Stopped Clock Illusion

By Anupum Pant

When you quickly move your eyes to focus on the seconds hand of an analogue clock, have you ever noticed that the first second you see actually seems to linger for a slightly longer time? Yes, it does. And there’s a reason why it happens.

When you rapidly move eyeballs to focus from one point to the another, it’s called a Saccade. If you ever try doing this rapid movement with a camera, a motion blur occurs in between the first point focus and the last point focus.

Unlike cameras our eyes (work closely with the brain) has a built-in mechanism to erase this motion blur. The brain erases all the motion blur during those few milliseconds and replaces the motion blur frames with the final image in the end.

This is why you see the longer first second when you quickly focus your eyes on the seconds hand – the stopped clock illusion or chronostasis. This also explains why you can never see your eyeballs moving when you try to spot their movement while staring at your own eyes on a mirror.

Michael Stevens from Vsauce explains…

Concrete Cloth – Makes Durable Shelters Within Hours

By Anupum Pant

Today we have something which civil engineers would be extremely proud of – A recent innovation in concrete technology that has an immense life-changing potential – The concrete cloth; certainly a splendid engineering marvel.

What is it?

It is material which feels like a very thick canvas and has a three-dimensional fiber matrix. This piece of thick cloth is impregnated with a specially formulated concrete mixture. Once it is completely wet with water, it hardens into a thin, strong, fire-resistant and water-proof material, within a few hours. Commercial variants either have a hydrophobic coating on the outer surface or a PVC lining from the inside to make it completely impermeable to water.

Concrete Cloth

Since it just a thick piece of canvas impregnated with concrete, it can be transported fairly easily and can be made into various shapes to be used for different applications. For instance, it can be used for rapidly deploying hardened concrete shelters for people in need. It works like this:

  1. You carry a huge concrete canvas balloon with you in a truck.
  2. Place it wherever you need the shelter to be deployed.
  3. Pump water into it.
  4. Quickly start inflating it using a pump.
  5. Pull it around using, say a truck.
  6. Wait for it to harden.


  • To erect a shelter with concrete canvas, it only takes a fraction of the time taken to construct a shelter using tradition building techniques.
  • Unlike cloth tents, this one is extremely durable and can last for about 10 years. Moreover, it protects the residents from any form of extreme weather outside (Thermally insulated).
  • Construction material is light enough to be transported by a small pickup truck.
  • Requires just 2 people and can be deployed to a ready state within 24 hours – Within these 24 hours it gains about 80% of its full strength.
  • Can be tailored as required with the help of staples, cuts and nails / screws. In fact cutting it before hardening is not much different from cutting a thick piece of cloth.
  • Does not burn and is water-proof.
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