- cross-posted to:
- science
- cross-posted to:
- science
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Terrible headline by the magazine. Nothing debunked, just a competing theory.
Further, the article says dark energy is used to explain the expansion of the universe, which is not true at all. Dark energy is the delta between the observed energy and the mathematically theorized required energy to drive the observed expansion of the universe, given what we know of physics. If either the observations of the expansion of the universe are challenged, or what we know about physics is challenged, then that delta could be eliminated entirely. It could also be reduced, and if it is reduced, then there’s still a delta that we would call Dark Energy.
Dark Energy is not a theory of a specific energy but rather a theory that some energy or energies must exist (that we have not yet observed) in order for the observations we DO have to make sense.
The headline isn’t great, but the article itself is interesting. Personally, I’ve always found dark energy to be just a kludge people came up with cause the observed data didn’t fit with the predictions of the standard model. However, now we have mounting evidence against the notion of dark energy, and MOND is starting to look like a better overall model.
The timescape model proposed in this study seems to complement MOND nicely. MOND modifies gravity to account for observed galactic behavior, so it doesn’t rely on dark energy to explain cosmic expansion, but doesn’t provide a rationale. This study argues that time moves slower in matter-dense areas (like galaxies) and faster in voids, creating the illusion of accelerated expansion.
I think the article gets better. The opening paragraphs all speak as though dark energy is an explanation when it’s literally the opposite of an explanation - it’s a gap between observations and models.
I think your framing can be improved along the same lines. It’s not that we have mountains of evidence against dark energy, it’s that we have mountains of evidence against the standard model. There’s only 3 things to do with dark energy - find new energy, show our observations are wrong, or show our model is wrong. Showing our model is wrong is not evidence against dark energy, it’s evidence against the model!
If we can build a more complex and nuanced model, like this Timescape model, then in theory we could have a model that matches our observations and eliminates the delta. I have to imagine it will take decades to work through the implications of such a model, and as history has shown us, the model will likely result in other gaps between observations and the model. “All models are wrong, some are useful” comes to mind here.
Basically, it looks like MOND is more closely aligned with what we observe and it wouldn’t require dark energy to work. And the timescape model might provide further support for it. I agree that it’s highly likely that the next models will also have gaps as well. The truth of the matter is that we haven’t really been probing the universe for all that long. We’ve only been able to do serious physics experiments where we probe the nature of reality for a a century at most. I’m sure there’s plenty left to be discovered.
and it wouldn’t require dark energy to work
Again, Dark Energy isn’t a thing. By MOND more closely aligning with what we observe, there is no gap between the amount of energy required to explain observations and the amount of energy observed.
I agree that it’s highly likely that the next models will also have gaps as well
The question, vis-a-vis dark energy, is whether those gaps will be a deficit of observed energy relative to the energy required to meet observations given the model. Other gaps could be fatal, even if they balance the energy dimension, and that could be incredibly informative for finding subsequent models.
And yes, it’s been 101 years since Edwin Hubble discovered that other galaxies even exist. In 1923, the accepted model was that the Milky Way was the entire universe.
I’m not talking just about dark energy, MOND is closer to measured observations of how gravity behaves at large scales.
Other gaps could be fatal, even if they balance the energy dimension, and that could be incredibly informative for finding subsequent models.
Sure, but key part is that the whole notion of dark energy only exists because the model we came up with is at odds with what we see happening. And since we didn’t have other models that were at least as good we needed to paper over that somehow.
It’s also worth noting that cosmology ultimately relates to how physics work at the smallest scales. It’s all a continuum, and everything builds on itself. Explaining what we see at the largest scales has to directly trace back to the smallest ones.
MOND is not widely accepted for a couple of reasons, but right here in Wikipedia we have this:
The most serious problem facing [MOND] is that galaxy clusters show a residual mass discrepancy even when analyzed using MOND.[6] This detracts from the adequacy of MOND as a solution to the missing mass problem, although the amount of extra mass required is a fifth that of a Newtonian analysis…
Sure, but key part is that the whole notion of dark energy only exists because the model we came up with is at odds with what we see happening
That’s accurate but not precise. The model we came up with matched the observations we had at the time, and then new observations came that challenged the model. Dark matter and dark energy are the gaps that would have to be filled with exotic matter and energy in order for the model to remain consistent with observations. Changing the model to eliminate these gaps is the work of many, but developing such a model is the work of multiple generations.
It’s also worth noting that cosmology ultimately relates to how physics work at the smallest scales. It’s all a continuum, and everything builds on itself. Explaining what we see at the largest scales has to directly trace back to the smallest ones.
Which is why developing new models takes generations.
I’m aware MOND also has problems, and it will take time to figure out how to reconcile them. It’s even possible that an entirely different model might be proposed. It’s hard to make predictions on how quickly these things will develop however because the rate of progress is not linear. We accumulate data at increasingly higher rate and fidelity, the tools we use to analyze the data that are constantly improving, and communication is becoming easier. All of these factors accelerate the rate of research. It’s also worth noting that stuff like machine learning can play a big role here as well. These systems are very good at finding patterns in data that would be impossible for humans to see. So, it may take generations to develop a new model or it make take decades. Personally, this isn’t something I’d bet money on.
