« on: 14/08/2016 00:26:57 »
I don't think it's a very useful concept. As I understand it, any object moves through spacetime at the speed of light.
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Sure, but irrespective of what units we apply to it, light still has a maximum speed of a certain value. Why is it that value, 300 million metres per second?I think this is the same as asking why the speed of light is finite at all, since any numerical value we assign to it is purely arbitrary, depending on our perception of whatever time is. Other than that I like AI42's answer, that it can't go any faster because there's no fuel left to push it.
I think you've said it yourself - "no material thing is moving faster than light". Your inference depends on the 'image' of the light on the shell being a physical object when it is nothing of the sort. The only reality of that image is that it is a product of your brain's interpretation of photons hitting your retina having bounced back from the shell.
"If you wave a flashlight across the night sky, then, in principle, its image can travel faster than light speed (since the beam of light is going from one part of the Universe to another part on the opposite side, which is, in principle, many light years away). The problem here is that no material object is actually moving faster than light. (Imagine that you are surrounded by a giant sphere one light year across. The image from the light beam will eventually hit the sphere one year later. This image that hits the sphere then races across the entire sphere within a matter of seconds, although the sphere is one light year across.) Just the image of the beam as it races across the night sky is moving faster than light, but there is no message, no net information, no material object that actually moves along this image."
my point is light is not like a ball that you throw upwards, then it slows down and falls back to the ground. It always travels at the speed of light. Are we suggesting that when a photon leaves a body with sufficient gravity it travels upwards for a bit, and then slows down and falls back to the body? Cause that's what it means when an object is under the escape velocity.Correct, the light doesn't slow down at all, which is a common misconception. However, if you watch from a distance it might appear to.
Light doesn't travel slower when it exits a body with larger gravity, so how can gravity be responsible for stopping light in its' tracks?
To PmbI think that's right. Any change in measured speed is due to the observer, not intrinsic.
So you saying if i were near the black hole the light would appear to travel at the usual speed of "c" because of time being relative to space, but if i were observing from a distance it would appear to travel slower?
Well, for a lot of people, religion is a source of comfort, hope, solace, ....But the things in religion which bring comfort, such as companionship or a specific goal in life, can just as easily be found without the actual belief in god and without having to organise the way society works around this, whereas we would all still be in caves without science.
Don't get me wrong, I'm pretty atheistic myself, but I'm not blind to see what religion can do for other people. Of course there are negative aspects to religion, but so are there to science, as Ophiolite already pointed out.
I think he meant who is referred to by the "you" in your post, not who you are...And what do you mean, who am I?I don't expect you to understand the equation,By the way, who is you?
It does, however, depend on the gravittional potential Phi. See derivtion at http://home.comcast.net/~peter.m.brown/gr/c_in_gfield.htm Einstein first proved this in 1907. It was also experimentally proven.I am quite good with maths, but the meaning of all that is a bit beyond me. Is it saying that as you approach the black hole the local speed of light slows, first to walking pace, then finally zero at the event horizon? Because that goes against all that I remember from studying this.
So in the presence of gravity the speed of light becomes relative (variable depending on the reference frame of the observer). This does not mean that photons accelerate or decelerate. This is just gravity causing clocks to run slower and rulers to shrink.
Thanks for the reply. I'm not so good with maths.No. The speed of light in a vacuum is a universal constant, regardless of frequency, and does not change. The frequency might be red-shifted and the pathway might appear to be bent, but light does not get slowed or speeded up. Every observer will still measure the speed as c, no matter what frame of reference they are in.
Are you saying gravity can slow or speed up light? Does a red light move slower than a violet light?
The difference in time dilation between the Earths surface and a few hundred miles above the surface is minute but it is enough for the surface of the Earth to accelerate at 1g. Scaling that up to the size of a galaxy it must become very significant and should not be ignored.Nonsense. Don't even try to explain what you think you mean by this, I will just avoid your posts in future.
That time contraction does not lead to time passing faster (from the reference frame of a distant observer).The latter. If time contraction at the periphery is say 0.01% (and I have no idea whether that is the right figure, probably nowhere near) and at the centre is 100 times this because the density is also 100x, then time dilation at the centre would be 1%. Hence time at the centre would run at about 99% that of the periphery.
That time contraction may be 100 times greater but time would not be running 100 times faster. Are you questioning the numeric relationship between time contraction and time passing faster.
Continuation of reply # 2 of this post.That doesn't follow. Time dilation might be 100 times greater, but that wouldn't mean time itself is running 100 times faster.
If the Milky Way has a density gradient of 100 fold (thanks Clifford) from center to periphery then presumably it has a 100 fold time dilation gradient. If time at the periphery is passing 100 times faster than at the center,.
From memory it seems like Fabio & Lesage's (and Bamboozled's) idea, but it is a long time since I read it. I would offer to sell you mine but there are loads on Amazon at 1p.This idea was put forward in The Cosmic Ecosystem, by Alan Johnston, published 1980.Which idea? Are you saying that he presented the idea of Fatio & Lesage? Or did he beat me to my idea? I don't doubt that his cosmology shared one or two elements of mine, but I'd be very surprised if he had more than that.
I don't see any summary, review or exerpt of his book online. Guess I'll have to buy the book.
This is one of those subjects where, as a layman, I am finding it difficult to accept what science is claiming.I feel somebody has to try to address this, and even though I'm no logician I'll try.
Statement: The universe appears to be expanding at an ever faster accelerated rate.
Statement: This is not the results science had predicted.
Statement: Something must be causing the universe to expand faster and faster.
Statement: There is nothing we can identify that is causing this faster expansion rate.
Conclusion: It must be something we humans cannot detect. We will call it Dark Energy.
Query. Why do we suspect this Dark Energy exists?
Statement: Because without it, the universe would not be expanding at an ever accelerating rate.
Now I squeaked by logic in college by the skin of my teeth, and with the kindness of a decent teacher. So I am sure my logic flow is full of holes. But actually there are not. There appear to be holes, but in truth, they just cannot be detected. We call this Dark Logic.
Okay the last paragraph was my attempt at a joke. But I'm serious about the rest. And that appears to be circular logic to me. Thus my difficulty with this theory.