Another thought on Higgs

Another incomprehensible image typically used to illustrate stories about the Higgs Boson. It shows ‘things’ shooting out from the point where two protons have been smashed together. Picture stolen from The Guardian

I had one more thought about the recent discovery of the Higgs particle: if the Higgs is the particle which gives ‘mass’ to all the other particles, then surely the nature of the Higgs must be linked to the nature of gravity?

As you may be aware, the concept of ‘mass’ enters our lives in two quite distinct ways: as inertial mass and as gravitational mass.

• Inertial mass is the property of an object which makes it harder to speed up or slow down. This is encapsulated in Newton’s Second Law of Motion: that the amount of force required to achieve a given acceleration is related to the inertial mass of the object.
• Gravitational mass is the property of an object which makes it attract other objects at a distance through space. This is encapsulated in Newton’s Law of Universal Gravitation: that all the matter in the universe attracts all the other matter with a force which is inversely proportional to the square of the distance between the objects, .

Einstein was fascinated by the simple observation that inertial and gravitational mass were – as well as can be measured – always exactly equal. From this insight he was inspired to derive his General Theory of Relativity which is based on the central tenet – the principle of equivalence – that these two types of mass are not in fact two distinct properties, but one single property.

When scientists say the Higgs particle is responsible for giving ‘mass’ to all the other particles, they mean inertial mass. But this will also have a gravitational effect. I have not seen any discussion of this feature in the news, but surely, if the Higgs particle gives rise to both types of mass, it must provide some kind of link between the two different manifestations of mass. Discovering any kind of connection at all between the Electroweak force, the Strong force and Gravity would really be a major step forward in our understanding of the Universe.

Or maybe I have completely missed the point?

The Gravity 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.

Gravity

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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.