By Louise Mayor

This month is the 25th anniversary of Physics World – the member magazine of the Institute of Physics – and in addition to a special celebratory issue, we’ve decided to set you a challenge.

In fact, we have teamed up with GCHQ – one of the UK’s three Intelligence Agencies and home to some of the country’s hottest code-breaking talent – to create with us a set of five physics-themed puzzles. The puzzles have been devised by three GCHQ members of staff, who today we still know only as Colin, Nick and Pete. (Thank you, guys!)

Below is Puzzle 1, the first of the five. The rest will be released on successive Tuesdays throughout October on this blog. The first is the easiest – they only get harder from here on in!

You can check your answer for each puzzle using the box at the bottom of each post. If you enter the correct answer, you will be told you’re person number X to have done so. But will you be the first?

Once the fifth and final puzzle is released, then you’ll be able to check all your answers simultaneously in one master answer-checker, and see where you rank overall in solving in the Physics World at 25 Puzzle. We hope you enjoy the challenge and that, as there are no prizes, the satisfaction of completion will be a big enough reward.

Your first challenge lies below. #PW25puzzle

There is a word missing from the following. What is it? (Enter the answer in its encrypted form.)

TNVERI SMH EG ZSMRNPMUD: M SLRN PYMP VERRNVPT M ZSMRNP PE PYN TQR THNNZT EQP NXQMS MUNMT LR NXQMS PLKNT