Hummingbirds, snowflakes are both mostly unique

Today’s question: Can any bird other than the hummingbird fly backwards? Not really.

The vast majority of birds are equipped with strong muscles to power their wings downward while relying on wind lift to help bring their wings up again.

Hummingbirds evolved with a neat-o set of muscles that allow their wings to move up and down with equal power and with a bit less power to the sides and backward.

Some birds — herons, egrets, warblers and flycatchers, for example — can flutter slightly backward, but not for any distance or sustained period of time.

A few others — such as ospreys, kestrels, kingfishers and cuckoos — can use the wind to appear to fly backward, but they really can only hover a bit. Why do cab drivers no longer take the inititative to hold the cab door open for their passengers? I don’t know.

How do we know that no two snowflakes are alike? And what is the process of snowflake formation that makes them all different?

A snowflake forms when very cold water droplets freeze on a tiny bit of pollen or dust in the atmosphere and the bit grows heavy enough to fall to earth. As it falls, more water vapor gloms on to it and crystalizes, forming the six arms of a snowflake.

As the crystal grows, the molecules do not come together in perfectly regular order.

It is entirely possible to create identical snow crystals in the lab. And if you were to minutely examine one million snowflakes, it is possible you might find two alike. It is estimated this would take you about 100,000 years.

There are about 10 followed by 18 zeros water molecules in a snow crystal and an infinite number of ways in which those molecules can arrange themselves. So the odds of finding two alike are pretty much zero.