The concept, widely used as a rule of thumb by astronomers, was codified last year by Dr. Mendez and his colleagues into a more formal Habitable Zone Distance scale.

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To do so, he follows an old rule of thumb used by mothers and psychologists to get people to change their behaviour.

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Subtract all expenses and property taxes (30% of the rent is a good rule of thumb) and multiply by 12 to get the annual net operating income.

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The usual rule of thumb for screen size, by the way, is that you should sit about 2.5 times as far away from your TV as the diagonal measurement of the screen.

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The rule of thumb is that a 10pc rise in crude cuts US growth by 0.2pc four quarters later, but the science is flabbily soft and nobody knows where the inflexion point lies.

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His rule of thumb appeared to be, first: Is this a project proposed by a Republican?

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Often we accept people into our social networks by extension of trust, i.e. a friend of a friend, so a good rule of thumb might be to question how well you really know a person before accepting a new friend request.

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The rule of thumb is that 100 rems of exposure increases the chance you will die of cancer by 5% or so.

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As a rule of thumb, a careful cull of the 10% of lowest performers can make a firm leaner by removing fat without damaging muscle.

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