One of the concepts that have bothered me the most is the idea that the universe is ever exapanding.
If space is constantly exanding and we are in space, then our measuring sticks would also be expanding so we wouldn't be able to see it and
there would be no doppler effect.
Ruben Safir wrote:
One of the concepts that have bothered me the most is the idea that the
universe is ever exapanding.
[_expanding_]
We do not know that. We know that our universe is expanding now and has
been in the past (because we observe the cosmological redshift); but it is uncertain for how long, if at all, this will continue. The reason for that is that recent observations indicate that the Dark Energy density could be time-dependent (in the current Standard Model of cosmology, it is constant, leading to an exponential expansion). If it decreases, then gravitation might be able to slow down the expansion after all, and even reverse it, leading to a Big Crunch:
<https://www.quantamagazine.org/is-dark-energy-getting-weaker-new-evidence-strengthens-the-case-20250319/>
If space is constantly exanding and we are in space, then our measuring
sticks would also be expanding so we wouldn't be able to see it and
there would be no doppler effect.
No. First of all, you need to realize how large our universe is and how small everything in it is by comparison. This is best illustrated with numbers:
Terra (Earth) is a planet with a diameter of ca. 12'642 km (if you think
that is big, read on). Sol (the Sun) is a star with a diameter of ca. 1'400'000 (1.4 million) km. The average distance of Terra to Sol is approximately 150'000'000 (150 million) km. The distance to the next star from Sol, Proxima Centauri, is ca. 4.25 ly (light-years); that is, ca. 4.25 times the distance that light travels in vacuum in one Julian year: ca. 40 *trillion* (short scale) kilometers. Both those stars are two of approximately 200 billion stars in the Milky Way (each which on average at least one planet) which has a diameter of approximately 200'000 ly. The Milky Way is one of ca. 200 billion to 2 trillion galaxies in our observable universe which has a diameter of ca. 96 billion light-years. Our entire universe has a diameter that is at least 500 times as large as the
observable one's.
In the words of Douglas Adams, written in or before 1978 already:
"Space [says the Hitchhiker's Guide to the Galaxy] is big. You just won't
believe how vastly, hugely, mind-bogglingly big it is. I mean, you may
think it's a long way down the road to the chemist's, but that's just
peanuts to space."
The expansion of the space of our universe is a metric expansion -- all length scales are growing --, so the rate at which distances change itself depends on distance. Given the size of our universe (or even only the observable one), the rate at which distances change on everyday scales is (currently) so small that any short-range forces/interactions compensate for the expansion immediately. In fact, within the Local Group (of galaxies) to of which the Milky Way is one major component, gravitation dominates over
the expansion; the Andromeda Galaxy, the other major component of the Group, and the Milky Way are *approaching* each other (and might merge in several billion years from now) due to gravitation.
To get an idea how small the rate is at which space is expanding at everyday scales, multiply a distance by the Hubble constant, the current value of the Hubble parameter. Measurements of that vary, but so far the concordance value is ca. (70 km/s)/Mpc. 1 pc (parsec) is the distance an object needs
to have from Sol so that its annual parallax, half the angle under which it is observed from opposite sides of the orbit of Terra, is 1" (arcsecond, seconds of arc); that is, ca. 3.26 ly.
Second, the cosmological redshift is NOT a Doppler redshift. The galaxies are not really moving (by comparison) in their local space, but space is expanding and is carrying them away from each other. The cosmological redshift arises because the light was emitted in a different reference/rest frame than it is received: the length scales were smaller then than they are now, including the wavelengths of light.
Since the expansion is predicted and described by general relativity, it is better to continue discussing this in sci.physics.relativity. X-Post &
F'up2 set.
On 12/23/2025 03:42 PM, Thomas 'PointedEars' Lahn wrote:
Ruben Safir wrote:
One of the concepts that have bothered me the most is the idea that the
universe is ever exapanding.
[_expanding_]
We do not know that. We know that our universe is expanding now and has been in the past (because we observe the cosmological redshift); but it is uncertain for how long, if at all, this will continue. The reason for that is that recent observations indicate that the Dark Energy density could be time-dependent (in the current Standard Model of cosmology, it is constant, leading to an exponential expansion). If it decreases, then gravitation might be able to slow down the expansion after all, and even reverse it, leading to a Big Crunch:
<https://www.quantamagazine.org/is-dark-energy-getting-weaker-new-evidence-strengthens-the-case-20250319/>
If space is constantly exanding and we are in space, then our measuring
sticks would also be expanding so we wouldn't be able to see it and
there would be no doppler effect.
No. First of all, you need to realize how large our universe is and how small everything in it is by comparison.
--This is best illustrated with numbers:
Terra (Earth) is a planet with a diameter of ca. 12'642 km (if you think that is big, read on). Sol (the Sun) is a star with a diameter of ca. 1'400'000 (1.4 million) km. The average distance of Terra to Sol is approximately 150'000'000 (150 million) km. The distance to the next star from Sol, Proxima Centauri, is ca. 4.25 ly (light-years); that is, ca. 4.25 times the distance that light travels in vacuum in one Julian year: ca. 40 *trillion* (short scale) kilometers. Both those stars are two of approximately 200 billion stars in the Milky Way (each which on average at least one planet) which has a diameter of approximately 200'000 ly. The Milky Way is one of ca. 200 billion to 2 trillion galaxies in our observable
universe which has a diameter of ca. 96 billion light-years. Our entire universe has a diameter that is at least 500 times as large as the observable one's.
Ross Finlayson <ross.a.finlayson@gmail.com> posted:
On 12/23/2025 03:42 PM, Thomas 'PointedEars' Lahn wrote:
Ruben Safir wrote:
One of the concepts that have bothered me the most is the idea that the >>>> universe is ever exapanding.
[_expanding_]
We do not know that. We know that our universe is expanding now and has >>> been in the past (because we observe the cosmological redshift); but it is >>> uncertain for how long, if at all, this will continue. The reason for that >>> is that recent observations indicate that the Dark Energy density could be >>> time-dependent (in the current Standard Model of cosmology, it is constant, >>> leading to an exponential expansion). If it decreases, then gravitation >>> might be able to slow down the expansion after all, and even reverse it, >>> leading to a Big Crunch:
<https://www.quantamagazine.org/is-dark-energy-getting-weaker-new-evidence-strengthens-the-case-20250319/>
If space is constantly exanding and we are in space, then our measuring >>>> sticks would also be expanding so we wouldn't be able to see it and
there would be no doppler effect.
No. First of all, you need to realize how large our universe is and how >>> small everything in it is by comparison.
No, not if we make a meaningful comparison in terms of mass or numbers of atoms.
OK, the volume of the universe is large, but it makes little sense to ignore the
fact that it is overwhelmingly empty. In terms of mass it is only about 10^27 times
larger than the Earth, whereas the Earth is 10^40 times larger than an E. coli
cell. In other words the Earth is _much_ larger on the scale of a bacterial cell than the universe is on the scale of the Earth.
This is best illustrated with numbers:
Terra (Earth) is a planet with a diameter of ca. 12'642 km (if you think >>> that is big, read on). Sol (the Sun) is a star with a diameter of ca.
1'400'000 (1.4 million) km. The average distance of Terra to Sol is
approximately 150'000'000 (150 million) km. The distance to the next star >>> from Sol, Proxima Centauri, is ca. 4.25 ly (light-years); that is, ca. 4.25 >>> times the distance that light travels in vacuum in one Julian year: ca. 40 >>> *trillion* (short scale) kilometers. Both those stars are two of
approximately 200 billion stars in the Milky Way (each which on average at >>> least one planet) which has a diameter of approximately 200'000 ly. The >>> Milky Way is one of ca. 200 billion to 2 trillion galaxies in our observable
universe which has a diameter of ca. 96 billion light-years. Our entire >>> universe has a diameter that is at least 500 times as large as the
observable one's.
Ruben Safir wrote:
One of the concepts that have bothered me the most is the idea that the universe is ever exapanding.
[_expanding_]
We do not know that. We know that our universe is expanding now and has
Thomas 'PointedEars' Lahn wrote:
Ruben Safir wrote:
One of the concepts that have bothered me the most is the idea that the
universe is ever exapanding.
[_expanding_]
We do not know that. We know that our universe is expanding now and has
"We"???? you mean me, myself and I?
I'm flabgastted that people till this day are testing Positive for
Stupid in these sci newsgroups.
The UNIVERSE IS *NOT* EXPANDING! It *never* has expanded. It remains the
same size it always has been since it existence.
The Big Bang was the 'expansion' of ...space, not the expansion of the universe.
Space is expanding, not the universe.
The Starmaker wrote:
Thomas 'PointedEars' Lahn wrote:
Ruben Safir wrote:
One of the concepts that have bothered me the most is the idea that the >>>> universe is ever exapanding.
[_expanding_]
We do not know that. We know that our universe is expanding now and has
"We"???? you mean me, myself and I?
I'm flabgastted that people till this day are testing Positive for
Stupid in these sci newsgroups.
The UNIVERSE IS *NOT* EXPANDING! It *never* has expanded. It remains the
same size it always has been since it existence.
The Big Bang was the 'expansion' of ...space, not the expansion of the
universe.
Space is expanding, not the universe.
--------------------------------------------
Space is space, it dosen't expand.
The Starmaker wrote:
Thomas 'PointedEars' Lahn wrote:
Ruben Safir wrote:
One of the concepts that have bothered me the most is the idea that the >>>> universe is ever exapanding.
[_expanding_]
We do not know that. We know that our universe is expanding now and has
"We"???? you mean me, myself and I?
I'm flabgastted that people till this day are testing Positive for
Stupid in these sci newsgroups.
The UNIVERSE IS *NOT* EXPANDING! It *never* has expanded. It remains the
same size it always has been since it existence.
The Big Bang was the 'expansion' of ...space, not the expansion of the
universe.
Space is expanding, not the universe.
Space is space, it dosen't expand.
squalk wrote:
The Starmaker wrote:
Thomas 'PointedEars' Lahn wrote:
Ruben Safir wrote:"We"???? you mean me, myself and I?
One of the concepts that have bothered me the most is the idea that the >>>> universe is ever exapanding.
[_expanding_]
We do not know that. We know that our universe is expanding now and has >>
Astrophysicist/cosmologists. The scientific community.
I'm flabgastted that people till this day are testing Positive for
Stupid in these sci newsgroups.
The UNIVERSE IS *NOT* EXPANDING! It *never* has expanded. It remains the >> same size it always has been since it existence.
Observationally falsified.
The Big Bang was the 'expansion' of ...space, not the expansion of the
universe.
The Big Bang _is_ the expansion of the space of our universe. AFAWCS it is ongoing.
squalk wrote:
The Starmaker wrote:
Thomas 'PointedEars' Lahn wrote:
Ruben Safir wrote:"We"???? you mean me, myself and I?
One of the concepts that have bothered me the most is the idea that the >>>>> universe is ever exapanding.
[_expanding_]
We do not know that. We know that our universe is expanding now and has >>>
Astrophysicist/cosmologists. The scientific community.
I'm flabgastted that people till this day are testing Positive for
Stupid in these sci newsgroups.
The UNIVERSE IS *NOT* EXPANDING! It *never* has expanded. It remains the >>> same size it always has been since it existence.
Observationally falsified.
squalk wrote:
The Starmaker wrote:
Thomas 'PointedEars' Lahn wrote:
Ruben Safir wrote:"We"???? you mean me, myself and I?
One of the concepts that have bothered me the most is the idea that the >>>>> universe is ever exapanding.
[_expanding_]
We do not know that. We know that our universe is expanding now and has >>>
Astrophysicist/cosmologists. The scientific community.
I'm flabgastted that people till this day are testing Positive for
Stupid in these sci newsgroups.
The UNIVERSE IS *NOT* EXPANDING! It *never* has expanded. It remains the >>> same size it always has been since it existence.
Observationally falsified.
The Big Bang was the 'expansion' of ...space, not the expansion of the
universe.
The Big Bang _is_ the expansion of the space of our universe. AFAWCS it is ongoing.
Space is expanding, not the universe.
Our universe is to good approximation well described by spacetime, particularly the FLRW metric
ds^2 = -dt^2 + a(t)^2 [1/(1 - k r^2) dr^2 + r^2 (d Omega)^2],
(d Omega)^2 = (d theta)^2 + sin^2(theta) (d phi)^2,
where a(t) is the scale factor at the cosmological time t -- which is currently increasing --, and r, theta and phi are spatial (spherical) coordinates. So our universe and space are inseparable concepts: When we
say "space" in cosmology, we mean the space *of our universe* (at least the observable one).
[Notice that this is different from colloquial use where "space" often
is a shorthand for "outer space", i. e. the space of our universe outside
Terra's atmosphere.]
Space is space, it dosen't expand.
Wrong, too. We can *observe* the expansion and evolution of our universe because we can observe galaxies as they were in the past: The light that
they emitted takes time to get to us. The farther an object is away, the earlier the light was emitted that reaches us now:
<https://youtu.be/Fqfap3v0xxw?t=791&si=ro2EG6Cx9Sqg05hr>
On 12/28/2025 10:51 AM, Thomas 'PointedEars' Lahn wrote:
squalk wrote:
The Starmaker wrote:
Thomas 'PointedEars' Lahn wrote:
Ruben Safir wrote:
One of the concepts that have bothered me the most is the idea
that the
universe is ever exapanding.
[_expanding_]
We do not know that. We know that our universe is expanding now
and has
"We"???? you mean me, myself and I?
Astrophysicist/cosmologists. The scientific community.
I'm flabgastted that people till this day are testing Positive for
Stupid in these sci newsgroups.
The UNIVERSE IS *NOT* EXPANDING! It *never* has expanded. It remains
the
same size it always has been since it existence.
Observationally falsified.
The Big Bang was the 'expansion' of ...space, not the expansion of the >>>> universe.
The Big Bang _is_ the expansion of the space of our universe. AFAWCS
it is
ongoing.
Space is expanding, not the universe.
Our universe is to good approximation well described by spacetime,
particularly the FLRW metric
ds^2 = -dt^2 + a(t)^2 [1/(1 - k r^2) dr^2 + r^2 (d Omega)^2],
(d Omega)^2 = (d theta)^2 + sin^2(theta) (d phi)^2,
where a(t) is the scale factor at the cosmological time t -- which is
currently increasing --, and r, theta and phi are spatial (spherical)
coordinates. So our universe and space are inseparable concepts: When we
say "space" in cosmology, we mean the space *of our universe* (at
least the
observable one).
[Notice that this is different from colloquial use where "space" often
is a shorthand for "outer space", i. e. the space of our universe
outside
Terra's atmosphere.]
Space is space, it dosen't expand.
Wrong, too. We can *observe* the expansion and evolution of our universe
because we can observe galaxies as they were in the past: The light that
they emitted takes time to get to us. The farther an object is away, the
earlier the light was emitted that reaches us now:
<https://youtu.be/Fqfap3v0xxw?t=791&si=ro2EG6Cx9Sqg05hr>
Well you know the reason it's said "Dark Energy" is everywhere
is since there are conflicting observations in theory between
the usual idea after the inflationary epoch of expansionary cosmology
and the energy budget.
So, when you say "observationally falsified", well, you know,
yes and no. One fragment of a deciding theory is falsified,
well and good, yet then the wider fragment falsifies that,
then, ideas about the energy budget have been around pretty
much since the age of Hubble and Le Maitre.
Of course neither of "Big Bang" nor "Steady State" are
falsifiable, and both somehow fit the data.
Yet, "Dark Energy" has falsified the usual account of
either, about the energy budget.
One hopes the Nancy Grace Roman space telescope makes
it on station next year or so, the wide-field array will
be making quite a different perspective on things.
Yet, even a few hermits on a hill can notice physics' crises.
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