Who has told you, that Big Bang must be repeatable?!
You don’t understand what
@Altfish and
@ChristineM meant by “repeatable”, questfortruth.
It meant observations, which come in the forms of evidence or tests (eg test result that provide measurements as data, in the experiments).
In the case, of the Big Bang, which you have brought up, astrophysicists in the 1920s, 1948 and 80s & 90s, formulated both explanations and predictions that fulfilled the requirements of being “observed”.
In the 1920s, both Howard Percy Robertson (1924-25) and Georges Lemaître (1927) have predicted that the Redshifts can be used to determine if two distant objects (eg 2 galaxies) were moving away from each other, by looking at and comparing the absorption lines of the wavelengths, to see if wavelengths have lengthened or shortened.
If the comparisons of absorption lines showed the wavelengths have shift towards red end of spectrum, then it is “redshifted”, which is an indication that objects are moving towards each other, hence expansion.
But if these absorption lines have shift toward the blue end of spectrum, then it is “blueshifted”, an indicator that objects are towards each other, hence contraction.
The measurements of Redshifts can be used with the Hubble Law, to calculate the distance (normally given in Astronomical Unit (AU) instead of light year) between observed object (eg galaxy, nebula, star, etc) and the Observer.
Such measurements provide evidence for the expanding universe model (which was later called the Big Bang theory in 1949), and in 1929, Edwin Hubble made the discovery.
Redshifts are important measurements even to this day, in astronomy, and used by hundreds of observatories, as well as space observatories, since the first discovery. Hence, REPEATABILITY of observations, since the original 1920s predictions of Robertson and Lemaître, have been made.
Later, in 1948, a team of astrophysicists (George Gamow, Ralph Alpher and Robert Herman) explain the hot and young beginning of the universe, and Gamow and Alpher predicted the Big Bang Nucleosynthesis (BBN) and Alpher and Herman predicted the Cosmic Microwave Background Radiation (CMBR).
Both predictions are related to the formations of matters or atomic nuclei of the lightest atoms available (eg hydrogen, deuterium and helium nuclei) when the universe was young:
- without electrons bonded to the nuclei in the BBN prediction,
- with electrons bonded to nuclei in the CMBR prediction.
When the electrons bonded with ionized atoms for the first time, the hydrogen, deuterium and helium became electrically neutral, 377,000 years after the Big Bang (known as the Recombination Epoch). At the same time, the universe was cool enough for photons to travel freely in transparent space, AND it caused residual heat signatures (temperature) that can be measured from the highly redshifted cosmic background radiation.
CMBR are the earliest photons that can be observed, which is older than lights from the earliest quasars and earliest stars.
CMBR was later discovered in 1964 by Arno Penzias and Robert Wilson, who were setting up radio telescope.
Since then, other radio telescopes including space observatories like COBE, more recent WMAP and Planck spacecraft were able to map space for CMBR, at higher resolution. Hence, repeatability of the observation.
It was 1964 discovery is what turn the Big Bang model from “Hypothesis” into officially accepted “Scientific Theory”.
Then there was in 1980s, a more recent contribution to the Big Bang theory, the ΛCDM model (Lambda-CDM model). The Greek letter Λ stands for “Dark Energy”, while CDM is abbreviation for “Cold Dark Matter”.
Part of premises made in this newer model, is the prediction that the universe is not only still EXPANDING, but the expansion has also “accelerated”.
Now, I know there are lot of skeptics about the existence of Dark Matter and Dark Energy, but the observation of Type 1a Supernova in 1998, confirmed that the universe was indeed accelerating in its expansion.
Since 1998, other observations confirmed the prediction that the acceleration of the expansion. Hence, the observation meet REPEATABILITY requirements.
Observation don’t just mean “seeing with the eye” observation. Observation can include detecting, measuring and testing unseen phenomena, using devices that can detect and measure.
Like for instance, multimeters can detect electricity, and measure the current, voltage, power and resistance in electrical components or wiring. Meteorologists have various equipments designed to measure not only temperature, but also measure humidity, air pressures, wind speed, etc.
In medical science, genetics, any biology-related fields, and even in forensics, we cannot observe and measure with eyesight because some things are too small to see, so they relied on various techniques and technology to check blood samples, semen samples, and other specimens, for testings, eg illnesses, diseases, sugar levels, cholesterol levels, DNA, etc.
In astronomy, we not only have optical telescopes to view distant objects from visible light spectrum, but also from infrared, ultraviolet, microwave, x-ray and gamma-ray wavelengths in radio astronomy. We cannot see neutrinos, but we can measure them coming from the sun, or from other stars.
We use all sorts of technology of devices and equipment that can observe/detect, measure and test, repeatedly, which our eyesight, hearing and touch cannot perceive. We also used computers that do calculations at higher speed and with higher precision.
We can use technology to assist with research, investigation and testing, to find/discover evidence.
You really need to understand what science means by repeatable.
