Decades: 590s - 600s - 610s - 620s - 630s - 640s - 650s - 660s - 670s - 680s - 690s
Years: 640 641 642 643 644 645 646 647 648 649 650
... Contents Dennis Gabor Dennis Gabor (Gábor Dénes) (1900-1979) was a Hungarian physicist. He invented holography in 1947, for which he ...