XPost: sci.astro
From: '''newspam'''@nonad.co.uk
On 05/02/2026 16:59, Jan Panteltje wrote:
>> Martin Brown <'''newspam'''@nonad.co.uk>wrote:
>>> On 05/02/2026 06:23, Jan Panteltje wrote:
>>>> Thomas 'PointedEars' Lahn wrote:
>>>> However, our universe is expanding, and there are points whose distance
from
>>>> each other increases faster than light could propagate between them. So
>>>> even if our universe would be closed, it would not be possible for light
to
>>>> arrive at its point of emission by going around our universe. Maybe that
is
>>>> the reason why this has never been observed.
>>>
>>> Just a simple question, I am no astrofishycist,
>>> is that 'expansion' we observe deduced from the red shifts we measure?
>>> Or brightness of some stars?
>>
>> Actually both. Redshifts give the most reliable data at cosmological
>> distances and you can see all the clouds of neutral hydrogen along the
>> like of sight if you find a suitably bright remote quasar. The so-called
>> Lyman forest of absorption lines.
>>
>> https://en.wikipedia.org/wiki/Lyman-alpha_forest
>>
>> In addition there are also certain stars like a particular class of
>> supernova type IA that due to how they arise go bang at more or less
>> exactly the same total mass every time and so from the lightcurve and
>> it's peak brightness you can work out how far away it is. The brightest
>> of the standard candles these supernovae can outshine their entire host
>> galaxy for a couple of weeks. Catching them early helps astrophysicists
>> pin them down and amateur supernova surveys with CCD cameras assist.
>>
>> https://science.nasa.gov/mission/roman-space-telescope/type-ia-supernovae/
>>
>> New professional hardware is coming online to speed discovery up.
>>
>> There is no way for us to know if the universe itself is infinite or
>> just very very big. There is always going to be a finite limit to the
>> region that we can ever know about (ignoring for the moment that at the
>> greatest distances it is an optically opaque hot plasma now seen as the
>> 4K microwave background radiation.
>>
>>> How about tired light theory (light slowing down causing redshift)?
>>
>> Doesn't really hack it at all. Pauli's phrase "Not even wrong" is
>> probably the kindest description for Le Sage Theory.
>>
>> https://en.wikipedia.org/wiki/Not_even_wrong
>
> Sure, but motivate it
> Today (and my hat of to German science teaching TV channels!) there was a
lecture' about 'quantum' in physics on zdfinfo.de
> program named Terra X presented by Harald Lesch (professor).
> And that is what I am missing on UK free to air TV, most there is braindead,
games and repeats of old movies.
> Now if they also kill social media for people younger than 16 like they do
down under, end of the world...
> Anyways, it went among other things into light as wave versus light as
particle, the 2 slit experiment, and quantum secure communication,
> a view at the experiments, visiting the labs etc etc..
> Now if you see light as a wave, then its speed depends on the medium.
The speed of light in a *vacuum* is a fundamental invariant for physics
proved by Maxwell from his equations of electromagnetism well before
Einstein had conceived of relativity. It was a surprise at the time.
It is one of the things that catches out experimenters measuring the
speed of light - imperfect vacuum in the apparatus has to be corrected
for. Even the best man-made hard vacuum is poor compared to near space.
The systematic correction is small but for a period was applied by a
highly respected experimenter in the wrong sense. People who duplicated
the setup also made the same error. It was only noticed when a new
method came available with better precision and a harder vacuum that the
mistake was discovered. Speed of light with error bars as a function of
time and method employed makes for an interesting graph.
> Consensus these days is that the universe is not empty, talk about dark
matter (or Le Sage particles in my take)
> would mean that light speed can vary depending on the density of the medium,
> Jeroen from CERN had pointed to a paper that shows the universe filled with
a fluid makes most math for elementary particles as we know it work.
There is no need for a cosmic ether.
Michelson-Morely null result put paid to that idea a long time ago.
There is a sea of virtual particles flipping into and out of existence
on borrowed energy as can be demonstrated by the Casimir effect.
> Epicycles was good math but the planets do orbit the sun...
> Makes it all (sort of) simple..
Epicycles were the Fourier transform method of their day. They worked
well enough to enable practitioners to do what they needed to do.
Eventually better observational constraints and new theories come along
that can improve upon the established methods of the day. Back when
Galileo was around the Jesuit astronomers were happy enough to use
heretical heliocentric solutions in private because they worked.
Even now the most accurate planetary ephemeris is computed using
symbolic expansions of the perturbations of every planet on every other.
It all gets very messy in the real world even with just 9 planets.
> You need a *mechanism* to explain and predict things!! New things!!!
Unless your theory has predictive powers and predicts something new that
can be experimentally verified or used to refute it then it isn't a
scientific theory it is just random word salad pseudoscience.
--
Martin Brown
--- SoupGate-Win32 v1.05
* Origin: you cannot sedate... all the things you hate (1:229/2)
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