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Fiction Writer Looking for Some Astronomy Help

  1. Nov 19, 2007 #1
    Hi There,

    I'm a novelist working on a science fiction adventure, and I could use a little help on the astronomy side. I'm not looking to get down to the inner workings of quantum formulas, but I do want to make sure that I'm at least being reasonably on point given the fact that I can fudge the science to fit the confines of my particular story.

    I have a few questions, if anybody can help me out:

    For arugments sake, let's just say that a manned craft--say like a Star Wars fighter, whatnot--was traveling from Earth and toward the outer edges of the solar system. And let's say speed wasn't a problem.

    * If the craft had traveled 70 million miles from Earth (and away from the sun), at that distance from Earth, would the craft be close enough to Mars for a pilot to see it with his own eyes, or is it still too far away?

    * If he could see it, what would it look like in size, relative to his own? Same thing with Earth.

    * And along those lines, would he be able to see Jupiter from there, or is he too far away? And if he could see Jupiter, what would it look like in size, relative to his own?

    * Also, are there are any good sources or references from Astronauts describing the view from space? What the Earth looks like from up there? What it looks like from the Moon?

  2. jcsd
  3. Nov 19, 2007 #2


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    It depends on where the Sun-Earth-Mars system is at the time. If Mars is at the opposite side of the Sun to the Earth at the time then by flying away from the Sun you make Mars harder to see (further away). If they are on the same side then Mars becomes easier to see (closer).

    Since you can see Mars with the naked eye on Earth, through our atmosphere (which obscures and distorts the light from the stars and planets somewhat) then you can see it from space (where there is no atmosphere in the way) and the closer you get the easier it is to see.

    For your purposes you might want to point out that the ship is flying to Mars at a time when the Earth and Mars are close together, maybe that timing could be important to some other factors in the plot?

    I'm not quite sure what you mean by 'relative to his own?'

    I just did a rough calculation that you would need to be closer than about 8 million miles from Mars for a good human eye to be able to 'resolve' Mars, i.e. to see that it was not just a dot but actually see it have a 'size'.

    Jupiter is much bigger, so you can resolve it with the Human eye from around 160 million miles away (assuming my quick calculation is at all accurate).

    As above, but again you need to realise that the solar system is constantly changing in terms of which planets are near which others. They all rotate with different periods. Let me know if this confuses you and I'm sure I or someone can explain it, or find a useful link.

    I'm guess maybe NASA website might be a good place to start?
  4. Nov 19, 2007 #3
    There is a 3D planetarium software called Starry Night. One of its modes lets you setup 3D animations of the solar system where you the camera is free in 3D. It's not totally simple, but the person who set it up to do the thing you want was a philosopher who doesn't know math or too much astronomy.
  5. Nov 19, 2007 #4
    Cool. Can you provide the exact link for this software? There's a lot of Starry Night references online.

  6. Nov 19, 2007 #5
    Hi Wallace,

    You make very good points, and I should have been clearer in my original post, so I'll try to be more specific here.

    For the purposes of the description I'm working on, let's assume that given their various orbits, the planets are, if not in essentially a straight line starting with the sun and moving away from it, in a staggered pattern reasonably close to a straight line. So, if a ship were to launch from Earth and travel in one straight path, it would ultimately pass (or come reasonably close) to each of the planets in order. Mars, Jupiter, Saturn, etc.

    Now, let's say that, as per your earlier post about needing to be within 8 million miles of Mars to resolve it, the ship is indeed within that range. With Mars 8 million miles in the distance, from the cockpit of a small craft, would it look like the equivalent of a marble, a basketball, a blimp, a small island?

    I'm tryiing to get a sense of how big the planet would look--in contrast to the ship--as seen from that distance (from a certain distance, a small craft and Mars would look essentially the same size).

    Given the same scenario, how close would a ship have to be for a pilot to look at it with his eyes--not on a monitor--and go whoa! That's a freakin' big planet? I'm trying to give a 'from-the-pilot's eye' description. As an example, from a few thousand feet up in an airplane, you can look down at a skyscraper and it seems like a dot. From the ground it's stupendous. I'm looking for the same comparison here.

    Furthermore, what kind of space debris--dust, particles or whatever else is floating around in space--if any, is floating around Mars where a small craft would actually notice?

    Okay, same questions in regard to Jupiter and Saturn.

  7. Nov 19, 2007 #6


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    If you divide your distance to the planet by the planet's diameter (use whatever units you like, as long as you use the same units), it will tell you how many feet you need to stand from a 12-inch globe for it to appear the same size as the planet. You can measure your stride to know how far to walk. Mine is 3 feet. Try it:

    Distance from Earth to Moon: 245,000 miles. Diameter of Moon: 2000 miles
    245,000 miles / 2000 miles, you'd have to stand 122.5 feet from a 12-inch globe so it looks the same size as the Moon from the Earth. With a 3 foot stride, I'd have to take 41 steps away from the globe.

    Diameter of Mars: 6800 km
    8,000,000 km / 6800 km, you'd have to stand 1176 feet from a 12 inch globe so it looks the same size as Mars from 8 million kilometers. This would be similar to placing the 12-inch globe on the putting green of a par-4 golf hole and viewing if from the tee box.

    If you want to do larger distances, you can use something smaller than a globe. But your distance, instead of being feet will simply be ball diameters. So instead of measuring your pace in feet, you'd want to measure how many ball diameters you cover with each step.
  8. Nov 19, 2007 #7
    Here it is, listed for $249


    Some of the features include (wikipedia):

    * Display a realistic night sky, including stars from the USNO A2 catalogue, the Hipparcos Catalogue, the Tycho-2 Catalogue, and the Tully catalogue of galaxies
    * View the night sky from any location on Earth or any position in the solar system, the nearby Milky Way, or the Local Group of galaxies
    * Display any date and time for thousands of years in the past and future
    * Animate time forwards or backwards at any rate
    * Create observing plans
    * Calculate ephemerides of solar system objects
    * Display of current imagery from solar and Earth-observing satellites
    * Generate a Hertzsprung-Russell diagram of the displayed stars
    * Control most popular GOTO telescopes through a serial interface cable
    * Display the sky using an all-sky photographic mosaic created from CCD imagery
  9. Nov 20, 2007 #8
    This is cool. Thanks. Thing is, I'm kinda working with no budget. Is there any scaled down version of this anywhere, that does at least a decent job, that's free?
  10. Nov 20, 2007 #9
    I think I'm generally following you (although you'll have to excuse some of my ignorance; math was never my strong suit).

    As a follow up question, at what point would a small craft get caught up in a planet's orbit? Is there a safe distance where a ship could navigate itself in space without having to worry about being caught in the orbit?
  11. Nov 20, 2007 #10


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    I'm afraid there is no way to answer that question given distance alone. For getting caught in orbit, velocity is just as important as distance, and the two work together to yield the result (wether "yes" or "no"). Because the craft in question is in space, we'll assume that it has escaped Earth Orbit at some time. If that is the case then, unless something happens to slow it down, the craft will not get caught in Mars orbit, no matter how close it gets. Not while travellign at the same speed it needed to escape Earth Orbit.

    Of course slowing the craft down can mean several things in space travel; some of them obvious and others, not so much. If you swing by so close that you brush the upper atmosphere, that would slow you down. Or if you flip around and fire your engines. But, you could also be "slowed down" just by having the right trajectory. It could be possible for the vessel to be travelling at "a very fast speed", according to some observer (standing on Earth, e.g.), and that same observer sees Mars passing by, also at "a very high speed", and yet the vessel and the planet could be almost stationary, compared to each other.
  12. Nov 20, 2007 #11
    Celestia is another good (and free) program that you could use.

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