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RVHorror
Holy Cardinal and Five Star General of the Righteous Knighthood of Jabootu
USA
532 Posts |
 Posted - 10/13/2005 : 12:14:56 PM
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Got this URL through the usual channels:
http://www.geocities.com/nmdecke/TheMovieList.html
Lots of very good in-depth reviews of (largely) Japanese and Italian SF filmes.
(No, I'm not affiliated. I just enjoy those reviews of Jabootuan length.) |
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nmdecke
Archdeacon of Jabootu
11 Posts |
Posted - 10/14/2005 : 09:03:27 AM
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| Hey, thats me! Thanks for the kind words, not too many people actually admit to reading anything I've written :) nate |
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Greenhornet
Holy Cardinal and Five Star General of the Righteous Knighthood of Jabootu
1791 Posts |
Posted - 10/14/2005 : 4:12:58 PM
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| Now that the followers of Jabootu have learned of your site, you will know no peace! |
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John Nowak
Holy Cardinal and Five Star General of the Righteous Knighthood of Jabootu
USA
1017 Posts |
Posted - 10/14/2005 : 6:46:23 PM
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And, because I am unable to ignore questions -- regarding "Warning From Space."
>Hmmm…I'm not an expert on astral mechanics, but can two bodies really have the same orbit? Wouldn't they have to have EXACTLY TO THE OUNCE the same mass or the sun would pull one of them closer to itself and thus change the orbit?
Yes, two bodies can *theoretically* have exactly the same orbit, and even occupy different parts of that orbit at the same time. The mass of a satellite does not affect the orbit in any way, as long as it's very small compared to the body it orbits around. If you find a moon around a planet, you can calculate the mass of the planet, but not the moon.
>And how would this even happen, how would two planets coalesce from gas and dust way back when in the same orbit but on different sides?
It would probably never happen. The sun, for example, only blocks about half a degree of the sky, so when Earth is at 0 degrees Paira would have to be between 180.25 and 179.75 degrees. The odds against it are ... astronomical.
And unfortunately, even if it did happen, the two planets would never remain so tightly synchronized. Orbits are eliptical, and when a planet is close to the sun it moves faster; when it's further out it moves more slowly. So, we'd see Paira wobbling back and forth in the sky, ducking behind the sun and emerging again.
>And even if Earth were blown to bits, how would that effect Paira? Wouldn't the remains of Earth still be traveling around the sun at the same speed as before, and thus not a danger to Paira on the opposite end of the orbit?
You're right -- blowing Earth to bits could not affect Paira in any way. It's the Achilles Heel of this particular sub-genre of SF Films.
I'm talking about films where aliens come to prevent us primitive Earth screwheads from building nukes or some other overwhelming weapon -- examples include "Day the Earth Stood Still", "Santo vs. the Martian Invasion", "Plan 9 From Outer Space", and "The Incredible She-Creature." Of those, I think only "Plan 9" actually came up with a good reason for the aliens to consider us a threat.
>And couldn't you detect the presence of Paira even if you couldn't see it by the effect it has on the orbits of other planets?
Yes. But if you really wanted to be clever, you could argue that gravity doesn't really work the way we think it does, and that all our equations are based on observations which assumed Paira wasn't there. Of course, the liklihood of that is pretty darn low, but it's fun to think about.
>I hate this movie.
I don't blame you.
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We've always been united in stupidity. That's why there is no hope. But, then again, when has that ever stopped us?
-- hbrennan |
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KurtVon
Holy Cardinal and Five Star General of the Righteous Knighthood of Jabootu
USA
387 Posts |
Posted - 10/14/2005 : 7:51:16 PM
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quote:
Originally posted by John Nowak
The mass of a satellite does not affect the orbit in any way, as long as it's very small compared to the body it orbits around. If you find a moon around a planet, you can calculate the mass of the planet, but not the moon.
Well, that isn't fair. It does have an effect, it's just it has an effect on the orbit of the main body. For example, the Moon does not orbit the Earth, the Earth and the Moon both orbit a point at the center of gravity of the pair. It just so happens that center of gravity is inside the Earth. You canot determine the mass of either body from their orbits, but you can compute the relative mass between the two.
Heck, this is how most extra-solar planets are discovered -- by looking at the wobble of the star. That's why they usually are many time larger than Jupiter.
So it would alter the orbit, but not by much. And it doesn't have the effect people expect. Heck, the Earth is almost a million miles closer to the sun during the northern hemisphere winter than it is for the summer. It just isn't that big a deal.
Oh, and the odds of the other planet in teh same orbit being exactly opposite are one in five. In order to be stable it would have to be at a LaGrange point.
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John Nowak
Holy Cardinal and Five Star General of the Righteous Knighthood of Jabootu
USA
1017 Posts |
Posted - 10/14/2005 : 10:10:45 PM
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quote:
Originally posted by KurtVon
You canot determine the mass of either body from their orbits, but you can compute the relative mass between the two.
quote:
Future observations with the 10-meter Keck II telescope and the Hubble Space Telescope will determine the moon's orbital characteristics, which has an estimated period of about 14 days, and will therefore reveal the precise mass and density of Xena.
http://www.physorg.com/news6914.html
Think I'll go with physorg.com here -- in the equations to calculate the orbital period of a small body, the mass of the satellite is not even a factor. T=2(pi)[a^3/GM]^1/2.
Yes, there is a slight, measurable effect as a small body pulls on a larger one, but that would not have any relevance to the original question, and your statement that you cannot calculate the mass of a primary by observing the orbit of a satellite is simply incorrect. In fact, the weight of the earth was first determined using the orbital data of the Moon.
http://www.juliantrubin.com/bigten/cavendishg.html
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We've always been united in stupidity. That's why there is no hope. But, then again, when has that ever stopped us?
-- hbrennan |
Edited by - John Nowak on 10/14/2005 10:20:43 PM |
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nmdecke
Archdeacon of Jabootu
11 Posts |
Posted - 10/15/2005 : 05:02:29 AM
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| Good god! You are all a bunch of smartyheads here! :) I will contact you whenever i have a science question from now on. I guess if I'm going to keep reviewing sci-fi movies, then I better get my scientific facts straight! Thanks for the thoughts, but I think we are missing the essential point of my review, that Warning From Space's screenplay was written by two gerbils and a five-year old girl... nate |
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thepanteduffin
Diocesan Ecclesiarch of the Sacred Order of Jabootu
Canada
74 Posts |
Posted - 10/15/2005 : 10:30:57 AM
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I've just checked out the site and haven't read any of the reviews yet (but intend to later tonight). Still, I'm with RV Horror with my enjoyment of long, detailed reviews, so thank you and congratulations for the site! Looking very much forward to getting into it!
"You weren't being thick after all - you were showing moral fiber! "
- Ronald Weasley |
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KurtVon
Holy Cardinal and Five Star General of the Righteous Knighthood of Jabootu
USA
387 Posts |
Posted - 10/15/2005 : 3:15:34 PM
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From the "weighing teh Earth" article:
quote:
once G is known the mass of the Earth can be obtained from the 9.8m/s2 gravitational acceleration on the Earth surface
So it was not the moon's orbit that did it, but acceleration at the earth's surface. Of course, because the Moon has 1/18th the mass of the Earth, the mass is not insignificant.
Gabrielle is about 1/465th the mass of Xena (assuming they have the same albedo), which is a little closer to insignificant. From that you can estimate the acceleration of gravity for the planet and therefore estimate the mass of the planet by assuming the mass of Gabrielle is zero.
Despite the article, this is not the definition of precise I would use. Then again, as a mathematician I tend to have a very different view of "precise" than an astophysicist. To them it's precise if the error bars aren't in the exponent.
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Greenhornet
Holy Cardinal and Five Star General of the Righteous Knighthood of Jabootu
1791 Posts |
Posted - 10/15/2005 : 4:02:16 PM
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quote:
Originally posted by nmdecke
Good god! You are all a bunch of smartyheads here! :) I will contact you whenever i have a science question from now on. I guess if I'm going to keep reviewing sci-fi movies, then I better get my scientific facts straight! Thanks for the thoughts, but I think we are missing the essential point of my review, that Warning From Space's screenplay was written by two gerbils and a five-year old girl... nate
I tried to warn you, but would you listen? Noooooo!
"The Queen is testing poisons." CLEOPATRA, 1935 |
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nmdecke
Archdeacon of Jabootu
11 Posts |
Posted - 10/15/2005 : 5:15:46 PM
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| I have learned my lesson... I am humbled. |
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John Nowak
Holy Cardinal and Five Star General of the Righteous Knighthood of Jabootu
USA
1017 Posts |
Posted - 10/16/2005 : 12:28:22 AM
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quote:
Originally posted by KurtVon
From the "weighing teh Earth" article:
You did not cite your quote correctly. The actual quote is
quote:
...once G is known the mass of the Earth can be obtained from the 9.8m/s2 gravitational acceleration on the Earth surface and the Sun's mass can be obtained from the size and period of the Earth orbit around the sun.
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We've always been united in stupidity. That's why there is no hope. But, then again, when has that ever stopped us?
-- hbrennan |
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KurtVon
Holy Cardinal and Five Star General of the Righteous Knighthood of Jabootu
USA
387 Posts |
Posted - 10/17/2005 : 8:01:54 PM
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Okay, let's try this again (#%$^ full forum).
Yes, you can calculate the mass of the Sun exactly once you know the mass of the Earth. Or you can calculate the mass of the Sun faily well by assuming the Earth has zero mass (actual ratio is about 333,000:1).
You are making me regret my pedantry in my first post.
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Edited by - KurtVon on 10/18/2005 09:46:09 AM |
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nmdecke
Archdeacon of Jabootu
11 Posts |
Posted - 10/18/2005 : 08:30:33 AM
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| Before Kurt and John kill each other with their sliderules, I just wanted to say thanks to everyone. I've met some really nice people and i've had more hits on my site in the last 4 days than in the previous 12 months (seriously!). I have taken the liberty of sacrificing my first born child to Jabootu... I hope he is pleased. |
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twitterpate
Holy Cardinal and Five Star General of the Righteous Knighthood of Jabootu
Canada
1026 Posts |
Posted - 10/18/2005 : 09:14:31 AM
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| Well, he WOULD have been happier if you'd sacrificed Steven Seagal... |
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KurtVon
Holy Cardinal and Five Star General of the Righteous Knighthood of Jabootu
USA
387 Posts |
Posted - 10/18/2005 : 09:45:28 AM
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quote:
Originally posted by twitterpate
Well, he WOULD have been happier if you'd sacrificed Steven Seagal...
No, that would have made everyone happier.
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