At the limits of astrophysics - with Katy Clough

Why does modern astronomy often sound like science fiction? And how do objects like supermassive black holes, wormholes and warp drives fit into our current understanding of physics?
Watch the Q&A here: • Q&A: At the limits of ...
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This event was recorded at the Royal Institution on 23 March 2023.
Much of modern astronomy sounds a lot like science fiction - gravitational ripples in the fabric of spacetime, supermassive black holes hiding at the centre of galaxies, habitable exoplanets within the reach of our telescopes…are there any limits to what is out there?
Whilst largely considered to be firmly in the category of fiction, such concepts are nevertheless based on solid scientific ideas about the curvature of spacetime from Einstein’s theory of general relativity. This theory is known to be hugely counter-intuitive, giving rise to singularities, event horizons and time dilation around black holes. In strong gravity regimes things behave very differently to the low gravity environment on the Earth, so our intuition, which is based on our everyday experience, can mislead us. Studying these objects can help us to challenge our understanding of what is “natural”, and better understand the extreme limits of gravitational theory.
Katy Clough is a lecturer and Ernest Rutherford Fellow in the School of Mathematical Sciences at Queen Mary University of London. She studies systems with strong dynamical gravity using numerical simulations, including black holes and the early universe. She is part of the fundamental physics working group for the future space based gravitational wave detector, LISA. Katy’s first degree was in Engineering and her degree in Physics was obtained from the Open University whilst working as a chartered accountant. After her PhD at King’s College London she worked in Goettingen in Germany and in Oxford University in postdoctoral positions. She believes that science is for everyone and that there is no right way to be a scientist.
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[@georgeangles6542]

There is no limit to how long I'd be able to listen to this woman speak. She's great💪💪

[@tormodguldvog8405]

She is one of the best lecturers I have seen in a very long time. She is so cheerful and explains difficult concepts so easily. Captivating and well done!

[@Vaeldarg]

She was a bit quick when going over the "Novikov consistency conjecture", probably because it's so much closer to being correct than what many physicists WANT the answer to be. If this conjecture includes the trope of "the universe has some active system preventing past events from being changed" then yeah that part is clearly wrong. But the present is made from the events of the past, including anything a time-traveler did. The gun doesn't jam, because the time traveler can't kill someone who is somehow just meant to survive: the would-be victim survives into the present BECAUSE the time-traveler's gun jammed in the past.

[@techslugz]

I agree @Tormod Guldvog Absolutely amazing lecture, I really am enjoying it. She is great! And gives off such a lovely and friendly vibe.❤

[@techslugz]

@@iridium8341 why does it matter what gender a lecturer is?

[@ahsanmohammed1]

Yes. Good flow and rhythm.

[@uneducatedguess6740]

Chat GPT can spread mainstream/ignorance. What it cannot do is show how triple mistake in Hubble law can plunge humanity into Dark Science for a century. Check: Medium: Time Speeds Up In The Universe, By What Formula?

[@Syntax753]

Lately, have been delving into learning more about astrophysics/quantum mechanics - and the RI impresses with every presentation. The lecture format with live demos always manages to offer alternative representations which has influenced my understanding across the videos. Coming from a classical maths background, I particularly enjoyed this one! Thank you for all the hard work putting this together! I still love you Newton ☺

[@punditgi]

Brilliant presentation! ❤🎉😊

[@rbee6507]

Every so often, I hear a discussion of this level and somehow it brings me an even higher level of enlightenment, curiosity, and inspiration! Amazing presentation, delivery, and insight. I agree with you wholeheartedly in your interpretation. Considering gravity as a force absolutely limited my thought and I hadn't even realized it before hearing you! Don't you worry...I am confident it will catch on very soon. Thank you SO much! All the love and appreciation to you Katy! This completely changed my way of viewing even the things I already knew. I wish you much success and discovery.

[@ahsanmohammed1]

23:00 An astrophysicist saying, “I've got no sense of distance,” sounds a bit off to a layman like me.

[@_eduardolps_.7361]

She's a splendidly captivating lecturer. I would move to the UK just to hear her speeches on this matter. BTW, knowing not only Astrophysics' possibilities but also its limits is a wonderful way to acknowledge the place of science in our society. Could it possibly solve all of our problems? I hope to cherish new "Katys" Clough in action

[@mariam_tigress]

I love how nonchalantly she talks about time space - like, we can fold it, no problem, it's punching through that is difficult

[@davetubervid]

Brilliant. I usually give up on these types of videos well before the end because I simply can't follow them. I am fascinated by cosmology but totally out of my depth with physics and mathematics. (yes, I am a humanities graduate for my sins). This however was totally understandable, partly due to the brilliant teaching style and personality of Katie Clough, and indeed the whole approach of other lectures in this RI series.

[@JoimFormula]

Kip Thorne should be credited for the accurate black hole visualization in Interstellar movie

[@real_DrDummkopf]

As many of these I've seen as well as world science festival I've never actually explored the comments area of it and it paints a better picture other than just trying to get my own understanding. Thanks a million

[@savage22bolt32]

I find a lot of interesting ideas & opinions in the comments section. Take them with a grain of salt, as they say. But reading comments enhances the the whole shabang.

[@stevefromsaskatoon830]

Reading comments is by far my favorite thing about the internet

[@abdessamadhasnaoui6887]

I loved the lecture.. Thank you for explaining these valuable things And thanks to Thé Royal Institution for making these lectures accessible for free And know that you researchers are and will be forever the best people thar have ever existed😃😃😃

[@laurajohnson307]

This research is so up my alley!! WOW I love your lecture also :) I was born in Reading England currently in the states.

[@toma5153]

A very enjoyable and practical lecture. I encourage more lectures like this.

[@orangetee5]

Loved it!! Thank you 😊

[@MTSVW]

This is the first time I’ve heard gravity explained as a product of curved time in a way that makes sense. I love the analogy of two people hiking north and meeting at the North Pole, and it looking like a force pushing them together even though it really isn’t.

[@joskeguereza3714]

it doesn't really work though, if ONLY the north-south dimension was curved and the east-west dimension wasn't, then the students would never meet at the northpole. So i wonder if that means that both space and time have to be curved for it to work? interesting analogy though :)

[@cloudpoint0]

It works if you choose an appropriate coordinate system. But curvature is purely a function the coordinate system you chose and not of the physical universe. Imagine an East and West Pole on Earth instead of the north-south coordinate system we have adopted, and indeed you can keep going north forever.

[@davidgould9431]

​@@cloudpoint0 In your example you can't keep going east or west forever. On a sphere, when you set two people off locally parallel and they keep going according to their local metric, they will always meet. Calling it east, north, banana or whatever is arbitrary: any two parallel travellers will eventually meet.

[@cloudpoint0]

​@@davidgould9431 The equator, the two tropics and the two polar circles never cross. Any two people on any of these separate paths will never meet. East and west are indeed forever since in the coordinate system we use on Earth there is no East and West Pole. "Locally parallel" is a semantically defined term that has meaning only in a specific coordinate system. Two people heading North on the curved surface of the Earth are not on parallel paths. They are headed toward a common arbitrarily defined coordinate point. They just think they moving in a parallel way because of the way words like north and south are defined.

[@davidgould9431]

@@cloudpoint0"Semantically defined term". That's what semantics is: definitions. And coordinates have nothing to do with it. Coordinates are arbitrary and convertible one to another, so that's a non-starter. When talking about parallel lines, it's generally understood to be about straight lines which, on a sphere, are great circles. So lines of latitude are, on the sphere, curved because they aren't great circles. For example: concentric circles in flat, Euclidean space don't ever meet but are only locally parallel, not globally parallel. If you start two people pointing on lines of latitude and get them to each walk along the great circle in their respective directions they will meet. If you want to "semantically define" parallel according to your preference, that's fine: have a ball.

[@gidi1899]

16:50 - how to explain to 2 galaxies moving away from each other: 1. they have different initial speeds 2. they have different mass 3. they are viewed rotating on a sphere from inside the sphere

[@andreadelucia4969]

Such a wonderful and pleasant explanation, very kind, nice and professional at the same time. Thank you so much

[@robertspence7766]

Excellent talk about a complicated topic!

[@crazywickedcustoms7272]

Thank you , I learned alot

[@bilinguru]

The universe is not expanding, but curving in the time direction. Love it! First time to hear it expressed this way, and it really helped me visualize what's going on.

[@adairjanney7109]

except none of it is going on, they wont admit they made a huge error years ago which is why everything is so confusing, the CMB isnt real and most of the data that they base all of this on comes from data from the CMB which isnt even real, they never detected it at L2 that signal comes from the hydrogen bond in water which is why they should have known better when cobe got such a STRONG signal in polar orbit, it should have been a red flag but they didnt care

[@yanikkunitsin1466]

Oh, it's Mitch more complex than that.

[@adairjanney7109]

it isnt doing any such thing its all lies, the CMB doesnt exist at all they MISCORRECTLY applied the hydrogen bond to that signal and they wont admit it even though its beyond obvious and very provable see Dr Robitille for details. This is why cosmology is so broken

[@danielpark4028]

This is so great Katy, moving in curved time is a really good analogy 👌🏼

[@elenalosseva4912]

Amazing lecture!

[@vinnyvdalidemonet8527]

Dr. Clough did a fantastic job. Her explanations gave me a much better understanding to the space/time principles. She is a really good teacher. Her passion is contagious.

[@savage22bolt32]

I wonder where that famous desk has gone? Perhaps a little refinishing?

[@andycordy5190]

Well worth watching for the visualisation of a black hole. The notion that the black hole is an area/volume of spacetime where/when mass density is so great that a singularity is created. In a manner of speaking, it represents the opposite of total vacuum. Thinking about Katy's idea of the universe expanding into the apparently infinite future, works perfectly with looking back into contacting, finite past time. Lastly, it makes sense that continual paths on an evenly curved spacetime must converge but what/where/when is that convergence?

[@kano6325]

❤❤

[@dodatroda]

That makes no sense at all.

[@revitdviser4769]

Watched the whole video in one breath. Talented speaker.

[@vladimirp2674]

Astronomically speaking, this is a bright one lecture! Space and time are actually questions, that i firstly met during my school days, when i went through primitive books, that historically speaking, become quite obsolete and old-fashioned, even pretty ridiculous, when i have a jerk to remind myself, how first things about physics were explored to me, so i rarely moved towards old stuff, on the other hand, such an inventive and wise approach, naturally, reorganized my knowledge though i am not these days particularly into it. Well done!

[@ExecutiveChefLance]

I studied Biochem and Microbiology but been hardcore into Quantum Physics and Cosmology for past few years. And currently I am obsessed with the fundamentals. Hate the Copenhagen Interpretation. There HAS to be A Reason even if that reason does point to why Probability is a Fundamental Building Block. I think if we truly understood these questions it would point to obvious answer in Cosmology. My opinion is Energy itself can only exist in the form of EM Wave. And that the transition of energy to matter around the Big Bang is what gives us the Perception of Time. (What Spacetime is, Why it warps when Matter is present is another crazy ) Therefore if you can see a standing EM Wave you aren't moving Forward In Time. Given that Energy Distribution is the Basis of Entropy. And High Entropy means Hidden Information. Energy itself reveals Information. So it makes no sense to be able to SEE Energy. At the basis of Energy is just Vibrating Quantum Fields. Energy is like a Movie and the Observer Effect is like seeing a slice of that movie. So we see it as Particle Nature. All entropic relations go from High Stable to Low Stable with an intermediate Chaos. That is what we see in the spectrum of Nature between Waves or Energy and Matter or Mass. That Intermediate Chaos, the Probability or what some QM Scientists refer to as Choices that split Realities. Its like a Law of Nature. You cannot have 100% determinism or Energy and Time itself doesn't make sense. Sorry for the rant just drank a really strong coffee. Maybe in 20 years I can hammer down the details the of my Universal Law of Energy, Time and Determinism.

[@NeonVisual]

I see gravity as a curvature of causality. Matter has a causal relationship with other matter such as quantum fields interacting, molecular structure, and the more matter there is clumped together, the more complex interactions arise. For example on planetary scales like Earth we get really complex interacting systems like weather, plate tectonics and even life. It seems that the more matter is clumped together, the harder the universe has to work to allow all those interactions to take place, analogous to a really complex 3D simulation in a computer. In that analogy a computer's rendered framerate may drop as the rendering becomes more complex. I believe something similar is happening in the universe, and so to maintain causality and and the constant speed of light at which those interactions occur, the metric which has to bend is the rate at which time flows. For you sitting near a black hole's event horizon time appears to be flowing normally as you're next to an extremely compact clump of matter, but for everyone else it looks like time has slowed down for you, again the lowered framerate analogy. Causality has become curved the closer to the clumped matter. So I think if the universe didn't do this, then the only other metric which nature could alter is to increase the speed of light near clumped matter like overclocking the computer, but this would create causality paradoxes, and obviously this isn't what we observe. Furthermore, particles which don't have mass can't create complex interactions like regular matter, and so they don't curve spacetime at all, but are still affected by the slowdown in causality near matter and so are apparently bent by gravity. So, gravity is in essence the apparent local reduction of the rate of causality relative to flat spacetime in the presence of complexly interacting baryonic particles.

[@rang069]

Can you elaborate on the concept of causility as you have it in mind here?

[@yungsookevinhong7943]

Space time curvature is layer and layer sheet stacked or could it be explained as it’s density change, it is the high density to the low density to balance the spacing evenly. The universe is condense of physic. Therefore its has to balance to the low density as explain as the universe expansion phenomenon.

[@QuesoDePalo]

Beautiful!

[@Feenix102]

Is the stretching of space-time in the warp drive colapse in any way analogous to the spaghettification phenomenon that would be expected to happen inside a black hole?

[@richardcaves3601]

Depends on mass applied. Also on size of warp bubble. And on size of power/energy input.

[@mooseyrambling5838]

Well done Katy, Brilliant, really enjoyed. thanks.

[@paulgrosse7631]

Time-travel films - try 'Predestination' You will love it: One timeline; Novikov-consistency-conjecture proof; Chronology is proected; and, the physics is interesting.

[@Ryan_Hokanson]

Excellent & nice.

[@sns8420]

How does mass bend Space-Time? Does Space-Time exist if there is no Mass/Energy?

[@VijayGupta-cz4ef]

In PicoPhysics the observations leading to some conclusions like space curvature, Potential energy, exploding universe and propagation, reflection and refraction of light are all related to understanding of space. There is a mis-conception about what space is. In PicoPhysics space is the identity that is not Konserved. Konservation is Conservation sans neutralization. Though this characteristic of space can be mathematically/logically established, to make it easier to understand, it is incorporated as Unary law "Space Contains Knergy". With this as fundamental law of nature, we don't need such weird concepts as curvature of space as if space is some rigid curvy identity. Note: No. of spatial dimensions is derived characteristic of space (Non Konserved) in PicoPhysics.

[@chrissiriska8086]

My one regret about having to die eventually is I will never get to see just how far the human race can go. I want to see how far we can push and test the bounderies of science and the universe.

[@Robinson8491]

Really?

[@tux1968]

Alas, each of us is only a member of the human race, not the human marathon.

[@chrissiriska8086]

@Resh I am unsure of what I would be hoping to see. Mostly, I just want to know what is and isn't ultimately possible I'm reality. As far as where will we be? I have no idea, I'd like to believe we would have moved on from our capacity to destroy ourselves. I'd love to see our first contact with an alien race, if ever.

[@kano6325]

Special relativity 😂

[@kano6325]

​@@tux1968 ❤

[@BeelySalasBlair-uy5wn]

Thank you.

[@phillipcoetzer8186]

I do actually have a question ... space time is treated as one thing when it is two entities if a wormhole is made on the time fabric we travel through time .. if a wormhole is made through space we travel through space ... how does time behave in the latter ... I assume understanding that will enhance our understanding of how time works. And it seems to me a space wormhole is indeed a blackhole ... what would a timehole look like?

[@jimmifoulis]

Understanding space time is very simple. 1 time is perception. 2 time is a number. 3 is form of measurement. So if you understand this space time is magnetic fields flowing at a specific # or time lol

[@jeffroberts6865]

Katy says spacetime for the Universe overall is curved in the time direction so that galaxies mainly move apart as they go through time. This makes sense to me. However, does this mean from a topological perspective it is like a saddle shape? I had understood from previous readings and videos that it was regarded as mostly flat.

[@jeffroberts6865]

She actually answers this in the Q&A video.

[@Triring65]

I believe that the analogy of gravity is curvature of space and is not a force. Even if there is an indentation as acurvature of space, if there is no attracting force between two mass then the smaller mass should be able to stand still on the side of the hill. The only reason mass rolls down the hill is because gravity is actively attract the two mass.

[@JustNow42]

Protest: time do not progress in the empty room. Time is a progression and in empty space there is no progression. There is random energy variations that when you immerse particles in it drive a progression. So the random variations has a spectrum that determine the speed of time when probed. A little like you do not know certain parameters of particles unless you measure them. Is that so difficult?

[@derabidian]

Where does the space curve into?

[@loweha69]

Dr Clough, we need another lecture about what you mentioned in the last minute! :-) Great lecture!

[@stephenjones3946]

Our boundary knowledge is very limited. We are a young intellect in the scheme of things. Physics - has it really moved on.

[@jessech8047]

it was a great lecture for understanding the universe. the theory seems to explain the universe spacetime. my skeptical views lie in how mater and energy cause the curvature. a star like Sun created its own curvature for other objects ( planets) in sky. during the formation of Sun, it got more energy and mater through the process until the current stage of the Sun where energy and mater are not increasing anymore. spacetime did not say how mater and energy can form a curvature, and can the spacetime theory describe characteristics of curvature?

[@alykathryn]

Just tell the kids: No, you can't go into a black hole because black holes bend spacetime so much that, it is always past your bedtime. And you can't cross the bedtime horizon till your old enough

[@rudyvanderhoeven9628]

At last I understand

[@randomdazz]

You may not have to send a signal to the front of the bubble - if you are generating the centre of the bubble from your ship - surly the signal just has to end the generation of it - but be careful it doesn't collapse like in the simulation

[@0.618-0]

So I have one question from this fine presentation, If ime progression 25:47 es in one direction and the shape of time is divergent, and the universe is hubble expanding...is there a causal link between the two Katy?

[@schmetterling4477]

Time is a local phenomenon that has nothing to do with the Hubble flow.

[@0.618-0]

@schmetterling4477 Time and Hubble expansion are linked by Entropy. Time maybe local, Katy described time as producing gravitational effect on matter by warping space in a divergent world line. The Energy of an expanding universe, pushing galaxies away from each other by inserting space in between conglomeration of matter is the second law of Entropy or energy conservation. I think there is a link between expanding space and the arrow of time on matter.

[@schmetterling4477]

@@0.618-0 The best clocks don't use stochastic phenomena. They use coherent energy flow. You need to pay more attention to details.

[@0.618-0]

@schmetterling4477 The world you and I are aware of is stochastic is it not.

[@schmetterling4477]

@@0.618-0 I don't know what you are aware of. Whatever it is, it doesn't seem to match with reality.

[@EduardoRodriguez-du2vd]

In my impression, "curved space" implies a deformation of space with respect to something. But "curved time" cannot be the same and different from "curved space". Curved Time can only affect the pace of time passage. Apparently, she thinks that curved time is the inverse of curved space. There is a problem here with the idea of time. :)

[@yanikkunitsin1466]

You should research basic general relativity concepts. 'Pace of time' is meaningless.

[@phenixorbitall3917]

Brillant! :)

[@billdecat855]

ER=EPR this conjecture interests me insomuch as it somewhat says that wormholes = quantum entanglement.

[@JoimFormula]

Also, Alcubierre should be credited for the warp drive idea

[@saad-kb3er]

What a brilliant exposition! One of the best talks I have heard.

[@yungsookevinhong7943]

Weight is the actually measure of density of matter.

[@garlicgherkin]

No, density is mass/volume, and weight corresponds to just mass. So for instance Jupiter 'weighs' more than Earth (has more mass, over 300 times as much) but because its volume is so much greater, it has only 1/4 the density of Earth.

[@VijayGupta-cz4ef]

Space Curvature understanding on the basis of no force acting on the object - raises the question - why do photons move through space. What is the forcing them to move through space. Why they move with constant speed. Conservation of momentum is satisfied if they don't move at all as well. In PicoPhysics you get the answer to this question. The phenomenon (Space-Knergy interaction) that makes Photons move is common to observations leading to conclusions like space curvature, Potential Energy, exploding universe and propagation, reflection and refraction of light.

[@schmetterling4477]

Photons don't move through space. You simply didn't pay attention in high school when they explained photons to you.

[@VijayGupta-cz4ef]

If you have an inquisitive mind; you question all that is told to you as gospel truth. The first such challenge you come across is concept of potential energy (in the context of gravitation) to keep principle of conservation of energy. This misplaced conception about energy is the basis of all prevailing confusion in Physics - to the extent that now if universe we live in is questioned ? It it really exist or is just an imagination? Confusion about wave particle duality is only a small part of the prevailing confusion. In PicoPhysics there exist no such confusion. It is a simple deterministic theory based on single principle "Space Contains Kenergy". All laws of physics find their origin in this Unary principle.@@schmetterling4477

[@schmetterling4477]

@@VijayGupta-cz4ef I don't have the energy to explain to you how to carry a piano up tp the fourth floor. If your teachers couldn't make you understand, then nobody can. ;-)

[@VijayGupta-cz4ef]

No explaination required - No students are here - all are colleagues trying to understand nature - by listening to others or developing a robust thought process which enables understanding of observations on nature. @@schmetterling4477

[@ahsanmohammed1]

13:00 Two parallel lines going straight meet up at the North Pole? Seems they’re not parallel. Seems they’re angled to point to the North Pole. Shouldn’t parallel lines that start at the equator be going around the earth in perpetual parallellity?

[@hrgwea]

Unfortunately she used a bad analogy to explain space-time curvature. North is a single point, not a direction. Therefore two people walking north will always meet at the north pole because they started walking towards the same point. What she tried to do was to use north as a direction instead of as a point. So, if two people walk in the same direction starting from two different points, they should never meet each other if space-time was flat.

[@jasonhayward6965]

The real problem is PhD are trained to prove with experiments. But workers are trained to solve . So give workers technology to be able to look up the answers study new things and pound for pound the citizen scientists can rip apart and get an answer by solving it . While PhD are really only educating students.

[@chyldstudios]

Excellent lecture.

[@user-fz1nh3mt1c]

it is going to be an extremely curious talk, thank you so much

[@kano6325]

Research scientist has processor

[@brian554xx]

Utterly delightful, and she captures some of the nuances I so often see missed. Nice.

[@gidi1899]

21:36 - I would like to say "Nothing bigger/heavier/softer than light can travel faster than the speed of light"

[@ImtiazKhan-xk9nh]

This may be a stupid question, Katy explained that in 3d Spacetime time dimension is bent bringing the 2 students together as they move from Africa, so in 4d time this is bent which should bring convergence? further in her QA session she replies that time dimension derives this bent force from Dark energy, The very property of dark energy is expanding spacetime so isn't this counterintuitive? Dark energy is the very constituent of spacetime, so who is moving whom?, which came first? aplogies for my ignorance

[@yanikkunitsin1466]

Dark energy, unlike say gravity, is a 'placeholder' term to explain discrepancy in calculation and not very well understood physical phenomena that we can detect and make experiments or link to other things.

[@rogerphelps9939]

The other fundamental forces are mediated by particles specific to the force. To say that mass or energy concentrations cause the surrounding spacetime to be warped really begs the question. What is the mechanism? Gravitons are theorised to be the carriers of gravitation but if you accept that, isn't the concept of warped spacetime superfluous?

[@sunroad7228]

E=mc² - If it is a constant, then all the universe would know about it - Mass, Energy and all the rest... "A derived Value must not violate the Concept of its Value. In any system of energy, Control is what consumes energy the most. No energy store holds enough energy to extract an amount of energy equal to the total energy it stores. No system of energy can deliver sum useful energy in excess of the total energy put into constructing it. This universal truth applies to all systems. Energy, like time, flows from past to future".

[@SonicImmersion_]

The time dimension of spacetime is curved by mass. Rather than the spatial dimenions of spacetime being curved by mass. I love watching talks such as this, because of opportunities to learn something that hadn't occurred to me before. Now, I want to go learn more about time curvature.

[@rajeevgangal542]

Since both gravity and electrostatic equations are the same in form, is electromagnetic force not a force?

[@yourguard4]

Only Newtons gravity has this form. And Newton thought of gravity as a force.

[@ricocapili6990]

As the lecture points out the universe moves in an expanding direction. There is no point of reference from the outside only from the visible inside with the red shifting bodies. My theory is our universe has reached its tipping point of not reversing but bending back to its origin like a boomerang returning to the thrower in several dimensions. Heading destruction while our twin counter balance universe awaits creation.

[@ExcretumTaurum]

Since you like Deep Space Nine, the following seems apt is response to wormholes and temporal paradoxes: “I hate temporal mechanics” - Chief O’Brien to Chief O’Brien

[@ElinT13]

Very nice and informative lecture! Thanks very much!

[@0.618-0]

Cool talk Katy, very thought provoking. The stretchy fabric analogous model of gravity is misleading, gravity is like concentric rings around a sphere, with each concentric ring having a time and gravitational value, weakening the further away from the sphere. With space energy pushing on matter and matter energy pushing on space. Why are Spheres only created...what if Square massive forms were around, what would the gravity around a Square mass be. How could that even be calculated? 18:46

[@bomination.]

curved spacetime being gravity is easily disproved if you have any intuitive understanding of physics. 1. you can't curve something inside an area, you can only have a curve on a flat plain. 2. so it must be spacetime being pulled into the mass of the earth etc. 3. that means the closer you are to the mass the less dense the spacetime is, so the greater density further out is pushing you inward. 4. why does the mass pull space time toward it in the first place ? 5. where does the spacetime go ?... the mass would be FULL of spacetime after a very short time. 6. that would create an area of greater density of spacetime inside the mass that should then repel NOT ATTRACT !

[@0.618-0]

@STAFUS Interesting take on Gravity you have. Space time curvature should be called Spacetime Distortion. Gravity, I think, is a Spacetime Distortion. A distortion of density between matter on non matter. At the boundary layer, or surface of an astronomic body, Space Time , or non matter being evicted from the Volume the matter occupies when formed. it is pushed together by gravity. Mater doesn't pull on Spacetime, matter is riding the distortion field of spacetime toward the centre of the earth....

[@bomination.]

@@0.618-0 but gravity is being evoked twice. why would a mass attract spacetime at all ?

[@0.618-0]

@STAFUS Gravity evoked twice..every action has an equal and opposite reaction.second law of energy conservation. Mass has matter and spacetime in each molecule doesn't it? As you pointed out, there is greater volume of spacetime vs matter around a planet, thus gravity accelerates matter to the centre of the mass. Thus spacetime distorts , and wants to revert back to the space ather occupies. Like a mass in a tub of water. the volume of mass pushes the water. ....

[@bomination.]

@@0.618-0 "there is greater volume of spacetime vs matter around a planet, thus gravity accelerates matter to the centre of the mass" no sorry but that does not follow logic. it should repel not attract. greater density repels, it does not attract. you are simply presupposing the validity of the general theory rather than looking at it logically.

[@SiqueScarface]

I actually did not see Interstellar. Somehow I was not thrilled by the plot as announced.

[@sakismpalatsias4106]

This may be stupid question.. but are essentially saying time is de-sitter and space is flat space.. how would math work in this interaction?

[@sakismpalatsias4106]

Because the way I understand it is... Space and time are two different geometries interacting with each other in uniformity. It may be right but how would the math work ?

[@real_DrDummkopf]

@@sakismpalatsias4106 word!

[@skylark8828]

I don't think you could separate the two. There is adS space inside a black hole but spacetime is still spacetime even if the time component (axis) does get stretched the most.

[@DrDeuteron]

no, in weak fields at slow speeds, a moving mass couples to curvature through energy and momentum, but momentum is small, and the energy has big fat mc^2 in it, so the energy couples to time curvature, and....the space curvature is further suppressed by a factor "c", just to make the units work. If you do a linear approximation for small curvature, you get Newton's Law of gravity...it's kind of amazing. In spacetimes where space curvature matters, it's just too complicated to visualize.

[@hochathanfire0001]

Why does matter, mass curve space-time?

[@stellarwind1946]

The absolute worst thing in the world is when you see Ad 1 of 2 with no option to skip.

[@phenixorbitall3917]

Is there a topological reason which prohibits us to build a wormhole from scratch?

[@njdinostar]

Great talk! Thanks for sharing!

[@milkmanproductions1837]

What is the void that the universe stays in? And can we fill it or escape it? And if the universe has all these holes in it, why is it not deflating?

[@user-om7ft2ms8r]

She mixes analogies around the 19 minute mark, if the galaxies are 1 Mega Parsec and 70 meters at 1 second then rolling the clock back isn’t like “what’s further south than the South Pole?”. If at 1 second they are 1 MP + 70 then at negative 1 second they are -1 MP + 70 closer. Hopefully. I think anyone who reads this knows what I’m trying to say, wind the clock back galaxies get closer, that “space” decreases. So the whole “walking on the globe” thing is not a good way to picture what you’re saying when taking your other imagining into consideration.

[@opperhoofdgeilebizon]

Great talk, always imagined space to bent the most though. Not time. I now have to re-evalute my entire existence 😀

[@maxziebell4013]

I like the visualization in computers as a 3d grid deformed by mass

[@user-zh2hx6iu4r]

What does it mean? : the universe is mostly curved in time direction

[@Mesergschmidt]

She should've put more effort into explaining what the universe is expanding into. If you don't know say so, saying that it's like asking what's further south than the south pole is meaningless and a bit ridiculing. That is a valid question I think. The earth has limits and is round, we can always go further south than the south pole, it just won't be the south pole anymore. Does the universe also have limits ? If yes (she herself said that's a better question), what's beyond them ? What does the universe expand into ? Is it a container ? Is it wrapping in on itself as she mentioned ? Also she explained how the space-time is curved, she showed a model of space bending to prove it's correct, but then immediately proceeded to say it's actually the time and not space that's curved and gave no information for how now that is suddenly the correct view ???

[@jemhoare2105]

If space expands more quickly above me than below me do I move downwards?

[@schmetterling4477]

Relative to what? Things above or thing below you? ;-)

[@eldflaug]

Thank you so much for this great lecture

[@gorillagaming1117]

Can we inject exotic matter into regular matter to enhance our travel speed through said matter, maybe exceeding what people believe the highest achievable speed could be?

[@squad1153]

She is awesome. Love her energy and I can tell she enjoys what she does!

[@kevinashwell9384]

Hi Hi Hi Courtney Courtney hi hi hi hi hi

[@kevinashwell9384]

Hi Hi Hi Courtney Courtney 9:08 9:08 min min wait for for for for for 9:13 min min

[@kevinashwell9384]

Hi Hi Hi Hi Hi Hi Hi Hi Hi Hi Hi Hi

[@SnoopyDoofie]

Not sure why she says the universe is curved when virtually every authoritative source says it's flat.

[@extremesis]

51:30 "Dammit Tim, I'm an astrophysicist not an Engineer"

[@Robertnight888]

Although it’s a month ago for me to see ie a time difference ! From my understanding of the talk, I can only understand that the word space should be killed and realise that we live in time. Time curves, galaxies exist in time. Please, why do we need space ? Period.

[@MasterBlaster3545]

A lecturer that explains things in laymen’s terms. Give her a bigger chunk of taxpayers money (raise)

[@ashbb9165]

Negative energy is not exotic matter exotic matter is actual stuff that is not near us

[@raphaellavictoria01]

47:00 The possible answers to the time-travel paradox, what about, any changes to the past would rewrite the future in every way, except that it wouldn't affect the time traveler: his actions in the past create a tangent, which doesn't affect his past but rewrites the future and the past for everyone else. The time traveler becomes basically an isolated phenomenon, independent of HIS own past, as he knew it. Basically, he created a future where he is not born, however he continues to exist bc his universe, without being one of many universes, will not exist.

[@yanikkunitsin1466]

If he wasn't born he hasn't travelled to past in the first place.

[@addisondraper6444]

I was very impressed by this talk. It's not very often that you find someone who calls themselves a scientist who is willing to admit that they actually do know everything and couldn't possibly be wrong (like every other "scientist" who has ever lived). Smart.

[@Bobby-fj8mk]

don't you mean - do NOT know everything ?

[@robokill387]

Actually, most scientists accept that they don't know everything and that they could be wrong. That's why they got into science to begin with - there's no point in studying something that you think you already know everything about.

[@yungsookevinhong7943]

Time is a relative phenomenon related to gravity. It is a reflective or index of measurement of life condition relative consciousness.

[@MarcusMacgregor2]

Is talking about what happens if you put Mars at the Jupiter-Sun L5 point beyond the limits of astrophysics?

[@rwm1980]

Winderful presentation