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KP Lee wrote: Again, this station is like a top. That top continues to point to the center of the Earth against Earth's massive gravity trying to upend it.
But that doesn't sound right to me. the reason a top upends is because its point cannot move, but the rest of it can.
If you stand a pencil on a table it will fall over.
If you drop a pencil from a height it will land point down.
The Earth isn't trying to upend it!
The gyroscope effect will keep a spinning body oriented in the same direction, relative to the universe, as it moves - so you are right in that, if the axis is pointing toward the moon, and the ship is in orbit, then it would tend to rotate through a vertical plane through 360 degrees each orbit.
H suggests the tidal forces act on the ship - so is he assuming the tidal force is great enough to overcome the gyroscopic force?
PooperPig - Coming Soon
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Maxxx wrote: the reason a top upends is because its point cannot move, but the rest of it can.
Sort of right, but not quite. The top upends because the point is not a stable platform. You try to balance a top on it's point and let go, within seconds it will have tipped over. (Unless you stick it in sand, but that just widens the support base.) It doesn't immediately topple when you release the spinning top because the gyroscopic force overcomes the natural desire to topple and the point is a quite stable platform. In fact if the top lands unbalanced it will spin in smaller and smaller circles until the point comes to a complete stop (Relative to the floor location) and spins in place. The point hitting the floor is an anchor point that tries to keep the top in one place. The gyroscopic action is the stabilizing force. It finally becomes an unstable platform as the top slows it's spin.
Maxxx wrote: so is he assuming the tidal force is great enough to overcome the gyroscopic force?
I can't know what he is assuming. A spaceship with multiple rings ranging from 0.01 G's through 1 g levels would be massive, probably in the millions of KGms of material. Yes, the closer the orbit the bigger the tidal force, but the moon hasn't come close to stopping the Earth. I'm guessing putting a 100 Gm Top spinning in a 100 M orbit around the moon would take more than a month to stop spinning because of tidal forces. (It would fairly quickly start precessing.)
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Gjeltema wrote: he peaked with Time Enough for Love
Have to agree with you there, although Moon is a Harsh Mistress is my favourite among many. I have read a number of authors who are touted as the new Heinlein, Spider Robinson comes to mind, but they are not a patch on the RAH.
I think having someone pick at his scientific accuracy after he is dead would hugely amuse him.
Never underestimate the power of human stupidity
RAH
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Given your username, I'm not surprised that Moon is a Harsh Mistress is your favorite. 
I thoroughly enjoyed most of his books/stories before and after Time Enough for Love, I just personally found that to be his best book (it's one of my top 2 favorite books overall).
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Most think Mycroft comes from the detective guy, I always liked the idea of a self aware computer 
Never underestimate the power of human stupidity
RAH
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I must come to Heinlein's defence here.
The quote comes from Chapter 8 of The Cat Who Walks Through Walls. We have a cylindrical space station, spinning about the cylinder's axis. This gives you a space station made of cylindrical shells, each with its own level of gravity due to centripetal force.
The cylinder is quite long (at least a few hundred meters, judging by the presence of scooters inside), and was built with the axis of the cylinder pointing at the Moon. For a non-rotating cylinder, this position will be maintained because the gravitational pull on the near end of the cylinder is higher than that on the far end. This is your tidal lock.
As I see it, the problem here is that the cylinder is rotating. Forcing the axis to always point at the moon requires torque to be applied, and I am unsure whether the Moon's gravitational force provides enough. I have not read the book recently, but IIRC it doesn't give us enough information to do the calculation.
[Height over the Moon's surface - 300km (Chapter 9)
Length of the cylinder - ???
Radius of the cylinder - ??? <==> Rate of rotation - ???]
If Heinlein sinned here, it was not a great sin.
Gentlemen (and Ladies) of the Jury, give me your verdict. 
If you have an important point to make, don't try to be subtle or clever. Use a pile driver. Hit the point once. Then come back and hit it again. Then hit it a third time - a tremendous whack.
--Winston Churchill
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Your Honour; he mentions not if the cylinders were counter-rotating either ... not sure if it makes a difference, anyway, but wouldn't counter-rotating areas cancel out the gyroscope effect and allow it to maintain its attitude?
PooperPig - Coming Soon
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You have to have all cylindrical shells rotating in the same direction, otherwise transferring from one shell to the next would require very precise timing (think about it...). The same reasoning applies to an extension of the cylinder.
If you have an important point to make, don't try to be subtle or clever. Use a pile driver. Hit the point once. Then come back and hit it again. Then hit it a third time - a tremendous whack.
--Winston Churchill
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Think paternoster
PooperPig - Coming Soon
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If the cylindrical shells were counter-rotating, you would still have a problem of the lift going through the shells. I don't see how you would arrange this without the shells being in segments, broken where the lift goes through the shell.
I'm not a mechanical engineer, so perhaps there is a way to get this to work, but I can't see it.
If you have an important point to make, don't try to be subtle or clever. Use a pile driver. Hit the point once. Then come back and hit it again. Then hit it a third time - a tremendous whack.
--Winston Churchill
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you don't need a lift - as far as you're concerned it's walking through a doorway from one to the other - might be a bit jerky on the old legs I suppose, but it's not vertical, it's horizontal (from a 'gravitational perspective' point of view)
PooperPig - Coming Soon
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I still can't visualise it; have you any virtual napkins to use for drawings?
If you have an important point to make, don't try to be subtle or clever. Use a pile driver. Hit the point once. Then come back and hit it again. Then hit it a third time - a tremendous whack.
--Winston Churchill
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Imagine putting two hamster wheels side-by-side.
Spin one clockwise, the other anti-clockwise.
A well timed jump could take you from one wheel to the other.
So, now add 50 wheels.
The one at the far end spins fast
Next to it spins one slightly slower
And so on, until the middle, where it doesn't spin.
The *next* one spins slowly in the opposite direction.
then faster and faster until the ends.
Obviously, for docking purposes, it would be best to also have continually slowing rings out toward the ends so we can dock without having to match rotation - but as lonog as we duplicate the situation at each end, but in the opposite direction, then the rotations cancel each other out.
As I mentioned- I have absolutely no idea if this reduces the gyroscope effect at all!
PooperPig - Coming Soon
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I see your point, but this will not solve the prime problem of providing maximal living space. A rigid set of concentric cylindrical shells, all rotating together about their common long axis (same angular velocity for all shells), does so admirably - you can have full Earth gravity at the outer shell, going down as you get closer to the main cylinder's axis.
If you have a non-rigid set of shells (each shell rotating with a different angular velocity), you must have some sort of arrangement to keep the shells rotating smoothly past each other. Moving from one shell to another is much more difficult proposition, and God help the inhabitants if the "ball bearings" seize up...
The rigid set of shells can solve the docking problem very nicely. Docking is always at the axis. Either your spacecraft match rotation with the space station and dock, or there is a counter-rotating docking station at the axis, which (after the spacecraft has undocked) speeds up in order to let the passengers cross into the space station. IIRC, the second choice is the one used by Heinlein, Clarke, and others.
If you have an important point to make, don't try to be subtle or clever. Use a pile driver. Hit the point once. Then come back and hit it again. Then hit it a third time - a tremendous whack.
--Winston Churchill
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I thought "Surely, it is the end of days" and "darkness triumphs in the end". Donning sackcloth and ashes was in order. Deities, whether above or below, would certainly now allow such perversion, such a festering canker, to erupt within universe.
Thank goodness it was a mere April Fools joke.
| "The difference between genius and stupidity is that genius has its limits." - Albert Einstein | | "As far as we know, our computer has never had an undetected error." - Weisert | | "If you are searching for perfection in others, then you seek disappointment. If you are seek perfection in yourself, then you will find failure." - Balboos HaGadol Mar 2010 |
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I'm trying to set a value to the maximum smalldatetime allowed in SQL, yet what's appearing is "6 June 1979". Nothing I do seems to work: ensuring Culture is OK, ensuring I'm passing dates around in a sensible format, ensuring the data I'm setting is the actual date I'm setting.
In the debugger I see _date with a value of "6/06/2079 12:00:00 AM" (see rant below). The date is fine. I pass this into a formatter to turn it into "dd-MMM-yy" format. That works perfectly and the output is correct. This string goes to the user, they hit submit, it comes back and is parsed fine. Everything works perfectly.
Except the date always comes back as 1979.
ARGH. And then I spot it.
15 years too late I've been hit by the Y2K bug.
6/06/2079 12:00:00 AM is 6 Jun 2079 -> "6-Jun-79" which is parsed as 6-Jun-1979.
/more coffee, then better formatting.
As a side note: The American date format (mm/dd/yyyy) is painfully and dangerously ambiguous so given that OS installs are often set with US as the region, surely debuggers should display dates and times as dd-MMM-yyyy or even better, yyyy-mm-dd to account for the Rest Of The World who wants to scream everytime they get an email saying "the date is 4/7/2015".
cheers
Chris Maunder
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The American date format of MM/DD/YYYY is simply idiotic, as is our ridiculous clinging to Imperial measurements, when the metric system makes so much more sense. Why? I believe we Americans are just too lazy to adapt to a new system, despite the fact that it just makes sense to do so!
OK, I have my coat and am long gone! 
How do we preserve the wisdom men will need,
when their violent passions are spent?
- The Lost Horizon
modified 23-Jul-15 7:14am.
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How does the metric system make more sense? It's no less arbitrary and the assumption that people will find the arithmetic less difficult is highly doubtful (shortly after we decimalised currency in the UK I was delayed by several minutes in a shop because the assistant needed to fetch a calculator to work out a 10% discount!) The imperial weights fit particularly well with the quantities of things that people might want to buy - I know exactly what I'm getting in a quarter of mushrooms, an ounce of yeast or a pound of mince and so that's what I continue to ask for despite the EU's attempts to homogenise us all with baffling amounts. Long live the pound, the pint and the mile, I say.
And to return the date. It is of course the departure from the Imperial norm made by Americans (when and why I have yet to discover) that causes all the problems. Who else could come up with a system that takes a unit from its rightful place in between the lower and the higher and sticks it at the front? You don't do mm:hh:ss so why MM:dd:yy Bewildering!
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I believe the US Navy uses dd/MM/yyyy. Of course, the correct usage should be yyyyMMdd. No ambiguity there at all.
Long live Imperial!
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True, and year should be yyyy, not yy only.
The sh*t I complain about
It's like there ain't a cloud in the sky and it's raining out - Eminem
~! Firewall !~
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Neither imperial nor metrics system makes sense. Check the very basic physics for this 
modified 19-Jan-21 21:04pm.
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0x01AA wrote: Check the very basic physics for this
Yup. We should measure speeds in fractions of the speed of light, time as a multiple of a basic physical frequency, and distance at the distance travelled by light in a time unit.
Come to think of it, that's how the meter and second are defined!
If you have an important point to make, don't try to be subtle or clever. Use a pile driver. Hit the point once. Then come back and hit it again. Then hit it a third time - a tremendous whack.
--Winston Churchill
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I lived through the transition from the imperial system to the metric system in South Africa so I do have some experience in both systems. As far as I am concerned there is no choice: Metric is head and shoulders better than imperial!
I also experienced the transition of the monetary system from pounds/shillings/pence to the current metric equivalent in SA and the UK. In SA the transition was overnight. Pounds were withdrawn from circulation in a matter of days. In the UK it took months as they chose to run a dual system for months. Very painful!
Nobody will ever convince me that imperial is better!
How do we preserve the wisdom men will need,
when their violent passions are spent?
- The Lost Horizon
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Cornelius Henning wrote: I lived through the transition from the imperial system to the metric system in South Africa so I do have some experience in both systems. As far as I am concerned there is no choice: Metric is head and shoulders better than imperial!
I likewise lived through the transition in Canada, and agree that metric is better than Imperial or US.
One exception though: the country was surveyed in chains, yards, feet and inches, and changing "travelling" distances to metric was a bad idea. Anything that was in round numbers when surveyed, bought or sold is now in fractional units (meters, hectares, ...) and this is nothing less than a mess.
I'm retired. There's a nap for that...
- Harvey
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