Alan McDougall Posted January 28, 2014 Posted January 28, 2014 Define local. Most people I've seen touch on this topic always brush it off with a tangent as shown below. Conveniently denying an aether when it goes against relativity, then mandating the existence of an aether when they need it to exist. Exactly what I meant when I pointed out how unscientific relativity is. It becomes unfalsifiable when you see objects moving away from eachother at speeds greater than C, and we just turn around and say "it isn't really the objects moving that fast, but time and space expanding between those objects." Which inherently goes back to necessitating an aether... Even though SR is based upon the lack of evidence of such an aether. So, assume these two objects are traveling away from eachother at a speed greater than C. These two objects emit light toward eachother... Alan, do you believe light from the two objects can reach the opposite objects? What exactly is this strange thing you call an "Aether' this idea was proved false over a century ago, it smacks of a flat earth like belief to me!
John Cuthber Posted January 28, 2014 Posted January 28, 2014 ""it isn't really the objects moving that fast, but time and space expanding between those objects." Which inherently goes back to necessitating an aether." No.
Didymus Posted January 29, 2014 Posted January 29, 2014 Thank you for your polite response, strange. So, if: "There are galaxies receding so fast that light from them will never reach us." (I agree with this) Yet the speed of light relative to all frames of reference is immutable, according to SR, that light must get to us at some point. If object A and B are X lightyears away, if light is emitted from either object toward the other, light should reach the opposite object in exactly X years, regardless of the direction or rate either object is traveling during those X years. Agree or disagree? -1
Strange Posted January 29, 2014 Posted January 29, 2014 In the spirit of this thread's topic, if object A and B are "X" lightyears apart when the light is emitted, and the speed of light is constant, how can light take more than "X" years to travel from A to B? Because the distance is increasing. Importantly, the distance is not increasing because the source is moving; the distance is increasing because, at every point during the journey, space is expanding and the distance to be travelled increases (in this case, faster than the light can cover that distance). I'm challenging strange's suggestion, which goes against popular opinion. Does it? I would be happy to be shown what I have misunderstood.
Didymus Posted January 29, 2014 Posted January 29, 2014 I don't mean to insinuate that "you have misunderstood" anything. Only that that topic of this thread is "Why does light travel at 299,792,458 meters per second" and in the situation you brought up, light traveling from object A to B is not traveling at 299,792,458 meters per second relative to B when A is moving away at a speed faster than 299,792,458 meters per second. If you explain it as neither object moving at all, but space growing (or shrinking) between two objects, it's an interesting perspective. But whatever frame of reference you define as moving... if light can never reach a certain object, then that light in your example can not be approaching that object at the constant of C as suggested in the original post. The question this begs would be at what point this breaks down.
Strange Posted January 29, 2014 Posted January 29, 2014 I don't mean to insinuate that "you have misunderstood" anything. Only that that topic of this thread is "Why does light travel at 299,792,458 meters per second" and in the situation you brought up, light traveling from object A to B is not traveling at 299,792,458 meters per second relative to B when A is moving away at a speed faster than 299,792,458 meters per second. If you explain it as neither object moving at all, but space growing (or shrinking) between two objects, it's an interesting perspective. But whatever frame of reference you define as moving... if light can never reach a certain object, then that light in your example can not be approaching that object at the constant of C as suggested in the original post. This is the difference between proper speed and coordinate speed. But that would be getting even further off topic. The question this begs would be at what point this breaks down. It doesn't. (As far as is known.)
Didymus Posted January 30, 2014 Posted January 30, 2014 (edited) Oh, for crying out loud, the issue here is the topic under discussion is not expansion of the universe, so stop bringing up expansion of the universe! (Didymus, expansion does not involve a single inertial frame, and as you point out, the thread is about c being invariant in inertial frames.) Swon. We are discussing mainstream theories, including important questions tosk shen considering those theories. The forum rules specifically disallow the suppression of open discussion and different considerations of mainstream theories. considering the speed of light in "all inertial frames" includes inertial frames within an expanding universe. If you have an explanation consistant with the popular theory as to how celestial bodies (with valid inertial frames) can be moving at a speed greater than C relative to other bodies due to an observably expanding universe to the point where light from one body can't make it to the other because of their relative motion.... I would love to see it. I'm sure I'm far from the first person to think of such an example, therefore, many people may benefit from having the question answered. If you haven't considered it... Perhaps you should. By considering examples of situations where a theory -appears- to be weak, we test it. Either we will find an explanation and gain a better understanding of a correct theory, or we can find a weakness in a theory and learn from it. Note I am not offering an alternative theory or personal viewpoint. Only contributing to the conversation at hand to ask how you believe the popular theory applies to a valid circumstance. Edited January 30, 2014 by Didymus
Didymus Posted January 30, 2014 Posted January 30, 2014 Since the moderation staff keeps bringing the topic up: The overarching question is "Why does light (behave a certain way)." The answer of "it doesn't always" is a completely on topic response. The topic of the forum is not different mediums... yet, count how many people specified that light only moves at C in a vacuum. Although black hole's ability to alter light's course was brought up, the event horizon wasn't specifically mentioned. It's equally applicable to mention that the mainstream perspective is that light can be trapped at the event horizon of a black hole, neither escaping, nor being drawn in. So, the OP's "Why does light move at C" can be given the response of "it doesn't... if it's trapped in an event horizon." To the same extent, no... universal expansion itself isn't the topic of this thread. But "Why does light move at C?" ... in the case of universal expansion, according to mainstream understanding, it doesn't (relative to objects far enough away that the light can never reach it). Point was made a couple days ago... you could respond to it or ignore it. If you'd like the thread to go in a different direction... common sense says to start talking about the direction you'd like the thread to go. But if the moderation staff feels the need to address me, I will respond in the method they chose to address me. Send me a message in private if you'd like a private response. But if -you- address me in-thread, my response to your address can not be considered off-topic. You're the one driving the 'off-topic' topic.Were it up to me, this whole tangent you guys keep sticking to would be dropped, and we can get back to physics instead of politics.
hypervalent_iodine Posted January 30, 2014 Posted January 30, 2014 ! Moderator Note For goodness sake, why is this so difficult? You're going on a holiday. See you next week! 2
Strange Posted January 30, 2014 Posted January 30, 2014 Although black hole's ability to alter light's course was brought up, the event horizon wasn't specifically mentioned. It's equally applicable to mention that the mainstream perspective is that light can be trapped at the event horizon of a black hole, neither escaping, nor being drawn in. So, the OP's "Why does light move at C" can be given the response of "it doesn't... if it's trapped in an event horizon." Really? I know there is a zone outside the event horizon that photons can orbit, but I have never heard of photons being trapped at the event horizon. Can you provide a reference to this?
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