Do you ever have doubts?

Quote from: Ski on July 24, 2012, 11:26:37 AM

Quote from: garygreen on July 24, 2012, 09:12:36 AM

You've said this before, and it isn't true.  I even showed you the calculations astronomers use to construct ephemerides.  Yes, there are some astronomical phenomena that occur in somewhat regular patterns.  There aren't many of those.  There is no pattern I can follow that will help me find Ceres with a telescope on any particular evening.  However, I can use Kepler's equations to tell me exactly (within 25") where in the sky to find it on any date I choose.

I'm not sure if you're being deliberately obtuse or just naive. Man has charted the skies for thousands of years before Newton.

New comets are discovered all the time.  How does one determine when a newly discovered comet will return when that comet has no historical pattern to refer to? 

They don't.

How were the orbital periods of Neptune and Pluto determined when neither has made a full orbit since they were discovered?

They estimated based on its slowness across the sky.

Quote from: markjo on July 24, 2012, 12:04:38 PM

Quote from: Ski on July 24, 2012, 11:26:37 AM

Quote from: garygreen on July 24, 2012, 09:12:36 AM

You've said this before, and it isn't true.  I even showed you the calculations astronomers use to construct ephemerides.  Yes, there are some astronomical phenomena that occur in somewhat regular patterns.  There aren't many of those.  There is no pattern I can follow that will help me find Ceres with a telescope on any particular evening.  However, I can use Kepler's equations to tell me exactly (within 25") where in the sky to find it on any date I choose.

I'm not sure if you're being deliberately obtuse or just naive. Man has charted the skies for thousands of years before Newton.

New comets are discovered all the time.  How does one determine when a newly discovered comet will return when that comet has no historical pattern to refer to? 

They don't.

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How were the orbital periods of Neptune and Pluto determined when neither has made a full orbit since they were discovered?

They estimated based on its slowness across the sky.

[/quote]

Except that the planets change speed as they move across the sky.

It's funny that you think they "estimate based on it's slowness." I've watch Venus move across the sky. It moved very slow. But I was not able to estimate it's orbital period based on that. In fact, at first I wasn't even sure what I was looking at. I had to used a star chart and a planetary skymap or what ever you call it (created with kepler's equations, I believe) to figure out what it was.

Quote from: markjo on July 24, 2012, 12:04:38 PM

Quote from: Ski on July 24, 2012, 11:26:37 AM

Quote from: garygreen on July 24, 2012, 09:12:36 AM

You've said this before, and it isn't true.  I even showed you the calculations astronomers use to construct ephemerides.  Yes, there are some astronomical phenomena that occur in somewhat regular patterns.  There aren't many of those.  There is no pattern I can follow that will help me find Ceres with a telescope on any particular evening.  However, I can use Kepler's equations to tell me exactly (within 25") where in the sky to find it on any date I choose.

I'm not sure if you're being deliberately obtuse or just naive. Man has charted the skies for thousands of years before Newton.

New comets are discovered all the time.  How does one determine when a newly discovered comet will return when that comet has no historical pattern to refer to? 

They don't.

I think that Alan Hale and Thomas Bopp might disagree with you on that.
http://en.wikipedia.org/wiki/Comet_Hale%E2%80%93Bopp

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How were the orbital periods of Neptune and Pluto determined when neither has made a full orbit since they were discovered?

They estimated based on its slowness across the sky.

  I thought that you just said that they don't determine stuff like that.

Markjo, you should know Tom doesn't even pay attention to what he, himself says. I always see him contradict himself, and when someone points it out (as you just did), he further contradicts himself by saying that he didn't contradict himself. Or he'll totally ignore it and say another non-descriptive one-liner.

Thanks ThingingMan, but I've been playing this game with Tom for a few years now.  I usually have a pretty good idea of his response before I even post.

Of course I have doubts. What man in his right mind never encounters doubt. The only people I fear are those who never have doubts, to quote the poet. The ability to doubt is sacred.

As above. To doubt is to think.

I think that Alan Hale and Thomas Bopp might disagree with you on that.
http://en.wikipedia.org/wiki/Comet_Hale%E2%80%93Bopp

If you search for "when will Hale Bopp return?" on Google you will see that estimates range from the year 2900 to 4534, with some sources saying it wont return for 10,000 years. Not exactly an exact science.

  I thought that you just said that they don't determine stuff like that.

I said that they predict future occurrences based on previous occurrences. Looking at a body moving 0.0001 degrees across the sky in a night and predicting that it will move 0.0001 degrees on the next night, and nights thereafter, is a prediction based on past events.

I said that they predict future occurrences based on previous occurrences. Looking at a body moving 0.0001 degrees across the sky in a night and predicting that it will move 0.0001 degrees on the next night, and nights thereafter, is a prediction based on past events.

That's not how it works.  Planets and other objects in our solar system do not move at a constant angular velocity.  Your method will necessarily lead to erroneous results.  Ask the astronomers you supposedly work with.

Find me a single source that supports your claim.  I've provided you with many sources that say the opposite. 

If you search for "when will Hale Bopp return?" on Google you will see that estimates range from the year 2900 to 4534, with some sources saying it wont return for 10,000 years. Not exactly an exact science.

The range is that large for good reason.  Its orbit is enormous, and it's perpendicular to the Sun's equator.  It moves relatively slowly through the Solar System, exposing it to many gravitational perturbations from the planets and Kuiper Belt objects.  It's also not very massive, so we should expect the perturbations to be large.

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I think that Alan Hale and Thomas Bopp might disagree with you on that.
http://en.wikipedia.org/wiki/Comet_Hale%E2%80%93Bopp

If you search for "when will Hale Bopp return?" on Google you will see that estimates range from the year 2900 to 4534, with some sources saying it wont return for 10,000 years. Not exactly an exact science.

Interesting.  I did a quick search and most of the more recent estimates agree on an approximately 2380 year orbital period (for now).  Also, I like how you chose to highlight the 13 year old estimate (from NASA, no less), thereby suggesting that later estimates might not be more accurate.

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  I thought that you just said that they don't determine stuff like that.

I said that they predict future occurrences based on previous occurrences. Looking at a body moving 0.0001 degrees across the sky in a night and predicting that it will move 0.0001 degrees on the next night, and nights thereafter, is a prediction based on past events.

Actually, they observe the movement of bodies compared the background stars over many nights in order to determine orbital characteristics. 

Thanks ThingingMan, but I've been playing this game with Tom for a few years now.  I usually have a pretty good idea of his response before I even post.

Yes, sometimes I don't think very far ahead before I post things like this.