• Question: Why don't stars fully illuminate the sky?

    Asked by crouchingmurloc to Ben, Dave, Ed, Sam, Susana on 17 Jun 2013.
    • Photo: Sam Horrell

      Sam Horrell answered on 17 Jun 2013:

      I’m no expert but I’d say it is probably because they are so far away. The closes star to our solar system is 4.42 light years away from us so it takes that many years for their light to reach us. When we see that star we are effectively seeing a photograph of it 4.42 years ago.

    • Photo: Benjamin Hall

      Benjamin Hall answered on 17 Jun 2013:

      Light is a form of energy, like the food you eat and the fuel you put in the car.

      So to take the food example further… imagine you’re a body builder, like Arnold Schwarzenegger. To fuel your body you need a certain amount of calories. For your average man that’s about 2500 calories a day, for Arnie it’s probably more like 5000-6000 calories a day. If Arnold were to only take in 2500 calories a day he wouln’t have enough food to fill him up.

      So let’s take that back to the stars. Space is an unimaginably vast place. To fill up the night’s sky with light energy you’d need an unimaginably big star!

    • Photo: David Briggs

      David Briggs answered on 17 Jun 2013:

      Because whilst the stars are as bright or in some cases MUCH MUCH brighter than the sun, they are just too far away to make the night sky as bright as the daytime sky.

    • Photo: Susana Teixeira

      Susana Teixeira answered on 17 Jun 2013:

      Not a romantic huh? 😉

      Don’t trust me cause I am not an expert, but I remember reading somewhere that is is because stars have an age, and there isn’t an infinite number of them, so we only see the ones that were “alive” at the right time and distance for their light to reach us when we are looking up to the sky.

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