The sky’s a lie from certain viewpoints

[Times photo: Maurice Rivenbark] Line of sight differences made it appear the moon was to the left of the shuttle's trail in Hernando County, above, and to the right of the trail in Pinellas County. [Times photo: Bill Serne]

By JEAN HELLER

© St. Petersburg Times, published February 9, 2001

Okay, class, let's do an experiment.

Look around and find a door knob. Now find your right thumb.

Close your left eye and place your thumb so the knob is just to the right of it. Now open your left eye and close your right eye. See how the knob seems to jump to the other side of your thumb?

This is called "parallax," and that is why so many people thought a mistake had been made with the photograph of the shuttle launch that appeared on the front page of Thursday's editions of this newspaper. Some of you even suggested (gasp!) that we printed the photograph backward.

Not so, we are assured by our photo editors.

The photograph, taken in Hernando County, shows the moon to the left of the shuttle's smoke trail.

But those who viewed the launch from farther south, such as St. Petersburg, know the moon was to the right of the smoke trail.

How can this be?

"Depending on where you were relative to the shuttle, the moon would be in different positions," said Nadine Barlow, a professor of physics at the University of Central Florida. "From Hernando County looking toward the Cape, the moon would have appeared to the left of the smoke trail. From St. Petersburg, it would have appeared to the right."

The effect of parallax was heightened, Barlow said, because the shuttle took off to the north. If it had taken off to the south, the moon would have appeared to its left everywhere.

There will be a quiz later.

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