Jakarta –
In the 1960s to 1970s, the US and the USSR conducted a number of nuclear tests, including underground. Even though it destroys the environment and can trigger Earth’s temperature like in an ice age, it turns out that nuclear explosions are of no use. Scientists use it to study the Earth’s core.
Of course there is no direct way to see the Earth’s core. The deepest hole ever dug by humans, can only reach 12,263 meters, still far from breaking through the Earth’s crust to the layer below. However, we can see beneath the surface quite effectively by exploiting earthquakes in a technique called seismic tomography.
When an earthquake occurs, including those caused by underground nuclear explosions, waves of energy are sent out in all directions. By measuring the vibrations of multiple locations on the surface, scientists can create a map of Earth’s interior. Because the rocks and fluids inside the Earth have different densities, waves travel through them at different speeds, allowing geologists to know what kind of material the waves are traveling through.
Scientists had proposed in the 1990s that Earth’s core rotates faster than the rest of the planet’s crust. In the 2022 study, researchers from the University of Southern California (USC) used wave data from the Large Aperture Seismic Array (LASA) in Montana collected during Soviet underground nuclear bomb tests on the Arctic archipelago of Novaya Zemlya from 1971- 1974.
Using a technique they developed, they found that the core rotates more slowly than previously thought, about 0.1 degrees per year.
The team then looked at data from tests conducted by the US near Alaska in 1969 and 1971, and found that the inner core was reversed, sub-rotating (i.e. slower than the surface) at least a tenth of a degree per year.
“The idea that the inner core is oscillating is a model that’s out there, but researchers’ opinions are divided on whether it’s feasible,” said Professor of Earth Sciences at USC John E. Vidale quoted from IFL Science.
“We did this expecting to see the same direction and rate of rotation in the previous atomic test pair, but instead we saw the opposite. We were quite surprised to find that it was moving the other way.”
According to the team, the oscillations can explain fluctuations in the length of Earth’s day, which vary by about plus or minus 0.2 seconds on a six-year cycle.
“From our findings, we can see a shift in the Earth’s surface compared to its inner core, as people have been suggesting for 20 years,” said Vidale.
“However, our recent observations show that the inner core rotated slightly slower from 1969-1971 and then moved in the other direction from 1971-1974. We also note that the length of the day grows and contracts as predicted. The coincidence of the two observations makes the oscillations become possible interpretations,” he explained.
The length of Earth’s day varies more than one might assume, unless we keep an eye on the clock very accurately. There are many factors that affect the rotational speed, such as changes in sea level and earthquakes, although the biggest factor is that the Moon is moving away from Earth, as the two bodies interact. The result is that Earth slows down, albeit with occasional bursts of speed. This research shows that the inner core is also a factor in the length of our days.
“The inner core isn’t fixed, it moves under our feet, and it seems to be back and forth a few kilometers every six years,” Vidale added.
“One of the questions we’re trying to answer is, does the inner core move progressively or is it mostly locked in comparison to others in the long term? We’re trying to understand how the inner core forms and how it moves over time, this is an important step for better understand this process.
Watch the video “There’s an Atomic Bomb and a Nuclear Bomb, What’s the Difference?”
(rns/rns)
2023-08-04 09:10:30
#Underground #Nuclear #Explosion #Terrible
