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Reversing the Polarity – Silly?

In the forward thinking genre of sci-fi mistakes can be made, ideas that seem so exciting, so bold on screen can turn out to be as plausible as a Jesus Christ’s hovercraft.

Doctor Who - Jon Pertwee is the Third Doctor, 1970-1974There are no end of scientists (and Terry Pratchett) gesturing wildly at the TV in disgust at the crossed out and rewritten theories of the poorest scientific minds in drama; Doctor Who is no different.

SFX have plundered the vault and come up with ten examples of the “Silliest SF Moments“, with fan favourite and genre staple “reverse the polarity of the neutron flow’ coming in at number nine.

The catchphrase was used by Terrance Dicks to aid Jon Pertwee, who was adverse to learning any technobabble in his scripts;

“For many years fans have thought it impossible to reverse the polarity of the neutron flow, on account of the fact that they don’t have either a polarity or a flow. However, neutrons do have a magnetic moment, although they don’t have a net electric charge like other subatomic particles.”

In layman’s terms you could actually get neutrons to flow with a polarity but only theoretically.As SFX transaltes:

“Put it like this, it’d be very hard to do and not likely to fell a Sea Devil.”

The full phrase was only used once during Pertwee’s reign as the Doctor once in 1972’s The Sea Devils – and again during the 20th anniversary episode The Five Doctors.

On other occasions he would simple ‘reverse the polarity’ of various things.

He advises that the drill in Inferno has its polarity reversed, tells Ruth to reverse the temporal polarity of the TOMTIT device in The Time Monster; he reverses the polarity of his sonic screwdriver in Frontier in Space; he reverses the polarity of some dismantled circuitry in Planet of the Daleks; he tells Osgood to reverse the polarity of the diathermic energy exchanger in The Dæmons; and he reverses the polarity of the timescoop in Invasion of the Dinosaurs.

The last use of the phrase was in the Tenth Doctor tale The Lazarus Experiment where the Doctor said he was too out of practice to do it quickly enough to escape the Lazarus machine.

Whether or not making neutrons moon walk ruins a perfectly good episode of Doctor Who is another theory entirely- perhaps its best to leave the last word to Pratchett himself:

“After all, when you’ve had your moan you have to admit that it is very, very entertaining, with its heart in the right place, even if its head is often in orbit around Jupiter.”


Everyone has a favourite Doctor and mine - just for his honesty, his fairness and his ability to not notice the Master's awful, awful disguises/anagrams (Sir Gilles Estram!?!) - has to be the Fifth Doctor, Peter Davison. The stories didn’t serve him as well as his acting served those stories.

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