"Space" is the vast, near-empty expanse beyond Earth's atmosphere where planets, stars, and galaxies exist, while the "Universe" is the entirety of space, #time, matter, and energy, #encompassing #everything in existence. The Universe began with the Big Bang about 13.8 billion years ago and has been expanding ever since, #creating an "observable universe" that has a diameter of approximately 93 billion light-years.

Space

Definition: The expanse that exists beyond Earth's #atmosphere, containing very low levels of matter, making it a near-perfect #vacuum.

Contents: Contains predominantly hydrogen and helium plasma, along with electromagnetic #radiation, #cosmic rays, #magnetic fields, and dust.

Beginning: From Earth's perspective, space begins at the Kármán line, an #imaginary #boundary about 100 kilometers (62 miles) above sea #level.

The Universe

#Definition: Everything in existence—all space, time, matter, and energy—including #planets, stars, and #galaxies.

Origin and #Expansion: Emerged from the Big Bang #approximately 13.8 billion years ago and has been expanding ever #since.

#Observable Universe: The #portion of the universe that is currently visible to humans, which is about 93 billion light-years in #diameter, despite the universe's relatively young #age.

Contents: #Composed of about 4.9% ordinary (baryonic) matter, 26.8% dark matter, and 68.3% dark energy.

#Unknowns: The total size of the universe is not known and may be #infinite, and the true nature of dark #matter and dark #energy, which make up most of the universe, remains a mystery.

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