The March 2009 issue of Popular Mechanics magazine has a special feature on the science behind sightings of UFOs – unidentified flying objects.

It says many UFO sighting are caused by military aircraft on training flights – or flares they drop.

Popular Mechanics shows six U.S. military aircraft likely to be mistaken for UFOs. It notes that the “flying wing” B-2 bomber “looks like an alien craft from nearly any angle and specifically like a flying saucer when viewed head-on or in profile.”

The magazine gives several examples of alleged UFO footage. In one, a mysterious ring of bright lights over Phoenix, Arizona in 1997 was caused by decoy flares a pilot had dropped.

Others are hoaxes. In March 1983, more than 300 people reported seeing V- and boomerang-shaped lights in New York’s Hudson Valley. Pilots had rigged their planes with extra lights before flying in formation at night.

Styrofoam plates and bowls were used in another hoax photo.

Some UFO sightings may be caused by natural phenomena, like the large saucer-shaped lenticular clouds that can form near mountains.

The planet Venus was mistaken for an enemy aircraft in World War II and fired at.

As Popular Mechanics points out, belief in flying saucers is a distinctly modern phenomenon. In the ancient past, people thought gods rode chariots across the sky. Our fantasies are now more technologically advanced.

The four Iranian missiles blasting off in unison sure looked impressive in a photo that appeared on July 9. They should have. The photo was digitally altered.

The blog Little Green Footballs (LGF) spotted the digital fakery that same day. One missile that had apparently failed to launch had been removed and replaced with a faked composite made from images of the other missiles and smoke trails.

In a “corrective refile” note to its editors, Agence France Press stated that the four-missile image released by Sepah News, the public relations arm of Iran’s Revolutionary Guards, had been “digitally altered to show four missiles rising into the air instead of three during a test-firing.” It added, “the second right missile has apparently been added in digital retouch to cover a grounded missile that may have failed during the test.”

In a July 10 post, “Reality vs. Photoshop,” LGF cites another blog, Kamangir, which says another recently released Iranian photo appears to have actually been taken two years ago.

In the 1950s, Soviet leaders had their long range bombers fly over Red Square repeatedly during military parades in an effort to make their fleet appear larger than it was. But that was before Photoshop.