Transcript Document
bbc.co.uk/doctorwho FACT OR FANTASY? Who Is Doctor Who? • Time Lord from Planet Gallifrey • Travels in space and time in the T.A.R.D.I.S. • Can regenerate when facing death • Battles against evil enemies Daleks!!! Cybermen!!! Slitheen!!! And even more Daleks!!! Can we all be time lords? 3 easy steps to becoming a time lord… 1. Work out how to travel time 2. Build a time machine 3. Make a sonic screwdriver Can we all be time lords? 3 easy steps to becoming a time lord… 1. Work out how to travel time 2. Build a time machine 3. Make a sonic screwdriver Very cool… Time Travel Special relativity light always travels at same speed for observer (3x108 ms-1) Time Dilation moving clocks tick slower than stationary ones Oh no! That’s just wrong! Enough already! Time Travel General Relativity Time travels more slowly for objects in gravitational fields Space time gets distorted Large objects bends space time more than light objects Ah ha, that’s it! We can curl time back on itself! Wormholes Link 2 regions of space with a wormhole, cunning… Wormholes Wormhole instructions, please read carefully… 1. Take 2 wormholes side by side 2. Take one and accelerate it close to speed of light, keep the other one where it is 3. Time dilation – clocks tick slower in moving mouth 4. If you enter the stationary wormhole, you can come out of the moving one at an earlier time… There may be a problem… • Strong force of gravity acting on us • Need to keep wormhole open for long enough • Can’t visit time periods before time machine was created OK OK, spoil our fun. But can we at least move from different point in space? Can we teleport? Teleportation • Uncertainty principle prevents it • We can’t simultaneously know the position and momentum of a particle! • Same for energy and time Can use quantum entanglement Take 2 subatomic particles Bring them together to get quantum states interlinked Separate them, one determines the other Problems… • Human body has at least 1028 atoms • Would take 1013 years (that’s 4000 times the age of the universe!) • Need receiver So far have scientists have teleported photons Can we all be time lords? 3 easy steps to becoming a time lord… 1. Work out how to travel time 2. Build a time machine 3. Make a sonic screwdriver Oh boy… T.A.R.D.I.S. Time And Relative Dimensions In Space How does that work The tardis is bigger on inside than out… How? Use general relativity We can bend space and time to get a bubble bigger on side than out Can’t use normal particles Need exotic matter Particles that violate classical physics Have negative pressure, some even have a negative mass!!! Chameleon Circuit • Need to blend in with surroundings • Different to cloaking device • University of Tokyo has developed optical camouflage • System of cameras and projectors • Camera technology is improving Electrostriction • Change shape and texture • Use electrostriction - non-conductors can change shape under an electric field - can expand & contract by up to a factor of 5 • Calculate electric field to transform shape into clock etc Can we all be time lords? 3 easy steps to becoming a time lord… 1. Work out how to travel time 2. Build a time machine 3. Make a sonic screwdriver Very cool… Sonic Screwdriver Can do endless things… A great Father’s day present Works using sound waves, but what is sound? Sound waves Sound is vibration Sound waves are longitudinal Sonic Screwdriver • Use sound waves to undo screws • We can hear 20-20,000 Hz, above is ultrasound • Ultrasonic hard drives • Ultrasound is very harmful! > 159dB = warms skin > 180dB = lethal Sonic Screwdriver Need to make a narrow beam Have high frequency sound, so that beam is less spread out Speed = frequency * wavelength Use principal of beats… Beats • Take 2 waves of same amplitude • BUT slightly different frequencies • Variation in amplitude = beats • Beat frequency fbeat = fa - fb • Produce audible sound Be careful out there…