If the universe is expanding, what is it expanding into?

Theoretically, physicists from all over the world have been working to solve the mystery of the origin of our universe. Various Big Bang models have been developed over time. It is thought that the universe was initially an infinitely small ball (of zero radius) with an infinite density. As it began to heat up, it began to expand. Although scientists like Albert Einstein disagreed, several years later, several probes actually confirmed that the universe is expanding, and that it is doing so at an accelerating rate. However, because Big Bang was thought to be the beginning of everything, it was believed that there is nothing beyond it and that it is unnecessary to think about what existed before the big bang. Thus, even though there may be something beyond our universe, theore

The rate of expansion of the Universe is believed to be increasing based on the empirical studies of the supernovas. This means that the Universe will continue to expand infinitely. As the universe expands matter and energy will become increasingly spread out and diffused. Eventually matter will become so spread out that there will be no matter only energy. Energy will move to the lowest possible level where there is no usable energy left. The universe will have effectively ended.

"Expanding into" refers to the increasing distances between galaxies within the universe, while "expanding into" implies a space beyond the universe, which is not yet known or proven.