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Cosmology Has Some Big Problems

blogs.scientificamerican.com

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Re: Cosmology Has Some Big Problems

#31

Post by astro123 »

scrozart wrote: post #24
astro123 wrote: post #15

I'm a grad student working on cosmology, and while I agree there is a lot of work still to do (we don't know what 95% of the matter that makes up the universe is!), I disagree with a lot of what the author says. > Another recent probe found galaxies inconsistent with the theory of dark matter, which posits this hypothetical substance to be everywhere. We have found evidence of a few galaxies without DM. But most gala…

> > Today's space telescopes provide no direct view of anything > I have no idea what that means. They literally observe the sky... Seriously! At this point they're just spitballing.

I was maybe a bit too cavalier here. I think I understand what the author means - the data that they gather is understood in the context of the model that we think is best.

But, it isn't as if cosmologists are rigidly holding to the model. Here's a paper looking at extensions to lambda CDM https://arxiv.org/abs/1512.05356. As I mentioned, changing GR is being looked at as an alternative to DE http://www.resceu.s.u-tokyo.ac.jp/workshops/resceu08s/presen...

People aren't challenging some things though - I don't think anyone is seriously working on cosmologies that don't include a big bang, because without one I can't imagine how you explain the CMB.

Re: Cosmology Has Some Big Problems

#32

Post by lkrubner »

jerf wrote: post #26
hhs wrote: post #7

Interesting view. Near the end, it says: “The crux of today's cosmological paradigm is that in order to maintain a mathematically unified theory valid for the entire universe, we must accept that 95 percent of our cosmos is furnished by completely unknown elements and forces for which we have no empirical evidence whatsoever.” Empiricism is based on sense observations. And a lot of science has been confined to human…

When it comes to cosmology, our observations have been using light, because that's what has traveled in space. It is pretty obviously not that useful to ask a dog to sniff the sky or a homing pidgeon to navigate to Alpha Centauri, or something. We've obviously long since passed using only the visible spectrum. We also recently added gravitational wave detection to our repertoire. I seriously doubt any animals out the…

About this:

"It is pretty obviously not that useful to ask a dog to sniff the sky or a homing pidgeon to navigate to Alpha Centauri, or something."

That example might be bad, but there are others that are valid. For instance, in healthy human women, the menstruation cycle seems to be the exact length of the moon's orbit. Is that a coincidence, or do human bodies have a way of gaining data from the moon? If so, what is that data? Maybe the mechanism is as simple as a springy protein that can absorb tidal forces and convert it to an information signal. Or perhaps something novel is going on.

There are potentially a lot we can learn about the universe by making simple observations here on Earth.

Re: Cosmology Has Some Big Problems

#33

Post by AnimalMuppet »

jerf wrote: post #26
hhs wrote: post #7

Interesting view. Near the end, it says: “The crux of today's cosmological paradigm is that in order to maintain a mathematically unified theory valid for the entire universe, we must accept that 95 percent of our cosmos is furnished by completely unknown elements and forces for which we have no empirical evidence whatsoever.” Empiricism is based on sense observations. And a lot of science has been confined to human…

When it comes to cosmology, our observations have been using light, because that's what has traveled in space. It is pretty obviously not that useful to ask a dog to sniff the sky or a homing pidgeon to navigate to Alpha Centauri, or something. We've obviously long since passed using only the visible spectrum. We also recently added gravitational wave detection to our repertoire. I seriously doubt any animals out the…

Yes and no. Yes, we're seeing gravity waves and radio waves and gamma rays and near infrared and millimeter wave and neutrinos, and maybe a few others that I forget. We're way past human senses, or any animals.

And yet I keep thinking of a deaf species that runs across Beethoven's Ninth Symphony. They can put an oscilloscope on the pressure waves in the air, so they can "see" what's going on. They can study the different frequencies of vibrations, and they can find patters in the time variation of those frequencies.

But they can't hear it. Hearing Beethoven's Ninth is really different from studying the frequencies with an oscilloscope. They could even hook up a brain scanner to a human listening to it, watch the brain start lighting up, and they still wouldn't understand.

We can gather data via all these different frequencies and modes. And yet I wonder how much we're not getting, not because we don't have the data, but because we don't have the right... something. (I can't even figure out what words to use for that something. The music analogy is the best I can do.)

Re: Cosmology Has Some Big Problems

#34

Post by petschge »

astro123 wrote: post #15

I'm a grad student working on cosmology, and while I agree there is a lot of work still to do (we don't know what 95% of the matter that makes up the universe is!), I disagree with a lot of what the author says. > Another recent probe found galaxies inconsistent with the theory of dark matter, which posits this hypothetical substance to be everywhere. We have found evidence of a few galaxies without DM. But most gala…

The fact that SOME galaxies are inconsistent with the theory of Dark Matter actually strengthens that theory.

If the difference in rotation curves, the usual signature of dark matter at the galaxy level, from what GR predicts based on the mass of luminous objects was due to a modification in the way gravity works, then that should apply to ALL galaxies. Modified Newtowian Dynamics (MOND) (or the relativistic TeVeS models) should work the same for all galaxies, at least all of roughly same mass and same depth of the gravitational potential.

The fact that we can find similar sized and aged galaxies that behave like they have different amounts of dark matter is therefore NOT caused by the way gravity works. The next best explanation is that most galaxies contain dark matter, but some loose it through their evolution history, e.g. due to interaction with other galaxies.

Re: Cosmology Has Some Big Problems

#35

Post by DubiousPusher »

AnimalMuppet wrote: post #33
jerf wrote: post #26

Earlier quoted context omitted.

When it comes to cosmology, our observations have been using light, because that's what has traveled in space. It is pretty obviously not that useful to ask a dog to sniff the sky or a homing pidgeon to navigate to Alpha Centauri, or something. We've obviously long since passed using only the visible spectrum. We also recently added gravitational wave detection to our repertoire. I seriously doubt any animals out the…

Yes and no. Yes, we're seeing gravity waves and radio waves and gamma rays and near infrared and millimeter wave and neutrinos, and maybe a few others that I forget. We're way past human senses, or any animals. And yet I keep thinking of a deaf species that runs across Beethoven's Ninth Symphony. They can put an oscilloscope on the pressure waves in the air, so they can "see" what's going on. They can study the diffe…

> Hearing Beethoven's Ninth is really different from studying the frequencies with an oscilloscope.

I'm not sure that's a good analogy. When you hear Beethoven's Ninth, you're not understanding it any more than someone who drives a car is understanding the car. You can enjoy it. Which is to say, you have an appreciation for its acoustic beauty but that doesn't really have anything to do with understanding it.

Perhaps there is some intelligence that set up the cosmos and they get some aesthetic pleasure from it. And perhaps our experience is too foreign from those being's to get the same pleasure from it but that does not mean that minus that experience we can't understand entirely how it works.

Re: Cosmology Has Some Big Problems

#36

Post by libraryofbabel »

AnimalMuppet wrote: post #33
jerf wrote: post #26

Earlier quoted context omitted.

When it comes to cosmology, our observations have been using light, because that's what has traveled in space. It is pretty obviously not that useful to ask a dog to sniff the sky or a homing pidgeon to navigate to Alpha Centauri, or something. We've obviously long since passed using only the visible spectrum. We also recently added gravitational wave detection to our repertoire. I seriously doubt any animals out the…

Yes and no. Yes, we're seeing gravity waves and radio waves and gamma rays and near infrared and millimeter wave and neutrinos, and maybe a few others that I forget. We're way past human senses, or any animals. And yet I keep thinking of a deaf species that runs across Beethoven's Ninth Symphony. They can put an oscilloscope on the pressure waves in the air, so they can "see" what's going on. They can study the diffe…

It's a good analogy, although I feel compelled to point out that Beethoven never heard Beethoven's Ninth either, since he was profoundly deaf when he wrote it.

Re: Cosmology Has Some Big Problems

#37

Post by whatshisface »

petschge wrote: post #34
astro123 wrote: post #15

I'm a grad student working on cosmology, and while I agree there is a lot of work still to do (we don't know what 95% of the matter that makes up the universe is!), I disagree with a lot of what the author says. > Another recent probe found galaxies inconsistent with the theory of dark matter, which posits this hypothetical substance to be everywhere. We have found evidence of a few galaxies without DM. But most gala…

The fact that SOME galaxies are inconsistent with the theory of Dark Matter actually strengthens that theory. If the difference in rotation curves, the usual signature of dark matter at the galaxy level, from what GR predicts based on the mass of luminous objects was due to a modification in the way gravity works, then that should apply to ALL galaxies. Modified Newtowian Dynamics (MOND) (or the relativistic TeVeS mo…

To be clear, they're not inconsistent with the theory of dark matter, they're inconsistent with those galaxies specifically having dark matter. The author was wording that in a confusing way.

Re: Cosmology Has Some Big Problems

#38

Post by hhs »

AnimalMuppet wrote: post #33
jerf wrote: post #26

Earlier quoted context omitted.

When it comes to cosmology, our observations have been using light, because that's what has traveled in space. It is pretty obviously not that useful to ask a dog to sniff the sky or a homing pidgeon to navigate to Alpha Centauri, or something. We've obviously long since passed using only the visible spectrum. We also recently added gravitational wave detection to our repertoire. I seriously doubt any animals out the…

Yes and no. Yes, we're seeing gravity waves and radio waves and gamma rays and near infrared and millimeter wave and neutrinos, and maybe a few others that I forget. We're way past human senses, or any animals. And yet I keep thinking of a deaf species that runs across Beethoven's Ninth Symphony. They can put an oscilloscope on the pressure waves in the air, so they can "see" what's going on. They can study the diffe…

Useful note, I get this thought sometimes, too. And you write, “We can gather data via all these different frequencies and modes. And yet I wonder how much we're not getting, not because we don't have the data, but because we don't have the right... something.”

Do you mean some type of “receptor” that we might be unaware of? For instance, data is flowing by but we can’t recognize/capture it?

Re: Cosmology Has Some Big Problems

#39

Post by fastbeef »

AnimalMuppet wrote: post #33
jerf wrote: post #26

Earlier quoted context omitted.

When it comes to cosmology, our observations have been using light, because that's what has traveled in space. It is pretty obviously not that useful to ask a dog to sniff the sky or a homing pidgeon to navigate to Alpha Centauri, or something. We've obviously long since passed using only the visible spectrum. We also recently added gravitational wave detection to our repertoire. I seriously doubt any animals out the…

Yes and no. Yes, we're seeing gravity waves and radio waves and gamma rays and near infrared and millimeter wave and neutrinos, and maybe a few others that I forget. We're way past human senses, or any animals. And yet I keep thinking of a deaf species that runs across Beethoven's Ninth Symphony. They can put an oscilloscope on the pressure waves in the air, so they can "see" what's going on. They can study the diffe…

Access to higher dimensions? Aliens shaking their heads as we waste enormous amounts of energy to travel through R3 in a straight line instead of taking a short walk in R7.

Re: Cosmology Has Some Big Problems

#40

Post by CriticalCathed »

AnimalMuppet wrote: post #33
jerf wrote: post #26

Earlier quoted context omitted.

When it comes to cosmology, our observations have been using light, because that's what has traveled in space. It is pretty obviously not that useful to ask a dog to sniff the sky or a homing pidgeon to navigate to Alpha Centauri, or something. We've obviously long since passed using only the visible spectrum. We also recently added gravitational wave detection to our repertoire. I seriously doubt any animals out the…

Yes and no. Yes, we're seeing gravity waves and radio waves and gamma rays and near infrared and millimeter wave and neutrinos, and maybe a few others that I forget. We're way past human senses, or any animals. And yet I keep thinking of a deaf species that runs across Beethoven's Ninth Symphony. They can put an oscilloscope on the pressure waves in the air, so they can "see" what's going on. They can study the diffe…

Would the idea of a flatlander being incapable of comprehending 3-space be similar to what you're thinking?
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