Age of The Universe - Time vs Space

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Discussion Overview

The discussion revolves around the relationship between the age of celestial objects and the time it takes for their light to reach Earth. Participants explore concepts related to the speed of light, time dilation, and the implications of these ideas for understanding the age of the universe.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions the assumption that the age of a star is equivalent to the time its light takes to reach Earth, suggesting that if one were traveling at the speed of light, they would age differently than observers on Earth.
  • Another participant corrects the initial claim, stating that the age of an object observed at a distance does not correlate with the time taken for its light to arrive, emphasizing that the observer sees the object as it was in the past.
  • A participant elaborates on the concept of time for a photon, stating that it experiences no passage of time while traveling, which leads to the idea that it does not experience distance in the same way as observers do.
  • One participant introduces a geometric perspective using Minkowski diagrams, suggesting that as velocity approaches the speed of light, both time and space considerations change significantly.
  • Another participant expresses confusion regarding the relevance of geometric explanations to the original question, indicating that some responses may complicate rather than clarify the matter.
  • A later reply asserts that under General Relativity, a photon does not consider distance when traveling, as it traverses the universe in no time from its perspective.

Areas of Agreement / Disagreement

Participants express differing views on the relationship between time, distance, and the perception of age in the context of light travel. There is no consensus on the implications of these concepts, and the discussion remains unresolved.

Contextual Notes

Some participants' arguments depend on specific interpretations of relativistic effects and the nature of light travel, which may not be universally accepted or understood. The discussion includes various assumptions about the nature of time and space as they relate to light and observation.

Buttonpusher
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I have long wondered about this. When light takes x number of billion years to reach earth, we judge that the star emitting the light is x number of billions years old. I cannot understand that the star would be the same age as the distance it is away from us. If I was riding a spaceship at the head of that beam of light, I would not age the same as people, i.e.time, on earth. I would, in fact, be much yonger in years than the distance in light years traveled. Is this right? If it is, then would we not have to recalulate the age of the universe using this type of equation?
 
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Well your first assumption is wrong. We get light from the sun in 5 minutes but that doesn't mean the sun is 5 minutes old...
 
It's 8 minutes, Pengwuino, but you're right, there's a misunderstanding here.

Properly phrased, the concept is this: If you're looking at an object that is a billion light-years away, you're seeing light that was emitted a billion years ago. You are, therefore, seeing the object as it was a billion years ago.

The age of the object -- the time since it formed -- has nothing to do with it.

- Warren
 
Hi Buttonpusher! Welcome to PF. Plenty of brain bending concepts are regularly tossed around here. Chroot gave a very nice answer. Hopefully, I can expand on it a bit. If you were a photon, traveling at the speed of light, your wristwatch would indicate you had traversed the distance between your home star and Earth in no time flat. You would look exactly like you did the moment you began your journey, aside from some bending and stretching effects.
 
I thank you people for enlightening me on this subject. I understand now that when traveling at the speed at light, I get there quicker in time while the distance traveled remains the same.
_______________
Do not worry about your difficulties in Mathematics. I can assure you mine are still greater. - Albert Einstein
 
Actually, I believe that if you're going to use the "zero time" picture of light you must also have "zero distance". Physically this should be reasonable since if no time passed you didn't go anywhere.

Speaking more geometrically, as a velocity approaches c relative to some inertial observer both the time and space axes rotate up towards the 45 degree line on a Minkowski diagram, in the limit as v approaches c all of the events in space-time approach one single event.
 
dicerandom said:
...Speaking more geometrically, as a velocity approaches c relative to some inertial observer both the time and space axes rotate up towards the 45 degree line on a Minkowski diagram, in the limit as v approaches c all of the events in space-time approach one single event...
What on Earth does this have to do with the OP's question? (Sorry to pick on you Dicey, you're one among many). These answers are worse than no answer at all, as they actually confuse the matter.
 
DaveC426913 said:
What on Earth does this have to do with the OP's question? (Sorry to pick on you Dicey, you're one among many). These answers are worse than no answer at all, as they actually confuse the matter.

The OP's original question had already been answered, I was responding to his comment that "when traveling at the speed at light, I get there quicker in time while the distance traveled remains the same".
 
Under GR, traveling at the speed of light completely negates any consideration of distance. A photon, unless intercepted, traverses the entire universe in no time whatsover [by her watch]. Study the Einstein equations and this will become apparent.
 

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