Halton Arp showed examples of high redshift and low redshift galaxies
doing this.
I visited that link -- lots of pictures of people having line-of-sight fun with the Leaning Tower of Pisa.
About Halton Arp, many of his supporters consider him a martyr because he got denied telescope time or something like that. But being martyred is not evidence for the truth of one's theories.
(icebear on relativity...)
What icebear mentioned is a version of the Twin Paradox. The solution involves a counterintuitive feature of relativity. It's that the time between two space-time points is relative, in the way that their spatial separation is relative. That relativity of time is VERY tiny by ordinary standards, but it can get large in elementary-particle experiments.
The usual claim is 95%. Claiming 25% would be much worse, i.e. it would make the person making the claim look much dopier.
That's about 25% dark matter and 70% dark energy.
Dark matter and dark energy are two very different sorts of entities. We only know them from their gravitational effects, but that's enough to find their equations of state.
Dark matter: (pressure) ~ 10
-6 * (density)*c
2Dark energy: (pressure) ~ - (density)*c
2
The dark-matter pressure is from its velocity dispersion.
The dark-energy pressure would be an exact equality for the cosmological constant.
Again gravity is by 40 orders of magnitude th eweaket force in nature. Asking gravity to hold galaxies together is like wanting the littlest kid in the school to compete in the power-lifting event.
Between individual elementary particles, yes. But gravity has an edge over all other known interactions: its "charge" is always positive, and its range is effectively infinite. That makes it cumulative and long-distance.
One can test gravity over the sizes of the Earth and the Sun by doing structure calculations with estimated compositions. They do reasonably well at predicting various observed features, so we can be confident that one can extrapolate from laboratory scales to the Earth's and the Sun's sizes.
For larger size scales, one watches the planets and smaller objects, and sends out spacecraft. One finds that one can extrapolate gravity to the size of the Solar System.
One doesn't have as much data on other stars, but their structure calculations also work. Also, binary stars have Keplerian orbits, like many Solar-System objects, Keplerian orbits with Solar-System size scales.
Going to larger scales is more difficult, though the density profiles of star clusters could give some hints on the behavior of gravity at their size scales.
Electromagnetism is much like gravity, except that its charges can be zero and negative as well as positive. In our Universe, neutrons have zero charge to high accuracy and protons and electrons opposite charges to high accuracy. Furthermore, the Universe is electrically neutral, as far as we can determine.
The relative charges of the electron, proton, and neutron are likely a consequence of some Grand Unified Theory, and that gives us a hint as to why the Universe is neutral. If the Universe originated as a quantum fluctuation, it likely originated as a GUT gauge singlet. This means:
(Gauge-symmetry generators).(Universe) = 0
The electric charge is the only surviving low-energy one, so
(Electric charge).(Universe) = 0
The other interactions have very short ranges, due to confinement (QCD) or symmetry breaking (electroweak, SUSY?, GUT?, TOE?).
) - that "material" is "being held in a straight line until some point at which the field breaks down".