?

Deadpool: breathes a sigh of relief at his balls rebounding out of the Ring Singularity

13:56 Almost forgot! Thanks for reminding.

Just to clarify, this concept of “multiverse” has NOTHING to do with the multiverse predicted by quantum physics, right? If there are two universes, one with the alive, and the other with the dead cat, I cannot use a black hole to travel from one from the other, because that is an entirely different concept, only the naming is similar.

At every horizon is associated a Temperature, since Kerr (and Reissner-Nordström) Black Holes have two horizons an observer in the region between these two horizons does see both radiating?

Love that Mage reference in there!

Ergosphere surface and event horizon diagrams are almost correct. The event horizon is the spinning sphere that we are contained in crumpled up inside. You learn how all of them are contained based on their spin and angels should line on at one point within our galaxy. Somehow I believe the forces line in some orientation towards or away from the great attractor. That is one of my crazy ideas.

Psh, Everyone knows that the fifth element is love... It's how we got our moon.