Archive for November, 2017

How do we know anything?

November 18, 2017

How do we know Anything MdeP-NPL

This is an edited video of a talk I gave recently to the NPL Postgraduate Institute about the forthcoming changes to the International System of Units, the SI.

It’s 36 minutes long and you can download the PowerPoint slides here.

It features the first ever public display of the Standard Michael – the artefact defining length in the SM, le systeme de moi, or My System of Units. (It’s shown at about 6 minutes 40 seconds into the video).

The central thesis of the talk is summarised in the slide below:

Measurement

In the talk I explain how the forthcoming changes to the SI will improve future measurements.

I hope you enjoy it.

 

Before understanding comes familiarity

November 14, 2017
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Averil Horton

It is tough being an adult. Hey. We all know that.

But is especially tough if you realise as an adult that science fascinates you. There are relatively few places where you can go and learn about science  without being condescended to, or treated like a child.

I tried to create such an environment when I ran Protons for Breakfast and my friend Averil Horton is now trialling her ‘Science Club’ with adults.

I am attending as a helper – which is delightfully low stress compared to running a class!

And the key insight of which I have been reminded repeatedly is that experience has to come to before understanding. And for adults, just gaining exposure to the experiential pleasure of hands-on experimentation is so difficult!

I won’t describe the classes in detail, but below I will just post a couple of pictures showing the kinds of things people do. And with the exception of a couple of potentially dangerous things – everyone does everything!

Cutting Potassium…

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Chromatography…

Colours

Growing Silver…

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Burning Magnesium…

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Experiments with density…

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Burning hydrocarbons…

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And we are not even half way through!

Measuring Temperature with Sound

November 12, 2017

Measurement

I have just given the first of a series of five talks for The Training Partnership, a company that provide ‘enrichment’ days for A level students.

Since one of my key messages is the importance of measurement in science, I feel obliged to perform some measurements during the presentation.

I find this worrisome, but I think it works well. When it works!

Anyway, with four more presentations to go I thought I would create a page with links to all the the resources I use in the talk.

PowerPoint

The PowerPoint presentation can be found here. Please feel free to steal animations if you think they will be helpful, but please give credit to NPL.

Software

During the presentation I use:

  • Audacity for capturing acoustic wave-forms and analysing them: it is astonishing software, and completely free.
  • Sound Card Oscilloscope for detecting the resonance within the spherical resonator: it is excellent and free for educational users. It also comes with a built in oscillator, but for the demo it is much clearer if I use a separate device. So I use…
  • Signal Generator, an app for IOS devices. There many others for both IOS and Android but this one is fine and costs £0.99.

And this is the spreadsheet I use to interpret the results from the experiment.

Hardware

In my talk I use the same microphone for all the demonstrations, a commercial lapel microphone from RS Components (RS Stock No.242-8911which costs about £20. Similar devices are available from other suppliers.

I chose this particular model because it more robust than home-made contraptions and has a small head – so it fits inside tubes. Larger microphones will work but they tend to damp acoustic waves more strongly.

I hold it in place with a blob of Blutac.

The miniature loudspeaker I use for the resonator demo is quite specialised. It is from a range of products used in headphones, mobile phones and hearing aids produced by the Knowles corporation.

think the model I used is  from this ‘BK’ series. It requires wires to be soldered onto very tiny terminals, and then wired to a 4 mm jack plug that can connect to a mobile phone.

One alternative would be to dismantle a pair of in-ear headphones and just use the loudspeaker from one earphone.

Tube and Resonator

The metal tube I use in the talk is 1.1 metre long stainless steel tube approximately 9.5 mm diameter. You can also use many other types of tubing such as copper or steel plumbing tube.

In general, longer is better for more accurate measurements at room temperature, but it is obviously more difficult to heat it uniformly.

The resonator is a 3-D printed version of the copper resonator we used to measure the Boltzmann constant and make the most accurate temperature measurements in history.

I have placed the 3-D printing files in a zipped folder hereThere are files for the Northern Hemisphere, the Southern Hemisphere, and the plugs. Creating the resonator is quite complicated and I will write a separate blog post on that later.

Good luck!

 


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