The speed of rotation of the Earth around its axis depends on various factors, and has changed several times during the history of the planet. For example, 3.5 billion years ago the Earth rotated much faster than it does now, but with the advent of the Moon, the rotation speed began to decrease. Thanks to this, cyanobacteria were able to fill the atmosphere with oxygen, since they had more time to do this during daylight hours. Now scientists believe that the day on Earth may become even longer, but now the reason for this will not be the Moon, but the inner solid core of the planet, which consists of iron and nickel, and has a diameter comparable to the Moon.
Scientists predict an increase in the length of the day. Image source: spacegid.com
What's happening to the Earth's core
The inner core is located at a depth of 4,800 kilometers, it is hotter than the Sun, but remains solid. Surrounding it is the outer core – a super-hot layer of molten metals. Detailed information about the structure of our planet began to emerge relatively recently – about 40 years ago, when researchers began mapping the Earth's interior based on records of seismic activity. We have already told you that by the way seismic waves propagate in the bowels of the planet, scientists can draw conclusions about what materials they are made of.
Then scientists first discovered that the speed of rotation of the inner core around its axis is different from the rotation speed of the rest of the planet. It was spinning a little faster. However, according to the results of the latest study, the situation began to change since 2010. For some reason, the rotation speed of the inner core began to decrease. As a result, it now rotates even slower than the mantle and crust. Researchers report this in the journal Nature.
The inner core began to rotate slower than the outer layers. Photo source: www.bbc.com
Earth's rotation may slow down
According to scientists, if the rotation speed of the inner core continues to slow down, its gravitational pull will eventually lead to a slowdown in the rotation speed of the outer layers. That is, the Earth will begin to rotate more slowly than it does now, which will lead to an increase in the length of the day.
True, you are unlikely to notice this, since we are still talking about thousandths of a second. Therefore, most likely, people will not have to change calendars or the length of the day. True, everything may change if the rotation speed of the inner core begins to slow down even more, which also cannot be completely ruled out.
Slowing down the rotation speed of the inner core is called «reset». Photo source: livescience.com
Why is the Earth's core slowing down
This is not the first time that scientists have noticed that the Earth's inner core is slowing down. This phenomenon was even given a name – “return”. It has been discussed for the last ten years, but it is very difficult to prove. In a new study, to confirm the existence of the return, scientists used data from more than 100 earthquakes that occurred in the same place.
The earthquakes occurred along a tectonic plate boundary in the South Sandwich Islands, which are located in the Atlantic Ocean. Earthquakes occurred between 1991 and 2023. Each seismic event made it possible to determine the position of the core relative to the mantle. By comparing these data, scientists were able to discover that the rotation speed of the core changes downward over time.
This study is the most convincing evidence yet of the core slowing down. However, the reason for this phenomenon is still unclear. Scientists suggest that it is due to “stirring of the surrounding liquid iron core.” But it is also quite possible that the inner core is slowing down due to dense regions of the rocky mantle, which have strong gravitational forces. That is, they can serve as a gravitational “brake,” just as the Moon once did for the Earth.
Scientists obtain information about the inner core using seismographs. Photo source: ru.123rf.com
It is also not yet clear at what moments the core slows down. It is possible that the core periodically slows down and then speeds up. These changes can occur over decades or even longer. Therefore, in order to draw conclusions, long observations are necessary.
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Finally, we note that the inner core is one of the most mysterious layers of our planet. And although scientists have recently been able to find out quite a lot of information about it, and even learned that it is younger than the planet itself, much still remains a mystery.