The concept of an expanding universe can be tricky to grasp, but it’s essential to understanding our place in the cosmos. Unlike baking a loaf of bread or a batch of muffins, where dough expands into a pan, the universe doesn’t have a physical container to expand into.
Consider this analogy: if you’re standing at the North Pole and asked which direction is farther north, there’s no clear answer. Similarly, the universe’s expansion can feel like a brain teaser because we can’t experience it directly in our daily lives.
To better understand the expanding universe, scientists track other galaxies moving away from ours. By measuring this rate of expansion, they can imagine the universe expanding without a physical boundary. This concept is supported by observations of galaxy movements and was first proposed by physicist Alexander Friedman in 1922.
However, the more we learn about the universe’s expansion, the more questions arise. What drives this acceleration? Scientists have dubbed this phenomenon “dark energy,” which makes up approximately 68% of the universe’s total energy content. The remaining 32% consists of everyday matter.
While researchers can’t directly measure dark energy, models suggest it might be responsible for the universe’s accelerating expansion. One major challenge facing scientists is reconciling quantum mechanics and gravity, two fundamental forces that govern different scales of physics.
Some theories propose the existence of multiple universes or alternate dimensions, which could help explain these discrepancies. The multiverse theory attempts to bridge the gap between quantum mechanics and gravity by proposing a vast array of parallel universes with unique physical laws.
Source: https://www.sciencealert.com/a-physicist-explains-how-to-imagine-the-universes-mind-bending-expansion