Question regarding red shift and tired light hypothesis

  • Thread starter rrosenthal
  • Start date
  • #1
16
0

Main Question or Discussion Point

The idea that distant objects are receeding from us and thereby producing a proportional redshift --seems to be a fundamental tenant in terms of current cosmological thinking and theory. There have been alternate ideas proposed in the past including the tired light hypothesis-(whereby light traveling at great distances gives up energy to space and that this is what produces the red shift---still proportional to distance). If very distant objects are in fact receeding from us, they ought to be growing fainter in magnitude. Has this ever been measured ?? I wonder if the magnitude of distant objects on plates taken 20-30 years ago have ever been compared to present day magnitude of the same objects---to see-- if on average-- they have become slightly fainter. I wonder if our instruments are sensitive enough to make such a determination ???

Randy Rosenthal
 

Answers and Replies

  • #2
442
0
The idea that distant objects are receeding from us and thereby producing a proportional redshift --seems to be a fundamental tenant in terms of current cosmological thinking and theory. There have been alternate ideas proposed in the past including the tired light hypothesis-(whereby light traveling at great distances gives up energy to space and that this is what produces the red shift---still proportional to distance). If very distant objects are in fact receeding from us, they ought to be growing fainter in magnitude. Has this ever been measured ?? I wonder if the magnitude of distant objects on plates taken 20-30 years ago have ever been compared to present day magnitude of the same objects---to see-- if on average-- they have become slightly fainter. I wonder if our instruments are sensitive enough to make such a determination ???

Randy Rosenthal
From what I know Doppler shift is based on this and the usage of it's formula tellls us whether Object "X" radial velocity is approaching us or not but this isn't why you posted this thread.So in tired light hypothesis what exactly happens to the light itself? does it give a proportion of it's energy or does it exhaust? if we are to assume that energy is absorbed by the interstellar dust then wouldn't that actually produce anomaly itself towards the data which we have observed since the absorbed "energy"/photons are radiated in random direction. Sorry if I am deviating the subject of this thread,just a thought which just sprung my mind.I apologize If I got the wrong idea.
 
  • #3
Chronos
Science Advisor
Gold Member
11,408
738
The decrease in luminosity due to recession is so miniscule it would take hundreds of thousands of years to detect using current technology. Don't worry about 'tired light'. That conjecture has been thoroughly refuted. Note that cosmological redshift is not the same as doppler shift. Here is a good article addressing this subject:
http://www.astronomycafe.net/cosm/expan.html
 
  • #4
442
0
The decrease in luminosity due to recession is so miniscule it would take hundreds of thousands of years to detect using current technology. Don't worry about 'tired light'. That conjecture has been thoroughly refuted. Note that cosmological redshift is not the same as doppler shift. Here is a good article addressing this subject:
http://www.astronomycafe.net/cosm/expan.html
Ah thank you very much.
 
  • #5
26
0
if we are to assume that energy is absorbed by the interstellar dust then wouldn't that actually produce anomaly itself towards the data which we have observed since the absorbed "energy"/photons are radiated in random direction.
I was taught that this was not the case, that absorbed light would be retransmitted in the same direction just at a different wavelength otherwise this absorption would account for Olbers paradox! I apologise if I have misunderstood or misinterpreted the above statement.

From Wiki:
"However, this reasoning alone would not resolve the paradox given the following argument: According to the second law of thermodynamics, there can be no material hotter than its surroundings that does not give off radiation and at the same time be uniformly distributed through space. Energy must be conserved, per the first law of thermodynamics. Therefore, the intermediate matter would heat up and soon reradiate the energy (possibly at different wavelengths). This would again result in intense uniform radiation."
 
  • #6
16
0
The decrease in luminosity due to recession is so miniscule it would take hundreds of thousands of years to detect using current technology. Don't worry about 'tired light'. That conjecture has been thoroughly refuted. Note that cosmological redshift is not the same as doppler shift. Here is a good article addressing this subject:
http://www.astronomycafe.net/cosm/expan.html
Read the article you gave me. I have 2 comments---1st---"gravitational" redshift quoted in the article sounds like another version of the "tired light" hypothesis in the sense that red shift observed--(as a result of passing thru gravitational fields) is still --it seems to me--a function of distance transversed rather than a receeding of objects from one another or an increase in distance between the 2 objects. The Einsteinien notion that space is what is expanding between objects still seems to imply an increasing--rather than static--distance between the objects. I may be mistaken, but the whole expansion idea still seems based upon the redshift observations. 2nd comment---Current theory says that the most distant objects may be receeding from us at light --or greater than light speed--(given that space is what is expanding). This implies an increase of at least 1 light yr in distance increase per yr---or 20 light yrs of distance if the comparison plate is 20 yrs old. The objects are billions of light yrs away---still 20 parts per several billion may be close. I seem to remember reading several yrs ago --?--that instruments could detect magnitude changes of 1 part per billion---perhaps instrumentation is more sensitive now----if so, one would not have to wait centuries to make this kind of experiment---?----R Rosenthal
 
  • #7
Read the article you gave me. I have 2 comments---1st---"gravitational" redshift quoted in the article sounds like another version of the "tired light" hypothesis in the sense that red shift observed--(as a result of passing thru gravitational fields) is still --it seems to me--a function of distance transversed rather than a receeding of objects from one another or an increase in distance between the 2 objects. The Einsteinien notion that space is what is expanding between objects still seems to imply an increasing--rather than static--distance between the objects. I may be mistaken, but the whole expansion idea still seems based upon the redshift observations. 2nd comment---Current theory says that the most distant objects may be receeding from us at light --or greater than light speed--(given that space is what is expanding). This implies an increase of at least 1 light yr in distance increase per yr---or 20 light yrs of distance if the comparison plate is 20 yrs old. The objects are billions of light yrs away---still 20 parts per several billion may be close. I seem to remember reading several yrs ago --?--that instruments could detect magnitude changes of 1 part per billion---perhaps instrumentation is more sensitive now----if so, one would not have to wait centuries to make this kind of experiment---?----R Rosenthal
Unfortunately that kind of measurement is still beyond the realm of current (or near-term) technology. I'd add that concept of "tired light" is based in a larger notion of conservation of energy that may not apply to the universe as a whole.

edit: I'd add, those measurements we can make, as Chronos said, refutes the notion.
 
  • #8
26
0
I hope you aren't referring to photographic plates - there is no accurate means of comparing them to CCD images. Measuring a stars brightness is based on comparisons with other stars - standard stars. BUT how standard are the standard stars? Everything is moving, everything evolves and all stars change brightness over long periods of time. The very best photometric measurements go to 4-5 decimal places - thats it - but when they are compared to standards that only go to 3 decimal places, well we are a long, long way short of 1 part per billion. Variations in the earths atmosphere will be enough to throw out plate to plate comparisons in any case. Hubble would fair better but we are back to the physical constraints of the well depth on CCD chips.

Also, gravitational redshift doesn't imply a loss in energy of light so although the result that we observe may be the same, it is nothing like 'tired' light'.

Cheers

David
 

Related Threads on Question regarding red shift and tired light hypothesis

  • Last Post
Replies
0
Views
2K
Replies
8
Views
1K
  • Last Post
Replies
3
Views
2K
Replies
10
Views
3K
  • Last Post
Replies
11
Views
2K
  • Last Post
Replies
2
Views
13K
  • Last Post
Replies
4
Views
10K
  • Last Post
Replies
11
Views
4K
  • Last Post
Replies
7
Views
3K
Top