23 Apr 16
1 edit
Originally posted by sonhousehttp://mentalfloss.com/article/55895/countries-havent-adopted-metric-system
Krist, who uses such outdated units anyway?
Next we need to agree on . vs ,
Were you able to view any of my music links I posts over there?
Some of them. To be honest, I am not a big music fan so I didn't watch them all the way through.
23 Apr 16
1 edit
Originally posted by twhiteheadOk, back to science then🙂
http://mentalfloss.com/article/55895/countries-havent-adopted-metric-system
Next we need to agree on . vs ,
[b]Were you able to view any of my music links I posts over there?
Some of them. To be honest, I am not a big music fan so I didn't watch them all the way through.[/b]
Hey, I am totally with you on Metric units. Americans are stubborn, set in their ways and just want to keep adding 9 and 3/32 to 5 and 14/128ths forever.
Just like the prohibition against marijuana.
Look how well THAT turned out.....
23 Apr 16
Originally posted by sonhouseAnd nothing is stopping them. The secret is to put metric in the education system so the the next generation grows up with it. Most people who deal with the units in their jobs have to learn both systems anyway, and everyone else can continue with the old units till the next generation replaces them.
Hey, I am totally with you on Metric units. Americans are stubborn, set in their ways and just want to keep adding 9 and 3/32 to 5 and 14/128ths forever.
23 Apr 16
Originally posted by twhiteheadThe thing is that which units I use tends to be a function of what I'm looking at. For science I'll use natural units (c = h = k = 1), for an engineering problem (if I were to look at one) I'd use SI, for computation I'd use abstract units (as is standard), and for every day stuff like cooking I'll use pounds and ounces.
And nothing is stopping them. The secret is to put metric in the education system so the the next generation grows up with it. Most people who deal with the units in their jobs have to learn both systems anyway, and everyone else can continue with the old units till the next generation replaces them.
I have the Wikipedia page for light year open as I wanted the conversion to Astronomical Units and noticed something. Entertainingly it's defined in terms of the Julian year (365.25 days) as opposed to the Gregorian year (365.2425 days), this system was adopted in 1984 long after anyone continued to use the Julian calendar...
23 Apr 16
Originally posted by DeepThoughtWell I grew up with and use the metric system in daily life. Even for cooking, the food is marked in grams and litres. My parents were comfortable with both. Most kids wouldn't even know what you were talking about if it wasn't metric.
The thing is that which units I use tends to be a function of what I'm looking at. For science I'll use natural units (c = h = k = 1), for an engineering problem (if I were to look at one) I'd use SI, for computation I'd use abstract units (as is standard), and for every day stuff like cooking I'll use pounds and ounces.
23 Apr 16
Originally posted by twhiteheadJust noticed this - the posts were coming thick and fast earlier - I'll check your spreadsheet.
Please refrain from using different units all the time lets stick to a particular unit, in this case W/m^2
My figure is based on DeepThoughts origional post where he says that Sirius:
At 1AU the radiance is 1,368 W/m^2
I then use the inverse square law and the distance between the sun and Sirius.
I think I have the distance from Sirius to the sun in ...[text shortened]... e 800 Kilowatts/M^2.
One step at a time. If my first figure is wrong, the rest will be too.[/b]
23 Apr 16
Originally posted by twhiteheadRight I've found three problems. The first is in box B14, you have a typo and are using tanh rather than tan - this makes no difference numerically because of the small value.
Please refrain from using different units all the time lets stick to a particular unit, in this case W/m^2
My figure is based on DeepThoughts origional post where he says that Sirius:
At 1AU the radiance is 1,368 W/m^2
I then use the inverse square law and the distance between the sun and Sirius.
I think I have the distance from Sirius to the sun in ...[text shortened]... e 800 Kilowatts/M^2.
One step at a time. If my first figure is wrong, the rest will be too.[/b]
In boxes B29 and B30 you are dividing where you should be multiplying - although the ratio comes out right anyway (as you're doing the wrong operation with the same number so the error cancels).
23 Apr 16
1 edit
Originally posted by DeepThoughtNot a typo. I am working out an angle.
Right I've found three problems. The first is in box B14, you have a typo and are using tanh rather than tan - this makes no difference numerically because of the small value.
In boxes B29 and B30 you are dividing where you should be multiplying - although the ratio comes out right anyway (as you're doing the wrong operation with the same number so the error cancels).
OK, so we now agree, a ratio of about 17,000
Next I will work out the slightly further out point where there should be approximately double the radiation.
And then I will think about which figures would be fun to put in a program.
23 Apr 16
Originally posted by twhiteheadWe've already got that, it's the 117 km figure (for a 1 m radius collector disk). The reason for this is that the top of our current annulus will be the centre of the annulus for the point where the amount of radiation is doubled relative to the first focus.
Not a typo. I am working out an angle.
[b]In boxes B29 and B30 you are dividing where you should be multiplying - although the ratio comes out right anyway (as you're doing the wrong operation with the same number so the error cancels).
OK, so we now agree, a ratio of about 17,000
Next I will work out the slightly further out point where there ...[text shortened]... le the radiation.
And then I will think about which figures would be fun to put in a program.[/b]
23 Apr 16
Originally posted by DeepThoughtWhat is the ration 17,000?
We've already got that, it's the 117 km figure (for a 1 m radius collector disk). The reason for this is that the top of our current annulus will be the centre of the annulus for the point where the amount of radiation is doubled relative to the first focus.
23 Apr 16
3 edits
Originally posted by DeepThoughtSo you are saying 0.005 watts / meter squared from sol vs 81 watts at first focus?
Light from Sirius hitting the collector disk divided by light from the Sun hitting the collector disk at the point of first focus.
if Sirius puts out 25X sol, that would amount to about 33,000 watts per meter squared at 1 AU. Sirius is about 529,000 AU from Sol. That is a factor down about 3.5E-12 and that times 33,000 is about 511 watts per square meter at first focus, where there is about 4.3E9 meters available around the disc of the sun to focus at 542 AU. 33,000 (1 AU) times 3.5E12 = 1.1E-7 Watts/M^2 at sol times 4.3E9 and I get about 500 watts concentrated at 542 AU.
It also seems to be at the other end, the power goes to 15,000 watts/M^2 suspiciously close to half the number at 1 AU (33,000 watts/m^2)
You want to go over these figures?
24 Apr 16
1 edit
Originally posted by sonhouseYes, the power ratio at the collector - focused radiance from Sirius divided by unfocused direct radiance from the Sun.
So you are saying 0.005 watts / meter squared from sol vs 81 watts at first focus?
if Sirius puts out 25X sol, that would amount to about 33,000 watts per meter squared at 1 AU. Sirius is about 529,000 AU from Sol. That is a factor down about 3.5E-12 and that times 33,000 is about 511 watts per square meter at first focus, where there is about 4.3E9 mete ...[text shortened]... iciously close to half the number at 1 AU (33,000 watts/m^2)
You want to go over these figures?
You seem to be out by a factor of two for the power from Sirius at the point of first focus - the annulus is 1/2 a metre wide for the first focus which I'm guessing is what the problem there is (for a focus point more than 117 km further out on a 1m radius collector that would go up to 1 m wide, see earlier in the thread).
I don't understand what you mean by "at the other end" - are you talking about the equivalent effect of light from the Sun being focused by Sirius?