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Are gravity (and star-system) simulators worth the $$$?

  1. May 19, 2012 #1
    As a writer, this is important for me to know, since if they aren't worth the money to purchase (and many of them are indeed for-pay, rather than Open Source), I need to avoid mistakes.

    Currently looking at several programs, some of which I know are likely to be Windows-only. Since I currently use Linux (in the form of Linux Mint 10) rather heavily since it is much easier on my battery, this could be an issue.

    Pity I cannot recall the names of specific ones at this moment :rolleyes: which is highly annoying, but will search my computer for data files saved from various trialware.

    Okay. This is truly annoying. I know I have data stored on this machine from such programs, but no joy on finding the titles ATM.
  2. jcsd
  3. May 19, 2012 #2
  4. May 19, 2012 #3
    Without some idea of planet size (and therefore likely surface area) I could make serious mistakes regarding distances on-planet? And ditto for distances between star systems or planets. Some of the star systems are legitimate (and known!) systems within the Milky Way, so accuracy is highly advised, naturally.

    Would prefer not to run into such show-stoppers during submission and edits of any of my novels, thanks. :smile:
  5. May 19, 2012 #4
    You could just look up distances on the wikipedia (there's probably websites with more, easier to acess information if you look/ask about), I wouldn't say that any of those gravity simulators would be great for either of those tasks.

    If you need to work stuff out yourself you could play about with the 1/r^2 newtons force law to work out what distances should be, if you want help with this part I, or most of the other people here would be happy to help.
  6. May 20, 2012 #5
    What I need, really, is to be able to work out the size of the globes in question, the orbits of the planets, etc.

    One planet in my books, for example, has a gravity of 1.916g, and an orbital period of 1157.407407407 Terran days (which equates to 1000 local days (of 100000 seconds)). Another is a planet more similar to Earth, albeit a bit larger.

    Took me several months of intense work to work out the equations to convert time back and forth, and I am still uncertain of their full accuracy. Since the two major "powers" in the books use very different time systems (total of 3, to be honest) it made it a royal PITA to get all too many of the numbers to match up. Finding, for example, the correct Regellian date for 1980-Jan-01 at exactly 00:00GMT took more than a little work, even though the Regellian time system's clock is expressed as a large number of seconds.

    Example: 5512:932:6:00:00 is, in fact, 551293260000 seconds from a specific event mentioned indirectly in the books, and correlates roughly to sometime in 2377A.D.

    As it turns out, the odd clocks I see occasionally (that show time according to a so-called metric day, and are thus divided into a 100-division clock-face (10 hours of 100 seconds)) are potentially usable as clocks for my personal reference, but only if I can see the exact time in both systems simultaneously at a glance.

    Anyone assisting my efforts to be correct will, of course, be credited with the help and receive complimentary copies of the books as they are published, unless they explicitly opt-out, which two people already have. This is my goal, and I am sticking to it.
    Last edited: May 20, 2012
  7. May 20, 2012 #6
    Regelis, for example, is a more arid world than Earth (with only 57% water area vs. Earth's 76-78%), while Trekala is probably closer to Earth in both size and general livability. Heck, it is even likely that the star the latter planet orbits is a direct analogue to our own Sun, albeit a very long way away. How far away is a bit daunting, to be honest. LOL

    The speed scale is, at first glance, a duplicate of Trek's, but that would be incorrect, as the speeds go up a lot faster and, in this universe, warpspace can apparently be reached from a velocity lower than Trek's Warp 1. (Trek:Original used Warp^3, while the book series uses a far different scale that places TNG's Warp 9 at about Warp 4 on the novel's chart.) The only two races currently able to go past Warp 4 do so by going into yet another form of hyperspace they call hyperwarp.
  8. May 21, 2012 #7
    First, I assume by 1.916g we mean the gravitational force at the surface of this planet is 1.916 times that of the force on earths surface?
    This means that;

    [itex]\frac{G M_{planet}}{r_{planet}^2} = 1.916 * 9.8 \frac{m}{s^2}[/itex]
    (G = newtons constant)

    This is just newtons 1/r^2 force law. Now we need another piece of information to work out

    We also know that the period is P = 1157.407407407

    The period of an orbit is related to the mass and the 'width' of the orbit by

    [itex]P = 2 \pi \sqrt{\frac{d^3}{G\ M_{body\ being\ orbited}}}[/itex]
    (d = semi major axis aka the farthest the planet gets from the center)(fix'd, ty BobG)

    To get any farther here we need some extra piece of information (we have two equations with three unknowns, mass of the planet, radius of the planet and semi major axis)

    So if you had, say, the average density of the planet we could write mass as a function of radius which would then turn our three unknowns into two and allow us to solve the problem.

    I'd try and help more with the time problem but I'm a little uncertain as to what you're trying to do with it.
    Last edited: May 21, 2012
  9. May 21, 2012 #8


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    For the period of the orbit, the mass is the mass of the star being orbited; not the mass of planet doing the orbiting.

    The latter was the problem faced by astronomers after Kepler's third law and Newton's laws of motion. They knew how long the Earth (and the planets) took to orbit the Sun. You had an equation with three unknowns - a universal gravitational constant that Newton believed was so small no one would ever be able to calculate it, the mass of the Sun, and the distance between the Earth and the Sun.

    But I do agree that a simulator would be little use for what the original poster needs.
  10. May 21, 2012 #9
    Whoops, I didn't work it out myself so I just wiki'd it, I don't really work with newtons laws all that much so I didn't notice my mistake :blushing:
  11. May 24, 2012 #10
    Mass of the planet is discussed in one of the other threads I began. Basically, density is identical enough to Earth's that using that as a baseline works. While this larger planet's water percentage is only (IIRC, must check my resources!) 57% vs 78% for Earth, the ecosystem is very different, especially given the likelihood that the planet is in the near (hotter) side of the Habitable Zone for their star.

    I have been trying to also figure out the star class, based on one item mentioned once in the books; it is mentioned that the light from the star is intensely bright (requiring use of sunglasses!), even though it is toward evening at the time. This is unlike our Sun, but would fit, given the need for the star to be hotter than ours. The one Habitable Zone "calculator" I found was, in the end, useless, since it only had examples for three star-types, not all the known classes. Oops.

    The other planet, Trekala, is in a similar-enough system to the solar system that it is less of a concern; much of its ecosystem is implied to be tropical or sub-tropical and gravity is slightly higher. While it could be that Trekala's star is simply somewhat hotter, I have not mentioned this because I am unsure of myself and don't want to get caught out on using bad astrophysics in my books! Which is why I am relieved to have found this forum, albeit quite late in the game.

    As for the time equations, Regellian time is entirely base-10, while they observe the exact same second (and below) as we do here on Earth. 10 months of 10 weeks of 10 days of 10 hours of 100 minutes of 100 seconds. (1,000 days of 100,000 seconds each) This is in sharp contrast to Earth's 12 months that consist of 52 weeks of 7 days of 24 hours of 60 minutes of 60 seconds (365.2425 calendar days per year). This presented a thorny problem that, fortunately, all but solved itself once I realized I had attacked the problem from the wrong direction. :eek: Almost all of the time equations resolved to fractions that simply flipped to go one way or the other. The problem arises primarily because Terran time has months of variable length, while Regellian months are all a consistent 100 days. Converting Terran time to the day-of-the-year, then that to the month and day does work, but adds a couple of steps to the process.

    Explanation of conversion of minutes (as an example of the complexity):
    Since 3 Regellian minutes = 5 Terran (300 seconds in both cases), it wound up being straightforward, and was the first one to be reduced to equation form. Most of the others forced me to reduce the two periods to number of seconds, then simplify the fraction to the lowest terms that stayed accurate. Since my math skills are somewhat unreliable at times, I used a math-skills learning site to confirm my calculations, most of which were (fortunately!) correct.

    RM=TM*(3/5) while TM=RM*(5/3) The first, assuming 36 Regellian minutes, correctly renders 60 Terran minutes, while the other way returns the proper 36 Regellian minutes.
    Code (Text):
    Hour    TH*(9/25)       RH*(25/9)
    Day TD*(108/125)        RD*(125/108)
    Week    TW*(378/625)        RW*(625/378)
    Above are three more examples (from Appendix A of Capricorn Chronicles, although all the books will have this data), all of which seem consistent. Notice, however, that the numbers are consistently getting larger and more difficult.
    Will not go into the language construction that's still an ongoing project after 10 years, since it has nothing to do with physics, except insofar as words in the language would describe how it works! :rofl:

    (And what any of this has to do with the original question is rather a puzzler, too. :rofl: After all, the programs I am looking at are known quantities, at least in some circles, but I am simply unsure I need to invest nearly $100 in one of them to get things to work the way they ought. I used to have the trialware of the more powerful one, and still have (somewhere!!) the data files it generated for the three planets that are major locales for the books, but since my funds are limited, I am leery of purchasing something that may not do precisely what I need it to do.)
  12. May 24, 2012 #11


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    I hate to cause any new frustration, but if there is interstellar travel involved you would also have to factor in relativistic dilation to your timekeeping system. (That's why Roddenberry took the easy way of inventing "stardates".)
  13. Jun 11, 2012 #12
    In ST:TOS, the stardates weren't even consistent. Wasn't until ST:TNG that stardates were consistent enough to actually be useful for anything. (The "stardate" of a Captain's Log in ST:TOS was actually a random number. This has been confirmed by people who worked on the series (including several of the writers), and by the further fact that the episodes show little to no correlation of stardates to the series' progression.)

    In my books, all the major races (or organisations of races) are very aware of the dilation problem when in Newtonian space. Apparently, in warp-space, slipstream or hyperwarp-space, there is so little dilation that it is trivial.

    Believe me, the issue's been dealt with in the books, although a standard for the "interstellar year" (for use by ships running interstellar distances, with the dilation issues factored in) has not (even in the novels) been determined.

    But again, the use of these programs to map out the star routes (and with the more powerful program, even mapping the planets!) has little to do with the headache of time dilation, and I am trying to figure out whether it is worth my time, money and effort to purchase one of them. LOL
  14. Jun 12, 2012 #13


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    Believe it or not, Roddenberry intended them to be inconsistent and thus let the writers use whatever numbers they pulled out of the air. His (not entirely scientific) reasoning was that since warp travel was a non-linear scale (warp 1=c; warp 6=512 x c), time was meaningless. There was therefore also no linearity to the sequence of events outside of the ship's reference frame.
    Anyhow, sorry about derailing your thread. Back on topic, is there a chance that you could rent time on someone else's simulator, or hire someone who has one to do the calculations for you?
  15. Jul 19, 2012 #14
    Sorry for the longish delay on my reply to this. 5-yr-old in house and I've also been a bit scatterbrained!

    In reference Trek, especially ST:TOS, I fully agree that the Silver Bird of the Galaxy's reasoning was a bit flawed, but then again, he was a cop when he originally wrote out the concept for Star Trek: The Original Series.

    In reference to the rental of time on a scientific-level simulator, the problem really isn't that critical, IMO. I am mainly concerned that with my (very limited!) income, a cost of ~US$58-US$70 for the program and its accessories (even though a once-off cost!) is a bit much for my budget, especially if the program then leads me to have the wrong size for the planets I need to make sure of distances on. <- (Bad grammar in that last? Sure reads funky!)

    Have used AstroSynthesis (by NBOS Software) in the time-limited trial before and discovered its numbers for planet size seemed a bit off, but orbital dynamics seemed spot-on, since (if I messed up distancing!) two of the moons would inevitably collide long before the people I write about get there from gravitational tides causing fatal orbital decay! (Yes, I found the name of one of the programs. The other still escapes me, although it has some form of the word "gravity" in the title!)
  16. Jul 19, 2012 #15


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    That's nobody's fault but your own; a little Superglue and a cork could have prevented that.
    When I'm looking for software, my first stop is always Sourceforge.net. It's all open-source stuff in various stages of development. That's where I got my Inkscape that I use in place of Illustrator, and Gimpshop to replace Photoshop, and NeoOffice rather than MS Office. I prefer the Adobe stuff, but it would have cost me thousands of dollars to buy new versions that would work on my Intel-chipped MacBook. There's a limited amount of stuff available for this machine, and you have to be careful that you're not downloading an Alpha version or worse, but it's all free. If you have any programming skills, you can even help to improve what's there. That having been said, I have no idea as to whether or not they have anything like what you want.
    Last edited: Jul 20, 2012
  17. Jul 20, 2012 #16


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    So Regel orbits its star in a perfectly circular orbit? Or it has no moon, so its 'months' are just arbitrary divisions of the year?

    If you look closely at Earth calendars, there's not the same number of days from the Vernal Equinox to the Autumnal Equinox as there are from the Autumnal Equinox to the Vernal Equinox.

    And each solar day on Earth are different lengths as measured from local Zenith of the Sun to the next local Zenith. 24 hours are just the average length of the solar day.

    Nothing wrong with just setting arbitrary time divisions that have no history behind them, but you are setting up the character of the Regellian race by doing so. A race that uses a time completely divorced from their environment would be an almost naively "pure logic" race - naively, because their logic has resulted in their time becoming an entity in itself with little relevance to the real world they live in.

    That's not to say that humans aren't tempted to do the same. Many people would love to get rid of leap seconds and just let time drift. So what if someday the Sun will rise at 4:15 PM? At least all of our computers have the correct time! (Besides, if we do quit inserting leap seconds, all of us reading this will already be dead before anyone notices it becoming a problem.)
  18. Aug 31, 2012 #17
    Ditto here, although I'm running Linux as well. (Win7 Home Premium was installed on the laptop; I installed (and use extensively) Linux Mint 13.)

    I have heard of (and have on my machine) Inkscape and LibreOffice (which is a fork off the OpenOffice code; fairly mature and VERY stable). As for all things Adobe being overpriced, I agree more than totally. When they took over Syntrillium and voided the licenses granted to those who had Cool Edit 2000 Pro (which became Adobe Audition, but is far less capable, as of the only time I tried to use it) I became very disgusted with Adobe. Instead of Adobe Reader, I use Foxit Reader (does all the same stuff, pretty much, for a much lower price and loads a whole lot faster.) Instead of Audition, I use CE Pro 2000 or Audacity. (the latter is FOSS, but a lot better than Audition was at the time.) Did not know of GIMPshop, although I will certainly look into it; I am fairly well versed in Photoshop, so if it's anything like Photoshop in the workflow, can use it nicely.
    Been looking on Sourceforge for a while now, since one of the programs (in one form) is indeed Open Source, but so far, no joy. Either it was removed from SourceForge for some unknown reason, or was never there to begin with. Ah well. (Hint: Not all open-source software is hosted/stored/echoed/etc. at SourceForge!)
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