In the absence of air, a penny and a feather dropped from the same height at the same time will fall at the same speed relative to each other.

Here's why:

* Gravity's Constant Acceleration: The only force acting on both objects in a vacuum is gravity. Gravity accelerates all objects at the same rate, regardless of their mass or shape. This means the penny and the feather will accelerate downwards at the same rate.

* No Air Resistance: In a vacuum, there's no air resistance to slow the feather down. Air resistance is what typically makes a feather fall much slower than a penny in normal conditions.

Therefore, in the absence of air, the penny and the feather will fall side-by-side, reaching the ground simultaneously. This was famously demonstrated by astronaut David Scott on the moon, where the lack of atmosphere allowed a hammer and a feather to fall at the same rate.