Quantum theory supposes that observation affects reality. Experimental evidence for this theory was published in Nature in 1998 discussing that a beam of electrons was affected by the act of being observed.

A readable popular science summary from ScienceDirect can be found here.

Buks, E., Schuster, R., Heiblum, M., Mahalu, D., & Umansky, V. (1998). Dephasing in electron interference by a ‘which-path’detector. Nature, 391(6670), 871.