speed of light measured in mm/s??

[Former user]

Originally reported on Google Code with ID 77

What steps will reproduce the problem?
speed of light 

What is the expected output? What do you see instead?
1. expected 299792.458, got 299792458

What version of the product are you using? On what operating system?
0.8-alpha

Please provide any additional information below.

Reported by [e-mail] on 2007-07-19 06:18:39

[Former user]

``` No it's not the speed of light (that value is ok), it's the light year, that confused me. The ratio light year/speed of light is something near 31000, and that's not the seconds in a year. Obviously, not all constants are in SI units. ```

Reported by `[e-mail]` on 2007-07-19 06:31:10

[Former user]

``` I'm a bit confused about all this. After reading http://en.wikipedia.org/wiki/Light_year I got the idea that there is not an agreement on this. The number of seconds in a year is not clear.

Also, in http://en.wikipedia.org/wiki/SI#Standards_and_conventions : "Astronomical distances measured in astronomical units, parsecs and light-years instead of, say, petametres (a light-year is about 9.461 Pm or about 9 461 000 000 000 000 m)."

So I really don't know what we should do about this. ```

Reported by `helder.pereira.correia` on 2007-07-21 17:34:24

[Former user]

``` The problem is, if you do not stick strictly to a common set of units, and I strongly recommend SI, then you cannot use two constants in a formula without prior conversion. At least you have to check each constant individually. This is not (a) what I expect in the first place, and (b) it is error prone. My initial posting is a good example of what happens in such situations: Without hesitation I used two constants in the same context, assuming this is allowed, and divided them. I was astute enough to see that the result is somewhat weird (but that's not what you can generally expect!!). Confused I made my second mistake (the first was my assumption, that the constants are compatible), and blamed the wrong constant. It finally took some time to sort things out. This is simply not what I expect from a calculator. So, yes, why not define a light year as 9.461e15 m? Regarding the year, a good approximation is the length of the tropical year 1900, that had 31556925.9747 seconds. 50 years ago, this was the basic definition of a second, before atomic standards replaced this. ```

Reported by `[e-mail]` on 2007-07-21 20:11:13

[Former user]

``` ps.: To be precise, because a km is a (derived) SI unit as well, I mean: use SI base units only

Wolf Lammen ```

Reported by `[e-mail]` on 2007-07-21 20:30:10

[Former user]

``` Fixed in branches/0.8. Will be merged into trunk later. ```

Reported by `helder.pereira.correia` on 2007-07-22 00:33:58 - Status changed: `Fixed` - Labels added: Milestone-0.8

[Former user]

Reported by `helder.pereira.correia` on 2007-07-22 22:11:50