How do we know that the Universe is expanding?

In 1920 American Astronomer Edwin Hubble along with other’s discovered that the Universe is expanding. It’s funny that an 100 years have passed since then, and we still don’t know much about it. The galaxies beyond our Milky Way are moving away from us, and those farther from us are moving even faster. However it is not the Galaxies which are moving away, its the Space itself. Which means that there is no center to the Universe, or neither an edge. Everything in Space is moving away from each other. This expansion theory was pivotal in solidifying the fact that the Universe was indeed created from Big Bang. Earlier, Astrophysicists used to believe that the speed of expansion was somehow a constant. But decades of research and study have now revealed that the speed at which the Universe is expanding, is only accelerating with time, if it makes any sense.

We know that the Universe is atleast 14 Billion years old, we know it because that’s from how far light has traveled to Earth till date. But the aforesaid theory suggests that there may have been galaxies or star systems which have moved away from us so far, so quick, that light from them would never reach Earth, depriving us from witnessing their existence. Keep Reading