Beyond Einstein: Gravitational Rainbows

Good evening everyone, tonight we have the privilege of delving into some deep and intriguing mysteries at the forefront of human understanding. Together we will travel to the cosmic landscape or the dark energy of gravity and the very structure of space intertwine and fold giving the possibility of Stunning astrophysical phenomenon as a background Our story begins with a change in our understanding of the force of gravity that took place around the first decades of the 20th century. Isaac Newton's universal law of gravity, which had remained undisputed for centuries, was radically replaced by Albert Einstein's. General theory of relativity now, although the observational differences between Einstein's and Newton's theories are minuscule in familiar settings.

Einstein's theory wasn't just a minor update of Newton's, it was a complete overhaul that revealed a new way of thinking about gravity, not as a force as we are. they were all taught in high school, but instead like the curvature of Space-Time itself, even Einstein, the revolutionary, the incomparable architect of humanity's edifice of understanding, even Einstein himself struggled to accept the full implications of his own general theory of relativity. Einstein had difficulties at least at first. with the idea of ​​an expanding Universe, although it is a direct consequence of the most basic version of his equations.

Einstein struggled again with the idea of ​​black holes, although black HSs are also a direct consequence of his equations. Einstein struggled to accept the possibility of Gravitational waves rippling in the very fabric of Space-Time and ultimately are of particular relevance to our discussion here tonight. Einstein introduced, but later abandoned, the idea of ​​a cosmological constant that is an invisible energy that permeates space, an idea that in recent decades has made a strong return to the mainstream of cosmological science. Still, although many physicists and astronomers are convinced that the universe is full of dark energy, we still largely don't know the true nature of dark energy - what exactly is dark energy made of?

What are its detailed properties? Is it really constant or does dark energy change over time? We've been asking these same questions for some time and have been coming up empty-handed; However, there have been new advances in observational astronomy and experimental physics, including the detection of

gravitational

waves. offer us new tools to investigate this mystery in the spirit of Beyond Einstein, although Einstein himself was skeptical that

gravitational

waves would ever be detected here, not only have we detected them, but we will now discuss their use to understand energy dark through a beautiful concept known as a gravitational rainbow, the idea postulates that gravitational waves, as they move through dark energy, could split into component frequencies analogous to light, forming

rainbows

as it passes through Of the residual fog after a rain, is there a pot of gold, a treasure?

A treasure trove of new knowledge to be found by chasing gravitational

rainbows

, that is a question we will discuss in this chapter of the story with our first guest Claudia Dam and let's begin with our first conversation with Claudia Donon, professor of theoretical physics at Imperial College London and A member of the American Academy of Arts and Sciences she researches gravity, particle physics, cosmology, searching for the fundamental laws of the universe. So cloudy, I thought what we'd start with, since this chapter describes the dark side, I'd like us to get to this idea of ​​dark energy. which is a vital part of our thinking about the cosmos right now and towards the end we will get to the work that you are doing, which in some ways tries to probe dark energy, almost using dark energy as a tool to get a deeper insight into the force of gravity, but to get there let's go back in time and think about gravity in the early stages of our species.

We try to understand it, which of course brings up Isaac Newton, who gave the world the first description of gravity. which does a pretty good job, it's amazing that even today we use Newton's laws to discover most of the universe, most of what is happening in the solar system, it works flawlessly, apart from a little Twix here and there , and if so, whether Newton does that. good job of describing the kinds of things we see that motivated Einstein to try to go further, so there were different developments that occurred in the late 20th century. One thing that was already clear from Newton's perspective was the force of gravity as he described it was instantaneous, meaning that as soon as something came into existence, it would affect the entire universe around it and Newton already realized that this cannot be right, it cannot just happen like this.

He knew about special relativity, he didn't know that information has to travel at most at the speed of the line, but he already knew that it didn't make sense, so it was already a theoretical preconception that said so. cannot be the definitive Theory of Everything and one way to quickly see that just because we have Newton's equation on the board is if you change one of the masses in that formula that we teach high school kids around the world, the force Attraction between them changes instantly, there is no delay in that, in that formula that is exactly right, so he already knew at that moment that he had to have something more.

Beyond Newton's theory of gravity, but no one knew exactly what and then centuries passed, really centuries. He went through where Newton's laws of gravity were, they were simply miraculous, they matched everything, including the minima of gravity in the solar system, yes, to a point where they could go ahead and predict the presence of new planets in the solar system . The system is based on simply observing the motion of the known planets and understanding how, according to Newton's theory of gravity, there needed to be other masses there to explain the motion of all the planets. Neptune Neptune was exactly like that Neptune was uh um it was just predicted before it was observed uh using Newton's laws and then the same thing happened with Mercury.

They were looking at the orbits of Mercury and just by looking at how it orbited the Sun represented all the other motions in the Sun of all the other masses in the Solar System, Jupiter, the Earth and everything else, um, they could predict that there had to be something further there to explain the movement of Mercury and in the solar system, so they predicted the existence of a new planet, Vulcan. Vulcan and observed Have you seen Vulcan in the sky? It was observed. It wasn't true and now we know that what explains the movement of Mercury to impeccable precision is not a new planet, it is something new, but it is something that is in the laws of gravity, but that raises a beautiful point right there because Sometimes an anomalous observation suggests that there is something different out there, sometimes an anomalous observation means that there is something wrong with our theory that is correct and sometimes we don't know it and sometimes it is a lot, it is something new with gravity or what is new in gravity is actually a new substance and as we will see with dark energy, sometimes the two are very aligned with each other, it is really something new in understanding the world around us, so Einstein certainly came to the conclusion that The law of gravity that Newton wrote needed an exact revision and he spent about 10 years trying to find a new description of gravity that matched all the experimental data but they didn't have this instantaneous action at a distance that was new to the problem, so It is, since 1905 since special relativity then it was clear that nothing could travel faster than light, so it was engraved in stone that gravity itself or the minima of gravity could not travel faster than the speed of light and it took him 10 years between 1905 and 1915 to really understand that not only was there a unification of space and time as is the case in special relativity, but it is even more Fundamental than that, it is not just space and time, it is space and time of matter and energy and everything, really everything you can imagine, has to be reconciled and affect the very notion of Space-Time, yes, so it is an understanding of Einstein and General Relativity in 1915 to see that gravity is a concept that can be thought of as a force and it is useful to think of it as a force in most context, but more fundamentally it can be thought of as actually the curvature of spacetime and our motion in this Cur space um C curó the space-time around us, so we now understand from Einstein's theories of relativity that if we feel the effect of the Sun, for example, in the solar system, it is because we live in a space-time and the sun curved the structure of space-time around itself. and we, as inhabitants of Space-Time, feel this curvature and the way we act in our R life is by adapting to the nature of Space-Time.

Now what we're seeing here is a familiar image, I think, to many people. those who follow science, this warping of the environment around the Sun, this is a 2D version that we all often use because it's a little bit easier to understand, but if we can show just for Giggles the 3D version, this is a little bit closer to the view that Einstein gives reason that any massive body simply by the fact of being there in space has its impact on the environment, that's right, that's right, and if we put our Force eye, we could see that in Space -4D time with a notion of time itself and with the capacity for time is really very fundamental in the minima of general relativity and one thing maybe we can see in an animation, I don't know, but now we can see it in the theory of Einstein's relativity that if you add a mass or if you remove the Sun from the solar system all of us I'm a theorist so I can do that you see our observers can do that but if you took the Sun out of the solar system for a second it would take some time. for the structure of spacetime to adapt to that and propagate that information to the planets in the solar system, which would solve the problem we have with Newton's description, so this is around the year 19, 15.

Einstein writes The final form of the field equations I think was on November 25, 1915 at the Prussian Academy of Sciences and then people slowly began to apply Einstein's new description of gravity to various things, such as the universe as a whole. together, trying to see what Einstein tells us. It's just kind of a thumbnail sketch of where we went or where scientists went in applying Einstein's ideas cosmologically, so one thing that people already knew at that time is that we are made of many galaxies and galaxy clusters and, according to Einon's theory, general relativity, anything affects space-time, even light will affect space-time, anything made of energy pressure will have an effect on the structure of space around it, so Einstein himself He realized that if there are all these things present in the universe, it's not going to make the universe stop, the universe will want to adapt to it and evolve, so if you just have a mass like the sun present at some point locally , it wraps the fabric of spacetime around itself locally, but if you think about the entire universe it's not just a localized mass here or there, it's everywhere, everywhere, there's some dust, there's some radiation, There are some galaxy clusters, so it doesn't have an effect on the universe, it is just wrapping space around itself, but it has to be something global throughout the Universe and what Einstein understood is that this and his colleagues will lead to an expansion of the universe, the universe will not stay still, it will want to evolve, the fabric of Space-Time will stretch through the effect of everything present in the universe and that led to the idea that through the existence of all matter in the universe the universe should expand uh and and we this is what was observed later, but at that time people did not think that the Universe was something that was time-dependent and evolved, so, to count on that , Einstein thought, well, maybe we have to add something, add something, not in terms of matter, because we have matter there that leads to an evolution. of the universe, but we have to compensate for that in Einstein's laws of generic relativity, but by adding a cosmological constant that would counteract the effect of everything else in the universe, which would be a kind of push outwards for that, that, that , that, that, that's it, and then I want to say just for people who want to see that there's math behind this.

I mean, if we mention Einstein's equation just for a moment, the purest and simplest version that doesn't have this quality that would help stabilize the universe, this is a beautiful equation that what Einstein writes about, but then, as you say, to stabilize the universe to prevent it from expanding, you have this other term that he adds, it is that Lambda, which is the famous cosmological constantand in history. of Science in 1929, when Edwin Hubble finally reveals that the universe is expanding, Einstein Ru, the day he introduced the cosmological constant because it was intended to produce a static Universe, slaps himself on the forehead and says that this is the biggest mistake. of my life exactly exactly and that was probably a stroke of his genius because we will see that he will come back and today we think that this coson or something very similar has to be there, well, let's do it, so this is you.

We know that back in the 1930s a lot of thought and research occurs in the intervening decades, but I want to move forward to the very modern result that occurred, you know, in the late 1990s, where the expectation was that the universe was expanding. , but it would expand more and more slowly because, after all, even in Einstein gravity is something that draws inward at least the gravity associated with ordinary things like stars and planets. What happened in 1998 with this expectation. So if the universe is expanding slower and slower, that means that as you look further and further away you look further and further into the past. and that means that in the past things expanded faster than today um and that's why there were different missions looking for Supernova star explosions that would allow us to understand how in the past the universe expanded with the expectation that it would expand. faster the further away you look because in the past it would have been faster and people were really trying to converge towards this observation in 1999, that's right, about eight or n yes, two groups realized that precisely the opposite was happening when they go and look further into the past, what you see is that the expansion of the universe was going slower compared to what it is today, which means that today the expansion of the universe is growing faster than in the past, the gravitational pool is not making the expansion of the universe slower, but faster, so the galaxies, as we see here, are simply moving apart faster and faster.

That's right, the expansion of the universe is accelerating, so something must be driving this accelerated expansion of the universe. We can call that something dark energy, we can call it whatever we want, but calling it something doesn't mean we know what it is, it's just a place for lack of knowledge due to lack of understanding of what it is. happening in the universe why and it's a version of that idea that Einstein put forward and then retracted, so what do you think dark energy is? And by you I mean the broad community of physicists, that is a good question that we know the reality.

We don't know if we can call it Lambda as a cosmic constant, it has to be something very close to a cosmic constant, so now we have very good observational evidence that it is there, there is no debate that something must be driving the acceleration. expansion of the universe and we have more and more evidence of what it is not, but it has what it is, it has to look a lot like this cosmological constant or this Lambda term that Einstein introduced into his equation, but where does that come from? that's a matter of debate, one thing we know as physicists is that there must be some energy in a vacuum and by that I mean that if you look around you, we are made of classical matter, but at the most fundamental level, made of particles that are quantum in nature, the world is quantum and therefore comes in and out of existence everywhere, not just in the solar system but throughout the structure.

Space-Time, there are some quantum fluctuations. We see it here. I guess that's correct. this is made of this has a certain energy density, it's vacuum energy and it's everywhere, not just in the habitable regions of the universe, it's really everywhere, so it's a constant, it's a constant in space and It is a constant. in time, so it is a cosmological constant, but when we calculate this with our best understanding of quantum physics, what size energy do these waves seem to generate? Yes, this is where the fun part comes in, so in principle everything works fine. we have a vacuum energy that seems like a cosmic constant that drives the acceleration of the universe that we all set up, sometimes we just need to do some calculations, so if I just do unknown physics, we know that electrons live in the universe, that's not a problem .

However, we now know that the Hix field is present. The contribution of the Hix field to the vacuum energy is 56 orders of mann or large compared to what we would need as an amount of dark energy or cosmic constant to explain the observations. expansion accelerated expansion of the universe 56 orders of magnitude too big and this is really a problem because we have too much if we didn't have enough it would be fine we would say there are more then maybe there are other more massive particles that we haven't observed yet and once we observe them they can contribute to accelerated expansion, but here we are really something too good and this is the largest discrepancy in the entire history of physics, yes, 56 orders of magnitude with known physics and if I imagine that there could be contributions beyond the particles of the standard model beyond the hg, we could reach a discrepancy of 120 orders of magnitude, this is just crazy, it is orders of magnitude, if I only consider the high contribution to the energy of the vacuum, it would make the universe accelerate so much fast that would have a size of one centimeter.

The entire universe wouldn't be able to see it beyond a center because everything else would be if you went away faster than the speed of light, you wouldn't be able to see it, that's exactly it, so you as a theorist have been investigating ways in which which at least in principle we might be able to probe dark energy, see the D, the effect. of dark energy and other things that we can measure more directly to try to get an idea. Can you give us an idea of ​​what you are doing? One of the things we'll try to do is just imagine it.

It is a rainy day and then there is a little sunlight and you see a rainbow in the sky and from the rainbow just by the fact that the light passed through water droplets in the sky you can see the division of the different colors and just by seeing the rainbow, you know that there are drops of water in the sky, now this is an album cover that is good to illustrate that point exactly now we want to do the same and it's not just pop culture, it's actually, something What we can, we can try to do with gravitational waves, dark energy, what we do know is that it is not something that we are going to interact with very easily in our daily lives.

We probably know it's there around us, but we are. No, we are not interacting directly with it and therefore to see it, if it were, we need to use gravity, we need to use the analog of Light, which is the gravitational wave, so I show it quickly, I'm sure that people are familiar with it, but. You know, we now know since 2015 that if masses move within the fabric of space, they can push it around sending out these gravitational waves and as another footnote, Einstein himself thought about gravitational waves and again it was one of the ideas to which that finally he resisted so much.

Again we have gone beyond Einstein, they have now been detected, but you propose using gravitational waves as a means of testing this dark energy, as gravitational waves propagate through spacetime they can interact with dark energy because the Dark energy is everywhere and just like Bright light through clouds leads to a rainbow. The bright gravitational waves through the dark energy through the clouds. Dark energy clouds in the universe can lead to gravitational wave rainbows, so they may be gravity rainbows. As we look at gravitational waves of different colors and different frequencies, we can see them propagating in slightly different ways and right now with ligo in 2015 and since then we observe gravitational waves at a frequency of around 100 HZ, so these are not the real colors, it's just an analogy, where is that? you're way to the right so towards red sorry it's SP towards yes it's to your right towards Violet so it's a relatively high frequency for gravitational waves but as we get more and more missions going into space and possibly even using the stars themselves as our gravitational wave detectors, we hope to go towards increasingly lower frequencies or increasingly towards the color red and how we see the evolution of gravitational waves as they pass through our space-time through our universe in different colors. we can see that there is a small change in the way they evolve, which would seem in some sense a gravitational rainbow, the analogue of a rainbow before gravitational waves and that is why it is so important to be able, for example, with the Observatory Simon observe gravitational forms of frequency as low as the color red, if you like, the frequency of those gravitational waves is the wavelength of those gravitational waves, they are all almost as big as the entire observable universe, they are as big as they can be and simply testing how different colors of the gravitational shape evolve differently.

We may have an idea of ​​how gravity behaves and how it interacts with dark energy as they propagate through the universe. Beautiful idea. We only have a couple of minutes. I just want to finish with another idea you've had. I've been chasing, which again extends Einstein because you've been investigating the possibility that, as much as light has, people have certainly heard, you know, two independent polarizations, you know it can oscillate one way or another, Gravitational waves also have a similar quality to traditional gravitational waves. Einstein standard and description, but you've been studying the possibility of maybe other versions that extend Einstein's different polarizations.

There may be more than two, it just gives an idea of ​​that ex exactly, so this is an image of how the two polarizations of light are illuminated and we have a very good purpose with that and there is a direct analogy for gravitational waves that we can see . I don't know if there's another slide, yeah, if you can show that other video please, yeah, great, so on your left they are. the polarization of gravitational waves that have been observed with ligo for gravitational forms, but in principle there could be more, there could be more flavor of gravitational waves, some that we have not observed and they may be quite shy, but they may be present. and so, as we investigate our understanding of gravitational waves and try to probe them in different ways using different instruments or different realizations, we can see that there could be more to gravity or more to gravity and that in some sense there could be more to the gravity. either the effect of dark energy on gravity or it could be the way that gravity mimics dark energy and sometimes the two are a kind of mat, they are embedded in the same concepts, which is why both the experiment and theory perhaps blend together in a powerful way.

It's exactly fascinating work, so unfortunately our time is up and it's limited, but please join me in thanking Claudia D. Thank you very much. Thank you so much. I can't help but think that if Einstein were in the audience of this conversation, he would now be smiling with two ideas. arising directly from his own general theory of relativity, the AAL cosmo or dark energy, as well as ripples in the fabric of space, gravitational waves, none of which, let's say, he leaned towards in his own life, now They are at the forefront of our understanding of reality and, as we have just heard, they may well come together in the astonishing idea of ​​gravitational rainbows, in which dark energy acts as a kind of prism that divides gravitational waves in their component frequencies, the analogue of the colors of light or pure tones for sound that would in fact be something that would make Einstein proud.

The next conversation in this Beyond Einstein series will address another implication of general relativity that Einstein resisted the idea of ​​black holes, a possibility that over the years has gone beyond improbable. from possible to probable and now with recent observations to absolutely certain abs we'll talk to some of the scientists responsible for that final shift towards certainty we'll explore what's on the horizon for black hole research join me for part two of the series my conversation with eron Cara and Shep Dolan