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FrankC
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Not to get off subject but, when I gaze at the Triangulum Galaxy how “Old” is the light I’m observing?
Kind of.DrStupid said:Does it make sense to ask for the age of light?
If you know Relativity no as anything traveling at the speed of light does not experience "time". However you can validly ask "when was a photon of light emitted relative to our reference frame". For somone lacking an understanding of special or general relativity and used to our largely nonreletavistic everyday experiences where Galilean transformations produce close enough approximations to reality that those rules were only valid for speeds much less than the speed of light wouldn't be realized until Michelson and Morley's famous experiment showed the speed of light is a constant of nature and that no "Aether" exists.DrStupid said:Does it make sense to ask for the age of light?
Dragrath said:no as anything traveling at the speed of light does not experience "time".
True that typical definition of time doesn't apply, hence why I said "time" not time, but it is a useful way to conceptualize a minkowski diagram as it will fall entierly along the spatial axes so it helps get the point across.weirdoguy said:That is a pop-science nonsense. There is no frame of reference in which light is at rest, so there is no meaningful way to talk about what light "experiences".
The age of observed light is determined by measuring the distance between the source of the light and the observer, and then calculating the time it took for the light to travel that distance. This is known as the light travel time. The longer the distance, the older the observed light is.
No, we cannot observe light that is older than the universe. According to the Big Bang theory, the universe is approximately 13.8 billion years old, so the oldest light we can observe is from that time period. Anything older than that would not have existed yet.
The oldest observed light in the universe is known as the cosmic microwave background (CMB). This is the leftover radiation from the Big Bang and is estimated to be around 13.8 billion years old. It can be observed in all directions in the universe and is considered to be the oldest light we can see.
The age of observed light is closely related to the age of the universe. As light travels at a constant speed, the farther away the source of the light is, the longer it takes for the light to reach us. Therefore, the age of the observed light can give us an estimate of the age of the universe.
Yes, we can observe light that is younger than the universe. This is because light from distant objects takes time to reach us, so we are essentially looking back in time. For example, if an object is 10 billion light years away, we are seeing the light that was emitted 10 billion years ago, even though the universe is only 13.8 billion years old.