FACT OR FANTASY?

bbc.co.uk/doctorwho

• 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

Who Is Doctor Who?

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 screwdriverVery 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 entanglementTake 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 screwdriverOh boy…

Time And Relative Dimensions In Space

T.A.R.D.I.S.

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 screwdriverVery 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…