From: PointedEars@web.de   
      
   Ross Finlayson wrote:   
   > On 02/11/2026 05:43 PM, Thomas 'PointedEars' Lahn wrote:   
   >> The energy dispersion relation for a photon is E = ℏ ω(K), and one finds   
   >> ω(K) = k c, so E = ℏ k c = ℎ/(2π) (2π/λ) c = (ℎ/λ) c.  But   
   >>   
   >>    p = ℎ/λ,   
   >>   
   >> so for a photon   
   >>   
   >>    E = p c.   
   >>   
   >> The energy-momentum relation for a free particle in Minkowski space is   
   >>   
   >>    E^2 = m^2 c^4 + p^2 c^2  <==>  m = 1/c √(E^2 - p^2 c^2)   
   >>   
   >> so   
   >>   
   >>    E = p c  ==>  m = 0. ∎   
   >   
   > [pseudo-scientific babbling]>   
   > Solar sails work. If one suggests that it's "ionic wind"   
   > others have that it's light plainly.   
      
   Solar sails work, NOT because photons have non-zero mass, but because they   
   have non-zero _linear momentum_ *even though* they have non-zero mass, as   
   I just showed.   
      
   The total linear momentum is conserved thus (assuming no absorption)   
      
     P_spacecraft = n P_gamma' + P_spacecraft',   
      
   where   
      
     P_spacecraft = m_spacecraft * V_spacecraft = m * 0 = 0   
     P_gamma' = -n (h/lambda) cos(alpha) P_gamma/p_gamma   
     P_spacecraft' = m V_spacecraft',   
      
   where n is the number of photons, lambda is the wavelenghth, and alpha is   
   the photons' angle of incidence to the surface of the spacecraft.   
      
   One can see that the larger the area where photons can "impact", and the   
   smaller the mass of the spacecraft, the greater the speed that can be   
   achieved.  Therefore, solar sails are huge while the spacecraft propelled by   
   them are usually small (satellites).   
      
   > Actually, a photon follows about _half_ the curvature of   
   > spacetime,   
      
   No, you are confusing facts.  The "half" comes from that the angle of   
   deflection of light as observed, and as predicted by general relativity, is   
   only half of the angle as predicted by Newtonian mechanics *if* one assumes   
   that a photon has a non-zero mass that is equivalent to its energy.   
      
   This falsifies both Newtonian mechanics and the idea that photons have   
   non-zero energy.   
      
   > which was enough to improve the computation of the precession of Mercury.   
      
   This has nothing to do with that, but pertains to Einstein's prediction of   
   1916, and Eddington's confirmation by observations during the total solar   
   eclipse of 1919, of the deflection of starlight when it passes close to Sol:   
      
      
      
   Einstein predicted the _perihelion_ precession of Mercury correctly in 1915   
   already.  It had been observed by Le Verrier before, but could not be   
   explained using Newton's theory of gravitation (there was no planet Vulcan   
   that orbited closer to Sol than Mercury):   
      
      
      
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   PointedEars   
      
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