Science @kbin.social ourlifeintoronto @kbin.social 1 yr. ago

New research puts age of universe at 26.7 billion years, nearly twice as old as previously believed

phys.org New research puts age of universe at 26.7 billion years, nearly twice as old as previously believed

Our universe could be twice as old as current estimates, according to a new study that challenges the dominant cosmological model and sheds new light on the so-called "impossible early galaxy problem."

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@ourlifeintoronto The article touches on implications for dark energy. Anybody knowledgable in the area able to say a bit more about that?
- What are you interested in specifically? Dark energy is a huge topic :)
  
  @fearout @ourlifeintoronto Specifically, is this a way to remove the need for it in our models or not?
  
  Nope.
  
  Dark energy is basically what we call a force that drives the ever-accelerating expansion of the universe. Something is pushing spacetime itself to expand in all directions simultaneously, and that something isn’t accounted for by any other fields or forces.
  
  There is a cosmological constant associated with dark energy, Λ (lambda). It represents energy density of dark energy across our universe. This is why the article (and the paper itself) mentions ΛCDM model — that’s the simplest dark energy model, where vacuum has constant energy throughout the universe and that’s what drives the expansion. There’s a special parameter w, which is a ratio of pressure to energy density of dark matter. It currently seems to be exactly -1, but different values of w yield different predictions for future fate of the universe.
  
  What you need to know about w, is that if it’s exactly -1, it means that dark energy is indeed constant and the universe is going to continue to expand ever faster, ultimately headed towards Heat Death.
  
  If it’s less than -1 (what’s called phantom dark energy), then the amount of energy somehow increases over time and we’re looking at the Big Rip scenario — the universe will eventually expand so fast that I’ll rip everything apart, even atoms. There’s some fun stuff that might happen if that’s the case, like boiling into a new big bang when trying to rip apart quarks (only works if there’s a lower matter energy state, I think), but that’s another topic and it’s highly speculative anyway.
  
  And if it’s between -1 and 0, it means that dark energy decreases over time, and the expansion is going to slow down and eventually reverse, leading to a Big Crunch, and possibly Big Bounce, implying that the universe “beats” like a heart.
  
  You can google Heat Death, Big Rip and Big Crunch to learn more.
  
  Now, what the paper is suggesting (I think, I haven’t found/received the original paper yet to read it in full) is that recent JWST observations might turn out to be a piece of further evidence that the cosmological constant might not actually be constant, but more like some parameter that can change over time and space. That would kinda lower the importance of w, since the constant becomes parametrized and the “fate” can change in the future regardless. But it doesn’t remove dark energy in any way (it’s a phenomenon that demonstrably exists), just alters our understanding about how the universe operates.
  
  Jeez that turned out to be a long comment. Hopefully my explanation wasn’t too convoluted :)
  
  @fearout @ourlifeintoronto Thanks. That was very comprehensive!
  
  Hey, so I got the paper from its original author, and I shared my thoughts in a recent comment. TLDR: the universe probably isn’t that old, and the models that predict it are somewhat weird and have little chance of actually being a true representation of reality. It’s more of an observation than a workable hypothesis.
  
  @ourlifeintoronto, I’d be interested to hear your reasoning for downvoting. Something you disagree with?
  
  The "cosmological constant," Is also known as the Hubble constant, it refers to the rate of expansion in the universe. By knowing the speed of expansion it would be possible to "Rewind" the universe (like a video) to get an estimation of the universes age. I believe the authors are suggesting that dark energy has a bigger effect on the red shift than previously estimated.
  As for Dark energy....
  That is a topic of much discussion, there is "Dark Matter" and "Dark Energy" that we know about, thanks to Einstein. When they refer to either it's safe to say that the don't fully understand what they are only that they are. Personally I believe that Dark matter is just a particle that has yet to be discovered, and that Dark energy is a result of that particles interaction with matter.
  
  Well, not really.
  
  First of all, neither were suggested by Einstein. The concept of Dark matter comes from a Swiss physicist Fritz Zwicky from the early 1930s. He noticed that stars on galaxies’ periphery are rotating much faster than they should, so he guessed that there should be extra mass that’s somehow undetectable.
  
  Dark energy concept is much younger, from 1990s. It was proposed by two astronomers trying to measure the rate at which expansion is slowing down, but discovered that it’s actually speeding up. Before that, it was believed that the universe got its initial speed kick from the Big Bang and is gradually slowing down. They won a Nobel prize for that too.
  
  And Dark energy and Dark matter are wildly different and likely totally unrelated concepts. I think it’s unfortunate that they share the same adjective, it’s somewhat confusing. One is the expansion phenomenon, and the other is just another form of matter (most probably formed by a yet undiscovered field, quite similar to ordinary matter in a sense), but one that just doesn’t interact with ordinary matter or via electromagnetic forces. We “see” it through gravitational effects though. But there are currently no links between it and the expansion of the universe, and for now it doesn’t look like there’s going to be one.
  
  Also, here are some other fun implications (besides the different age) that actually can come from this paper (that I can think of, there are definitely more):
  
  If the cosmological constant/rate of expansion acceleration may change over time, can it also change across space? Some parts of the universe might expand at different rates in this case.
  
  The fate of the universe is no longer defined by the value of w. It can behave in one way in current time, but change again and alter what awaits the universe in the future.
  
  New physics! Time-varying cosmological constant might force us to revise general relativity (since it’s specifically a constant there), or can somehow tie into quantum gravity, for example. Or suggest an existence of a yet undiscovered field.

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