7 What causes the sound of thunder?

We found out why lightning looks the way it does. Now, what causes that rumbling, thunder sound? When the negative charge of the clouds connects with the positive charge of the ground, you witness the lightning flash. This lightning flash heats the air surrounding it to a temperature of about 50,000° F, making the air three times hotter than the Sun’s surface.

The hot gases surrounding the discharge experience a sudden increase in pressure. This pressure could be about a hundred times the normal atmospheric pressure. This causes the compressed air to explode, resulting in a shock wave, and so we hear a loud, booming noise. The shock wave nearer to the ground is what you hear first, followed by the shock waves from higher up. The compressed air rapidly expands and contracts, causing tubular vibrations around the channel, creating the rumbling sounds of thunder. (1, 2, 3)

8 Why do we experience a falling sensation in our sleep?

Hypnagogia is the transition between wakefulness and light sleep during which hallucinations like floating, being bigger or smaller than yourself, or falling may occur. The falling sensation in sleep is a universal experience, and it is often experienced during the transition from wakefulness and light sleep when the body relaxes to prepare for sleep. When the body reaches deep relaxation, the brain misinterprets it as the body falling and jerks you awake.

A part of the brain called the reticular activating system controls our basic functions but ventrolateral preoptic nucleus, near the optic nerve, dictates tiredness. When we are falling asleep, the reticular activating system releases control of the body and the ventrolateral preoptic nucleus takes over but this process may not be smooth which causes the remaining wakeful energy to surface and result in jerky movements. This is called the hypnic jerk, and it knocks you back into consciousness.

Some theories state that this was a reflex which helped in the survival of our ancestors. The falling sensation has also been interpreted as a symbol that shows if a person is feeling vulnerable or fearful about a certain aspect of their life. (source)

9 How do whales and dolphins sleep without drowning?

Dolphins and whales cannot breathe underwater like fishes. They are marine mammals that need to reach the surface to breathe, and they do not have involuntary breathing reflexes like humans. If these mammals sleep like humans and go into a deep unconscious state, then they will most likely suffocate and drown. So how do they sleep without drowning?

A brilliant answer to this is that these mammals shut one eye at a time and allow the other half of the brain to fall asleep. Sleeping with one eye open and one half of their brain awake helps them to control their breathing and also keep a watch out for any dangers. They alternate between the two halves of the brain so they can get the rest they need. This sleep is called “uni-hemispheric sleep,” wherein one brain hemisphere sleeps at a time.

Other advantages, like being able to hold in their breath for longer and having high tolerance towards carbon dioxide in their system when compared to other mammals, also play a role.

(1, 2)

10 Why does burping after drinking soda cause a burning sensation?

We have all burped after drinking a fizzy soft drink, and if you’re that person who goes around saying they don’t burp, don’t lie! Our burp is usually followed by a stinging sensation in our nose and throat, but have you ever wondered why that is?

According to research from the University of South California, carbonated drinks activate a particular cell that serves as pain sensors in the nasal cavity. This is similar to what happens when you eat something spicy, like mustard or horseradish, but only at a lower intensity. The cells that responded to the carbon dioxide were the same ones that detected spices.

The burning sensation comes from a set of nerves responding to the sensations of pain, skin pressure, and temperature in the nose and mouth. So, even when we know soda induces pain, why we continue drinking it is still a mystery. (1, 2)

11 Why is it easier to carry a person than a similarly heavy, inanimate object?

To understand this, we need to understand the center of gravity. The Center of gravity is the average location of the weight of an object. The center of gravity is fixed in inanimate objects. For a symmetrical object, it is likely to be at the center of the object, but the same does not apply for nonsymmetrical objects.

In humans, the center of gravity changes depending on their age, weight, height, and the position of their body. And unlike inanimate objects, humans can adjust their center of gravity accordingly. For example, when you carry a person, the person might adjust their center of gravity by putting their arms around the neck or by not bending their legs to make it easier for you to carry them.

But with deadweight objects, the center of gravity is fixed, and so lifting them seems harder. The same goes for unconscious people. Their center of gravity will be in the default position, making it harder for you to carry them. (source)

12 Why do ships and aircraft have circular windows instead of square ones?

Both ships and aircraft need to withstand a stark difference in pressure and temperature caused by external and internal forces. Believe it or not, square windows existed in airplanes once upon a time, but it was discovered that these windows were responsible for a few fatal crashes.

The presence of the four corners created a weak spot and was detrimental to the structural integrity. The sharp corners concentrate more stress and experience two to three times more stress than the rest of the cabin, causing a structural weakness.

This was avoided by curving the windows. Circular windows help distribute the stress equally and maintain the structural integrity of either a ship or aircraft. Circular shapes are stronger and can resist deformation easily. Therefore, circular windows help maintain structural integrity under extreme differences in pressure in aircraft and can withstand the pressure of storm waves in ships. (1, 2)