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Study suggests that the Universe's expansion 'is now slowing, not speeding up'
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- Title
- Universe's expansion 'is now slowing, not speeding up': Evidence mounts that dark energy weakens over time
- Word count
- 1000 words
This feels like a pretty big deal. Is this a pretty big deal?
I hate precisely measuring things.
As an adult reading science news it feels like the best discoveries in physics and astronomy come down to new ways to measure things and increasing precision by finding weird stuff like this article mentions. One one hand I find it really interesting how they manage to do this stuff, on the other hand it makes me so glad I didn't end up doing stuff like that as a job because I would absolutely hate it so much. Props to the people who make a career out of it.
Don't go into metrology.
Or woodworking... ask me how I know.
I've heard you only need to measure once, right? You can always cut twice if you need to.
I make jewellery, and regularly work to tenths or sometimes hundreths of a mm accuracy and before any machinists come along and have Opinions about that, I do so almost exclusively using hand tools.
I fix pianos, and while I do sometimes measure with a micrometer, I'm always fascinated by watch repair and jewelers. Those tools are so darn tiny!
Even when I measure 3 times I still manage to fuck it up half the time
This is part (only part, admittedly) of the reason I am so mediocre at woodworking and sewing. An 1/8 of an inch here a 1/4 of an inch there. "It doesn't matter." But of course you do that enough and all of a sudden everything looks kinda wonky.
Do you happen to like cooking by chance? That feels like a place where that mindset works well.
This comic sums up my approach to cooking.
Do you have 9.5 fingers?
Can't remember why I hold this opinion but I suspect it's non linear and inherently tied to dark energy and the quantum foam that is the "vacuum". My money, for what it's worth, is we're probably inside of a black hole, dark energy and expansion happen as it consumes matter, contraction as it expels it.
Ahh nix that, we're not in a black hole but expansion and contraction appear nonlinear which completely changes the standard model of physics.
I am a cosmologist and want to weigh in on this. This is not the opening salvo in this argument — this same group at Yonsei has been making this claim for a while. I do not believe it holds up to scrutiny, and my impression is that the rest of the cosmology community working on supernovae agrees. These measurements are really difficult to get right, and a vast and incremental community effort has developed a robust understanding of possible systematics and errors over the last 20 years.
This group uses a small and non-representative set of supernovae, some of which have not even been confirmed to be type Ia supernovae (which is necessary for this type of analysis). Furthermore, they are relying on old measurements from ~2010 that are essentially obsolete. Papers like this are useful and can sometimes develop into serious challenges to the standard model of cosmology, but most of the time they serve to strengthen it by identifying possible systematic errors. Happy to answer questions about this, but in short, I would not go updating your understanding of what the cosmology community agrees on based on this.
This isn't an example of bad science, but it is an example of science media amplifying the conclusion of a single paper, without providing the appropriate context from others in the community.
Note: I also took the liberty to edit the title of this post to better reflect this uncertainty. I hope I am not stepping on anyone's toes by doing so.
(@okiyama @wervenyt @mild_takes — just tagging as you might find this perspective interesting given the comments left here).
Thanks so much, you never know what sorts of expertise will pop up online!
What's your area of study if I may ask?
My area of expertise is the cosmic microwave background, but I regularly interact with people doing SN or baryon acoustic oscillation stuff, and use both data sets as required.
Appreciate the background!
I'm no physicist, but I am glad about this update to the models. The idea that spacetime was apparently constantly accelerating in volume is the kind of notion that undermines cosmic meaning comparable to god's non/existence, if you ask me. It's bad enough we (existences) will all eventually freeze out to stasis, and the idea of crunch/bang cycles is daunting, but that's far more compatible with our minimally-intuitive notions of energy and time than some kind of self-consumption that also approaches infinity.
Yesterday I read about this and a wall of fire at the edge of our heliosphere, detected a by both voyagers.
The reporting on both seemed a little scant even after having searched for alternative articles.
As you say, this discovery seems very significant, but I'd expect more coverage were that the case?
Regarding the wall of fire, I understand that there are few particles out there, which is why the probes survived the up to 50,000k temps, but I'm not sure i fully understood why these particles so far out were getting so warm? Anyone have a better understanding?
I haven't read any literature but my conjecture is it's due to the the interaction between the heliosphere and interstellar space in the same way as our earth's magnetic field interacts with solar wind/particles.
I’m not any more well read on the topic, but that makes sense to me.
An interesting implication of all of this is that any craft intended to take humans beyond the confines of the solar system may need significantly beefier shielding than even crafts intended for indefinite habitation that never leave it. So you might have two classes of crewed, permanently spaceborne crafts: solar and interstellar.
It might be a good idea to send out a few probes designed specifically for gathering information on the environment outside of the heliosphere. Not that we’re going to need that data any time soon, but the tail on such missions is so long that it’s better to launch them sooner than later.
I looked into it, and it seems like this (the "firewall" thing) was first published in 2019. It's not a new discovery. I couldn't find any recent news published by NASA about this, but plenty from 2019. What appears to have happened is that someone, somewhere rediscovered this piece of news from 2019, posted about it as if it were a new discovery, and then that went somewhat viral and got amplified by numerous websites repeating the same information. You probably couldn't find anything that isn't just a rehash of the same information because they're all copying each other, copying old news from six years ago.
Here's the original paper: https://www.nature.com/articles/s41550-019-0929-2
NASA's own website has nothing I could find from this year relating to this particular discovery. The crossings of the Voyagers into interstellar space occurred in 2012 and 2018, respectively. In fact, the Voyager 2 plasma measurement instrument was recently turned off to conserve the dwindling power supply, and Voyager 1's similar instrument was turned off years ago. So it appears neither probe is actively collecting the sort of information that these studies were based on anymore.
As for the reasons why these particles get so hot so far out: my layman's understanding is that it's theorized to be one or both of a) compression due to the meeting of the solar wind and the interstellar medium, and b) magnetic reconnection. When separate magnetic field lines meet up, they can convert magnetic energy into kinetic energy, heating up particles - it happens in the Earth's magnetosphere as well, and can even lead to a temporary reversal of the local solar wind, sending the particles back towards the Sun!
...why is my first thought "ah, so maybe we do already live in hell"?
Had a chat with Gemini to get clarification on this. It is a fucking bombshell!
Basically, in 1989 astronomers used special supernova that were assumed to be "constant candles" in other words, they emit a constant amount of light (or other stuff em waves). So when they looked further back in time and found them dimmer than ones newer in time, they concluded the universe was expanding.
For this, the 2011 nobel prize was awarded. What this paper is saying is that the assumption of "constant candles" was inaccurate. It's actually that the younger one of these supernovae are, the dimmer they are. When you assume that, expansion goes away and we find a non linear expansion and contraction field across the universe.
This is fucking bonkers huge. It's published in a very respected journal, and it's essentially saying "forget the lambda" (cosmological constant) of the standard lambda cold dark matter model. Instead, it looks like something called quintessence is reality.
Holy shit!
Sorry for the slop but this is worded well. "In short, if this paper is correct, the 2011 Nobel Prize was awarded for misinterpreting a systematic bias, and our entire understanding of the universe's current state is wrong." -Google Gemini 11/7/2025