in 1929 the american astronomer edwin hubble made a groundbreaking discovery. he confirmed early observations that the light from distant galaxies is more redshifted than the light from closer ones. that means that distant objects are moving away from us faster than the closer ones. this led hubble to conclude that the universe is expanding. it all started around 14000000000 years ago with a big bang and ever since the universe has been growing all of its mass with all of its gravitational pull couldn't overpower the force of the expansion of the galaxies that formed continue to grow further and further apart like the raisins in a rising. the rate of expansion is known as the hubble constant it's such a key concept in cosmology we want to know it as precisely as possible the european space agency's planck satellite measured radiation from the early universe and determined that for every megaparsecs or 3300000 light years further away a galaxy is it's receding 6070 kilometers per 2nd faster but more recently the hubble space telescope examined nearby galaxies an