When astronomers observe distant galaxies, they can tell that most of them are moving away from one another. In addition, the more distant the galaxies, the more rapidly they are likely to be moving away from each other. Can you devise a hypothesis to explain these observations?

Understanding galactic redshift is key to unlocking the secrets of the cosmos. When we look at the light from distant galaxies, we notice a peculiar thing: the light is shifted more towards the red end of the spectrum than we would expect. This redshift happens because the universe is expanding, stretching the light waves along their journey towards us.

Think of it like a siren of an ambulance. As it moves away from you, the pitch seems to drop. In the same way, as galaxies move away, the wavelength of their light stretches out, becoming redder. This redshift gets larger the further away a galaxy is, which is a crucial piece of evidence for the Big Bang theory. It tells us just how fast a galaxy is receding from us, acting as a cosmic speedometer. Therefore, galactic redshift isn't just about color; it's about understanding the very fabric of the universe and its dynamic nature.

The idea of an expanding universe can be quite mind-boggling. Simply put, the universe is getting bigger every second, with galaxies moving away from each other as if they were on the surface of a balloon being inflated. This concept emerged from observing the aforesaid galactic redshift.

But, how do we know it's true? We've gathered evidence from various measurements, one being the redshift which indicates that most galaxies are not just moving randomly, but are receding from a common point of origin. This suggests that, once upon a time, the universe was much smaller, denser, and hotter. Over billions of years, this primordial speck has expanded to the vast cosmos we see today, and it's still growing. This notion of an ever-growing universe is one of the cornerstones of the Big Bang theory, offering our best explanation for the cosmic past and future.

Astronomical observations give us a window into the workings of the vast universe. Using powerful telescopes and advanced technology, astronomers collect data on stars, planets, and galaxies far beyond our own. The observations relating to galaxy movements and positions are particularly important in supporting the Big Bang theory.

For example, by measuring the light from galaxies and applying our knowledge of redshift, we can infer not only their speed but their direction of movement. These findings are consistent with what you would expect in a universe that started from a singular, dense state and has been expanding ever since. It's like detective work that spans across light-years, where we piece together the history of the universe from the clues that light brings us from afar. Astronomical observations, therefore, are not just about seeing into space—they are about unraveling the story of the cosmos from the beginning of time.