Jump to content Main menu Main menu move to sidebar hide Navigation Main page Contents Current events Random article About Wikipedia Contact us Donate Contribute Help Learn to edit Community portal Recent changes Upload file Languages Language links are at the top of the page across from the title. Search Create account Log in Personal tools Create account Log in Pages for logged out editors learn more Contributions Talk CentralNotice move to sidebar hide (Top) 1 Origin and history of the idea 2 Original thought experiment 3 Criticism and development 4 Recent progress 5 Applications 6 Experimental work 7 As metaphor 8 See also 9 Notes 10 References 11 External links Toggle the table of co...