Transcription
um that the idea that the universe is expanding um sounds sounds almost philosophical at first, like something inferred rather than than observed. But in reality, it comes from direct measurements of light itself.
Um, when we look at distant galaxies, we don't just see where they are. We we analyze the light they emit. And that light carries a a kind of fingerprint, a pattern of lines that tells us which elements are present. Uh, what we find is that almost all distant galaxies have those fingerprints shifted toward the red end of the spectrum.
This effect, called redshift, tells us that the light waves have been stretched while traveling through space, which only happens if the space between us and the galaxy has expanded. The farther away a galaxy is, the more its light is stretched, which means the faster it's moving away from us. And remarkably, this relationship is is consistent in every direction we look.
Um, that tells us it's not galaxies flying through space away from a central point, and it's space itself expanding everywhere at once. And when you rewind that expansion backward in time using the laws of physics, you arrive at a universe that was once hotter, denser, and much smaller than it is today.