Posts Tagged ‘Measurement’

Why Measuring Stuff Matters

April 12, 2013
We live in a world in full of vast structures which change imperceptibly slowly, and tiny structures which change imperceptibly quickly. Measurement extends our senses into these realms.

We live in a world in full of vast structures which change imperceptibly slowly, and tiny structures which change imperceptibly quickly. Measurement extends our senses into these realms.

One of the wonders of human psychology is how we deceive ourselves about the true nature of the world.

One of the triumphs of the human psyche is that – even while trapped within our own deception – we can break through and discover uncomfortable facts about the world. Facts that allow us to understand our limitations and learn how to overcome them. Experiments which allow us to experience our own blind spots are a classic example, but in fact we go much further than that.

We trust our measurements more than we trust ourselves. From basic measurements of length and time and mass, we have developed an infrastructure that allows us to make measurements – often simple in themselves – through which the nature of the Universe is revealed to us – despite our very human biases and blind spots. Sorry that sounds so pompous – but that’s how it is!

We make measurements and then we trust them more than our own eyes. If sensors tell us a light is flickering 100 times a second – we believe it – even though our eyes see nothing. If measurements indicate that continents are moving apart at 2 centimetres per year – we believe them – even though we experience nothing.

We have developed techniques of measurement that allow us to see ourselves and our world in richer detail than at any time in human history. Looking just through the open tabs on my browser I see have measurement ‘stories’ on all these themes:

In each case above, measuring things and comparing them with our expectations doesn’t simply provide a number – it allows us to view the world in new ways. And it allows us to extend our vision into the realms of the otherwise imperceptible, or the overwhelmingly vast. And that is why measurement matters!

The Gravity Gnome

April 27, 2012
Weighing a Gnome

Weighing a gnome is actually a way of probing the gravity field around us.

Gravity is the most mysterious of the forces we experience in our lives. Impossible to screen against, it extends throughout space to the farthest corners (corners?) of the cosmos, causing every piece of matter in the Universe to affect every other. Wow!

More prosaically, gravity gives rise to the phenomenon of ‘weight’ – the force which pulls us ‘down’ to the Earth. GCSE students are tutored on the difference between mass and weight, and are told that the weight of an object, say a Gnome, varies from one planet to another, but its mass is the same on any planet. However, the Kern instrument company are keen to point out that if you use a sensitive force balance, its weight changes from place to place around the Earth.

The balance doesn’t even need to be that sensitive. I was surprised to find out by how much the weight of an object measured at a fixed height above sea level changes with latitude and longitude: – it varies by  around 0.5%. So for a Gnome weighing around 300 g, changes of 1.5 g should be seen and this is easily detectable. The rationale for the publicity stunt is explained here, and you can follow the Kern Gnome on his journey here. I like this experiment because the measurement is so simple – and yet the physics it uncovers is so profound.

The light-hearted video below shows my children’s reflections on the mystery of Gravity.

P.S. After a period of steady decline, my own weight has been mysteriously increasing. I think this may be due to a fluctuation in the gravitational constant G. More about this in future articles.


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