Light weighs nothing, but it does influence the weight of objects. Do we weigh less at night than during the day?
If we cast our shadow on a scale, it would not mark anything. Logically, a shadow weighs nothing. But what about the light? Technically, neither. But it does influence the weight of the objects.
It must be taken into account that, in reality, the weight of a person and an object is the force of attraction that our planet exerts on us towards its center. And it is the case that light is made up of photons that, although they do not have mass, do generate energy, pressing and pushing the bodies they hit, which contributes to increasing the effect of gravity, albeit imperceptibly. .
Obviously, that pressure is infinitesimal. It was the English physicist James Clerk Maxwell , who formulated in the 19th century the equations that predict the pressure of light, which were confirmed experimentally in 1903. And the result is that this force exerted by light is approximately 0.000000001 pounds, half of a billionth of a kilogram.
What follows from the above is that, if the light gives us, we will have an infinitesimally greater weight, than we would have being completely in the dark. Of course, that weight is negligible for individual people or objects. But the thing changes if it is about very extensive surfaces.
Chicago weighs about 140 kilos more during a sunny day than at night
Thus, it is calculated, for example, that a city the size of Chicago weighs about 140 kilos more during a sunny day than at night. And, it is estimated that the Iberian Peninsula is about 131 tons heavier during the day than after sunset.
And this curious phenomenon takes on even more importance in the case of space travel. For example, when the Japanese space probe Hayabusa approached the asteroid Itokawa in 2005, the pressure of the light was equal to 1% of the thrust of the probe’s engine, and had to be taken into account so that the spacecraft could orbit close to it. asteroid without problems.
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