A Space & astronomy forum. SpaceBanter.com

Go Back   Home » SpaceBanter.com forum » Astronomy and Astrophysics » Astronomy Misc
Site Map Home Authors List Search Today's Posts Mark Forums Read Web Partners

GRAVITATIONAL REDSHIFT DUE TO LOWER SPEED OF LIGHT



 
 
Thread Tools Display Modes
  #1  
Old April 8th 13, 07:18 AM posted to sci.astro
Pentcho Valev
external usenet poster
 
Posts: 8,078
Default GRAVITATIONAL REDSHIFT DUE TO LOWER SPEED OF LIGHT

http://www.wired.com/wiredscience/20...in-relativity/
"Galaxy Clusters Back Up Einstein's Theory of Relativity. (...) The researchers, led by Radek Wojtak of the Niels Bohr Institute at the University of Copenhagen, set out to test a classic prediction of general relativity: that light will lose energy as it is escaping a gravitational field. The stronger the field, the greater the energy loss suffered by the light. As a result, photons emitted from the center of a galaxy cluster - a massive object containing thousands of galaxies - should lose more energy than photons coming from the edge of the cluster because gravity is strongest in the center.. (...) The effect is known as gravitational redshifting."

Does "light will lose energy as it is escaping a gravitational field" mean "light will lose SPEED as it is escaping a gravitational field"? In other words, is the gravitationally redshifted light one moving at a speed lower than c? The answer is yes:

http://sethi.lamar.edu/bahrim-cristi...t-lens_PPT.pdf
Dr. Cristian Bahrim: "If we accept the principle of equivalence, we must also accept that light falls in a gravitational field with the same acceleration as material bodies."

http://www.einstein-online.info/spot...t_white_dwarfs
Albert Einstein Institute: "One of the three classical tests for general relativity is the gravitational redshift of light or other forms of electromagnetic radiation. However, in contrast to the other two tests - the gravitational deflection of light and the relativistic perihelion shift -, you do not need general relativity to derive the correct prediction for the gravitational redshift. A combination of Newtonian gravity, a particle theory of light, and the weak equivalence principle (gravitating mass equals inertial mass) suffices. (...) The gravitational redshift was first measured on earth in 1960-65 by Pound, Rebka, and Snider at Harvard University..."

http://courses.physics.illinois.edu/...ctures/l13.pdf
University of Illinois at Urbana-Champaign: "Consider a falling object. ITS SPEED INCREASES AS IT IS FALLING. Hence, if we were to associate a frequency with that object the frequency should increase accordingly as it falls to earth. Because of the equivalence between gravitational and inertial mass, WE SHOULD OBSERVE THE SAME EFFECT FOR LIGHT. So lets shine a light beam from the top of a very tall building. If we can measure the frequency shift as the light beam descends the building, we should be able to discern how gravity affects a falling light beam. This was done by Pound and Rebka in 1960. They shone a light from the top of the Jefferson tower at Harvard and measured the frequency shift. The frequency shift was tiny but in agreement with the theoretical prediction. Consider a light beam that is travelling away from a gravitational field. Its frequency should shift to lower values. This is known as the gravitational red shift of light."

Pentcho Valev
  #2  
Old April 8th 13, 11:24 AM posted to sci.astro
Pentcho Valev
external usenet poster
 
Posts: 8,078
Default GRAVITATIONAL REDSHIFT DUE TO LOWER SPEED OF LIGHT

http://www.youtube.com/watch?v=FJ2SVPahBzg
"The light is perceived to be falling in a gravitational field just like a mechanical object would. (...) The change in speed of light with change in height is dc/dh=g/c."

Integrating dc/dh=g/c gives:

c' = c(1 + gh/c^2)

Equivalently, in gravitation-free space where a rocket of length h accelerates with acceleration g, a light signal emitted by the front end will be perceived by an observer at the back end to have a speed:

c' = c(1 + gh/c^2) = c + v

where v is the speed the observer has at the moment of reception of the light relative to the emitter at the moment of emission. Clearly, the speed of light varies with both the gravitational potential and the speed of the observer, just as predicted by Newton's emission theory of light.

Pentcho Valev
 




Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
GRAVITATIONAL REDSHIFT AND SPEED OF LIGHT Pentcho Valev Astronomy Misc 3 May 12th 12 02:27 PM
GRAVITATIONAL REDSHIFT MEANS DECREASED SPEED OF LIGHT Tonico Astronomy Misc 0 March 30th 12 05:34 AM
EINSTEINIANA: SPEED OF LIGHT IN A GRAVITATIONAL FIELD Pentcho Valev Astronomy Misc 7 December 12th 11 12:09 AM
REDSHIFT LAW, SPEED OF LIGHT, PIONEER ANOMALY Pentcho Valev Astronomy Misc 12 December 28th 08 01:26 PM
VARIABLE SPEED OF LIGHT IN A GRAVITATIONAL FIELD Pentcho Valev Astronomy Misc 30 August 3rd 08 01:10 AM


All times are GMT +1. The time now is 06:10 PM.


Powered by vBulletin® Version 3.6.4
Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Copyright ©2004-2024 SpaceBanter.com.
The comments are property of their posters.