Why do we yawn?

Like many of us, you probably think that people yawn when they are hungry or tired. Actually, this is not exactly true! After many studies, all scientists do not explain this phenomena the same way.

A whole family happily yawning together

Yawn to make our brain colder

One of those theories is the one of Dean Falk, an anthropologist. He think that we yawn for make our brain colder. Indeed, when we are tired our brain is warmer than its normal temperature. But as a computer, the brain work better when it is not too warm. When we yawn, air go into us by our nostrils and our mouth, making the blood in our head colder, and so our brain colder. It is also a good way to be more concentrated and attentive.

It has been thought that yawning increased the level of oxygen in the body, but studies have shown that is wrong. Indeed, we do not yawn more when we do sport, whereas it is exactly the moment when our body need more oxygen.

Yawn to be under less stress

It allows to relax face muscles and breath deeply. It is by the way recommended to voluntary yawn through the day, especially when you feel stressed, tired or upset.

Yawn is contagious

Scientists discovered that this phenomena concerns only humans and primates, but when you see someone yawn, you will probably yawn too. Maybe even just by reading this text, you are likely to yawn yourselves. However, some people are less susceptible to contagious yawning than others. It depends on our capability of empathy. The more you demonstrate empathy, the more you are susceptible to contagious yawning.

You can check how susceptible to contagious yawning you are by watching this video!

Did you know?

On average, we yawn around 240 000 time in our lives. We yawn even as fetuses, in our mother's wombs. Moreover, all mammals yawn.

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Why are rugby balls egg-shaped?

It could be surprising but first rugby balls were round. Rugby balls have become egg-shaped 50 years later!

An example of beautiful egg-shaped rugby ball

How was the rugby invented?

In 1823, while a football match at the college of Rugby, a town in United Kingdom close to Birmingham, William Webb Ellis, one of the students, grabbed the ball with his hands to drive it into the opponent goal.

The ball provided from the Rugby's shoemaker, William Gilbert who used inflated pork bladders to create it. The ball was still round.

What is the point of an egg-shaped ball?

In 1840, William Gilbert invented egg-shaped balls to avoid that slipped through rugby player's hands, especially when it rained, by wrapping inflated pork bladders with leather.

How the Gilbert's ball became the reference?

However, in 1846, the rugby game rules are officially determined, form and size of the ball are not specified. We have to wait until 1877, to see the egg-shaped ball officially adopted by the Rugby Football Union. Gilbert’s ball was exported firstly to Australia, New Zealand and South Africa, then all over the world. It even became the regulatory standard.

In 1930, rugby balls were changed again to make it more handy for players and more impressive for spectators. Indeed, the more the ball is egg-shaped, the less its trajectory can be calculated.

So now, the length of a rugby ball should be between 280mm to 300mm, the length circumference 740mm to 770mm and the width circumference is 580mm to 620mm. But there are also different sizes for children and women.

Gilbert' s ball is still the reference of rugby ball, it is even use for international competition like the World Cup.

Did you know?

Rugby has only featured in the Olympics four times: 1900, 1908, 1920 and 1924, and US Olympic rugby team is the most successful (won in both 1920 and 1924).

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Why do we have different time zones around the world?

If you have already traveled, you probably know that the time is different according the country you are in. You can even save time by travelling!

For example: if your flight leaves Paris at 10am, he will be in New York at 11am, local time. However, your flight would have lasted in reality 7 hours and have crossed 6 different time zones.

Different time according their own time zone

Until 1891, each town determined its own time according sun’s position. But when industrialization appeared, this method became obsolete. Early in the 20^th century, coordinated universal time was created. From the point of reference of Greenwich, a London’s suburb, 24 different time zones which equally split Earth were created.

Let's check them here:

A world time zone map

Source: timeanddate.com 

Each state has to choose its own according sun’s position and other criteria mentioned below!

Historical reasons

During World War II, Germany imposed its time to France, then to show his support to Nazi, General Franco changed Spain’s time zone. To be coordinated with its ally, United Kingdom also changed its time zone. After the war, London get back its original time zone, but both France and Spain kept the German’s time zone. That is why there is still a time lag of 1 hour between those countries.

Economic reasons

The International Date Line crosses Pacific Ocean and creates some weird situations. For example, the Saoma islands which were aligned with United States’ time zone in 1894, changed to the one of Australia and China because they had not enough days in common with those both last countries to do business with them.

Political reasons

5 time zones cross China, but the government chose the one of Beijing as reference. It is communists’ wishes which are in power since 1946.

Environmental reasons

Time change has been created to saves energy. But for some countries, it is still confused. In Australia, lands are free to decide doing time change or not.

Thus, there is not only 24 time zones through the world in reality but 37, and even 43 when we take into account time change. But when time zones didn’t exist, there were around 300 different time zones, just through the North of America!

Finally, we are making progress :)

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