"Observations indicate that the universe is expanding at an ever increasing rate. It will expand forever, getting emptier and darker." -Stephen Hawking
Today's Ask Ethan comes to us via our question/suggestion box from reader MIUFish, who asks:
I read something recently about some people who were doing work looking at the possibility that the mass of things has been decreasing, as an alternate explanation - or, perhaps, interpretation - to some of the questions regarding the expansion of the universe and so on.
Is there any seriousness to this? Do you know anything about it?
Here's what MIUFish is talking about.
For every galaxy we see in the Universe, we can measure how the light coming from it is shifted. Galaxies that appear to be moving towards us have their spectral lines -- that is, lines absorbed from or emitted by neutral atoms -- shifted. The amount of the shift is in direct proportion to a combination of:
- How quickly the object is moving towards us (for blueshifts) or away from us (for redshifts), in addition to
- How much the spacetime fabric of the Universe has expanded (for redshifts) or contracted (for blueshifts) from the time the light was emitted to the time it arrives at our eyes.
Combine both of those two things, and that accounts for the observed red-(and blue-)shifts of all the galaxies ever observed.
For galaxies that are very far away, the first part -- how quickly they move -- is negligible compared to the very large expansion of spacetime. That light has been traveling for billions of years, and so by measuring how that light redshifts for galaxies at different distances, we can reconstruct exactly how the Universe has expanded over its history.
At least, that's how it works if you accept General Relativity as the laws that govern our Universe, and conclude that the Big Bang describes our cosmology based on the evidence.
But that's not the only possibility, and recently, one proposed alternative has garnered some attention.
You see, instead of an expanding Universe stretching the wavelengths of photons, we could instead tweak the masses of the particles in the Universe, gradually, over time, so that light emitted a long time ago would be redder because the quantum physics underlying atomic transitions was different.
The idea comes from Christof Wetterich (and you can read his paper here), one of the rare people who's had a speculative idea in the past that was so intriguing I highlighted it for you on this blog. This idea might seem counterintuitive, but it's really incredibly simple. Think about Newtonian gravity for a minute, if you will.
Imagine you've only got two masses in the Universe, they're getting farther apart, and the only thing you can measure is the force between them.
So what do you see? As r goes up, the force goes down, and it goes down like r -2.
But could you be sure that r was going up, and not that G was (or the two ms were) going down? No, not if the force was the only thing you could measure.
And so it goes with the galaxies in our Universe.
We can measure only a few things about these distant galaxies, and the rest we have to infer. Because our experiences (and experiments) with spacetime and with masses tell us that the mass of particles doesn't change but spacetime does expand, contract and otherwise curve, we assume that's how the Universe works on scales where we can't do experiments.
But Wetterich's idea could work, too. But here's what isn't being reported: it comes at a cost.
You see, in an expanding Universe governed by General Relativity, there's a very powerful prediction that comes out: the expansion rate of the Universe at all times is determined by a combination of the curvature and energy density of the Universe. All the stuff in the Universe tells us, at all times, how the Universe has expanded, and therefore how objects should be redshifted.
So in our Universe, we observe that galaxies at different distances have different redshifts in a particular manner, and that tells us what the Universe is made out of.
We can then reconstruct exactly what we know to be in the Universe at all times, make predictions as to how the Universe did evolve and will evolve, and test them out.
We can compare these predictions with data sets that come from the Cosmic Microwave Background, the Large Scale Structure in the Universe, and Big Bang Nucleosynthesis, among others. As we've gone over, the agreement is astounding.
But if it isn't the expanding Universe that causes the redshifts, if instead the masses are changing, all of that predictive power disappears.
The fluctuations in the microwave background just happen to be this way because the mass changed in such a way to produce it, not because of the powerful underlying physics. The Universe is speeding up now not because there's an inherent energy (dark energy) to spacetime, but because the way that mass changes is contrived to produce that effect. And this is true for pretty much every such observation.
But you'd never have gotten this nuance from reading the news that came out about it.
This is the most common type of question I receive, and it goes something like,
Hey, I saw this story that made some outlandish claim. It's been getting a lot of attention and maybe even some news coverage, but is it true? Can you weigh in.
And every single time, it crushes me a little bit. Because people writing about it are supposed to provide nuance and context when a new find comes out, and to fact-check. You know, to take pride in what you do for a living. And there is some very, very good science writing and science journalism out there. But there's also this.
Really? Spacetime is just an illusion? No, and no one (reputable) is saying that it is.
What the actual research says is more like, "Hey, have you ever heard of quantum field theory (QFT)? That's a way -- okay, the way -- of calculating how the particles and fields in the Universe interact, and how they produce measurable things like cross-sections and scattering amplitudes. But there's a limit to what you can do with it."
"Well, there's a new mathematical technique that may be promising for calculating some of the cross-sections and scattering amplitudes we can't calculate with QFT. It's based in geometry, and it's just mathematics right now (as in, we can't yet do these calculations for the particles and fields that describe our Universe), but this is potentially very interesting!"
But it gets worse.
Yes, there was a story released this week about some theoretical work that postulates our three-dimensional Universe originated from a higher-dimensional Universe. An idea, by the way, that goes back to at least 1980!
But I assure you, wherever our Universe came from, the Big Bang is still correct, and you'd hope a science writer would know that!
Let me summarize: some incredibly speculative research that did not pass peer review and wound up in the sham-science Journal of Cosmology wound up hitting the front page of many newspapers making an outlandish claim with completely insufficient supporting evidence.
I don't know why some people have so little integrity when it comes to their own work. Is it churnalism? Is the time it takes to do a decent job too much for the amount you're paid?
It makes me incredibly sad every time I see a story like this, because I feel that the very people who are supposed to be assisting the public's understanding of science are behaving in a way that actively undermines it. Where is the fact-checking? Where is the editor to step in and say, "this isn't newsworthy." When did it become acceptable to fail to provide the correct context, and instead to just write the most sensationalist headline, accompanied by an article devoid of substance?
It's yellow journalism, plain-and-simple.
I wish it didn't exist. I wish it weren't everywhere. And I wish everyone involved in science communication behaved more ethically, like there was this inherent value in getting the science right. Like it was important to be careful, to get the facts right, to educate people about what's real, and to do the research to make sure you're getting it right when you talk about scientific truths.
Those last three articles (except the satire) that I screenshotted for you were all from this week, and this wasn't really an atypical week. Playing whack-a-mole like this would be a full-time job, and it would be a losing effort.
So although I'll take the occasional bait when something really raises my hackles, I'll stick to mostly writing about what we know, what's real, and telling you how we came to know it. With nuance, and facts, and evidence. Because even if everyone else doesn't care, I do, and I'm betting you do, too.
Keep fighting the good fight!
I truly appreciate your enthusiasm and your desire to educate.
It drives me bananas when I read something that shouldn't have made it past an editor (makes me wonder if science news websites even have editors worth their salt).
Awesome, thanks Ethan!
“Imagine that mass is actually shrinking” is exactly what I described to a colleague in our drafting department 25 years ago. She had no concept of either redshift or expansion, so I told her I would give her a description that she could visualize AND it would give her an idea of how theories work. She was good at geometry so I explained that if two objects were sitting still in space and were shrinking then they would appear to be moving apart to the also-shrinking observer. That would make an object twice as far away appear to be receding even faster. I told her the wavelengths of light that were emitted long ago would also seem to be larger over time and, hence, red-shifted. This would be happening to all particles in the universe simultaneously as a property of matter.
She understood and quickly visualized my illustration without me having to go into detail about the electromagnetic spectrum or launch into a lesson in cosmology. More importantly, I added that my description wasn’t really true, but in the absence of a better explanation you always work to test and confirm the theory that best appears to explain your observations, which is how science works.
Although I still don’t believe my explanation could have been right, my feeling about that is now shrinking.
For your proposed alternative to redshift due to expansion to be correct, our understanding of gravity would have to be fundamentally wrong. Take, for instance, an observation of a far off galaxy with a width of 100,000 light years. If matter was shrinking, the gravitational interaction of various stars in that galaxy would be unchanged. The galaxy itself would not shrink more than the radius of one star. For your alternative to be valid, distant galaxies would have to shrink substantially as time progresses. We know of no explanation of gravity to allow this to be the case, therefore, we can rule out this alternative explanation.
Well, I didn't propose it to my co-worker as a real possibility. I just used it to help her quickly visualize what was happening and I used my explanation to show how theories are proposed that can describe a phenomenon, but may not be correct and therefore must be tested. She got it.
There should be an online system that allows scientists around the world to have there say and debunk the latest stories on science. Just one place that the normal public can go to and see what's real.
Yes, there are many sites, like this one, that debunk the odd story, but they are not well known by non science types.
I imagine a scenario where all the main science stories are added to this service, then the scientists around the world can pick and choose which of those stories to debunk/verify. This way we'd be able to see which stories hadn't been dealt with.
You could have a rudimentary peer review system.
I'd love to see a site like that.
"Is the time it takes to do a decent job too much for the amount you’re paid?" For a non-physicist newspaper journalist, probably. As a layman w/above-average understanding (much of it from reading your excellent blog, btw...thanks for doing it!) and decent writing skills, I can imagine it being difficult to produce a nuanced summary of a development in advanced physics on deadline. Hanlon's Razor and all that.
I very often see redshift-pictures like the 3rd one.
If you take a ruler and measure the distance of any two lines and compare it to the related lines in any other stripe, you see they are equal.
As far as I know there is no wavelength-shift. Instead the lines' distances should compress from the high-z downto the laboratory stripe.
Am I right? Shouldn't we finally produce a correct picture and replace them at least here and in Wikipedia?
You have to understand: it's all about page clicks. Every web site is trying to increase it's number of page clicks (the more page clicks, the more revenue). Now the more spectacular the headline, the more people will click on it. Web sites have an economic motive to describe any story in the most sensational manner possible. You just have to follow the rule: ignore the headline, and read the story for the facts.
no, the image is correct, because the absorption lines of elements are same. It's the wavelength/frequency that's shifted.
Hydrogen will absorb the light of certain frequency and so will i.e. iron... thus the "distance" of them in the spectra remains the same... the whole spectra shifts. Imagine absorption lines staying fixed and spectra moving left and right.
@8 Schwar is exactly correct, and I was just coming here to report it myself. That figure does NOT show the redshift phenomenon correctly. The wavelength of each line is shifted by the same multiplicative factor, not the same additive factor:
lamba_new = (1 + z)*(lambda_old)
So, imagine two lines which have rest wavelengths 300 and 400 nm. At rest, they are separated by 100 nm. At a redshift of 1, their wavelengths are now 600 and 800 nm, which are separated by 200 nm: a larger difference.
Creating a proper picture takes much more work than simply shifting an image (applying an additive offset). I agree with Schwar -- someone ought to do it so that we can all use a proper figure.
"So, imagine two lines which have rest wavelengths 300 and 400 nm. At rest, they are separated by 100 nm. At a redshift of 1, their wavelengths are now 600 and 800 nm, which are separated by 200 nm: a larger difference."
yes, you are right. My bad. Sorry Schwar/Michael.
" I can imagine it being difficult to produce a nuanced summary of a development in advanced physics on deadline"
Add in that getting the correct nuanced answer will likely anger an important contributing advertiser and therefore the editor in chief, and you see the problem with any genuinely attentive journalist.
(it's much the same as political appointments or police: doing a good and conscientious job gains you all the responsibilities of power and none of the benefits. And lots of problems from those doing the opposite, who not only get the benefits of power, refuse to accept the responsibilities of power too, but also get more notice and therefore promotion. Given that, the good ones are worn down and leave and the bad ones stick around for the gravy.)
After Schwar and Michael pointing out there aren't correct images, with it being sunday and having nothing better to do.. here it is.
If there should be any improvement/corrections, please say so.. after that.. anyone can use it..
Re. amplituhedrons: I ran across this in the popular press, but there was a link to simonsfoundation.org, which seemed like a reasonable source. What I got from the Simons Foundation article was:
Radical simplification of calculations for particle interactions, reducing hundreds of pages of Feynman diagrams to a single page of geometry and a few equations that could be done by hand. (This by itself is good cause for excitement.)
And the implications I see in that are:
1) This may make a piece of quantum physics accessible to high school kids: "Now you can calculate by hand, something that previously required a supercomputer." Anything that makes basic science more accessible in the educational system is obviously good.
2) This may extend the range of effectiveness of our computer resources by a degree that's comparable to the degree of compression of the calculations. To be a bit hyperbolic about it, if we can go from 500 pages of Feynman diagrams to 1 page of geometry with a few equations, that should be roughly equivalent to extending the capacity of computing resources by a factor of 500. Radical simplification of calculations will enable computer simulations of phenomena that are presently too complex to calculate.
3) No, spacetime didn't just go away, that's silly media stuff.
Then I checked with a friend who has physics credentials. He said that from his quick glance at some press releases and suchlike, he thinks this is still at the level of a "toy model" that only works up to 4 dimensions at present, and more work will be needed to extend it to the point where it can be used regularly.
None the less, it's still a pleasant bit of news.
As far as the item about decreasing mass is concerned, I took that with a large dose of skepticism along the lines of "right now this is pure speculation and not close to being a theory that generates testable hypotheses." Many are the wild ideas, few are the ones that generate falsifiable predictions.
As for the media and its sensationalizing, emotionalizing, and so on, I suppose if it gets people interested in the subject matter, that's better than nothing.
(Disclaimer: I think I have the flu or something right now, and I'm pretty badly brain-mushed, which is offered as an excuse in case any of the preceding is either pure crap or poorly stated.)
@Sinisa Lazarek #14:
Wonderful: with linear scale with wavelength values added this would be perfect :-).
By the way: How did you generate that?
Will/Can you place that into Wikipedia redshift page?
Aye, G, I'd look at this as more like the FFT algorithms that noted how the fourier transforms could be simplified and get precisely the same answer as the originally proposed form.
I'd put this, in physics terms, more like the idea of everything being "information" that can aid with some calculations, which a few people have sensationalised into being "EVERYTHING is *merely* information, just like we're in ***THE MATRIX***!!!".
Thanks for input. Will put a scale under wavelength, and will try to match the absorption lines to actual values from 1+z=lambda observed / lambda emited
Sure, can put it on wiki. Haven't uploaded anything on wiki yet, will see what's the procedure.
As for software.. just photoshop/ilustrator
Very nice! I've seen those images everywhere, and just never thought about whether they were actually representing the equation correctly until SCHWAR_A mentioned it.
There's a few typos in that image Sinisa. It should be "Laboratory", "Distant", and "Wavelength".
Thanks for an important correction. I also always thought that the pattern of absorbtion bands was simply shifted (why else would they call it a 'red shift'? Are they trying to pull the wool over my eyes?)
It's all about $$; draw in readers and stimulate advertising to grow the bottom line. That is the fundamental problem.