00:00Imagine you build the fastest spaceship ever conceived. Faster than any technology humanity
00:05has ever imagined. You leave Earth behind and begin a journey toward the edge of the universe.
00:10Day after day, year after year, century after century, you continue moving forward.
00:15But here's the question that has puzzled humanity for the universe have no edge at all.
00:20For most of human history, people believed the sky was a dome covering the Earth.
00:24Ancient civilization are fixed on a giant celestial sphere. Many believed there was nothing.
00:32But as our understanding grew, we discovered something astonishing.
00:39The Earth is not the center of the cosmos. Our planet orbits an ordinary star in the Milky Way.
00:45The Milky Way itself is only one galaxy among hundreds of billions more. Galaxies gather into
00:51clusters. Clusters connect into gigantic structures called the cosmic web.
00:55The universe is unimaginably vast, yet the mystery remains. Where does it end?
01:00To answer this question, we first need to understand something familiar.
01:08The Earth. If you start walking in one direction on Earth,
01:17Earth has no edge because its surface curves back onto itself. It is finite, yet unbounded.
01:30A revolutionary theory revealed that space is not empty nothingness. It is a dynamic fabric
01:36capable of bending under the influence of matter and energy.
01:41gravity is not merely a force pulling objects together. It is the bending of space-time itself.
01:51This discovery opened a stunning possibility. What if the universe itself is curved in a way similar
01:58to Earth's surface? Many people imagine the Big Bang as an explosion that happened at one location
02:06in empty space. But that's not what actually happened. The Big Bang was not an explosion in space. It was
02:16the expansion of space itself.
02:21Imagine raisins inside rising bread dough. As the dough expands, every raisin sees all the others moving away.
02:32The galaxies are like those raisins. The space between them continues stretching.
02:42This brings us to another important concept. The observable universe.
02:52Light travels at a finite speed. Because the universe has a finite age, we can only see a limited region.
03:02The observable universe is not the edge of the universe. It is simply the limit of what light has had
03:09time to reach us.
03:11If you traveled to another galaxy, that galaxy would have its own observable universe.
03:22The horizon moves with the observer.
03:27It is not a wall. This leads scientists to two major possibilities.
03:36First possibility. The universe may truly be infinite.
03:46If this is correct, then there is literally no edge. Because space extends forever.
03:58Second possibility. The universe may be finite, but curved.
04:06In this model, traveling far enough could eventually bring you back to your starting point.
04:17Scientists search for clues in the oldest light in the universe,
04:21known as the cosmic microwave background.
04:28Measurements suggest the universe appears remarkably flat.
04:36Flatness doesn't necessarily prove infinity.
04:39The universe could still be so enormous that its curvature is impossible for us to detect.
04:47Suppose you could travel forever.
04:53What would happen?
04:55You would continue encountering new galaxies,
04:58new stars, and new regions of space.
05:02The universe would keep revealing more of itself.
05:06So why does the universe have no edge?
05:08Because the universe is not like a room with walls. Or it may be curved in a way that eliminates
05:14boundaries entirely.
05:16Either way, every observation we have made points toward the same extraordinary conclusion.
05:22The universe does not appear to that you can reach.
05:25The greatest mystery is not what lies beyond the edge.
05:30The greatest mystery is that there may be no edge at all.
05:34It might be a medical condition.
05:34IfI select the universe somewhere, it really may not be a
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