88 Miles per hour/Teacher Notes
From OER in Education
Teacher's Notes
Session 5 – 88 miles per hour
- This session looks at the question of time travel and other topics in the context of why we don’t understand everything. It aims to introduce the concept of modelling and points out how far we have to go to get a complete picture of everything.
- 88 mph is the speed at which you must go to travel through time in Back to the Future (The trailer shown in the introduction). Are time and space really the same thing – can you Travel in Time?
- Example - you are asked to guess a number sequence which increases by +2.2 each time. When displayed to zero decimal places, the first 4 numbers follow a regular pattern but then the model that we use (adding just 2) breaks down. Going back to the drawing board often happens in science. One observation can cause a whole theory to be questioned and changed
- Example from chemistry
- - Model of atoms as smallest building blocks
- - Plum pudding model
- - Understanding of a nucleus (Rutherford)
- - Charged particles in a nucleus
- - Quark model (see session 4)
- New evidence and experiments lead to models being refined. It is NOT that the old models are wrong – or that the people who first stated them were stupid – more that new evidence makes a better model possible – however it is still just a model and will no doubt be improved in the future.
- Lord Kelvin made some outlandish statements, but also did some very good science, however it is wrong to consider him stupid for them. Predicting the future is notoriously difficult...
- The theory of special relativity
- - Thought experiment – turning the lights on, on a car travelling very, very fast.
- - Is the speed of light in this case c? Or c + v?
- - http://en.wikipedia.org/wiki/Special_relativity
- - Mickleson-Morley experiment proved it was always c http://en.wikipedia.org/wiki/Michelson%E2%80%93Morley_experiment
- - Thought experiment - Light clock – I suggest you only deal with a brief explanation of time dilation and ignore length contraction.
- - Consequence of this is that as you watch someone move fast you see time slow down for them.
- - Concorde example. Fly 1 clock to JFK and back and leave another @ LHR)
- - Twin example, ignoring the paradox component, a twin visits alpha centauri @ .95c comes back to find her identical twin much older than she is. http://en.wikipedia.org/wiki/Twin_paradox
- - The case of a black hole
- General relativity states that time also slows down in the case of a gravitational field. So time passes faster the weaker gravity is – example the clocks on the GPS satellites have to be constantly corrected. This can lead to extreme slowdowns of time. If you fell into a black hole – your friend watching would see you almost stop completely on the event horizon – whereas you would see all the future of the universe flash before your eyes as you spaghettified.
- Quantum mechanics. Relativity tells us something very strange happens with big and fast things. So what about small things?
- - Key figure Niels Bohr http://en.wikipedia.org/wiki/Niels_Bohr
- - Quantum means “the smallest discrete quantity of some physical property that a system can possess” so a quantum of solace basically means – a very small bit of peace and quiet. It is important because if the universe has a smallest possible size for something – then it will be impossible to measure something smaller.
- - How long is a table? Analogous to the how long is a piece of string http://news.bbc.co.uk/1/hi/sci/tech/8363934.stm
- - Video from the HBO series “the elegant universe” adapted from a book by Brian Greene. The key point is that QM works very very well with the small – and GR works well with the big – but when you deal with something Heavy and small, like a black hole or the “big bang, you get nonsensical answers as you have to use BOTH. Therefore there is something wrong with one or both of these foundational theories in science.
- - Close is often good enough. Video to show we got to the moon without worrying about it.
- - But sometimes it isn’t. Video - Chloe and Keith’s Wedding clip is a setup, but it is still funny...
• Pioneer Anomaly also points to potential wrongness in theory of gravity. See http://en.wikipedia.org/wiki/Pioneer_anomaly
End of Session 5
Cloudy weather options
• Video task from session 4
• Describe in a leaflet to a friend why time isn’t constant!?
• Invent your own theory of the universe (you get to name it after yourself)
