What is your argument against this?

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Johnny Blade
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Re: What is your argument against this?

Post by Johnny Blade »

Rumraket wrote: Aug 03, 2024 12:10 pm
That looks like a clear downward trend to me, yes.

There's a lot of uncertainty due to different methods, and another problem is the mass class also strongly affects metallicity. Ideally we'd want to tr ack metallicity with redshift for a specific galaxy mass class. They do this in Zahid et al. 2021:
Skærmbillede 2024-08-03 135747.png

Notice the mass-metallicity relation decreases obviously with redshift. The blue curve is redshift z=0.08, yellow curve (which is below blue) z=0.29, and so on, with the red curve (highest redshift) also showing lowest metallicities. So yes, there's a clear and obvious correlation when controlling for the mass-metallicity relation.

Yes, there's a mass-metallicity relation too, in addition to a redshift-metallicity relation. You need to control for mass, which the website you linked doesn't do.
Johnny Blade wrote: Aug 02, 2024 5:13 pm Do you still believe metallicity is a good way to determine age?
I would say there's an obvious correlation for specific mass classes, yes.
So I'm not so sure yet why you think any of this means what you think it means. Best I can figure is that our galaxy has a higher mass than about 85% of all known galaxies. And it also has a metallicity thats higher than about 85% of known galaxies. This has been known for some time now. So of course, to find more galaxies, we have to look farther out into space. And almost all of the new galaxies we find will have less mass and less metal than the milky way.

So considering we have observed at the most, 5% of the knowable universe (I don't know where they get that number from. Maybe you can help me.) and further considering the morphology of galaxies we find (galaxy bars ect), It looks like the trend is that we will just find all kinds of different galaxies, everywhere, relative to our own high mass and high metal galaxy.
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Re: What is your argument against this?

Post by Rumraket »

The Milky way galaxy is among the top 15% on terms of mass? Okay, and?
Johnny Blade wrote: Aug 07, 2024 9:08 pm So considering we have observed at the most, 5% of the knowable universe (I don't know where they get that number from. Maybe you can help me.) and further considering the morphology of galaxies we find (galaxy bars ect), It looks like the trend is that we will just find all kinds of different galaxies, everywhere, relative to our own high mass and high metal galaxy.
The trend we have is that metallicity correlates inversely with redshift, as predicted by big bang cosmology.

Since the further away we look, the further back in time we look, the more time has there been for space to expand and light to be shifted towards longer wavelengths. And so since the universe is predicted to have once consisted almost entirely of hydrogen and helium, then the first stars would have consisted of only that.
And these stars and subsequent generations of them would have been producing all the elements heavier than helium, and so the more time have passed since that the more heavy elements have had time to build up. So since the closer to our own milky way, the closer to the present in time we look, the higher the metallicity on average.

The logic here seems perfectly straightforward and comprehensible to me. Close to the milky way, closer to the present. Closer to the present, longer since the big bang. More time, more time for metallicity to build up.

This trend hasn't been falsified or overturned that I am aware of. The situation in cosmology with the JWST is, to my mind, like we had a model that was created to fit observations we had from previous generations of telescopes, and it predicted a decreasing trend of, say, 0.9x (to just pick some number out of a hat to make a point). But a better telescope now tells us the trend is probably closer to 0.92x. Whoah, how will big bang cosmology survive?

If you read the pop-sci press you come away with the fatuous picture that astronomers and cosmologists are "surprised", "nobody expected this", "this galaxy shouldn't be possible", heads are exploding everywhere, textbooks have to be rewritten, and everything we use to think we knew is false so make-believe is just as reasonable as, well, all of modern science. Etc. etc.

It's ridiculous of course. This kind of reporting on the science is driven by bad incentives. Attention-grabbing, career-advancement, attracting researchers and grad-students to your institutions/university, generating hype and interest, attracting grants and funding, etc. The scientists themselves are often totally complicit in hyping, dramatizing, and overselling their results.

Meanwhile the truth is actually much better summarzied as something along the lines that "the best current model didn't entirely accurately predict the rate of star formation very close to the big bang, and possibly models that predicted a top-heavy initial mass function were correct all along." But that sounds much less shocking, doesn't it?
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Re: What is your argument against this?

Post by Spearthrower »

murshid wrote: Jul 07, 2024 9:46 pm One argument I heard for the universe beginning to exist a finite time ago (as stated in Kalam) is that if it began to exist infinite time ago, the universe would have already suffered heat death, and since it didn't, it began to exist a finite time ago, that is the universe began to exist.

What is the usual counter-argument to that?

You can respond with any argument you like because it is merely an assertion that has no basis in either fact or logic, so the response could as well be 'jam' as anything and be precisely sufficient.
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Re: What is your argument against this?

Post by Spearthrower »

There is no counter argument against it. The universe most definitely had a beginning, as stated in the first verse of the Bible.
1 In the beginning God created the heavens and the earth.
Factually, the Bible does not say that the universe had a beginning. The first verse of the Bible seems to be talking expressly about our world. I assume this is because the ancient people who created these stories were essentially completely ignorant of the rest of the universe.

Even if we interpret the phrase 'heavens and earth' to mean 'everything' - that still doesn't say or mean that God created the universe - it could just as well be read that God created everything within the existing empty universe.

What's stunning is how people try to take this extremely simplistic statement in the Bible and pretend that modern science corroborates it. What utter pish.
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