11 How can mobile phones make “emergency calls” when there’s no network coverage?

The two most annoying things that cause frustration to mobile users are “low battery” and “no network coverage.” When you are calling someone, your call gets connected via the network coverage offered by your service provider.

When pressing the call button, your phone releases a signal which is detected by the nearest network tower. The signal is then transmitted to the receiver’s tower, and finally, you are able to reach the person. Have you ever imagined how an emergency call goes through even during the absence of network coverage?

It is the general assumption that emergency calls can go through without a network, but it’s not true. SIM cards usually work on Global System for Mobile (GSM) technology. The GSM technology enables the utilization of signals from the nearest tower even when provided by another network service provider.

This mechanism of using another network service provider’s tower facilities enables a user to make emergency calls. In some countries including the United States, it is possible to make an emergency call even with a dysfunctional SIM card.

This is facilitated by the antennae that are present on your mobile phones. The antenna connects to the nearest tower rather than your SIM card. (source)

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12 Why does the plastic turn white when you bend it?

Polymers, like plastic, turn white when they experience stress by color-change reactions known as “stress-induced crystallization.” It is a known fact that many polymers are semi-crystalline (neatly ordered) and amorphous (unordered).

When plastic is bent, the polymer chains start rearranging themselves according to the direction in which it is bent. The polymer chains get closely packed and aligned during the reorientation phase.

When the white color appears on top of the plastic, this is due to the elongation of the polymer chain on the top side. If the color change is observed on the reverse, this is due to elongation of the chain on the bottom side.

If the process is repeated a couple of times, the plastic breaks due to repeated stress induced on the polymer chain. If the polymer chain is tangled, then the plastic can further be elongated. It is important to check how polymers perform under stress in order to make good-quality products. (source)

13 In a cup of coffee, why does the top of the liquid leave a stain ring, whereas the rest of the liquid does not?

If you are a coffee lover, you would have noticed that your favorite liquid leaves a circular stain on the top of the mug. Have you wondered why this occurs? Well, we have the answer for you. Based on a study published in the science journal Nature, researchers were able to determine the movement of particles.

The particles in coffee move towards their perimeter forming a dense ring around the edge of the liquid. When coffee evaporates, these particles do not evaporate and stay in the same place. The particles also tend to remain in the same place when the volume of the coffee decreases.

In another study, the researchers were able to determine that the shape of the coffee particle is spherical. These particles tend to spread easily towards the edges when compared to other shapes. (source)

14 Why is it when you rub your eyes for long enough, you begin to see shapes, grids, and other stuff?

Everyone has experienced a weird display of fuzzy colors, swirling visuals, and checkerboards after squishing your eyes. Why does this occur? Scientists have identified this phenomenon as “phosphenes.” One experiences light sensations without the light actually entering into the eye. This commonly arises due to pressure phosphene.

The human eyeball is comprised of many types of neurons called “retinal ganglion.” It is responsible for receiving the visual information from the light-sensitive photoreceptors cells in the retina. However, it can also be activated by applying pressure on the eyeball and tricks the eyeballs into activating a similar phenomenon. (source)

15 Why do pen caps have holes in them?

One of the most common thing which we notice on a day-to-day is the hole on top of the pen caps, but why do they have them? The pen caps have holes in them to prevent suffocation in case they were swallowed accidentally.

According to various reports, pen caps are considered to be the most common thing swallowed by children. This can cause potential choking and prove to be fatal. Pen caps with holes were designed to allow passage of air through the holes if they are accidentally swallowed by children.

After knowing the reason behind it, pen caps can be considered superheroes in disguise. (source)