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Evidence that the key assumption made in discovery of dark energy is in error

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Re: Evidence that the key assumption made in discovery of dark energy is in error

#221

Post by SAI_Peregrinus »

Koshkin wrote: post #186
Certhas wrote: post #169

Earlier quoted context omitted.

No space really is expanding. Think of it this way: You have a rubber band and you pull it apart, if you place two beads on the rubber band the distance between the beads will increase (even though they don't move relative to the rubber). But if you connect the two beads by a strong spring, then their distance will stay the same, despite space expanding. The force of the spring makes them move (relative to the rubber…

> relative to the rubber This makes me uneasy about your analogy. It’s like saying “relative to space” which is nonsense. Also, why would space limit itself to only expanding outside a physical body?

> Also, why would space limit itself to only expanding outside a physical body?

It doesn't, it's just that the forces within the body (the spring in the analogy) are stronger than the expansion.

The "relative to space" bit is the nonsense part of their analogy, but I'm not sure of a clearer way to describe things than what they did. It's not my field.

Re: Evidence that the key assumption made in discovery of dark energy is in error

#222

Post by shpeak »

Certhas wrote: post #215
shpeak wrote: post #183

Earlier quoted context omitted.

Such counteract action will make lot of side effects, which can be measured. For example, trajectories of separating or oscillating bodies will be slightly curved. Do you have any experimental support for this theory?

The effect of the expansion of the universe on bound systems is far to small to be observed. Two objects 1 meter apart would move at a speed of 10^-17 m/s. Utterly unobservable. But we know space is expanding by looking at things that are super far away from us and that are not bound.

We can directly measure distance to stars which are near us, using trigonometry and waiting half of year for Earth to make half of distance around Sun. Distance to thousands of stars is already measured with ±5% precision.[0] Yes, it's true that at least some stars, which are near to us, are moving away from us. However, it can be explained in number of ways, without inventing of Bing Bang or other epic events.

We cannot measure distance to super far away stars directly. Period.

10^-17 m/s is very high speed. Distance to Moon is 0.385E15 mm, and it can be measured at sub-millimeter accuracy, so this effect can be spotted. However, it will violate Conservation of Energy principle: no force applied, but job is done.

0: https://www.youtube.com/watch?v=i6GhsYrU5WQ

Re: Evidence that the key assumption made in discovery of dark energy is in error

#223

Post by bananabreakfast »

zaroth wrote: post #114
Tenemo wrote: post #108

Earlier quoted context omitted.

Your ruler is absolute distances, like the speed of light. You can inflate or deflate the balloon and the number of marks on its surface won't change. But the time required for the light to travel between them will.

Stupid question - How do you know for certain it isn’t just that light is slowing down? Relativity probably doesn’t work this way at all, but if light did actually slow down, would it be perceived by us as light moving at the same speed across a greater distance?

Not exactly. Remember, we're not timing the light's transit. We're observing a redshift of it's frequency which could not be caused by c simply decreasing over time.

Re: Evidence that the key assumption made in discovery of dark energy is in error

#224

Post by stefantalpalaru »

doodliego wrote: post #73
carbocation wrote: post #8

Earlier quoted context omitted.

This doesn't really address your point, but the 2011 physics Nobel [1] said that "What is known is that dark energy constitutes about three quarters of the Universe." Not saying the Nobel write-ups constitute evidence, but dark energy has certainly been popular, at least. 1 = https://www.nobelprize.org/prizes/physics/2011/press-release...

The Luminiferous Aether was popular too.

> The Luminiferous Aether was popular too.

It still is: https://en.wikipedia.org/wiki/Quantum_field_theory

Re: Evidence that the key assumption made in discovery of dark energy is in error

#225

Post by bananabreakfast »

JackFr wrote: post #104
Hendrikto wrote: post #97

Earlier quoted context omitted.

Your interpretation of the expansion is incorrect. Basically, it looks like all points are moving away from each other over large distances. It is easier to understand in 2D: Imagine a deflated balloon with two dots drawn on it. When you inflate the balloon, its 2D surface increases, which results in the two points "moving away" from each other, without either of them actually moving. It‘s just that the surface on wh…

What's still not clear is how I know the other point on the surface of the ballon is moving away from me? I measure it as 9 tick marks away. After inflation it's still nine tick marks. That is to say, what is my ruler that is untethered to the surface of the balloon?

It's incorrect to think with this analogy. There is no ruler reaching across the universe, growing with it.

It is not the meter that is growing, that's impossible. Instead you must see it as it is, which is that there are more meters continuously appearing in all of space.

Re: Evidence that the key assumption made in discovery of dark energy is in error

#226

Post by antman »

Certhas wrote: post #215
shpeak wrote: post #183

Earlier quoted context omitted.

Such counteract action will make lot of side effects, which can be measured. For example, trajectories of separating or oscillating bodies will be slightly curved. Do you have any experimental support for this theory?

The effect of the expansion of the universe on bound systems is far to small to be observed. Two objects 1 meter apart would move at a speed of 10^-17 m/s. Utterly unobservable. But we know space is expanding by looking at things that are super far away from us and that are not bound.

Any objects? So it's independent of mass?

Re: Evidence that the key assumption made in discovery of dark energy is in error

#227

Post by shpeak »

simcop2387 wrote: post #96
cjonas wrote: post #93

Earlier quoted context omitted.

My (limited) understanding is that only space is expanding. Iow there is more space but the space that matter takes up stays constant. Maybe I'm also confused though

That's basically my lay-person's understanding also. It's because the expansion isn't significant at small scales, so gravity and electromagnetism overpower it. This causes existing objects and clouds to effectively remain the same size [I have to assume that there's an effect, stealing potential energy at very small scales].

Gravity and EM are holding our galaxy, our Laniakea, our Universe. See https://www.youtube.com/watch?v=rENyyRwxpHo .

Re: Evidence that the key assumption made in discovery of dark energy is in error

#228

Post by Certhas »

antman wrote: post #226
Certhas wrote: post #215

Earlier quoted context omitted.

The effect of the expansion of the universe on bound systems is far to small to be observed. Two objects 1 meter apart would move at a speed of 10^-17 m/s. Utterly unobservable. But we know space is expanding by looking at things that are super far away from us and that are not bound.

Any objects? So it's independent of mass?

Yes, any two bound objects will do so, irrespective of their mass or anything else.

Re: Evidence that the key assumption made in discovery of dark energy is in error

#229

Post by raattgift »

cygx wrote: post #148
raattgift wrote: post #127

Earlier quoted context omitted.

> The Universe is expanding at every known point at the same time at the same rate No, it's not. The (local) metrics sourced by the Earth, Earth-Moon, Sun, solar system, Milky Way, and the Local Group are not at all like FLRW with or without a cosmological constant, while all those metrics are very much like Kerr or LTB, wherein ordinary matter like gas and dust gradually condenses into a point. Conversely, the metri…

Kinematical interpretations fall apart really spectacularly I disagree: Relativistic frequency shifts (doppler shift, gravitational shift, cosmological shift,...) can all be understood kinematically: The invariant quantity you have to consider is photon 4-momentum, with energies at time of emission and absorption given by the projections onto the 4-velocities of the respective observers, so it's all about the relativ…

I'm pretty sure we were talking about the ensemble of redshifts across the sky, rather than one particular photon. (Even in the single-photon case there will be lots of uncertainty about the \lambda_{obsv} vs \lambda_{emit} relationship; think in particular about its interaction with ions along the way. We'd want at least an "ensemble" of photons along the lines of a classical beam equipped with a spectrum).

I'm not sure if you are objecting to approaches like the tetrad formalism in your final sentence, or even to gauge freedom itself. There's no reason an observer -- even an always lightlike one -- can't carry around its own system of coordinates. People from ISS astronauts (LVLH vs ECEF/ITRF) to aerobatic pilots (LVLH/LENU to GPS) to pedestrians looking at map apps on their smart phones do that casually all the time, and nobody expects ensembles of objects to move with respect to each other as one swaps sets of coordinates. Setting a new coordinate system every few steps while navigating on foot through a complicated city core is perfectly fine, and so is setting up a new coordinate frame at every infinitesimal step along an affine-parametrized curve traced out by a photon. IMHO that is the core of relativity.

Re: Evidence that the key assumption made in discovery of dark energy is in error

#230

Post by Certhas »

shpeak wrote: post #222
Certhas wrote: post #215

Earlier quoted context omitted.

The effect of the expansion of the universe on bound systems is far to small to be observed. Two objects 1 meter apart would move at a speed of 10^-17 m/s. Utterly unobservable. But we know space is expanding by looking at things that are super far away from us and that are not bound.

We can directly measure distance to stars which are near us, using trigonometry and waiting half of year for Earth to make half of distance around Sun. Distance to thousands of stars is already measured with ±5% precision.[0] Yes, it's true that at least some stars, which are near to us, are moving away from us. However, it can be explained in number of ways, without inventing of Bing Bang or other epic events. We ca…

What's your point? Do you want me to explain the basics of GR and Cosmology, including the vast amounts of evidence we have for everything in HN comments? Do you think you are pointing out subtle errors in reasoning that none of the tens of thousands of physics students since the early twentieth century spotted?

You don't have the decency to try to learn the basics but presume to lecture me/expect explanations? Take a course. Show a little humility. Even reading Wikipedia thoroughly would have informed you that it's galaxies, not stars that confirm the expansion of the universe. The expansion (not the acceleration of the expansion) is beyond doubt. Conservation of Energy is not a priory defined for the question at hand because in GR you can not just add the energy at different points in space.

Measuring the perturbation to the moon's trajectory from expansion would require knowing all parameters that enter the trajectory to this accuracy, not just the average distance.

This is all basic if you want to learn, but you seem to have a different agenda...

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