You need to login before you download the free activities. You can register here.


Einstein's time

  • Key Stage 3
  • Popular Activity
  • Topical

Type: Activity
Learning Strategy: Data work
Topic: Laws of motion

A hundred years ago this week Einstein turned 26. He'd been shy at school and a slow learner. He was dyslexic. But in 1905 he had a terrific burst of scientific creativity. He turned in three essays - each one a cracker - with radical new ideas on different bits of science. He's most famous for a totally new take on time and speed that scientists still use now. His ideas have inspired science fiction writers and given us hundreds of episodes of Star Trek. But they have a practical side too. They led to the development of Satellite TV, GPS, nuclear power, Hi-fis and computers. This activity looks at one of the weirdest outcomes of his theories: what happens if a twin travels around the galaxy at ultra high speeds and then comes back to her sister. You don't have to understand relativity to work it out – you just need a graph and a calculator!

The activity is supported by the Institute of Physics as part of their Einstein Year celebrations.

Published: 16th March 2005
Reviews & Comments: 4

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

You will need Acrobat Reader installed to open the activity sheets.

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.

News links

For teachers: What's the Twin Paradox and where the trick is. Not for KS3!
Time twins game (needs sound) with links to information about relativity.
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."
Short but serious Relativity Primer
Georgia State University
Muon experiment for the purist!
Economist article on 100 years since Einstein's "memorable year".
Could he have had Asperger's?

Reviews & Comments

Write your online review to share your feedback and classroom tips with other teachers. How well does it work, how engaging is it, how did you use it, and how could it be improved?

parts missing?

Jun 13th, 2010

3 Star

This looks like a good activity but are there parts missing? Where is the Trisha interview?

Reviewer: clare gore


Mar 17th, 2009

5 Star

i have discovered this site and i am very impressed with it and suspect i will be using it a lot! in the future

Reviewer: kim clowes


Jan 27th, 2008

5 Star

Very helpful for more able pupils. Makes them apply knowledge learnt and challenges their ideas.

Reviewer: Kathryn Gibbon

Spelling mistake!

May 21st, 2006

3 Star

Could the correct spelling of metres be placed on the pdf file re: Einstein's Time Dilation. Thanks! (Studied time dilation on my physics degree course and here I am, 35 years later, teaching it to 13 year olds!) David Greenway

Reviewer: David Greenway