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| Thread: Supernatural, Paranormal, or ... |  This thread is pages long: 1 2 3 4 5 6 7 8 9 10 11 12 · «PREV |
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TheDeath
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posted June 23, 2009 06:47 PM |
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The distance to the Sun can be used as a multiplier to the distance to Mars. We weren't talking about distant stars, but about the Sun.
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JollyJoker
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posted June 23, 2009 06:58 PM |
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JJ:Quote:
Triangulation, as a mathematic method has indeed been known to the Egyptians. Since the beginning of the 17th century it has been used for chart-making. But to use it to determine distance to far away stars you need two things:
1) A correct model of the universe. You need to know that the Earth is circling the sun within a year and you need to know the distance earth-sun.
Moreover, that as with Aristarchos you need PRECISE instruments to measure the angles, since due to the large distances milliseconds of degrees are of importance.
So, the first successful distance measurement using parallaxe (the only known way to measure cosmic distances) was made in 1838 by Friedrich Bessel.
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TheDeath
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posted June 23, 2009 07:07 PM |
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Ok let's just drop it. I was talking about parallaxe, because Cassini used parallaxe, not triangulation. I certainly see no common point in our debates, it's like we're arguing about different things. So let's just drop it. 
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JollyJoker
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posted June 23, 2009 07:23 PM |
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Death, did you read the Leavitt part at all?
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In case people are still following me here, Mytical, now comes the point where you may pause: She (and everyone else, mind you) made the assumption now that equal periods mean equal brightness - everywhere in the universe, as far as our telescopes reach. This allowed a COMPARISON of distances, since it is known that Distance = SqRt(brightness factor): If you have two stars with the same absolute brightness and one appears 9 times darker, then it is 3 times as far away.
So far so good, but STILL the problem was that no distance to any pulsar was known.
That assumption isn't correct because not all stars have the same brightness, it would be like saying that all light bulbs have the same brightness (at the same distance) which is incorrect.
What I find interesting here is that
1) you obviously dismiss something generally accepted for nearly 100 years, instead of stopping and thinking, hmm, why is that accepted did I misread or misunderstand something?, and
2) you don't realize that the assumption I mean is that the thing you deem to be incorrect is assumed to be valid EVERYWHERE IN THE UNIVERSE which means that you missed the part that had some significance for the point Mytical made (which is the reason why I explicitely addreassed her), which goes a long way to show your interest for the actual topic.
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JollyJoker
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posted June 23, 2009 07:40 PM |
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Quote:
Ok let's just drop it. I was talking about parallaxe, because Cassini used parallaxe, not triangulation. I certainly see no common point in our debates, it's like we're arguing about different things. So let's just drop it.
Umm, parallax is a special form of triangulation.
But, yeah, was the one who took triangulation into space I guess.
Still, the trouble was the precision in measuring to make use of it.
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TheDeath
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posted June 23, 2009 07:42 PM |
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Edited by TheDeath at 19:44, 23 Jun 2009.
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Quote:
What I find interesting here is that
1) you obviously dismiss something generally accepted for nearly 100 years, instead of stopping and thinking, hmm, why is that accepted did I misread or misunderstand something?, and
2) you don't realize that the assumption I mean is that the thing you deem to be incorrect is assumed to be valid EVERYWHERE IN THE UNIVERSE which means that you missed the part that had some significance for the point Mytical made (which is the reason why I explicitely addreassed her), which goes a long way to show your interest for the actual topic.
I really don't care how much this assumption survived, for 100 years or 1000 years. It still is an assumption (likely to be incorrect, might I add) unless I'm missing some data or something (which I didn't see).
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Umm, parallax is a special form of triangulation.
Everything is a special form of mathematics
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JollyJoker
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posted June 23, 2009 10:00 PM |
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That's really sad. I mean, it's really sad that you don't see the genius of that woman. That's why I'll try to explain it again.
At that time people had discovered an endless number of stars, but NO way of determining the distances of all those nebulas. You have to consider that 100 years ago the universe wasn't as big as now. In fact there were two "directions", one, that all those fancy nebulas they saw with their scopes were all part of the milky way, and two, that those nebulas were separate galaxies like the milky way...
A pulsar is a star that changes its brightness PERIODICALLY. If you watch it continually the brightness will change in a characteristic pattern and that pattern will take a certain time. If you'll make a foto every 12 hours you'll get a certain brightness each time. This will add up to a series of values, and this series of values will repeat itself AFTER A CERTAIN TIME. So the bringhtness values of a star may look like (shortened)
12, 11.5, 11, 11, 11, 10.5, 10.5, 11, 11.5, 12, 12, 11.5...
another one may look like
10, 9, 9, 9, 8.5, 9,5 10, 9, 9, 9...
Now. What Leavitt did, was she studied intensively fotos of the Small Magellan Nebula, and compared them. She did that because that small nebula and the stars in it were easily identifiable as being part of that nebula. So she endlessly compared fotos of it that were made at different times and found at last 25 pulsars. Her assumption was, that this nebula would be pretty far away, but that those pulsars would be more or less equally distant to earth compared to the distance to Earth. Which had to mean that relatively brighter meant absolutely brighter in comparison of those.
Then she compared the pulsating PATTERN with brightness and found that there was a simple relation: the brighter the star the longer the period of the pattern.
Note that this assumption was cool: Let's say a nebula is 100.000 lightyears away, and 10.000 lightyears thick. That means, the difference between two of those stars in there is at most 10.000 lightyears. There isn't much difference in brightness whether an object is away 100.000 or 110.000 LYs (the factor would be 1.21: 1.1x1.1).
Anyway, this meant that you could just look at PERIODS of pulsars. If a pulsar had a loooong period and low brightness it mant that it had to be faaaar away, since it was a bright star in an absolute sense. And so on.
The assumption relevant for this thread is, that this relation between brightness and pulsating period would be the same everywhere in the universe.
It's really a shame that ou don't have more interest - this is one of the really great achievements of astronomy.
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TheDeath
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posted June 24, 2009 12:16 AM |
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Quote:
Note that this assumption was cool
Being cool isn't a substitute for data. All data out there is that pulsars have patterns. That's it. Since you don't know the distance in the first place you can only make guesses that they are all neighbors or whatever, or that ALL of them exhibit the same behavior.
My question was is this "fact" of pulsars based on any other data than just a guess/assumption that pulsars even exist based on just observations of a star changing brightness in a pattern? The patterns are there, how are you sure that brighter stars "in an absolute sense" have longer periods? Because their patterns have a maximum brightness? I mean here comes her second assumption: that they were all basically near each other compared to the distance to the Earth. What leads that to represent the star's actual brightness? How was she even sure that all pulsars would exhibit same behavior (with pattern vs brightness relationship)?
Some people say that there aren't enough evidence for black holes. I think this tops even those. Just my opinion, which I also think, is off topic
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JollyJoker
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posted June 24, 2009 08:04 AM |
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*sigh*
It seems you have no sense for the beauty of really intelligent ideas and assumptions, especially when linked with tons of work to get the empirical data to make something of it.
If you see a group of birds rising from out of a stand of trees, not only it makes sense to assume that they are a flock and near each other, you can assume as well, that if some of them are looking much bigger than others, that they are bigger indeed. If you had the idea now to film their flight, then watch it in slomo and check how fast their wings beat and you would get this results:
size 1 2 3 4 5 6 7 8 9 10
beats/min 8 15 25 31 39 48 56 63 72 79
you'd have a very clear hypothesis about a simple relation between size and wing beats (strange birds, I admit, but good example). In this case you can just count wing beats and deduct size. All you are missing is one ACTUAL size, like, we saw a bird sitting on my fence and could measure its wing span and body lenth from our house; when it flew away we counted 24 wing beats/second.
This is a very simple article:
http://en.wikipedia.org/wiki/Cepheid_variable
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Mytical
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posted June 24, 2009 08:23 AM |
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Ok somebody want to simplify for the layman who read this what the HECK you two are talking about...and why?!
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JollyJoker
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posted June 24, 2009 03:47 PM |
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You brought distances into the equation, and I explained, how it is possible to determine how distant very far away objects like other galaxies really are. While the bird example is obviously wrong for birds (at least I wouldn't know about a simple relation between size and wingbeats per minute, it serves well as a model to understand how it works with the pulsars.
Oh, and of course Death thinks that this method is wrong somehow or incorrect or based on wrong assumptions or whatever, and I've tried - in vain, it seems, to explain it to him.
I mean, think about it: how would you know how far away a nebula is that you watch through a strong telescope?
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TheDeath
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posted June 24, 2009 05:17 PM |
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Edited by TheDeath at 17:18, 24 Jun 2009.
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Hey I didn't say that it is incorrect, I said that it is an assumption. And the biggest one would be that these pulses are constant for ALL pulsars.
Is there ANY explanation as to WHY the pulse happens and exactly why in that pattern? For instance, exactly why do brighter stars have longer periods, and is there any equation that can describe this based on star composition or whatever? (please link if it is, it would be nice to know, but I haven't seen in this thread). You can't even analyze objects so far away so it is a BIG assumption. Much like the redshifts representing expansion when it could be something else entirely. Just assumption because, you know, doppler effect happens here on Earth...
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JollyJoker
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posted June 24, 2009 05:21 PM |
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Just follow the Cepheides-link I gave two posts above, and work yourself onwards from then on. Yes, the phenomenon has been explored and explained.
About what you said:
Quote:
That assumption isn't correct because not all stars have the same brightness, it would be like saying that all light bulbs have the same brightness (at the same distance) which is incorrect.
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Mytical
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posted June 27, 2009 01:18 PM |
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Ok now that the science lessons have settled down...maybe we can get back on track.
ESP - The ability to see into the future. Conmen and Gypsies have long claimed to have this ability, but use generalizations and tell people what they want to hear. However, does honest to goodness precognition exsist? Your thoughts on the matter, and under what circumstances you would think it exsists if you think it doesn't.
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