Dark Energy Wrong?

[BiotechFusion]

I can't remember what it was, but supposedly proponents of Dark Matter were challenged to predict the accuracy of Dark Matter theory by predicting where satellite galaxies around the Milky Way would be in 5 years. Their opponents were a group of scientists who claimed that dark matter didn't exist but only that the gravitational constant varied with distance.

 

Despite all the hype of dark matter, the gravitational constant group came out ahead with amazing accuracy while the dark matter group was very far off.

 

First question is: does anyone know the name of this experiment?

 

Second question is: I don't have a particular preference for dark matter theory, but varying gravitational constant is kind of a no-brainier almost like curve-fitting so of course its going to work if you fine tune your values. With this theory, what is the explanation for how specific, localized regions appear a lot more dense than they should be using this gravitational constant theory? Like for instance rings around galaxies that have been identified as having a higher gravity than measurable matter can account for, not the interior of the galaxy, not millions of light-years from the galaxy, a ring right around it? And what of the hubble boundary of the universe? Is it suppose to be some kind of illusion caused by how our apparent physics changes with distance, which would also affect several universal constants or is space actually still expanding with no dark model? There's so many other things that would have to vary with distance as well like Planck length, Planck time and Planck mass and Planck temperature. How does this model actually explain everything we're seeing? What's the actual explanation?

Edited April 27, 2016 by BiotechFusion

[Delta1212]

This topic seems more like it's about Dark Matter than Dark Energy.

[swansont]

From what I've read, the problem with any modified Newtonian models is that when they're tuned to one length scale, they fail pretty spectacularly elsewhere.

[Mordred]

I believe the two models is LCDM vs MOND.

[BiotechFusion]

I believe the two models is LCDM vs MOND.

Hold up, why not just say dark matter itself causes variations in the gravitational constant instead of having two different theories try to predict the same kind of thing about gravity? It would give dark matter its accuracy and give MOND the mechanism.

[Mordred]

Neither model suggests that dark matter causes variations in the gravitational constant. There isn't any scientific evidence that supports a varying gravitational constant.

 

MOND describes variations in Newtons acceleration equations in order to replace dark matter.

 

LCDM is the BB model that uses cold dark matter and dark energy aka the cosmological constant.

 

Dark energy and dark matter are two separate entities.

 

You have no idea how many posters try to invent their own model, to replace dark energy or dark matter. Let alone relativity.

Amazing enough they rarely understand the concordance models in the first place and rarely understand the associated math or physics.

 

Some attempts are similar to what you posted, yet they never heard of the NFW profile for galaxy rotation curves.

Edited April 28, 2016 by Mordred

[elfmotat]

Hold up, why not just say dark matter itself causes variations in the gravitational constant instead of having two different theories try to predict the same kind of thing about gravity? It would give dark matter its accuracy and give MOND the mechanism.

 

When the gravitational constant is promoted to a field, the result is Brans-Dicke Theory. The new field must obey a field equation that constrains it to behave according to basic physical principles like Lorentz symmetry, locality, etc.

 

Modified gravity theories that attempt to reproduce observed galaxy behavior without dark matter like TeVeS are even more complicated, introducing a new type of vector field, a non-dynamical scalar field, and a dynamical scalar field like the one in Brans-Dicke Theory. Gravity theories of this sort have largely been ruled out as they fail to explain behavior like the gravitational lensing in the Bullet Cluster.

Edited April 28, 2016 by elfmotat

[Mordred]

LCDM has an extremely high confidence level in accuracy however MOND has a couple of successes in better predictions in rotation curves for certain specific galaxy types. Yet MOND gradually lost out to LCDM as the latter model became more and more fine tuned.

 

This is one aspect many don't realize is that sometimes competing models provide an aid to better improve the models its competing against. Simply by showing where improvements is necessary.

 

With galaxy rotation curves the problem can be complex, while one metric has high accuracy with spiral galaxies, those same metrics become less accurate on dwarf galaxies.

 

The most successful metric for galaxy rotation curves is the Navarro Frenk White profile.

 

https://en.m.wikipedia.org/wiki/Navarro%E2%80%93Frenk%E2%80%93White_profile

 

However this does absolutely nothing for anything other than rotation curves.

This metric is extremely successful in all galaxy rotation curves, as it better correlates the enclosed mass as a function of radius compared to the Keplar methodology which MOND originally competed against. Just a side note eventually the later MOND models also required dark matter, but didn't use cold dark matter.

Edited April 28, 2016 by Mordred

[BiotechFusion]

Hmm guess it was bad intel then, not the theory I thought it was but I guess in the end they did reconcile each other to some extent.

Edited April 28, 2016 by BiotechFusion

[Mordred]

Kind of hard to tell without knowing exactly which study your referring to in your OP. I mentioned two of the more popular competing models. (At least as far as rotation curves go)

[ajb]

There is also some work in progress by various people looking into the idea that breaking the assumption of homogenety in the cosmological models can explain dark energy. You will have to do a literature serach yourself, all I know is that I attended a few talks on the subject a few months ago. Not really my thing.

[Velocity_Boy]

So, which entity are we actually discussing here?

 

Dark Energy? As mentioned in your Thread Title?

 

Or Dark Matter, as you went on to speak of (sort of) in the text of your OP?

 

I trust you ARE aware they are two totally different entities.

 

Or forces, might be more accurate.

 

We actually not one scintilla what EITHER is comprised of.

 

All we have done is given those two names to explain what is causing the cosmological phenomenons we have observed but cannot explain with traditional Newtonian mechanics.

 

Or, Hubblerian or Planckian meahcnaics!

 

Did I just make up two words? LOL.

 

But its true. We simply observed that the galaxies in the known Universe are receding faster than they should, especially at the outer edges, so we say some sort of Dark Energy is involved.

 

And conversely see the galaxies themselves "sticking" together tighter and more coherently then they should given our know understanding of gravitational mechanics. So we use the term Dark Matter to explain that. Which, btw has been around, the word, for a lot longer than most folks think: some 70 years now!

 

The Dark Energy, though, is a repetitively new discovery. Only about a decade or so ago.

 

Funny, eh? Despite all of our so-called advances in Cosmology, we now know that we DON'T know what 90% of the Universe is comprised of!

 

Oh....the Creationists must be wetting themselves at this one!

 

Thanks.

 

 

http://www.space.com/4554-scientists-dark-matter-exist.html

Edited April 29, 2016 by Velocity_Boy

[J.C.MacSwell]

 

 

So we use the term Dark Matter to explain that. Which, btw has been around, the word, for a lot longer than most folks think: some 70 years now!

 

 

 

 

 

some 80+ so...yeah

[swansont]

So, which entity are we actually discussing here?

 

Dark Energy? As mentioned in your Thread Title?

 

Or Dark Matter, as you went on to speak of (sort of) in the text of your OP?

 

I trust you ARE aware they are two totally different entities.

 

Or forces, might be more accurate.

 

Matter is matter, energy is energy. Neither are forces.

[Velocity_Boy]

Matter is matter, energy is energy. Neither are forces.

Really?

 

You need a Physics 101 class, bro.

 

Everything is energy!

 

Even you.

 

Potential energy.

 

More than a nuclear bomb.

 

Look it up.

 

Thanks.

 

 

 

http://www.lifetrainings.com/We-are-made-of-Energy-not-Matter.html

Edited April 30, 2016 by Velocity_Boy

[swansont]

"Life Trainings" is your reference for this? What's next? Deepak Chopra quotes?

[Phi for All]

Really?

 

You need a Physics 101 class, bro.

 

"Tune in next week as Velocity_Boy attempts to remove his foot from his mouth using PHYSICS!"

 

A physicist with the US Naval Observatory can teach a higher level class than that, bro.

[MigL]

Just to be fair to Velocity_Boy, he did a more than fair job of explaining things.

 

What Swansont mentioned is true, matter is matter and energy is energy, and neither are forces.

However...

 

We postulate dark matter. None has been identified yet.

All we have are observations of modified galactic rotation in response to a ( gravitational ?? ) force.

What this force is due to, dark matter or not, is yet to be determined.

 

We postulate dark energy, and associate it with the Cosmological Constant.

Yet we have not been able to derive this from first principles and get a meaningful result ( 120 orders of magnitude too high ??? ).

All we observe is distant galaxies moving away at accelerating rates, and speculate that it is vacuum pressure which provides this force.

 

In other words neither matter nor energy, directly cause a test mass to change its motion. Forces do that.

That being said, matter and energy DO give rise to forces by their very presence, and so indirectly, cause changes in motion.

( or sometimes directly, as in collisions )

Edited April 30, 2016 by MigL

[Strange]

All we have are observations of modified galactic rotation in response to a ( gravitational ?? ) force.

What this force is due to, dark matter or not, is yet to be determined.

 

We have a quite a bit more than that. But your point still stands, we haven't identified it yet.

Edited April 30, 2016 by Strange

[Velocity_Boy]

"Tune in next week as Velocity_Boy attempts to remove his foot from his mouth using PHYSICS!"

 

A physicist with the US Naval Observatory can teach a higher level class than that, bro.

I don't think my foot is Anywhere near my mouth, bro.

 

What are you not getting about this?

 

All matter is comprised of potential energy.

 

I'm actually working on paper right now in fact, about something we call Zero Point Energy.

 

But that's a bit off topic.

 

Anyway...here's a bit more for ya.....

 

 

http://www.askamathematician.com/2010/01/q-is-it-true-that-all-matter-is-simply-condensed-energy/

[Strange]

That article really doesn't support your claim. Quite the reverse, in fact. Apart from anything else, you are ignoring charge, mass and all the other conserved quantities.

[MigL]

I tried to help him extract his foot with a little grace...

But he's not helping himself with the attitude.

[swansont]

I don't think my foot is Anywhere near my mouth, bro.

What are you not getting about this?

All matter is comprised of potential energy.

I'm actually working on paper right now in fact, about something we call Zero Point Energy.

But that's a bit off topic.

Anyway...here's a bit more for ya.....http://www.askamathematician.com/2010/01/q-is-it-true-that-all-matter-is-simply-condensed-energy/

At the very basic level, things aren't made of energy because energy isn't a substance, it's a property. Things aren't made of energy any more than they are made of tall.

 

Phrases like "turning back into energy" are lazy pop-science schlock.

[Prophet12A]

The theory of Dark Energy or Dark Matter is an error or wrong.... It is the wrong's way to explain the inexplainable....which stems from the error of believing the universe is 'expanding at an ever increasing rate' promoted by the expansionism belief. When the expansionist's belief is flipped to think of it as contracting and contracting at an ever increasing rate....the truth and the rest becomes 'scientifically explainable' while the dark matter/energy crowd can stop searching for nothing in the dark.

[Mordred]

It's never a good idea to attempt to answer questions on a forum based on your personal feelings or arguments.

 

For one thing expansion has very little to do with dark matter. Even if the universe was contracting you would still need dark matter for galaxy rotation curves and early large scale structure formation.

 

Secondly scientists didn't say ooh lets have dark energy and make the universe expand.

 

Measurement data shows the universe is expanding in both distance and temperature thermodynamic relations.

 

However the universe doesn't require dark energy to explain how a universe expands. Its needed to explain why that expansion isn't slowing down.