The Universe encompasses the totality of all space, time, matter, and energy. Most scientists believe it began approximately 13.8 billion years ago in a rapid expansion called the Big Bang, which marked the simultaneous birth of space and time. Since that moment, the universe has been continuously expanding, and recent observations show this expansion is actually accelerating due to a mysterious force known as dark energy, which makes up about 68% of the cosmos. Interestingly, all the stars, planets, and galaxies we can see account for less than 5% of the universe’s total composition. The remainder consists of dark energy and dark matter, an invisible substance that acts as a gravitational “glue” holding galaxies together. While the observable universe is a sphere about 93 billion light-years in diameter, the true size of the entire universe remains one of science’s greatest unknowns
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