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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

#111

Post by allovernow »

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?

I think physical forces (electromagnetism, gravity, strong/weak nuclear) probably become weaker even though your metric (9 ticks) stays the same. I'm just guessing here, that's the only consequence I can think of.

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

#112

Post by ncmncm »

ltbarcly3 wrote: post #92
ncmncm wrote: post #85

Earlier quoted context omitted.

Conservation of energy has only ever been observed in local conditions. The universe is not obliged to respect our local expectations, and has always turned out to violate them in uncomfortable ways. The ground looks flat near you (at least in Nebraska). The Sun seems to go around Earth.

Which is more likely, that you can have infinite free energy or that the very careful measurements of the distances to supernova that happened billions of years ago on the other side of the universe, and for which we have virtually no standard yardstick to compare against are not accurate? You are just making an appeal to ignorance. All of physics and astronomy is based on the assumption that the rest of the universe…

That is the condition of cosmology. Not everyone envies it.

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

#113

Post by adrianN »

cjonas wrote: post #93
dieppe wrote: post #90

Earlier quoted context omitted.

> The Universe is expanding at > every known point at the same > time at the same rate This part I don't get (I am in no way versed in astrophysics). If I am in a box, and that the box grows 10%, but that at the same time I grow 10%, what has changed? I mean, if every point in the universe expands at the same rate at the same time, what does it change? Relatively speaking, everything is the same size before and after…

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

As I understand it, the forces that keep matter together are strong enough to counteract any expansion.

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

#114

Post by zaroth »

Tenemo wrote: post #108
JackFr wrote: post #104

Earlier quoted context omitted.

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?

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?

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

#116

Post by sanxiyn »

kiliantics wrote: post #52
mirimir wrote: post #45

Earlier quoted context omitted.

That's how I understand it. But maybe there are other standardizable objects. The sense I got from TFA is that there aren't .

There are actually. There is a class of star in the "tip of the red giant branch" (TRGB) which have also been used to calibrate luminosities of type Ia supernovae[0] to form a "cosmic distance ladder". I believe they have been used to confirm the accelerated expansion results (though less strongly). I am not super well versed in stellar evolution, but I believe that the TRGB should make this calibration method indepe…

Nope, the link is proposing TRGB-SNIa as an alternative to Cepheid-SNIa, not TRGB as an alternative to SNIa.

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

#117

Post by Jweb_Guru »

ncmncm wrote: post #83
platz wrote: post #66

Sabine Hossenfelder comments on this paper: Dark Energy might not exist after all https://youtu.be/oqgKXQM8FpU

Amusingly, this video is about entirely different work that also calls into question the basis for claims about dark energy. Nobody seems to be saying how the two results interact. Taking away dark energy twice could give us negative dark energy, which would be fun. I don't know whether unexpected negative dark energy would be more embarrassing than unexpected zero dark energy.

It sounds like the earlier article is pretty flawed and doesn't control for things like redshift associated with the motion of the solar system, so I very much doubt that the observations in that paper will end up "stacking" with those in this one. I'm no expert, but it seems like this more recent paper presents a much more serious challenge to the existence of dark energy.

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

#118

Post by j-dr »

Even if this paper is correct, there is still overwhelming evidence for dark energy provided by other observations, in particular those of the Cosmic Microwave Background (CMB) and Baryon Acoustic Oscillations (BAO). This article provides some details on why Dark Energy is in no danger of being called in question: https://www.quantamagazine.org/no-dark-energy-no-chance-cosm...

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

#119

Post by MiroF »

njarboe wrote: post #74
MiroF wrote: post #60

Earlier quoted context omitted.

No - this article aside, most of the evidence suggests that this is matter that is actually there, not just an error term that we have added to our models.

This article is about dark energy, not dark matter. IANAC, but I think the evidence for the existence of dark matter is stronger than dark energy.

Yes, but the comment I'm replying to mentions dark matter.

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

#120

Post by [deleted] »

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?

[deleted]
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