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The Invisible Enemy (Doctor Who)

The Invisible Enemy (Doctor Who) is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand The Invisible Enemy (Doctor Who) rather than just read about it. In short: The Invisible Enemy is the second serial of the 15th season of the British science fiction television series Doctor Who, which was first broadcast in four weekly parts on BBC1 from 1 to 22 October 1977. The serial introduced the robot dog K9, voiced by John Leeson.

The Invisible Enemy (Doctor Who) — main illustration
The Invisible Enemy (Doctor Who) — illustration

Key takeaways

  • The Invisible Enemy (Doctor Who) belongs to science; place it in that map before memorising details.
  • Learn the definition first, then one example that makes the definition concrete.
  • Connect The Invisible Enemy (Doctor Who) to a quantity you can measure, compute or draw — that is where exam questions come from.
  • Reproduce the core statement of The Invisible Enemy (Doctor Who) from memory before moving on to harder problems.

Reference excerpt

The Invisible Enemy is the second serial of the 15th season of the British science fiction television series Doctor Who, which was first broadcast in four weekly parts on BBC1 from 1 to 22 October 1977. The serial introduced the robot dog K9, voiced by John Leeson. In the serial, an intelligent virus intends to spread across the universe after finding a suitable spawning location on the moon Titan.

Plot Some human space travellers are cruising near the outer planets of the Solar System with their ship on autopilot. The TARDIS is travelling through the same region. The crews of both ships are infected by a sentient virus, which chooses The Doctor to be the host of its "mind," the Nucleus of the Swarm. The Nucleus declares Leela a reject and orders her killed. The Doctor manages to break free of his infection and tells Leela how to get the TARDIS to the nearest medical centre. At the medical station, the Doctor's doctor, Professor Marius, introduces the group to K9, a robotic dog he made to replace the real dog he had to leave on Earth. Leela and the Doctor decide to create clones of themselves, which will then be shrunk and inserted into the Doctor. There they will destroy the Nucleus and escape through a tear duct. In the meantime, Leela and K9 fight off the infected staff of the hospital. The plan goes awry, allowing the Nucleus to escape and become human sized. The Nucleus and the infected staff leave for Titan Base so the Nucleus can spawn. The Doctor realises he is cured since Leela's clone introduced her immunity factor into his bloodstream. He replicates it and gives it to Prof. Marius. The Doctor, Leela, and K9 proceed to Titan Base in the TARDIS. They fight off the infected humans, but are again without sufficient weaponry to destroy the Nucleus, or its many children, which are about to hatch as "macro-sized" beings, like the newly macro-sized Nucleus. The Doctor jams the door they are behind and rigs a gun to fire into a cloud of oxygen gas he is releasing and escapes. As intended, when the Swarm finally forces open the door, the blaster fires, igniting the oxygen in Titan's methane atmosphere and destroying the Swarm and the base. When they return to the hospital, they thank Prof. Marius for the use of K9, who has ably assisted them. Prof. Marius offers K9 to the Doctor, as he is due to return to Earth, and the Doctor and Leela leave with their new companion in the TARDIS.

Production Working titles for this story included The Enemy Within, The Invader Within and The Invisible Invader. It was not decided until late in the production that K9 was to be a new companion. The decision to use it in multiple serials was made partly to offset the expense that had gone into making the prop. The Invisible Enemy was filmed and recorded in April 1977. In one scene there is an obvious crack in a wall before it is fired at by K9; the crack was originally concealed, but the scene was reshot with little time left to repair the join.

Cast notes

Michael Sheard (Lowe) makes his fourth of six appearances in Doctor Who, having made previous appearances in The Ark (1966), The Mind of Evil (1971) and Pyramids of Mars (1975). Brian Grellis previously played Sheprah in Revenge of the Cybermen (1975) and would later appear as the Megaphone Man in Snakedance (1983). Frederick Jaeger (Marius) also played Jano in The Savages (1966) and Professor Sorenson in Planet of Evil (1975).

Broadcast and reception

The story was repeated on BBC1 on consecutive Thursdays from 13 July to 3 August 1978, achieving ratings of 4.9, 5.5, 5.1 and 6.8 million viewers, respectively. Reviewing the serial for The Times newspaper on the Monday following the second episode's transmission, critic Stanley Reynolds gave the story a generally negative reception. He also pointed out that in ITV regions where the series was competing with Man from Atlantis in the Saturday early-evening slot, it was now losing the ratings war:

In the current story, The Invisible Enemy, now halfway through its four-week run, a malignant virus has struck a space station. Some evil force is attempting to take the station, and undoubtedly the universe, over. When one is being 'taken over' those sort of lightning flashes like the advert for learning how to hypnotise, travel from the eyes of the villain to the one having the fluence put upon him. One then gets rather furry of face and hand, but the appeal of Dr Who has always been the monster and this time out the BBC seems to have lost its touch with monsters... Maybe the leggy Leela is there for the dad and more earthy 14-year-olds, rather like those appalling rhythmic girls who practise dancing each week on Top of the Pops. Of course the return of the Daleks is all Dr Who needs; what the Top of the Pops girls need is something else, but that is neither here nor there. More recent reviews have also not been positive. Paul Cornell, Martin Day and Keith Topping wrote of the serial in The Discontinuity Guide (1995), "An ambitious project which has the look of a grand folly due to budget constraints and the tongue-in-cheek script... K9 makes a quite impressive debut, though, as with many aspects of The Invisible Enemy, the ideas are better than the realisation." In The Television Companion (1998), David J. Howe and Stephen James Walker called it one of the "weakest" Fourth Doctor stories, mostly consisting of "clichéd and undemanding action-adventure material". They also noted the inconsistent visual effects. In 2010, Mark Braxton of Radio Times awarded it two stars out of five, contrasting it with the Philip Hinchcliffe era and describing it as "a kidified, Poundland Star Wars". He felt "many of the effects are excellent" but observed a "precarious juxtaposition" between good and bad effects and "the ambition of the serial as a whole". He praised the story as a "romping yarn" which "brings out the best in veteran designer Barry Newbery", but criticised "unbelievably incompetent" action scenes, as well as "harsh lighting" and "pristine white sets". He also commented on Louise Jameson as looking "unsurprisingly ill at ease" despite giving "her usual 100 per cent". DVD Talk's John Sinnott disliked the way K9 was used too conveniently and found the plot too similar to Fantastic Voyage (1966), but less well done. He praised the visual effects of the inside of the Doctor's head, but criticised the other sets.

Commercial Releases

In print

… excerpt ends here. Continue reading the full article.

Worked examples

Example 1 — a first encounter with The Invisible Enemy (Doctor Who)

Start with the simplest possible case. Write down what The Invisible Enemy (Doctor Who) claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to The Invisible Enemy (Doctor Who) before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about The Invisible Enemy (Doctor Who) ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of The Invisible Enemy (Doctor Who)

In research
The Invisible Enemy (Doctor Who) appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry
Engineering practice reuses The Invisible Enemy (Doctor Who) in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom
The Invisible Enemy (Doctor Who) is common in secondary-school and first-year university syllabi. It links to neighbouring topics 1977 British television episodes, Doctor Who serials novelised by Terrance Dicks, Fiction about size change, so understanding it makes those chapters shorter.
In everyday life
Look for The Invisible Enemy (Doctor Who) outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.
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How to study The Invisible Enemy (Doctor Who) in 20 minutes

  1. Read the reference excerpt below once, without taking notes.
  2. Close the page and write down what The Invisible Enemy (Doctor Who) means in your own words.
  3. Compare your version with the excerpt and mark what you missed.
  4. Work through the three examples above with pen and paper.
  5. Explain The Invisible Enemy (Doctor Who) out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is The Invisible Enemy (Doctor Who) in simple terms?

The Invisible Enemy is the second serial of the 15th season of the British science fiction television series Doctor Who, which was first broadcast in four weekly parts on BBC1 from 1 to 22 October 1977. The serial introduced the robot dog K9, voiced by John Leeson.

Why does The Invisible Enemy (Doctor Who) matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study The Invisible Enemy (Doctor Who)?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on The Invisible Enemy (Doctor Who).

Tags

  • 1977 British television episodes
  • Doctor Who serials novelised by Terrance Dicks
  • Fiction about size change
  • Fiction set on Titan (moon)
  • Fourth Doctor serials
  • Television episodes about cloning
  • Television episodes set in hospitals
  • Television episodes written by Bob Baker (scriptwriter)
  • Works set in the 5th millennium

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