The Stranger Things season 3 finale should not have worked, as Suzie gave Dustin the wrong code. The latest season of Netflix's hit series once again saw Eleven (Millie Bobby Brown) and her Hawkins friends save the day. While Eleven tried to defeat the Mind Flayer, it was revealed the Russians had reopened the gate to The Upside Down. However, Joyce Byers (Winona Ryder), Jim Hopper (David Harbour), and Murray Bauman (Brett Galman) stepped up to try and close it.
To prevent access to The Upside Down, Joyce and Hopper had to infiltrate the secret Russian base below Hawkins' new mall. Their mission was to shut off their device known as The Keys, which was responsible for reopening the gate. All it takes to deactivate the machine is to obtain two keys and simultaneously turn them. However, the Russians were smart enough to lock these keys away, and the solution to it is Planck's constant. Dustin doesn't know the whole thing by heart, but his girlfriend Suzie does. After a duet of "Never Ending Story", Suzie tells Dustin the code and Hawkins is saved - except it shouldn't have worked.
Despite what some may think the name implies, Planck's constant is a scientific formula that does change over time and is how Stranger Things season 3's finale messed up. Suzie tells Dustin that the value of Planck's constant is 6.62607004. While that is an accurate value for the formula, that is only true in the year 2014, and not in 1985 when season 3 is set. The actual value of Planck's constant in 1985 was 6.626176. The difference is relatively small, but it does mean that Joyce and Hopper should not have been able to open the safe.
After pointing out this error, it obviously raises a question over whether or not this is a big deal. To be fair, this isn't the only mistake that season 3 included, and you can see a few more in the latest Screen Rant video at the top of this post. For a show like Stranger Things that has been fairly accurate in its representation of the '80s, this mistake is all the more surprising and noticeable. It would almost be comparable to Stranger Things season 2 including Back to the Future references instead of season 3. Those involved with the series made sure a mistake as prominent as that didn't happen, but the value of Planck's constant is not one that received the same level of fact-checking.
Even though it'd be better if this mistake wasn't made, the good news for Stranger Things is that most viewers likely had no idea. Planck's constant isn't a common scientific formula, so the majority of the show's audience probably wouldn't know Suzie gave Dustin the wrong numbers. Technically, Suzie was wrong at this moment and the adults never should have been able to turn off The Keys. Lucky for the Hawkins residents, nobody involved with Stranger Things knew any better and Suzie was able to play the hero.