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Webb and Hubble confirm Universe's expansion rate

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Re: Webb and Hubble confirm Universe's expansion rate

#301

Post by SkyBelow »

pfannkuchen wrote: post #210

I don’t really understand how we can make conclusions about the entire universe when literally all of the data is collecting from one point in space. Couldn’t there be local effects that obfuscate global behavior? Is there an implicit caveat asterisk on all such statements that is like “as far as we can possibly tell from the data we have” and the reality is we really, really don’t know for sure?

Yes, there is such an implicit caveat on all of science.

Science at its core runs on a repeated process of collect some data, explain it, collect some more data, explain it as well, and keep repeating forever. The scientific model you are likely more familiar with refines this a bit where you use the current model and data to direct where you spend your time/funding collecting more data, but that is mostly a heuristic. Sometimes a person going off on their own will find something amazing to bring back, but we have to remember that many others spend their entire lives and end up finding nothing new or noteworthy.

One problem with science literacy is that too many people treat the existing models as true, even when they aren't. In some cases we know they aren't correct because there are discrepancies in experiments that shouldn't exist, but no model better fits the data and resolves the discrepancies.

At no point can science say "this model is how reality must work". But that is somewhat scary. It is scary to think the truth is unknowable and at best we will have an ever better approximation, so people find it simpler to treat that approximation as truth.

Re: Webb and Hubble confirm Universe's expansion rate

#302

Post by baq »

munksbeer wrote: post #295
effingwewt wrote: post #274

Earlier quoted context omitted.

Let me try to explain- galaxies moving would be like balls floating in a pool. The galaxies are moving across the water. Space moving would be like balls placed on a bed sheet and the sheet expanding. The galaxies aren't moving- the sheet is. What's actually happening is more like galaxies moving around on a sheet that's being pulled further at all sides.

How can you tell the difference?

things are moving away from other things the faster the farther away they are, uniformly across the universe. everything is moving away from everything, not just two particular points.

is there a difference if there isn't a difference?

Re: Webb and Hubble confirm Universe's expansion rate

#303

Post by denton-scratch »

explaininjs wrote: post #277
denton-scratch wrote: post #218

Earlier quoted context omitted.

> the first "year" of reality was far longer than one year today This talk about the "rate of time" doesn't make any sense to me. A second takes one second, and always has. Isn't this like asking whether the length of a metre might have changed over time? Or the mass of a kilogramme? It looks to me like a category error.

`This talk about the "rate of execution" doesn't make any sense to me. A cycle takes one cycle, and always has.` The root of the question is whether there exists an external "system clock", and what that would even mean.

> whether there exists an external "system clock"

I'll ignore your analogy with a CPU, which I don't think is apposite.

Whether there's a 'system clock', a sort of reference clock that can tell you how fast time is passing, so you can calibrate other clocks against it, seems to be the same category error. As far as I can see, either time is all there, all at once; or one second lasts exactly one second. (I've perpetrated the same category error there, because a second doesn't 'last' for some period of time; it just is).

[Edit] That's not very clear. I mean: if you are measuring a distance, you use a calibrated ruler. If you doubt the calibration of your ruler, you might recalibrate for precision. But you don't have a clear idea of what one foot is, it doesn't make any sense to ask whether your one-foot ruler has grown or shrunk; how would you tell if the purported 'fact' is true or false?

And if some fact about the Universe means that it has grown or shrunk, how would you tell? If you can't in principle tell whether a 'fact' is true or false, it follows that the 'fact' isn't a fact, because it has no effect on anything.

See Russells Teapot.

Re: Webb and Hubble confirm Universe's expansion rate

#304

Post by Cthulhu_ »

whimsicalism wrote: post #235
luc4sdreyer wrote: post #212

Earlier quoted context omitted.

> Nobody had a clue In the 3rd century BC, Aristarchus calculated that the Sun was between 18 and 20 times farther away from the Earth than the Moon, and proposed the Heliocentric model as a result. The true value is instead approximately 400 times. But it's incredible given that he didn't have lenses, the value of Pi, and that the Geocentric model was considered correct until 1800 years after his death. https://en.w…

yeah i would call estimating it as 20x when it is actually 400x firmly within “not having a clue”. He didn’t say nobody had a clue about heliocentrism.

I appreciate that he worked on it at least. Around the same era, someone else calculated the circumference of the earth (and that it was round) in a pretty accurate fashion (between −2.4% and +0.8% off) based on measuring shadows on equally sized posts at different locations on the same date. Googled, it was Eratosthenes, the cities were Alexandria and Syene/Assuan.

Re: Webb and Hubble confirm Universe's expansion rate

#305

Post by pigpang »

munksbeer wrote: post #296
pigpang wrote: post #257

Earlier quoted context omitted.

Spacetime is 4D array of points. It's like a movie file, but with 3D frames instead of 2D frames (pictures). Expansion of space means that coordinates of points in a frame changed to move away from us, to match movie (model) with reality.

An array of 4D points implies some sort of construct upon which the points exist. As far as I know, the that was the concept of "the ether" and that fell out of fashion long ago. So again, how can you tell the difference between space expanding or two things actually just moving away from each other (to keep it to a very simple example of two bodies).

Ether now known as "physical vacuum". As I told you already, expansion of spacetime is the mathematical tool, like a shader in OpenGL.

Re: Webb and Hubble confirm Universe's expansion rate

#306

Post by physicles »

kovacs_x wrote: post #262

I'm 1000% sure, in 20, 50, 100, 500 years humans will look back on "science of 20/21th century" as we look now on say 16/17th century- there were some things that were "mostly" right, but most of it was incorrect / inprecise / incomplete and was a fantasy of earlier thought up models. It's been like that always. Don't think it'll be different this time. Though people of every time thought they had (almost) complete u…

Sure, the frontier is always messy. Scientists talk about “quarks” and “dark energy” but those are just placeholders for “we kinda get what they do but we have no idea what they actually are.”

100 or 500 years from now, QM and GR will turn out to be approximations, or shadows, of some deeper theory. But that won’t change how insanely accurate their predictions are.

Our understanding of reality isn’t just moving forward, it’s getting asymptotically closer to ground truth. New theories may upend the conceptual framework, but they still just add decimal points — they have to, otherwise they’re worse theories than what we already have.

Re: Webb and Hubble confirm Universe's expansion rate

#307

Post by pigpang »

mrguyorama wrote: post #280
pigpang wrote: post #197

Earlier quoted context omitted.

> That seems contradictory and unintuitive, that two observers moving away from each other both measure light moving c relative to themselves, but that’s reality. Light is a wave. Photon is a complex thing (Hopfion?), but it's a wave, so it waves something, a medium. Speed of wave propagation in a medium is constant. IMHO, it's intuitive.

>but it's a wave, so it waves something, a medium. Which was unobserved in the michleson-morely experiment and other followup experiments because....?

LIGO/Virgo are better version of Michelson-Morely experiment. Gravitational waves are found, so existence of a medium is confirmed.

Re: Webb and Hubble confirm Universe's expansion rate

#308

Post by mrguyorama »

dvsfish wrote: post #281
mrguyorama wrote: post #270

Earlier quoted context omitted.

If you want creativity, take an art class. This is cosmology, ostensibly a science. Pulling wild ideas out of thin air and basically ad-libbing a "theory" is not.

So we have to put everyone who dares to imagine down about it? I see value in sharing a wild idea purely for the inspiration it may give others to think about things from a unique perspective. A lot of great science started as a strange idea.

What's the value in """daring to imagine""" about cosmology? This is nothing more than reality based fan fiction.

>A lot of great science started as a strange idea.

Disagree. A lot of great science started with "This weird math I'm doing is the only way to fit this data", which is an extremely different thing.

Do you not think physicists and cosmologists and their nerdy friends have thought of wild ideas? Do you not think undergrad students spend drunken friday nights theorycrafting universes?

It's pretty disrespectful to "why don't you just" a profession without showing that you at least did your homework first, or that you have looked at whoever definitely asked that question before you.

There are people in this post reinventing Tired light and Aether based theories for crying out loud, theories with fairly conclusive reasons we abandoned them.

When you just ass-pull theorycrafting without any of the fundamentals, all you do is talk in circles. It's no better than all the dumb "the brain is like a computer" arguments by analogy in neuroscience posts.

It's not even wrong.

We live in a world where the people who had to cheat off me in high school biology angrily insist that the vaccine doesn't work. Do we really benefit from playing such anti-scientific games?

Re: Webb and Hubble confirm Universe's expansion rate

#309

Post by mrguyorama »

pigpang wrote: post #307
mrguyorama wrote: post #280

Earlier quoted context omitted.

>but it's a wave, so it waves something, a medium. Which was unobserved in the michleson-morely experiment and other followup experiments because....?

LIGO/Virgo are better version of Michelson-Morely experiment. Gravitational waves are found, so existence of a medium is confirmed.

Gravitational waves existing doesn't confirm the existence of a medium any more than discovering light behaves like a wave confirms the existence of the aether.

If you want to posit that light has a medium, you need to redo 100 years of physics, so start showing your work. You mention elsewhere "doing a calculation", and that's just not nearly good enough. You want to overturn perfectly working physics, you NEED to show up with receipts. That's table stakes.

Re: Webb and Hubble confirm Universe's expansion rate

#310

Post by fooker »

explaininjs wrote: post #170
fooker wrote: post #32

Earlier quoted context omitted.

Philosophical indeed, as it's impossible to define the idea of a rate of time, when the idea of rate is defined in terms on time itself.

Yes, an external reference clock is needed. If a computer chugs along doing { counter++; } at 1 clock cycle per clock cycle for 13.7 billion clock cycles, it will think 13.7 billion clock cycles have passed when counter is 13.7 billion. On the other hand, if a computer chugs along at one clock cycle per clock cycle for 1 clock cycle, and reads &counter and sees 13.7 billion, it will think 13.7 billion clock cycles ha…

This reminds me of old computer games that started to run faster on newer computers, because of strong assumptions about clock speeds!

For a hypothetical entity inside the game, nothing would have changed.

https://www.vogonswiki.com/index.php/List_of_CPU_speed_sensi...

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