He is an expert in astrophysics, and his research is highly valued around the world.

He is an expert in applied physics.

He understands the importance of learning.

He is majoring in psychology.

Gaku is my best friend.

He has a deep interest in archaeology.

Weak interaction is one of the four fundamental forces between elementary particles.

Strong interaction is one of the four fundamental forces in particle physics.

Electromagnetic interaction is one of the fundamental forces used to explain the force between substances.

Gravitational interaction creates attraction between objects.