There isn't a "newest" most common form of physical weathering. The most common forms of physical weathering have been around for a long time, and their relative prevalence depends on the specific environment.

Here are some of the most common forms of physical weathering:

* Frost Wedging: This process involves water freezing and expanding in cracks within rocks. The repeated freezing and thawing cycle widens the cracks, eventually breaking the rock apart. This is prevalent in areas with frequent freeze-thaw cycles.

* Thermal Expansion and Contraction: Rocks expand when heated and contract when cooled. In regions with extreme temperature fluctuations, this repeated expansion and contraction can cause stress within the rock, leading to fracturing.

* Abrasion: Rocks can be worn down by friction from windblown sand, glaciers, or moving water. This is common in deserts, glacial valleys, and riverbeds.

* Salt Wedging: Similar to frost wedging, salt crystals can grow in cracks within rocks, putting pressure on the rock and causing it to break. This is prevalent in coastal areas or areas with high salt content in the soil.

* Root Wedging: As tree roots grow, they can exert pressure on surrounding rocks, causing them to crack and break apart. This is common in areas with dense vegetation.

It's important to note that these processes can occur in various combinations and at different rates depending on the environment. For example, frost wedging is more prevalent in cold climates, while thermal expansion and contraction are more common in areas with large temperature swings.

So, while new research may reveal subtle variations in weathering processes, the fundamental mechanisms have been occurring for millions of years.