We all know about lemmings, right? These tiny Arctic rodents occasionally commit mass suicide by hurling themselves off cliffs en masse. Why, adorable fuzzy creatures? Why?

The answer is: They don't. Lemming suicide is a myth, a misconception, a lie.

We hold this false belief because a 1958 Disney documentary called White Wilderness staged fake lemming suicide scenes for the camera. (Disney filmmakers shipped lemmings to Canada and chased them off a cliff.) Here's the scene that created the lemming suicide myth.

It's hard to know what's true and what's false, and always has been. Hoaxes, rumors, urban legends, conspiracy theories, political spin and propaganda have been with us for millennia.

The internet has made this problem both better and worse. It's better because we can look things up and research what's true. For example, Googling "lemming suicide" returns stories on the fabrication of the myth. But it's also worse, because falsehoods are easier to spread on social media and elsewhere.

In recent months, fact-checking (which in the past only professional journalists fretted over) has become central to political discourse. "Fact-checking" has come up in discussions about the role of moderators in presidential political debates and has been repeatedly mentioned during the debates themselves.

Before the internet, most fact-checking happened before publication. Anyone who cared about facts subscribed to trusted newspapers and magazines. Editors on staff, and sometimes dedicated, full-time fact-checkers, identified and researched every factual assertion.

That's all you had to do: Pick reputable sources of news (like the publication you're reading now).

Trouble is, social media causes us to lose control over the sources of information we're exposed to. We see whatever is shared by the people we follow. And they share stories from their followers. And so on.

Technology created this problem. Can technology solve it?

Algorithms giveth, and algorithms taketh away

Google this week added a "Fact Check" item to search results. This links to an article that's designed to offer explicit fact-checking related to the search query, and it appears in the expanded story box on Google News for users in the U.S. and U.K., as well as the Google News & Weather apps on both iOS and Android.

The "Fact Check" result joins other categorical highlights, including "In-Depth," "Wikipedia," "Local Source" and, my favorite, "Opinion."

And speaking of opinion, how does Google choose which fact-check article to highlight?

The company starts by looking for schema.org ClaimReview markup, which provides specifics in a web page's code on what exactly is being fact-checked in an article. It then uses a wide range of other signals to surface what Google algorithms conclude is the most reliable and authoritative fact-checking article related to the search query.

Nice!

Meanwhile, the opposite is happening at Facebook. After Facebook's human editorial team was criticized by a political activist for bias in how they chose stories for Facebook's Trending feature, Facebook laid off the editorial staffers in late August and replaced them with algorithms.

Unfortunately, these algorithms are having a hard time telling fake stories from real ones. "The Intersect" reportedly ran a series of experiments and found out that Facebook has published several hoax or fake stories in its Trending section.

Facebook algorithms are actually choosing hoaxes and deliberately spreading them to millions of users. Sadly, we humans don't need help from algorithms. We can spread misinformation just fine without them.

Anything for traffic

Did you hear about Rachel Brewson? She became the subject of a series of articles on the women's site xoJane. She's a Hillary Clinton supporter who fell in love with a Donald Trump supporter named Todd. At first, their political disagreements added passion to their relationship, and they got married. But then things soured, they split up and Rachel penned a post on xoJane headlined, "Trump is Tearing My Marriage Apart."

Great story, right? The online news site "Fusion" thought so, and interviewed the couple on camera. So did ABC's Nightline.

Unfortunately, it never happened, and Rachel Brewson doesn't exist. The whole thing was a publicity stunt to drive traffic to a now-defunct site called "Review Weekly." They even hired actors to play Rachel and Todd on camera.

This is a fraudulent business model. It's fiction presented as nonfiction, based on the idea that a prurient, gossip-centric, reality-TV-obsessed public needs to believe a drama is true in order to stay engaged.

Before Jezebel's investigative journalism exposed the fraud, there was no way to "fact-check" the story, no way to know for sure whether the story was true, partly true or a total lie.

And speaking of lies...

Let's talk politics

Political organizations have always spread disinformation that helps their candidates. But in recent years, they've been spreading disinformation about fact-checking itself!

I learned this the hard way.

Watching the political arguments over the upcoming U.S. presidential election take over my Twitter stream, it became clear that each side was arguing from its own set of facts. And this frustrated me, because facts are facts -- or they're supposed to be. So I experimented by responding to heated political arguments with links to fact-checking sites.

To quote a common clickbait catchphrase, you won't believe what happened next!

My tweets were pounced upon by hoards of people convinced that fact-checking sites are biased, corrupt and untrustworthy. Every specific site I linked to was discredited as owned or controlled by a politician or their supporters, or it was a "joke," not to be taken seriously.

Political propaganda has successfully inoculated a minority of the voting public against the scourge of fact-checking. They've been told that the news media are corrupt and fact-checking sites mere smokescreens.

The professional political operatives that advise candidates also anticipate fact-checking and have learned to make their comments fact-check-proof. They do this by being slippery, vague and categorical, instead of specific. An entire political style of speaking has emerged, designed to be fact-check-proof.

For example, saying that a candidate voted in Congress against a specific bill designed to thwart ISIS is fact-checkable. Saying that a candidate "did nothing to stop ISIS" is not fact-checkable.

Saying that a candidate's specific policy prescriptions have been denounced by a specific expert is fact-checkable. Saying that a candidate "has no clue about what to do [about education and innovation]" is not fact-checkable.

Still, the fact-checking sites try to fact-check such statements and wind up posting long-winded explanations and somewhat subjective conclusions, all of which provide more fodder for argument, disagreement and partisanship, rather than clarity over the facts.

So is that it? Are we really living in a post-fact world?

How to be an informed citizen

Thanks to the social web and the way it exposes us all to unreliable content, we're mostly on our own when it comes to figuring out what's true and what's false.

In my opinion, each of the major fact-checking sites is pretty solid. And when several sites agree -- when there's a consensus among the fact-checking sites about a specific point -- that consensus can be taken as a fact you can rely on.

My favorite fact-checking sites include Emergent, On The Issues, Factcheck.org, Snopes, Politifact, About.com, Truth Or Fiction and Hoax Slayer.

My best advice is to promote these sites from passive reference sites to active sources of content.

Spend quality time proactively browsing your favorite fact-checking sites, as if they were blogs or news sites. They're great sources of information because they tend to be clear and present controversial information in a systematic way that helps understanding.

Also: Add the Twitter accounts of several fact-checking sites to your feed or add the RSS to your reader. Get the facts even before you get the lies.

Don't be like the fake Disney lemmings and follow the internet masses over the cliff of confusion. We are not living in a post-fact world. Facts really do exist.

And that's a fact.