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Sciencey Wiencey: The Weeping Angels – Quantum Locking

Guest contributor Caleb Howells investigates more Who science.

Don't blink. Again.

In 2007, Steven Moffat struck gold with one of the most critically acclaimed episodes ever, and also one of the most popular monsters. The Weeping Angels were a very simple, but very clever idea. As long as you can see them, they’re just statues, but as soon as you look away, they can move. It’s a creepy idea, and one that I could relate to as a child. Lying in bed at night, I would keep staring at whatever was scaring me on that occasion, certain that it would do something if I stopped looking at it.

I don’t know how exactly Steven got the idea, but he chose to use quantum mechanics to explain how they worked. They are “quantum locked” only in their statue form when someone’s observing them.

Before I continue, I’d just like to give a brief explanation as to how quantum mechanics work. There are various different aspects other than the one we’ll be looking at, and they’re all fascinating, but irrelevant. The Weeping Angels only use one concept, and that is that of the true state of electrons (sort of).

In school, you would have been taught that electrons orbit round the nucleus of an atom in much the same way as planets orbit a star. This is not the case. They don’t move in such boring, linear ways. They are essentially all around the atom at once. They don’t “decide” where exactly to be until someone looks at them. As I said, that’s just one aspect of quantum mechanics and there are plenty of others.

However, objects only behave like this on a very small scale. Large scale objects appear to have their own, different laws of physics, which is why there’s so much talk about trying to come up with a unified theory.

So, as I said, large scale objects don’t behave like that, so how can the Weeping Angels? Well, here’s something which I’m sure you’ll agree is very, very interesting. Scientists have found that the closer something is to absolute zero (-273.15 degrees C), the more it behaves like it does on a quantum scale.

To clarify: Heat is, in actuality, the vibration of atoms or molecules. The more they vibrate, the hotter the substance measures. Absolute zero is the temperature at which there is no movement whatsoever. The substance has no energy at all. Scientists haven’t been able to make anything this cold, but they’ve come very, very close.

Now, as I said, things tend to behave in a more quantumy way when they’re really, really close to absolute zero. However, as I mentioned earlier, there are many different aspects of how things behave on a quantum scale. The whole ‘doesn’t decide where it is until you look at it’ thing is only one aspect. Quantum mechanics is very complicated (and due to how new a science it is, if you go into too much detail you’re likely to be out of date to one degree or another after not very long), and if there really was a creature that behaved in a quantum manner then doors wouldn’t be able to stop it – it could just teleport to the other side.

time-of-the-doctor-tv-trailer-(9) weeping angel

So this is really a very messy explanation for how the Weeping Angels could work. You can only cheat the laws of physics so much. But, because there’s still interesting science to tell you about, let’s just assume for a moment that you could make a statue-sized object be at virtually absolute zero. It would, obviously, be very cold! So naturally, it would make everything else around it utterly freezing as well. How could we get around that?

Well, first of all, let me explain what ‘cold’ really is. Heat is the vibration of particles, as I stated earlier. If something is really hot, its particles are vibrating a lot (the Kelvin temperature scale is directly based on this fact – hence it has no minus numbers, because 0 Kelvin is the absolute absence of energy). So if something is really cold, then its particles aren’t vibrating nearly as much. So what is it, exactly, that you feel?

You don’t feel the kinetic energy of its particles. No, what you feel is the kinetic energy of your particles being taken away. This is because everything wants to be at the same temperature. It’s very similar to diffusion in water. If you put two liquids in a cup, they won’t stay apart. They will diffuse together and be completely evenly spread out. And it’s the same with temperature. So the cold thing that you’re touching will try to take away your heat until both you and it are at an equal temperature.

This explains why some things feel colder than others, even if they’re actually not. For example, imagine you had a wooden spoon and a metal spoon. If you put them in the fridge for a while, they’ll end up the same temperature. But then when you touch them, the metal spoon will feel considerably colder than the wooden one. Why? It’s not colder. So why does it feel colder?

It’s because metal is much faster at taking away your heat than wood is. The wooden spoon is equally cold, but it takes much longer for it to take away the kinetic energy from your particles, so it doesn’t feel as cold.

Now imagine you made a Weeping Angel out of a material that was virtually perfect at not absorbing energy. It wouldn’t make anything else cold. So, that solves our problem.

Of course, unless it was truly perfect, it would eventually get warm, and then it wouldn’t have its quantum abilities.

Unfortunately, the Weeping Angels are not conceivably possible. At least, not in a genuine quantum physics way, as the show states. It may well be possible in some other, more conventionally biological way (such as receptors that detect if something’s looking at them – whatever way that would work – and then the outer cells are sent signals which tell them to become ridged), but in terms of being “quantum locked”… no. That wouldn’t work.

Step back in time...

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51 comments
DW_girl
DW_girl

I think we all know that Weeping Angels couldn't possibly work but the theories were very interesting. Not usually one for physics (I'm a Chem and Bio lover, me), but this was genuienly intriguing.

tlkeiss
tlkeiss

So, why large size objects can behave in QM style at low temp?  after a quick google, it seems to me the phenomena related to macroscopic quantum effect like superconductivity and superfluidity are mainly due by the large amount of particles behaving like quasi-particles.  But does that really mean we can describe a weeping angle with a wavefunction of a considerable wavelength?  Also, even if they are made of insulators, there can still be heat transfer through radiation right?  Then the church soldiers should have easily defeated them at crash site of byzantium


Nightmarish
Nightmarish

Yay finally! I always like these articles. This one was especially interesting. The only thing is, this doesn't explain how Weeping Angels send you back in time. Maybe they travel in their own little wormhole…? 


JamesStroud
JamesStroud

Great article, really interesting read

NeutronFlow
NeutronFlow

Enjoyed reading your article Caleb. Very informative stuff. 

This line, 'Unfortunately, the Weeping Angels are not conceivably possible.' did make me chuckle though. 

I for one, am very happy they're not really possible! ;)



Adric the Genius
Adric the Genius

As much as I like the Science of Doctor Who to make sense, the fact of the matter is that Gallifreyans and many other species have much more scientific knowledge than us, thus making almost anything possible.

Naryave
Naryave

Interesting topic. Following AbslomDaark AbslomDaark, I would like to make a few clarifications:

1. The material they are made off does not need to be a perfect heat insulator, as they could use some energy (work) to get rid of the heat coming in to stay cold.

2. Even if they behave in a quantum mechanical (QM) fashion, they wouldn't be able to teleport through the door. The door is a classical object, in terms of QM it would appear as an almost infinite potential, thus the probability of tunneling is basically zero.

3. QM manifest not only at very cold temperatures. For example the behavior of electrons in metals at room temperature follows QM not classical mechanics, or superconductivity is possible at 100K.

I think you should read a bit more about QM and rethink your conclusions.

MarlonJBonnici
MarlonJBonnici

"I don’t know how exactly Steven got the idea"

He's said himself he got the idea from the childrens game "Grandma's footsteps"

The Genie
The Genie

Another excellent sciency-wiency article, Caleb.  I feel all enlightened...y...wightened.


Grizzlybread
Grizzlybread

O, thank God! It is not possible, after all. All those statues I was afraid of. Dear me, they're absolutely innocent as it turns out.

Tomb of the Cyberbob
Tomb of the Cyberbob

A nice article. I would only take issue with your final statement that quantum locking wouldn't work.  Clearly it would- because we've seen it on telly, and they're not allowed to lie.   It's simply a case that we aren't clever enough to fully understand quantum locking yet.  Our brains aren't powerful enough....

LordRassilon
LordRassilon

I honestly feel that 'quantum locked' is an horribly bad description of the ability. Instead of this, 'genome locked', or 'temporally disjointed' would probably be better, as it is fesible for a creature to have the ability to modify its genome, alterning carbon, or other base materials at a fine scale, making it rigid. Perhaps 'quantum locked' refers to the ability to rearrange and lock the state of the quanta, within the genetic structure of a creature.


A temporal de-synchronisation would also be possible, if the creature exists in a different temporal state (a different position on Axis-T), so that when an entity from the 'standard' depth of Axis-T observes it, it appears to them, in their frame of reference, as frozen in place.  That makes some sense, from the perspective of the Heisenberg Uncertainty Principle; and to some ideas of my own. The evolutionary defence mechanism shift the creature to a different temporal state, when observed. 

Their ability to shift creatures through time, and absorb the temporal displacement energy, as defined, would seem to best fit this model. 


Beyond this, the idea that this natural defence mechanism would also affect members of its own species has some very odd ramifications, including this: How does the species perpetuate itself? Overall, while engaging a natural mechanism to defend against other entities, it is extremely illogical to believe this would have the same effect on other members of the same species; unless they propagate by some form of mitosis, and are predatory within their own genus.


One important note for you: There is a technical 'Negative Kelvins', but it doesn't have anything directly to do with temperature, as you stated. It's a factor of entropy, and as I remember it, a Negative Kelvin scale, would be impossibly high levels of thermal interaction.

Polyphase
Polyphase

A couple of things that never made sense to me is how the Angels gather together without ever seeing one another and how the hell do they breed

Gustaff
Gustaff

Good analysys Caleb.


However, I'm disappointed you didn't even mention schrodinger's cat. Seems like it fits right up the Weeping Angels' ammo.


I love these sciency-wiency articles. They always make my head go explody-wohdy.

Badwolf2
Badwolf2

im glad they aren't possible they are creepy

Unibot
Unibot

Of course, The Doctor could always be referring to a future quantum theory that is unbeknownst to us, because, well... we can't get everything right! :P

AbslomDaark
AbslomDaark

"then doors wouldn’t be able to stop it – it could just teleport to the other side" - no, not unless it wants to violate causality and thermodynamics at the same time.  "

So, as I said, large scale objects don’t behave like that," - actually they can do. It is perfectly possible to have an object that is on the larger scale behave in a quantum fashion without absolute zero getting involved. An extreme example would be a black hole. It's not that larger objects obey different laws of physics - it's that the countless quantum fluctuations are "averaged out" as you zoom out. It's like listening to a single person speaking, then many thousands - you can make out the words clearly in the first case, but in the second the cacophony of voices becomes effectively random noise and sounds the same regardless. The discrepancy between quantum physics and relativity for example is mainly in the domain of gravity - in a lot of other ways (such as the relativistic orbits of electrons around heavy nuclei for example) they work reasonably well together. When you get to extreme cases (singularities, degenerate matter, the Big Bang etc) it's just not a complete view, is all. As for the Angels? Well, I for one never saw the quantum locking as anything more than an analogy - I think the Angels "physics" is probably meant to be far more complex than 21st Century science can explain, so we're left with just enjoying them as damn good monsters. Though I think that the Silence have the edge slightly - I find an enemy that I don't even remember more terrifying than one that has to be watched - after all, isn't never take your eyes off your opponent a basic rule of combat? 





Americanwhovian
Americanwhovian

What we need is a weeping angel origin story. they were old by the time lords standards. and in an article a while ago someone mentioned a predator of the angels. were they always angels? that sounds like an earth thing

pinkjaguar12
pinkjaguar12

I love these articles - they're wonderful to read.  As a studying biologist, that description about receptors seems plausible.  I would love to explore more into that.

Joncon95
Joncon95

Are you a science student Caleb? Very interesting stuff. As a uni student I can agree with you at how complicated it all gets!

goodnightraggedyman
goodnightraggedyman

Id like to know more about them. like where they come from and were they once time-lords. something that rassilon says in end of time and when we see that woman covering her face like the weeping angels do.

Baker Street is heading Into the Dalek
Baker Street is heading Into the Dalek

Another fantastic article Caleb! I wouldn't even know where to start when writing an article like this - it's very impressive. Not only that, but I actually really understand it because it's very well-explained. I have always wondered about how the Angels actually work, so thanks for doing this (even if they are impossible).

Master Michael Moon
Master Michael Moon

Very well explained article. Now we just need one about the Silence and how people forget seeing them, Moffat's second piece of genius.

Polyphase
Polyphase

Thank god for that last paragraph :)

bulerias
bulerias

This is a nice article but missed the most important thing, which is that quantum mechanics doesn't care whether a *person* is looking at something or not. Pretty much any sort of interaction can qualify as an observation. So any light bouncing off a Weeping Angel, for example, would cause its state to "collapse," regardless of whether or not that light subsequently went into a person's eyeball. It couldn't move around freely and only stop when a human being looks at it because of quantum mechanics.




The Beater
The Beater

I'd say "Fortunately*, the Weeping Angels are not conceivably possible."


Moxx
Moxx

Cor, blimey! Really fascinating stuff, and explained very comprehensibly. Keep 'em coming, Caleb!

The Finn
The Finn

Another cracker of an article, Caleb!

Meh Meh Meh Meh Meh
Meh Meh Meh Meh Meh

Great article! I've been waiting for this for a while. Of course, it's fine that not everything matches up, because Doctor Who is also a fantasy show- and for all we know, in thousands of years, the Weeping Angels might be plausible.

DW_girl
DW_girl

@NeutronFlow I think it should be 'fortunately,' otherwise everyone will be getting sent back in time!

AbslomDaark
AbslomDaark

@Naryave  Thanks for your reply. To explain my understanding and comments further -- The reason why teleportation causes issues is as follows - imagine you are standing on top of a mountain, and could teleport to the bottom of a nearby valley. At the top of the mountain you have a particular gravitational potential energy - when you are at the bottom of the valley, you have *less* gravitational potential energy. So that energy has to go somewhere - typically, it would be expressed as heat. So in theory, if you teleported into a gravity well, you would burn up on arriving - and if you teleported out of a gravity well, you would freeze and draw in energy from your surroundings to reach equilibrium. ST fans please note, Kirk and co should be fried to a crisp by now. If you teleport horizontally and not vertically then there is a smaller issue with kinetic energy as the planet is both moving and rotating, but that's not such a noticeable effect as far as I remember as the difference between start and end point is tiny. That's ignoring the point that teleportation, if instantaneous and regardless of the method, is Faster Than Light travel, and as such violates causality - and any form of FTL is technically time travel, as the Lorentz transformations involved always come out involving the "time" axis. Never mind the issues with Heisenberg precluding you scanning the object to teleport in the first place. So basically, as it stands, modern day science precludes teleportation as well as FTL and time travel - which is not to say that they are impossible, just that we don't have any ways around the laws of physics as we know them. In a Sci-Fi series you get to bend these rules, of course, that's the fun in it - but you cannot use those same rules to explain away that rules bending and expect it to make sense, as inevitably you have to point to a bit of the advanced technology and say "and then a miracle happens" ...  or some pseudo babble. My advice is to suspend your disbelief and just go with it ;-)

Beasts_a_Snarling
Beasts_a_Snarling

@Tomb of the Cyberbob  Do you believe everything you see on telly? Oh, and there's a simple explanation to all of this. Only the Doctor describes the Weeping Angels' as "Quantum Locked." No one else does. Rule 1. The Doctor lies….

The Finn
The Finn

@Polyphase  In TTOA/FAS it's shown that they carve themselves out of stone, IIRC. Remember those half-formed Angels? I think that's your answer to that question. Another might be the "that which holds an image of an Angel becomes an Angel" route.

floppy_who
floppy_who

@Gustaff You've just reminded me of a brilliant cartoon I saw recently: a disappointed cat staring into an open, but empty tin can bearing the label "Schrodinger's Cat Food".....

Calebxy
Calebxy

@Joncon95  No, just interested in science. And thanks. I'm glad you liked it. 

Naryave
Naryave

@AbslomDaark @Naryave I guess we are both saying that quantum behavior does not imply teleportation, just from different perspectives. I think the idea of quantum locking is clever, and depending on how one defines an observation it could work. That's what makes Sci-fi Sci-fi.

In summary I agree with your reasoning, but not with the author's.

Unibot
Unibot

@PrisonerZeroIsACybermen @Ross Jenkins  Partly based on the game and partly based on a weeping angel statue in a graveyard that Moffat and his son came across. When he went back there in the daytime, it was no longer there. :Moffat:





DW_girl
DW_girl

Physics isn't really my strong point, and I don't find it vastly interesting either. This article was alright though.