3 ms·

> If you think there are others, please exhibit one. I could easily do that (god tinkering with our measurements? we live in a simulation?) but explanations by

> If you think there are others, please exhibit one. I could easily do that (god tinkering with our measurements? we live in a simulation?) but explanations by themselves are worthless. Any set of facts can be "explained" but it doesn't really help. The science is concerned with theories that don't just explain known facts and measurements but also predict new ones. These are also known as falsifiable theories because a theory is falsifiable IFF it predicts at least one new observation that can be actually made and tested. Now even these can obviously be constructed ad infinitum. For your question of alternatives to expansion, take a theory from the same field (e.g. tired light), then take facts it doesn't fit and make specific ad-hoc carve-outs for these facts in the theory. Sure it makes it ugly and complex but it remains a scientific falsifiable theory. Furthermore this exact things happens very often in the scientific community because theories don't fall immediately when the first contradiction is found. They only fall when a better theory appears to supersede them and until then they just develop a "protective belt of ad-hoc assumptions" as Lakatos called it. No need to mention that the same thing will happen to the "better theory" in due time. I write all of this not because I have a good cosmological theory sitting in my closet but rather because your statement "The totality of all the observations we have cannot be explained in any other way than an expanding universe" is outright false. As I show above it not only can be explained in an infinite number of ways, but you can also construct and infinite number of scientific theories that fit the totality of observations. Because this "totality" is alas finite. This reminds me of my school math teacher who once told me that "the sequence 1, 2, 6, 24, 120, 720 cannot be explained other way than by n!". A pity I didn't know about Lagrange Polynomials at that age and had to spend the whole evening to construct a fitting polynomial by hand.

fpoling 2y ago
A big problem of the modern cosmology is not only that we have observations that do not fit models but that we do not know if the observed discrepancies are the real problems with the models or are artifacts of calculations. For example, to simulate a galaxy one should use a model based on General Relativity. But mathematics behind GR is too complex to allow simulations on the scale of the galaxy even with all that modern computation power. So instead of GR the calculations use Newtonian mechanics with minimal corrections for the light speed limit. Plus there are a lot of other simplifications like replacing star systems with hard balls that reflects when hit each other with no notion of matter transfer or ejection in the process. Then we see that the simulation does not fit data. A typical explanation that is used is that of dark matter hypothesis. But this is unjustified. We have no proof that numerical simplifications are mathematically valid and do not lead to a big error on a galactic scale. Moreover, there were recent papers that tried to account at least for some effect of General Relativity. Apparently it was enough to explain at least some effects previously attributed to the dark matter. So it can be that the dark matter is just an artifact of inaccurate simulations.
- adrianN 2y ago
  Do you maybe have links for the papers you mention?
  - fpoling 2y ago
    See references on Wikipedia page https://en.m.wikipedia.org/wiki/Galaxy_rotation_curve https://en.m.wikipedia.org/wiki/Galaxy_rotation_curve under “alternatives to dark matter”.
- aragilar 2y ago
  Not a cosmologist, so I'll defer to any simulators who are more up-to-date with the field than I am, but the papers linked from wikipedia are about the fitting of models to existing data, and by using a more complete model, they can better constrain values in the models; whereas the massive 3D simulations are looking at a different problem, and go through a rigorous level of validation and cross-checking, with different microphysics tested and examined. Both dark matter and dark energy fall out of GR—they can both be zero, but they can also be non-zero.

fpoling 2y ago

A big problem of the modern cosmology is not only that we have observations that do not fit models but that we do not know if the observed discrepancies are the real problems with the models or are artifacts of calculations. For example, to simulate a galaxy one should use a model based on General Relativity. But mathematics behind GR is too complex to allow simulations on the scale of the galaxy even with all that modern computation power. So instead of GR the calculations use Newtonian mechanics with minimal corrections for the light speed limit. Plus there are a lot of other simplifications like replacing star systems with hard balls that reflects when hit each other with no notion of matter transfer or ejection in the process. Then we see that the simulation does not fit data. A typical explanation that is used is that of dark matter hypothesis. But this is unjustified. We have no proof that numerical simplifications are mathematically valid and do not lead to a big error on a galactic scale. Moreover, there were recent papers that tried to account at least for some effect of General Relativity. Apparently it was enough to explain at least some effects previously attributed to the dark matter. So it can be that the dark matter is just an artifact of inaccurate simulations.

adrianN 2y ago
Do you maybe have links for the papers you mention?
- fpoling 2y ago
  See references on Wikipedia page https://en.m.wikipedia.org/wiki/Galaxy_rotation_curve https://en.m.wikipedia.org/wiki/Galaxy_rotation_curve under “alternatives to dark matter”.
aragilar 2y ago
Not a cosmologist, so I'll defer to any simulators who are more up-to-date with the field than I am, but the papers linked from wikipedia are about the fitting of models to existing data, and by using a more complete model, they can better constrain values in the models; whereas the massive 3D simulations are looking at a different problem, and go through a rigorous level of validation and cross-checking, with different microphysics tested and examined. Both dark matter and dark energy fall out of GR—they can both be zero, but they can also be non-zero.