-- It's one of the most common perils of the Internet age: Is what you're seeing actually true?
On Facebook, that question often goes unasked.
For many, Facebook has become a secure network of trusted online relationships. This has caused users to drop their collective guard, causing incorrect information to spread even faster than it did in the days of now-quaint chain letters and emails.
We're seeing the proliferation of photos that are too good to be true, but are shared by Facebook user after Facebook user.
In the last couple of weeks, Facebook has enlarged the photos shared on the home page, making them more easily readable and giving them more impact.
And many photos are publicly viewable by default, so posts can quickly go viral because they can be seen and shared by any Facebook user who comes across the post.
Photo not even a photo
Last week, on Diwali — the Festival of Lights celebrated by Hindus and others — an incredible image began to spread on Facebook purporting to show India from a NASA satellite, with brilliant multicolored lights blanketing the country and viewable from space.
The image carried the caption: "India at night during Diwali NASA."
That's apparently all the proof many needed. The image was shared an untold number of times — at one count, it was well over 100,000 — with exultations such as "Amazing!" and "What a cool photo!"
Just one problem: It wasn't from Diwali. It's not even a real photograph.
The image, made in 2003, is actually a composite of satellite images of India from the National Oceanic and Atmospheric Administration, according to Chris Elvidge, a physical scientist at NOAA's National Geophysical Data Center.
The composite of cloud-free satellite images is intended to show population growth over time, Elvidge said. The white lights depict where populations were centered before 1992 and more colored lights were added in subsequent years to show the movement of people.
The original poster appears to have been a single Facebook user near Hyderabad, whose post has been shared more than 87,000 times.
Another photo, showing a Washington, D.C., police offer restraining a dog before gunning it down when he said it charged after him, has been given legs by the Occupy Wall Street movement, which has gripped several cities with scenes of skirmishes between police and protesters. Many posters have mistakenly linked the photo to an Occupy confrontation.
The photo, though, was taken on Sept. 12, 2010 — more than a year before the first Occupy Wall Street protest was staged in New York City.
"This is sick … Please spread the word …" said one of the thousands of Facebook users who spread the photo. "I am so outraged I'm crying!" said another.
Occasionally a savvy commenter seeks to set the record straight, saying that the photo isn't from the Occupy movement at all, but the effect is a bit like trying to use a soup ladle to stop a ship from sinking.
Earlier this year, when an unusual 5.8 earthquake hit the D.C. region, a photo quickly popped up online showing the supposed damage: a single plastic lawn chair tipped on its side.
Many shared it with a laugh, but that photo, too, has been online for years and was not what many said it was.
Seek the truth doggedly
No harm, no foul? Maybe.
But as people increasingly depend on friends and other online connections for news and information, the Facebook effect can't be ignored.
Another image being spread this week shows a Great Dane leading another apparently blind Great Dane through a field, its leash gripped between its teeth.
"They have been together for five years and Madison guides Lily by the leash and touches him to make sure he doesn't stumble over anything," the Facebook post read. It's also being shared thousands of times.
That story, though, turned out to be true.
The Associated Press reported last week that the British animal shelter housing the two dogs had been inundated with offers of help.
Still, next time something seems too good to be true, do a quick Google search before spreading the post. It might just be.