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Resources

Questions and answers

Do you want to know more about metrology and the science of measurement?

Have you ever wanted to know the answers to the most popular questions about measurement or physics?  What is the difference between metrology and measurement? Why is the science of measurement important? What are the laws of physics? What is physics and why is it important? How is physics used in everyday life?

What is a leap second?

An occasional leap second adjustment ensures our clocks reflect the Earth's rotation speed as accurately as possible.

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What is net zero?

The UK has committed to bringing all greenhouse gas emissions to ‘net zero’ by 2050, but what does this mean?

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How are greenhouse gases measured?

Greenhouse gases in the Earth’s atmosphere are increasing. So how do we define and measure the greenhouse effect?

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How do scientists measure the temperature of the Earth

Many aspects of the earth’s temperature can be measured, each with their own relevance and techniques. 

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How and why do we measure the colour of the ocean?

What role does ocean colour play in measuring climate change?

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What is a National Metrology Institute?

NMIs realise, maintain and develop their country’s primary measurement standards.

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What’s the difference between metrology and measurement?

Both are fundamental to human activity, but what’s the difference?

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Is midnight 12am or 12pm?

The meaning of 12am,12pm, midday, midnight and the 24-hour clock

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Is there a difference between measurement 'accuracy' and 'uncertainty'?

When used in measurement it is vital to use the correct word

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When do the four British seasons dates officially begin?

There are no official definitions of the duration of spring, summer, autumn and winter, so what are the british seasons dates?

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Why does atmospheric pressure change with altitude?

Atmospheric pressure reduces with altitude for two reasons, both of which are related to gravity.

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What is the difference between density and specific gravity?

Both are used to describe mass and to compare substances

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Why is my radio-controlled clock not showing the correct time?

What can you do to ensure you receive the correct time?

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What is the scientific definition of a vacuum?

The definition of a vacuum is not precise but is commonly taken to mean pressures below, and often considerably below, atmospheric pressure.

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What are g-forces and are they caused by gravity?

The term g-force is used to convey values of force and acceleration.

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What is the SI unit of force?

Historically, there have been a variety of units of force and conversion factors.

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What are the differences between mass, weight, force and load?

We use these words on a daily basis, but do you really know the difference?

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How is air density determined?

Air density is used in many branches of science, engineering and industry andy can be measured in two broad categories, Indirect measurement or parametric method and Direct measurement.

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How do I convert between dew point and relative humidity?

There is no simple formula for converting between dew point and relative humidity.

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The difference between a transducer and a transmitter?

Both devices measure pressure, but what’s the difference?

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What is emissivity and why is it important?

What is emissivity? All objects at temperatures above absolute zero emit thermal radiation.

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What is a platinum resistance thermometer?

A platinum resistance thermometer (PRT) contains a piece of platinum wire, whose electrical resistance is proportional to temperature.

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How small is the world's smallest Christmas card?

The world's smallest Christmas card requires a powerful microscope just to see it, helping to unlock new battery and semiconductor technologies.

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What is platinum?

Platinum is one of the rarest and most precious metals. It is used to represent 70 year celebrations – birthdays, anniversaries and, recently, the Queen’s Jubilee.

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How hot is the hottest Christmas pudding?

NPL's temperature experts created a graphite Christmas pudding and placed it in our high-temperature furnace.

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