Final answer:
The discovery of the universe's expansion began with Vesto M. Slipher's studies of spiral nebulae at Lowell Observatory and was further propelled by the use of Type Ia supernovae as standard candles, revealing an unexpected acceleration in the expansion. Technological advancements in spectroscopy and large telescopes have been central to these discoveries, which have profound implications for cosmology and our understanding of dark matter.
Step-by-step explanation:
Discovery of the Universe's Expansion
The discovery that the universe is expanding was one of the most significant astronomical findings of all time. Initially, Vesto M. Slipher's pioneering observations at Lowell Observatory, originally intended to search for life and other solar systems, led to the study of the spectra of spiral nebulae. This study coincided with advances in spectroscopy and the use of large telescopes. It was through detailed examination of these spectra and subsequent redshift observations that the expansion of the universe was inferred.
Furthermore, the surprising discovery using Type Ia supernovae as standard candles provided insight into the rate of expansion of the universe billions of years ago. It revealed that, contrary to expectations based on gravitational effects, the expansion was not decelerating but accelerating. This had deep cosmological implications, necessitating new theories such as dark energy to explain the observations. The “standard bulb” property of Type Ia supernovae has been indispensable in measuring distances to extremely distant galaxies, thus illuminating the acceleration of the universe's expansion over time.
These findings have ushered in a data-rich era for astronomy with ongoing research continuing to reshape our understanding of the universe's expansion and its ultimate fate. Such insights have also contributed to the contemporary discussions on topics like dark matter and the universe's closure. What began with a quest to understand distant galaxies has led to questioning the very nature of the cosmos itself.