This deep Hubble Area Telescope picture exhibits among the earliest galaxies recognized within the universe. The James Webb Area Telescope has peered even farther again in time. Credit score: ESA/NASA
In July, cosmologist Rajendra Gupta on the College of Ottawa revealed a splashy paper in Monthly Notices of the Royal Astronomical Society claiming that our universe is more than 10 billion years older than we have now lengthy believed it’s. Let’s dig into this stunning declare that, if true, would shake the foundations of contemporary cosmology, and see if it holds as much as scrutiny.
Spoiler alert: it doesn’t.
The setup
The central focus of Gupta’s work is the superb outcomes popping out of the James Webb Area Telescope (JWST), which has revealed that the early universe is stuffed to the brim with massive galaxies. These galaxies are far bigger than we thought they’d be based mostly on our present mannequin of the evolution of the universe, often called ΛCDM (the place Λ is the uppercase Greek letter lambda; pronounced “Lambda-CDM”). The ΛCDM mannequin is about as easy a mannequin as may be that makes an attempt to suit all accessible proof. It says that our universe is essentially manufactured from darkish vitality (that’s the “Λ” half), a superb chunk of cold dark matter (that’s the “CDM”), and a smattering of regular matter and radiation (which doesn’t get to be part of the identify). The mannequin additionally states that the universe has been increasing from a scorching Huge Bang, and that enlargement causes the sunshine from distant galaxies to redshift on its manner towards us.
Like all concepts in science, it has its shortcomings and holds its fair proportion of mysteries. We don’t perceive the character of dark matter or of darkish vitality, and within the newest case, the ΛCDM mannequin predicts that early galaxies must be small.
New cosmology?
One very actual chance is that we’re getting this all incorrect and that the ΛCDM mannequin is damaged. That is the tack that Gupta took, and he launched a hybrid mannequin that invokes a number of concepts which were floating round in cosmological circles for nearly a century to clarify the younger, massive galaxies. In Gupta’s mannequin, the universe is greater than 10 billion years older than the ΛCDM mannequin would recommend, which supplies galaxies loads of time to develop to their spectacular sizes. In different phrases, the “early” universe isn’t so early. Downside solved.
However cosmology is a mature science and plenty of, many observations exist that every one relate to one another. You’ll be able to’t simply clarify one statement, just like the sizes of distant galaxies, and name it a day. It’s a must to face a gauntlet of different observations if you’d like your mannequin to succeed. Gupta acknowledges this and likewise asserts that his mannequin agrees with, for instance, the isotropy of the cosmic microwave background (CMB; i.e., why it’s so uniform all through the sky) and the info from supernova surveys.
However to make all of those observations work, Gupta’s mannequin is way extra advanced than ΛCDM. In Gupta’s mannequin, there may be the conventional enlargement of the universe. Moreover, he invokes an thought known as “drained gentle,” first proposed by astronomers on the daybreak of contemporary cosmology, round 1930. This concept challenges the interpretation that the universe is increasing, as an alternative stating that gentle merely loses vitality because it travels. Plus, Gupta invokes one other century-old concept that the bodily constants of the universe, just like the pace of sunshine and the energy of gravity, change with time.
Unsurprisingly, if you make fashions extra advanced and extra concerned, you’ll be able to typically clarify any statement you need. However this comes at a value.
Hitting snags
Gupta’s mannequin introduces an infinite quantity of further complexity and new physics to the universe, all to clarify the massive measurement of distant galaxies whereas additionally satisfying the aforementioned nature of the CMB and the supernovae we see. Nonetheless, many extra observations exist which have but to be addressed by this new mannequin. For instance, we have now the abundance of sunshine components cast within the early Huge Bang. We’ve got the expansion and growth of clusters, filaments, and voids within the cosmic net. We’ve got not simply the isotropy of the CMB, however the tiny fluctuations in temperature that do exist inside that background. And extra.
The ΛCDM mannequin can clarify all these observations, whereas Gupta’s mannequin doesn’t. As well as, Gupta’s mannequin introduces all types of latest physics that at present go unexplained. How precisely does gentle lose vitality because it travels? What’s the mechanism behind the variations within the bodily constants? These processes demand clarification. Certainly, physicists have examined comparable fashions for many years and located them unable to deal with the wealth of information popping out of particle physics experiments across the globe.
Even when we have been to take Gupta’s mannequin severely and put apart the problems with its foundational physics, the mannequin isn’t as hardy because it seems. Sure, it explains the measurement of distant galaxies, however not their age. The JWST observations do reveal galaxies which are bigger than we anticipated them to be, however paradoxically additionally they seem younger and vivid. Regardless of their measurement, they appear to be galaxies which are just a few hundred million years outdated, not 5 billion or 10 billion years outdated, like fashionable galaxies. Additionally, if Gupta’s mannequin is correct, we should always see stars in all places which are 15 billion to twenty billion years outdated. We don’t.
Gupta’s mannequin is fascinating as a thought experiment to discover what physics we would want to clarify these and maybe future JWST observations. However as a completely functioning cosmological mannequin, it falls far quick, and creates extra mysteries than it solves. It’s true that we have to replace our understanding of the universe, however this new mannequin isn’t the way in which.
