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'More than a hint' that dark energy isn't what astronomers thought

nytimes.com

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Re: 'More than a hint' that dark energy isn't what astronomers thought

#71

Post by doodlebugging »

api wrote: post #53
thom wrote: post #27

Were I to have a religion, it would be following the poor, stressed programmer tasked with creating (on some insane deadline) the universe we inhabit. To fix various performance bugs, he (I like to think he's called Colin) had to implement all sorts of hacky workarounds: lazy loading so some information is only calculated when it's observed, a maximum speed of information propagation to enable sharding, a system to i…

So the first lead coder was this Lucifer guy. Wrote the whole code for the physical universe layer in like days on Red Bull and maybe speed. Unfortunately he was shady and found to be embezzling from the company so he was fired. Only then did the team actually look at that code. Absolutely incomprehensible mess, and it looked like he left back doors in so he and his pals could manifest weird stuff in the universe and…

And then there's the kid Jesus who promises us relief from all the skullduggery coded into our existence if we will only agree to subscribe to his Salvation as a Service (SaaS) subscription model.

Re: 'More than a hint' that dark energy isn't what astronomers thought

#72

Post by karmakaze »

thom wrote: post #27

Were I to have a religion, it would be following the poor, stressed programmer tasked with creating (on some insane deadline) the universe we inhabit. To fix various performance bugs, he (I like to think he's called Colin) had to implement all sorts of hacky workarounds: lazy loading so some information is only calculated when it's observed, a maximum speed of information propagation to enable sharding, a system to i…

> a maximum speed

It's even hackier than that. Everything moves at c always, if not through space then through time or some combination.

Re: 'More than a hint' that dark energy isn't what astronomers thought

#73

Post by fedeb95 »

sigmoid10 wrote: post #18
fedeb95 wrote: post #17

An interesting part from a different article mentioned here in the comments: The results do not meet the so-called five-sigma threshold of statistical certainty that is the gold standard in physics for claiming a discovery. But many in the collaboration have shifted in recent months from a position of scepticism to confidently backing the finding. Source: https://www.theguardian.com/science/2025/mar/19/dark-energy-..…

If you combine it with other data it's from 2.8 to 4.2 sigma. Pretty strong and it has gone up since last year with more data. Nothing definite yet, but certainly intriguing.

yes, that was my point! Interesting that's "on the rise"

Re: 'More than a hint' that dark energy isn't what astronomers thought

#74

Post by indigoabstract »

function_seven wrote: post #47
indigoabstract wrote: post #34

Earlier quoted context omitted.

Call it professional bias, but I like to think about it as a big VM. If for some reason, things go awry, the (said) programmer will hit the pause button, then diligently go to the last valid snapshot, fix the bug and then get things going again. If this isn't desired, fixing the current mess is also an option. The time required for fixing bugs isn't really an issue in this case, he can take as long as he likes.

VMs are too resource hungry. No, the many-worlds interpretation shows that our universes are merely containers with copy-on-write behavior :)

Yeah, could be a giant LMDB, but that's implementation detail :)

I imagine there's some serious optimization involved to make it all fit in memory.

Re: 'More than a hint' that dark energy isn't what astronomers thought

#76

Post by beeforpork »

Timwi wrote: post #39
beeforpork wrote: post #31

Earlier quoted context omitted.

Why would you be concerned? Earth and everything living on it will be long dead by then, and probably gone and swallowed by the sun. And maybe the Sun dies before that, too. So what would be particularly concerning about merging of our galaxy with another one?

> Earth and everything living on it will be long dead by then How do you know? It's not far fetched to think that, if humans don't go extinct in the meantime, they will continue to find ways to shape the world according to their needs. By the time the Sun goes red giant, we may well have found a way to alter the orbit of Earth. By the time the Sun goes supernova, we may be able to move to another star. Who knows. But…

> How do you know?

Hmm, yes, I don't. I just honestly don't get why that galaxy collision is concerning. What's the concern? For whom? Four billion years is very, very long compared to humankind's evolutional history. Homo may be 2 My old, that's 1% of the time it takes the sun to rotate a single time around the center of the galaxy. Sol completed already ~20 rotations since it exists. Homo's whole history is 1/2000th the time ntil Andromeda will arrive. So, what's the concern? Humankind will not exist for many, many hundreds of millions of years.

> It's not far fetched to think that, they will continue to find ways to shape the world according to their needs.

Humans fixing Earth's and Humanity's problems is totally out of character. I did not even consider it.

Earth's death is certain. Sun's death is certain. Galaxy collision might even go unnoticed for quite a while -- it's not like millions of stars would crash into each other -- very unlikely. It's more like a reshaping, but what's concerning about that? More supernovas around us? Yeah, maybe.

But why is it more concerning that any other demise? It is an interesting question, I think, about perceived danger.

Re: 'More than a hint' that dark energy isn't what astronomers thought

#77

Post by gadders »

mr_mitm wrote: post #21
sigmoid10 wrote: post #19

Earlier quoted context omitted.

Don't confuse accelerated expansion with the cosmological constant. Accelerated expansion's origin is most likely the cosmological constant aka dark energy, but they are not the same thing. The cosmological constant itself arises naturally (kind of how an integration constant emerges for indefinite integrals) when you derive the field equations of general relativity. It is basically a geometric degree of freedom inhe…

I'm not sure where you got that I'm confusing something. For what's it worth, my name is in the author list of that paper.

This is nearly as good a comment as cperciva winning the Putnam.

Re: 'More than a hint' that dark energy isn't what astronomers thought

#78

Post by antognini »

fedeb95 wrote: post #17

An interesting part from a different article mentioned here in the comments: The results do not meet the so-called five-sigma threshold of statistical certainty that is the gold standard in physics for claiming a discovery. But many in the collaboration have shifted in recent months from a position of scepticism to confidently backing the finding. Source: https://www.theguardian.com/science/2025/mar/19/dark-energy-..…

As a former astronomer, one thing to highlight here is that statistical uncertainties aren't usually all that important in assessing how likely a result in astronomy is to be true. The main issue you grapple with in the field are your systematic uncertainties. When you report your uncertainty, it always is an uncertainty in the context of some model. However, if certain assumptions that your models have made are wrong, you will have underestimated your true uncertainty. Unfortunately, systematic uncertainties can't be reduced just by getting more data --- you have to somehow verify that the different assumptions your model has made are correct.

Astronomers spend a lot of time arguing with each other about whether they have properly incorporated all their systematic uncertainties. For measurements of dark energy this very quickly gets you into the weeds of Type Ia supernova physics (which is made more difficult because we don't know for certain what Type Ia supernovae are), stellar physics in Cepheids, the effect of metallicity, selection bias effects, and on and on.

Re: 'More than a hint' that dark energy isn't what astronomers thought

#79

Post by mr_mitm »

gadders wrote: post #77
mr_mitm wrote: post #21

Earlier quoted context omitted.

I'm not sure where you got that I'm confusing something. For what's it worth, my name is in the author list of that paper.

This is nearly as good a comment as cperciva winning the Putnam.

I wouldn't want to overstate it either, since I was just a lowly and IMHO mediocre PhD student at the time and my contribution to the paper was minor. Nevertheless, I believe I understand the relationship between the cosmological constant and dark energy just fine.
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