The speed of light; another perspective.

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Expand view Topic review: The speed of light; another perspective.

Re: The speed of light; another perspective.

by Beyond » Mon Aug 23, 2010 11:59 am

StarstruckKid wrote:Here's where we're still stuck: the second, a completely earth-bound, human-based measurement. IMHO, if we sent the Bftsplkians instructions to build a cesium clock so they could use our measurement of a second, after they got through laughing raucously, they would call us a bunch of arrogant, self-centered children and tell us not to call back until we could talk to them like cosmic adults. We are mired in the League of Extraordinary Gentlemen's metric system and our own self-importance, and would be seen as such by any civilization with any degree of sophistication.

I've thought further about the topic in the last week, and I make this suggestion in all seriousness: recognize the metric system for the anachronism it is and toss it. I'm not the first person to have a glimmer of this, as witnessed by the attempts at universality on Voyager (which, after being poisoned by the first Star Trek movie, will always be known to me as Veeger).

All technologically advanced 'races' will, like us, recognize c as a universal unit of speed. Let's do as I suggested above and begin to express speeds accordingly, My speed of 90 nano-c's was calculated as approximately equivalent to 60 mph.

All technologically advanced civilizations will recognize the hydrogen atom as the most basic and thus a logical basis for a system of measurement. The mass of H is the unit of mass. The wavelength of Lyman-alpha is the unit of distance. The time required to go one Lyman-alpha length is the unit of time. The frequency of Lyman-alpha is the unit of frequency.

These measurements would be scaled to useful sizes, the comparison of which would allow us to share information about things like our own relative sizes.

Class exercise: derive the rest of the system.

Think you're done? Bet you used base 10 to scale everything. Nope, ten fingers, human-based. The most basic number is 2. Go back and redo. But I'll give you a break: those lines of 1's and 0's will be as long as your arm, so use a natural scaling like 2 ^2 ^2 ==> 16, conveniently close to the 10 we're used to, and a likely compromise in any advanced technological civilization.

Now we can talk to the Bftsplkians and be on their level. Scaled appropriately, of course. :)
On my hands i have ten digits--eight fingers and two thumbs. So i would very much like to see at least a picture of those humans with ten fingers.

Re: The speed of light; another perspective.

by Chris Peterson » Mon Aug 23, 2010 12:26 am

StarstruckKid wrote:Here's where we're still stuck: the second, a completely earth-bound, human-based measurement...
We choose units that are convenient for us. Although they need to have a connection to something physical that can be used as a reference, they are otherwise arbitrary. We choose our number system in the same way, and ten is a perfectly reasonable choice. If I were going to change it, I'd go to 16 rather than 2. But there is no more reason to change our number system than there is to change the meter, gram, or second.

If we're going to invest energy in this, far better to simply make sure everybody uses the same system. And I'm talking about right here on Earth. Any aliens we encounter sophisticated enough to care... won't care.

Re: The speed of light; another perspective.

by StarstruckKid » Mon Aug 23, 2010 12:10 am

Here's where we're still stuck: the second, a completely earth-bound, human-based measurement. IMHO, if we sent the Bftsplkians instructions to build a cesium clock so they could use our measurement of a second, after they got through laughing raucously, they would call us a bunch of arrogant, self-centered children and tell us not to call back until we could talk to them like cosmic adults. We are mired in the League of Extraordinary Gentlemen's metric system and our own self-importance, and would be seen as such by any civilization with any degree of sophistication.

I've thought further about the topic in the last week, and I make this suggestion in all seriousness: recognize the metric system for the anachronism it is and toss it. I'm not the first person to have a glimmer of this, as witnessed by the attempts at universality on Voyager (which, after being poisoned by the first Star Trek movie, will always be known to me as Veeger).

All technologically advanced 'races' will, like us, recognize c as a universal unit of speed. Let's do as I suggested above and begin to express speeds accordingly, My speed of 90 nano-c's was calculated as approximately equivalent to 60 mph.

All technologically advanced civilizations will recognize the hydrogen atom as the most basic and thus a logical basis for a system of measurement. The mass of H is the unit of mass. The wavelength of Lyman-alpha is the unit of distance. The time required to go one Lyman-alpha length is the unit of time. The frequency of Lyman-alpha is the unit of frequency.

These measurements would be scaled to useful sizes, the comparison of which would allow us to share information about things like our own relative sizes.

Class exercise: derive the rest of the system.

Think you're done? Bet you used base 10 to scale everything. Nope, ten fingers, human-based. The most basic number is 2. Go back and redo. But I'll give you a break: those lines of 1's and 0's will be as long as your arm, so use a natural scaling like 2 ^2 ^2 ==> 16, conveniently close to the 10 we're used to, and a likely compromise in any advanced technological civilization.

Now we can talk to the Bftsplkians and be on their level. Scaled appropriately, of course. :)

Re: The speed of light; another perspective.

by Markus Schwarz » Thu Aug 19, 2010 10:57 am

StarstruckKid wrote: In terms of defining units of measurement, there would seem to be a good argument for using one of the emission lines of hydrogen (the most basic element) for a unit of frequency/time
Replace hydrogen with cesium and you have the SI definition of a second, which is defined as the 9 192 631 770th multiple of the period of a certain emission line of cesium. I am no experimentalist, but the choice of cesium over hydrogen is most likely due to the fact that it is easier to archive the required precision. Since the speed of light in vacuum is defined to be 299 792 458 meters per second you have that one meter is the distance traveled by in the 299 792 458th part of a second. While the actual numbers might seem ridiculous, they are based on well-defined standards that can be reproduced everywhere.

So, sending the aliens these definitions, they will be able to reproduce our SI units and derive the conversion factors to their units. Most likely they will have a similar modern definition for a frbzzle which they could send us, so we would be able to reproduce their units. The only problem is our kilogram, which is defined as the mass of the kilogram prototype in Paris...

Besides, I think it would be interesting to the Bftsplkians to know our "human-based" units, because it would give them an idea about our everyday environment (The human size is about one meter.). And since our SI system is based on standards that can be reproduced everywhere, I don't see a problem.

By the way: your suggestion was used on Voyager's Golden Record to give aliens the time scale to which all times on the plate are referring.

Re: The speed of light; another perspective.

by StarstruckKid » Tue Aug 17, 2010 2:40 am

Henning Makholm wrote:...Or transact all our business in natural units.
That is what I was aiming at. Most of us are caught up in definitions of elemental quantities in tems of completely relative units. Throwing all that out, as was attempted with the Hz unit, clears the air of misconceptions such as a 'light year' being somehow bound to the length of a planet's orbit, or the speed of light being being somehow tied to our derived units like the second. Even the choice of a cesium clock for a time standard is arbitrary, and the resulting definition is still some huge number that adds up to a second, for pete's sake.

In terms of defining units of measurement, there would seem to be a good argument for using one of the emission lines of hydrogen (the most basic element) for a unit of frequency/time (a 'hydro-tick'), and its associated wavelength (an 'angst') for the basis of a unit of length. Thus completely stepping away from ancient and human-based things like the second. I will drive my car at 90 nano-cs for a distance of (i'm not going to try to calculate this one) some-number-of giga-angsts, and get there in some-other-number-of giga-hydro-ticks.

Now we can communicate with those Bftsplkians.

Re: The speed of light; another perspective.

by swainy » Tue Aug 17, 2010 12:47 am

Chris Peterson wrote:
swainy wrote:I do understand Chris, I am just playing with it. 5 years orbiting our black hole, is ten years on Earth, Vice verse. Some what different with the speed of light. Its what the paradox is all about. But your not going to show me how, Time is not effected by Mass in any meaningful way ? Huh?
There is no paradox. Only something that seems contrary to our everyday experience.
Remember you heard it from me first. :wink:

tc

Re: The speed of light; another perspective.

by Chris Peterson » Tue Aug 17, 2010 12:36 am

swainy wrote:I do understand Chris, I am just playing with it. 5 years orbiting our black hole, is ten years on Earth, Vice verse. Some what different with the speed of light. Its what the paradox is all about. But your not going to show me how, Time is not effected by Mass in any meaningful way ? Huh?
There is no paradox. Only something that seems contrary to our everyday experience.

Re: The speed of light; another perspective.

by swainy » Tue Aug 17, 2010 12:32 am

Chris Peterson wrote:There is no way to tell if your local time is somehow "fast" or "slow"; that doesn't even have any meaning.
We are getting somewhere, :wink:

I do understand Chris, I am just playing with it. 5 years orbiting our black hole, is ten years on Earth, Vice verse. Some what different with the speed of light. Its what the paradox is all about. But your not going to show me how, Time is not effected by Mass in any meaningful way ? Huh?

tc

Re: The speed of light; another perspective.

by Chris Peterson » Tue Aug 17, 2010 12:07 am

swainy wrote:No, Not according to Hawking. Time travel is possible, Either way. (With the Tech). You don,t get out of it that easy. The Clocks are different, I saw them with my own eyes, Its been proven. So I will ask again. What is the connection, Between Time And Mass?
You don't understand Hawking, either. Or what you get from him you get from some of his popular work, which is technically wrong.

Time is not affected by mass. Two different reference frames in different gravitational fields will each see time in the other moving at different rates. That's what we learn from relativity. It doesn't mean that time itself is affected. Comparing time between two non-inertial frames is non-trivial. But the important point is that it is a comparison. From within either frame, time flows exactly as always. There is no way to tell if your local time is somehow "fast" or "slow"; that doesn't even have any meaning.

Re: The speed of light; another perspective.

by swainy » Mon Aug 16, 2010 11:57 pm

Chris Peterson wrote: So Why does a bigger Mass, Slow time down?


It doesn't. You don't understand the most basic aspect of different reference frames. Time always flows the same. It only appears different from different frames.
No, Not according to Hawking. Time travel is possible, Either way. (With the Tech). You don,t get out of it that easy. The Clocks are different, I saw them with my own eyes, Its been proven. So I will ask again. What is the connection, Between Time And Mass?

tc

Re: The speed of light; another perspective.

by Chris Peterson » Mon Aug 16, 2010 11:45 pm

swainy (tc) wrote:
Chris Peterson wrote:Gravity certainly does not "control time".
Are you sure about that?
Yes.
So Why does a bigger Mass, Slow time down?
It doesn't. You don't understand the most basic aspect of different reference frames. Time always flows the same. It only appears different from different frames.

Re: The speed of light; another perspective.

by swainy (tc) » Mon Aug 16, 2010 11:35 pm

Chris Peterson wrote:Gravity certainly does not "control time".
Are you sure about that? So Why does a bigger Mass, Slow time down? To A point, Where T=0 ? What are the Connections that make this so? Why would there be, any connections?

tc

Re: The speed of light; another perspective.

by Henning Makholm » Mon Aug 16, 2010 10:55 am

StarstruckKid wrote:To make matters worse, our planets have a large differential velocity, so the Doppler effect prevents using the frequency of the radio wave as a reference.
....
So then we measure how long it takes our radio signal to go to Bftsplk and back,(they'd have to have a repeater pointed back at us), we tell them it was x seconds, they tell us it was y hhrrrrckkks, and voila! we now know how many seconds per hhrrrrckkk.
If we have a large differential velocity, there will be relativistic time dilation to take into consideration, so the two ends will not be measuring the same amount of time. (In fact, due to the mutual velocity, successive radio messages will not even have the same distance to travel).

Much better simply to send them the SI definitions of the second and meter, and have them build a cesium clock to get their own realization of the second. Or transact all our business in natural units.

Re: The speed of light; another perspective.

by StarstruckKid » Mon Aug 16, 2010 2:18 am

I think what wonderboy was getting at was the difficulty of communicating with the inhabitants of another world how each side measures fundamental quantities like the speed of light (c). Not only are inertial frames of reference all local, so are systems of measurement.

Suppose we managed to establish radio contact with the inhabitants of Bftsplk and we want to talk about the speed of light. Here on Earth we measure it in distances based on things like the diameter of the planet (the meter) or the length of the King's royal pedal extremities (the foot) extended to how many times the King can put one foot in front of the other before he gets tired (5280, a mile). Our time measurements are based on the rotational speed of the Earth and the apparent size of the Sun (and Moon). Since the angular size of the Sun is about 1/2 degree, it takes almost exactly 2 minutes to pass a given fixed reference point.

But on Bftsplk, the unit of length is based on the size of the average Bftsplkian's facial tentacle (very democratic beings, those Bftsplkians) or a frbzzle, and their unit of time is based on how long it takes the average Bftsplkian to fall a distance of 1717 (did I mention they have 17 tentacles?) frbzzles, or a hhrrrrckkk. Also did I mention they are about the size of a terrestrial palmetto bug? They have determined that the speed of light is 98-13/17 vrsook (I won't attempt to explain their numeric system) frbzzles per hhrrrrckkk.

To make matters worse, our planets have a large differential velocity, so the Doppler effect prevents using the frequency of the radio wave as a reference.

BUT, we can get away from local units of measure, and dispense with defining c in those terms by turning the problem upside down. Start with the fundamental constant, c, and work backwards. Much as we dispensed with the old cycles per second yardstick with frequency and now call one cycle per second a Hertz (not a fundamental quantity, however, it's still based on the second).

So then we measure how long it takes our radio signal to go to Bftsplk and back,(they'd have to have a repeater pointed back at us), we tell them it was x seconds, they tell us it was y hhrrrrckkks, and voila! we now know how many seconds per hhrrrrckkk.

Now we just need to rework our road signs. I will no longer be driving 60 miles per hour, it will be, oh, about 90 nano-c's, if I've figured right.

Michael

Re: The speed of light; another perspective.

by swainy » Sat Jul 03, 2010 9:29 pm

Chris Peterson wrote:Gravity certainly does not "control time". Whether the speed of gravity can be something other than c is an interesting question- essentially, it is asking if there is something like an index of refraction for gravity. I don't know that anybody can answer that beyond speculation. I very much doubt that anything modifies the propagation speed of gravity enough to produce anything but very subtle observational effects, however.
I,m sorry to say, that I have a strong belief that Gravity is connected to Time. But not in this thread.

But, I would like to say, you have made my day, by posting the above :roll: Thanks Chris.

tc

Re: The speed of light; another perspective.

by Chris Peterson » Sat Jul 03, 2010 8:50 pm

swainy wrote:I don,t no how you can say that with any form of certainty. Check out the Apod pillars of creation. http://antwrp.gsfc.nasa.gov/apod/ap100328.html Then tell me our universe has not changed in transparency in 6 billion years.
I didn't say that. What I said is that most of the Universe is largely empty space, and theory tells us that has been the case since very shortly after the BB. Even in regions like the Pillars of Creation, what you see would be considered a hard vacuum in any laboratory. It isn't a medium with a refractive index different than one, which means the speed of light is not affected by it.
But any hows, how can light be a constant if it can be slowed down?
As previously noted, the speed of light is not a constant. That belief is a common misconception. There is a universal constant called c, which shows up in many physical theories. The velocity of light in a vacuum happens to be equal to c. That does not mean that c is the speed of light, and it does not mean that the speed of light is a constant. The index of refraction of a medium defines the amount by which light travels slower than c.
Does this mean something can slow gravity down? and as gravity may control time, does that mean we can physically manipulate almost anything?
Gravity certainly does not "control time". Whether the speed of gravity can be something other than c is an interesting question- essentially, it is asking if there is something like an index of refraction for gravity. I don't know that anybody can answer that beyond speculation. I very much doubt that anything modifies the propagation speed of gravity enough to produce anything but very subtle observational effects, however.

Re: The speed of light; another perspective.

by swainy » Sat Jul 03, 2010 8:35 pm

Chris Peterson wrote:Space is neither cold, nor full of gas. When you play around with the velocity (or phase velocity) of light in a Bose-Einstein condensate, you are working at a temperature of microkelvins. The Universe is bathed with radiation that is 2.7 K - millions of times hotter than you need for these effects. In addition, most of the Universe is nearly empty of gas. The refractive index of any region of the Universe is so close to 1 that we can safely say that every photon we record from the CMB is traveling at c.
Just for the interest, and the reading only.
I don,t no how you can say that with any form of certainty. Check out the Apod pillars of creation. http://antwrp.gsfc.nasa.gov/apod/ap100328.html Then tell me our universe has not changed in transparency in 6 billion years. Bering in mind, Class 1,? and 2 generation stars. http://www.universetoday.com/2010/03/03 ... milky-way/ Creating more pillars of creation more nebula gas dust etc etc. And then times this by billions into a smaller 8 billion year old universe. somebody once told me. There are more stars in the universe than grains of sand on every beach. That,s just stars, now add all 8 planets for every star, and billions on tons of other size rocks etc etc. But I don,t need all the grains on every beach, I just need a hand full. Because with just a hand full I can,t see the skin of my palm. So how can a little photon, travel 14 billion light years x 6 trillion miles of gas, dust and all other stuff we have no knowledge of? There may be no gas and dust there now. But five billion years ago?

But any hows, how can light be a constant if it can be slowed down? Does this mean something can slow gravity down? and as gravity may control time, does that mean we can physically manipulate almost anything?

tc

Re: The speed of light; another perspective.

by Chris Peterson » Sat Jul 03, 2010 3:15 pm

The Code wrote:So reports say light could be slowing down, over billions of years.
That's not what is being suggested. The article refers to the (slim) possibility that c has changed over time. This has nothing to do with the speed of light, other than the fact that the fastest light can travel is c. There is no lower limit on the speed of light.
And scientist can actually stop light by Freezing it through Very cold gas... So, I here space is very cold, And Full of Gasses. Can you actually tell, from looking at any part of the CMB the speed at which you are seeing those photons traveling at?


Space is neither cold, nor full of gas. When you play around with the velocity (or phase velocity) of light in a Bose-Einstein condensate, you are working at a temperature of microkelvins. The Universe is bathed with radiation that is 2.7 K - millions of times hotter than you need for these effects. In addition, most of the Universe is nearly empty of gas. The refractive index of any region of the Universe is so close to 1 that we can safely say that every photon we record from the CMB is traveling at c.

Re: The speed of light; another perspective.

by The Code » Sat Jul 03, 2010 2:17 pm

Chris Peterson wrote:
swainy wrote:No bite yet then?
Perhaps because there's really no story. There have been occasional suggestions over the years that various physical constants are not actually constant. This is another such claim. It is highly speculative and poorly tested. At the moment, there is a vast amount of evidence that suggests c actually is a constant, and hasn't changed since the current physical laws crystallized out of the Big Bang. The possibility remains interesting, but there's really nothing at this point to discuss.
So reports say light could be slowing down, over billions of years. And scientist can actually stop light by Freezing it through Very cold gas. :

http://www.sciencentral.com/articles/vi ... =218392702
http://physicsworld.com/cws/article/news/3013

So, I here space is very cold, And Full of Gasses. Can you actually tell, from looking at any part of the CMB the speed at which you are seeing those photons traveling at?

tc

Re: The speed of light; another perspective.

by Chris Peterson » Fri Jul 02, 2010 10:28 pm

swainy wrote:No bite yet then?
Perhaps because there's really no story. There have been occasional suggestions over the years that various physical constants are not actually constant. This is another such claim. It is highly speculative and poorly tested. At the moment, there is a vast amount of evidence that suggests c actually is a constant, and hasn't changed since the current physical laws crystallized out of the Big Bang. The possibility remains interesting, but there's really nothing at this point to discuss.

Re: The speed of light; another perspective.

by swainy » Fri Jul 02, 2010 10:15 pm

swainy wrote:Next thing you will be saying is, Is the speed of light slowing down. Oops That's another thread sorry.

http://www.opfocus.org/index.php?topic=story&v=8&s=4

tc
No bite yet then? What does the link, change in the universal constant?

I have been looking into this. I have read some very interesting things on this. Post pending tray?

tc

Re: The speed of light; another perspective.

by Chris Peterson » Fri Jul 02, 2010 2:13 am

makc wrote:Europe?
Just an example <g>.

Re: The speed of light; another perspective.

by swainy » Fri Jul 02, 2010 1:55 am

Check out the Grey patches. You trying to tell us something?

tc

Re: The speed of light; another perspective.

by makc » Fri Jul 02, 2010 1:37 am

Chris Peterson wrote:...somebody in Europe goes into the store and buys 100g of cheese...
Europe?
Image :wink:

Re: The speed of light; another perspective.

by swainy » Fri Jul 02, 2010 1:22 am

Chris Peterson wrote:
wonderboy wrote:I'm not arguing over the speed of light, merely its understanding to someone with different understandings of distance and yearly orbits on a different planet.
I'm afraid I don't see how the use of different units produces a different understanding. If I go into the store and buy a quarter pound of cheese, and somebody in Europe goes into the store and buys 100g of cheese, I expect each of us has exactly the same sense of how much we are getting. If I use their units, or they use mine, we both might "know" how much we're getting but have a different sense- that's just unfamiliarity with the units. But that doesn't apply to us and aliens, each using our comfortable units of stellar distance.
Every language can be translated, To English. As Chris said, Physics is much the same. The numbers may appear different but they are not. Just a different language.

tc

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