This is a quick-and-dirty FAQ (hence "qdFAQ") pulled together by your FAQservant (whose address you can easily work out, given that you know his name to be Richard) from messages posted to and from other Web sites run by interested parties. Nobody has yet had the time to create a real FAQ, so this will have to do for a while.

Copyright: reproduction of these pages for the usual FAQ purposes is permitted without fee, on condition that the names of the original authors are left in.

Current version: 1.5.4.
New since 1.5: lunar beanstalk article, some more extrasolar planet URLs, another article about tidelocked planets, and a URL for the FAQ of
New since 1.4: Dinosaur civilisations.


The Drake Equation

... is a framework for estimating the number of technological civilisations that may exist in our galaxy. It is explained here by the SETI Institute.

The Fermi Paradox

... is what you get when you believe (as many of us do) that the answer to the Drake equation is significantly above 0.0, and (as most of us do) that it is possible -- if difficult -- to travel from one star to another in the galaxy at speeds of, say, a thousandth of the speed of light. Namely, you get that extra-solar aliens should not only exist, but should have visited this solar system, or be visiting it now. But we don't exactly see evidence of this.

Bill Vaughan lists some explanations
Erik Max Francis argues that we simply don't know

Richard Harter also has an essay on the subject, which I recommend, here
Geoffrey Landis explains his "percolation theory" here
and Erik Max Francis collects some more links on the general subject here.

Stellar Physics

Erik Max Francis has a couple of introductory essays on stellar evolution and when the Sun will die; there may be more advanced presentations in the FAQ for sci.astro, though I haven't looked.

Planets, here and elsewhere

If you're looking for sizes and speeds and so on of planets in this solar system, NASA offers a set of brief
fact sheets. There's a more descriptive site called "Nine Planets" here with a wealth of info and links. Regarding planets orbiting other stars, Geoffrey Landis points me to the Exoplanets and Other worlds, distant suns sites. See also The Extrasolar Planets Encyclopaedia.

Destroying the Earth

It is often asked what it would take to shatter the Earth into little pieces. Erik Max Francis gives a rough answer. A less drastic measure would be to sterilise it by heating the outside. Brian Davis does the arithmetic, but I think he should have calculated what it would take to boil the oceans, which is a few thousand times more by my BotEC. Occasionally it is asked what would happen if you shot a fast-moving projectile at the Earth; I've written something up.

Dinosaur Civilisations

or, what evidence would we find if there had been a technological civilisation on Earth 65 million years ago?

This section is still under development. A related question that is sometimes asked is, how might aliens arriving 65 MY in the future tell that we had had a technological civilisation?

P.D. Tillman gives an archaeological view of the first question.

Types of Stardrive

i.e. FTL drives found in science fiction

Erik Max Francis wrote a short list
Geoffrey Landis gives a few more exotic ones
Erik Max Francis mentions a few pitfalls for authors
Winchell "Nyrath" Chung has a long list of size 21K or so (written by Geoffrey Landis).
Bruce Bowden has a longish article about relativistic (slower than light) interstellar travel. It's 60Kb plus some medium-sized GIFs that present his algebra.

For the pitfalls of faster-than-light travel, see Jason W. Hinson's Relativity FAQ, and the FAQ for sci.physics.relativity.

But can't we just use tachyons? There's an article within the sci.physics FAQ that explains better than I can.

What about the very long rigid rod?

Getting into Orbit

Erik Max Francis has an essay on the rocket equation (not recommended for the math-o-phobic). You can find an interesting, albeit dated (December 1996), article about gas gun launchers here.

There was once a list of existing and near-future Orbital and Planetary Launch Services (with payload, price, and reliability numbers; dated October 1995). Space Future is a good site if you're interested in current R&D efforts.

Dani Eder's list of Canonical Space Transportation Methods is pretty old (1994) but very comprehensive. File size is about 109k. Or I keep a ZIP-compressed version of it here, only 41k.

Orbital Elevators

I couldn't find a message that described the basic concept, so I've written it up here if you need the background.

Errors in Science Fiction

I've summarised some of them here since I couldn't find any good messages about them. Blaine Gordon Manyluk has written a longer list (file size about 16k); note that his figure of 10% efficiency for lasers is obsolete, with semiconductor lasers reaching as high as 60% and other types perhaps as much as 20%. The Bad Astronomer points out many astronomical errors in the news media and in some "sci-fi" films.

Weapons and Tactics

Questions about how wars will be fought in space are frequently asked, but there are no widely agreed upon answers. People have many differing views about how to resolve the tension between speed, stealth, protection, and offensive power. Join the fun.

Weather on Tide-Locked Planets

Every so often it is asked what the weather, or climate ("climate is what you expect; weather is what you get"), would be like on a generally Earth-like planet that always presented the same face to its sun.

Jason Goodman takes a stab at it.

Phil Plait notes that Venus has rather little difference in temperature between day and night sides; but its atmosphere is much denser than Earth's, which probably makes heat transfer faster.

Brian Davis reports the results of some computer modelling.

Other FAQs and links

The FAQ for rec.arts.sf.written will be of interest to some; try here? The FAQ for is here.

The FAQ for sci.astro is on the World Wide Web at

The FAQ for sci.physics.relativity is here and the one for sci.physics is here.

There are some good FAQs on evolution at, especially this Introduction to Evolutionary Biology, which is long, but solid.

Is there a FAQ for Edward Bornstein points me to this, for which I thank him. The Nuclear Weapons FAQ is here.

This isn't exactly a FAQ, more of a directory, but it could be useful.

UniSci often has interesting accounts of cutting-edge science that is being done today.