There's strong evidence this is true of most galaxies!
Does light only travel at one speed?
- Thread starter Megahurtz400
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There's strong evidence this is true of most galaxies!
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Your initial post said that both its speed and direction could be changed by mavity and you specifically mentioned the variable speed of light (and have done so again). Gravitational lensing indeed involves a change of direction but, as the wiki page says, it doesn't involve a change in the speed of light. The wiki page you've linked to about the variable speed of light is about a hypothetical situation. In general relativity (which predicted gravitational lensing) the speed of light is not changed by gravitational fields. Measurements in cosmology which attempted to find evidence for a varying speed of light aren't doing it in regards to gravitational fields but in regards to a universal time dependency, ie it was different long ago compared to now. This is different from asking if the speed of light is different in a strong gravitational field. Even in the cosmological case the evidence put an upper bound on the variation of something like less than 1 part in a million over 10 billion years. As such there is no evidence for the speed of light varying due to time or due to gravitational fields.
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Maybe, but I also stated that it was constant in a vacuum.
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Maths as an undergrad and string theory as a postgrad. Yes, I think 'geek' covers it pretty wellBetanumeric did you study physics or astro-physics? You sound like one geek guy
You mentioned 'variable light speed' after saying 'mavity' and then linked to the wiki page on variable light speed in the sense of the vacuum speed, it says so in the first sentence.
And I never said it did. You misread my initial post and if you had read it in it's full context you would have seen that I didn't.
Sorry I'm not a physicist but assuming it's path is changed and it still reaches it's destination ( this is where I might be wrong ), then it's speed DOES change, it's velocity however doesn't.
Pedantry is most unbecoming you know.
The gist of my post was obvious, and I suspect you know that and are simply attempting to use it as an excuse to unnecessarily flex your knowledge, when you could quite simply have accepted that the statement on the vacuum speed and the time taken for the event to be visible on Earth was the part relevant to the OP.
Poorly worded I concede, but I thought it was obvious what I was saying.
To be extremely pedantic about it, apparently the speed of light doesn't actually change even through transparent mediums, and I am sure that with your extensive knowledge you can tell us why? because I'll be damned if I understand what my bro is saying....
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What if the light source is being emitted exactly perpendicular to the gravitational source (ie me shining a torch directly up from the earth). Would mavity then pull my light back down in exactly the same direction as it is heading thus affecting its speed & velocity
What if the light source is being emitted exactly perpendicular to the gravitational source (ie me shining a torch directly up from the earth). Would mavity then pull my light back down in exactly the same direction as it is heading thus affecting its speed & velocity
Like I said I'm not a physicist so I have no idea what effect mavity has on light, I was just checking his post from a logical point of view. Just that if the path was to change then it would take longer to reach it's destination? I'm assuming it is still reaching the same point ie instead of going into a straight line to it's destination it goes in a parabola. Then it's speed would change because it would take longer to get there, but it's velocity wouldn't, however again if it is mavity that would cause this parabola then it's velocity would have course be accelerating (or decelerating depending on which way you are looking)...
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As I said in my previous post, you said :
"While light's speed and direction can be affected by specific mediums such as Glass, and forces such a mavity (the Variable Speed of Light), it has a constant speed in a vacuum (the Effective Speed of Light)"
The 'variable speed of light' comment comes immediately after mavity, which would be read as you saying mavity has an effect on the speed of light. If you were referring to just 'specific mediums such as glass' in regards to varying the speed then the '(the Variable Speed of Light)' bit should have come after that, not after 'such as mavity'. When I asked about it you then linked to the wiki page on variable light speed, as if you were trying to justify the variable light speed comment, which had been made in connection to mavity in your initial post.
I'm not bothered if you did initially claim that mavity altered the speed of light and now you're retracting it or not but your initial mentioning of 'variable speed of light' immediately after saying 'mavity' and then linking to the wiki page on precisely that certainly gave the impression you were saying it was an effect.
As I've explained, putting 'variable light speed' immediately after 'mavity' certainly implied you were connecting the two. I wasn't attempting to be pedantic, I have no idea your level of understanding and hence I was just correcting what I saw to be a mistake. I didn't say "OMG you idiot!" and it never entered my mind, I was trying to be helpful. If this is just a crossed wire then try to get less worked up about it.
Now I'm beginning to again think you did say mavity altered the speed of light because you're trying to turn this around onto me by throwing out another factoid and saying "Well if you're so smart explain that!". Where did I claim I know such a thing? The fact black holes and relativity happen to be things I have some knowledge of doesn't mean I'm omniscient or believe myself to be. Yes, I'm aware that the effect in materials is not due to a literal slowing down or even a sequence absorption/emission but some interference of the electromagnetic fields within the material and the electromagnetic field of the photon but the precise calculations I am not familiar with. Practical photonics wasn't something I studied.
I post in threads where I have something to say. I don't post in football threads because I don't care about it. I posted in this thread because I have something to say and it happens I had relevant comments to make to plenty of people's posts. If you deal so badly with someone who knows a bit of science might I suggest staying out of science threads? Or at the very least constructing your comments in a clearer fashion?
The time taken increases, as the photons have to go along longer paths. In the case of lensing if they could travel in a straight line through the galaxy in their way then they'd arrive earlier than those which bend around it. I vaguely remember something about this being a noticeable effect, some lensed galaxies have 'older' left hand images than right (or vice versa, its an arbitrary choice), in the range of hundreds, if not thousands of years.
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That's the Newtonian point of view. In relativity the light will still move at c but it still has to lose energy (just as a ball will lose energy by slowing down) and it does this by red shifting. This means that its frequency goes down and since photon energy E is related to frequency via E = hf (where h is Planck's constant) a lower frequency means lower energy. Conversely a satellite shining a torch down to you will mean its light gets blue shifted, it'll increase in frequency such that it gains as much energy as your torch light going up to the satellite would lose.What if the light source is being emitted exactly perpendicular to the gravitational source (ie me shining a torch directly up from the earth). Would mavity then pull my light back down in exactly the same direction as it is heading thus affecting its speed & velocity
This effect was one of the main ones Einstein predicted, which has been used to test general relativity. It was originally done using specialist equipment at a university but now its something which has to be factored in when computing locations using the GPS network.
As I said, poorly worded maybe, but the relevance to the OP was clear.
Yet I stated clearly that Gravitational Lensing was what I was referring to and made the note as to the direction in that clarification.
I didn't claim anything, only asked if you could explain the why better than my brother here, given that you seem to have an extensive knowledge on the subject at hand.
I haven't refuted anything you had to say on the subject at hand, only your refusal to accept that I did not state what you claim I did and you simply misread something. I am sure that someone of your intelligence could see, especially with the clarification given that however constructed the relevant part was perfectly clear.
To quote myself in reply to your question "to what are you referring?"
Both wiki pages were included to illustrate the difference, not the similarity between Speed and Direction.
I thought it was obvious, apparently not.
Anyway it doesn't really matter, and is nothing whatsoever to do with the thread so may I suggest we drop the issue and move on?
BetaNumeric: I think you were unnecessarily harsh in responding to Castiel's question about light travelling through a medium. It was a genuine question, not a smart arse "well if you're so clever...!" retort.
Castiel: Relax!
Castiel: Relax!
Castiel: Relax!
Indeed. One of my character flaws I'm afraid. I am now relaxed and have dropped the subject.
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I never said I knew about the specifics of photonics within materials. In fact, despite your comments about me supposedly trying to show off, I actually said very little about my knowledge. Even when asked I gave a 1 line response to the question. I didn't open with "Listen to me, I have the following qualifications : ", I just explained a few things and made some comments. If I'd wanted to go in with guns blazing it'd have been a lot different.
The original post was about the speed of light and it always being the same. That's to do with relativity, specifically special relativity. Then someone else brought up mavity and black holes, which is general relativity. Neither of them relate to the quantum interactions of photons with atoms in materials, that would be (unsurprisingly) quantum mechanics. I've studied quantum mechanics but its a big subject and I went down the particle physics route rather than the quantum properties of materials route. Like any area of science, quantum mechanics is so huge you could spend a life time working on it and only scratch 0.1% of it. I happen to be confident in the little bit I scratched but all too often those with little science experience mistake that confidence in my area of choice as no it all arrogance (not just in me, but in scientists in general).
Since I have no problem saying so, fine I was wrong in how I read your initial post. However, even if you did mean as you say in that post your "So I'm sure you can explain....." comment isn't a ringing endorsement for your attitude towards people who actually know a little bit of science, arrogant or not. But hey, I'm new here (actually I'm not, my previous account here is user number 28, but its been a fair few years) so maybe I've just got the wrong impression and things will iron themselves out as time progresses.
Anyway, I have work in the morning and I should probably get some sleep...
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Light travels at light speed but this varies through different mediums.
For example, when it travels through frozen plasma, it only moves at 38 mph.
For example, when it travels through frozen plasma, it only moves at 38 mph.