Why don't we see starlight heading in every other direction?

  • 5 Replies
  • 2723 Views

0 Members and 1 Guest are viewing this topic.

*

Brian Saunders

  • Guest
Brian Saunders asked the Naked Scientists:
   
When we look at a star we are seeing light that has been travelling for some time.

Why then does the light only appear to be coming towards us and not flooding out in every direction. In theory we should be seeing a lot more light which has expanded in every direction from the source point??

What do you think?
« Last Edit: 21/12/2009 18:30:02 by _system »

*

Offline PhysBang

  • Hero Member
  • *****
  • 593
    • View Profile
Why don't we see starlight heading in every other direction?
« Reply #1 on: 21/12/2009 18:48:26 »
We can only detect light that is coming toward us, that's all our detectors can possibly detect. As far as we can tell, light is flooding out in every direction from every light source. In some cases, we can see light from distant sources reflected back at us. I can't remember the exact example, but there is an example of light from a supernova source being reflected off a distant nebula out there somewhere, if I recall correctly.

*

Offline Geezer

  • Neilep Level Member
  • ******
  • 8328
  • "Vive la rÚsistance!"
    • View Profile
Why don't we see starlight heading in every other direction?
« Reply #2 on: 22/12/2009 02:08:26 »
Brian Saunders asked the Naked Scientists:
   
Why then does the light only appear to be coming towards us and not flooding out in every direction.


As PhysBang says, we only see the light that is coming straight at us, but the light actually is flooding out in all directions. It's easy to prove. Look at a star, now start walking while still looking at the star. (Don't walk into anything!) The light from the star does not diminish even though you change your position.
There ain'ta no sanity clause, and there ain'ta no centrifugal force Šther.

*

Offline LeeE

  • Neilep Level Member
  • ******
  • 3382
    • View Profile
    • Spatial
Why don't we see starlight heading in every other direction?
« Reply #3 on: 22/12/2009 23:50:29 »
Brian: get a torch and shine it against a wall.  You'll see the patch of wall light up, but unless you're in a dusty or smoky room, you won't see the light in the gap between the torch and the wall.  The next time it's sunny and with clear air i.e. no mist etc, go outside and see how although the sun lights everything up (otherwise it would be like night time) but you can't see the beams of light from the sun heading towards everything.

The stars in space are just like this; the space between the stars is usually pretty 'clean' in that there's very little dust, so you can't see the 'beams' of light from the stars.

The only time that you can see a 'beam' of light is when at least some of the light is scattered towards you;  when you shine a torch in a dusty or smoky room, some of the light hits the particles of dust or smoke and are scattered towards you and it's only then, as the others have said, that you appear to see the 'beams' of light.
...And its claws are as big as cups, and for some reason it's got a tremendous fear of stamps! And Mrs Doyle was telling me it's got magnets on its tail, so if you're made out of metal it can attach itself to you! And instead of a mouth it's got four arses!

*

Offline Webo

  • Jr. Member
  • **
  • 13
    • View Profile
Why don't we see starlight heading in every other direction?
« Reply #4 on: 25/12/2009 14:53:55 »
I am not sure as of yet science can fully understand light, and its way past me to speculate which theory is closest, however I have as you pointed out that after 13 billion years of stars burning and shinning the night sky should be always bright and not dark, and those that are working on dark matter I believe they think that the dark matter is responsible in part (small or big I don't know) as to why we don't see a lot of light that is generated...great quest my friend       

*

Offline yor_on

  • Naked Science Forum GOD!
  • *******
  • 12188
  • (Ah, yes:) *a table is always good to hide under*
    • View Profile
Why don't we see starlight heading in every other direction?
« Reply #5 on: 26/12/2009 01:21:20 »
yeah, light is weird. It only show itself when interacting with something. You can light a laser in a fog chamber and then you will see the 'beam' but that is because it interacts with all the particles in the fog.

The same done in space will only have a transmitter and the receiver, sort of, with 'nothing' in between.

Which then should mean that what we see as day, is light hitting all those molecules dancing around?
"BOMB DISPOSAL EXPERT. If you see me running, try to keep up."