There is a natural phenomenon behind it: that is why airplanes reach the speed of sound

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There is no doubt that flying is the fastest conventional way to travel. But an airplane does not always fly at the same speed. The flight from Switzerland to the US takes over an hour longer than the return journey. That was not the case in recent days. According to CNN, eastbound transatlantic flights saved an average of an hour off the scheduled flight time. Thanks to the jet stream.

People usually talk about ‘the’ jet stream, even though there are several. These are wind tunnels that extend all over the world at an altitude of eight to twelve kilometers. They are the strongest natural winds and can reach speeds of almost 500 km/h.

Like all winds, jet streams are created by differences in pressure or temperature. For example, at the equator, air heated by stronger solar radiation rises, and at the poles, cold air sinks. An imbalance arises, which is balanced by the wind. The greater the temperature difference, the stronger the wind. As the Earth rotates, these winds are deflected eastward, creating our jet streams.

There are two major jet streams in the Northern and Southern Hemispheres: the Polar Front and the Subtropical Jet Stream. They swing around the Earth from west to east and change with the position of the sun. The polar front jet stream is the most important jet stream for Europe. Depending on the location of the polar front, it runs through the Northern Hemisphere between 40 degrees and 60 degrees north or south latitude. The subtropical jet stream over the subtropical high-pressure belt is in the range of 20 to 30 degrees north latitude. It is weaker than the polar jet stream and often only occurs during the relevant winter months.

The reason for the current top speeds is a cold snap in the US. This increase in temperature gradient has increased the speed of the jet streams in the Northern Hemisphere, sometimes causing them to reach the speed of sound. But the low pressure area that was previously over the US has now arrived in Europe, meaning the amplifying effect has disappeared.

According to CNN, Emirates Flight 222 from Dallas to Dubai reached approximately 750 mph. This is close to the speed of sound. However, unlike the legendary supersonic Concorde, these aircraft did not break the sound barrier.

The speed of sound is the speed at which sound waves propagate. The speed of sound generally depends on the medium and its temperature. The speed of sound in air that is 20 degrees warm is about 1234 km/hour. However, in water that is ten degrees cold, the sound is four times faster. At a general altitude of about eleven kilometers in temperatures of minus 55 degrees, the speed of sound is almost 1080 km/h.

There are two speeds to consider: ground speed and relative speed in flight. When there is no wind, both are the same. When flying in the jet stream, the wind speed must be subtracted or added to the speed observed on the ground – depending on the tail or headwind. This gives you the actual flight speed. In the case of the Emirates flight, the ground speed is 1250 km/h, but the actual airspeed is “only” just under 1000 km/h, so the sound barrier is far from broken. (keg)

Source: Blick