Lightning
Build charge → watch lightning strike. Builds on Electrostatic Potential.
A thunderstorm is building. Negative charge accumulates at the bottom of the cloud, and positive charge builds on the ground below. Finally, the voltage difference is too great and a lightning bolt connects cloud to ground. You see a brilliant flash.
The bright visible flash that you see — in which direction does it travel?
The bright flash travels UPWARD — from the ground to the cloud! Here’s the full sequence: first, an invisible ‘stepped leader’ of negative charge zig-zags down from the cloud in short bursts, ionizing a path through the air. When it gets close to the ground, a positive streamer reaches up to meet it. The instant they connect, a massive current surge — the return stroke — blasts upward from the ground at 100,000 km/s, lighting up the channel in a brilliant flash. That’s what you see.
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Watch the sequence in slow motion: the dim stepped leader branches downward from the cloud. When it reaches the ground, the brilliant return stroke races back up the channel. Use the speed slider to slow it down and see each phase. Toggle between real-time and slow-motion views.
E > 3 × 10⁶ V/m
When the electric field exceeds air’s breakdown threshold, electrons are ripped from molecules, creating a conducting plasma channel. The potential difference in a thunderstorm can reach 100–300 million volts.
A pointed metal rod on a rooftop creates a strong local electric field at the tip. This encourages the streamer to form there rather than on the building itself, guiding the return stroke safely through the rod to ground.
Above powerful thunderstorms, enormous red flashes called sprites and rings called elves illuminate the upper atmosphere at 50–90 km altitude — lightning’s exotic cousins, discovered only in 1989.
Ash particles colliding in volcanic plumes separate charge just like ice in thunderclouds. The result: spectacular lightning bolts inside eruption columns, following the same breakdown physics.
Scientists launch small rockets trailing grounded wires into thunderstorms to trigger lightning on demand. The wire provides a low-resistance path, and the return stroke follows it — allowing precise measurements.
“Lightning is nature’s most dramatic capacitor discharge: hundreds of millions of volts, thirty thousand degrees, and the flash goes UP. Every thunderstorm is an electrical circuit on a planetary scale.”
Lightning Generator
Control the conditions of a thunderstorm and trigger lightning on demand. Adjust the charge separation, humidity, and ground topology. Watch the full sequence unfold: charge buildup, stepped leader, streamer connection, and the brilliant return stroke. See the electric field intensify until breakdown occurs.
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Start by slowly increasing the cloud charge and watch the electric field between cloud and ground intensify (shown by the color map). When the field hits breakdown strength, the stepped leader begins its jagged descent — slow the animation to watch each step. Add a tall building or mountain and see how the geometry concentrates the field at the top, triggering lightning there first. Place a lightning rod and compare: the strike is guided safely to the rod. Try increasing humidity to lower the breakdown threshold. Finally, trigger multiple return strokes in rapid succession (most lightning flashes contain 3–4 strokes!) and watch the channel flicker.
Lightning is a two-step process: the invisible leader builds the road, and the brilliant return stroke drives on it. The electric field must exceed ~3 MV/m for breakdown — and geometry matters enormously. Pointed objects and tall structures concentrate the field, determining where lightning strikes. It’s not random — it’s physics.