Re: Can you propel a spacecraft by turning light into matter?

Yes you can!

But light is not very heavy - so you need a lot of it.

If I emit a thousand megawatts of power in the form of a beam of light, 
you can CALCULATE the force from the equation:
 force by distance/second = watts.
Here distance per second is 300,000,000 metres/sec and the force is 
newtons.

To get a bit closer to your question "Is light matter" then "photons" 
certainly ARE matter, and carry momentum - so much for each photon.
And if you do it THAT way you get EXACTLY the same force as from the 
watts!

So on THIS occasion, quantum mechanics told us nothing we did not know 
already.

John