by mgeorge » Fri Oct 21, 2005 8:15 pm
Here are the relevant BELIEFS in astronomy, see for eg.
http://imagine.gsfc.nasa.gov/YBA/HTCas- ... tical.html
http://www.talkorigins.org/faqs/astronomy/distance.html
A. Size:
Size is proportional to distance. This is bedrock theory, not observational bias.
B. Distance
1. Beyond about 26,000 LY (for which parallax methods suffice), the speed of light has been used, as done for supernova SN1987A in LMC which exploded in 1987. "Before the explosion, the star was already surrounded by a ring of dust. This ring began to glow about a year after the supernova explosion, when the light from the explosion reached it. Hence we know that the diameter of the ring is about two light years, and by measuring its angular diameter in the sky, the distance to the supernova was determined to be approximately 169,000 light years. This agrees well with other distance determinations…" [We are not told how they know that it was after 1 year that the ring began to glow].
2. Brightness and colour of stars have been used to measure distances [of up to ??] based on a reference model which includes the concept of absolute brightness. However, stars known [by methods not mentioned] to be too far away for their brightness or too close for their lack of it are classified as giants or dwarves respectively.
3. Helpful "cepheid" stars which show cycles of brightness over 1 to 70 days have been used to measure distances of up to at least 56M LY. The cycle period is said to be proportional to absolute brightness. The changing brightness is said to depend on changing size arising from "gravitational imbalance" [as opposed to being due to a binary or giant planets].
4. Spectral red-shift is said to (a) be proportional to speed and (b) show that the very space between galaxies, except for the closer ones, is expanding at speeds proportional to their distance FROM US. This follows from the Big Bang idea that the universe looks essentially the same everywhere, However, intervening gas clouds cause variations in the red-shift. This expanding universe posits "dark energy" as making up about 95% of universe.
5. Red-shifts of relative motion of PARTS of distant objects have been used to measure distances of up to 6 billion LY.
Here are the relevant BELIEFS in astronomy, see for eg.
http://imagine.gsfc.nasa.gov/YBA/HTCas-size/optical.html
http://www.talkorigins.org/faqs/astronomy/distance.html
A. Size:
Size is proportional to distance. This is bedrock theory, not observational bias.
B. Distance
1. Beyond about 26,000 LY (for which parallax methods suffice), the speed of light has been used, as done for supernova SN1987A in LMC which exploded in 1987. "Before the explosion, the star was already surrounded by a ring of dust. This ring began to glow about a year after the supernova explosion, when the light from the explosion reached it. Hence we know that the diameter of the ring is about two light years, and by measuring its angular diameter in the sky, the distance to the supernova was determined to be approximately 169,000 light years. This agrees well with other distance determinations…" [We are not told how they know that it was after 1 year that the ring began to glow].
2. Brightness and colour of stars have been used to measure distances [of up to ??] based on a reference model which includes the concept of absolute brightness. However, stars known [by methods not mentioned] to be too far away for their brightness or too close for their lack of it are classified as giants or dwarves respectively.
3. Helpful "cepheid" stars which show cycles of brightness over 1 to 70 days have been used to measure distances of up to at least 56M LY. The cycle period is said to be proportional to absolute brightness. The changing brightness is said to depend on changing size arising from "gravitational imbalance" [as opposed to being due to a binary or giant planets].
4. Spectral red-shift is said to (a) be proportional to speed and (b) show that the very space between galaxies, except for the closer ones, is expanding at speeds proportional to their distance FROM US. This follows from the Big Bang idea that the universe looks essentially the same everywhere, However, intervening gas clouds cause variations in the red-shift. This expanding universe posits "dark energy" as making up about 95% of universe.
5. Red-shifts of relative motion of PARTS of distant objects have been used to measure distances of up to 6 billion LY.