這是一篇討論各種科幻領域裡面的超光速航行的faq，自從暑假抓回來之後
一直沒有時間看完，把他post在這裡希望跟大家分享，哎.....我下次抓faq回來一定
要先看完。發信地點是在美國普度大學的物理實驗室。
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Relativity and FTL Travel
by Jason W. Hinson ([email protected])
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An Introduction to the FAQ
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Copyright (C) 1995, Jason W. Hinson. This document, including all
of its parts, is not in the public domain. Permission to
distribute this document in its entirety (unedited and including
this copyright notice) is granted, provided no fees are charged for
the distribution beyond charges for downloading and/or connection
time from a commercial information service. Permission to
distribute a partial version of this document containing only this
introduction along with parts I and IV is also granted under the
same restrictions. Publication of any part of this document in a
magazine or journal (in any media format) must be approved by the
author.
Star Trek (R), Star Trek: The Next Generation (R) and Star Trek:
Deep Space Nine (R) are trademarks of Paramount Pictures registered
in the United States Patent and Trademark Office. Star Trek:
Voyager is a trademark of Paramount Pictures.
Edition 4.0b: (Last Modified: April 25, 1995)
This is edition 4.0b of this FAQ. The FAQ is now broken into 5
separate posts (this introduction and 4 separate parts of the FAQ
itself). Two parts of the FAQ are completely new--one which looks
further into the concepts of special relativity and one which explores
general relativity. The information in these two parts is not
directly used in the arguments concerning FTL travel (which are
contained in PART IV), and they are provided simply as information for
interested readers.
The "b" in the edition number indicates that it is a "beta"
edition. I call it this because I am sure it contains mistakes here
and there I have yet to catch, and this version will be a "test
version" until I am reasonably sure all the mistakes are taken care
of. Therefore, as always, if you see any mistakes or if you think
that any changes should be made, please let me know.
Access from the World Wide Web:
At this time, all parts of this FAQ are available in text format
from links at this URL:
http://bohr.physics.purdue.edu/~hinson/ftl/FTL_StartingPoint.html
At some point I want to convert the document to HTML format;
however, the time scale for completing this step is unknown right now.
What is it about, and who should read it:
The primary purpose of this FAQ is to discuss (in straight-
forward, simple terms) the relationship between relativity and faster
than light (FTL) travel. PART I introduces the information about
special relativity which one needs to understand the discussion of FTL
travel. One of its sections involves an introduction to space-time
diagrams, which are used to make some significant points in the FTL
travel discussion. Therefore, if you are not familiar with these
diagrams, then this will be a very important section for you to read.
Parts II and III are what I call "optional reading" parts. If
you do not want to read them, you can still understand the FTL travel
discussion. PART II gives more information about special relativity
and explains two "solvable paradoxes" which are associated with the
theory, while PART III introduces and explores some of the major
concepts in general relativity, and does so at considerable length.
PART IV is the part which discusses the question of FTL travel.
There are two basic problems which are discussed, and while most ideas
for FTL travel in science fiction address the first problem (the light
speed barrier), many simply ignore the second (producing unsolvable
paradoxes). PART IV also discusses various conceptual forms of FTL
travel (each of which get around the "first problem"), and it
introduces special provisions for getting around the "second
problem".
Finally, because this FAQ is meant for the rec.arts.startrek.tech
newsgroup, I will apply the FTL discussion to explain how warp (as it
is depicted in Trek) can allow FTL travel while getting around both of
the problems mentioned above. As far as I can tell, it presents the
best way of explaining everything the series has shown us.
I should also note that various diagrams are used throughout this
FAQ, and it may be helpful for you to make a hard copy of the parts
you are reading so that you can view the diagrams easily as you read
various sections of the FAQ.
I hope you can learn a little something from reading this, or
at least strengthen your understanding of that which you already know.
Your comments and criticisms are welcome, especially if they indicate
improvements that I can make for future posts. If any or all parts of
this post do not show up at your site, or if any or all are cut short,
let me know and I can e-mail you the parts you want.
Part Sizes:
PART I: 845 lines ~13 pages
PART II: 895 lines ~14 pages
PART III: 1867 lines ~29 pages (yes, an extensive discussion)
PART IV: 1313 lines ~21 pages
Contents of the FAQ:
PART I: Special Relativity
1. An Introduction to Special Relativity
1.1 Reasoning for its Existence
1.2 Time Dilation and Length Contraction Effects
1.3 Introducing Gamma
1.4 Energy and Momentum Considerations
1.5 Experimental Support for the Theory
2. Space-Time Diagrams
2.1 What are Space-Time Diagrams?
2.2 Basic Information About the Diagrams we will Construct
2.3 Constructing One for a "Stationary" Observer
2.4 Constructing One for a "Moving" Observer
2.5 Interchanging "Stationary" and "Moving"
2.6 "Future", "Past", and the Light Cone
PART II: More on Special Relativity
3. Completing the Space-Time Diagram Discussion
3.1 Comparing Time for O and O'
3.2 Comparing Space for O and O'
3.3 Once Again: The Light Cone
4. Paradoxes and Solutions
4.1 The "Twin Paradox"
4.1.1 Viewing it with a Space-Time Diagram
4.1.2 Explaining the "First Part"
4.1.3 Explaining the "Second Part"
4.1.4 Some Additional Notes
4.2 The "Car and Barn Paradox"
4.2.1 Viewing it with a Space-Time Diagram
4.2.2 The explanation
Part III: A Bit About General Relativity
5. Introduction to General Relativity
5.1 Reasoning for its Existence
5.2 The "New Inertial Frame"
5.3 Manifolds, Geodesics, Curvature, and Local Flatness
5.4 The Invariant Interval
5.5 A Bit About Tensors
5.6 The Metric Tensor and the Stress-Energy Tensor
5.7 Applying these Concepts to Gravity
5.7.1 The Basic Idea
5.7.2 Some Notes on the Physics and the Math
5.7.3 First Example: Back to SR
5.7.4 Second Example: Stars and Black Holes
5.8 Experimental Support for GR
PART IV: Faster Than Light Travel--Concepts and Their "Problems"
6. Introduction to the FTL Discussion
6.1 A Few Notes On The Meaning of FTL Travel
7. The First Problem: The Light Speed Barrier
7.1 Effects as One Approaches the Speed of Light
8. The Second Problem: FTL, Causality, and Unsolvable Paradoxes
8.1 What is Meant Here by Causality and Unsolvable Paradoxes
8.2 How FTL Travel Implies Violation of Causality
8.3 How We Get Unsolvable paradoxes.
9. FTL Concepts with these Problems in Mind
9.1 Tachyons (Without Special Provisions)
9.2 Using a Special Field/Space/etc. (W/o Special Provisions)
9.3 "Folding" Space (Without Special Provisions)
9.4 Space-Time Manipulation (Without Special Provisions)
9.5 Special Provisions
9.5.1 Consistency Protection
9.5.2 "Producing" Restricted Space-Time Areas
9.5.3 A Special Frame of Reference for the purpose of FTL Travel
10. Some Comments on FTL Travel in Star Trek
10.1 Which Provision is Best for Explaining Warp Travel
10.2 Subspace as a Special Frame of Reference
10.3 The "Picture" this Gives Us of Warp Travel
10.4 Some Notes on Non-Warp FTL Travel and Time Travel in Trek
10.5 To sum up...
11. Conclusion.