During the early stages of the universe, specifically the first 300,000 years after the Big Bang, the universe was extremely hot and dense. At this time, the universe was filled with a plasma of particles, including photons, electrons, and atomic nuclei, interacting with each other through electromagnetic and other fundamental forces.
According to our current understanding of physics, as described by the theory of relativity, time is not an absolute quantity but rather a dynamic aspect of spacetime. The theory of relativity tells us that time is influenced by the presence of mass and energy. In the early universe, as the density and energy were extremely high, the effects of relativity become significant.
During this period, the expansion of the universe caused the wavelengths of photons to stretch, resulting in a phenomenon called cosmological redshift. As the universe expanded, the wavelengths of photons increased, causing their energy to decrease. This process is linked to the concept of cosmic microwave background radiation, which is the remnant radiation from the early universe that we can observe today.
In terms of the perception of time, due to the high energy and density of the early universe, the passage of time was influenced by the physical conditions prevailing at that time. The intense interactions among particles and the expansion of the universe would have affected the flow of time, but it's important to note that our understanding of time breaks down at extremely high energies and densities.
As for whether the first 300,000 years of the universe were longer than 300,000 years now, it's not accurate to make a direct comparison. The passage of time itself is a relative concept, and it's difficult to compare time scales between different periods of the universe's history. The conditions and physical laws governing the universe have changed significantly over its vast timescale, and direct comparisons become challenging.