The spire is shorter when the weather is cool.

It's pretty well known that metal expands when it gets hotter – and that's what happens to the spire. It's taller in summer than it is in winter.

Opening a Jar

Your jam jar won’t open. We've all been there.

Pouring hot water over the lid helps to solve the problem. While the metal lid and the glass jar both expand upon heating, the lid expands to a greater extent making it easier to open the jar.

The temperature of an object is related to how much energy it has – cold objects have very little energy compared with hotter ones.

All materials are made from atoms that are bonded together.

If you take a cold object and heat it, each of the constituent atoms start to move around a lot – and the moving atoms push out to take up more space. That’s why hot materials occupy more space than cold materials.

Different materials expand...

Different materials expand and contract at different rates because of variations in how atoms are bound together. Materials that have atoms tightly bound together will expand less, because even with the extra thermal energy, the atoms are physically constrained. So liquids expand more due to heat than solids do, and disordered solids like glass expand more than ordered solids like metals.

The Spire is made from stainless steel, an alloy of iron, carbon and chromium. Over a typical year temperatures in Dublin can range from ­-5°C to 25°C. This 30°C variation causes the Spire’s height to vary by about 0.5% – around 5cm.

Making the spire

Officially named the Monument of Light, and standing in the same spot where Nelson’s pillar used to be, the Spire has become an important Dublin landmark since its completion in January 2003.

The Spire was designed by Ian Ritchie Architects and manufactured in Waterford. Made from eight hollow tubes of stainless steel, it contains a tuned mass damper – a device which stabilises structures against vibrations caused by wind, traffic and even earthquakes. The seemingly abstract patterns on the base of the Spire are actually based on a core sample taken from the site that the structure is built on. To date, the Monument of Light is the world’s tallest sculpture.

The expansion of materials

is one factor that engineers have to take into account when they’re considering how structures should be built. And we see the effects all around us.


It's not just metal structures that expand when heated.

Concorde, the supersonic jet retired in 1999, was almost 25cm longer in flight than on the ground due to the friction caused by the speed it traveled at. It’s nose cone heated to 127°C. On a normal jet flying today, an airframe usually operates at temperature of around -50°C. That’s a difference almost 180°C!

There's a lot more to understanding heat expansion than using it as a trick to open stuck jam jars.