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It has been said multiple times that the sonic screwdriver doesn't open, move, change anything made of wood.

Why is that? It is sonic!

The type of material should not affect it. The Sonic Screwdriver has worked on a multitude of materials, but never wood.

no wood embarrassing

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    Because Dr Who is a British show and we Brits have a sense of humour. :-)
    – Stevetech
    Jun 8, 2012 at 17:03
  • I distinctly recall an episode where ex explains that it's cause wood has no moving parts, but I can't recall the episode, and therefore can't cite anything, so I'm only running it as a comment.
    – VBartilucci
    Nov 6, 2018 at 19:10

4 Answers 4

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Technically, the sonic screwdriver shouldn't be able to do nearly as much as it does in the series (open doors, reprogram Cybermen, adjust any of several other devices of largely arbitrary function). It is, sad to say, a magical "do anything" device.

As such, throwing in an arbitrary weakness, like being unable to do anything to any wooden objects, allows the writers to add tension to a story. If your all-powerful device suddenly can't do anything, then you are in a bit of trouble and need to find a new way out.

I honestly don't know if there is an explanation that involves the in-universe "science", but the inability of the sonic screwdriver to work with wood seems to be an addition to keep it from being used in too many deus ex machina plot resolutions.

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    I think it's interesting that, when the new series started, they kept having things have a deadlock seal as the sonic-thwarting mechanism when plot required it. Since the "it doesn't do wood" claim, it seems they've moved over fully to having things just be wooden. I'm assuming this is for humor factor, but maybe "it's wood" is easier to pass off for audiences.
    – PeterL
    Jan 14, 2013 at 15:37
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    +1 for Deus ex machinia. It seems anytime the Doctor is stuck, he presses the button, and presto! the screwdriver has a setting to get him out of that problem. I think the whole "doesnt work on wood" is a sort of wink wink by the writers, telling us they know they've overused it
    – Shantnu Tiwari
    Jun 6, 2013 at 13:48
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    There’s a great deal it can’t do, actually. A good computer programmer can open doors and reprogram machines, but they’re hardly omnipotent (even if they can’t do anything to wood).
    – Adamant
    Nov 2, 2017 at 3:59
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Rule 1: The Doctor lies. Also as Jonathan Thiele Stated it is a good plot device. But let's look at a real world example we have sonic welders http://en.wikipedia.org/wiki/Ultrasonic_welding which do not work on wood. Also wood is a hard organic material, a natural composite of cellulose fibers (which are strong in tension) embedded in a matrix of lignin which resists compression. (according to wiki) It is often used in musical instruments with different woods affecting the sound and tones emitted. So since the Doctor's Sonic Screwdriver is sonic it could be that wood is one of the few materials able to resonate and distribute the sound directed at it.

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    Ever hear a woodpecker that found a dry enough tree? You can hear it from a good distance for such a small bird.
    – Kogitsune
    Jun 8, 2012 at 18:22
  • @Kogitsune Is the sound that you hear from the tree or the woodpecker's beak?
    – CamelBlues
    Jun 8, 2012 at 18:26
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    It originates from the beak, but the tree acts as a very large speaker.
    – Kogitsune
    Jun 8, 2012 at 18:56
  • The reason ultrasonic welding doesn't work on wood isn't because sound doesn't work on wood, it's because welding doesn't work on wood.
    – David Conrad
    Jul 20, 2015 at 17:56
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From a physics POV:

The screwdriver is sonic. That means it works by emitting sounds of the resonant frequencies of objects and vibrating them in such a way that work gets done. It seem a bit advanced in that it can affect electrical systems too, and it seems to have the capability of doing the exact calculation of the sound required on its own. It can scan by using a system similar to sonar, which will help it pick up resonant frequencies in the first place.

Metal is easy, a single metal part has a couple of well defined resonant frequencies and can be targeted easily.

Wood is not. Wood is organic, and as such a wooden part is much more complex when it comes to finding resonant frequencies (or even having resonant frequencies). There's also extra damping, so any resonant frequencies you have might not be effective.

The screwdriver does work on Flesh, though, which is organic. This might be due to the Flesh internally crystallizing to form the solid body (liquid crystals and similar substances are easier to resonate). Alternatively, it might have some nanobot-like components.

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    I believe this is the "correct" answer, and it is also backed up by the long calculation required to vaporize the wooden door in the Tower of London in "The Day of the Doctor".
    – Keavon
    Aug 23, 2014 at 6:14
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IMHO it's related to how it cannot kill, wound or maim living things (Doomsday) and wood has cells. Dead cells, in case of furniture, but cells nonetheless. Must throw off the Sonic.

However, chances are that it just doesn't. The Doctor (Matt) does say at some point that he should fix it.

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