The computer countdown reads "solar impact". Solar refers specifically to Earth's sun. It should read "stellar impact."
In the Booklet that comes with the Series 3 DVD Boxset, David Tennent (The Doctor) revealed that in one scene he was accidently given the stunt man's suit, which was too big for him. He commented "I looked like a wee boy in his Dad's jacket"
The escape pod is recalled to the ship by magnetic means. Considering the situation, this is problematic, as the power of magnetism is substantially decreased by heat, and, as it reaches the Curie Point, it loses all magnetism. In the immediate vicinity of the sun, the temperature should create substantial problems with any magnetically attractive device.
Happy Numbers: One of the door lock sequences is a short list of Happy Prime Numbers "313,331,367,...?", with the next number of the sequence, 379, to open the door with, being the next Happy Prime in the sequence.
A Happy Number is identified by an iterative process: take the number, calculate the sum of the squares of its digits, and repeat the process until the number equals 1 (an obvious endpoint), or it falls into a looping cycle which does not include 1. If this process ends in 1, it's a Happy Number, if it does not, it's an Unhappy Number.
3^2+2^2 == 9+4=13
1^2+3^2 == 1+9=10
1^2+0^2 == 1+0=1
If a Happy Number is also a Prime Number, then it's a Happy Prime.
The title 42 is the first time in the show's history that a story title was just a number.
When the system lockdown begins and the Doctor asks about the defences, it is said the doors are deadlock sealed and the Doctor replies that a sonic screwdriver will not help. The screwdriver's ineffectiveness against deadlock seals has also featured or been mentioned in, Bad Wolf, School Reunion, Evolution of the Daleks and the Sarah Jane Adventures episode Invasion of the Bane.
The rising temperatures in the spaceship are similar to The End Of The World (2005) when the temperature increased minutes before the Earth exploded.
The phrase 'burn with me' has been used before this series- the Plasmavore Florence Finnigan said it just before she was incinerated by the Judoon in Smith And Jones.
The Doctor uses the French term 'allons-y' again (which means 'let's go') when they're in the medical centre looking after Korwin. He has previously used this in Army Of Ghosts and Evolution Of The Daleks.
The Doctor: We need a backup in case they don't reach the auxiliary engines in time. Come on, think! Resources! What have we got?
Martha: (over intercom) Doctor?
The Doctor: What is it now?
Martha: Who had the most number ones: Elvis or the Beatles? That's pre-download.
The Doctor: Elvis. No! The Beatles. No! Wait, um... um... oh, there was that remix, um... I don't know! I am a bit busy.
Martha: Fine, I'll ask someone else.
The Doctor: Now, where was I? Here Comes The Sun. No, resources!
(trying to open a password-sealed door)
Riley: Find the next number in the sequence: 313, 331, 367... what?
Martha: You said the crew knew all the answers!
Riley: The crew's changed since we set the questions.
Martha: You're joking.
The Doctor: 379.
The Doctor: It's a sequence of happy primes. 379.
Martha: Happy what?
The Doctor: Just enter it!
Riley: Are you sure? We only get one chance.
The Doctor: Any number that reduces to 1 when you take the sum of the square of its digits and continually reiterate until it yields 1 is a happy number, any number that doesn't isn't, a happy prime is a number that's both happy and prime, now type it in! I don't know, talk about dumbing down. Don't they teach recreational mathematics anymore?
(After speaking to Martha, Francine hands the mobile phone to a blonde woman who seals it in a bag)
Francine: That's all?
Sinister Woman: For now. Have you voted?
Francine: Of course. Just don't expect me to tell you who for.
Sinister Woman: Thanks for all you're doing, Mrs. Jones. Mr. Saxon will be very grateful.
Martha: (saying goodbye to Riley) It was nice, not dying with you. I reckon you'll find someone worth believing in.
Riley: I think I already did.
(after a pause, the two of them kiss)
Scannell: (seeing the TARDIS) This is never your ship.
The Doctor: Compact, eh, and- another good word- robust. Barely a scorch mark on her.
The Doctor: It's your fault, Captain McDonnell.
McDonnell: Riley, get down to Area 10 and help Scannell with the doors. Go!
(Riley heads off)
The Doctor: You mined that sun, stripped its surface for cheap fuel. You should have scanned for life!
McDonnell: I don't understand.
Martha: Doctor, what are you talking about?
The Doctor: That sun's alive, a living organism. They scooped out its heart, used it for fuel and now it's screaming!
McDonnell: What do you mean? How can a sun be alive? Why is he saying that?
The Doctor: Because it's living in me.
McDonnell: Oh my God.
The Doctor: Humans! You grab whatever's nearest and bleed it dry. You should have scanned!
(Martha phones her mother to say goodbye)
Martha: Mum… you know I love you, don't you?
Francine: Of course I do. What's brought this on?
Martha: I never say it. Never get the time or never think of it and then... (starts to cry) I really love you. Tell Dad, Leo and Tish that I love them too.
Francine: Martha, what's wrong?
Martha: Nothing, I promise.
Francine: Where are you?
Martha: Just out.
Francine: With anyone nice?
Martha: Some mates.
Francine: What mates?
Martha: Mum, can we not just talk?
Francine: Of course. What do you want to talk about?
Martha: I dunno, anything. What you had for breakfast, what you watched on telly last night, how much you're gonna kill Dad next time you see him. Anything.
(Riley and Martha are in the jettisoned escape pod)
Riley: The wonderful world of space travel. The prettier it looks, the more likely it is to kill you.
Martha: He'll come for us.
Riley: It's too late. Our heat shields'll pack in any minute and then we go into free-fall. We'll fall into the sun way before he has a chance to do anything.
Martha: You don't know the Doctor. I believe in him.
Riley: Then you're lucky. I've never found anyone worth believing in.
Martha: No girlfriend? Boyfriend?
Riley: The job doesn't lend itself to stable relationships.
Martha: Family then?
Riley: My dad's dead. I haven't seen my mum in six years. She didn't want me to sign up for cargo tours. Things were said and since then… all silent. She wanted to hold on to me, I know that. She's so stubborn.
Martha: Yeah, well, that's families.
Riley: What about you?
Martha: The works. Mum, dad, dad's girlfriend, brother, sister. No silence there. So much noise. (starts to tear up) God, they'll never know. I'll just have disappeared and they'll always be waiting.
(McDonnell comes face to face with the possessed Korwin)
McDonnell: Korwin? What are you? Why are you killing my crew? What did you do to him? What have you done to my husband? (Korwin stops) You recognise me? Korwin, you know me. It's Kath, your wife.
Korwin: My wife?
McDonnell: That's right. You're still in there. Your wife.
Korwin: It's your fault.
McDonnell: Is the infection permanent? Can you cure him?
The Doctor: (after a long pause) I don't know.
McDonnell: Don't lie to me, Doctor. Eleven years we've been married. We chose this ship together. It keeps me honest, so I don't want false hope.
The Doctor: The parasite's too aggressive; your husband's gone. There's no way back. I'm sorry.
McDonnell: Thank you.
The Doctor: Are you certain nothing happened to provoke this? Nobody's working on anything secret? 'Cause it's vital that you tell me...
McDonnell: I know every inch of this ship. I know every detail of my crew's lives. There is nothing.
The Doctor: Then why is this thing so interested in you?
McDonnell: I wish I knew.
Erina: (after Ashton gives her orders over the intercom) Whatever you say, 'boss'. Go there. Come back. Fetch this. Carry these. Make drinks. Sweep up. Please… kill me now.
(The possessed Korwin appears beside her)
Korwin: Burn with me...
(The Doctor, McDonnell and Scannell find the vapourised Abi Lerner in the medical centre)
The Doctor: Burn with me.
Scannell: That's what we heard Korwin say.
McDonnell: What? You think… No way! Scannell, tell him! Korwin is not a killer. He can't vapourise people. He's human!
The Doctor: (reading the test results) His bioscan results. Internal temperature, one hundred degrees. Body oxygen replaced by hydrogen. Your husband hasn't been infected; he's been overwhelmed!
McDonnell: The test results are wrong!
The Doctor: What is it, though? A parasite? A mutogenic virus? Something that needs a host body, but how did it get inside?
McDonnell: Stop talking like he's some kind of experiment!
The Doctor: Where has this ship been? Have you made planet floor recently? (McDonnell shakes her head) Docked with any other vessels? Any sort of external contact at all?
McDonnell: What is this, an interrogation?
The Doctor: We've got to stop him before he kills again.
McDonnell: We're just a cargo ship!
The Doctor: The power's still working, the generator's going, if we can harness that… ah!
McDonnell: Use the generator to jumpstart the ship.
The Doctor: Exactly! At the very least, it'll buy us some more time.
McDonnell: That is brilliant.
The Doctor: I know! (to Scannell) See, tiny glimmer of hope.
Scannell: If it works.
McDonnell: (to Scannell) Oh, believe me, you're gonna make it work.
The Doctor: (via intercom) Martha, be careful. There may be something else aboard the ship.
Martha: Anytime you want to unnerve me, feel free.
The Doctor: (via intercom) Will do, thanks.
Martha: What are you typing?
Riley: These doors' trip-codes the answer to a random question set by the crew. Nine tours back, we got drunk, thought them up. Reckoning was if we're hijacked, we're the only ones who know all the answers.
Martha: So you type in the right answer…
Riley: This sends an unlock pulse to the clamp, but we only get one chance per door. Get it wrong; the whole system freezes.
Martha: Better not get it wrong then.
Riley: The oldest and cheapest security system around, eh, Captain?
McDonnell: Reliable and simple. Just like you, eh, Riley?
Riley: Try and be helpful, get abuse. Nice.
McDonnell: The auxiliary controls are in the front of the ship
Scannell: There's twenty-nine password-sealed doors between us and them. We'd never get there in time.
Martha: Can't you override the doors?
Scannell: No. 'Sealed closure' means what it says. They're all deadlock sealed.
The Doctor: So a sonic screwdriver's no use.
Scannell: Nothing's any use. We've got no engines, no time and no chance.
The Doctor: Oh, listen to you! Defeatist before you even started! Where's your Dunkirk spirit?
The Doctor: Oh, we're in the Toraji system, lovely. You're a long way from home, Martha. Half a universe away.
Martha: Yeah, feels it
The Doctor: And you're still using energy scoops for fusion. Hasn't that been outlawed yet?
McDonnell: (off Riley's look) We're due to upgrade next docking.
The Doctor: Thank you.
Martha: Don't mention it.
The Doctor: (regarding the ship) Now that is hot!
Martha: It's like a sauna in here...
International Air Dates:
Australia: August 11, 2007
Brazil: November 14, 2007
Canada: July 29, 2007
New Zealand: October 7, 2007
United States: August 17, 2007
Turkey: December 12, 2010
Russell T Davies had considered bringing the Ood back in this episode.
The character of Riley was named after writer Chris Chibnall's godson. Russell T Davies wanted him to be called Riley Kincade but opted for Vashtree after realising a character in the episode Gridlock had the surname Kincade.
Overnight viewing figures for this episode were 7 million, with a final viewing figure of 7.41 million.
The stasis chamber is adapted from the prop used as the MRI scanner in the hospital in Smith and Jones, according to associate production designer James North.
The episode was not filmed on a set, but in a factory. The actual filming took place in January, and instead of actually being hot, it was very cold. The actors were covered in baby oil to simulate perspiration.
In this episode, Martha is given both a key to the TARDIS and the ability to call home with her phone from anywhere.
The title 42 refers to the series 24, in which events are presented in real time, as they are in this episode, which starts with 42 minutes to succeed or die. It also refers to the 42nd century (during which this episode is set). And is probably also a riff on The Hitchhikers Guide to the Galaxy (42 is the "answer to life, the universe and everything").
A prologue for this episode was especially written for the official Doctor Who website (written by Joseph Lidster).
This episode was originally intended to air on May 12 2007. However, it was postponed for a week due to the BBC's coverage of the Eurovision Song Contest (as an early start for the episode would not be appropriate).
This episode was written by the head-writer of the Doctor Who spin-off Torchwood, Chris Chibnall.
When Korwin puts on the mask, the mechanical breathing sound is similar to Darth Vader's respirator from the Star Wars movies.
The shadows burned into the inside hull of the SS Pentallian by the living sun are reminiscent of those caused by the nuclear explosions of Hiroshima and Nagasaki. These were created when the buildings were discoloured by the brightness of the blast. Anything blocking the light, in this case a human body, created a permanent and haunting shadow.
Martha: I can't believe my life depends on a stupid Pub Quiz.
A pub quiz is as stated a quiz held in a pub. It is largely a British phenomenon but has been exported to many countries, generally by students on their Gap year travels. In the USA they are commonly called Trivia Nights. Pub quizzes are still quite popular after their apex in the mid-1990's as they generally attract people to a pub who are not found there on other days.
The Doctor: If you can't stand the heat.
"If you can't stand the heat, you better get out of the kitchen", is an adage widely associated with US President Harry S Truman, referring to not getting involved in a situation you aren't prepared to handle.
The Doctor: Here comes the Sun.
'Here Comes the Sun' is a song written by George Harrison from The Beatles' 1969 album Abbey Road. Whilst this is an accurate description of the situation in which The Doctor has found himself, it is more in reference to the question Martha has just posed regarding who had the most No.1 hits, Elvis or the Beatles.
The basic plot line, - alien infested crew member hunts down and kills crew of isolated space ship - is a take on Ridley Scott's Alien.
The Doctor: Where’s your Dunkirk spirit?
’Dunkirk spirit’ is a phrase used to describe the tendency of the British public to pull together and overcome times of adversity. The idiom came into use following the evacuation of allied troops across the English Channel at the Battle of Dunkirk in 1940, when Royal Navy ships were aided by pleasure boats, working barges and other civilian craft.
The episode title number 42 is very significant in science fiction circles. In Douglas Adams' celebrated Hitchhiker's Guide to the Galaxy series 42 is established as being the Ultimate Answer to Life, the Universe and Everything. The quest for the Ultimate Question to match the Ultimate Answer led to the creation of a massive planet-sized computer called the Earth. This is not the first time the Hitchhiker's series has been referenced on the program. The Doctor compared himself to the series protagonist Arthur Dent in The Christmas Invasion. Douglas Adams also served as story editor for the original Doctor Who's seventeenth season.
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