We know that Jupiter and Saturn are made mostly of helium and hydrogen, but is this true for other systems and their gas giants too?
We know that Jupiter and Saturn are made mostly of helium and hydrogen, but is this true for other systems and their gas giants too?
That’s not really true though. There are multiple lines of evidence. We can calculate the mass, we see the effects through gravitational lensing, there’s the CMB evidence etc. And we can’t forget the bullet cluster, which has a different distribution of dark matter, showing that most theories that make some global changes to physics such as MOND cannot be true.
This is way more than fudge factor. Everything is consistent with a something that doesn’t interact except through gravity.
As for dark energy, this very question was covered in a podcast that you might be interested in listening to. https://www.iheart.com/podcast/105-daniel-and-kellys-extraord-29862087/episode/is-dark-energy-a-fudge-factor-343402032/
That evidence is not evidence of dark matter (that’s the problem), it’s evidence that we’ve modeled gravity or spacetime or inertia or whatever wrong.
It’s like drawing triangles on spheres or other non euclidean spaces, but for mass/inertia. Maybe the problem with the Hubble constant is the clue.
If you need a big fat invisible undetectable magic amount of mass or energy to make it all work, perhaps some of the underlying assumptions are incorrect.
It might be a big fat invisible undetectable magic amount of mass or energy, but it’s not the only option. It is an inelegant option.
How can any change to gravity globally accurately describe the bullet cluster? I’ve never seen a MOND theory even try to do that. They keep talking about galaxy rotation and forget all the other lines of evidence.
There is a lot of evidence that motion and gravitational lensing at the scale of galaxies doesn’t behave how we would expect from the mass we see and relativity.
The obvious solutions there are:
Dark matter is the theory with the most support, but there are plenty of problems with it as well. For one, we’d need the majority of the matter in the universe to be dark, and we have essentially no theory for what it would be. Obviously no way to ‘see’ it, and no way to detect it beyond gravitational effects. Any theory that relies on the presence of an absolutely massive amount of invisible and conveniently distributed stuff is going to face challenges.
MOND has also faced trouble, no theory here has accounted for all observations.
We must also remain open to the possibility that some observations are true evidence for an unknown massive particle, and some are the result of an incorrect understanding of gravity.
There appears to be quite some debate between several competing theories.
Apparently MOND can explain that cluster with ‘only’ additional cold hydrogen.
The authors of the paper this article is talking about graded their own work. These are the model’s builders testing it with their own code. An outside group checked it against 32 independent expansion-rate measurements and concluded it faces significant challenges…
https://academic.oup.com/mnras/article/547/3/stag430/8507252
I get people wanna jump to different explanations for DE and DM, but it needs to fit all the data points already gathered and organized into a theory to be a better explanation than ∆CDM model. No one is saying ∆CDM is perfect or absolutely fully correct or the final answer, just that the models fit it the best at the moment. It most certainly isn’t the correct model, their too much discrepancy in the calculated and apparent DE by a huge order or magintude. But it’s the best model at the moment.
It’s not tired light folks, sorry 🙃
There’s very little serious debate outside of niche interner forums populated by non-physicistsv weirdly enough.