Telescope Reviews: Re: Is it possible to see the nebula with colour?

This is not a post counter the thesis that colors can be seen in nebulae.

This is a post counter some argumentations that have been produced to support (maybe demonstrate) that thesis.

1) Colors are real because reliable observers have seen them. This sentence does not proof anything (the observers migh all be experiencing a systematic effect). It is like saying that some seashells make sounds the proof being that we can hear the sounds. Another example is this: suppose one have a meter which is actually 1.5 meters long. In the effort to show that the meter is exact he might trace two marks onto a pavement at the beginning and end of the fake meter. Then he might use the *same* meter to measure the distance of the two marking, finding that they are exactly one meter apart. I think the two examples clearly show the short circut. The sentence is irrelevant either for the veridicity or falsity of the the origianal thesis.

2) There are large variations between persons, thus color is visible. There are two mistakes here: the correct sentence might be: "there are large variations between persons, thus color *might* be visible". The fact that there are variations does not necessarily mean that they are *large enough* to reach the effect. An example: "some people run faster than others" does not necesarily mean that some people run 100 meters in 0.1 seconds. The premise "there are large variations between persons" although using the adjective "large" in fact does not mean anything: how large? If we do not specify how large the variations might be we cannot say anything about the performance of the best case. How large are the variations between people? Are there data? Yes, there are. It is the responsibility of who makes the sentence to show how large the variations are (with experimental data) and that they are in fact large enough.

3) A scope large enugh will show colors. This sentence may be either false and true. It is too vague. The correct sentence is (a) "a scope large enough will show colors on those regions that are brighter than cones threshold". This sentence is true. Another sentence might be (b) "whichever the brightness of the nebula there is a diameter which makes the image bright enough to stimulate cones". This sentence is false. Surface brightness cannot be amplified. Thus "A scope large enugh will show colors" is a misleading sentence that suggests that both (a) and (b) might be true, whereas only (a) is true and (b) is false.

Edited by Mauro Da Lio (12/01/07 05:56 PM)

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