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URL: http://sciastro.astronomy.net/
Posting-frequency: semi-monthly (Wednesday)
Archive-name: astronomy/faq/part0
Subject: Introduction
sci.astro is a newsgroup devoted to the discussion of the science of
astronomy. As such its content ranges from the Earth to the farthest
reaches of the Universe.
However, certain questions tend to appear fairly regularly. This
document attempts to summarize answers to these questions.
This document is posted on the first and third Wednesdays of each
month to the newsgroups sci.astro and sci.astro.seti. It is available
via anonymous ftp from
<URL:ftp://rtfm.mit.edu/pub/usenet/news.answers/astronomy/faq/>, and
it is on the World Wide Web at
<URL:http://sciastro.astronomy.net/sci.astro.html> and
<URL:http://www.faqs.org/faqs/astronomy/faq/>. A partial list of
worldwide mirrors (both ftp and Web) is maintained at
<URL:http://sciastro.astronomy.net/mirrors.html>. (As a general note,
many other FAQs are also available from
<URL:ftp://rtfm.mit.edu/pub/usenet/news.answers/>.)
Questions/comments/flames should be directed to the FAQ maintainer,
Joseph Lazio (jlazio@patriot.net).
Subject: Copyright
This document, as a collection, is Copyright 1995--2003 by T. Joseph
W. Lazio (jlazio@patriot.net). The individual articles are copyright
by the individual authors listed. All rights are reserved.
Permission to use, copy and distribute this unmodified document by any
means and for any purpose EXCEPT PROFIT PURPOSES is hereby granted,
provided that both the above Copyright notice and this permission
notice appear in all copies of the FAQ itself. Reproducing this FAQ
by any means, included, but not limited to, printing, copying existing
prints, publishing by electronic or other means, implies full
agreement to the above non-profit-use clause, unless upon prior
written permission of the authors.
This FAQ is provided by the authors "as is," with all its faults. Any
express or implied warranties, including, but not limited to, any
implied warranties of merchantability, accuracy, or fitness for any
particular purpose, are disclaimed. If you use the information in
this document, in any way, you do so at your own risk.
Subject: Table of Contents
Dates in brackets are last edit.
A.00 The Internet and other information sources
A.01 What are the sci.astro* newsgroups about? [1999-11-03]
A.02 How do I subscribe to sci.astro*? [1998-02-28]
A.03 What are the guidelines for posting on astronomy (sci.astro*)
newsgroups? [1995-07-10]
A.04 What should I do if I see an article that doesn't follow
these guidelines? (What about cranks?) [1997-02-04]
A.05 Can I get help on my homework from the Net? [1995-07-26]
A.06 What are good Net sites for astronomy info and
images? [2003-04-27]
A.07 How can I find contact addresses for
astronomers/observatories? [1996-12-04]
A.08 Which observatories offer tours or public viewing?
[1995-09-17]
A.09 Is there a list of astro jokes? [1999-12-15]
A.10 What are good books on astronomy (especially for beginners)?
[1995-06-27]
A.11 Are there other sources of information? [1996-01-24]
A.12 How can I find an astronomy club? [1996-01-24]
A.13 Where can I find out about public lectures or star parties?
[1995-09-17]
B.00 General
B.01 What good is astronomy anyway? [1997-08-06]
B.02 What are the largest telescopes? [2001-02-04]
B.03 What new telescopes/instruments are being built? [2000-01-01]
B.04 What is the resolution of a telescope? [1995-08-23]
B.05 What's the difference between astronomy and astrology?
[1995-08-23]
B.06 Is there scientific evidence for/against astrology?
[1995-08-23]
B.07 What about God and the creation? [1995-08-27]
B.08 What kind of telescope should I buy? [2001-01-17]
B.09 What are the possessive adjectives for the planets?
[1995-12-05]
B.10 Are the planets associated with days of the week?
[2000-11-12]
B.11 Why does the Moon look so big when it's near the
horizon? [1997-01-21]
B.12 Is it O.K. to look at the Sun or solar eclipses using
exposed film? CDs? [1996-11-20]
B.13 Can stars be seen in the daytime from the bottom of a tall
chimney, a deep well, or deep mine shaft? [1996-06-14]
B.14 Why do eggs balance on the equinox? [1996-06-14]
B.15 Is the Earth's sky blue because its atmosphere is nitrogen
and oxygen? Or could other planets also have blue
skies? [1998-02-06]
B.16 What are the Lagrange (L) points? [2003-10-18]
B.17 Are humans affected psychologically and/or physically by
lunar cycles? [2000-06-03]
B.18 How do I become an astronomer? What school should I
attend? [1996-07-03]
B.19 What was the Star of Bethlehem? [2002-05-04]
B.20 Is it possible to see the Moon landing sites? [2002-05-07]
C.00 Time, Calendars, and Terrestrial Phenomena
C.01 When is 02/01/04? or is there a standard way of writing
dates? [2001-12-14]
C.02 What are all those different kinds of time? [2002-05-07]
C.03 How do I compute astronomical phenomena for my location?
[2002-05-04]
C.04 What's a Julian date? modified Julian date? [1998-05-06]
C.05 Was 2000 a leap year? [2000-03-17]
C.06 When will the new millennium start? [2001-01-01]
C.07 Easter:
07.1 When is Easter? [2001-08-14]
07.2 Can I calculate the date of Easter? [1995-12-11]
C.08 What is a "blue moon?" [2001-10-02]
C.09 What is the Green Flash (or Green Ray)? [1999-01-01]
C.10 Why isn't the earliest Sunrise (and latest Sunset) on the
longest day of the year? [2002-01-30]
C.11 How do I calculate the phase of the moon? [2001-08-14]
C.12 What is the time delivered by a GPS receiver? [2002-05-07]
C.13 Why are there two tides a day and not just one? [1999-12-15]
D.00 Astrophysics
D.01 Do neutrinos have rest mass? What if they do? [2002-05-04]
D.02 Have physical constants changed with time? [1997-02-04]
D.03 What is gravity? [1998-11-04]
D.04 Does gravity travel at the speed of light? [1998-05-06]
D.05 What are gravitational waves? [1997-06-10]
D.06 Can gravitational waves be detected? [2000-08-31]
D.07 Do gravitational waves travel at the speed of light?
[1996-07-03]
D.08 Why can't light escape from a black hole? [1995-10-05]
D.09 How can gravity escape from a black hole? [1996-01-24]
D.10 What are tachyons? Are they real? [1995-10-02]
D.11 What are magnetic monopoles? Are they real? [1996-07-03]
D.12 What is the temperature in space? [1998-04-14]
D.13 Saturn's rings, proto-planetary disks, accretion disks---Why
are disks so common? ]99-07-18]
E.00 Sun, Moon, and Planets
E.01 How did the solar system form? [2000-07-15]
E.02 Has anyone attempted to discern details of the star that went
supernova and formed our local group of stars? [2002-05-04]
E.03 What is the "Solar Neutrino Problem"? [1997-07-01]
E.04 Could the Sun be part of a binary (multiple) star system?
[1995-08-27]
E.05 When will the Sun die? How? [1995-08-23]
E.06 What happens to the planets when the Sun dies? [2000-03-17]
E.07 Could the Sun explode? [1995-07-07]
E.08 How are solar system objects and features named? [1995-11-29]
E.09 Where can I find pictures and planetary data? (ref)
E.10 Could Jupiter become a star? [1995-07-07]
E.11 Is Pluto a planet? Is Ceres? Is Titan? [1995-08-18]
E.12 Additional planets:
12.1 What about a planet (Planet X) outside Pluto's orbit?
[2000-05-21]
12.2 What about a planet inside Mercury's orbit? [1996-11-20]
E.13 Won't there be catastrophes when the planets align in the
year 2000? [2000-07-15]
E.14 Earth-Moon system:
14.1 Why doesn't the Moon rotate? [1997-10-01]
14.2 Why does the Moon always show the same face to the
Earth? [1997-10-01]
14.3 Is the Moon moving away from the Earth? (and why is Phobos
moving closer to Mars?) [1997-06-04]
14.4 What was the origin of the Moon? [1998-11-04]
E.15 What's the difference between a solar and lunar eclipse?
Where can I find more information about eclipses?
[2001-01-17]
E.16 What's the Oort Cloud and Kuiper Belt? [1998-02-28]
E.17 Asteroid Impacts
17.1 What would be the effects of an asteroid impact on the
Earth? [1998-04-14]
17.2 What can we do about avoiding impacts? [1998-04-14]
E.18 What's the difference between meteoroids, meteors, and
meteorites? [1998-04-14]
E.19 How do we know that meteorites are from the Mars? (or the
Moon?) [2002-05-04]
F.00 Extraterrestrial Life
F.01 What is life? [1997-09-03]
F.02 Life in the Solar System
02.1 Is there life on Mars? [1996-09-03]
02.2 Is there life in Jupiter (or Saturn)? [1996-09-03]
02.3 Is there life on Jupiter's moon, Europa? [1996-09-03]
02.4 Life on Titan? [1997-08-05]
F.03 What is the Drake equation? [1995-10-04]
F.04 What is the Fermi paradox? [1995-12-28]
F.05 Could we detect extraterrestrial life? [1999-09-15]
F.06 How far away could we detect radio transmissions?
[1996-09-03]
F.07 What's a Dyson sphere? [1997-06-04]
F.08 What is happening with SETI now? [1998-01-31]
F.09 Why search for extraterrestrial intelligence using radio?
Why not <fill in the blank> method? [2000-01-01]
F.10 Why do we assume that other beings must be based on carbon?
Why couldn't organisms be based on other substances?
[2001-03-20]
F.11 Could life occur on an interstellar planet? [2003-04-27]
G.00 Stars
G.01 What are all those different kinds of stars?
01.1 General overview and main sequence stars [1996-01-02]
01.2 White dwarfs [2003-04-27]
01.3 Neutron stars [2003-04-27]
01.4 Black holes [2003-04-27]
G.02 Are there any green stars? [1995-12-28]
G.03 What are the biggest and smallest stars? [1998-06-03]
G.04 What fraction of stars are in multiple systems? [1995-06-27]
G.05 Where can I get stellar data (especially distances)?
[2003-05-08]
G.06 Which nearby stars might become supernovae? [2000-02-20]
G.07 What will happen on Earth if a nearby star
explodes? [1998-02-11]
G.08 How are stars named? Can I name/buy one? [1995-12-28]
G.09 Do other stars have planets?
G.10 What happens to the planets when a planetary nebula is
formed? Do they get flung out of the solar system? [2002-05-04]
G.11 How far away is the farthest star? [1999-01-01]
G.12 Do star maps (or galaxy maps) correct for the motions of the
stars? [2003-10-18]
H.00 Galaxies, Clusters, and QSO's
H.01 How many stars, galaxies, clusters, QSO's etc. in the
Universe? [1997-08-06]
H.02 Is there dark matter in galaxies? [1997-12-02]
H.03 What is the Hubble constant? What is the best value?
[1995-07-19]
H.04 How are galaxy distances measured? [1995-06-29]
H.05 When people speak of galaxies X billion light years
away, does this mean they are that far away now or were that
far away when the light left them? [1997-08-06]
H.06 What are QSO's ("quasars")? [1995-06-29]
H.07 Are the QSO's really at their redshift distances?
[2003-02-18]
H.08 What about apparent faster-than-light motions? [1995-06-29]
H.09 What's the Local Group? [1999-05-19]
I.00 Cosmology and the Universe [1998-02-28]
I.01 What do we know about the properties of the Universe?
I.02 Why do astronomers favor the Big Bang model of the Universe?
I.03 Where is the center of the Universe?
I.04 What do people mean by an "open," "flat," or "closed"
Universe?
I.05 If the Universe is expanding, what about me? or the Earth? or
the Solar System?
I.06 What is inflation?
I.07 How can the Big Bang (or inflation) be right? Doesn't it
violate the idea that nothing can move faster than light?
(Also, can objects expand away from us faster than the speed
of light?)
I.08 If the Universe is only 10 billion years old, how can we see
objects that are now 30 billion light years away? Why isn't
the most distant object we can see only 5 billion light years
away?
I.09 How can the oldest stars in the Universe be older than the
Universe?
I.10 What is the Universe expanding into?
I.11 Are galaxies really moving away from us or is space-time just
expanding?
I.12 How can the Universe be infinite if it was all concentrated
into a point at the Big Bang?
I.13 Why haven't the cosmic microwave background photons outrun the
galaxies in the Big Bang?
I.14 Can the cosmic microwave background be redshifted starlight?
I.15 Why is the sky dark at night? (Olbers' paradox) [2001-10-02]
I.16 What about objects with discordant redshifts?
I.17 Since energy is conserved, where does the energy of
redshifted photons go? [1998-12-03]
I.18 There are different ways to measure distances in cosmology?
[1999-07-06]
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with stars, then every direction you looked would eventually end on
the surface of a star, and the whole sky would be as bright as the
surface of the Sun.
Why would anyone assume this? Certainly, we have directions where we look that are dark because something that does not emit light (is not a star) is between us and the light. A close example is in our own solar system. When we look at the Sun (a star) during a solar eclipse the Moon blocks the light. When we look at the inner planets of our solar system (Mercury and Venus) as they pass between us and the Sun, do we not get the same effect, i.e. in the direction of the planet we see no light from the Sun? Those planets simply look like dark spots on the Sun.
Olbers' paradox seems to assume that only stars exist in the universe, but what about the planets? Aren't there more planets than stars, thus more obstructions to light than sources of light?
What may be more interesting is why can we see certain stars seemingly continuously. Are there no planets or other obstructions between them and us? Or is the twinkle in stars just caused by the movement of obstructions across the path of light between the stars and us? I was always told the twinkle defines a star while the steady light reflected by our planets defines a planet. Is that because the planets of our solar system don't have the obstructions between Earth and them to cause a twinkle effect?
9-14-2024 KP