If light is shining onto something does it add more weight to that object? Even by a billionth of a gram?

Question: If light is shining onto something does it add more weight to that object? Even by a billionth of a gram?
- Keywords:
  light,
  weight
Asked by tosty55 to Aggelos, Andrew, Eileen, Naomi, Shane on 19 Nov 2012.
- Shane Bergin answered on 19 Nov 2012:
  
  light is made of photons – small elementary particles that are massless. so you could irradiate a sample with an infinite number of photons and it would not get heavier.
  
  Also, if photons had mass, they would not be able to travel at the speed of light (the fastest speed that anything can travel at : 3,000,000,00 meters/second) as they would violate Einstein’s theory of relativity
- Andrew Jackson answered on 19 Nov 2012:
  
  i bow to shane’s far superior knowledge on this! nice answer shane, and a really really great question. I would have guessed it would, and i would have been wrong!
- Eileen Diskin answered on 20 Nov 2012:
  
  SUCH a cool question! And I learned something too 🙂
- Aggelos Zacharopoulos answered on 21 Nov 2012:
  
  @tosty55
  you would not be able to add weight to an object but how about powering a spaceship using something called “solar pressure” generated by the light and high speed ejected gases from star!
  
  So if you are in space you can use a “solar sail” which will capture the solar pressure and allow a spaceship inlimited travel similar to a sailing boat from planet to planet!
  
  Have a look: http://science.nasa.gov/science-news/science-at-nasa/2011/24jan_solarsail/

Comments

Andrew commented on 20 Nov 2012:

im so glad tosty55 asked this and shane answered!

I remembered back to my school days when i saw a device called Crookes Radiometer demonstrated. http://en.wikipedia.org/wiki/Crookes_radiometer . I think i was taught (incorrectly) that the light particles essentially pushed the wheel around which is why i would have guessed that light would give an object extra mass.

Instead, the light heats the dark side more than the shiny side which reflects the light and heat away. This difference in heat creates a very small difference in pressure between the dark and shiny sides, and so the blades rotate – similar to the way a pressure difference above and below a wing lifts the plane into the air (/hydrogenn12-zone/2012/11/14/how-do-planes-stay-up/).

cool.

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tosty55 commented on 22 Nov 2012:

Thanks for taking your time to answer! 🙂

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Question: If light is shining onto something does it add more weight to that object? Even by a billionth of a gram?