MINNEAPOLIS (WCCO) – The Super Bowl and its memorable TV ads are just two days away.

So we’ll start with a question about commercials.

Dorothy Holzkopf from Rogers, Minn., wondered: Why do the wheels in car commercials look like they’re spinning backwards?

It’s an illusion.

It has to do with the shutter speed of the cameras. Our video cameras take 30 pictures per second, so they don’t catch all the action. But they’re close.

Because of that, when the pictures get stitched together, it shows part of the wheel turning. When we stitch all of those individual pictures together, it often gives the illusion of moving backwards.

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Pat in White Bear Township has seen a lot of commercials for jewelers buying used diamonds. He wanted to know: Are jewelers selling us used diamonds?

We asked Dean and Umit from Wedding Day Diamonds.

And they said, in the jewelry world, there is no such thing as a used diamond. All jewelers take trade-ins from clients that have purchased diamonds, and those diamonds are resold, because unlike other stones, diamonds don’t show wear and tear.

At Wedding Day, they take diamonds – certify them – and sell them to clients, wholesalers or other jewelers.

Sometimes they’ll re-cut the diamonds to make them more brilliant or attractive.

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Terry Valentine’s heard that noise from the new traffic lights along University Avenue in St. Paul. He wanted to know: Why are the stop lights clicking?

Terry thought it was the timer running the light, but that’s all electronic. It’s actually an audible cue for people who are low-vision or blind.