Soft things include kittens, pillows, and sweaters right out of the dryer, but also clouds, ice cream, and airplane landings. When Gizmodo came up with their latest Ask Giz column, they consulted different experts and mainly got a discussion as to how the question is impossible to answer. John E. Hayes of the Sensory Evaluation Center at Pennsylvania State University said,
Softness is fundamentally a perception (a percept). This implies it occurs in the brain, which in turn means that it can only be measured with a human assessor. With any human sensory system, there are limits of detection, both at the high end and low end, and outside these limits, we cannot tell (perceive) a difference, even if a machine or instrument might. Consider the hardness of cut glass and a cut diamond—when we touch them with our fingertip, they each depress our skin (and the mechanoreceptors in our skin) by roughly the same amount, so we cannot tell them apart, even if a lab instrument could.
But still, most came up with a possible answer, depending on how you define the question. Read their thoughts at Gizmodo.
(Image credit: Benjamin Currie/Gizmodo)