If the universe is already infinite, what is it growing into?

You place the dough in a pan to bake a loaf of bread or a batch of muffins. The dough expands into the baking pan while it bakes in the oven. The expansion of the muffin batter causes any blueberries or chocolate chips to become further separated from one another.

In certain respects, the universe's expansion is comparable. However, this analogy is flawed since the cosmos has nothing into which to expand, whereas the dough expands into the baking pan. It simply enlarges into itself.

The universe is thought of as everything within the universe, which may sound like a brainteaser. There is no pan in the expanding universe. Only dough. Even if there were a pan, it would still expand with it as it is a part of the cosmos.

These concepts are difficult to understand, even for me, a physics and astronomy professor who has spent years studying the cosmos. This is not something you encounter on a daily basis. It's similar to asking which way is farther north of the North Pole.

Considering the motion of other galaxies away from the Milky method is another method to consider the expansion of the cosmos. Because they can follow other galaxies as they separate from our own, scientists are able to determine that the universe is expanding. The rate at which other galaxies move away from us is used to describe expansion. They can envision expansion using this concept without requiring a source of expansion.

The universe's expansion

The Big Bang occurred 13.8 billion years ago, marking the beginning of the cosmos. According to the Big Bang theory, the cosmos began as a hot, dense singularity. This small spot abruptly experienced inflation, a rapid expansion in which the universe as a whole expanded outward. However, the Big Bang moniker is deceptive. It wasn't as the name implies, a massive explosion, but a period of rapid cosmic expansion

Then, as the cosmos rapidly cooled and compacted, matter and light began to form. It eventually developed into the cosmos that we know today.

The physicist Alexander Friedman initially proposed the theory that our cosmos was dynamic and might be growing or decreasing in 1922. He provided mathematical evidence for the universe's expansion.

Edwin Hubble investigated the expansion rate in further detail, but Friedman demonstrated that the cosmos was expanding, at least in certain places. Hubble published his seminal study in 1929, confirming that the entire universe was expanding and that the rate of expansion was increasing, although many other scientists also established that other galaxies were moving away from the Milky Way.

Astrophysicists are still perplexed by this discovery. What phenomenon enables the cosmos to expand by drawing items in the universe apart while simultaneously overcoming the force of gravity that holds it together? In addition to all of that, its rate of expansion is increasing over time.

To illustrate how the universe's expansion has accelerated since the Big Bang, many physicists employ a graphic known as the expansion funnel. Consider a wide-brimmed, deep funnel. The beginning of the universe is symbolised by the narrow end on the left side of the funnel. You are travelling forward in time as you approach the right. The expansion of the universe is symbolised by the cone widening.

The source of the energy driving this accelerated expansion has not been directly measured by scientists. They are unable to measure it or detect it. They refer to this kind of energy as "dark energy" as it is invisible and impossible to quantify.

Models developed by physicists indicate that dark energy, which accounts for roughly 68% of the universe's total energy, must be the most prevalent type of energy. Just under 5% of all energy is derived by ordinary stuff, which includes the Earth, the Sun, and everything else that is visible to us.

There is no proof from scientists that there is anything outside of the known cosmos. There may be more than one universe, according to certain predictions. Some of the issues scientists face with the present models of our universe might be resolved by a model that incorporates multiple universes.

One of the main issues with modern physics is that scientists are unable to reconcile gravity, which rules large-scale physics, with quantum mechanics, which explains how physics functions on a very small scale.

The small-scale behaviour of matter is determined by quantised, or fixed, amounts of energy and probability. Things can enter and exit existence at this size. Matter is capable of wave-like behaviour. The quantum realm differs greatly from our perception of reality.

At vast scales, or what physicists refer to as classical mechanics, things behave as we would anticipate them to on a daily basis. Things can have constant amounts of energy since they are not quantised. Things don't just appear and disappear.

Energy in the quantum realm just has an on/off switch, much like a light switch. All degrees of energy are permitted by the world we see and engage with, which functions similarly to a dimmer switch.

However, when scientists attempt to investigate gravity at the quantum level, they encounter difficulties. Physicists would have to postulate that gravity is quantised at the microscopic scale. However, such theory is not supported by the studies that many of them have done.

The multiverse theory is one approach to bringing various notions together. The interplay between gravity and the quantum realm is explained by a variety of ideas that extend beyond the existing universe. Among the most prominent theories are loop quantum theory, brane cosmology, string theory, and numerous others.