B Energy loss of a photon

kymner
Messages
3
Reaction score
0
TL;DR Summary
Quick question about energy loss of a photon due to its own gravitational field.
I've been told that a photon doesn't lose energy as it travels through a vacuum because it doesn't experience time. However, general relativity states that any energy creates a gravitational field that travels away from the energy at the speed of light. Doesn't this imply that a photon once created should immediately create a gravitational wave that very slightly decreases it's energy changing its gravitational field and creating more gravitational waves causing it to very lose all of its energy over astronomically large distances? Since the gravitational field expands out to infinity shouldn't the energy lost be perpetual so that it continues losing energy forever until it ceases to exist? Wouldn't this explain the apparent expansion of the universe without actually requiring expansion?
 
  • Skeptical
Likes PeroK
Physics news on Phys.org
kymner said:
I've been told that a photon doesn't lose energy as it travels through a vacuum because it doesn't experience time…. general relativity states that any energy creates a gravitational field that travels away from the energy at the speed of light.
Whoever told you these things, either they’re wrong or you misunderstood them.
(It is true that light doesn’t lose energy as it travels through a vacuum, but that isn’t because it “doesn’t experience time”).

As this thread is based on a mistaken premise, it is closed.
 
I started reading a National Geographic article related to the Big Bang. It starts these statements: Gazing up at the stars at night, it’s easy to imagine that space goes on forever. But cosmologists know that the universe actually has limits. First, their best models indicate that space and time had a beginning, a subatomic point called a singularity. This point of intense heat and density rapidly ballooned outward. My first reaction was that this is a layman's approximation to...
In this video I can see a person walking around lines of curvature on a sphere with an arrow strapped to his waist. His task is to keep the arrow pointed in the same direction How does he do this ? Does he use a reference point like the stars? (that only move very slowly) If that is how he keeps the arrow pointing in the same direction, is that equivalent to saying that he orients the arrow wrt the 3d space that the sphere is embedded in? So ,although one refers to intrinsic curvature...
Thread 'Dirac's integral for the energy-momentum of the gravitational field'
See Dirac's brief treatment of the energy-momentum pseudo-tensor in the attached picture. Dirac is presumably integrating eq. (31.2) over the 4D "hypercylinder" defined by ##T_1 \le x^0 \le T_2## and ##\mathbf{|x|} \le R##, where ##R## is sufficiently large to include all the matter-energy fields in the system. Then \begin{align} 0 &= \int_V \left[ ({t_\mu}^\nu + T_\mu^\nu)\sqrt{-g}\, \right]_{,\nu} d^4 x = \int_{\partial V} ({t_\mu}^\nu + T_\mu^\nu)\sqrt{-g} \, dS_\nu \nonumber\\ &= \left(...
Back
Top