[katieHaylor (OP)]

Roger says:

Given that the universe started with the big bang, an infinitesimally small and dense point, expanding to create the elements, can the universe be considered to be completely symmetrical and uniform? Would the influences on matter be completely equal during the expansion? If not, what caused the initial variances?

What do you think?

[PmbPhy]

Roger says:

Given that the universe started with the big bang, an infinitesimally small and dense point, expanding to create the elements, can the universe be considered to be completely symmetrical and uniform? Would the influences on matter be completely equal during the expansion? If not, what caused the initial variances?

What do you think?

No. The universe is not completely symmetrical. If it were then galaxies, stars, planets and life could never have existed. There is quantum mechanics to consider and that won't allow for a symmetrical universe.

[evan_au]

Would the influences on matter be completely equal during the expansion? If not, what caused the initial variances?

On very large scales, the universe is extremely uniform; studies of the Cosmic Background Microwave Radiation show that the temperature of the universe is the same in all directions to within 1 part in 100,000.
Physicists think these small temperature variations came about due to quantum fluctuations in the early universe. Studying this slightly splotchy map of the sky has allowed cosmologists to estimate the composition of the early universe.
See: https://en.wikipedia.org/wiki/Cosmic_microwave_background#Features

[PmbPhy]

Would the influences on matter be completely equal during the expansion? If not, what caused the initial variances?

On very large scales, the universe is extremely uniform; studies of the Cosmic Background Microwave Radiation show that the temperature of the universe is the same in all directions to within 1 part in 100,000.
Physicists think these small temperature variations came about due to quantum fluctuations in the early universe. Studying this slightly splotchy map of the sky has allowed cosmologists to estimate the composition of the early universe.
See: https://en.wikipedia.org/wiki/Cosmic_microwave_background#Features

Evan is speaking about the cosmological principle which refers to the large scale structure of the universe. This principle states that on very large scales the universe is both uniform and isotropic. Recent observations show this principle to be questionable. See: https://en.wikipedia.org/wiki/Cosmological_principle

Caution: This principle is based on the portion of the universe that we can see. We have no knowledge of the portions of the universe that we can't see and we never will. Therefore the cosmological principle can never be verified. Its an extrapolation. Karl Popper was the one who originally noted this.

While the universe is quite uniform on extremely large scales )250 million light years) it is quite non-uniform on the small scale, i.e. stellar and galactic scale. If not then stars and thus life would not exist in the universe.