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What I liked: In the words of Glad-OS "This was a triumph, I'm making a note here, huge success... for the people who are still alive." This is essentially the justification the bad guys have for their actions. It turns out it doesn't make much of a difference if it is a homicidal robot or some homicidal people singing the song to you, it still doesn't seem like a good excuse. But it does get stuck in your head, it's a very catchy tune. I like that if you invent a fantasy world you get to make up completely non-internally consistent rules for your world. What is affected by accelerated time? Living things-yes unless you're bacteria in which case no unless you are tetanus then yes again. Dead things-yes. Unless it's food or paper or clothes. Never alive things- no but also maybe yes. A single bolus dose of Magnetic waves, which are notoriously afraid of calcium carbonate. 

What I didn't: So, on a completely different topic, that has nothing to do with the movie, let's talk about scientific rigor. In order to interpret any results you need replicates because freaky unexplained one off things can happen any time. You need to see if something happens predictably the same way every time; that's why clinical trials enroll hundreds to thousands of people at a time. That is also why, hypothetically speaking, stranding less than ten people with diverse ailments on a beach is a terrible way to test anything. You could recruit a bunch of people with the same ailment or maybe a large family with affected and unaffected individuals. If I found myself putting together an accelerated temporal experiment I would focus on two of the greatest problems facing us: antibiotic resistance and cancer. In something the size of a large food cooler, that you may or may not have for a trip to the beach, you could complete hundreds of replicates over thousands of bacterial generations searching for new antibiotic substances. Similarly you could for screen fish or worms that did not develop cancer over hundreds or thousands of generations and thus discover anticancer genes. All this with the added bonus of not murdering anyone. Or if you are less academically inclined, this would be an excellent place to store nuclear waste, or other waste for that matter. And who set up the cameras? You know what would solve all the problems? Robots. Robots would solve all the problems. Why was no one using robots? Everyone should use robots. 

Who should watch this movie? People who dislike the beach. People who have not heard of robots or magnetic waves.  

Would I watch it again? No, but I do hope the screen writers stay in entertainment and don't seek a second career in research.