Our process at TED-Ed involves several steps to make sure the content we present is factually accurate. First, the authors of lessons are educators and subject matter experts. Second, we have a team of fact-checkers who review our content and flag anything that needs review. Unfortunately, there are times when we still make mistakes! That was the case with a lesson we recently published (“How do computers find websites so quickly”).

Our community was extremely helpful and proactive in identifying an error, and after further research and verification, we took the video down. We see mistakes as great learning moments, and the author of the lesson, Chand John, was kind enough to explain what went wrong. (Read his letter below.) The main content of this lesson — explaining how hash tables work and why they’re important — is something we see as valuable in and out of the classroom, and Chand is an excellent educator and communicator. So we’ll be working with him to create a new version that will come at the content from a different direction. Every video we produce takes several months to make, because our script-writing and animation-creating processes both require a lot of time and attention; please stay tuned for a new, corrected version of this video later in the year!

Below, read Chand John’s letter:

When you use the Internet, many different processes and entities are involved: domain name servers, routing protocols, and much more. In an attempt to create a lesson about hash tables in the context of Internet communication, I chose to base the lesson on a very widely available hash table, called the Linux routing cache. Here are a couple of nice descriptions of the routing cache:

http://linux-ip.net/html/routing-cache.html
https://www.cs.unh.edu/cnrg/people/gherrin/linux-net.html#tth_sEc8.2.3

There was a key mistake in how this was introduced in the lesson, however: the Linux routing cache, which contains IP addresses and related information, existed on many devices, but in conducting research for this piece, I misunderstood the context in which the routing cache is typically used.

We introduced the routing cache (which we called a “routing table” in the video, since it was one of multiple routing-related tables available on many computers) in the context of typical Web browsing. However, what the video describes is more like what a router itself can do during typical Internet use, if it happens to use this type of hash table, and *not* what your own computer typically does when you access the Internet (unless, perhaps, you configured it to act like a router itself).

In short, while the routing cache described in the video has *existed* on a very wide array of devices, it is not necessarily *used* on most of those devices for the purpose suggested in the original video.

While we tried *not* to make this lesson describe all aspects of Internet communication (our goal was to focus on one particular aspect of it involving a widely available hash table), the earlier parts of the video make it sound like this hash table is something your devices do every time you use the Internet, which is inaccurate. My big concern after realizing my mistake is that viewers not misunderstand how typical Internet communication works.

We instructors make mistakes sometimes, and sometimes we like to turn these into valuable lessons of their own: in subjects like computer science, where really tiny details can make a huge difference in whether something works or not, or whether a statement is correct or not, the important thing is to be open to feedback, to understand that we will make mistakes, to learn from those mistakes, and to share that knowledge. This is why computer programmers often review each other’s work, why many publications have editors, and why academic research papers go through detailed peer review.

When challenging yourself by learning and doing new things, you will make mistakes, experience failure, and feel discouraged at times. It is how you handle these moments that most influences whether you will continue to progress in your learning. So, those times of failure are your best opportunities to prove to yourself that you can keep going, and to see those moments not as barriers that stop your progress, but rather as stepping stones from which you can propel both yourself and others to new heights. It helps to know that you’re not alone: even the world’s most famous, successful people make mistakes. Chances are, they have made more mistakes than most people, because many of them took on difficult challenges that others avoided.

There’s a big difference between *striving* to be correct 100% of the time, and *expecting* oneself to be right all the time. Mistakes can have consequences, but if you’re willing to learn from them, chances are you will continue to progress in your learning. The biggest barrier I’ve seen to people’s progress is not being wrong at times; it’s the expectation that the point of learning is to be right all the time, and then avoiding new challenges due to an exaggerated fear of failure. And it’s important to support each other when we do encounter new challenges: that’s why we educators and TED-Ed do what we do, to support and encourage our viewers to take on new educational challenges in a fun and inspiring way.

Our top priority is to ensure that educators and students receive accurate information, and I do apologize to all viewers who may have been misinformed about the mechanics of typical Internet communication. I thank everyone who has contributed to the discussion on this video, as well as the amazing team — animators, narrator, editors, and the whole TED-Ed team — who have worked so hard on putting this together. It is a real privilege to continue to work with them on creating these beautifully illustrated lessons for the benefit of viewers worldwide.

— Chand

Inside Out, Pixar’s latest animated masterpiece, is not only an emotional rollercoaster, but also a vehicle for some solid scientific storytelling. Of course, the film can’t be taken literally, as it’s a visual interpretation of abstract concepts: memories are not spheres, and the train of thought is not … actually a train. To help clarify the trickier science, we’ve rounded up 5 TED-Ed Lessons that explain some of the neuroscience and psychology introduced in the film. 

MEMORY

Memories drive both the plot of Inside Out and most of the inner workings of Riley’s brain. But how do our brains actually store them for later retrieval? And are there different types of memories?

This TED-Ed Lesson answers those questions and more with the story of a patient with a remarkable brain.

SADNESS

If Joy is the captain of this movie, Sadness is the navigator. It’s also pretty prominent in our brains when we sit in the audience. I’m only a little ashamed to admit that I cried. Twice.

Inside Out stresses the importance of sadness—it’s not something we can just push away or blissfully avoid all of the time—because it’s critical for our emotional and social health. And the science supports that idea. This lesson explains how.

BRAIN ACTIVITY 

Our brains are pretty complicated, and they’re doing a lot of things, all at the same time (not the least of which is keeping us alive). This lesson helps connect the visual metaphor of Inside Out with the various functions our brains manage.

SLEEP

What’s so great about a good night’s sleep? Why do we even need to sleep at all? “Inside Out” gives a clue for one major reason in the moments when Riley falls asleep and her memories head to long term storage. That’s not far from the truth, as you’ll see in this lesson.

EARWORMS

Is the song from “Lava” (the digital short before Inside Out) stuck in your head? Or the Bing Bong song? Because like Riley’s toothpaste commercial, I can’t shake either one. What’s going on? This is actually an ongoing scientific mystery with a surprising history.

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Featured image courtesy Disney/Pixar.

Thanks to physicist Kip Thorne’s influence, the latest space-travel film Interstellar features some remarkably scientifically accurate depictions of topics that have previously been mangled by the Hollywood treatment. Here, we wrangled together five TED-Ed Lessons that can serve as a (spoiler-filled) crash course on some of the trickier science in the film.

Time Dilation

Why do 7 years pass on Earth for every hour spent on the water planet orbiting Gargantua? How does Murph wind up older than her father? Why does Paul Rudd never seem to age? (OK, that last one has nothing to do with Interstellar, but we have our suspicions that they’re related…)

5-dimensional Beings

What does it actually mean for a being to be 5 dimensional? What is the tesseract that Coop falls into inside the Black Hole’s event horizon?
*Note: This lesson references 4 dimensional life forms, while Interstellar talks about 5 dimensional beings. The reason for the difference is that this lesson is just looking at geometric dimensions, whereas Insterstellar is counting 4 spatial dimensions plus 1 time dimension.

Black Holes and Gravity

Why is there a secret locked inside Gargantua? How are gravity and spacetime related? Why does Sandra Bullock hate space so much? (OK, OK, different movie again, sorry!)

Tidal Waves

We suspect that the colossal waves on the water planet have something to do with tidal forces caused by Gargantua’s gravitational pull, similar to how the moon causes the Earth’s tides. The film isn’t entirely clear on that point, but for an explanation of tsunamis on Earth, look no further.

Newton’s Third Law

It isn’t often that a protagonist will cite a foundational law of physics when he heroically sacrifices himself. But when he or she does, it makes us feel all warm and fuzzy inside. This video will help you brush up on Newton’s Laws for the next time you need to justify an epic life decision.