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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

#21

Post by mr_mitm »

sigmoid10 wrote: post #19
mr_mitm wrote: post #4

I know it makes for a "better" headline, but don't be mislead by it thinking Astronomers actually thought dark energy was a cosmological constant, period. Read section 1.1 of the Euclid review paper from 2016 to get an impression straight from the horses mouth. > Why then is the cosmological constant not the end of the story as far as cosmic acceleration is concerned? There are at least three reasons. https://arxiv.o…

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.

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

#22

Post by sigmoid10 »

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.

>where you got that I'm confusing something

From the idea that the constant that equates to dark energy in the stress energy tensor is not commonly thought to be a constant. People didn't call it that way as some joke. This isn't even up to astronomers, this is something that mathematicians will tell you. And it could potentially cause some real trouble not just for our models of the universe but for the basic mathematics of relativity if it is changing. Motivating that alone will we hard, not to speak of the consequences down the line.

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

#23

Post by [deleted] »

sigmoid10 wrote: post #22
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.

>where you got that I'm confusing something From the idea that the constant that equates to dark energy in the stress energy tensor is not commonly thought to be a constant. People didn't call it that way as some joke. This isn't even up to astronomers, this is something that mathematicians will tell you. And it could potentially cause some real trouble not just for our models of the universe but for the basic mathem…

[deleted]

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

#24

Post by rcxdude »

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-..…

That's basically a particle physics threshold, because in particle physics you tend to do many, many experiments (usually you're doing thousands a second). It's hard to get something that certain in astronomy, where you've only got one universe to observe.

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

#26

Post by gpderetta »

rcxdude wrote: post #24
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-..…

That's basically a particle physics threshold, because in particle physics you tend to do many, many experiments (usually you're doing thousands a second). It's hard to get something that certain in astronomy, where you've only got one universe to observe.

It is also an informed threshold. FTL neutrinos where, IIRC, above 6 sigma and nobody believed it was true, while there were strong rumors that Higs had been found well before it hit 5 sigmas.

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

#27

Post by thom »

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 insert new nodes in the linked list of spacetime, pushing galaxies apart and ensuring the complex timelines of intelligent species never have to snap together and run on a single instance. The work is constant and unrewarding, but I am thankful to Colin for his work, however mysterious it might seem to us.

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

#29

Post by petargyurov »

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…

[BUG #3451249]

Unlimited resource drain caused by conscious blobs of particles (a.k.a humans) invoking recursive thought patterns over their own existence.

Workaround: ponder function can return a feeling of existential dread accompanied by increased weights for headache "sensation", causing blob to terminate process.

Estimate: M

Label: Backend

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

#30

Post by flopunctro »

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…

This comment reminded me, with a smile, of Scott Alexander's Unsong: https://www.astralcodexten.com/p/unsong-available-in-paperba...
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