Why matter is not empty space

 The discovery of nuclear atomic structure came from Ernest Rutherford's gold foil experiment (1909-1911), conducted with Hans Geiger and Ernest Marsden at the University of Manchester.

The Experiment

Rutherford's team fired alpha particles (helium nuclei) at an extremely thin gold foil—only about 400 atoms thick. They expected the particles to pass through with minimal deflection, based on J.J. Thomson's prevailing "plum pudding model" which envisioned atoms as diffuse positive charge with electrons embedded throughout.

Instead, they observed:

• Most alpha particles passed straight through (as expected)
• Some deflected at small angles
• Astonishingly, about 1 in 8,000 bounced back at angles greater than 90°

Rutherford famously remarked this was "as if you fired a 15-inch shell at a piece of tissue paper and it came back and hit you." This led him to propose that atoms have a tiny, dense, positively-charged nucleus containing most of the atom's mass, with electrons orbiting at relatively vast distances.

Why Atoms Aren't Actually Empty

While the nucleus occupies only about 1/100,000th of an atom's volume, atoms are far from empty space:

Electron probability clouds: Electrons aren't tiny particles orbiting like planets. Quantum mechanics shows they exist as probability distributions—electron clouds or orbitals—that genuinely occupy the entire atomic volume. The electron is "everywhere" in its orbital simultaneously until measured.

Electromagnetic fields: The entire atomic volume is permeated by intense electromagnetic fields from the nucleus and electrons. These fields are physical entities carrying energy and momentum.

Pauli exclusion principle: This quantum principle prevents atoms from collapsing or passing through each other. When atoms approach, their electron clouds overlap, and the exclusion principle creates powerful repulsive forces—this is what you feel as "solidity" when touching objects.

Virtual particles: Quantum field theory reveals that "empty" space teems with virtual particle-antiparticle pairs constantly appearing and annihilating. The quantum vacuum is an active, energetic medium.

The "emptiness" metaphor only works if you imagine electrons as classical point particles, which they're not. The atom is better understood as a dense quantum system where fields and probability distributions fill the entire volume.