Atoms are incredibly tiny, too small to be seen by the naked eye or even a regular microscope. We know they exist through several lines of indirect and direct evidence. One of the earliest and strongest evidences comes from Brownian motion, observed by Robert Brown in 1827. He noticed pollen grains suspended in water moving randomly due to collisions with invisible molecules—atoms and molecules—which was later explained thoroughly by Albert Einstein. This motion gave a way to measure the size of atoms indirectly by the statistical impact of countless tiny collisions.
Further proof came with advances in technology. Electron microscopes, which use electron beams with much shorter wavelengths than visible light, allowed humans to visualize atoms for the first time. These microscopes can scatter electrons off atoms to create images, thus providing direct visual evidence of atomic structure.
In addition, many other scientific observations and experiments throughout history, such as chemical reactions, spectroscopy, and X-ray crystallography, support the atomic theory by explaining the behavior of matter based on atoms.
In summary, the existence of atoms is confirmed by:
- Observable effects like Brownian motion showing the impact of invisible particles (atoms) on visible particles,
- Direct imaging using advanced electron microscopes,
- Consistent experimental evidence from physics and chemistry explaining matter's properties through atomic theory.
