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Physicists now question the fate of the Universe

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Re: Physicists now question the fate of the Universe

#41

Post by mr_mitm »

dotnet00 wrote: post #5

The premise comes off as a bit of a surprise to me. My understanding had always been that physicists have not reached any majority agreement on which of the outcomes was likely, precisely because of the lack of understanding of the exact nature of dark energy.

There is nothing to agree on. You make measurements, see what model fits best, and then ask the model what will happen as time goes to infinity.

And we did have a consensus: the standard model of cosmology. It fits the data best, that's how it became the standard model. Many cosmologists don't like the standard model, because it has some theoretical deficiencies. One example: The value of the dark energy density seems highly tuned. Its value is unnatural and there is no known mechanism that could produce such a finely tuned parameter. But what can you do if all observations agree with the standard model?

I've been in cosmology grad school ten years ago and would listen to a visiting scientist presenting a novel model that might explain the standard model's shortcomings practically once a week. There is no shortage of speculative models. And as I said, science doesn't work by finding an agreement. You devise experiments that can show that your model explains more than the standard model and let nature find the agreement for you. If there are a few stubborn scientists left that cling to ruled out ideas (Fred Hoyle comes to mind), experience shows that they will die out over time.

Euclid is one such experiment my group studied a lot, and it's finally collecting data. Hopefully it helps us find a better model than the standard model, and with all the news in the past few years, it's looking good.

Re: Physicists now question the fate of the Universe

#43

Post by mr_mitm »

tiborsaas wrote: post #18
fasteddie31003 wrote: post #10

This kind of research is non-falsifiable and I think it's just a waste of these scientists' talents. You will hear never-ending theories of the Big Bang, black holes, and the end of the universe because all this research is non-falsifiable and just people playing with math and coming up with different ideas that humans find interesting, but will not affect your quality of life at all. Science has to be falsifiable or…

I kinda agree about researching the end of the Universe, but the birth of the Universe and black holes a pretty relevant to modern day science. We don't have a theory of quantum gravity, we have a singularity at the big-bang, etc. Finding a theory of everything could unlock many new practical improvements. Falsifiability not only happens when you can disprove something with a physical experiment. You can't trigger an…

> I kinda agree about researching the end of the Universe,

It's a fallacy to believe that people are specifically researching the end of the Universe. We research models. The standard model for example is parameterized by six numbers. You measure those six numbers, put them in the model, and the model will tell you how old the universe is and what will happen in the far future.

If it turns out that different probes yield incompatible sets of values for those six numbers, for example probes from the early universe vs more current probes (e.g. the cosmic microwave background vs super novae data), then the model must be wrong. Then we might look for another model, perhaps one with seven parameters, where the additional parameter characterizes the evolution of dark energy, which assumed to be constant until now, and see if that fits better. And what do you know, that model might yield a different result for the age of the universe and its fate.

It's a consequence of fundamental research, not a primary goal in itself.

Re: Physicists now question the fate of the Universe

#45

Post by gilmore606 »

"What’s reality? I don’t know. When my bird was looking at my computer monitor I thought, ‘That bird has no idea what he’s looking at.’ And yet what does the bird do? Does he panic? No, he can’t really panic, he just does the best he can. Is he able to live in a world where he’s so ignorant? Well, he doesn’t really have a choice. The bird is okay even though he doesn’t understand the world. You’re that bird looking at the monitor, and you’re thinking to yourself, ‘I can figure this out.’ Maybe you have some bird ideas. Maybe that’s the best you can do."

-- Terry Davis

Re: Physicists now question the fate of the Universe

#47

Post by slowmovintarget »

mr_mitm wrote: post #41
dotnet00 wrote: post #5

The premise comes off as a bit of a surprise to me. My understanding had always been that physicists have not reached any majority agreement on which of the outcomes was likely, precisely because of the lack of understanding of the exact nature of dark energy.

There is nothing to agree on. You make measurements, see what model fits best, and then ask the model what will happen as time goes to infinity. And we did have a consensus: the standard model of cosmology. It fits the data best, that's how it became the standard model. Many cosmologists don't like the standard model, because it has some theoretical deficiencies. One example: The value of the dark energy density seem…

It seems wrong-headed that even the hint of a Creator requires turning theories into pretzels to remove that hint even when it's not proof.

The "problem" of fine-tuning isn't really a problem. Why that value? We just don't know yet. Maybe God set it. Maybe we're part of an infinitely large cosmos where our false vacuum has these parameters, and others don't (statistical multiverse / baby universe models). We just don't know, and sometimes it's enough to know that we don't know.

Re: Physicists now question the fate of the Universe

#48

Post by nutrie »

MilStdJunkie wrote: post #36

When I hear debates about whether or not the universes are black holes nested inside each other, or what the fate of the cosmos is, I often have an instinctive reaction to question whether or not concepts like "inside", "nested", or "fate" have actual fundamental qualities at the scales and timeframes under discussion.

In other words, we don't know shit.

Re: Physicists now question the fate of the Universe

#49

Post by mr_mitm »

slowmovintarget wrote: post #47
mr_mitm wrote: post #41

Earlier quoted context omitted.

There is nothing to agree on. You make measurements, see what model fits best, and then ask the model what will happen as time goes to infinity. And we did have a consensus: the standard model of cosmology. It fits the data best, that's how it became the standard model. Many cosmologists don't like the standard model, because it has some theoretical deficiencies. One example: The value of the dark energy density seem…

It seems wrong-headed that even the hint of a Creator requires turning theories into pretzels to remove that hint even when it's not proof. The "problem" of fine-tuning isn't really a problem. Why that value? We just don't know yet. Maybe God set it. Maybe we're part of an infinitely large cosmos where our false vacuum has these parameters, and others don't (statistical multiverse / baby universe models). We just don…

> Maybe we're part of an infinitely large cosmos where our false vacuum has these parameters, and others don't (statistical multiverse / baby universe models).

You'd be in good company with that approach.

Ironically, it becomes easier to explain if dark energy wasn't constant (see: TFA), because then you can make an anthropic argument, that only this part of the universe leads to complex structure and thus life. But for that you have study alternative models which might just be right.

>We just don't know, and sometimes it's enough to know that we don't know.

That is a very anti-science take that I find problematic. Curiosity is a very human trait and has been proven to be fruitful.

Re: Physicists now question the fate of the Universe

#50

Post by slowmovintarget »

mr_mitm wrote: post #49
slowmovintarget wrote: post #47

Earlier quoted context omitted.

It seems wrong-headed that even the hint of a Creator requires turning theories into pretzels to remove that hint even when it's not proof. The "problem" of fine-tuning isn't really a problem. Why that value? We just don't know yet. Maybe God set it. Maybe we're part of an infinitely large cosmos where our false vacuum has these parameters, and others don't (statistical multiverse / baby universe models). We just don…

> Maybe we're part of an infinitely large cosmos where our false vacuum has these parameters, and others don't (statistical multiverse / baby universe models). You'd be in good company with that approach. Ironically, it becomes easier to explain if dark energy wasn't constant (see: TFA), because then you can make an anthropic argument, that only this part of the universe leads to complex structure and thus life. But…

Heh... Yeah, I'm against the "shut up and calculate" mentality of the Copenhagen Interpretation.

Perhaps it's a problem with the science communication and less with the scientific community, but it seems like an often cited impetus for the science is supposed to be this overweening need to eliminate a negative association instead of to explain or satisfy curiosity.

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