Final answer:
Albert Einstein believed the movement of pollen grains was due to the random collisions with water molecules, a concept known as Brownian motion, providing indirect evidence for the existence of atoms. This phenomenon was later confirmed by Jean-Baptiste Perrin, solidifying the theory and contributing to the calculation of Avogadro's number.
Step-by-step explanation:
Albert Einstein attributed the erratic movement of pollen grains observed under a microscope to the phenomenon now known as Brownian motion. He believed that this motion was caused by the statistical fluctuations in the number of water molecules colliding with the pollen grains. This random thermal motion results in sporadic paths of the visible particles as they get hit unevenly from different sides.
Hypothesis:
Einstein proposed that the movement of the grains was not due to the living organisms inside, but rather resulted from the collisions with water molecules, which pointed to the existence of atoms and molecules.
Observation:
Under a microscope, small particles in fluid, such as pollen grains in water, exhibited complex paths due to the fluctuating impacts from water molecule collisions.
Conclusion:
Albert Einstein concluded that the movement observed was a direct result of fluctuations at the molecular level. This provided nearly direct evidence for the existence of atoms. Jean-Baptiste Perrin later confirmed Einstein's theory and used it to accurately calculate sizes of atoms and molecules, contributing to the establishment of Avogadro's number.