There is a related issue in quantum mechanics relating to whether systems have pre-existing – prior to measurement, that is – properties corresponding to measurements that could possibly be made on them. The assumption that they do is often referred to as "realism" in the literature, although it has been argued that the word "realism" is being used in a more restricted sense than philosophical realism. A recent experiment in the realm of quantum physics has been quoted as meaning that we have to "say goodbye" to realism, although the author of the paper states only that "we would [..] have to give up certain features of realism". These experiments demonstrate a puzzling relationship between the act of measurement and the system being measured, but it is unclear if they require a conscious observer or not.