Redshift and Universal Expansion

  • #1
Correct me if I'm wrong, but the only real evidence showing that the universe is expanding (and accelerating it's expansion) is by observing the so called "standard candle" supernovae which always have the same luminosity and observing that the farther they are, the more red shifted their light is, and since red shift indicates that an object is moving away from us, we assume that the whole universe is expanding, is this an accurate description?

Isn't also equally plausible that there is some sort of electromagnetic influence on some properties of light which on long time scales will make the light more red shifted?

In other words, we assume that the universe is expanding because the farther an object is, the more red shifted it is, and by having such theoretical construct we are assuming that light is unchanged, that the properties of light are a constant (I'm not referring to the speed of light here), what I'm questioning is that, when light travels across space for billions of years, it should be expected for it to suffer some interference in it's wavelenght.

And if this notion can be sustended by current understanding, wouldn't it somewhat invalidate the whole lambda cdm cosmological model, and in effect the big bang theory itself?
 

Answers and Replies

  • #2
Drakkith
Staff Emeritus
Science Advisor
21,156
4,996
I'm not well versed on the details of all this, but I believe that current evidence and theories point to the redshift being because of expansion. I have heard of the theory or idea that light traveling for billions of light years might lose energy, but I've never seen any evidence on it.
 
  • #3
I'm not well versed on the details of all this, but I believe that current evidence and theories point to the redshift being because of expansion. I have heard of the theory or idea that light traveling for billions of light years might lose energy, but I've never seen any evidence on it.

I'm not referring to a "loss of energy", what I'm questioning is, having light travelling for billions of years, and in the process being constantly interacting with other light, matter, gravity and all other aspects of nature, known and unknown, isn't it equally plausible that the sum of all this interactions for billions of years would in effect alter some properties of this light, making it increasingly more red shifted as a function of time?

And this idea being plausible, wouldn't it directly invalidate the "need" for a concept such as the big bang theory or at least to some extent invalidate that it would have happened at about 13.7 billion years, but instead much farther in time (if at all)?
 
  • #4
Drakkith
Staff Emeritus
Science Advisor
21,156
4,996
I'm not referring to a "loss of energy", what I'm questioning is, having light travelling for billions of years, and in the process being constantly interacting with other light, matter, gravity and all other aspects of nature, known and unknown, isn't it equally plausible that the sum of all this interactions for billions of years would in effect alter some properties of this light, making it increasingly more red shifted as a function of time?

That's what I'm saying. The more redshifted light is, the less energy it has for our frame here on earth.
 
  • #5
1
0
If I understand correctly, this hypothesis is not considered a real alternative anymore, although there is no conclusive proof against it. The main reason is because the Big Bang model and the expanding universe can explain easily observations that this model (known as "tired light" model) have difficulties explaining. I am no expert on this, but you can find a lot of information if you search for "tired light".
 
  • #6
Ken G
Gold Member
4,438
333
I'm not referring to a "loss of energy", what I'm questioning is, having light travelling for billions of years, and in the process being constantly interacting with other light, matter, gravity and all other aspects of nature, known and unknown, isn't it equally plausible that the sum of all this interactions for billions of years would in effect alter some properties of this light, making it increasingly more red shifted as a function of time?
That depends on one's criterion for what is "equally plausible." If one equates that phrase with "has equal evidence in favor of", which I think is a fair interpretation of those words, then the answer is "no." The reason is that we have all kinds of evidence that gravitational effects can cause redshifts, and an expanding universe obeys the gravitational constraints of general relativity (if we throw in some dark matter and dark energy, but there is also good evidence for doing that), and general relativity has a lot of evidence to support it as well. Constrast that with the idea that light could be redshifted due to unknown interactions with "matter and fields", without any evidence that any such interactions are actually occuring, and the scale tips decisively away from that hypothesis. It doesn't make it wrong, it just makes it not the best current theory, and not the best current source of testable hypotheses that can guide future observations and keep cosmology active and vibrant, as it is today.
And this idea being plausible, wouldn't it directly invalidate the "need" for a concept such as the big bang theory or at least to some extent invalidate that it would have happened at about 13.7 billion years, but instead much farther in time (if at all)?
Yes, it would certainly invalidate the need for a big bang theory. The question then becomes, is throwing out the big bang theory a step forward or a step backward for science? That's not always easy to tell, but one standard metric is, does it empower us to explain more observations, or do we lose the power to explain them? Does it furnish us with a new set of testable hypotheses that observers can jump on with the proposals of tomorrow, or do they lose testable hypotheses to motivate their observing proposals? Those criteria are generally what is used to tell if science is moving forward or backward, and at the moment, throwing out the Big Bang and GR-described redshifts certainly seems like a step backward to most active astronomers.
 
  • #7
I'm not referring to a "loss of energy", what I'm questioning is, having light travelling for billions of years, and in the process being constantly interacting with other light, matter, gravity and all other aspects of nature, known and unknown, isn't it equally plausible that the sum of all this interactions for billions of years would in effect alter some properties of this light, making it increasingly more red shifted as a function of time?

And this idea being plausible, wouldn't it directly invalidate the "need" for a concept such as the big bang theory or at least to some extent invalidate that it would have happened at about 13.7 billion years, but instead much farther in time (if at all)?

When light interacts with something, it usually means it is absorbed or scattered, doesn't it? If this were the case, wouldn't the light not reach us in the first place? Isn't light that reaches us reaching us because there was nothing in its way on its way here?

When light goes through a strong gravitational field, it bends according to spacetime bending in order to remain on a straight line, so it can't be losing energy in that respect.
 

Related Threads on Redshift and Universal Expansion

  • Last Post
2
Replies
27
Views
5K
  • Last Post
Replies
10
Views
3K
  • Last Post
2
Replies
32
Views
5K
  • Last Post
Replies
1
Views
1K
  • Last Post
Replies
5
Views
3K
Replies
7
Views
2K
Replies
16
Views
26K
  • Last Post
Replies
9
Views
2K
  • Last Post
Replies
2
Views
682
Top