MAYBE it was a viral pandemic, or an asteroid strike, or perhaps nuclear war.
Whatever the cause, the world as we know it has ended.
Now you and the other survivors must start again.
What key knowledge would you need to start rebuilding civilisation from scratch?
Once you have scavenged what you can, how do you begin to produce the essentials?
How do you grow food, generate power, prepare medicines, or get metal out of rocks? Could you avert another Dark Ages or take steps to accelerate redevelopment?
If you would like to hear some possible answers to these questions, and others like them, come to Portsdown U3A’s annual lecture.
Dr Lewis Dartnell is an astrobiologist who is professor of science communication at the University of Westminster.
His lecture, based on his bestselling book, is called The Knowledge: How to Rebuild our World from Scratch. Transform your understanding of the world as it is by considering what it would be like if it ceased to exist.
The lecture will take place at 2pm on Wednesday, November 30 at Cosham Baptist Church, 48 Havant Road, Cosham, Portsmouth.
This is a free event, but you need tickets from me.
Please call me on (023) 9269 7009 or e-mail firstname.lastname@example.org.
Portsdown U3A is an organisation for people who are no longer in full-time employment and who have an interest in learning.
We normally meet at 2pm on the third Wednesday of every month, except August, at Cosham Baptist Church.
We also have a wide range of interest groups.
You can find out more about us when you come to our annual lecture, and there is more information at portsdownu3a.org.uk.
Carole Chapman is from Portsmouth U3A, an organisation for retired people who want to continue learning.