For tens of thousands of years, humans have looked upward and tried to find meaning in what they see in the sky. Since Aristotle began systematically recording the motions of the planets and formulating the first models of the universe, there have been over 2350 years of scientific study of the sky. The earliest scientists explained their observations with the Earth-centered universe model and little more than two millennia later we now live in an age where we are beginning to characterize exoplanets and systematically probing the evolution of the universe from its earliest moments to the present day.
Human understanding of the universe has leapt forward incrementally with each new technology. Firstly with improvements in the methods of observing with the naked eye and the recording of observations, then, over 400 years ago with Galileo and the first telescopes. There followed a continuing constant evolution to larger collecting surfaces. Larger lenses and much larger mirrors were developed and within the last 150 years the use of photographic plates and spectroscopy coupled with improved mechanical tracking allowed huge advances. The sphere of the observable universe increased to distances and times when the universe was considerably younger than today.
A mechanical rendering of the Palomar 200" telescope from Russel Porter. Courtesy of Caltech Archives and Special Collections.
The Palomar 200” Hale telescope was designed when the scale of the universe and its expansion were new discoveries. It was the largest in the world when it was built in 1949 with a mirror that collected four times more light than the largest existing telescope. The two Keck telescopes were also the worldʻs largest telescopes when they were built in the 1990s. Their large mirrors each collected four times more light than the Hale and demonstrated the validity of the segmented-mirror approach TMT is using to provide a nearly 10-fold increase in light gathering power compared to Keck.
TMT comes into existence in similar circumstances as did the Hale 200”. The scientific parallels of these telescopes are striking with the recent understanding of precision cosmology and the abundance of exoplanets echoing the then recent understanding of the scale and expansion of the universe that preceded the Hale. From early estimates of the Hubble constant to explorations of dark matter and energy; from characterizing the range of stellar abundances to observing the first population of extremely metal poor stars; from identifying the first quasars to exploring the earliest formation of galaxies and the role of black holes in their formation; TMT will carry on the grand tradition of technical, scientific advancement and leadership for the next 50 years.
