what is a lumen (measurement of light)? how do we dictate the "strength" of a beam of light? if light is essentially weightless and moving at an incredible speed, how does it gather or gain strength? originally i had just assumed the difference between light and dark was just photonic dispersion, but we can see supernova from so much further away than we could a red dwarf. Does a supernova just "spit out" more photons to counteract dispersion? or is there a reason why photons from a supernova travel so much further?

(apologies in advance, this is not something i know anything about beyond what i've picked up from basic physics/astronomy classes, figured this would be a fun place to ask)

checked that before i posted, but it doesnt help me measure light from a supernova very well, how many watts do you think that is?

That is exactly it. A single star during a supernova can put out more energy in the form of photons than the rest of the galaxy (more energy in photons than the other 100,000,000,000 stars 'nearby').

A lumen is how we the measure intensity of man made light and Is based on how bright a candle is at 1 meter. I don't think sunlight is even comparable really, like if the Sun in 93 million miles away from earth and Mars is 230 million miles away from the sun - what intensity difference of light would it receive IDK, the answer is probably something we shouldn't even know, GL getting Nasa to ever talk about that number, they must know that number because the Mars Rover is Solar Powered. Fire off a twitter to Neil Degrasse Tyson and see if he'll actually talk about it.

consider the surface area of two spheres. #1 with radius r, #2 with radius α*r

#1 SA = 4*pi*(r)^2
#2 SA = 4*pi*(α*r)^2 = 4*pi*α^2*r^2

So if you are α times closer to the source of the light, you get α^2 as much light per unit area.

Since Mars is about 142 million miles away from the sun, and the Earth is about 93 million miles away from the sun: Mars is 142/93 ≈ 1.5 times as from the sun as the Earth. So someone in orbit around the Earth will see the sun as 1.5 * 1.5 ≈ 2.3 time brighter as someone in orbit around Mars.

i think mars is 142 million miles away from earth, or ~230million miles away from the sun

And instead of the considering the size alone of the sun to determine its quality of light, we could also consider the temperature difference

So even being 230/93 or 2.4 times further away - with avg summer temperatures around the equator at Noon on Mars at 70-80 degrees F while here it is like 100?.

So it must receive ~75% of the light too as well.

Sounds like a nice place to vacation at....

This post was edited by card_sultan on Mar 10 2016 03:06am

the distance from Earth to Mars changes dramatically as a function of time.

Nowhere did I use the size of the sun in that calculation

Temperature is a very complicated matter, and would be an extremely poor choice.

It is about 1.5 times further away.

Again, surface temperature is a function of a grip of variables; so that argument don't work.

Average surface temperature =/= average equator temperature at noon

The area of a disk, more commonly called the area of a circle, of radius r is equal to πr2. Another word for area of disk can be size.

So do you disagree with the guestimate of 75% of the quality of Sunlight?

What number does Nasa use to calculate the energy the solar powered Mars rover can generate?

This post was edited by card_sultan on Mar 10 2016 12:29pm

i forget the number, but we can see a supernova from something like 6 times further away, how is it possible that every photon of a star "bounces" off particulate, while the (majority?) of supernovic (i probably made up that word) photons are capable of travelling magnitudes of order further. If it came down to "luck of the draw" in regards to dispersion, wouldn't stars at the edge of our visible universe sort of flicker in and out of existence (from our perspective)?