Long and short of contrails

Atmospheric conditions cause airplane engines to form exhaust contrails.  These are caused by the hot and moist engine exhaust gases mixing with the cold air.   Long contrails mean the air at the flight level is very humid.  Short contrails indicate drier air and a lack of water vapor in the atmosphere at that altitude.  Very low relative humidity air will rarely produce a contrail.

Short trail

Long trail

In the two exemplars shown here, the contrails are produced by a four-jet engine airplane.

Sliding to the left

Seat shadows

The slanting sun casts seat slat shadows on the sidewalk.

Brick faces

Heavily pointed wall

Years of weather exposure and too diligent cleaning have worn down the faces of the bricks in this wall.

Shado-ramic

Shadow selfie

The shadow cast by the setting sun can make a person seem just a bit taller than they really are.  This shadow panoramic was created from two images of the street beneath our feet.

Two views one store

Store left wall

Store upstage center

When you are not sure which view is the better, photograph them both! 

These two stereographs of an empty storefront are presented in relaxed view 3d.

 

Shady returns

RETURNS 24 HOURS sign

The slanted afternoon sun turns the raised lettering of this sign into a shadow font

Blue vee

It goes that-a-way

While the blue directional arrow marking the underground utility infrastructure is fading, the paint on the "V" of the water cover remains, brightly pointing the way.