15 seconds ...

Quantum mechanics proves beyond a shadow of a doubt there is no certitude. When researchers delve into the notion of superposition, reality itself becomes questionable at best, something in concert with how our eyes and brain keep us from going truly live in an existence we will never fully understand.

Everything You See Is From 15 Seconds in the Past, New Research Claims

And that's probably the reason why our vision doesn't constantly make us throw up.

"Instead of analysing every single visual snapshot, we perceive in a given moment an average of what we saw in the past 15 seconds," the authors note in a piece published in The Conversation, a website where scientists routinely detail their latest work. "So, by pulling together objects to appear more similar to each other, our brain tricks us into perceiving a stable environment. Living 'in the past' can explain why we do not notice subtle changes that occur over time."

As the researchers put it in their paper:

Retinal images continuously fluctuate because of many sources of internal and external noise ranging from retinal image motion, occlusions and discontinuities, lighting changes, and perspective changes, among many other sources of noise. However, the objects do not appear to jitter, fluctuate, or change identity from moment to moment.

As an experiment, track your finger with your eyes, notice how smooth the motion is. Now, try to move your eyes without tracking something. Not smooth is it? This is something yours truly has noticed for years but never knew why this is so until now. :)

The image below shows why certitude is but an illusion.

Figure 1: Classically, a particle is bound in the central region C if its energy E is less than V0, but in quantum theory the particle may tunnel through the potential barrier and escape.