Dark Fudge

[Ray McCarthy]

The universe doesn't expand as expected.
The galaxies rotate more like solid disks than Keplerian orbital systems.
There are a few other anomalies.

The solutions to make the observations fit the equations was to propose dark energy and dark matter.

Dark Energy

In physical cosmology and astronomy, dark energy is an unknown form of energy which is hypothesized to permeate all of space, tending to accelerate the expansion of the universe. Dark energy is the most accepted hypothesis to explain the observations since the 1990s indicating that the universe is expanding at an accelerating rate.

Assuming that the standard model of cosmology is correct, the best current measurements indicate that dark energy contributes 68.3% of the total energy in the present-day observable universe.

Dark Matter

Dark matter is a hypothetical type of matter composing the approximately 27% of the mass and energy in the observable universe that is not accounted for by dark energy, baryonic matter, and neutrinos. The name refers to the fact that it does not emit or interact with electromagnetic radiation, such as light, and is thus invisible to the entire electromagnetic spectrum. Although dark matter cannot be directly observed with conventional electromagnetic telescopes, its existence and properties are inferred from its various gravitational effects such as the motions of visible matter, via gravitational lensing, its influence on the universe's large-scale structure, and its effects in the cosmic microwave background. Dark matter is transparent to electromagnetic radiation and/or is so dense and small that it fails to absorb or emit enough radiation to be detectable with current imaging technology.

Both Dark Energy and Dark Matter are essentially fudge factors to make the equations work. If there evidence they don't exist, then there is something wrong with observations, or the models/equations or something else we didn't think of applies. If you have more "Dark Matter" then you need more Dark Energy. Recent observations have been finding more stars obscured by dust in the Milky Way, two things to reduce the "Dark Matter". The space between the spiral arms has a lot of stars, just not as many as the visible spiral arms.

Estimates of masses for galaxies and larger structures via dynamical and general relativistic means are much greater than those based on the mass of the visible "luminous" matter.
The standard model of cosmology indicates that the total mass–energy of the universe contains 4.9% ordinary matter, 26.8% dark matter and 68.3% dark energy. Thus, dark matter constitutes 84.5% of total mass, while dark energy plus dark matter constitute 95.1% of total mass–energy content. The great majority of ordinary matter in the universe is also unseen, since visible stars and gas inside galaxies and clusters account for less than 10% of the ordinary matter contribution to the mass-energy density of the universe.

Note that all this "Dark Matter" and "Dark Energy" is hypothetical although Wikipedia gives impression it's fact, they do point out that these things are hypothetical.

Recent Hubble Telescope observations suggest the current assumptions are wrong.

If we know the initial amounts of stuff in the universe, such as dark energy and dark matter, and we have the physics correct, then you can go from a measurement at the time shortly after the Big Bang and use that understanding to predict how fast the universe should be expanding today.
However, if this discrepancy holds up, it appears we may not have the right understanding, and it changes how big the Hubble constant should be today.

Also here Universe's shock rapidly expanding waistline may squash Einstein flat

Hubble Constant

The Hubble constant, named after its discoverer American astronomer Edwin Hubble, is the rate at which objects in the universe expand over time. The new value is 66.53 (plus or minus 0.62) kilometers per second per megaparsec (3.26 million light-years). That means in 9.8 billion years the distance between cosmic objects will double.

El Ref says "the boffins" have narrowed it down to three possibilities.

1. Firstly, our calculation on the effects of dark energy could be wrong. Dark energy, which can't be detected on current instruments, is already causing the expansion of the universe and may have additional properties that theorists haven't accounted for.

2. The second option is that in the early period after the Big Bang, a new kind of subatomic particle burst out travelling at just under the speed of light. This would have sped up the expansion of the early universe and would explain the discrepancies in current theory.

   
   

3. The third option is that Einstein's theories of gravitation are wrong, or at least in serious need of revision. That opens up a whole new can of worms.

Surely too the very idea or quantity of Dark Energy and/or Dark matter may be wrong. The two are interlinked, because with less Dark matter, you don't need as much "Dark Energy" to have the Universe expanding. It's possible to fit the new observations simply by adjusting the amount of Dark Energy, which is hypothetical anyway!

"We know so little about the dark parts of the universe, it's important to measure how they push and pull on space over cosmic history," said Lucas Macri of Texas A&M University in College Station, a key collaborator on the study, published in The Astrophysical Journal.

 

[mosaix]

Surely too the very idea or quantity of Dark Energy and/or Dark matter may be wrong.

But the idea may be right as well, Ray. Until we know I think your term 'fudge' is a bit harsh.

 

[Ray McCarthy]

Dark Energy and Dark matter sound too much like the Luminous Ether, Aether and Phlogiston to be real. They are not based on any direct evidence and no theory predicts them nor suggests what they might be. We need better observations. They are PURELY "made up" because we have observations that don't quite fit the equations. The more likely solutions are that:

• Observations of the rotation of objects in the Galaxy are in error.
• There is something more complicated about gravity, it's the least understood of the four fundamental forces. That might account for strange behaviour of galactic rotation vs an individual star system.
  
• There are more actual stars in the observable universe and more dust, that's why we don't see them.
• Expansion observations are in error. This seems likely as they have changed what it is more than once I think.

Also it turns out that dust and hydrogen in space causes a down shift in frequency of EM due to the photon losing energy. This looks like Red Shift and obviously will increase with distance, creating illusion further away things are moving faster away than they really are. So we don't yet accurately know rate of expansion of Universe nor how many stars (and kind) our own galaxy has. Thus even if Dark Matter and Dark Energy are "real" the estimate for amount of them could be very badly wrong.

More observations needed.

 

[Brian G Turner]

The issue of "dark energy" came from that study on Type 1a supernovas. The findings - that some appeared more dim than they should - is not contentious. The conclusion, however, that there must be a mysterious new force in nature, was. Yet, astonishingly, it appears to remain unchallenged.

 

[Vertigo]

Unchallenged, I suspect, only until someone comes up with something that explains the facts better. I don't have a problem with the Aether and Phlogiston; they both worked for the science at the time and were replaced when we had better science (not without some resistance it must be said), and I'm sure the same will be the case for dark energy and matter. I see them as place holders until we have something better.

 

[Ray McCarthy]

I see them as place holders until we have something better.

Yes, that's what they are. I rather suspect we will eventually have something better.

 

[Vertigo]

I sincerely hope so!

 

[Ray McCarthy]

BBC article

"To be honest, with this latest measurement we've really gone beyond what we might call 'tension'; we're missing something in our understanding of the cosmos," the Nobel Laureate told BBC News.

Hubble clocks faster cosmic expansion - BBC News

 

[Ray McCarthy]

Independent UK (not to be confused with Irish one still on paper)
The universe is expanding way faster than it should be