Impact Winter: light as a commodity

For those unfamiliar,

An impact winter is a hypothesized period of prolonged cold weather due to the impact of a large asteroid or comet on the Earth's surface. (Wikipedia)

In my world I want light and light sources to be a commodity. This means that the atmosphere must be sufficiently dense such that light and heat radiation from the sun does not reach the Earth's surface.

Do we know how large a meteor would have to be to kick up enough debris and dust to crowd the atmosphere to this effect?

For reference: the meteor that is thought to have extinguished the dinosaurs was about six miles wide. But I'm not sure just how dense this impact made the atmosphere.

posted over 8 years ago

socrates‭

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