how many candles would it take to be as bright as the sun?

Answer 1

Brightness or luminosity is measured in candela which is a modern version of the old unit candlepower which was based of the lumionosity of a standard candle.
As candlepower and candela are roughly equal and as the luminosity of the sun is 400 billion candela (Viewed from the earth), this means we would need 400 billion standard candles.

(Additonal) Errr... I supect my maths and my original data is sumewhat suspect

Answer 2

You need to measure the luminosity of the candle in Watts (or look up, on Google, say, the luminosity of an average candle - don't look up 'standard candle', that's a different thing entirely). The luminosity of the Sun is about 3*10^26 Watts. Divide this by the luminosity of the candle and this is how much (intrinsically brighter) the Sun is than a candle. It is therefore how many candles you would need to place at the distance of the Sun in order for them to be as bright.

(Added) To try to remove confusion. In astronomy, luminosity is measured in Watts. In Physics, it is as in the answer above.

Good luck! I couldn't find a value for the luminosity of a candle :)

(Another addition) On Dr GH's calculation, which I'm sure is right, each square meter of the Sun's surface is about as bright as 15 million candles. Just thought you'd like to know.

Answer 3

OK... concentrate...

In terms of the brightness of the light falling onto the earth from the sun, per square meter, sunlight is about 100,000 lux.

A common candle emits roughly 1 candela.

How do you convert candelas to lux? Carefully. Try and follow this bit:

An isotropic one-candela light source emits a total luminous flux of exactly 4π lumens.

One lux is equal to one lumen per square metre, so if you concentrate all the light from a candle onto 1 square meter of ground, you'll get: 4π lux which is about 12.57 lux.

OK. Now we've got some numbers to work with, in the same units.

How many candels do we need to focus on 1 square meter of ground to be as bright as sunlight on that 1 square meter of ground?

100,000 lux divided by 12.57 lux...
7958 candles.

So you'd need a pretty big reflector dish to concentrate that much candle light.

Now that's 1 square meter.. what about the whole light output from the sun?

The sun is 149.6×10^6 km away..
The surface area of a sphere of radius r is A = 4πr²

The earth sits in a sphere of that radius, so the sunlight falling on the earth is 1 part in 2.81x10^17 parts.

Which means you'll need that many times more candles.. a total of
2.24 x 10^21 candels.

A million is 10^6.. so we're talking...

a few hundred thousand million million million candles.

Roughly.

froggie

Answer 4

The LUX is the SI unit of brightness that is weighted based on the amount of area the light covers and which wavelengths are more perceptible by people. It is a good measure of what looks brighter than what. So here is a chart of lux intensities:

lux............example

0.00005.....Starlight
1...............Moonlight
10.............Candle one foot away
400...........A brightly lit office
400...........Sunrise or sunset on a clear day.
1000.........Typical TV studio lighting
32000.......Sunlight on an average day (min.)
100000.....Sunlight on an average day (max.)

So, assuming that you could cram that many candles into a small space one foot away from you, it would take between 3,200 and 100,000 candles to simulate an AVERAGE day. And much more for bright days!

Hope that helps!

Answer 5

An inummerable number, just as the stars in the sky or the sand of the Sea.

Answer 6

never enough candles in the world to outshine our lovely sun

Answer 7

googol

10^100 (a 1 followed by one-hundred zeros)

Answer 8

It would be millions. That is a longs way away.

Answer 9

very much, but less then infinity (because infinitiy is VERY big) ... look at hitchhicker's guide to galaxy for the explanation.

Answer 10

a million trillion x billion