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Good Question ‘Reply All’: Leaf Colors, Sirens & Tin Foil

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(credit: CBS) Heather Brown
Heather Brown loves to put her innate curiosity to work to answer yo...
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MINNEAPOLIS (WCCO) – We’ve all seen the beautiful leaves out there. But how exactly do they change colors?

That’s just one of the Good Questions you e-mailed us this week. Now back to leaves…

Leaf color comes from pigments: chlorophyll (green), carotenoids (yellow, orange and brown) and anthocyanins (red).

All the trees have the green and yellow/brown pigments in them, it’s just the chorophyll covers the carotenoid. But when there’s less sunlight out as the days get shorter, leaves stop producing chorophyll and the yellow/brown pigment shines through.

As for the red, anthocyanins are only produced in the fall and only in certain trees — like the oaks or the maples — and only under certain weather conditions. That’s why we don’t see the brilliant red every year.

Shawn asked: How loud are storm sirens?

I talked with the folks at Hennepin County emergency management and they said there are more than 250 sirens in the county. There are about a dozen different kinds of them, some older than others. The loudest sirens are 127 decibels at 100 feet — drums, loudest ever human scream, a marching band — and that can cause hearing loss. The quieter ones, and there are only a few of them, are 100 decibels at 100 feet – that’s like a blow dryer or subway train. There’s always the challenge of balancing ear damage with making sure people can hear.

Matt from Minneapolis wants to know: Why doesn’t tin foil get hot?

If you put your tin foil in the oven, it actually does get hot. The aluminum is a good conductor of heat, but it’s very thin and can’t hold in a lot of that thermal energy. So when you touch the foil, it transfer that heat it does hold to your hand, which has a lot more mass than the tin foil, so it doesn’t feel all that hot.

I’m such a bad cook, though, I always use potholders. Safety first.

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