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Comment by sahil50 | Hacker News Reader

What if the cause of the cosmological redshift is continuous photon decay? Not galactic recession, but photon hubbling, or tired light?

www.bigcircusmodel.org

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I'm not smart enough to understand most of cosmology or astrophysics, but the way that site is presented makes me feel that it is quackery. The fact that there are only a handful of sentences makes me feel it is trying to appeal to people with low science literacy.

I'm not trying to discount it, but that home page with 12 photos of various galaxies, and then 4 blurbs of text, then a full screen YouTube video just feels "unscientific".

Not supported by data. There is plenty observational evidence that the redshift is due to cosmic expansion, e.g. galaxy surface brightness evolution, CMB, time dilation, the list goes on.

The website you link poses a number of unsubstantiated claims without any answer to the numerous problems it raises.

Then he links to this hilarious notebook; https://colab.research.google.com/drive/1K1qoUFvqZp1fWbpcKJW...

I don't mean to sound rude but this doesn't look like the work of someone who has spend any considerable amount of time actually studying the Universe.

What if I could rebut all the rebuttals?

- The analysis of supernovae light curves is calibrated in a way that presumes galactic recession. More detail here https://arxiv.org/abs/1711.11237.

- The 2.7 K cosmic background radiation is consistent with non-expansionary, non-big-bang models. Cosmic temperature was predicted 50 years before Penzias and Wilson. https://en.wikipedia.org/wiki/Cosmic_microwave_background#Ti...

- The mechanism for photon energy loss (can we call this "photon hubbling"?) is not scattering by free electrons. I speculate it is the cost of traveling, of a photon forging its way through spacetime. E_t / E_0 = e^(-Ht). In the act of moving, the photon is warping spacetime. It doesn't travel for free.

And, what's your view on Dirac's large numbers hypothesis?

It’s intuitively a reach, because photons don’t move.

From a four dimensional perspective—which is the correct one, let’s not forget—the distance between a photon’s emission and absorption event is always zero.

“Tired light” would require the photon to spontaneously lose energy based on the Manhattan distance of the path it takes. That distance can be arbitrarily large, sure—a photon can cover the entire universe before absorption—but it isn’t the path the photon actually takes, so it’s difficult to imagine why it would matter.

> From a four dimensional perspective—which is the correct one, let’s not forget—the distance between a photon’s emission and absorption event is always zero.

That would require the emission and absorption events location in the space to be the same would it not? Or do you mean that a photon does not experience time, so relative to the photon it simply travel instantaneously from emitting coordinate to absorption coordinate?

> That would require the emission and absorption events location in the space to be the same would it not?

I think they're referring to the distance in Minkowski space,[0] where the time component and space component cancel out for light.

[0]: https://en.m.wikipedia.org/wiki/Spacetime#Spacetime_interval

The distance metric for flat spacetime is given by:

   ds^2 = dx^2 + dy^s + dz^2 - cdt^2

For a particle traveling at the speed of light, this gives ds=0.

Where does your claim that photons don't move come from? Very simply, the Sun is 8 minutes from the Earth. The photon is most definitely moving from the Sun to the Earth.

They are talking about "intervals" in 3+1 dimensional space time. To explain it rigorously, one needs to define a few terms like "metric" or "light cone". One defining property of the photon is that its space-time interval between any two events in its history is zero. You can think of it as the dual of the fact that a clock moving at the speed of light would be completely stopped.

Intervals are the square of the distance, so not quite, but… yes.

There’s a tendency to treat spacetime intervals as something abstract and possibly metaphysical, because we can’t see or touch them, and they work counterintuitively.

They’re actually the opposite. Our normal experience of 3D space is what is unphysical; the (square root of the) spacetime interval is simply distance, measured in meters. Or seconds, of course.

The literal, physical distance between an absorption and emission event is always zero. Reality is non-Euclidean. The Manhattan distance is larger than the actual distance, which is usually true anyway.

Well, I suspect I just spent a lot of words telling you something you already knew, so I’ll leave off with a book recommendation. Dichronauts, by Greg Egan.

Between that and the Clockwork Rocket trilogy, I don’t know a better way to inculcate an intuition for special relativity.

One is set in a 2+2 spacetime; the other in 4+0. The differences are instructive.

This made me laugh given that, actually, Greg Egan is by far my favorite author. But I also think you are going way too far by saying that our normal 3D space is what is unphysical. The fact that our everyday reality is the limit of a more interesting reality when some parameter becomes small, does not make it any less real, for any reasonable definition of "real".

Well, it's certainly consistent. And for the most part you're right; it's just light that gets hard to understand from this perspective.

Unfortunately photon behaviour is fairly important...

Briefly, from special relativity. As something approaches the speed of light, time slows down for it. At the speed of light (through vacuum) time stops, and in that reference frame there is no such thing as distance.

Thoughts on gravitational lensing point above? From the photon's point of view, it is experiencing changes through time and space.

That point misses (or rather ignores) the larger point. Ignoring special relativity because you think Einstein was "lost in the notation" is an extraordinary claim for which no extraordinary proof exists.

Never said that. I'm solid on speed of light as a max, gravitational lensing, gravitational redshift, and all the real world measurements that are in total sync with relativity.

The point is that I think claims like "distance doesn't exist" is the kind of thinking that comes from people lost in notation.

It's 8 minutes for an "external" observer. Physicists say the photon itself does not experience time or space.

The photon does experience change over time and space. Take gravitational lensing by the Sun. The photons that we see from behind the Sun, are definitely affected by the Sun. From the photon's point of view, it is experiencing changes through time and space. Thoughts?

Not from the photon's point of view. It is emitted and absorbed immediately. The distance traveled (in 4d spacetime) of a photon is always 0, no matter (pun intended) what's in between or what you observe.

I don't think it is true to say that "it is emitted and absorbed immediately", because there is a very real difference from a photon going from the Sun to the Earth, to a photon going from the Sun to Jupiter.

I know the theory the view you're saying comes from, and the weight it has in academia, but it always struck me as useless. And that whoever came up with it was lost in notation.

>because there is a very real difference from a photon going from the Sun to the Earth, to a photon going from the Sun to Jupiter.

Not from the photon's point of view. This is very crucial and it is not because of notation or maths. The real difference is from your point of view. I know it's counter-intuitive but that's different from being useless.

Sun->Earth or Sun->Jupiter is a small beer. It is the same for photons from the CMB being recorded. For them, they have been emitted and absorbed at the same instant and experienced no passage of time or distance traveled

"Sun->Earth or Sun->Jupiter is a small beer"? How do you mean? This is a real physical example with real physical consequences for example for how much dimmer the light is per area (by 1/r^2) and by how much redder it is (by 1/r).

What are the real physical consequences of thinking that the photon is "emitted and absorbed at the same instant"?

This idea has been around almost a hundred year. It is not supported by the evidence.

https://en.wikipedia.org/wiki/Tired_light

What if I could rebut all the rebuttals?

- The analysis of supernovae light curves is calibrated in a way that presumes galactic recession. More detail here https://arxiv.org/abs/1711.11237.

This would not give blackbody radiation, and is ruled out by observation.

http://www.astro.ucla.edu/~wright/tiredlit.htm

What if I could rebut all the rebuttals?

- The analysis of supernovae light curves is calibrated in a way that presumes galactic recession. More detail here https://arxiv.org/abs/1711.11237.

Please don’t repeat the same comment over and over, it comes off as spam even though that’s not what you intended.

This doesn’t even address this particular parent’s question. Better would be to make the comment once, where it is most appropriate, then give specific responses to other threads, perhaps linking to the one comment if it’s relevant.

The supernova light curve data is red shift vs. timescale of the light curve. This doesn't make any assumption about galactic recession. And it's incompatible with tired light models.

No, the CMBR is not consistent with non-expansionary models. Tired light may get the shape of the CMBR spectrum right, but it fails to get the intensity right unless there's an extreme coincidence that we just happen to be living at exactly the right moment.

This was all explained in the page you think you were rebutting, so please go re-read it, this time for comprehension.

I await your commentary on the SALT2 calibration mechanism. This is the point where bias is introduced. The supernovae light curve data was biased before any analysis made.

This doesn't appear anywhere in the link from the link I provided for the SN light curves.

https://arxiv.org/abs/astro-ph/0104382

Thanks for linking. So this paper is from 2001. Whereas SALT2 is from 2007. https://www.aanda.org/articles/aa/pdf/2007/16/aa6930-06.pdf

This 2001 paper uses a correction template that I think is a v1 of what SALT2 is. SALT2 probably is an "improvement" on this template, so I think by identifying a problem in SALT2, I have adequate (but not 100%) reason to think this template introduces the same bias.

The current work on SN cosmology is making subtle measurements to try to determine difficult to measure properties of the expansion of the universe, using SN at high red shift.

Tired light is easily killed without all that, using data available decades ago, at z < 1. And this doesn't require estimation of the absolute luminosity of the SN.

Why are you bringing up something else? Awaiting your commentary on the big 3 rebuttals of tired light, and the rebuttals of those rebuttals.

It's you bringing up something else. SALT2 is a red-herring.

Now that's false.

The point is that the data calibration mechanism introduces bias before any analysis has been made. The data is calibrated to assume galactic recession. That's the problem.

The point of SALT2 was better models for calculating the brightness of SN, so their distance could be calculated. This is necessary for detecting subtle changes in the expansion rate of the universe.

Killing tired light doesn't require any of this. What the paper I cited did was plot the redshift vs. the rise and fall times of the light curves. This doesn't depend at all on the overall brightness of the SN. There is no need to estimate this brightness. In tired light, the result curve will be flat; in the standard cosmology it will not be. And the observations were inconsistent with tired light at 10 standard deviations, killing the theory. The SALT2 stuff you're pointing to is indeed a total red herring.

I get the feeling you're just pretending to understand all this stuff you're pointing to, for some reason.

Considering all the redshift data we have, galactic recession does not fit. Rough calculations https://docs.google.com/spreadsheets/d/1HI61-pDIzzSItw48K0ga... Data from https://ned.ipac.caltech.edu/Library/Distances/

Crawford addresses what you're saying in this paper. https://arxiv.org/abs/1711.11237

Sorry for meta, but to downvoters: please don't downvote a what-if question that - well, questions an established theory in a casual conversation. A lot of interesting, disruptive things in science start with a question!

Without taking a position on downvoting - this is true for new interesting questions, at some point you have to move past ones already eliminated as reasonable possibilities.

OTOH, I think this position is relevant only from the perspective of new scientific inquiry — it’s worth asking questions that have already be asked when learning / acquiring knowledge! Sure, someone could find this information on Google, but misinformation too, so I think it’s worth asking in this sort of environment so we can all more deeply understand existing theory, etc.

While the comment says "What if", the site linked is more "All physics is wrong, this is how it is" and presents some model that has been disproven by evidence over and over. I think crank physics isn't worth discussing when presented in that fashion.

This seems very much like a disingenuous what-if - not a desire to actually seek an answer, but an attempt to convince people into believing what they do by posting a link to a very biased site.

Thank you

I'm not smart enough to know if that makes any sense at all. But it's a very intriguing idea. I'd never heard of it before.

If it were the case, photon decay would be measurable.

https://physicsworld.com/a/what-is-the-lifetime-of-a-photon/

E_measured / E_emitted = e^(-d / H'c)

e is 2.718... d is distance of travel H' is 13.83 billion years, the continuous decay rate

Rough calculations https://docs.google.com/spreadsheets/d/13aRdc1gZmsA3F-gKt5sK...

Data from https://ned.ipac.caltech.edu/Library/Distances/

Reminds me of Cyclic Conformal Cosmology theory (backed by Roger Penrose).

As far as I can tell, the CCC theory says that the big bang did happen but that the universe is cyclical. i.e. once the universe reaches 'heat death' another big bang happens.

Penrose's observations of evaporated black holes in the cosmic background radiation map are really interesting. This is a big reason to think there are structures older than 13.8 billion years.

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