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Earth lightning over water: discharge of several million volts
Photo: Jure Batagelj / 500px / Getty Images / 500px Prime
The crucial moment doesn't even last a second.
Scientists filmed and analyzed the birth of a lightning bolt between heaven and earth.
Strictly speaking, it's about the moment that causes enormous tensions between the ground and a thundercloud to discharge with a bright glow.
The analysis was based on images from Beijing by Rubin Jiang from the Chinese Academy of Sciences and his team.
In 2017, during a thunderstorm, they captured lightning bolts with a high-speed camera that captured an image every 2.6 microseconds.
As in the "Creation of Adam"
The experts were particularly interested in the point in time at which the downward, branching charge channels of a storm cloud and the upward charge channels on the ground come into contact and combine to form a lightning channel.
Experts also speak of the final jump.
According to the current analysis in the specialist magazine "Geophysical Research Letters", two individual charge channels from both directions are sufficient.
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Extremely slowed: the gif shows a time span of 0.00003 seconds (30 microseconds)
Photo: Jiang / Geophysical Research Letters / AGU
Researchers had previously speculated that under a thundercloud several charge channels might merge to form a large lightning conductor and then connect to those on the ground.
The procedure actually documented, however, is reminiscent of the two hands in Michelangelo's famous fresco depicting the creation of Adam, whose fingers approach from above and below.
The fingers are transferred to the lightning scenario, the charge channels directed upwards and downwards, between which there is a voltage.
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"The Creation of Adam" - fresco by Michelangelo
Photo: Michelangelo / Art Images / Getty Images
Objective: predict lightning strikes
Lightning between the ground and the sky occurs when negative charges form in a thundercloud and positive charges form on the ground.
The differences in charge create a voltage that is discharged in lightning.
Since air is not a good conductor, several million volts are required.
The charges in the cloud also electrify surrounding air molecules.
A light current flows, which moves forward several tens of meters in a few microseconds and branches out - these are the fingers.
New bursts of charge at the top let it grow further down.
According to the current evaluation, this continues until the tip of a finger comes close enough to a positively charged counterpart on the floor.
In the analyzed images, the strands of charge approach each other from below and above to a distance of 23 meters.
According to the experts, lighting up indicates contact.
Immediately afterwards it flashes violently (see GIF above).
The observation suggests that the first contact between the strands determines the route for the lightning, according to the researchers.
The string of weak charges then heated up in a flash and forms a plasma channel that can transport large quantities of charged particles between the cloud and the ground, i.e. lightning.
One question, however, remains: Since numerous, sometimes branching, downward-directed charge channels usually form under thunderstorm clouds, it is not yet possible to predict where the fusion will occur - and it is therefore still difficult to predict exactly where lightning will strike.
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