Evidence that the key assumption made in discovery of dark energy is in error • Hacker News Board

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

#201

Post by roywiggins » Tue, Jan 07, 2020, 2:25 PM UTC

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?

You can't make an electron bigger, so it can't be stretched out. Other point particles are the same. The forces that hold physical stuff together are much more powerful than the gentle expansion of space, so we don't see people and planets dissolving.

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

#202

Post by cthalupa » Tue, Jan 07, 2020, 2:31 PM UTC

ltbarcly3 wrote: post #145

cthalupa wrote: post #131

Earlier quoted context omitted.

This is a false dichotomy. We have known energy is not (always) conserved since long before we began discussing dark energy. This is such a misunderstood topic vis a vis dark energy that Discovery specifically has an article on it: https://www.discovermagazine.com/the-sciences/energy-is-not-...

Nope. We have no actual evidence of a violation of the conservation of energy. What has happened here is that astrophysicists got way out on a branch. They were quite excited and came up with a theory that seemed to explain why there appeared to be increasing redshift with distance, and later that theory was shown to violate conservation of energy. Doubling down, they waved their hands and said that conservation of e…

>Doubling down, they waved their hands and said that conservation of energy must not hold at 'cosmological scales'

Energy not being conserved has been experimentally verified, as noted in the article you were linked.

This isn't a controversial topic, nor is it one where scientists have proposed it as a potential solution for a problem they can't conclusively solve. GR predicted it, we've verified it.

>without any evidence to make such a claim.

Light redshifts. The energy of a photon is in its wavelength. Light redshifting fundamentally means that energy isn't being conserved.

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

#203

Post by magicalhippo » Tue, Jan 07, 2020, 2:35 PM UTC

osbertlancaster wrote: post #154

exabrial wrote: post #115

Can someone eli5 why if space itself is expanding, how can an observer detect that if they too are expanding at the same rate?

As I understand it: We are not expanding. Size of e.g. a hydrogen atom is not changing.

And we are not expanding because other forces are stronger at short range. Similar to how the electroweak force is preventing you from falling through your chair, even though the gravity of the entire earth is pulling you.

Dark energy, as we thought before this paper at least, would overcome gravity only on the grandest scales, between galaxies.

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

#204

Post by mannykannot » Tue, Jan 07, 2020, 2:46 PM UTC

When dark energy was first accepted, it seemed to me, as an outsider, that it happened very quickly, without, apparently, any time as a possibly-contentious, 'could this be so?' hypothesis in the way that, for example, dark matter did (and, to some extent, still is.) That surprised me because, up to that point, there seemed to be a problem with the cosmological distance ladder, with different methods getting different results, and with there being stars that seemed older than the universe supposedly was.

In comparison, when superluminal neutrinos were tentatively announced a few years ago, there was a lot of justified skepticism about there being experimental error (admittedly, overthrowing special relativity is an even more extraordinary claim than dark energy.)

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

#205

Post by mirimir » Tue, Jan 07, 2020, 2:49 PM UTC

sanxiyn wrote: post #116

kiliantics wrote: post #52

Earlier quoted context omitted.

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.

Yeah. In my reading, it almost characterized SNIa as fact.

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

#206

Post by [deleted] » Tue, Jan 07, 2020, 2:52 PM UTC

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?

[deleted]

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

#207

Post by Pigo » Tue, Jan 07, 2020, 2:58 PM UTC

rs23296008n1 wrote: post #75

Good. Science is meant to be a honest search for facts: data, knowledge and wisdom. Being wrong is a feature. "I don't know" is an acceptable starting point with no shame attached. Being certain means a mountain of data to back it up. Being allowed to be wrong is a requirement. Anyone saying a scientist can't ever be wrong is likely placing oddball limits on progress that will only damage and limit the future[1]. How…

This is one of the most important things I learned from Star Trek. The beginning of wisdom is "I don't know".

https://www.youtube.com/watch?v=ZcV25N37-C4

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

#208

Post by RookyNumbas » Tue, Jan 07, 2020, 3:05 PM UTC

guygurari wrote: post #125

It is hard to overstate how important the resolution of this question is to physics, and in particular to theoretical physics. The “cosmological constant problem”, that is the problem explaining the cosmological acceleration (if it exists), is arguably the most important and hardest question in high energy theoretical physics. Many theoreticians have spent significant effort studying this question, working under the…

Do you know if these measurements were possible in the past, and no one thought of doing them? Or are they only recently possible, enabled by new technology?

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

#209

Post by Hoagy » Tue, Jan 07, 2020, 3:20 PM UTC

Late to the party but does anybody know if this is connected to the findings a few weeks ago that this Quanta article is replying to? (https://www.quantamagazine.org/no-dark-energy-no-chance-cosm...)

I know they are proposing different mechanisms for the error in calculation but it gives a sense of a 'moment' shifting against dark energy. Coincidence?

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

#210

Post by Certhas » Tue, Jan 07, 2020, 3:34 PM UTC

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?

I never said it is only expanding outside. Also moving relative to space is not nonsense. Motion is not just relative to other objects in space. This what Newton's bucket thought experiment showed.

Edit: the pearl is made from around bound by electric forces, so you can repeat the same argument for inside the pearl. You can repeat it all the way down until you have to admit that the approximations inherent in the concepts useful to describe the world at distances from nano meters to mega parsec eventually break down.