How Many Helium Atoms Does it Take to Power a Lightbulb?
Tuesday 3 November 2026 at 21:57
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Edited by Richard Walker, Tuesday 3 November 2026 at 22:35
About 90% of the energy we use comes directly or indirectly from the Sun. Apart from solar panels, we have wind and hydroelectric power, which are ultimately driven by the effect of solar radiation on the climate, and burning of fossil fuels which are the remains of photosynthesis by plants that grew millions of year ago and stored up sunlight. And then there is combustion of wood and biowaste, but these too are stored sunlight.
The bulk of the energy generated in the Sun is from hydrogen atoms fusing together at high pressures and pressures to create helium atoms. In the process some mass is converted to energy according to Einstein's famous equation.
The fusion actually happens in three steps called the Proton-Proton Chain Reaction, with six hydrogens atomic mass 1 being input and one helium atomic mass 4 and two hydrogens emerging at the end. It's a bit more complicated but that is the gist.
Thinking about this I wondered if I could relate something we are all familiar with — powering a light bulb — to actual numbers of helium atoms being created in the sun.
How many helium atoms does it take to power a lightbulb?
Assuming a 10 w bulb, we need to find 10 Joules of energy each second (a Watt is one Joule per second by definition).
The creation of one helium 4 atom releases about Joules, so or around 2,500,000,000,000 helium atoms must be created per second.
How Many Helium Atoms Does it Take to Power a Lightbulb?
About 90% of the energy we use comes directly or indirectly from the Sun. Apart from solar panels, we have wind and hydroelectric power, which are ultimately driven by the effect of solar radiation on the climate, and burning of fossil fuels which are the remains of photosynthesis by plants that grew millions of year ago and stored up sunlight. And then there is combustion of wood and biowaste, but these too are stored sunlight.
The bulk of the energy generated in the Sun is from hydrogen atoms fusing together at high pressures and pressures to create helium atoms. In the process some mass is converted to energy according to Einstein's famous equation.
The fusion actually happens in three steps called the Proton-Proton Chain Reaction, with six hydrogens atomic mass 1 being input and one helium atomic mass 4 and two hydrogens emerging at the end. It's a bit more complicated but that is the gist.
Thinking about this I wondered if I could relate something we are all familiar with — powering a light bulb — to actual numbers of helium atoms being created in the sun.
How many helium atoms does it take to power a lightbulb?
Assuming a 10 w bulb, we need to find 10 Joules of energy each second (a Watt is one Joule per second by definition).
The creation of one helium 4 atom releases about Joules, so or around 2,500,000,000,000 helium atoms must be created per second.
Here's a (very) peripherally related joke.