For an interesting and lighthearted look at some of the problems arising from the Back to the Future movies, read the article by Martyn Ruks on the BCS website.
Ruks looks at the security implications of the inventions featured, such as flying cars and hoverboards.
Although the Back to the Future films were made 30 years ago, they are shown so often on tv (well, British tv at any rate) that most of your students are bound to have seen them. You can't rely on that, though, so it might be a nice idea to rent the movie and show it to your classes (if the rental conditions permit) -- but with one crucial addition.
Set the students various tasks to carry out while watching the movie. For example, ask them to make a note of any cyber security or other safety issues they identify. Ask them to write a program or set up a spreadsheet that will work out how much fuel would be needed to travel backwards and forwards in time. (They won't necessarily have all the data they need to run the program or spreadsheet accurately, but that shouldn't prevent them actually creating it.)
Maybe ask them to create a flow chart showing the progress of the trip back in time and then back to the present, with the critical points (ie where history could have been changed) marked on it.
Well, you get the picture. There's a lot you can do with a film like that once you start thinking about it. Alternatively, set them the homework of seeing the latest Star Wars film. I'm sure they won't find that too arduous. Though I suggest you see it first just in case there's nothing in it you can play around with. I can't imagine that would be the case though.
Here's the article I mentioned earlier: Back to the future.
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