As other posters have noted, this is not a case of overturning the ‘big bang’ in the sense that there was a time about 13 gigayears in the past when the universe was dense and hot and it has expanded since. Inflation (its veracity and the details thereof if it did indeed happen) and early galaxy formation are active areas of research.
Another is an asymmetry in the average temperatures on opposite hemispheres of the sky. This runs counter to the prediction made by the standard model that the Universe should be broadly similar in any direction we look.
I remember when that was discovered! It is very interesting. That and the ‘dark flow’, an apparent bias in the movement of galaxies across the visible universe. I have wondered if this apparent inhomogeneity in the early universe reduces the need for inflationary cosmology in the first place to explain what is observed? It was posited in the first place to explain extreme sameness in all directions of the CMB. That it runs counter to certain cosmological nuances does not go against the evidence that the universe is expanding and used to be dense and hot.
We are also getting a better look at galaxies at greater distances, thinking they would all be young galaxies, and finding they are not
They aren’t noting their age, they are noting their star-forming status. And finding that many finished star formation much earlier than previous models suggested, suggesting models of galaxy and star formation are wrong. It should be noted that it does not take long after star formation stops for galaxies to lose their ‘young’ gleam—star brightness increases with the 3.5th power of mass and so star lifetime decreases with the 2.5th power of mass. A star 4x as massive as the sun will be 128x as bright and only live for a bit over 300 megayears. The thin scum of the largest stars (up to 100 solar masses) dominates the light produced by any given galaxy and goes away quite fast after star formation ceases, cosmologically speaking.
It should also be noted that there IS a very distinct arrow-of-time in star formation rates that points at the early universe being very different than the late universe:
ARXIV, PDFPopular press
To quote myself from a previous post I made:
To make a long story short, a survery was made looking into deep space, and back in time up to 11 billion years, of a pretty good proxy of star formation (the emission lines produced by emission nebulae that are lit up like neon lights by the ultraviolet light of freshly-born huge stars). After doing some fancy math to correct for the expansion of space and the like the conclusions are striking—the modern average rate of star formation in the universe is less than 1⁄30 the peak rate of 11 billion years ago, and half of the stars in the universe are over 9 billion years old. To make matters even more interesting, the empirically-derived relationship between time and star formation actually converges to a finite number of stars when you project it into the future, and at infinity reaches a total number of stars born only 5% more than currently exist today.
95% of stars that will ever exist already exist.
This is a very strong tendency through time for star formation rates to be high early and tail off. (NOTE: if space weren’t expanding, that star formation rate difference would be even higher than the above figure given the observations made.) Combined with the fact that there don’t seem to be any stars older than the age of the cosmic microwave background radiation… yeah, something big happened 13 gigayears ago.
To my mind the cosmic microwave background radiation, the observation of the slow reionization of the universe from neutral hydrogen to hydrogen plasma over the course of hundreds of megayears after the first quasars, and the fact that if you fit models of space expansion and run them back to t=0 and calculate the densities and temperatures thereof and simulate nuclear reactions of the first few minutes after t=0 you can get out the primordial hydrogen and helium and isotope ratios that are observed (lithium 7 showing difficulties with the models with several possible implications which are being explored, including possibly relaxing the assumption of homogeneity) are the best pieces of evidence that about 13 gigayears ago there was a major event where a dense hot universe began expanding into a cool empty one. That and the redshift. Basically, something banged, and theyre still trying to figure out what did and why, and lots of details of the early universe are still being worked out. As is the apparent fact that the expansion is accelerating, and the fact that the best model so far for predicting the motions and spins of galaxies requires nonbaryonic mass.
Additionally, to my mind, any speculation as to if the big bang was truly the ‘beginning of time’, or one among many, or symmetrical about t=0, or all manner of other things is premature as there is insufficient data as to the nature of the event in the first place. The fact that an event happened seems clear though.
As other posters have noted, this is not a case of overturning the ‘big bang’ in the sense that there was a time about 13 gigayears in the past when the universe was dense and hot and it has expanded since. Inflation (its veracity and the details thereof if it did indeed happen) and early galaxy formation are active areas of research.
I remember when that was discovered! It is very interesting. That and the ‘dark flow’, an apparent bias in the movement of galaxies across the visible universe. I have wondered if this apparent inhomogeneity in the early universe reduces the need for inflationary cosmology in the first place to explain what is observed? It was posited in the first place to explain extreme sameness in all directions of the CMB. That it runs counter to certain cosmological nuances does not go against the evidence that the universe is expanding and used to be dense and hot.
They aren’t noting their age, they are noting their star-forming status. And finding that many finished star formation much earlier than previous models suggested, suggesting models of galaxy and star formation are wrong. It should be noted that it does not take long after star formation stops for galaxies to lose their ‘young’ gleam—star brightness increases with the 3.5th power of mass and so star lifetime decreases with the 2.5th power of mass. A star 4x as massive as the sun will be 128x as bright and only live for a bit over 300 megayears. The thin scum of the largest stars (up to 100 solar masses) dominates the light produced by any given galaxy and goes away quite fast after star formation ceases, cosmologically speaking.
It should also be noted that there IS a very distinct arrow-of-time in star formation rates that points at the early universe being very different than the late universe: ARXIV, PDF Popular press
To quote myself from a previous post I made:
This is a very strong tendency through time for star formation rates to be high early and tail off. (NOTE: if space weren’t expanding, that star formation rate difference would be even higher than the above figure given the observations made.) Combined with the fact that there don’t seem to be any stars older than the age of the cosmic microwave background radiation… yeah, something big happened 13 gigayears ago.
To my mind the cosmic microwave background radiation, the observation of the slow reionization of the universe from neutral hydrogen to hydrogen plasma over the course of hundreds of megayears after the first quasars, and the fact that if you fit models of space expansion and run them back to t=0 and calculate the densities and temperatures thereof and simulate nuclear reactions of the first few minutes after t=0 you can get out the primordial hydrogen and helium and isotope ratios that are observed (lithium 7 showing difficulties with the models with several possible implications which are being explored, including possibly relaxing the assumption of homogeneity) are the best pieces of evidence that about 13 gigayears ago there was a major event where a dense hot universe began expanding into a cool empty one. That and the redshift. Basically, something banged, and theyre still trying to figure out what did and why, and lots of details of the early universe are still being worked out. As is the apparent fact that the expansion is accelerating, and the fact that the best model so far for predicting the motions and spins of galaxies requires nonbaryonic mass.
Additionally, to my mind, any speculation as to if the big bang was truly the ‘beginning of time’, or one among many, or symmetrical about t=0, or all manner of other things is premature as there is insufficient data as to the nature of the event in the first place. The fact that an event happened seems clear though.