Civil twilight: the sun is between 0 and 6 degrees below the horizon
Nautical twilight: the sun is between 6 and 12 degrees below the horizon
Astronomical twilight: the sun is between 12 and 18 degrees below the horizon
I believe if the sun is lower than 18 degrees below the horizon, all sun rays can no longer reach your location. Hence it is completely ...
chlorophyll is green because that was the part of the spectrum that was left when plants evolved. The bulk of the spectrum was already being harvested by other photosynthetic life. there is actually a wide variety of photosynthetic pigments chlorophyll is just one of many. You may want to check out the purple earth hypothesis.
To ask why chlorophyll is green is a bit like asking why haemoglobin is red. That is just the colour of them, in the case of haemoglobin due to the iron content and in the case of chlorophyll probably due to the magnesium atom at the centre of every chlorophyll molecule. As you very likely know, the function of chlorophyll is to carry out photosynthesis, ...
From an human eye perspective.
Civil twilight=you will be able to read a newspaper.
Nautical twilight=you will be able to see the contours of mountains and the brightest stars will be visible.
Astronomical twilight=you will no longer be able to see the contours of mountains and the atmosphere will have a very dark color,lots of stars are visible.
In general, REE minerals tend to be fluorescent. In our lab we deal a lot with REE and we have a UV lamp just for fun, to see the colours. Other minerals that are commonly associated with REE deposits are also fluorescent, with the best example being calcite, fluorite, and apatite.
The fluorescent properties of REE-bearing solid state ...
I think the answer to your question have to be no.
Lots of minerals are fluorescent in UV light,You can take a look here https://geology.com/articles/fluorescent-minerals/
So as you can see in the linked summary of fluorescent minerals it can be hard to tell what you have found unless you know what to look for.
A better way to find Rare Earth Elements ...
Twilight occurs when the sun is just slightly below the horizon. You cannot see the sun but light will still be available due to atmospheric processes. The different stages of twilight depend on the angle of the sun to the horizon leading to different degrees of darkness.
Down all day just means that the sun will never pass the horizon. But twilight may ...