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Einstein's time

Learning objectives

This is a simple way of introducing students to the complex idea of time dilation. They practice speed calculations, use graphs to read off a scale factor and convert one quantity into another and appreciate that time dilation is only noticeable at speeds very much greater than those they are used to.

Try the activity

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Curriculum link

9K Speeding up
that speed can be determined by measuring distance travelled and time taken.
the units in which speed is measured.
to manipulate and apply the quantitative relationship linking distance, time and speed.
to use understanding to evaluate the contribution of a scientist/inventor

Running the activity

Most pupils will be familiar with the format of TV talk shows like Trisha. In this activity they role play a Trisha situation. It is 2050, and twins born on 1st January 2000 are on the show. But they have aged very differently. One twin remained on Earth while the other travelled the Universe at 96% of the speed of light - experiencing time dilation as a result.

Answer to the time dilation problem

The interview takes place in 2050, and they were Millennium babies so the first twin is 50. Only the time spent at speed counts towards time dilation. The time spent exploring the planets is effectively the same as Earth time. For the 30 years spent travelling at 96% of light speed, the graph shows aging was 28% of that for the twin left at home, or 8.4 years. So Jal would look about 28 and a half compared to the sister who is 50.

Answers to the speed calculations


A person walks at 3 m/s
An athlete runs 10 m/s
A cheetah runs at 35 m/s
A racing car travels at 60 m/s
A rocket flies at 11 000 m/s
But light travels at 3 000 000 000 m/s

If you never thought it possible for 11-14 year olds to grasp time dilation, have a look at the ASE's School Science Review Journal (Mar 2005, 86(316)). There's a nice physical simulation where students act as photons from a clockface - it really does get over the essential idea about relative time.

Web links

News links

Wikipedia

For teachers: What's the Twin Paradox and where the trick is. Not for KS3!

IOP

Time twins game (needs sound) with links to information about relativity.

Wikipedia

Biographical information with clever quotes at the bottom of the page like "When a man sits with a pretty girl for an hour it seems like a minute. But let him sit on a hot stove for a minute and its longer than any hour. That's relativity."

IOP

Short but serious Relativity Primer

Georgia State University

Muon experiment for the purist!

Economist

Economist article on 100 years since Einstein's "memorable year".

BBC

Could he have had Asperger's?

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