On Jun 21, 7:07*am, Pentcho Valev wrote:
http://www.nature.com/news/2010/1006....2010.303.html
NATU "Gravity is mercilessly impartial - on Earth, it accelerates
light and heavy objects alike with a tug of 9.8 metres per second
squared. That property is the cornerstone of Albert Einstein's theory
of general relativity, which states that gravity is indistinguishable
from any other type of acceleration."

Argh! What a poor and sloppy way to put it...

That gravity "accelerates light and heavy objects alike with a tug of
9.8 metres per second squared" is true but this is Newton's emission
theory of light developed by John Michell in the 18th century and
temporarily adopted by Einstein in 1911. If NATURE's editors were both
honest and knowledgeable they would have published the following text:

"Gravity is mercilessly impartial - on Earth, it accelerates light and
heavy objects alike with a tug of 9.8 metres per second squared. That
property is the cornerstone of Newton's emission theory of light; it
is equivalent to the fact that, in the absence of a gravitational
field, the speed of light varies with the speed of the emitter, v, in
accordance with the equation c'=c+v."

They should have cited Einstein instead, according to whom light bends
but does not accelerate while approaching the Earth.

Although in 1911 Einstein was on the right track, in 1915 he spoiled
everything by making light accelerate faster than cannonballs by a
factor of two:

http://www.mathpages.com/rr/s6-01/6-01.htm
[..]

No. And here Kevin Brown explains the factor two much better:

http://www.mathpages.com/home/kmath115/kmath115.htm

Harald