the standard model of cosmology conceives of a universe which is made up of 68% Dark Energy a mysterious substance for which we know next to nothing about we've lived with this idea for decades now but new work suggest that this entire idea could be wrong that there is no Dark Energy it's all Just an Illusion created inart by subtle time dilation effects in general relativity this alternative theory is called timescapes and now a new analysis suggests that it could actually explain observations of the local Universe better than dark energy to backt track in 2011 the
Nobel Prize in physics was awarded to the discovery that the universe is not only expanding but that its expansion is accelerating the team exploited the fact that type 1A super Navy are standard candles that means they all roughly have the same intrinsic brightness so if you measure their apparent brightness that gives you their distance combine this with their red shift which is how shifted the spectral lines appear and you can get their speed now we knew since Edwin Hubble's time that more distant things are moving away from us faster that is the manifestation of the
expansion of the universe but the 2011 Nobel was awarded for noting that it's even more extreme than this the universe expansion seems to be accelerating this has led to the idea of dark energy as the underlying culprit something which we know next to nothing about but would curiously comprise the vast majority of the universe's mass energy content the standard model of cosmology includes this dark energy with a symbol called Lambda and it adds in cold Dark Matter to explain other observations too so together we call it Lambda CDM the math behind this model makes the
simplifying assumption that we can treat the largest scales of the universe as isotropic and homogeneous so in other words we can ignore all those pesky details of stars galaxies and superclusters in this picture we can almost imagine smoothing out the universe into a giant smudge of mass and energy if you do that the math is much easier and we can now solve Einstein's general relativistic field Expressions to get the so-called Freedman equations that Lambda term is dark energy but it's really just put in there by hand as Einstein first famously did so in an effort
to stop the universe from imploding now land m is incredibly successful at explaining a huge range of observation so no single experiment is going to Dethrone such a successful Theory but astronomers are always on the lookout for kinks in the armor that's our job really nothing gets us more excited than proving that an established idea might be actually wrong and this new paper appearing on the archive on the 19th of December by Antonio safer is quite the Kink they find that a gold standard catalog of type 1A Supernova known as the pantheon plus catalog actually
match predictions from the Timescape alternative Theory better than Lambda CDM Timescape is the brainchild of physicist David wilcher who challenges the Assumption of smoothing out the universe as we usually do of course we know this assumption truly must be wrong but it makes the math incredibly elegant to deal with and the resulting Theory seems to explain a very large number of observations to date we points out that the Universe does indeed start out fairly homogeneous but over time it concentrates into clusters and filaments more and more and this process leaves behind Giant voids which are
nearly empty now wilch argues that we can just throw out dark energy and get something which looks like an accelerating universe but actually it isn't to see how we're going to need two crucial ingredients first voids expand more rapidly than denser regions because they experience less gravitational pull so light which comes from such regions or even just passes through will stretch out due to this expansion and become anomalously red shifted but there's also a time dilation effect just like in the movie Interstellar clocks tick slower when you are near a lot of mass and thus
time is ticking slower for us than it is in those voids a way to think about the consequence of this is that as the light falls from a void into our gravitational well it should actually gain energy and thus blue shift so we have an extra red shift and an extra blue shift and the theory predicts when you put those together you're left with a net red shift and it is that net red shift which causes the apparent illusion that the universe is accelerating because of course it means that things look like they are moving
away from us faster than they really are Antonio safeer and colleagues decide to test this idea by comparing the predictions of the two theories against the pantheon plus Supernova catalog now this is non-trivial because as you can probably guess the math behind time Scapes is much harder despite having no Dark Energy in fact in order to make progress the team had to ignore a few bias correction terms in the theory because they just haven't been corrected yet however these should be small adjustments now if they include all of the data available they find that time
Scapes is strongly favored at the roughly three sigma level that's not overwhelming but it's impressive all the same if they eliminate some of the closer in supern there's still a preference for time Scapes but it gently drops so this is very alluring because at the end of the day dark energy has always felt like a bit of a fudge factor and a fix that no one was really that happy with but does this really mean that dark energy is done for well one of my favorite channels here on YouTube Dr Ryan ridden he's an astronomer
and a YouTuber who is actually involved in this study so please check out his video on this topic for more detail but for the sake of this video I'm just going to give you a little quote of what he thinks about this have we proven that there is no Dark Energy I wouldn't go that far at least not yet what we have shown is that Supernova data is good enough now to really test Lambda CDM and it is looking very promising for the time scape model so stay sober on this it's very intriguing but Lambda
CDM is an incredibly successful Theory which explains a lot more data than just Supernova observations the real question now is whether time Scapes can score up more successes for different sets of observations which is going to be very exciting to follow after all if Dark Energy isn't real the fate of the universe will be radically different I think sometimes the public gets the false impression that scientists Proclaim ideas and never challenge them but nothing could be further from the truth as timescapes here shows we are always challenging our own ideas seeking the next crack to
pry open and that's what makes science so powerful it self-corrects and if this is indeed a correction what a hell of a correction it would turn out to be so until next time stay thoughtful and stay curious [Music] [Music]
