They weren't. See the video that MadDogMurdock linked, it explains far better than I could:
Astronomy / Space Is the universe expanding faster than the speed of light?
They weren't. See the video that MadDogMurdock linked, it explains far better than I could:
A thought/idea from what you said, feel free to tear it to pieces,
The universe is expanding, mass moving apart therefore gravity is thinning out. Gravity slows down light (by distorting space time) therefore if gravity was thicker in the past, light ran slower resulting in a red shift. could this extra red shift affect the calculations for expansion/contraction.
am I talking nonsense??
thanks. great video.
The universe is a bit older than 14 billion years. Immediately after the big bang, light could not travel very far before it got scattered by something else in the way. Eventually, everything cooled down and spread out enough for atomic matter to form, which allowed the light to pass more freely through the gaps. This was 14 billion years ago, so the light that was still flying around back then is only just reaching us. Any older light than that was being constantly scattered up until that time, so all we see is a constant nearly uniform cosmic background radiation.
EDIT: I just noticed your avatar. Star Fleet was an awesome series.
A year is defined as the time it takes the Earth to travel one revolution around the Sun, from the perspective of an observer on the Earth. Light-years use the Julian Year, which is fully defined as the duration of 290097396344952000 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium 133 atom when both the atom and the observer are in the same reference frame.
If you're standing in the same place as your caesium 133 atom, moving at the same speed, shine a beam of light into the sky and then count off 290097396344952000 periods of the radiation corresponding to the transition between the two hyperfine levels, your beam of light will have travelled a total of 9460730472580800 metres, or one light-year.
A metre used to be defined as one ten millionth of the distance from the North Pole to the Equator along the surface of the Earth (of course, from the perspective of an observer on the Earth). Now it's defined as 1/9460730472580800th of the distance light travels in a year.
If time's a drug, then Big Ben is a huge needle injecting it into the sky.
Because the ruler used to measure the distance was very tiny.
The speed at which light propagates through transparent materials, such as glass or air, is less than c. The ratio between c and the speed v at which light travels in a material is called the refractive index n of the material (n = c / v). For example, for visible light the refractive index of glass is typically around 1.5, meaning that light in glass travels at c / 1.5 ≈ 200,000 km/s; the refractive index of air for visible light is about 1.0003, so the speed of light in air is about 90 km/s slower than c.
You have taken my tennis ball analogy out of context. An object such as a car that starts from standstill, then travels in a straight line at increasing speed, is accelerating in the direction of travel. This is consistent with my tennis ball analogy but you fail to mention this. Instead you simply stated that acceleration is a change in velocity. This is also correct but you should have acknowledged my effort to describe an increase in speed.
They appear to be moving away but why can't they be contracting to a point on the other side of a sphere if the universe is round? Another explanation of contraction can be found here....
http://www.contractinguniverse.co.uk/
And finally, my apologies for my lack of scientific language in my first post. I admit that I should have been more specific.
And what you're measuring is a wave whose velocity is an average of the velocities of individual particles, all of which are travelling at c.
Let's say you shine a beam of light into a material and each particle is split at a uniformly random angle somewhere between 0 and 45 degrees. All of these particles are travelling at c. The average velocity is ~2c/sqrt(3) in the direction of the original beam, which leads to an apparent reduction in speed (and reduction of the speed of propagation of the wave) of ~15%, meaning a refractive index of 1.15. At no point in this model has light travelled slower than c.
In practice, it's not uniformly spread, and there is some absorption and emission going on, but that's roughly how it works, in simple terms.
Apologies for that, but I was rather insulted that you seemed to think that with "A ball in the air is under constant acceleration towards the Earth" I was confusing speed with acceleration when I clearly wasn't.
Oh, I see... you failed to mention the idea of a spherical (or technically hyperspherical) universe, this makes more sense in context.
The link appears to make an awful lot of assumptions... having said that, I can't see anything to outright say it's wrong, so it certainly seems valid to me.
@DigitalDuck
I think that we can both agree on the fact that all theories on the universe, its origin and where it is heading make an awful lot of assumptions.
Although we have made good progress in the last 50 years, there really hasn't been that great breakthrough that we've been waiting for. People are just 'Filling In The Gaps' to explain their own theories. Two examples of which are the
Dark Energy and Dark Matter issues which I personally think is bad science. I mean how can you possibly include something in a theory that may not even exist? [EDIT] However, I do understand the need to do this for experimental purposes but the theory itself should be proved.
Anyway. An interesting discussion. Thanks for the links that you posted earlier. Haven't had time to read them all yet but thanks.
I think that we can both agree on the fact that all theories on the universe, its origin and where it is heading make an awful lot of assumptions.
Although we have made good progress in the last 50 years, there really hasn't been that great breakthrough that we've been waiting for. People are just 'Filling In The Gaps' to explain their own theories. Two examples of which are the
Dark Energy and Dark Matter issues which I personally think is bad science. I mean how can you possibly include something in a theory that may not even exist? [EDIT] However, I do understand the need to do this for experimental purposes but the theory itself should be proved.
Anyway. An interesting discussion. Thanks for the links that you posted earlier. Haven't had time to read them all yet but thanks.
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True. Even relativity hasn't been proven, although many of the conditions it stipulates have been.
Well, all theories include things that haven't been proven to exist - after all, if they have been proven then they cease to become theories...
Neutrinos are a form of dark matter, and they've been detected - but so far I think they're the only form that have been. Most of the current known unknowns of the Universe are a result of gravity not being fully understood, and the two approaches of fixing that are changing our model of the Universe so it fits gravity, or changing our model of gravity so it fits the Universe. Dark matter's the former, and it's generally more widely accepted because it's simpler; there are alternative theories that try to challenge what we think we know about gravity.
And since this is probably getting too serious for most, here's a video of someone who really doesn't understand gravity.
Not at all - they probably won't add much now, but you never know. Thanks for staying civil about this.
Yes, there are two that I know of. Gravity bending light and the orbit of Mercury. Also, I understand that NASA still use newtonion physics rather than Einsteins physics where space flight is concerned.
That's interesting because I recently attended an astronomical meeting where the subject was discussed. The guest speaker informed us that they hadn't been detected yet even though scientists had spent millions trying to detect them under the sea. I'll have to find out more about this so that I can tell him next time we meet.
Hey no problem buddy. I'll always try and be civil. Nobody is correct all the time and you learn by what others say. We are only human
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Just one niggly little point - there's a common misapprehension that 'dark' stuff is some kind of fudge factor...
it isn't - rather, it's an inference, from an anomalous measurement; that is, one that doesn't conform to expectation. An inconsistency between observation and theory.
So in the case of dark matter, it's not some hypothetical entity invoked to fill the gaps, but rather a discrepancy between expected and measured values - star systems follow Kepler's laws, but galaxies apparently don't - and worse, some inexplicably moreso that others... so it's not even a particularly predictable anomaly.
So these are facts, not theories.
The hypotheses come in to play in trying to tie up these loose ends - is dark matter an actual form of matter, such as WIMPS, MACHOS or HALOs etc. etc. or is it a failure of classical laws at cosmological scales, requiring something like MOND to make sense of (has shown some predictive success just in the last week)..?
Dark energy, dark flow et al are likewise observed deficits in current models, not speculative tacked-on afterthoughts to milk academic funding, or something... their whole point of interest is precisely because they're the big questions at the cutting edge of cosmology - the limits of current knowledge.
Whichever prospective theories win out, it'll be because they better explain observations, and make accurate predictions for future measurements. Or, as DigitalDuck put it (top posts BTW), they're "known unknowns"...
it isn't - rather, it's an inference, from an anomalous measurement; that is, one that doesn't conform to expectation. An inconsistency between observation and theory.
So in the case of dark matter, it's not some hypothetical entity invoked to fill the gaps, but rather a discrepancy between expected and measured values - star systems follow Kepler's laws, but galaxies apparently don't - and worse, some inexplicably moreso that others... so it's not even a particularly predictable anomaly.
So these are facts, not theories.
The hypotheses come in to play in trying to tie up these loose ends - is dark matter an actual form of matter, such as WIMPS, MACHOS or HALOs etc. etc. or is it a failure of classical laws at cosmological scales, requiring something like MOND to make sense of (has shown some predictive success just in the last week)..?
Dark energy, dark flow et al are likewise observed deficits in current models, not speculative tacked-on afterthoughts to milk academic funding, or something... their whole point of interest is precisely because they're the big questions at the cutting edge of cosmology - the limits of current knowledge.
Whichever prospective theories win out, it'll be because they better explain observations, and make accurate predictions for future measurements. Or, as DigitalDuck put it (top posts BTW), they're "known unknowns"...
Also time dilation - it's what keeps GPS in-sync, among other things. I think NASA apply the time dilation aspect of relativity to Newtonian physics as it's the most pronounced effect over long periods, but space flight is still so slow that it has barely any effect whatsoever.
There was a recent controversy over neutrinos supposedly moving faster than the speed of light (turned out the cable wasn't plugged in properly... clearly they should've called IT support, it would've been the second thing they tried) - they've been known for a few decades now, but I think the point is that other forms of dark matter haven't yet been detected. In fact, I think neutrinos were discovered before the gravitational inconsistencies were...
Thanks! This is pretty much what I was trying to say - there's either something else we haven't accounted for, or we haven't accounted for everything correctly.
If it's a revision of gravity that's necessary, then personally I'm gunning for scalar-tensor-vector gravity theory. Aside from the fact it explains most of the stuff the presence of dark matter does, and matches observations almost as well, it also adds the possibility that gravity can, in certain circumstances, be a repulsive force as well as an attractive one, and I do like my symmetry. Repulsive gravity also offers an explanation for the acceleration of the expansion of the Universe.
My interpretation of it is as follows:
1. Quantum entanglement does not send information faster than light. When you observe 1 of the particles you cannot decide what the outcome will be, it is statistically determined. Yes, if anyone observes the entangled other particle far away an instant later that result will depend on the result from the first observation. But no information has travelled. You cannot use it to send any messages, as you cannot select the result. It is sorta the same as two observers taking pictures at a galaxy, but each is far away on opposite side of it. The instant they both look at the picture they have taken, they will both know that it is (for example) a spiral galaxy with 3 arms. None of them have communicated that information to each other though. Note here that if the light from the galaxy pictured would observe the light going the opposite way towards the other observer it would not measure its speed to be 2x speed of light, but measure it at 1x speed of light.
2. The galaxies are not flying away from each other. They are more or less standing still. It is the space between them that is expanding. So even though their positions in relation to each other is moving apart far faster than the speed of light they are not moving above light speed. The space expansion can be witnessed by light being red-shifted, due to space 'stretching' the fotons wave lengths as they travel through expanding space. This can also be used to see how far the light has traveled from the object when we observe it (also there is another source of redshifting, doppler redshift due to relativistic time contraction).
3. That the visible universe is uniform does not imply in any way that it is infinite, the jury is still out on that one. But it does imply that the universe is larger than the visible part (46 LY).
4. The example mentioned of 2 ships from two galaxies flying high speed away from each other is interesting. If they both fly from their galaxies at 75% of light speed and they could observe each other, they would not see the other ship at 150% light speed, not even 100%. Could be maybe 80% light speed, did not calculate it, just a guesstimate. This follows from relativity. Many counter intuitive things was discovered about our universe when relativity was discovered. For example if one observer see 2 simultaneous events, another might not even see them as happening at the same time, etc etc. Or time does not go at same speed as compared to another observer, eg. if a light foton could measure time, it would see no time pass from when it is created till it interacts with something, quite stunning if it travels halfway across the visible universe.
1. Quantum entanglement does not send information faster than light. When you observe 1 of the particles you cannot decide what the outcome will be, it is statistically determined. Yes, if anyone observes the entangled other particle far away an instant later that result will depend on the result from the first observation. But no information has travelled. You cannot use it to send any messages, as you cannot select the result. It is sorta the same as two observers taking pictures at a galaxy, but each is far away on opposite side of it. The instant they both look at the picture they have taken, they will both know that it is (for example) a spiral galaxy with 3 arms. None of them have communicated that information to each other though. Note here that if the light from the galaxy pictured would observe the light going the opposite way towards the other observer it would not measure its speed to be 2x speed of light, but measure it at 1x speed of light.
2. The galaxies are not flying away from each other. They are more or less standing still. It is the space between them that is expanding. So even though their positions in relation to each other is moving apart far faster than the speed of light they are not moving above light speed. The space expansion can be witnessed by light being red-shifted, due to space 'stretching' the fotons wave lengths as they travel through expanding space. This can also be used to see how far the light has traveled from the object when we observe it (also there is another source of redshifting, doppler redshift due to relativistic time contraction).
3. That the visible universe is uniform does not imply in any way that it is infinite, the jury is still out on that one. But it does imply that the universe is larger than the visible part (46 LY).
4. The example mentioned of 2 ships from two galaxies flying high speed away from each other is interesting. If they both fly from their galaxies at 75% of light speed and they could observe each other, they would not see the other ship at 150% light speed, not even 100%. Could be maybe 80% light speed, did not calculate it, just a guesstimate. This follows from relativity. Many counter intuitive things was discovered about our universe when relativity was discovered. For example if one observer see 2 simultaneous events, another might not even see them as happening at the same time, etc etc. Or time does not go at same speed as compared to another observer, eg. if a light foton could measure time, it would see no time pass from when it is created till it interacts with something, quite stunning if it travels halfway across the visible universe.
Short answer... No. Lightspeed is a constant 'c', and as such using Einsteinian laws remains the same throughout the multiverse. If you were to sit at any point at our galaxys edge with a sufficiently powerful telescope you would see clear across to the other edge- barring of course nebulae, anomolies which blur or distort vision, and gravitational bending .
Hope that helps.
also there is a theory that cosmic expansion is powered by 'dark' energy, which brings up other ideas and theories. Have you seen the NASA warpship? The theory is that it moves by 'warping' space using amounts of energy, like when you place a toy in the sink and drop small amounts of detergent into the water behind it. And in a cool way it looks like the Vulcan starships from Enterprise.
The expansion of the universe has always puzzled me: gravity is an attractive force, Brownian motion doesn't seem to be sufficient to push things apart, and the expansion is apparently speeding up, so it's not just a leftover "explosion". There must be some really big forces we have no idea about? I'm just an amateur who has read lots of books, but it feels like we know lots about the minutiae, and can do the maths very well, but have no clue about what is all really means (cf Copenhagen interpretation).
String theory and supersymmetry are good, but we are still missing something *huge* in our understanding of the universe. Maybe we can never "understand" it in any meaningful way.
Still, it's good to make your brain hurt!
Hmm firstly, prove they're the same throughout the multiverse, prove there is one... however..
Lightspeed isn't constant.. Gravity can change/warp/bend and indeed in the case of a black hole have such a force that light isn't fast enough to escape the field. At least that's what was described to me when I was at stargazing live in January.
Or in the words of Terry Pratchett, Light isn't the fastest thing around, because you'll always notice Dark was there before it.