1. Starchy Surface: Pasta is coated in starch which swells on contact with water.

2. Glassy center: The starch on the surface of pasta forms a glassy layer when hydrated. This layer protects the pasta's interior from overcooking.

3. Al Dente: This point is reached when the glassy center is almost completely hydrated, giving pasta a slight resistance when bitten.

Factors affecting cooking time:

- Pasta shape: Different shapes have different surface areas, affecting water absorption.

- Pasta thickness: Thicker pasta takes longer to cook.

- Water temperature: Higher temperatures speed up cooking.

- Salt: Salt in water helps pasta absorb water faster.

How physics describes al dente:

* Glass transition: The glassy center transforms into a rubbery state during hydration. The right cooking time catches pasta at the edge of this transition.

* Starch gelatinization: As pasta cooks, starch granules absorb water and swell, giving pasta its texture. Al dente is reached when starch gelatinization is optimal.

* Diffusion: Heat and water diffuse into the pasta, causing the starch to gelatinize. The rate of diffusion determines cooking time.

Physics helps optimize cooking methods for perfect al dente pasta.