Astronomically Rare ‘Double Lens’ Yields Best Single System Measurement Of Cosmic Expansion
“Methods based on early signals imprinted in the cosmic microwave background and on the Universe’s large-scale structure indicate one value: 67 km/s/Mpc. However, methods relying on precise measurements to distant objects deliver a conflicting value: 74 km/s/Mpc. With overall errors of just 1-2% apiece, this 9% difference is significant and robust. Each new measurement has the opportunity to either validate or refute this growing tension.”
How quickly is the Universe expanding? You might think that’s a simple question, and it would be if every way we had of measuring that rate gave the same consistent answer. Only, what we’re finding is something very strange: measuring the expansion rate using an early-time signal gives one value, and measuring it using a late-time signal gives a different, inconsistent value.
The next step is to come up with as many different methods as possible of measuring this rate, and to see if the discrepancy persists. In a novel 2017 find, the system DES J0408-5354 was discovered, appearing to be a background objects lensed four times by a foreground galaxy. As it turns out, though, this is actually a double lens: two independent background sources lensed by the same foreground source, with each one creating multiple images.
This is an unprecedented system for measuring the expansion rate, and yields a value with just 3.9% uncertainty. Which group did it agree with? Come find out as the mystery deepens today!
Was Dark Matter Really Created Before The Big Bang?
“So if that’s what the observational data points towards, what can we say about where dark matter comes from? A recent headline that made quite a splash claimed that dark matter may have originated before the Big Bang, and many people were confused by this assertion.
It might seem counterintuitive, because the way most people conceive of the Big Bang is as a singular point of infinite density. If you say the Universe is expanding and cooling today, then you can extrapolate it back to a state where all the matter and energy was compressed into a single point in space: a singularity. This corresponds to an initial start time for our Universe — the beginning of our Universe — and that’s the Big Bang.
So how could something that exists in our Universe, like dark matter, have originated before the Big Bang? Because the Big Bang wasn’t actually the beginning of space and time.”
Last month, a paper came out claiming that dark matter may have been created before the Big Bang. Although it might sound implausible, it’s absolutely a possibility that we cannot rule out, although it might be an idea that’s extraordinarily difficult to test when we compare it up against the other options. We have to keep every scenario that hasn’t been ruled out in mind, and understand that despite all we don’t know about dark matter, there’s a ton of indirect evidence brought to us by the full suite of observations at our disposal.
Could dark matter have been created before the Big Bang? Yes, but three other possibilities are maybe even more viable. Come find out why today.
What Was It Like When Life In The Universe First Became Possible?
“We still don’t know how life in the Universe got its start, or whether life as we know it is common, rare, or a once-in-a-Universe proposition. But we can be certain that life came about in our cosmos at least once, and that it was built out of the heavy elements made from previous generations of stars. If we look at how stars theoretically form in young star clusters and early galaxies, we could reach that abundance threshold after several hundred million years; all that remains is putting those atoms together in a favorable-to-life arrangement. If we form the molecules necessary for life and put them in an environment conducive to life arising from non-life, suddenly the emergence of biology could have come when the Universe was just a few percent of its current age. The earliest life in the Universe, we must conclude, could have been possible before it was even a billion years old.”
When the Universe was first born, life was absolutely impossible. There were no planets for life to reside on; there were no organic molecules to self-replicate; there were no energy gradients or sources of heat and light; there weren’t even heavy elements or neutral atoms. In order for life to exist, the Universe had quite a bit of work to do.
Our Earth formed after more than 9 billion years of cosmic evolution, and life began on our planet shortly after that. But there’s no reason to believe that Earth is the only world with life on it; in fact, if we put everything we know about the Universe together, many other locations should have gotten there billions of years earlier.
Here’s the cosmic story of when life could have first arisen in the Universe, and it comes not only before us, but before most people have ever dared imagine.
One Universe Is Not Enough
“If you accept that inflation is a stage that occurred in the Universe’s past prior to the hot Big Bang, and that the Universe itself is inherently quantum in nature, the existence of a multiverse is unavoidable. Even though we cannot observe these other Universes, we can observe a huge amount of evidence for inflation, indirectly pointing to its inevitability. We can also observe a huge amount of evidence that the Universe itself is quantum, even though we have no proof that inflation itself behaves as a quantum field. If you put these pieces together, it unambiguously leads to the prediction that our Universe should be only one of countlessly many Universes, all embedded in an eternally inflating, expanding background. One Universe is not enough. Even though we cannot detect it, the prediction of a multiverse is unavoidable.”
When Carl Sagan’s Cosmos began, the first words you heard were, “The cosmos is all there is, or was, or will be.” Only… what if it weren’t? What if what we know as our cosmos, i.e., the entire Universe, were only one of countlessly many, all embedded in a strange spacetime that was continuously creating more of them? This sounds like some sort of strange speculation, but it’s actually an unavoidable consequence of two of our best theories put together: cosmic inflation and quantum physics. Combine them, and you get a multiverse.
This doesn’t mean the multiverse is the answer to all our problems; far from it. But it does mean that one Universe is not enough. Come find out why!
Inflation Isn’t Just Science, It’s The Origin Of Our Universe
“3.) There should be fluctuations on scales larger than light could have traveled since the Big Bang. This is another consequence of inflation, but there’s no way to get a coherent set of fluctuations on large scales like this without something stretching them across cosmic distances. The fact that we see these fluctuations in the cosmic microwave background and in the large-scale structure of the Universe — and didn’t know about them until the COBE satellite in the 1990s — further validates inflation.”
Beginning in 1979, a new idea arose in theoretical physics, seeking to improve upon the idea of the Big Bang: cosmic inflation. Recently, a number of physicists, including one of inflation’s cofounders, Paul Steinhardt, have come out with vitriol against the theory of inflation, calling it not even science. It’s true that inflation may not be the final answer to absolutely everything in the Universe, as there are a number of indeterminate predictions and a number of puzzles it fails to adequately solve. But that does not mean it isn’t science! In fact, inflation is the best theory we have to explain the initial conditions that the Big Bang has been observed to begin with. In addition, inflationary cosmology makes a number of powerful predictions that give rise to observables within our Universe, and a great many of them have been subsequently tested and validated. For reproducing the successes of the pre-existing theory, for explaining phenomena the old theory could not, and making new, testable, successful predictions, inflation hits all the points a scientific theory could aspire to.
It isn’t just a theory; it’s the best descriptive theory of the early Universe we’ve ever come up with. And in pushing the needle forward, it’s a shining example of the best kind of science of all.
Is The Inflationary Universe A Scientific Theory? Not Anymore
“The scientific approach to the situation would be to choose a model, determine the parameters that best fit observations, and then revise the model as necessary – i.e., as new data comes in. But that’s not what cosmologists presently do. Instead, they have produced so many variants of models that they can now “predict” pretty much anything that might be measured in the foreseeable future.
It is this abundance of useless models that gives rise to the criticism that inflation is not a scientific theory. And on that account, the criticism is justified. It’s not good scientific practice. It is a practice that, to say it bluntly, has become commonplace because it results in papers, not because it advances science.”
The inflationary Universe is one of the most revolutionary new ways of looking at the cosmos to come out of the last 40 years of science. Instead of going all the way back to a singularity from which time, space, matter, and energy all emerged, cosmic inflation posits a different state that gave rise to our hot, dense, matter-and-radiation-filled Universe. With energy inherent to space itself, brought about via coupling to a new field known as the inflaton, this exponentially expanding epoch preceded what we presently know as the observable Universe. Inflation has its attractive features, and can explain many features that are observed to be true. In addition, it has made successful predictions that were borne out, years or even decades later, by detailed observations of the Big Bang’s leftover glow. But there’s a darker side to inflation: the phenomenon of “infinite model-building,” where theorists churn out model after model after model, predicting every imaginable outcome, and therefore, predicting nothing at all.
Although inflation has some incredible features that no other competitor can match, it’s not a theory without its flaws. Sabine Hossenfelder gives us a peek behind the curtain on Starts With A Bang today.
The Greatest Cosmic Puzzle: Astronomers Find Stars That Appear Older Than The Universe
“Now, it’s always possible that there’s something fishy that happened in the star’s past that we can’t know about today. It’s possible that it was born as a higher-mass star and something stripped the outer layers off, reducing the star’s lifetime precipitously. It’s possible that the star absorbed some material later-in-life that changed its heavy element content, skewing our perceptions today. Or it’s possible that we’ve got a misunderstanding in the subgiant phase of the stellar evolution of these old, low-metallicity stars. These unknowns (and in some cases, unknowables) are possible sources of errors when we try and compute the ages of the oldest stars.
But if we’ve got these ages right, there might potentially be a problem. You can’t have a star that exists in our Universe that’s older than the Universe itself. Either something’s wrong with our estimates for the ages of some of these stars, something’s wrong with our estimates for the age of the Universe, or something else, that we’re not even considering, is off.”
Age may be just a number, but in cosmic terms, there are some rules it’s pretty important to obey. It should be impossible to have a complex creature that’s older than the planets; a rocky planet that predates the stars; or a star that’s older than the Universe itself. With a figure of 13.8 billion years, we’ve arrived at an incredibly accurate estimate for the age of the Universe since the Big Bang from a slew of different sources, and so nothing should be older than that. When we survey the stars in the Milky Way, however, we find not only many that are older than 12 billion years, but a few that may predate the galaxy itself, hailing from just 300 million years after the Big Bang. In one alarming find, though, there’s a particular star, HD 140283, that appears to be 14.5 billion years old. A star older than the Universe itself is impossible, of course, but there’s got to be a reason for this discrepancy.
Is the age of the star wrong? Our estimate for the age of the Universe? Or is something else afoot? Regardless, there’s more to learn, and a compelling cosmic puzzle to investigate here.
How Does Earth Move Through Space? Now We Know, On Every Scale
“Ask a scientist for our cosmic address, and you’ll get quite a mouthful. Here we are, on planet Earth, which spins on its axis and revolves around the Sun, which orbits in an ellipse around the center of the Milky Way, which is being pulled towards Andromeda within our local group, which is being pushed around inside our cosmic supercluster, Laniakea, by galactic groups, clusters, and cosmic voids, which itself lies in the KBC void amidst the large-scale structure of the Universe. After decades of research, science has finally put together the complete picture, and can quantify exactly how fast we’re moving through space, on every scale.”
It’s hard to believe, but despite being at rest here on the surface of Earth, we’re actually hurtling through the Universe in a variety of impressive ways. The Earth spins on its axis, giving someone at the equator a speed of some 1700 km/hr. Yet at even faster speeds, the Earth orbits the Sun, the Sun moves through the Milky Way, and there’s a great cosmic motion that applied to the Milky Way galaxy beyond even that. For a long time, we’ve been able to measure the total effect of all these motions, summed up, by measuring our motion relative to the cosmic microwave background: the leftover glow from the Big Bang. But it’s only very, very recently that we’ve identified the source of all the gravitational causes of this motion. While we’ve known of stars, galaxies, and the large-scale structure of where matter is, it’s new that we’ve quantified the effects of these great cosmic voids.
By combining everything together, we can finally explain the grand total of all of our cosmic motion through the Universe. Come get the full, complete story at last!