# Faster-Than-Light Paradoxes in Special Relativity

## Presentation on theme: "Faster-Than-Light Paradoxes in Special Relativity"— Presentation transcript:

Brice N. Cassenti

Principle of Special Relativity Paradoxes in Special Relativity Relativistic Rockets Conclusions

Principle of Special Relativity
Postulates Lorentz Transformation Lorentz Contraction Time Dilation

Postulates of the Special Theory of Relativity
The laws of physics are the same in all inertial coordinate systems The speed of light is the same in all inertial coordinate systems

Inertial Reference Systems

Lorentz Transformation Derivation
Assume transformation is linear Assume speed of light is the same in each frame

Relative Motion (x,ct) v (x’,ct’)

Lorentz Transformation
Inverse transformation Use of hyperbolic functions

Coordinate Systems ct ct x x

Lorentz Contraction Length is measured in a frame by noting end point locations at a given time. When observing a rod in a moving frame, with its length in the direction of motion the frame, the length is shorter by: The result holds in either frame.

Time Dilation Time is measured in a frame by watching a clock fixed in the moving frame. When observing a clock in a moving frame the clock runs slower by: The result holds in either frame.

Pole Vaulter Twin Paradox Faster-than-Light Travel Instant Messaging

Pole Vaulter & Barn 15 ft 10 ft

Pole Vaulter & Barn v 7.5 ft 10 ft

Pole Vaulter & Barn v 15 ft 5 ft

Front door opens

Front door opens Forward end of pole enters barn

Front door opens Forward end of pole enters barn Back end of pole enters barn

Front door opens Forward end of pole enters barn Back end of pole enters barn Front door closes

Front door opens Forward end of pole enters barn Back end of pole enters barn Front door closes Pole entirely inside barn

Front door opens Forward end of pole enters barn Back end of pole enters barn Front door closes Pole entirely inside barn Back door opens

Front door opens Forward end of pole enters barn Back end of pole enters barn Front door closes Pole entirely inside barn Back door opens Front end of pole leaves barn

Front door opens Forward end of pole enters barn Back end of pole enters barn Front door closes Pole entirely inside barn Back door opens Front end of pole leaves barn Back end of pole leaves barn

Front door opens Forward end of pole enters barn Back end of pole enters barn Front door closes Pole entirely inside barn Back door opens Front end of pole leaves barn Back end of pole leaves barn

Pole Vaulter Paradox Pole Vaulter View
Front doors opens

Pole Vaulter Paradox Pole Vaulter View
Front doors opens Forward end of pole enters barn

Pole Vaulter Paradox Pole Vaulter View
Front doors opens Forward end of pole enters barn Back door opens

Pole Vaulter Paradox Pole Vaulter View
Front doors opens Forward end of pole enters barn Back door opens Front end of pole leaves barn

Pole Vaulter Paradox Pole Vaulter View
Front doors opens Forward end of pole enters barn Back door opens Front end of pole leaves barn Both ends of pole never in barn simultaneously

Pole Vaulter Paradox Pole Vaulter View
Front doors opens Forward end of pole enters barn Back door opens Front end of pole leaves barn Both ends of pole never in barn simultaneously Back end of pole enters barn

Pole Vaulter Paradox Pole Vaulter View
Front doors opens Forward end of pole enters barn Back door opens Front end of pole leaves barn Both ends of pole never in barn simultaneously Back end of pole enters barn Front door closes

Pole Vaulter Paradox Pole Vaulter View
Front doors opens Forward end of pole enters barn Back door opens Front end of pole leaves barn Both ends of pole never in barn simultaneously Back end of pole enters barn Front door closes Back end of pole leaves barn

Pole Vaulter Paradox Pole Vaulter View
Front doors opens Forward end of pole enters barn Back door opens Front end of pole leaves barn Both ends of pole never in barn simultaneously Back end of pole enters barn Front door closes Back end of pole leaves barn

Use Lorentz transformation In barn view, time interval from back door closing to front door opening is less than time light needs to cover distance In pole vaulter view, time from front of pole to leave and back to enter is less than time light needs to cover distance along pole Lorentz transformation correctly predicts both views correctly from both the barn and pole vaulter frames

Faster-than-light signals would allow contradictions in observations

Twin Paradox One of two identical twins leaves at a speed such that each twin sees the other clock running at half the rate of theirs The traveling twin reverses speed and returns Does each think the other has aged half as much?

In order to set out turn around and stop at the return the traveling twin accelerates. The traveling twin feels the acceleration. Hence, the traveling twin is not in an inertial frame. The stationary twin ages twice as much as the traveling twin.

Twin Paradox - Resolution Constant Acceleration

Twin Paradox - Resolution Infinite Acceleration

Accelerating reference frames need to be treated with a more General Theory of Relativity

Faster-Than-Light Travel

Faster-Than-Light Travel

Faster-Than-Light Travel

Faster-Than-Light Travel

Faster-Than-Light Travel

Faster-Than-Light Travel

Faster-Than-Light Travel

Faster-than-Light Travel – Conclusion
Faster-than-Light motion reverses travel through time – a time machine

The Mathematics of Faster-than-Light Travel
Recall Setting Then If Then Let And Or

Instant Messaging

Instant Messaging

Instant Messaging

Instant Messaging

Instant Messaging

Instant Messaging

Instant Messaging

Instant Messaging

Instant Messaging – Conclusion
Instant communications is a nonlinear process (exponential) and does not satisfy the postulates of Quantum Mechanics. The number of messages must collapse to a single message. Faster-than-light travel may result in the collapse of the wave function

Relativistic Rockets Relativistic Energy Constant Acceleration Rocket
Photon Rocket

Relativistic Energy

Relativistic Energy

Relativistic Energy

Relativistic Energy

Relativistic Energy

Relativistic Energy

& constant in all reference frames
Relativistic Energy There is a relativistic rest mass energy For is imaginary Particles are tachyons Tachyons have never been observed & constant in all reference frames ,

Relativistic Accelerating Rocket

Relativistic Accelerating Rocket

Relativistic Accelerating Rocket

Relativistic Accelerating Rocket
In rocket frame

Relativistic Accelerating Rocket
In rocket frame

Relativistic Accelerating Rocket
In rocket frame

Relativistic Accelerating Rocket
In rocket frame

Constant Acceleration Rocket

Constant Acceleration Results
In the reference frame of the rocket when sinhq>1, dx/dt>c. Accelerating at one gravity a crew could circumnavigate the universe within their working lifetime.

Photon Rocket

Photon Rocket

Photon Rocket

Photon Rocket

Photon Rocket

Photon Rocket

Photon Rocket Results Velocity parameter replaces velocity in the ‘rocket equation’

Photon Rocket Results Velocity parameter replaces velocity in the ‘rocket equation’ Circumnavigating the universe at one gravity requires an enormous mass ratio

Photon Rocket Results Velocity parameter replaces velocity in the ‘rocket equation’ Circumnavigating the universe at one gravity requires an enormous mass ratio But the mass required is not larger than the mass of the universe

Conclusions Faster-than-light paradoxes in the Special Theory of Relativity are: More than curiosities They can provide a better understanding of space and time They can add insight into other paradoxes Collapse of the wave function They can lead to new physical theories And may allow unlimited access to the universe.

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