Does the Age of the Universe Need to Factor in Light's Expansion?

Click For Summary

Discussion Overview

The discussion centers around the implications of light's wavelength expansion on the age of the universe, particularly in relation to the Cosmic Microwave Background (CMB). Participants explore whether the expansion of light's wavelength should be factored into calculations of how long it takes for light to reach us from the early universe.

Discussion Character

  • Exploratory
  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • One participant questions the accuracy of the age of the universe by suggesting that the expansion of light's wavelength could mean light reaches us sooner than previously thought.
  • Another participant argues that all light travels at the same speed, implying that the wavelength expansion does not affect the time it takes for light to reach us.
  • A metaphor involving a string is used to illustrate the concept of light traveling while its wavelength expands, but this is challenged by others who clarify that photons do not behave like physical objects with extent.
  • Redshift is discussed as a phenomenon that lowers the energy of photons, with one participant comparing it to a baseball caught by a retreating outfielder.
  • There is a suggestion that the wavelength stretching of light does not mean we perceive the light sooner, as its speed remains constant regardless of energy changes.
  • One participant explains that the redshift is a result of the expansion of space, which also means that light travels a longer distance than it would have otherwise, leading to a later perception of the light.

Areas of Agreement / Disagreement

Participants express differing views on whether the expansion of light's wavelength affects the perception of light's arrival time. Some argue that it does not, while others suggest that it could imply a different understanding of how we perceive light from the early universe. The discussion remains unresolved with multiple competing views present.

Contextual Notes

Participants reference concepts such as redshift and the expansion of space, but there are limitations in the assumptions made about the relationship between wavelength expansion and light travel time. The discussion does not resolve the implications of these concepts on the age of the universe.

jinny1
Messages
3
Reaction score
0
Age of Universe inaccurate??

Hi. i have a question that could already been nullified.

Reading about the CMB it occurred to me that normal light is around 370 - 770 nm in wavelength and a microwave could be upto 30cm long..
That means light has been expanded a million fold?? (not sure) since the moment light could be emitted.

Wouldnt that mean we have to take into account the expansion of light's wavelength into the age of CMB?? As it would reach us a lot sooner than if light had a higher frequency...Or have we already done that..

Thanks
 
Astronomy news on Phys.org


As it would reach us a lot sooner than if light had a higher frequency.

That doesn't make sense. All light travels at the same speed.
 


its like a 1cm string traveling at c to reach a certrain distance but during the course of its journey the string becomes more liken 100km long.
 


jinny1 said:
its like a 1cm string traveling at c to reach a certrain distance but during the course of its journey the string becomes more liken 100km long.

A piece of string is something physical with physical extent. A photon is not like this. Loosely speaking, you can think of it as a point particle. Its frequency corresponds to how fast the electric field and magnetic field change direction.
 


jinny1 said:
Reading about the CMB it occurred to me that normal light is around 370 - 770 nm in wavelength and a microwave could be upto 30cm long..
That means light has been expanded a million fold?? (not sure) since the moment light could be emitted.

Sorry, you seem to be suggesting that visible light is somehow transformed into microwaves over time? Why do you think this?

Are you talking about redshifting?
 


Redshift does lower the energy of a photon - like a baseball caught by a retreating outfielder. Nothing mysterious about that.
 


DaveC426913 said:
Sorry, you seem to be suggesting that visible light is somehow transformed into microwaves over time? Why do you think this?

Are you talking about redshifting?

yea..the wavelength of light is stretched...wouldnt that mean we would be able to perceive the light sooner?
 


jinny1 said:
yea..the wavelength of light is stretched...wouldnt that mean we would be able to perceive the light sooner?
No. It still travels at the same speed. The attentuation does not make the beam reach its destination sooner.

Intuitively, how could it? Going from visible light to microwaves is a one thousand-fold decrease in energy. The beam is one thousand times more "tired", as it were...
 
Last edited:
  • #10


If we're talking about light emitted early in the history of an approximately homogeneous and isotropic universe, and I assume we are, then the redshift is caused by the expansion of space when the light is in transit. So the same thing that causes the redshift also forces the light to travel a longer distance than it otherwise would have. I guess you could say that we "perceive the light later", not sooner. Also, when the light gets here 13.7 billion years after it was emitted, the point in space where it was emitted it is about 46.5 billion light-years away. This figure is greater than 13.7 billion light-years because space has expanded.
 

Similar threads

Graduate Accelerating Universal Expansion
  • · Replies 6 ·
Replies
6
Views
4K
Undergrad How Does a CMB Photon Travel Through Expanding Universe?
  • · Replies 39 ·
2
Replies
39
Views
6K
Graduate Quantum Confusion - Does not exist until it's observed and age of universe
  • · Replies 3 ·
Replies
3
Views
4K
Undergrad How does the expansion of space affect the age of the universe?
  • · Replies 25 ·
Replies
25
Views
5K
Graduate Space time expnasion, age of universe.
  • · Replies 4 ·
Replies
4
Views
2K
Graduate Issues regarding the expansion of the Universe at the subatomic level
  • · Replies 15 ·
Replies
15
Views
5K
High School The accelerated expansion of the universe; redshift and time/distance
  • · Replies 3 ·
Replies
3
Views
2K
Graduate Visual perspective at the speed of light:
  • · Replies 3 ·
Replies
3
Views
2K
Graduate Thoughts and questions about the CMBR.
  • · Replies 25 ·
Replies
25
Views
4K
Undergrad Some questions about Cosmic Microwave Background radiation
  • · Replies 13 ·
Replies
13
Views
7K