First Evidence Black Holes Source of Dark Energy - EXPLAINED

last week a team of physicists may have finally found the answer to one of the biggest problems in cosmology a solution for the origin of dark energy an invisible force that shapes the evolution of our universe and that it may be tied to the existence of the black holes that populate the centers of galaxies this may explain the nature of why our universe is expanding and why that expansion is accelerating a problem that's been perplexing cosmologists and theoretical physicists for more than a hundred years today we're looking to understand are black holes driving the expansion of the universe to understand where we're going let's take a look at how we got here and visit the history of black holes dark energy and the universe foreign in the early 1900s when Einstein first started coining ideas around general relativity his aim was to describe a universe that was static and constant as this was the generally accepted assumption at the time that meant that for the force of gravity that draws everything back together he included a counter term with a placeholder name of the cosmological constant to apply a positive expansive Force to the universe to explain why we hadn't seen everything contract and collapse back into a single point due to that strong force of gravity this mechanism of making a perfectly balanced universe is an example of something called fine tuning and it was later realized that Einstein's static Universe would be very difficult to be a stable solution any local inconsistency or inhomogeneity in the distribution of gravity or mass or any change in this repulsive force would ultimately lead to either runaway expansion or runaway contraction of the universe there's an example of when equilibrium is actually unstable in 1929 Edwin Hubble provided the first observational evidence that the universe may not actually be stable but instead be expanding using the largest telescope of the time Hubble noticed that light from far away galaxies appears to be stretched to longer wavelength in a phenomena called redshift implying that the more distant a galaxy is from us the faster it must be receding into space that the universe is expanding uniformly in all directions this feels in a practical sense a lot like a balloon expanding and all the points across it becoming further away from each other with further points increasing in distance at a faster rate than closer points but it's worth asking what's actually happening here if it's everything in the universe that's expanding then your ruler would be expanding also then you wouldn't actually notice the difference between these points increasing in distance we have however noticed the expansion so objects must be somehow separated from this expanding phenomena the very fabric of space-time instead must be expanding how strange at this point in time even though Hubble had provided us evidence that the Universe was expanding it still wasn't completely clear whether that expansion was slowly being reduced by the mass in the universe as gravity provides some contractive force or whether that expansion was accelerating and running out of control while the universe is everything and if it's expanding someday it will break apart and that will be the end of everything foreign Supernova search team published observations of a type 1A Supernova with the goal of determining which of these scenarios was happening the idea was that as type 1A Supernova have very well defined brightness so-called standard candles the only way that brightness should vary when we look at them is as a function of their distance from the person observing them by comparing this distance to a supernova's cosmological redshift we noticed that the Supernova are about 10 to 15 percent further away than expected if we were to measure them solely by their redshift the findings from these observations suggested that the Universe had expanded more in the later half of its life than in the first half that the expansion of the universe was accelerating now this was a really strange result because the only Force we were really aware of that acted on cosmological scales was that of gravity and we expected the pull of gravity between all objects in the universe should be slowing expansion down to account for the observation that the Universe was not only expanding but accelerating in its expansion scientists proposed a term called dark energy that was responsible for pushing things apart more strongly than gravity could contract them now this if you remember sounds a lot like that initial term Einstein had proposed of the cosmological constant the real problem was we didn't really have a good candidate for why this expansion was actually happening hence its somewhat opaque name of dark energy or in more colloquial circles bad Universe Juju and the thing is this isn't a minor correction factor as of 2013 the best current measurements indicate that dark energy contributes about 68 of the total energy in the present-day universe so there's something out there that outnumbers everything else we understand and know about in a ratio of two to one one of our most reasonable guesses for sources of this dark energy was something fundamentally part of space-time itself that we referred to as vacuum energy in quantum mechanics space is never truly completely empty this is because there's always a background of bubbling and churning virtual particles popping into and out of existence any given virtual particle or particle pair will only exist as long as Allowed by the uncertainty principle still any small volume of space has many pairs coming and going in and out of existence all the time as a result if we measure the energy contained in that volume we will not measure the classical value of zero instead we will measure a small but finite energy content even in empty space this vacuum energy could contribute to the mass energy of space and it provides a possible physical reason for the cosmological constant there was however one big problem with this Theory black holes they're extremely strong gravity is hard to oppose even for a universe filled with possible virtual particles applying some expansive pressure so how do we deal with the big black hole in the room foreign from the core of a massive Star as the star runs out of fuel causing it to collapse this sets off a shock wave blowing up outer layers of the star causing a supernova as the core collapses under the force of gravity its density increases at some point if the available mass is enough in that core of the star approximately three times greater than the mass of our sun then that mass will become compressed into such a small point and distort the fabric of space-time around it so heavily that not even objects moving at the speed of light can escape the gravitational well giving black holes their characteristic Blackness as not even light can escape them as you can imagine the difficulty in detecting black holes that give off no light and give off no signal can be a particular challenge the primary way that we go about studying them is when they start to consume other stars passing too close by to the black hole they draw the star towards them forming something called an accretion disk that shines brightly as the material from the star is superheated by friction before being swallowed into the black hole these objects are called quasars and they are some of the brightest objects in the universe and allow us to spot black holes in the night sky this accretion process we thought was the only real way for black holes to gain Mass however if you look at populations of black holes in old dead galaxies where there is no more material for them to consume over billions of years they continue relentlessly to increase in Mass this was the discovery in the first of two papers published by Duncan Farah from the University of Hawaii and his collaborators around the world they show that the mass gained by black holes over billions of years can't easily be explained by any standard Galaxy or black hole process that we're aware of so what is actually happening the research team looked at a particular type of galaxy called a giant elliptical galaxy which evolved early in the lifetime of the universe and then became dormant dormant Galaxies have finished forming Stars leaving little material for black holes at their Center to consume in order to increase in Mass meaning any further growth can't be explained by normal accretion of mass processes it's worth introducing here how do we actually look further back in time in the history of our universe you can do this by looking at more distant stars because their light is only just started to reach us you can imagine the recording of a star or Galaxy's life to essentially be sprawled out Across the Universe with its birth at the most distant point and its present at the star or Galaxy's surface now in comparing observations of very distant galaxies which were young with local elliptical galaxies which are old and Undead showed growth much larger than predicted by accretion or mergers alone over 9 billion years the black holes increased between 7 and 20 times their initial Mass even though there was no mass in those Galaxies for the black holes to consume the team set out to understand if this Mass increase could somehow be connected to the increased rate of expansion of the universe over this time period to do this they Define something called a coupling constant that is a measure of the relation of the black hole Mass increase relative to the rate of expansion of the universe for a traditional Singularity containing black hole the coupling strength would be zero as there would be no relation between the universe's expansion and the black hole's Mass increase however if the black hole mass is coupled to the universe expanding we would expect to see a coupling strength of three the team examined five different black hole populations in three different collections of elliptical galaxies in each of the comparisons they measured the coupling constant to be around 3.11 ruling out the possibility of zero coupling to 99.98 confidence the killer question obviously is why foreign if the universe was expanding because something was applying an expansive force on it at each increment of expansion the density of that Force should be decreasing ultimately allowing the expansion to slow down as the researchers found that the black hole mass is increasing proportionally to the universe's expansion the research team hypothesized that this is essentially keeping the density of that Force constant Across the Universe keeping the universe's expansion accelerating that black holes are in effect the source of dark energy the researchers present a calculation that if this was the case what fraction of the total energy of the universe would black holes contribute and they find an answer of about 68 exactly are estimates for the energy composition of dark energy now what is actually happening here I think isn't as clearly presented but the paper only just came out so I think there's still some thinking left to do here the speculation is that black holes are somehow breaking down the matter they consumed and are converting it into the energy of space-time driving expansion of the universe now although I am a physicist this isn't my field so I'm very happy to be corrected on any of this in the sophisticated scene that is the physics chat rooms around the internet I've seen murmurings of speculations about some proposed mechanisms but at the moment it's all just speculation the most vocal Contender that I've seen a lot of conversation around is something called Hawking radiation the idea that those vacuum energy particles that pop into and out of existence that they could do so on either side of the Event Horizon of a black hole so one particle could fall into the black hole and one could Escape out into the universe it feels maybe a bit related but there are a number of holes with this idea no pun intended that I can't really make up my mind if I actually agree with it just yet regardless though this result is special it's the first observational evidence that black holes contain vacuum energy and that they are coupled to the expansion of the universe increasing in mass as the Universe expands if further observations confirm it cosmological coupling will redefine our understanding of what a black hole is but what does it actually mean for the rest of our universe [Music] this is one of the first if not the first proposed sources of dark energy where no new phenomena needs to be added into our understanding of how the universe behaves in order to build an accurate model of the universe it appears with very high levels of confidence that black holes in Einstein's theory of gravity are dark energy but what does that mean for the eventual fate of the universe well in a universe that continues to expand faster and faster most galaxies will eventually cross a type of cosmological event horizon where any light or information they emit past that point will never be able to reach us at any time in any infinite future the distance between us and these stars and galaxies will be uncrossable even given infinite time traveling at the maximum speed of the universe the speed of light now this might feel like a cold and Bleak future where slowly the lights of the universe start going out around us in the grand scheme of things I think it's easy to feel small in an expanding universe but distance can often make the heart grow fonder and remind us to appreciate what we have and to hold on to the things that matter most that we are part of something big something beautiful and something that's expanding and evolving every day if you like this video do please consider subscribing and leaving a like if you are interested in other Universe phenomena you might be interested in the video I Shot recently on is the universe actually real thanks very much for watching I'll see you next time goodbye [Music]

Channel: Dr Ben Miles

Views: 119,760

Keywords: science, startup, spinout, research, how to run a business, business, innovation, future, investment, deep tech, deep science, future technology

Id: hsb7g9_aS34

Length: 15min 39sec (939 seconds)

Published: Sun Feb 19 2023