PDA

View Full Version : Neutron star



Ring
2001-Dec-01, 06:25 PM
I have just finished reading "Dragon's Egg" by Robert Forward and I find myself confused by some of the physics involved.

The molecular creatures (the Cheela) living on a neutron star find it much easier to travel along the intense magnetic field lines rather than having to travel across them. But it would seem that the qv X B force on the protons in the nuclear material of their bodies would be radial not rearward? Plus, it seems there would be as many electrons as protons and therefore the net force would be zero. Anybody know what's going on?

They also find it a lot easier to see in the direction of field lines. Why would that be so?

Azpod
2001-Dec-01, 07:16 PM
On 2001-12-01 13:25, Ring wrote:
I have just finished reading "Dragon's Egg" by Robert Forward and I find myself confused by some of the physics involved.

The molecular creatures (the Cheela) living on a neutron star find it much easier to travel along the intense magnetic field lines rather than having to travel across them. But it would seem that the qv X B force on the protons in the nuclear material of their bodies would be radial not rearward? Plus, it seems there would be as many electrons as protons and therefore the net force would be zero. Anybody know what's going on?

They also find it a lot easier to see in the direction of field lines. Why would that be so?


Cool book; I need to pick up the sequel someday. I don't know much about the physics of a neutron star, so I can't make any statements about the magnetic field lines making movement more difficult. I thought charged particles moved along magnetic field lines because any velocity tangental to them would produce a force parallel to the lines. But I could be terribly wrong; it's been a while since I studied magnetism in any serious fashion.

However, the reason that the bodies of the Cheela were not neutral is because the engeries required to sustain the nuclear reactions within their bodies are much higher than are allowed for the electrons to bind with the nuclei and form atoms. That's why they were alive on the surface of the neutron star: they used nuclear rather than chemical reaction for all of their life processes.

All in all, a very cool premise for a story.

Wiley
2001-Dec-01, 10:13 PM
On 2001-12-01 13:25, Ring wrote:
I have just finished reading "Dragon's Egg" by Robert Forward and I find myself confused by some of the physics involved.

The molecular creatures (the Cheela) living on a neutron star find it much easier to travel along the intense magnetic field lines rather than having to travel across them. But it would seem that the qv X B force on the protons in the nuclear material of their bodies would be radial not rearward? Plus, it seems there would be as many electrons as protons and therefore the net force would be zero. Anybody know what's going on?

They also find it a lot easier to see in the direction of field lines. Why would that be so?



I think you're right. The force on an electric charge should be perpendicular to the magnetic field. This seems to imply they would be going in circles alot.

Of course if they had magnetic charge, they would find moving in the direction of the field easier (or harder). Just because we have never detected a magnetic monopole, does not mean it does not exist.

David Hall
2001-Dec-02, 09:14 AM
It's been a while since I read it, but I seem to remember something about the effect of the magnetic field on the surface itself. I don't think the Cheela fought the field itself so much as the ground they travelled on. The crystalline structure of the surface tended to align with the east-west field, making it easier to travel in that direction than across it. Also I remember when the expedition to the east(?) pole started getting near it, they had a hard time moving in any direction because the crystals were aligning in a vertical direction.

That's my thinking, I'm no expert. Actually, I don't even fully understand the point of the OP.

Apzod, I have a paperback rinting that combines both Dragon's Egg and Starquake in one volume. Starquake is just as interesting in it's own way, but I was a little dissatisfied by the ending. I don't want to give it away for people who haven't read the book, but I think even Forward kind of forgot one or two of the basic premises of his creation.

Ring
2001-Dec-02, 03:21 PM
On 2001-12-01 14:16, Azpod wrote:
[quote]
However, the reason that the bodies of the Cheela were not neutral is because the engeries required to sustain the nuclear reactions within their bodies are much higher than are allowed for the electrons to bind with the nuclei and form atoms.


Yes, but the electrons would still be there. They'd just be degenerate, and therefore the qv X b force would act both away from the surface and towards the surface, in other words it would be compressive in nature.

At another forum someone suggested that eddy currents might be the answer, however I don't see where the change in magnetic flux would come from. It would seem that the magnetic field would be uniform at the surface of the star.

Tim Thompson
2001-Dec-02, 10:07 PM
Good book, I thought; long time since I hace read it.

In the Lorentz force formula F = q(E + VxB) if the angle between the V and B vectors is zero, then so is the value of VxB zero. Assuming there is no E either, then moving along the field line produces no resulting force. Moving in any other direction will produce a force, and it really does not matter in principle what the direction of the force is; it's fair to say (I think) that "no force" is always the preferable situation. However, if the V vector is parallel to the surface of the star, then it will be coplanar to the magnetic field lines, which are dipolar and more or less parallel to the surface as well (or so I recall the story model). In that case, using the right hand rule for the direction of VxB (curl the fingers of your right from V to B), then the force will be either up or down, depending on the charge q. However, since q for electrons and protons is of opposite signs, so will the force VxB be in opposite directions. Hence, trying to move in the wrong direction, will subject the creature not to a net zero force, but to internal stress that tends to tear it apart.

<font size=-1>[ This Message was edited by: Tim Thompson on 2001-12-02 17:08 ]</font>

Ring
2001-Dec-03, 12:11 AM
On 2001-12-02 17:07, Tim Thompson wrote:
<snip>
Hence, trying to move in the wrong direction, will subject the creature not to a net zero force, but to internal stress that tends to tear it apart.


I agree that there would be two forces that would tend to pull the Cheela apart rather than compress them as I erroneously stated earlier. But it would seem that the net force would still be zero. I.e. the up force equals the down force, and adding the two together equals zero.

However, this is still not to the point. The book clearly says that there exists a force that impedes forward progress when moving across the field lines. The only thing I can figure is that somehow there is an induced eddy current with its concomitant drag. I just can't figure out what causes the changing magnetic flux.

I also don't see why seeing in the field direction is easier than seeing in the direction across the field lines.

Kaptain K
2001-Dec-03, 12:39 AM
The only thing I can figure is that somehow there is an induced eddy current with its concomitant drag. I just can't figure out what causes the changing magnetic flux.
The change in the magnetic flux is caused by the movement across the magnetic field lines. Just like a current can be induced in a wire by moving the field OR by moving the wire.The Cheela feel the force only when they try to move across the the field.

ljbrs
2001-Dec-03, 01:49 AM
I think that the characteristics of a neutron star would preclude anything from living on one. The gravity would crush anything and everything. Note that most of its material has already been compressed to form neutrons (whereas with white dwarf stars, the electron degeneracy prevents this). Of course, if much more mass is added (as with an accretion disk pulling sufficient matter from the outer envelope of a nearby red giant star), it might end up as a black hole where nothing (including light) escapes the singularity.

Science fiction is not science and the plot line could not get anywhere if it were true to science. I would not look to science for answers for science fiction where none can possibly exist.

ljbrs /phpBB/images/smiles/icon_wink.gif /phpBB/images/smiles/icon_wink.gif

<font size=-1>[ This Message was edited by: ljbrs on 2001-12-02 20:55 ]</font>

Ring
2001-Dec-03, 02:46 AM
On 2001-12-02 19:39, Kaptain K wrote:

The change in the magnetic flux is caused by the movement across the magnetic field lines. Just like a current can be induced in a wire by moving the field OR by moving the wire.The Cheela feel the force only when they try to move across the the field.



I don't think that's the way it works. If you move a coil of wire through a *uniform* magnetic field there's no d(phi)/dt and therefore no induced EMF. And as far as I can see the magnetic field would be constant at surface of the star.

<font size=-1>[ This Message was edited by: Ring on 2001-12-02 21:47 ]</font>

<font size=-1>[ This Message was edited by: Ring on 2001-12-02 22:04 ]</font>

Ring
2001-Dec-03, 02:50 AM
On 2001-12-02 20:49, ljbrs wrote:
I think that the characteristics of a neutron star would preclude anything from living on one. The gravity would crush anything and everything. Note that most of its material has already been compressed to form neutrons (whereas with white dwarf stars, the electron degeneracy prevents this). Of course, if much more mass is added (as with an accretion disk pulling sufficient matter from the outer envelope of a nearby red giant star), it might end up as a black hole where nothing (including light) escapes the singularity.

Science fiction is not science and the plot line could not get anywhere if it were true to science. I would not look to science for answers for science fiction where none can possibly exist.

ljbrs /phpBB/images/smiles/icon_wink.gif /phpBB/images/smiles/icon_wink.gif



Rober L. Forward is a Phd physicist and he is known for his accurate physical descriptions.

David Hall
2001-Dec-03, 02:54 AM
On 2001-12-02 20:49, ljbrs wrote:
I think that the characteristics of a neutron star would preclude anything from living on one.


As I understand it, Forward's story concept was taken from an actual paper on the possibility of life on a Neutron star.

The creatures can exist in that environment because they themselves are as dense as their world, and their life systems are based on nuclear, not chemical, reactions. Imagine a human being crushed into the size of a sesame seed (and still living and thinking) and you have an idea of the size and density of the Cheela.

ljbrs
2001-Dec-04, 02:37 AM
Rober L. Forward is a Phd physicist and he is known for his accurate physical descriptions.


I think he was writing science fiction there.




As I understand it, Forward's story concept was taken from an actual paper on the possibility of life on a Neutron star.

The creatures can exist in that environment because they themselves are as dense as their world, and their life systems are based on nuclear, not chemical, reactions. Imagine a human being crushed into the size of a sesame seed (and still living and thinking) and you have an idea of the size and density of the Cheela.



I think that it is highly improbable that anything like this has actually been studied under scientific conditions. Where have such creatures been studied?

When someone is writing science fiction, he (or she) is hardly doing science. He (or she) is having fun (and making a lot of money if it is good). Fun is fine, but it sometimes makes for a good old "roll on the floor, laughing".

Then again, the science fiction discussed here must have been very, very entertaining.

ljbrs /phpBB/images/smiles/icon_eek.gif

Kaptain K
2001-Dec-04, 02:58 PM
ljbrs,
I very seriously suggest that you read the book (Dragon's Egg by Robert L. Forward Ph.D) before you criticize the physics of Dr. Forward. He is a full time physicist and part time science fiction writer. The hallmark of all of his science fiction is his adherence to currently known principals of physics. In other words, it may be "science fiction", but it violates none of the laws of physics as they are currently known.

2001-Dec-04, 04:54 PM
The molecular creatures (the Cheela) living on a neutron star find it much easier to travel along the intense magnetic field lines rather than having to travel across them. But it would seem that the qv X B force on the protons in the nuclear material of their bodies would be radial not rearward?

Yes. The force would depend on latitude. It would mostly be horizontal, either up or down. However, they may have to fight forces that are similiar to our frictional forces: kinetic friction and static friction. These forces increase with normal force. If these creatures were pushed down, it would increase the normal force. They would have difficulty moving across the lines. If up, they could skid.
There is also the point that the magnetic field won't be EXACTLY horizontal. The small component of the field parallel to the surface could also cause difficulties in most latitudes. The books never described an expedition to the pole. There, the effect would be MUCH different than Forward describes.


Plus, it seems there would be as many electrons as protons and therefore the net force would be zero. Anybody know what's going on?


I think that they would have to be charged just because of the heat emanating from the neutron star through them. Friction from air currents create a separation in charge. Our own atmosphere has an electric field caused by air currents that whose friction creates charge separation. We have a slight electric charge too. However, our magnetic field is not nearly strong enough to interfere with us.
The thermocouple effect could also contribute to charge separation. The surface of Dragonsegg is different from the atmosphere, almost like two dissimiliar metals. The surface is heated, so it would be at a higher temperature than the atmosphere. There would be a strong thermocouple effect. That could also create a charge on the Cheela.
The Cheela live in a stronger magnetic field and they move much faster than we do. This would increase the effect of a magnetic field. The Cheela wouldn't need a strong electric charge to be affected.
This "latitude" effect would be the only situation on the Cheela world where electromagnetic forces are strong enough to actually feel. However, given the fact it would be strong, they may develop electromagnetic theory sooner than Forward says they would.



They also find it a lot easier to see in the direction of field lines. Why would that be so?

The atmosphere of Dragonsegg is probably birefringent due to the Faraday effect. A hot plasma is oriented by a strong magnetic field. When they look across the field lines, they are looking partly at extraordinary rays which move in curved lines. When they look with the magnetic field, they see ordinary rays which move in a straight line.


Some explanation of the premise should be given. The baryons in nucleii (i.e., neutrons and protons) interact by strong and weak nuclear forces.
The Cheela have a biology based mostly on the strong nuclear force. Lets consider what goes on in a very heavy nucleus. For the outermost baryons, there are quantum shells very similiar to the electronic shells in atoms. The innermost baryons of the nucleous form a compact mass, similiar to a droplet of liquid. The outermost baryons orbit the innermost baryons in quantized orbits. This system resembles an atom, at least superficially. It could even form "bonds" with other systems like it. There could be complex "molecules" made of nucleii with no electrons bound to them.
Experiments with colliding nucleii show that there are nuclear reactions analogous to chemical reactions. So the premise is plausible in a wild sort of way.
On a neutron star, the conditions could be just right for "biochemistry" to occur with baryons rather than with electrons, but the scale of these reactions would be much smaller and much faster. What we call chemical reactions could not occur at the temperature and pressure of a neutron star, but nuclear reactions at this temperature and pressure are possible.
Forward used all this in the Dragonegg series.

Note that these creatures disintegrate "slowly" in a vacuum. Their skin peels off. This would be because of the "weak" nuclear force. Since they move by the strong force, the disintegration looks slow to them. However, it would be a rapid explosion to us creatures with a chemistry based on electromagnetic forces.


<font size=-1>[ This Message was edited by: Rosen1 on 2001-12-04 12:31 ]</font>

ljbrs
2001-Dec-06, 01:45 AM
Where does Dr. Forward do his physics? Where has he published? It would be interesting to read what he has written in science before I attempt his science fiction.

ljbrs /phpBB/images/smiles/icon_rolleyes.gif /phpBB/images/smiles/icon_smile.gif

Kaptain K
2001-Dec-06, 10:25 AM
ljbrs wrote:
Where does Dr. Forward do his physics?
At Forward Unlimited, a company he founded in 1962.


Where has he published?
His home page,
http://www.whidbey.com/forward/index.html has a link titled "technical papers" that lists 168 publications.
That should be sufficient to sate your curiosity.


_________________
TANSTAAFL!

<font size=-1>[ This Message was edited by: Kaptain K on 2001-12-06 05:32 ]</font>

ljbrs
2001-Dec-07, 12:48 AM
That is a .com site. For my understanding of science, I only visit .edu and .gov (the sites for governmental science laboraties). He seems to be a great science fiction writer and a great businessman (more lucrative). This does not mean that what he necessarily writes agrees completely with science. If he did, he would never had made any money or had any followers.

I am certain that his science education can only help him avoid blatent scientific errors in his science fiction. I do not get my science from science fiction. If you take your science from science fiction, that is all right with me.

ljbrs /phpBB/images/smiles/icon_rolleyes.gif /phpBB/images/smiles/icon_wink.gif /phpBB/images/smiles/icon_wink.gif /phpBB/images/smiles/icon_biggrin.gif

Torsten
2001-Dec-07, 06:58 AM
ljbrs said:

<blockquote>"That is a .com site. For my understanding of science, I only visit .edu and .gov (the sites for governmental science laboraties)."</blockquote>

If I understand you correctly, I think you are using ".edu" and ".gov" as a criterion or filter for considering the validity of science information. I believe you are arbitrarily and unnecessarily limiting your sources of information.

Consider, for example, that Nature (http://www.nature.com/nature/), which is undoubtedly a top class primary source of scientific information, is a .com site. (Even our very own GrapesofWrath has had a letter published there.)

Then there is Science (http://www.sciencemag.org/), or The Proceedings of the National Academy of Sciences (http://www.pnas.org/), both of which are ".org" sites. Science has published wonderful papers and review articles on astronomy topics. (PS, ljbrs, I know you're a subscriber /phpBB/images/smiles/icon_wink.gif ). PNAS has free access to its articles on-line after 6 months, BTW. Actually, you can still get this year's articles after 4 weeks -- they're changing policy. What a fantastic resource!

Through my Canadian ISP I have free access to all the journals published by Canada's National Research Council Press (http://www.nrc.ca/cgi-bin/cisti/journals/rp/rp2_jour_e). This is a ".ca" site.

And don't forget our host. Phil's Bad Astronomy (http://www.badastronomy.com/) is a site devoted to explaining things in very understandable fashion about our branch of science.

And though the following is drifting from astronomy, I want to underscore the necessity of using our baloney detection tools rather than an arbitrary ".edu" domain as a criterion for evaluating sites. Consider this "technical paper" (http://origins.swau.edu/papers/man/hominid/default.html) from this ".edu" site (http://origins.swau.edu/). Read the first paragraph of the summary. There's science for ya! [/sarcasm]

I hope I have misunderstood your reasoning. If so, please forgive my rant.

David Hall
2001-Dec-07, 01:03 PM
I just checked my copy of Dragon's Egg. I wanted to see who it was who actually postulated the idea of life on a neutron star. I think you'll recognize the name: Dr. Frank Drake. /phpBB/images/smiles/icon_smile.gif

Here's how Forward developed the idea for his novel:

http://www.space.com/sciencefiction/books/forward_000328.html

and here:

http://www.space.com/sciencefiction/books/forward_egg_000328.html


And ljbrs, I agree with Torsten. It's good to be cautious, but just because it has .com on it, doesn't mean a site isn't factual (and vice-versa, for that matter). Forward is a published author with his own business, so it's natural that he would use a .com address. But that doesn't dissuade the fact that he's also a highly-regarded physicist who writes factually accurate SF stories. I've only personally read the 2 novels mentioned here, but from those, I would consider him one of, if not the "hardest" of hard science fiction writers.

Kaptain K
2001-Dec-07, 06:54 PM
ljbrs,
It is obvious from your reply, that you did not actually check out the technical publications list on the web-site. You saw ".com" and ignored it. If you honestly believe that all .com sites are ** and that everything on .gov and .edu sites are the unquestionable gospel, you are in extreme danger of being led far astray.
Do the names:

Nature
Am. Phys. Soc.
American Journal of Physics
J. Applied Physics
Physical Review
Physical Review Letters

mean anything to you? These are just a few of the refereed, peer reviewed journals in which Dr. Forward has been published. Many of the articles are linked from the list.

ljbrs
2001-Dec-08, 02:10 AM
Whatever... It looks as if Dr. Forward's work is highly regarded.

However, .com and .gov would not pertain to magazines such as SCIENCE and NATURE, because .com and .gov are reserved for educational and research institutions (from what I have been told by my *real scientist* friends). However, both SCIENCE and NATURE have excellent reputations.

And this site is a .com site (but there is a real astronomer, BADASTRONOMER, supervising the BABB).

Then again, I am not a professional scientist, so I cannot possibly know what is correct. For this reason, I am careful for myself, because there is so much baloney floating around on the web.

Whatever...

ljbrs /phpBB/images/smiles/icon_wink.gif

Hat Monster
2001-Dec-09, 07:24 PM
However, .com and .gov would not pertain to magazines such as SCIENCE and NATURE, because .com and .gov are reserved for educational and research institutions

You meant .edu didn't you? .gov is for the US government only. They have a total monopoly over that TLD, although there are hacked DNS entries which I'll leave to the reader to discover.
.edu is used for US educational establishments. Other, civilized, nations use .ac.** where ** is the country in question and AC means "academic" which is rather more appropriate.

.org was meant to be for non-profit organizations but got tarnished by religious nutcases and eventually became a free-for-all.

.com is what .org has become. It was originally for commercial ventures.

.net was for Internet structure maintainers such as backbones and ISPs. That's also now a free-for-all.

So .org, .net, .com are identical in use, only .gov, .edu, .gov.**, .ac.** and a few other ones are means tested. There are several means tested TLDs that have yet to have any DNS entry for them.

ToSeek
2001-Dec-10, 03:51 PM
On 2001-12-09 14:24, Hat Monster wrote:
.org was meant to be for non-profit organizations but got tarnished by religious nutcases and eventually became a free-for-all.

.com is what .org has become. It was originally for commercial ventures.



Yeah, I actually got chided by another member of a non-profit club I'm in for setting us up as a ".org" instead of a ".com" because she thought more people would find us as the latter. It seems to be self-selecting at this point.

David Hall
2001-Dec-10, 04:29 PM
The problem with all of these suffixes is that nobody ever bothered to set up or enforce any of the divisions as they were originally conceived. so now the whole thing is generally a free-for-all without any logic to it.

And it's only getting worse with the new domain suffixes being created now, forcing organizations to shell out even more money to protect their names across more domains. Even more confusion is coming from the new attempt to create addresses in non-alphabetic languages like Japanese and Chinese. Those serve no purpose but to exclude anyone outside of the home turf and further confuse and balkanize the whole mess. How many of you can enter a Japanese URL into your browsers?

It's all crazy. I take everything on the net with a grain of salt unless I know I can trust the source. Even then it pays to be a bit sceptical, as this page shows: /phpBB/images/smiles/icon_biggrin.gif

http://www.snopes2.com/index.html

ljbrs
2001-Dec-12, 01:48 AM
You meant .edu didn't you? .gov is for the US government only. They have a total monopoly over that TLD, although there are hacked DNS entries which I'll leave to the reader to discover.
.edu is used for US educational establishments. Other, civilized, nations use .ac.** where ** is the country in question and AC means "academic" which is rather more appropriate.

I typed *.edu* and *.gov* and meant exactly that. *.gov* can refer to governmental laboratories and would not be *.edu* sites, but would be where the governmental scientific research laboratory sites would be located on the web.

ljbrs /phpBB/images/smiles/icon_biggrin.gif /phpBB/images/smiles/icon_wink.gif

Kaptain K
2001-Dec-12, 06:16 AM
ljbrs,
I direct your attention to this excerpt from a post by you.

Posted: 2001-12-07 21:10
... .com and .gov are reserved for educational and research institutions ...
now, tell us again how you typed .edu and .gov.

ljbrs
2001-Dec-15, 01:27 AM
ljbrs,
I direct your attention to this excerpt from a post by you.
Quote:
--------------------------------------------------------------------------------

Posted: 2001-12-07 21:10
... .com and .gov are reserved for educational and research institutions ...

--------------------------------------------------------------------------------


now, tell us again how you typed .edu and .gov.
_________________
TANSTAAFL!


Did I type that? Dumb! Of course, I did not mean to type ".com", but I did. I lost my concentration and simply typed merrily along without paying attention to what I was typing.

I am not a scientist, so I am careful where I get my information. I have been advised by my scientist friends that .edu and .gov sites are generally much better for that purpose. (Now, all of the time that I have been writing this, I have mistyped .com over and over again and have had to delete it each time I did so.)

Of course, Bad Astronomy is a .com site, but it is a good one, and it has a bona fide astronomer at the prime focus.

However, I do believe that .edu and .gov sites are best for scientific information. For further information, I also subscribe to SCIENCE, NATURE, PHYSICS TODAY, PASP (Publication of the Astronomical Society of the Pacific), plus a number of astronomy magazines, such as MERCURY, SKY & TELESCOPE, and ASTRONOMY.

Thank you for pointing out that dumb mistake. Some of the people here will like to get a laugh over my carelessness.

ljbrs /phpBB/images/smiles/icon_eek.gif /phpBB/images/smiles/icon_redface.gif /phpBB/images/smiles/icon_rolleyes.gif /phpBB/images/smiles/icon_wink.gif

GrapesOfWrath
2001-Dec-15, 02:58 AM
Hahahahaha he thinks .com sites are for dummies

ljbrs
2001-Dec-15, 11:17 PM
Oh, I was just speaking generally (from advice given to me by my scientific and programmer friends. I know of a lot of .com sites, such as:

http://www.superstringtheory.com

and

http://www.badastronomy.com

which are just great. I am almost certain that there must exist many .edu and .gov sites which are questionable.

However, anyone can use .com, but there are certain qualifications which must be met in order to use .edu and .gov in URLs.

ljbrs /phpBB/images/smiles/icon_eek.gif /phpBB/images/smiles/icon_rolleyes.gif /phpBB/images/smiles/icon_wink.gif

GrapesOfWrath
2001-Dec-16, 01:47 AM
Didn't Archimedes Plutonium have an .edu site once?

ljbrs
2001-Dec-17, 01:37 AM
Didn't Archimedes Plutonium have an .edu site once?


Beats me. Archimedes was an ancient Greek mathematician, engineer, and physicist and was a bit before my time.

Archimedes Plutonium (whoever), if he exists, is an unknown person to me.

ljbrs /phpBB/images/smiles/icon_biggrin.gif /phpBB/images/smiles/icon_eek.gif

Ilya
2001-Dec-17, 02:15 AM
Archimedes Plutonium is a well-known nutcase on sci.physics, and several other Usenet groups. He's been posting bizarre theories for years. I did not know he had a web page, but his e-mail address is Archimedes.Plutonium@dartmouth.edu, so he may have a web page provided by that college.

David Hall: What problem do you see with "Starquake" ending? I read it more than 10 years ago, but don't remember any obvious contradiction.

lbjrs: Correct me if I am wrong, but you seem to think that all of a neutron star is a uniform ball of neutrons. That's not true - this (http://www.astro.umd.edu/~miller/nstar.html) describes how density and composition changes with depth.

David Hall
2001-Dec-17, 04:05 AM
On 2001-12-16 21:15, Ilya wrote:

David Hall: What problem do you see with "Starquake" ending? I read it more than 10 years ago, but don't remember any obvious contradiction.



It's going to be a little difficult to give my opinions without giving away spoilers, but I'll give it a shot.

It's not that there were contradictions with the ending so much as it was inconsistant with the rest of the books. If you remember, at the end of Starquake, the humans were trapped with no way to get home after sacrificing their gravity assist to help the Cheela. There was no way they could survive for 6 months for the second asteroid to arrive and give them another chance to go home.

Well, doesn't it seem really strange that advanced beings capable of interstellar travel and generating artificial black holes would be unable to come up with a solution to boost them out of the gravity well or advance the other asteroid along in it's orbit? Especially since, with their accelerated speed, they had plenty of time to think about it. Yet everyone gets all despondent and fatalistic after only a few hours. Why not sit back and discuss the problem for a few (human) days before getting worried about it?

And the solution they finally came up with feels very contrived to me, and once again ignores the difference in time perception. The Cheela had to start their project and then wait 6 months before coming back to finish it. That's like what, 50,000 years to them? Who knows what would happen to their society by then? Would they even remember what they were supposed to do by then? Their civilization could go through half a dozen fallings and risings in that time. Just too much uncertainty in my opinion. I wouldn't trust my great^nth grandson to finish the job for me.

What I feel is that Forward came up with a gee-whiz way to end the story and then warped everything to make it happen, regardless of how well it fit in with the rest of the series. It was a cool idea, and of course it fits in with scientific theory, but it just doesn't make logical sense in the situation. I feel it was a mediocre ending to an otherwise incredible pair of books. /phpBB/images/smiles/icon_biggrin.gif

ljbrs
2001-Dec-21, 01:11 AM
lbjrs: Correct me if I am wrong, but you seem to think that all of a neutron star is a uniform ball of neutrons. That's not true - this describes how density and composition changes with depth.

I have read a lot about degenerate matter. I just do not get my scientific understanding from science fiction, even if it is written by a creditable scientist. Science fiction is science fiction. Its purpose is entertainment, not enlightenment.

ljbrs /phpBB/images/smiles/icon_wink.gif /phpBB/images/smiles/icon_eek.gif /phpBB/images/smiles/icon_razz.gif /phpBB/images/smiles/icon_rolleyes.gif

2001-Dec-27, 12:58 AM
And the solution they finally came up with feels very contrived to me, and once again ignores the difference in time perception. The Cheela had to start their project and then wait 6 months before coming back to finish it. That's like what, 50,000 years to them?

In both books, it is clear that the more advanced Cheela civilizations have developed a method of restoring youth. Something to do with triggering a dormant state by trauma, where the dormant Cheela is using it's muscles for food. In any case, the beings in advanced Cheela society are immortal. This leads to a continuity of corporate memory that exists on a time scale that even us electrical force beings can use. The humans are having conversations with Cheela who are living maybe 1000 times longer than their "natural" lifetimes, so a million times faster per natural generation really is only a thousand times more faster per life prolonged generation.
I don't know how valid this assumption is, but other science fiction writers use it. Larry Niven uses it in "Time Out of Mind." The immortal "Boys" in the story have a tradition that lasts millions of years, partly because the "Boys" can live a couple of thousand.


Who knows what would happen to their society by then? Would they even remember what they were supposed to do by then?

This is exactly why the humans thought they were toast. They knew how unstable Cheela society could be. Suppose your life depended on whether one could actually find the Book of Jashur, supposedly written 3000 years ago but never found? You may dispair too.


Their civilization could go through half a dozen fallings and risings in that time. Just too much uncertainty in my opinion. I wouldn't trust my great^nth grandson to finish the job for me.

Exactly. That was the reason for the dispair.
There are some questions in my mind though. The one who starts the "Save the Humans" program dies of old age at the finish, happy knowing that he accomplished his lifes work. I thought that the Cheela had rejuvenation treatments. What happened?


What I feel is that Forward came up with a gee-whiz way to end the story and then warped everything to make it happen, regardless of how well it fit in with the rest of the series. It was a cool idea, and of course it fits in with scientific theory, but it just doesn't make logical sense in the situation. I feel it was a mediocre ending to an otherwise incredible pair of books. /phpBB/images/smiles/icon_biggrin.gif

I think that Forward shares a problem with Hal Clement. His aliens have a psychology are too similar to that of a upper middle class, late twentieth century society. On the other hand, most SF stories tend to be hominid-centric. Understanding a story that was based on a culture that was very different from mine would be too difficult. I have enough difficulty understanding Hub'. /phpBB/images/smiles/icon_razz.gif