How Big Is the Universe?

How Big Is the Universe?

The universe is, as far as observations allow us to say, at least about 93 billion light-years across in diameter for the observable universe. That does not mean the whole universe is only that size; it means light has had a finite time to reach us since the Big Bang, so there is a limit…

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The Discovery of the Expanding Universe

The night sky has fascinated humanity for millennia, inspiring both wonder and scientific inquiry. Over time, astronomers unraveled the vast tapestry of stars, nebulae, and distant galaxies, gradually uncovering the dynamic nature of the cosmos. The journey toward understanding the expanding universe represents one of the most profound leaps in modern cosmology, reshaping our perception…

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How NASA Prepares for Planetary Defense

Planetary defense is a critical field of research and engineering dedicated to protecting Earth from the potential hazard posed by small bodies in our Solar System. By combining advanced observations, sophisticated modeling, and ambitious space missions, space agencies like NASA aim to detect, characterize, and, if necessary, deflect threatening objects before they can cause significant…

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