Forest Moulton in 1900 had also shown that the nebular hypothesis was inconsistent with observations because of the angular momentum. Moulton and Chamberlin in 1904 originated the planetesimal hypothesis[10](see Chamberlin–Moulton planetesimal hypothesis). Along with many astronomers of the day they came to believe the pictures of "spiral nebulas" from the Lick Observatory were direct evidence of forming solar systems.