There are 7 basic critical flaws in relativity making it an invalid model for cosmology.
Time is not a dimension; time is an incremental measurement.
Mankind has agreed upon the definition of a second.
Time is used to make measurements in physics simply because no motions are instantaneous.
Changes in position over time allows the calculation of an object's velocity.
Distance is the measurement between two points in space but distance is not part of the physical space.
Time is used to make measurements in chemistry simply because changes in molecular bonds are not instantaneous.
In both cases time is not connected to space in a 3-dimensional Euclidean geometry(height, width, depth). Time is just a measurement of a change that is not instantaneous.
An object does not move in time. While an object is moving or stationary the current time can be sampled. Time is an accumulation of counts having nothing to do with space or motion in space.
Relativity replaces time as used in both classical physics and chemistry with time as a dimension in the observer's reference frame.
This allows relativity to distort time like a dimension in a coordinate system but time is just an incrementing count of events, usually treated as an increasing number of seconds.
Relativity assumes time is a dimension which an object can move along but time is an independent entity and not like that. This is a fundamental flaw.
Gravity is not the most significant force in the universe. It is actually much weaker than the other two major forces, from either an electric field or a magnetic field.
Relativity assumes gravity is the only important force. It is the only force that affects the observer's motion, which involves distorting the observer's spacetime in relativity. This omission of electromagnetic forces is a fundamental flaw.
Relativity has a second flaw with gravity, its assumption gravity is a force with a speed limited to c.
Isaac Newton was correct when he concluded gravity is instantaneous.
The evidence is clear in our solar system. All bodies including the Sun revolve around the instantaneous center of gravity of all bodies, a point called the barycenter.
The Earth is about 8 light-minutes from that point while Neptune is over 4 light-hours away.
The Sun is speeding in its orbit around the Milky Way but all bodies maintain this instantaneous barycenter at their ellipse's focus despite the motions of these bodies.
If gravity had a speed limit this observed stability is impossible.
There is no gravitational wave.
Relativity is wrong about gravity.
Geometry allows one to describe positions by defining a coordinate system.
On the Earth we can use a simple geometry using only two dimensions to describe positions, latitude and longitude. We agree where 0 degrees is for each plane so everyone can use this geometry.
On a flat map or on a globe we can place lines representing a value of latitude and of longitude.By sharing this common geometry we can share the values of lat and long to find a place on Earth.
It is critical to recognize these lines or this geometry (and its coordinate system) are not part of the Earth or physical space. The geometry is used only to describe positions using coordinates.
Relativity proposes the observer's geometry gets distorted by gravity, This change in geometry is not a change in physical space.
The Earth or the universe do not have a built-in geometry. We decide with the geometry selection how to describe positions.
Changes in the coordinate system are not changes in the space being described.
Relativity proposes a 4-dimensional coordinate system (or a defined geometry) including 3 for changes in linear positions (in a Euclidean geometry) and the 4th for a change in time.
Sometimes the combination of space and time can be called an event in spacetime. While an observer is stationary our accepted 'universal' time continues counting; it is silly to describe this scenario as a stationary observer moving in spacetime.
This spacetime, as the observer's reference frame, can be distorted by a gravitational field in relativity so what should have been a straight path (in the physical space) will be bent by the gravitational field for the observer when the observer is using coordinates for motion.
An observer on a charged body like a star which is moving can have its path affected by any of the the 3 major forces, gravity, electric, or magnetic, but spacetime uses only gravity as a force affecting the path.
This wrong simplification is a fundamental flaw.
This flaw has consequences. If only a gravitational field can affect motion, then both electric and magnetic fields are ignored. Cosmology based on relativity starts with this flaw. For example, the galactic magnetic field drives a spiral galaxy rotation so when the real cause is ignored then there is no alternative but to make up something that does not exist, called dark matter, to explain an observation. Relativity ignores critical forces.
5) based on an observer
All behaviors described by relativity involve the observer.
The universe has no built-in n-dimensional coordinate system. The definition of axes in the universe requires a fixed point in the universe to define the planes and the zero reference point for each dimension. There is no such fixed point so this coordinate system independent of an observer cannot be defined.
Our celestial coordinate system has two planes for declination and right ascension with the center of the earth as their fixed reference point. A third dimension in this geometry is the distance from Earth to the object.
Without a defined geometry at the level of the infinite universe, it is impossible to refer to any physical positions using coordinates without a defined geometry.
This limitation means relativity cannot refer to any position in the universe outside of an observer's reference frame. Positions in the universe (in relativity) are described only as distances from the observer's reference frame.
This limitation means relativity cannot describe any behaviors in the universe outside of an observer.
Unless an observer is with the light the light beam cannot bend around a distant galaxy due to a curved spacetime. Its path can bend only by observer's spacetime curvature when the observer is at this distant galaxy and in its gravitational field AND when the light is moving by using coordinates in the light's reference frame; light has no reference frame. Light travels in a straight line regardless of a coordinate system.
The claim for distant gravitational lensing is invalid.
The 1919 test with the solar eclipse was at the solar limb for maximum diffraction in the solar atmosphere.
Spacetime depends on an observer. Relativity and its observer dependent spacetime is limited as the basis for cosmology.
6) There is an additional flaw with relativity.
It allows the theoretical description of a black hole.
With a very large mass the spacetime for the observer in a non-inertial reference frame will curve extremely at that location down to a geometric point. A geometric point has no physical size, so this special point in spacetime is called a singularity where IF spacetime were real the mass resides within a volume of zero size meaning infinite density. This result is a violation of physics.
The black hole is present only to the observer whose spacetime is curved by that mass. No one else in the universe can see a specific black hole until in this object's gravitational field for their path's curvature.
The mistake of a black hole is allowed to persist in cosmology due to the dogma of relativity.
Other scientists have pointed out problems in the black hole theory and relativity.
The recent international collaboration to image the core of the M87 galaxy demonstrates the importance of finding a confirmation of relativity. Relativity is the foundation of cosmology and doubt is not tolerated.
Instead of an image of an accretion disk (expected for the assumed black hole), a torus or plasmoid was observed. Despite that discrepancy, relativity and its theoretical black hole remain unchallenged.
7) speed of light
Relativity assumes nothing can go faster than light.
That assumption was common in the late 1800's.
This is clearly a mistake. By the 1960's hydrogen atoms near a quasar were measured with an emission line shift in wavelength indicating the atom had a velocity faster than light.
Relativity with this assumed speed limit required the distortion of the observer's reference frame.
Near or at the velocity of light the observer's time must slow down (time dilation) and observed lengths must change so the observer maintains the illusion of not actually reaching this speed limit.
Spacetime was developed to address this problem with the speed of light as a limit, a mistake.
Claims of confirming a prediction by relativity always have an alternate explanation with classical physics.
Gravitational lensing was not confirmed in 1919 when light bending in the plasma in the atmosphere at the Sun's limb was the better explanation. Light from other stars, further from the limb, did not bend correctly for gravity.
General relativity is the foundation of modern cosmology and yet the theory has significant flaws.
I expect many in this group will be interested in considering whether a 1905 theory remains valid.
Quantum mechanics recognizes gravity as a force so QM has difficulty reconciling with spacetime.