“There are so many people who are arguing or fighting over issues which don’t have much relevance. We must all realise it is not worth it. It’s like being in the whirlpools which are always present behind a little rock near a river. We seem to be living in these little whirlpools and forget that there is a whole river. The picture is much bigger.” -Kalpana Chawla
Throughout history, a number of advances have enabled astronomers to collect superior data about the Universe. Smoother mirrors, adaptive optics, superior instrumentation, and optimized photon collection have all made significant contributions, but at some point, you simply have no choice but to go bigger. Doubling the size of your primary mirror doubles your resolution and quadruples your light-gathering power, so bigger is always better. In the mid-2020s, the Extremely Large Telescope (ELT) will be completed, surpassing everything.
At 39 meters in diameter, the ELT will be made up of 798 hexagonal segments, each one an impressive 1.4 meters from corner-to-corner. The smoothness of the surface will be a ridiculous 7.5 nanometers, with a resolving power capable of scientific advances the world has never seen. But just as impressive is the technical achievement of making, assembling, and configuring the mirrors. To make the largest, most accurate telescope the world has ever seen means creating something with unprecedented precision.