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Language: en

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I'm on the 19th floor of One Canada Square in London

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and that is a GORGEOUS sunset .

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And soon the sun will dip below the horizon

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and it will be twilight.

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See, night doesn't technically start--

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at least under formal definitions --

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until the sun is 18° below the horizon.

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And until then, there are three types of twilight:

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First of all there is civil twilight,

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that's when the sky is still fairly light and you can walk about without worrying you're going to trip over something,

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that's 0° to 6° below the horizon.

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Next up is nautical twilight,

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that's when you can just about see the horizon against the sky if you're navigating on a boat,

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that's 6° to 12°.

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And finally there is astronomical twilight,

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where it's still just a little bit too light

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for the really faint objects like nebulae and galaxies

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to come out in the sky,

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that: 12° to 18°.

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And then finally, when the sun tips under that,

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then it formally becomes night.

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But the thing is in midsummer,

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when it's really really bright,

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when it's the sun, high in the sky

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the United Kingdom is north enough,

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that it never becomes night,

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that from evening to morning we are perpetually in twilight,

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until finally Autumn rolls around and we dip into night once again.

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America doesn't quite get it,

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Vancouver in Canada just stretches into that definition,

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but the whole of the UK,

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and of course a lot of northern Europe,

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well, we have entire seasons when we never ever technically have night.

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That is twilight,

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that is a really gorgeous sunset

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and that is something you might not have known.

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[Closed captions by MM
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