Has anyone tried Michelson-Morley-type experiments with the ECI in mind?
amirjf nin wrote:
Has anyone tried Michelson-Morley-type experiments with the ECI in mind?
What do you mean by "Michelson-Morley-type experiment" and "with the ECI in mind"? What are you getting at?
*An* ECI (Earth-centered inertial) coordinate frame is a useful theoretical model for describing satellite orbits and analyze relativistic effects such as "gravitational time dilation" (scare quotes intended; it is a convenient misnomer), not something that can be realized physically/experimentally: there is no object that can practically be at rest in an ECI.
<https://en.wikipedia.org/wiki/Earth-centered_inertial>
On 2/19/2026 4:48 PM, Thomas 'PointedEars' Lahn wrote:
amirjf nin wrote:
Has anyone tried Michelson-Morley-type experiments with the ECI in mind?
What do you mean by "Michelson-Morley-type experiment" and "with the ECI in >> mind"? What are you getting at?
*An* ECI (Earth-centered inertial) coordinate frame is a useful theoretical >> model for describing satellite orbits and analyze relativistic effects such >> as "gravitational time dilation" (scare quotes intended; it is a convenient >> misnomer), not something that can be realized physically/experimentally:
there is no object that can practically be at rest in an ECI.
<https://en.wikipedia.org/wiki/Earth-centered_inertial>
I am fairly certain all of the mainstream papers regarding modern Michelson-Morley replications never ever mention "ECI".
amirjf nin wrote:
On 2/19/2026 4:48 PM, Thomas 'PointedEars' Lahn wrote:
amirjf nin wrote:
Has anyone tried Michelson-Morley-type experiments with the ECI in mind? >>>What do you mean by "Michelson-Morley-type experiment" and "with the ECI in >>> mind"? What are you getting at?
*An* ECI (Earth-centered inertial) coordinate frame is a useful theoretical >>> model for describing satellite orbits and analyze relativistic effects such >>> as "gravitational time dilation" (scare quotes intended; it is a convenient >>> misnomer), not something that can be realized physically/experimentally: >>> there is no object that can practically be at rest in an ECI.
<https://en.wikipedia.org/wiki/Earth-centered_inertial>
I am fairly certain all of the mainstream papers regarding modern
Michelson-Morley replications never ever mention "ECI".
Again, assuming that would be true, now knowing what an ECI is, why do you think that they should?
Has anyone tried Michelson-Morley-type experiments with the ECI in mind?
Den 19.02.2026 20:00, skrev amirjf nin:
Has anyone tried Michelson-Morley-type experiments with the ECI in mind?
If you by "the ECI" mean "the non-rotating frame of reference
where the centre of the Earth is stationary", this was very much
in Michelson's mind.
He tried to measure the speed of the ether in said frame.
In Michelson's words:"the motion of the earth through the ether".
https://paulba.no/paper/Michelson_1887.pdf
Den 19.02.2026 20:00, skrev amirjf nin:
Has anyone tried Michelson-Morley-type experiments with the ECI in mind?
If you by "the ECI" mean "the non-rotating frame of reference
where the centre of the Earth is stationary", this was very much
in Michelson's mind.
He tried to measure the speed of the ether in said frame.
In Michelson's words:"the motion of the earth through the ether".
https://paulba.no/paper/Michelson_1887.pdf
Paul B. Andersen <relativity@paulba.no> wrote:
Den 19.02.2026 20:00, skrev amirjf nin:
Has anyone tried Michelson-Morley-type experiments with the ECI in mind?
If you by "the ECI" mean "the non-rotating frame of reference
where the centre of the Earth is stationary", this was very much
in Michelson's mind.
He tried to measure the speed of the ether in said frame.
In Michelson's words:"the motion of the earth through the ether".
https://paulba.no/paper/Michelson_1887.pdf
But Michelson was well aware that there should be both a daily effect,
caused by the Earth' rotation, and a (much larger) yearly effect
caused by its orbital motion.
IIRC he looked for both, so he 'didn't think ECI',
(avant la lettre)
Jan
On 20/02/2026 11:55, Paul B. Andersen wrote:
Den 19.02.2026 20:00, skrev amirjf nin:
Has anyone tried Michelson-Morley-type experiments with the ECI in mind?
If you by "the ECI" mean "the non-rotating frame of reference
where the centre of the Earth is stationary", this was very much
in Michelson's mind.
He tried to measure the speed of the ether in said frame.
In Michelson's words:"the motion of the earth through the ether".
https://paulba.no/paper/Michelson_1887.pdf
The measurement described in the 1887 article was not sesitive enough
that the difference between the ECI frame and the surface frame would
matter.
Den 20.02.2026 13:21, skrev J. J. Lodder:
Paul B. Andersen <relativity@paulba.no> wrote:
Den 19.02.2026 20:00, skrev amirjf nin:
Has anyone tried Michelson-Morley-type experiments with the ECI in mind? >>If you by "the ECI" mean "the non-rotating frame of reference
where the centre of the Earth is stationary", this was very much
in Michelson's mind.
He tried to measure the speed of the ether in said frame.
In Michelson's words:"the motion of the earth through the ether".
https://paulba.no/paper/Michelson_1887.pdf
But Michelson was well aware that there should be both a daily effect, caused by the Earth' rotation, and a (much larger) yearly effect
caused by its orbital motion.
IIRC he looked for both, so he 'didn't think ECI',
(avant la lettre)
Jan
Michelson looked for "the motion of the earth through the ether".
What he tried to measure was the velocity of the ether relative
to the earth, that is the velocity of the ether in the non rotating
frame of reference where the centre of the earth is stationary -
now called the ECI-frame.
Michelson obviously knew that since the laboratory was on
a spinning Earth, the velocity of the lab would have a diurnal
varying component in the ECI-frame. But he didn't mention
this velocity in his paper, the only velocity he mentions is
"v = velocity of the earth in its orbit".
Michelson probably thought (knew) that the diurnal variations
would be negligible.
The yearly variation of the velocity of the ether due to
the orbiting of the earth around the sun was what he expected
to find.
The speed of a point on equator in the ECI-frame is 465 m/s.
The speed of the Sun in the ECI-frame is 2978000 m/s (~1e-4 c)
The fringe shifts he expected are proporsional to v?/c?.
The expected yearly effect is 40 millions time higher than
the diurnal effect.
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