Do the fundamental constants of nature vary in spacetime?

One of the limitations of currently accepted physical theory, the Standard model of particle physics, arises due to our lack of understanding of the fundamental constants. The purpose of this thesis is to test the variability of one such constant, the fine-structure constant α, by measuring its relative deviation, ∆α/α, from the current value on Earth. For this purpose ∆α/α was measured in a total of 23 absorption systems, towards four quasars, using UVES/VLT and HIRES/Keck spectra. This almost doubled the number of reliable measurements and almost tripled the precision in the weighted mean result −1.0 ± 0.4stat ± 0.4sys parts per million.