A scene near the end of the Day of the Moon shows the doctor conducting a surreptitious pregnancy scan of Amy. The result oscillates between positive and negative. This is a phenomenon my daughter, and I expect a lot of other fans, have dubbed a "quantum pregnancy" or "Schroedinger's baby."

It occurred to me that one explanation of this oscillation could be that the Doctor will change his behaviour depending on the result of the scan. The eventual outcome of his knowledge of a pregnancy is to cause there to be no pregnancy. But the event leading to the pregnancy is in the past on the Doctor's timeline.

One possible cause of this is that in future he will cross his own timeline.

I won't pretend to understand the pseudo-science involved in Who time lore, but other circumstances we know about suggest that it is essential that the Doctor deduce that something so catastrophic will happen at some point in his future that he will desperately try to send himself a signal, even at the point of his own death.

The oscillation was whilst the scanner was scanning. The camera then cuts to the Doctor's face, we then hear a 'beep' to suggest that that scanner has finished. So only the Doctor knows the result and not us the viewer.

I really don't think the scanner was flipping between positive/negative because there was no baby or there was something 'wrong' but it was simply starting its scanning process when we saw it on screen for ourselves.

So imo the positive/negative oscillation wasn't the result but the actual scanning process

On another thread ("Spot the allegory") I've developed a hypothesis that the Doctor's death is staged by him as a coded message to his earlier self. Similarly I think the apparently frivolous messages, the "waving from history" are actually from the older Doctor and intended to be decoded by his younger self.

It's pure speculation, but I think this pregnancy scan and the odd result gives my hypothesis an interesting twist. Since Blink we've seen how Steven Moffat loves a time paradox. There's obviously a huge paradox involved somewhere here and I'm just trying to make sense of it.

What he said.

Maybe I'm being thick but I keep seeing these terms... could someone please explain what they mean?

Thank you

Oh now that sounds like a logical explanantion. I like that. can get my head round that one

I'll watch it again because that's an interpretation that I hadn't considered.

Still if you have a TARDIS available and in late July you ask it to carry out a full body scan on a woman who thought she might be pregnant in late April, you'd think it would be able to detect the foetal heartbeat. Forget Doctors, even the dimmest medical student can do that with nothing more than a stethoscope!

I think this is tied in somehow with the Silent's order to Amy in the toilet, that she must tell the Doctor what he must know and what he must never know. We naturally assume that the Silent refers to two separate facts. What if it refers to one fact, her pregnancy, which he must never know?

I don't think the TARDIS scanner would take that long to scan and come up with a result.

I think it was oscillating because at that moment in time it is 50:50 between two alternative timelines and the TARDIS is calculating which one will come out.

So, there is one timeline with a pregnant Amy and one where she's not pregnant.

Every part of the series' step is now determining this timeline outcome.

I bet the Doctor is aware of the implication ...

She did follow the command - she told the Doctor 2 things:
a) she's pregnant
b) that he's being killed (attempting to save his live which she is trying to prevent by shooting the astronaut)

The implication is obviously that the Silent wanted the Doctor to know this. Obviously he knows the Doctor and has a reason for him to find out. So, I wonder why? Obviously to influence his actions in a specific way ...

They are referring to the thought experiment of Schrodinger's cat, the extreme basics of which I think are that when the cat is in the box it may be dead (due to the poison released after the random act of radioactive decay) or alive. Without being able to see into the box, it is impossible to know which, therefore the cat may be assumed to be dead and alive at the same time.

Please feel free to correct my extremely dodgy quantum physics

The term refers to a thought experiment by the classical physicist, Dr Schroedinger. The good doctor thought the Copenhagen Interpretation of Quantum Mechanics was fundamentally absurd and to illustrate this he constructed an imaginary scenario in which, according to the Copenhagen Interpretation, a cat in a box would be neither alive nor dead but in a weird indeterminate state until the experimenter opened the box. Despite this the Copenhagen Interpretation prevailed. The term "Schroedinger's baby" is an analogy, comparing the existence of the pregnancy as an outcome of some past sex act to the alive or dead state of the cat in the thought experiment.

This could be related to the more famous grandfather paradox.

For details of the thought experiment and its interpretation in folklore see the relevant Wikipedia article.

^^

Thank you - all is clear now

I did that and I still think that's a perverse interpretation, considering how easy it is to detect a 3-month-old foetus. But writer's licence means I have to grant you that one. I have to admit I've seen even more stupid user interfaces than that.

There really aren't that many slim healthy women who can't tell whether they're three-months pregnant. This is a very bizarre situation.

Maybe it will have a time head! But that's not what you're thinking and it's not what I'm thinking, and it definitely isn't what the Doctor is thinking.

Yes, that's my first interpretation. I stand by the alternative interpretation which I outlined here. it's more exciting but it could be ridiculously and stupidly wrong.

To recapitulate: I think the oracular command was to tell him that she is pregnant, and the reason is they know the knowledge will lead to a paradox. He must know this and he also must not know it. They're messing with his head, yes. but they're doing so in a particular way that, I think, will prove to be characteristic of their methods.

I could be, and almost certainly am. completely wrong. So please don't get worked up about this.

In fact, no,

If I kill my grandfather, then I no longer exist.

If I no longer exist, I can;t have killed my grandfather.

Therefore, a time paradox oscillates between 2 states.

Shroedinger's point was that quantum formalism implies self-contradiction, ie, meaningless gibberish with no referents.

Well in the cat box story there is no oscillation but actually a wave equation that has two distinct solutions, and Schroedinger felt that this was offensive because, he believed, reality does exist and always has one value. A result that describes the cat as neither alive nor dead, he felt, betrayed the assumptions about reality that allow us to know anything.

In trying to relate this to the infamous grandfather paradox I suppose my thinking goes like this:
[LIST][*]Take one young person[*]Place him into a TARDIS[*]Convince him that killing his grandfather might be a good idea[*]Tell him how to travel in time[*]Put him back where he was[*]Bugger off to wherever you came from[/LIST]
Now he might be able to create a time machine and go back and kill his grandfather and the rest of the world will never know he existed, but we're time travellers and we set this whole thing up, so where does that leave us?

I think Steven Moffat is working in that area, where okay there are closed loops and obviously natural selection will weed out people who are prone to murdering their own grandfathers (unless they go on to marry their grandmothers, but that's a separate subgenre), but for the time traveller the story is different. You can see history changing and quite often it doesn't affect your ability to perceive the change.

I don't think I made it clear earlier: I think this is the point at which Doctor Who realises that his future self is doing alarmingly dangerous things, and trying to attract his attention. One of those things might be, for instance, having it off with a scrumptious redhead who gets randy and likes to explore the unexplored.

The above is a bit incorrect. He actually had a dog. Schrodinger had a rare eye disorder called 'animal blindness'. The condition makes it impossible to differentiate between cats and dogs. He thought his cat, called Twinkles, was a dog even though it barked and slept in a kennel.

Remember when Rose saved her Dad from dying in the first series? She didn't really remember having lived her life with a father, but look at what happened. Some weird mutated pterodactyls started eating everyone xD

I mean, yes. Your point stands: it doesn't affect how the time traveler perceives the events or whatever has yet to come, but based on what we've seen from pre-Moffat episodes, I think it's established that we can't kill our grandfathers or save our ancestors from their unwanted deaths without causing chaos. Just a thought xD

Now about the baby: I think that bleep in the end was obviously there for a reason. The TARDIS could've identified if she really was pregnant rather than have a Schroedinger's baby.

Now I have a theory that this is what actually happened: Amy saw a Silent in the bathroom and it suggested that she tells the Doctor that she is pregnant (prior to this Amy may have figured out that she was possibly pregnant and had no plans of telling anyone, not even the Doctor, because it might have three heads or a Time head. In reality, she probably wasn't really pregnant at all, the Silent simply used Amy's gut feeling about her pregnancy to confuse the Doctor and everyone else in the future, perhaps?) Now why would the Silence do this? Well remember when they have held Amy captive for days? Quite possibly, they have implanted a time baby in her which could explain why the TARDIS didn't have an easy time identifying that she was pregnant. The post-hypnotic suggestion about telling the Doctor may have been a not-so-perfect but passable cover up in the part of the Silence.

I have never ever ever ever heard of Schroedinger's baby. Where does it come from? Am I supposed to know?

No. It's not a real thing. It's a joking reference to quantum mechanics.

When I was pregnant with my eldest I was almost 6 months before I started showing and know plenty of people who weren't showing any signs of pregnancy at 3 months.

I think my friend in Edinburgh has hit it on the nose - IMO it is NOT a quantum pregnancy at all.

IMO Amy's pregnancy may well rely on a choice she makes in the future, so whilst her time line is in flux, both outcomes are possible.

Thank you. You can probably tell I am no scientist. Oh my god! I have turned into Jo Jones!!