3 ms·

I don't see where this explanation is strange, it's straightforward GR (General Relativity), as much as one can call GR "straightforward." It's a simpler explan

I don't see where this explanation is strange, it's straightforward GR (General Relativity), as much as one can call GR "straightforward." It's a simpler explanation than inventing Dark Energy, for which we have no direct observational evidence.

krunck 2y ago
I was wondering the same. It's just an application of GR in a way I thought people would have been doing already, right?
- PaulHoule 2y ago
  The equations are really simple for a homogeneous universe https://en.wikipedia.org/wiki/Friedmann_equations https://en.wikipedia.org/wiki/Friedmann_equations It's only recently that people have been able to handle the more complex case of an inhomogeneous universe. Scientists are often like the drunk who is looking for his keys under the lightpost.
  - cryptonector 2y ago
    > the more complex case of an homogeneous universe s/homogeneous/inhomogeneous/ ?
    - PaulHoule 2y ago
      Good call. I remember pretty clearly fighting with the spell checker on that one and I think it managed to change it when I wasn't looking. It's fixed!
SoftTalker 2y ago
> It's a simpler explanation than inventing Dark Energy Intuitively I never liked the Dark Energy theory. Doesn't seem valid to just make up an answer supported by no direct evidence for something you can't explain. It sounds a lot like religion in fact. But I never took physics after high school, so I always assumed I just didn't understand and had faith that these wise men knew what they were talking about.
- enasterosophes 2y ago
  I don't think it's accurate to compare it a theocratic phenomenon. Ask any physicist, they will say that science requires checking our theories against the evidence and changing our theories as new evidence comes to light. It's not like they issue scriptures to all grad students about what you must believe. In practice, science requires balancing multiple criteria. Does a model have the right level of simplicity and complexity? Can I convince my peers that it's correct? Should I trust the results of a crank over the results of someone who has a long history of excellent work, and how much onus is there on my me and my research group to reproduce every single published result? Keep in mind, no one expects to be responsible for a revolution, so you get an effect similar to "poll herding" -- it is desirable to have a consensus, and as consensus emerges around a theory for how to describe some new observations, you get people going along with it even if they maintain personal reservations. In fact, it has been clear to many physicists that dark energy is just an ad hoc explanation, and there has been serious contention about what better model could exist, and there have been several competing models. But every model had its flaws. It's possible that the timescape model will also have flaws that cause it to be re-evaluated. I recommend a book called "What is this thing called science?" by Chalmers [1]. When I was an undergrad it gave me a more nuanced understanding of the Philosophy of Science. [1] https://en.wikipedia.org/wiki/What_Is_This_Thing_Called_Science%3F https://en.wikipedia.org/wiki/What_Is_This_Thing_Called_Scie...
- antognini 2y ago
  Dark energy isn't really a theory, it's more of a placeholder for the observation that the universe's expansion is accelerating. There are a variety of ways you can potentially explain this observation. The simplest theory is the standard lambda-CDM model for dark energy where it is taken to be a cosmological constant. This model has worked well for about 20 years or so, but it is starting to come in tension with newer high precision observations.
  - SoftTalker 2y ago
    That seems reasonable; I guess I'd rather hear "for reasons we don't understand the universe appears to be expanding and the expansion is accelerating by a constant factor we're calling 'lambda'." But I guess "dark energy" is fewer words, if that's what it means.

krunck 2y ago

I was wondering the same. It's just an application of GR in a way I thought people would have been doing already, right?

PaulHoule 2y ago
The equations are really simple for a homogeneous universe https://en.wikipedia.org/wiki/Friedmann_equations https://en.wikipedia.org/wiki/Friedmann_equations It's only recently that people have been able to handle the more complex case of an inhomogeneous universe. Scientists are often like the drunk who is looking for his keys under the lightpost.
- cryptonector 2y ago
  > the more complex case of an homogeneous universe s/homogeneous/inhomogeneous/ ?
  - PaulHoule 2y ago
    Good call. I remember pretty clearly fighting with the spell checker on that one and I think it managed to change it when I wasn't looking. It's fixed!

SoftTalker 2y ago

> It's a simpler explanation than inventing Dark Energy Intuitively I never liked the Dark Energy theory. Doesn't seem valid to just make up an answer supported by no direct evidence for something you can't explain. It sounds a lot like religion in fact. But I never took physics after high school, so I always assumed I just didn't understand and had faith that these wise men knew what they were talking about.

enasterosophes 2y ago
I don't think it's accurate to compare it a theocratic phenomenon. Ask any physicist, they will say that science requires checking our theories against the evidence and changing our theories as new evidence comes to light. It's not like they issue scriptures to all grad students about what you must believe. In practice, science requires balancing multiple criteria. Does a model have the right level of simplicity and complexity? Can I convince my peers that it's correct? Should I trust the results of a crank over the results of someone who has a long history of excellent work, and how much onus is there on my me and my research group to reproduce every single published result? Keep in mind, no one expects to be responsible for a revolution, so you get an effect similar to "poll herding" -- it is desirable to have a consensus, and as consensus emerges around a theory for how to describe some new observations, you get people going along with it even if they maintain personal reservations. In fact, it has been clear to many physicists that dark energy is just an ad hoc explanation, and there has been serious contention about what better model could exist, and there have been several competing models. But every model had its flaws. It's possible that the timescape model will also have flaws that cause it to be re-evaluated. I recommend a book called "What is this thing called science?" by Chalmers [1]. When I was an undergrad it gave me a more nuanced understanding of the Philosophy of Science. [1] https://en.wikipedia.org/wiki/What_Is_This_Thing_Called_Science%3F https://en.wikipedia.org/wiki/What_Is_This_Thing_Called_Scie...
antognini 2y ago
Dark energy isn't really a theory, it's more of a placeholder for the observation that the universe's expansion is accelerating. There are a variety of ways you can potentially explain this observation. The simplest theory is the standard lambda-CDM model for dark energy where it is taken to be a cosmological constant. This model has worked well for about 20 years or so, but it is starting to come in tension with newer high precision observations.
- SoftTalker 2y ago
  That seems reasonable; I guess I'd rather hear "for reasons we don't understand the universe appears to be expanding and the expansion is accelerating by a constant factor we're calling 'lambda'." But I guess "dark energy" is fewer words, if that's what it means.