ok - I have not been studying astrophysics in any real sense but I have been an amateur enthusiast for ten years or more.

I have a burning question :

Our measurements of Universal bodies (stars, nebulae etc) comes from the measurements we have learned to make with our knowledge of Electromagnetic radiation here on earth and in the surrounding solar system. Now we revolve around our Sun with a discernable regularity - the Sun is our fixed point for measurement of this.

But our measurements into the Universe cannot be based on the same calculations as
1) we dont know whether Electromagnetic radiation behaves the same around other, much different celestial bodies (eg does the speed of light in space change in proximity of a black hole) and
2) we dont have a fixed point anywhere in the Universe to base our measurements from.

If the Sun is moving through the Universe and all the other things we are looking at are moving, we dont know what direction or speed they are moving (vector geometry without a fixed point?) and thus, what distance they are.

Before I try to hypothesise myself into oblivion, can someone tell me why I am wrong (as I think I must be or all Astronomy needs a rethink)?

Thanks.

Paul

Direction and speed have to be computed relative to something.

Distances in space are so vast that the velocities of stars or galaxies are relatively unimportant in the calculation of distance.

Even so, you don't need to know direction and speed in order to determine distance

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We're working on the assumption that we DO know how electromagnetic radiation behaves in all but the rarest and most extreme circumstances, and so far it all presents us with a very consistent model that has successfully predicted many previously unseen phenomena.

Is this proof? No there will never be proof.

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PaulAstro. The science of spectroscopy indicates that the "fingerprint" of colored lines identifying a specific element in a lab on Earth, is identical to the set of lines obtained through a telescope....with some allowance for red and blue shifting due to Doppler effects and gravitational wells. The relative spacing remains the same.
The distance scale is based upon a number of assumptions of standard candles. You might enjoy the link searching for Cepheids in Northwestern's lab...try:http://www.astro.northwestern.edu/labs/m100/


pete

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many thanks to the three of you.

those were 3 quite distinct answers and all contributed to me better understanding the question i was asking. (i read the article on Cepheids also - heavy theory there)

so we can reasonably conclude that our physics of EM radiation is sound, although the possibility of light speed variances still exist, the variances over the distance may be considered negligible.

and we can also determine distance based on the constant of light.

But the mind boggles with the thought that the way the Universe looks now is obsolete. do you think it would be possible to somehow calculate a stars or galaxys vector of travel and compute all that data to produce an actual image of the Universe?

With enough information and computing power you could make a reasonably good guess as to overall appearance, though some of the details would certainly be wrong.

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We need a galactic map like the ones in the Elite/Frontier/First Encounters space games by David Braben. Actually the way its done in those games is pretty cool and easy to understand from a spatial perspective, with the stars on stalks so one can measure the distance relative to the galactic plane.

Surely we have enough knowledge of thousands of stars in our galaxy to begin making such a map?

Yes, there was this set of computer games called Elite/Frontier/First Encounters that had maps like that based off of pretty good data as I recall

If you want more up to date/accurate ones you would just have to get the data from the various surveys and feed it into a program to generate them (or do it manually), though only a relatively small portion of the galaxy has had its distances measured by direct methods (parallax is the main and possibly only one),

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