Subtitles section Play video Print subtitles Hey, Vsauce. Michael here. A few years ago in Minneapolis an angry dad stormed into the retail store Target. His daughter, a high schooler, had been receiving coupons in the mail from the store for things like cribs and diapers. Was Target encouraging his daughter, a minor, to go out and get pregnant? well Well, the store apologized but a few days later they heard back from the father. He told them "a few things have been going on in my household I was unaware of. My daughter is due in August. I owe you an apology." You see, Target's internal algorithms have been tracking and processing his daughter's purchases and recently she'd started buying different items than usual. Things like certain vitamin supplements and scent-free soaps and lotions. Behaviors the system flagged as evidence she could be pregnant, thus they her sent the coupons. And they were right. Without being told, Target knew that a girl was pregnant before her own father. We are tracked and followed digitally now more than ever before. We live in a world of 24/7 CCTV, browser cookies, trackable debit cards and cell phones and GPS, fingerprinting and DNA analysis. But despite all of that, every single year in the United States alone more than 2,000 people disappear and are never found again dead or alive. Where do missing people go? How did they disappear? What if you disappeared and how do you know you haven't already disappeared? In many cases, missing persons are the victims of unsolved or unknown crimes. They may have suffered accidents or taken their own lives and their bodies were never found. Or they may be perfectly fine and have simply escaped their old life, old friends and family, old debt and obligations to start a new life somewhere else, possibly as someone else. How long would it take for people to notice if you disappeared? Well, think about it. I mean, it sort of depends on who you are, how you live and how you disappeared. In most jurisdictions after about five to seven years, if no one has heard anything from you at all, you can be declared dead in absentia. This is what happened to French astronomer Guillaume Le Gentil. In the 18th century hundreds of people traveled far and wide to observe the transit of Venus from different locations on earth. They knew that by comparing their measurements they could calculate more accurately than ever before just how far away the Sun was. So, Le Gentil left Paris in 1760 for Pondicherry in India. But after a storm blew him off course and the British occupied Pondicherry, he was forced to spend the day of the transit on a boat at sea, which rocked too much for accurate measurements to be taken. Now, the next transit would happen in 8 years. But after that, the next next transit wouldn't happen for another 100 years. So, he stuck around. He didn't return to Paris. Instead, he built an observatory and waited. When he finally returned to Paris, 11 years after leaving, he found that he had been declared dead. His wife had remarried, his family had plundered his belongings and his position at the Royal Academy of Sciences had been given to someone else. He never did see the transit of Venus, by the way. On the day that it happened, the sky above him was overcast. We know the human population of Earth. Kind of. Population figures and counters are only estimations. Individuals are best accounted for by real people in their real lives. But that doesn't always happen. Earlier this year Janet Veal passed away in her apartment in Ringwood, Hampshire. Large portions of her body were eaten by her pet cats before she was discovered weeks later. And seven years ago Joyce Carol Vincent was found dead on her sofa, in Wood Green; or at least her skeleton was found. She'd been dead for at least three years and no one ever checked on her. Her television was still on. And four days after Timothy McVeigh bombed a federal building in Oklahoma City, taking 168 lives, a severed left leg was found in the rubble. No one knew who it belonged to. The legs of all the other victims had been accounted for and no one else had been reported missing. DNA analysis showed that the leg belonged to a Lakesha Levy, but she had already been buried with both her legs. So, they dug up her corpse. She'd been buried with someone else's left leg. The legs were swapped, but because her body had been embalmed, DNA in the unknown leg could not be analyzed. To this day no one knows who that leg belongs to. The 169th victim remains a mystery. Some conspiracy theorists argue that the leg may have belonged to be actual bomber, someone besides Timothy McVeigh, who was close enough to the explosion to be obliterated completely, except for one leg. Regardless, what it does show is that it is possible for a person to disappear without anyone ever asking where they went. Sometimes people are reported dead or missing even when they aren't. Premature obituaries are common. Many living people already have one on file. If a famous person dies, the media, television, newspapers, magazines, well they need a full story as soon as possible. So, they prepare them ahead of time, locked away, leaving only the dates and circumstances of the death to be filled in. Makes sense, but it's awkward when they leak before the person's dead. In 2003 CNN's website accidentally carried draft obituaries for living people that could be accessed. It's embarrassing, but for the person reading their own obituary, it's a chance to do something that most of us never get a chance to do. See how you will be remembered after you're gone. Alfred Nobel invented dynamite. He made a fortune manufacturing and selling deadly weapons - cannons and armaments. In 1888 his brother Ludvig died but many newspapers mistakenly thought that he had died and published obituaries for Alfred Nobel. They weren't very flattering. One French paper declared "The merchant of death is dead." Nobel read these obituaries and was so ashamed by what his legacy apparently was going to be. When he did die, he left almost all of his money to the cause of celebrating humanity. He created The Nobel Prize. Marcus Garvey wasn't so lucky. The story goes that after suffering a stroke newspapers ran premature obituaries that were critical of him, saying, he died broke, alone and unpopular. Shocked by how negatively he was being remembered Garvey suffered another stroke while reading his own obituary and died. In April of 2006 five Taylor University students died in a tragic car accident. Another student survived, but was in a coma. She was identified as Laura van Ryn. Her friend Whitney Cerak wasn't as lucky. She was pronounced dead. A thousand people attended her funeral but over the next few days as Laura recovered, she began speaking and when asked her name, Laura said my name is Whitney. The girls looked similar. It turned out Laura was the one they had buried. Later, Whitney was married in the very same church that years before had held her funeral. What if you are already missing and just don't know it? It's not known how often hospitals accidentally switch babies at birth. Modern hospital policies make it unlikely to happen, but because we don't all go out and get maternity and paternity tests for fun, there isn't a lot of data on the phenomenon. But it does happen. It's often discovered because of DNA tests administered to resolve child support disputes. Or, in the case of the 35-year-old woman, in the Canary Islands, it's because in 2001 an employee at a store you're shopping at mistakes you for her best friend - because you look exactly like her, because she is your long-lost twin, separated from you since birth. And the sister you grew up with, thinking was your twin, turns out to be a biological stranger. What if you are missing but the authorities don't know? Such is the life of the unreported missing. People in a country illegally, people estranged from their family and friends with no missing person report ever being filed, children of homeless mothers. These people aren't just missing, they are what is known as missing missing. The FBI's National Crime Information Database contains approximately 50,000 reported missing children, but Outpost For Hope reports that there are more than a million children in America who are missing, without anyone knowing they're missing. It is not against the law to go missing under your own volition. You might have debts to pay or contracts to honor, but if you are an adult, the act of disappearing is not illegal in and of itself. You have the right to go missing. But believing that no one would miss you? That is ridiculous and unscientific. Statistics would suggest otherwise. David Wong wrote one of the most powerful articles I've ever read. There is a lot of information out there. There's even a word for it - infobesity. It takes a lifetime to even experience some of it. It's easy to think that everyone knows everything that you know. But every year more than 100 million new people are born and not a single one of them is born knowing that they are made out of atoms or that black holes are awesome. Someone needs to be there to tell them, to show them. How many jokes do you hear every day, every week? How many jokes do you hear every year? Here's a fun thought. By considering average life expectancy and the typical number of jokes a person hears in a year, David Wong posited a thought, rough in its approximation, but sharp in its essence. If you are under the age of 38 odds are the funniest joke you will ever hear is a joke you haven't even heard yet. And, if you are over the age of 38, odds are you already know a joke that to more people than you could ever possibly meet might be the funniest joke they will ever hear. So, wherever you are, we're glad you there. And as always, thanks for watching.