A Physicist Explains How to Visualize the Universe’s Astonishing Expansion

When you bake a loaf of bread or a batch of muffins, you place the dough in a pan. As it bakes, the dough expands into the pan, causing any chocolate chips or blueberries to spread farther apart.

In some ways, the Universe’s expansion is similar. However, there’s a key difference: while dough expands into a pan, the Universe has nothing to expand into. It expands within itself.

This concept can be puzzling because the Universe, by definition, includes everything. There’s no pan—just dough. Even if there were a pan, it would be part of the Universe and would expand with it.

As a physics and astronomy professor who’s studied the Universe for years, I understand how difficult this idea can be to grasp. You don’t experience anything like this in daily life. It’s akin to asking which direction is farther north of the North Pole.

To help visualize the expansion, think about how galaxies move away from our own, the Milky Way. Scientists track these movements to define the rate of the Universe’s expansion, allowing them to imagine expansion without needing something to expand into.

The Big Bang: The Universe’s Rapid Expansion 13.8 Billion Years Ago

The Universe began 13.8 billion years ago with the Big Bang, an event that wasn’t an explosion but a rapid expansion from a dense, hot singularity. This expansion—called inflation—caused every point in the Universe to move outward.

Afterward, the Universe condensed and cooled, leading to the formation of matter and light. Over time, it evolved into the Universe we know today.

In 1922, physicist Alexander Friedman first proposed that the Universe could expand. Later, Edwin Hubble confirmed this by showing that galaxies were moving away from the Milky Way. In 1929, he revealed that not only was the Universe expanding, but its expansion rate was accelerating.

This accelerating expansion remains a mystery. Scientists still struggle to explain how the Universe can overcome gravity’s pull and expand at an increasing rate. To visualize this, they often use the “expansion funnel” model, where the narrow end represents the Universe’s beginning and the widening funnel illustrates its expansion.

Dark Energy: The Mysterious Force Driving the Universe’s Accelerating Expand

The energy behind this accelerating expansion is called dark energy. Though scientists can’t measure or observe it directly, they estimate dark energy makes up about 68% of the Universe’s total energy. In contrast, ordinary matter accounts for just 5%.

But what lies beyond the expanding Universe? Currently, scientists have no evidence of anything beyond our known Universe. However, some propose the existence of multiple Universes, which could help resolve issues in current models of our Universe.

One challenge is reconciling quantum mechanics, which governs the small-scale world, with gravity, which operates on a large scale. In the quantum world, objects behave probabilistically and can come in and out of existence. In classical mechanics, objects behave predictably, without such fluctuations.

These two realms don’t fit together easily. Some theories, like string theory and multiverse models, attempt to bridge this gap, suggesting that multiple Universes might explain how gravity and quantum mechanics could coexist.

Regardless of these theories, the Universe will continue to expand, with galaxies growing farther apart over time.

Read Original Article: Science Alert

Read More: Scitke