TAN: _High Wizardry_ for physicists
Kate Nepveu
So I just finished Duane's _High Wizardry_, which I hugely enjoyed.
The scene where the upgraded version of the turtles is released is
marvelous, in particular. However, part of the ending is bugging me,
namely the bit with Olber's Paradox. Spoilers, I guess.
Okay. Dairine's [1] fighting the Lone Power and needs a lot of light.
To get it, she makes a spell which makes the universe stop expanding.
(NB: there's no statement that it's now contracting, just that it's
stopped expanding. Later, she mentions cancelling the spell, which
leads me to believe that it was a temporary holding of the expansion,
not a reversal of it.) Within minutes, it becomes really bright from
the galaxies, etc. which are no longer moving away.
Now, I know next-to-nothing about the math involved here. And
frankly, I don't need or want to know the math. But that doesn't
sound right to me--it seems like it happens far too fast. Can any of
our resident physics types tell me if this is even remotely plausibe?
[1] Just how does one pronounce this, anyway?
Kate
A rumor without a leg to stand on will get around some other way.
--John Tudor
J.Thiele
Kate Nepveu <kne...@lynx.neu.edu.CUT-HERE> wrote in article
<33e35a26...@nntp.neu.edu>...
| So I just finished Duane's _High Wizardry_, which I hugely enjoyed.
| The scene where the upgraded version of the turtles is released is
| marvelous, in particular. However, part of the ending is bugging me,
| namely the bit with Olber's Paradox. Spoilers, I guess.
|
|
|
| Okay. Dairine's [1] fighting the Lone Power and needs a lot of light.
| To get it, she makes a spell which makes the universe stop expanding.
| (NB: there's no statement that it's now contracting, just that it's
| stopped expanding. Later, she mentions cancelling the spell, which
| leads me to believe that it was a temporary holding of the expansion,
| not a reversal of it.) Within minutes, it becomes really bright from
| the galaxies, etc. which are no longer moving away.
|
| Now, I know next-to-nothing about the math involved here. And
| frankly, I don't need or want to know the math. But that doesn't
| sound right to me--it seems like it happens far too fast. Can any of
| our resident physics types tell me if this is even remotely plausibe?
|
No chance!
I am going to ignore the fact, that your not going to get a whole lot of
light from stopping the expansion of the universe.
The nearest galaxy is approx. 8 lightyears (IIRC) away from us, meaning
that its light takes _8 years_ to get here. The galaxies at the outer rim
of the universe are just a little bit further out, I'm not sure of the
distance right now (and to lazy to check, the truth be told), but were
talking many _millions_ of years - at least.
JTT
jorgenson
Kate Nepveu wrote:
>
> So I just finished Duane's _High Wizardry_, which I hugely enjoyed.
> The scene where the upgraded version of the turtles is released is
> marvelous, in particular. However, part of the ending is bugging me,
> namely the bit with Olber's Paradox. Spoilers, I guess.
>
> Okay. Dairine's [1] fighting the Lone Power and needs a lot of light.
> To get it, she makes a spell which makes the universe stop expanding.
> (NB: there's no statement that it's now contracting, just that it's
> stopped expanding. Later, she mentions cancelling the spell, which
> leads me to believe that it was a temporary holding of the expansion,
> not a reversal of it.) Within minutes, it becomes really bright from
> the galaxies, etc. which are no longer moving away.
>
> Now, I know next-to-nothing about the math involved here. And
> frankly, I don't need or want to know the math. But that doesn't
> sound right to me--it seems like it happens far too fast. Can any of
> our resident physics types tell me if this is even remotely plausibe?
>
>
> Kate
>
There's no way a ton of light would just start appearing. The distances
between galaxies are way to large. Our galaxy is about 100,000
light-years across. It would take a lot longer than a few minutes for
light to appear in vast quantities.
Dave
Aaron Bergman
In article <01bc9f8d$7eeb82a0$7144d6c3@thiele>, "J.Thiele"
<jthi...@SPAMtnet.de> wrote:
:
:No chance!
:I am going to ignore the fact, that your not going to get a whole lot of
:light from stopping the expansion of the universe.
:
:The nearest galaxy is approx. 8 lightyears (IIRC) away from us,
YDNRC. I'm not sure how far the nearest galaxy, but there are stars
farther than that. To pick one I know offhand for obvious reasons, Vega is
about 25 light years away. The Centauri triplet is about four to five
light years away, I think. I think the galaxy is on the order of tens of
thousands light years across.
Aaron
--
Aaron Bergman -- aber...@minerva.cis.yale.edu
<http://pantheon.yale.edu/~abergman/>
Smoke a cigarette. Slit your throat. Same concept.
Drew Gillmore
Kate Nepveu <kne...@lynx.neu.edu.CUT-HERE> wrote in article
<33e35a26...@nntp.neu.edu>...
> So I just finished Duane's _High Wizardry_, which I hugely enjoyed.
> The scene where the upgraded version of the turtles is released is
> marvelous, in particular. However, part of the ending is bugging me,
> namely the bit with Olber's Paradox. Spoilers, I guess.
>
>
>
> Okay. Dairine's [1] fighting the Lone Power and needs a lot of light.
> To get it, she makes a spell which makes the universe stop expanding.
> (NB: there's no statement that it's now contracting, just that it's
> stopped expanding. Later, she mentions cancelling the spell, which
> leads me to believe that it was a temporary holding of the expansion,
> not a reversal of it.) Within minutes, it becomes really bright from
> the galaxies, etc. which are no longer moving away.
>
> Now, I know next-to-nothing about the math involved here. And
> frankly, I don't need or want to know the math. But that doesn't
> sound right to me--it seems like it happens far too fast. Can any of
> our resident physics types tell me if this is even remotely plausibe?
The expanding of the universe causes blue and red shift in spectrum
lines[2}, but does not effect the *amount* of light that we get, AFAIK.
Considering that light travels in straight lines from the source in all
directions, If you stopped the universe from expanding, the same amount of
light would get to the Earth. The only difference would be that if you
analyzed the light's spectrum, it wouldn't be shifted at all.
>
> [1] Just how does one pronounce this, anyway?
I have no f-ing idea.
[2] Spectrum shift is how we know that the universe is expanding to begin
with. An analyzation of the light from distant galaxies shows the right
pattern of gaps in a spectrum, (From absorption by various elements) just
at the wrong place. From what we know from pulsar stars and variables,
especially binary star systems, the light waves are either compressed or
expanded depending on whether the source of the light is coming towards us
or moving away. If the object is moving towards us, the wavelength is
shorter, and therefore blue-shifted, and if it is moving away from us, it
is red-shifted. Analyzation of light from every galaxy we can see is
red-shifted, telling us that the light sources and all galaxies are moving
away from us, and therefore the universe is expanding.
I think I got that right, it's been a year since I had to think about it.
I may have the blue and red shifts backwards, but I think the rest is
correct.
--
Kid Probabillity kidprob...@hotmail.com
"What each man knows is, in an important sense,
dependant upon his own individual experience: he
knows what he has seen and heard, what he has
read and what he has been told, and also what,
from these data, he has been able to infer."
- B. Russell
Drew Gillmore
Aaron Bergman <aber...@pantheon.yale.edu> wrote in article
<abergman-030...@tip-mp17-ncs-9.stanford.edu>...
> In article <01bc9f8d$7eeb82a0$7144d6c3@thiele>, "J.Thiele"
> <jthi...@SPAMtnet.de> wrote:
> :
> :No chance!
> :I am going to ignore the fact, that your not going to get a whole lot of
> :light from stopping the expansion of the universe.
> :
> :The nearest galaxy is approx. 8 lightyears (IIRC) away from us,
>
> YDNRC. I'm not sure how far the nearest galaxy, but there are stars
> farther than that. To pick one I know offhand for obvious reasons, Vega
is
> about 25 light years away. The Centauri triplet is about four to five
> light years away, I think. I think the galaxy is on the order of tens of
> thousands light years across.
The nearest galaxy is the Large Magellanic Cloud, roughly 170,000 Light
years away and about 30,000 light years across. It is one of the two
"satellite galaxies" of the Milky Way, which is close to 200,000 light
years across. The Centauri Triplet, OTOH, is only 4.3 light years away,
and is/are the closest star(s).
HTH
Kid Probability
Kate Nepveu
This thread has been re-TANified (why it was de-TANned is beyond me.)
Rumor has it aber...@pantheon.yale.edu (Aaron Bergman) said:
>In article <01bc9f8d$7eeb82a0$7144d6c3@thiele>, "J.Thiele"
><jthi...@SPAMtnet.de> wrote:
>:The nearest galaxy is approx. 8 lightyears (IIRC) away from us,
>YDNRC. I'm not sure how far the nearest galaxy, but there are stars
>farther than that. To pick one I know offhand for obvious reasons, Vega is
>about 25 light years away. The Centauri triplet is about four to five
>light years away, I think. I think the galaxy is on the order of tens of
>thousands light years across.
I should point out that this took place very, very far away from the
Earth, over the "event horizon" of the Big Bang (not sure if that's
the proper term, but that's what Duane used--they're so far away that
we've never seen them.) I didn't get the impression that the
distribution of galaxies, stars, etc. was all that different from
here, though.
J.Thiele
Drew Gillmore <kidprob...@hotmail.com> wrote in article
<01bc9ff7$ca376de0$0c8a0ece@workstation>...
|
|
| Aaron Bergman <aber...@pantheon.yale.edu> wrote in article
| <abergman-030...@tip-mp17-ncs-9.stanford.edu>...
| > <jthi...@SPAMtnet.de> wrote:
| > :
| > :I am going to ignore the fact, that your not going to get a whole lot
of
| > :light from stopping the expansion of the universe.
| > :
| >
| > YDNRC. I'm not sure how far the nearest galaxy, but there are stars
| > farther than that. To pick one I know offhand for obvious reasons, Vega
| is
| > about 25 light years away. The Centauri triplet is about four to five
| > light years away, I think. I think the galaxy is on the order of tens
of
| > thousands light years across.
|
| years away and about 30,000 light years across. It is one of the two
| "satellite galaxies" of the Milky Way, which is close to 200,000 light
| years across. The Centauri Triplet, OTOH, is only 4.3 light years away,
| and is/are the closest star(s).
|
Eeeerrrrrr, did I really mistake Proxima Centauri with a Galaxy (and almost
double the distance) ?
I hope my old Astronomy teacher isn't reading this...
Sorry folks!
JTT
Justin H. Howell
aber...@pantheon.yale.edu (Aaron Bergman) writes:
>In article <01bc9f8d$7eeb82a0$7144d6c3@thiele>, "J.Thiele"
><jthi...@SPAMtnet.de> wrote:
>:
>:No chance!
>:I am going to ignore the fact, that your not going to get a whole lot of
>:light from stopping the expansion of the universe.
>:
>:The nearest galaxy is approx. 8 lightyears (IIRC) away from us,
>YDNRC. I'm not sure how far the nearest galaxy, but there are stars
>farther than that. To pick one I know offhand for obvious reasons, Vega is
>about 25 light years away. The Centauri triplet is about four to five
>light years away, I think. I think the galaxy is on the order of tens of
>thousands light years across.
Distance from the sun to the galactic center = 8.5 kpc +/- about 0.5 kpc
(not quite sure about the uncertainty). The stellar disk of the Milky
Way extends to a radius of about 14 kpc, with evidence for the gaseous
disk continuing to nearly 30 kpc. The LMC is 50 kpc away, and
Andromeda is 770 kpc distant. The Sagittarius dwarf is 24 kpc from
us, roughly 16 kpc from the center of the Milky Way. One can easily
find references by searching at
http://adswww.harvard.edu/abstract_service.html
Back to the original topic, the only way the spell described could
work would be if it retroactively changed the nature of the universe
to a form that allows Olber's paradox, which would then be a fatally
unpleasant place to live. A steady state universe of infinite age
would be easiest. If the character could do time travelling deity
strength spells, why was a relatively simple conjuration of a
searchlight (or something of that nature) not an option?
Justin Howell
jhho...@astro.columbia.edu
Andrea Lynn Leistra
In article <01bc9f8d$7eeb82a0$7144d6c3@thiele>,
J.Thiele <jthi...@SPAMtnet.de> wrote:
><33e35a26...@nntp.neu.edu>...
>| So I just finished Duane's _High Wizardry_, which I hugely enjoyed.
>| The scene where the upgraded version of the turtles is released is
>| marvelous, in particular. However, part of the ending is bugging me,
>| namely the bit with Olber's Paradox. Spoilers, I guess.
For those playing along at home, Olber's Paradox is the "Why is the night
sky dark?" question, answerable by the fact that the universe is finite
and that light has a finite speed.
>| Okay. Dairine's [1] fighting the Lone Power and needs a lot of light.
>| To get it, she makes a spell which makes the universe stop expanding.
>| (NB: there's no statement that it's now contracting, just that it's
>| stopped expanding. Later, she mentions cancelling the spell, which
>| leads me to believe that it was a temporary holding of the expansion,
>| not a reversal of it.) Within minutes, it becomes really bright from
>| the galaxies, etc. which are no longer moving away.
>|
>| Now, I know next-to-nothing about the math involved here. And
>| frankly, I don't need or want to know the math. But that doesn't
>| sound right to me--it seems like it happens far too fast. Can any of
>| our resident physics types tell me if this is even remotely plausibe?
No.
A few minutes or hours isn't going to have a noticeable effect on the
expansion of the universe, quite aside from the timing problems -- any
effect would take millions of years to be noticed.
And the expansion of the universe redshifts the light, but doesn't make it
go away.
>The nearest galaxy is approx. 8 lightyears (IIRC) away from us, meaning
>that its light takes _8 years_ to get here. The galaxies at the outer rim
>of the universe are just a little bit further out, I'm not sure of the
>distance right now (and to lazy to check, the truth be told), but were
>talking many _millions_ of years - at least.
And you are off by many, many orders of magnitude. The closest star to
the sun is a shade over 4 lightyears away, and the nearest galaxy[1] to
our own is about 2 megaparsecs, or about six *million* lightyears.
There is no "outer rim" of the universe. The most distant objects from us
(and, thus, the oldest) are several gigaparsecs out.
[1] Not including the Magellanic Clouds, which are satellite galaxies of
the Milky Way and not really independent. I don't know what their
separation is -- a couple hundred kiloparsecs, I think.
--
Andrea Leistra http://www-leland.stanford.edu/~aleistra
-----
Life is complex. It has real and imaginary parts.
Kate Nepveu
Rumor has it jhho...@alumnae.caltech.edu (Justin H. Howell) said:
>Back to the original topic, the only way the spell described could
>work would be if it retroactively changed the nature of the universe
>to a form that allows Olber's paradox, which would then be a fatally
>unpleasant place to live.
One of the characters does say "Olber's paradox in action," but as I
said, the text clearly indicates that the spell stopped the expansion
--nothing more complicated is indicated.
A steady state universe of infinite age
>would be easiest. If the character could do time travelling deity
>strength spells, why was a relatively simple conjuration of a
>searchlight (or something of that nature) not an option?
She needed a *lot* of light. No, really, I'm serious.
Kate Nepveu
Rumor has it alei...@leland.Stanford.EDU (Andrea Lynn Leistra) said:
>>Kate Nepveu <kne...@lynx.neu.edu.CUT-HERE> wrote in article
>><33e35a26...@nntp.neu.edu>...
[stopping expansion of universe makes sky really bright really fast]
>>|Can any of
>>| our resident physics types tell me if this is even remotely plausibe?
>No.
>A few minutes or hours isn't going to have a noticeable effect on the
>expansion of the universe, quite aside from the timing problems -- any
>effect would take millions of years to be noticed.
>And the expansion of the universe redshifts the light, but doesn't make it
>go away.
Okay. That's what I thought, but I wanted someone who actually knew
what they were talking about to back me up...
Pity, it's a good ending otherwise. Ah well...
Devin L. Ganger
In our last episode, Andrea Lynn Leistra <alei...@leland.Stanford.EDU> wrote:
: For those playing along at home, Olber's Paradox is the "Why is the night
: sky dark?" question, answerable by the fact that the universe is finite
: and that light has a finite speed.
: No.
: A few minutes or hours isn't going to have a noticeable effect on the
: expansion of the universe, quite aside from the timing problems -- any
: effect would take millions of years to be noticed.
: And the expansion of the universe redshifts the light, but doesn't make it
: go away.
If the expansion of the universe were halted, wouldn't some light that
was previously redshifted out of the visible spectrum be moved into the
visible spectrum? (Of course, visible light at the other end would be
subsequently blue-shifted right out of the visible spectrum, too).
So which direction would the shifting favor, and would the subsequent
increase/decrease of light produce enough effect to be noticeable?
--
Devin L. Ganger, a.k.a. The Most Arrogant Fictional Dead Man On The Net
http://www.teleport.com/~lewst/ -- The G-Files and other assorted stuff
http://www.teleport.com/~lewst/grue.html -- Join the fight against spam
All unsolicited commercial email will be billed for a $500 handling fee
Rick Moen
: the Milky Way and not really independent. I don't know what their
: separation is -- a couple hundred kiloparsecs, I think.
Greater Magellanic Cloud: 179,000 light years (55 kiloparsecs)
Smaller Magellanic Cloud: 210,000 light years (64 kiloparsecs)
Sagittarius Dwarf Elliptical Galaxy (discovered in 1994): 80,000 light years
(25 kiloparsecs)
All part of our cozy little Local Group.
--
Cheers,
Rick Moen "vi is my shepherd; I shall not font."
rick (at) hugin.imat.com -- Psalm 0.1 beta