# Thread: The speed of light.

1. I figured I would start another subject that I'm sure everyone will look at me and go..huh? What's this guy smoking

Light for some reason only goes so fast, some will say it's because it has a certain amount of mass and that based on it's level of energy can't go any faster.

A few things.

First, does it have mass? Can we get to a final answer on this one?

Does it in fact travel exactly at the same speed every single time? If so wouldn't this make it perfect?

I'll toss in my thoughts just because.

To the first question I would have to say that light having mass would explain it's limited speed.

To the second I would have to conclude that there must be variations in the speed of light as nothing is perfect.

So, keeping the concept of time 100% out of this thread...let's talk about light.

2.

3. light does not have mass, because the more mass an object has is the slower it will travel or the more mass it will need to go faster hence the fastest anything can go is if it had no mass right.

the speed of light does vary, exept in a vacuum where it travels at a constant speed which can be measured as the same from all observers, when it is traveling in different mediums.
light traveling through water will be slower than light traveling through air.

4. The speed of light depends on the electric and magnetic permeability and permittivity (basically just the resistance to changes in electric or magnetic field strength) of the space that the light is traveling through. In fact, the speed of light in any material can be derived exactly from the permeability and permittivity using the Maxwell wave equations.

Light will always, so far as we know, go exactly the same speed in vacuum. When it passes through materials it goes somewhat slower, since the permittivity and permeability is higher.

As for lightspeed not being constant because “nothing is perfect,” you should keep in mind that many things are always exactly the same. The mass on a neutron is always “perfectly” the same. The charge of a proton is always the same. The spin of an electron is always the same. Similarly, the speed of light in vacuum is always the same.

5. As for lightspeed not being constant because “nothing is perfect,” you should keep in mind that many things are always exactly the same. The mass on a neutron is always “perfectly” the same. The charge of a proton is always the same. The spin of an electron is always the same. Similarly, the speed of light in vacuum is always the same.
Good point.

One has to wonder why the speed of light in a vacuum is what it is, what characteristics defined this speed? Is it the wavelength? One also has to wonder why there is nothing faster, or perhaps there is something faster that we simply don't have a device or means to detect?

I also have to wonder what is the speed of gravitational force. In other words if one were to materialize a large body, how long would it take for the gravitational force to expand outward and impact objects?

6. I'm a non-scientist. In fact you'd be quite justified in referring to me as an idiot in that respect. But I found a book on my shelf which tells me, if I'm not mistaken, that all electromagnetic waves travel at the same, constant speed of light (in vacuum). Evidently, that goes for gravitational waves too. The other interesting item is that the colour spectrum, as in a rainbow, results from the fact that different wavelengths of light are at different energy levels, and are therefore slowed down to different degrees. Please correct me if this is wrong.

7. Originally Posted by (In)Sanity
So, keeping the concept of time 100% out of this thread...let's talk about light.
Can you tell me the speed of light, even approximately, without including the concept of time? No, of course not. Why would you wnat to leave out time, without which it is not very meaningful to talk about the "speed" of light.

8. Originally Posted by wallaby
the speed of light does vary, exept in a vacuum where it travels at a constant speed which can be measured as the same from all observers
I think that the only concrete evidence that light travels at a constant speed is the fact that is can be measured as the same from all observers.

9. Originally Posted by Hermes
Originally Posted by (In)Sanity
So, keeping the concept of time 100% out of this thread...let's talk about light.
Can you tell me the speed of light, even approximately, without including the concept of time? No, of course not. Why would you wnat to leave out time, without which it is not very meaningful to talk about the "speed" of light.
You can still reference the speed of light without time. You can base it on the changes in other forms of matter.

Light manges to cover this much distance while sound covers this much distance just before we stop it. Or light goes this far after this many oscillations of an atom. Time after all is just a reference to other changes. The light will reach it's destination as soon as this water boils.

Sorry, but time is just a man made reference to changes.

10. Originally Posted by (In)Sanity
Originally Posted by Hermes
Originally Posted by (In)Sanity
So, keeping the concept of time 100% out of this thread...let's talk about light.
Can you tell me the speed of light, even approximately, without including the concept of time? No, of course not. Why would you wnat to leave out time, without which it is not very meaningful to talk about the "speed" of light.
You can still reference the speed of light without time. You can base it on the changes in other forms of matter.

Light manges to cover this much distance while sound covers this much distance just before we stop it. Or light goes this far after this many oscillations of an atom. Time after all is just a reference to other changes. The light will reach it's destination as soon as this water boils.

Sorry, but time is just a man made reference to changes.
It may be that I need some coffee, but I can't catch your drift. When you refer to changes, you refer to time. When you refer to oscillations, you refer to cycles per second. I can't see how you can make any reference to the transmission of light without including a reference to time in one way or another. As I said, maybe I'm just dumb today. Please come back on this. Thanks

11. It may be that I need some coffee, but I can't catch your drift. When you refer to changes, you refer to time. When you refer to oscillations, you refer to cycles per second. I can't see how you can make any reference to the transmission of light without including a reference to time in one way or another. As I said, maybe I'm just dumb today. Please come back on this. Thanks Smile
Well it's simple.

Changes in the physical universe happen all the time. These changes happen in a certain order to produce some desired effect or cause other changes to be set in motion. We have labeled the duration of a given change with the label of "time". Time however is not needed for the change to occur. The atoms (etc) will interact at their given fixed durations to yeild the resulting effect.

Does it take time to boil water? Not really it just takes the right amount of reaction. We place the label of time on this change in order to better work with it. Otherwise we would run around saying I'll see you as soon as these 3 eggs boil

I'm not sure why people are finding my concept of the world without time hard to grasp. Time being a concept we use to measure change is very handy, it however is not needed for change to occur. Change happens at the rate set by the laws of physics. We just so happen to base these changes on other changes to establish a relationship between those intervals. Right now our scale is based on how long it takes for the planet to rotate once. The planet would still rotate regardless.

If everything in the universe slowed down except for light, would we not conclude that light had sped up? In reality all the things we use to base the speed of light on have just slowed down.

If light were to speed up would we think that everything else slowed down?

So time is not needed to measure the speed of something or for that something to happen, we need other changes to calculate the amount of "time" it takes for changes to happen.

What is there was only one thing and nothing else. If the only thing that existed was light. How fast is it going? Without other changes around we would not be able to measure it, and our concept of time would not exist. If we had bursts of light then we would use that change to determine the interval and the relative speed. So it takes change to measure change, making "time" just mans way of dealing with the relationship between these changes.

Confusing, perhaps...it's really pretty simple if you push certain things out of the way. It makes it no less valid.

12. (In)Sanity---I accept that you're opposed to the use of the word time (great, maybe you can just pop along and explain it all to my boss). But seriously, you are right of course. Time is indeed the word (in English, at least) that we apply to the dimension via which the three dimensions of space proceed from past to future, and possibly occasionally, according to such great scientists as the late Richard Feynman, from future to past. The fact is that we need to have a handle on this feature of reality. It has a different name in every language, but it's universally acknowledged that a name is required, just as a name is required for all else. Furthermore, consider the work of scientists and mathematicians. This, also, is dependent on a symbol representing what you call "duration" and "interval". I wonder why it is that you seem happy to use the latter two words.

This is from Merriam-Webster’s Collegiate Dictionary:

Time
Function: noun
a : the measured or measurable period during which an action, process, or condition exists or continues : duration
b : a nonspatial continuum that is measured in terms of events which succeed one another from past through present to future

I apologise if I've missed your point. I'd like to continue, but I'm afraid it's time for my beauty sleep :-D

13. It's all cool, I'll drop the time issue. I just don't like how some people feel it's an object. I'm not saying most people do, just many. I think it's important that people understand what they are dealing with.

That being said I have no problem at all with it's "correct" use. When people start talking about warping time, freezing time, traveling in time..etc then I get a bit squeamish.

I think the people I have been discussing this with have a firm grip on the situation.

14. (In)Sanity___ Yes, I understand your feelings about this. This universe certainly keeps us guessing. How about starting another (related?) topic - "the nature of consciousness"

15. Originally Posted by (In)Sanity
You can still reference the speed of light without time.

Sorry, but time is just a man made reference to changes.
Sorry, but the second statement here lends zero support to the first statement. Can you give a concrete example?

16. Originally Posted by (In)Sanity
I just don't like how some people feel it's an object. I'm not saying most people do, just many. I think it's important that people understand what they are dealing with.
I find it interesting that you have such a bizarre understanding of the concept of time, and yet you don't like it when people don't share your concept. If you really think that it is important that people understand what they are dealing with, then why not start with yourself and learn what time is, rather than speculating as you do and then getting upset when others do not share your quite unusual conclusions.

That being said I have no problem at all with it's "correct" use.
Which you do not yet seem to understand.

17. Originally Posted by Hermes
Originally Posted by (In)Sanity
I just don't like how some people feel it's an object. I'm not saying most people do, just many. I think it's important that people understand what they are dealing with.
I find it interesting that you have such a bizarre understanding of the concept of time, and yet you don't like it when people don't share your concept. If you really think that it is important that people understand what they are dealing with, then why not start with yourself and learn what time is, rather than speculating as you do and then getting upset when others do not share your quite unusual conclusions.

That being said I have no problem at all with it's "correct" use.
Which you do not yet seem to understand.
I understand time very well, it's very simple. I know what it is, and I know what it is not. Certain people have done us an injustice by making it appear to be something it is not. It's not something magical or mythical. It has a solid base on the physical world, yet it's not a physical object. It can't be independently manipulated. It can't exist without the presence of matter. It also makes for good story and some good movies

For the record I've never been upset once that people don't share my views. If you look closely I agree with 95% of what people say about time, I just split hairs to define things a little more. Trust me I'm not going against the grain here, I'm just making sure the concept of time is not misused in context.

So If I object when people start talking about time travel or the warping of time, etc then please forgive me. I dislike things that have zero basis in reality. I find they don't help in the progression of mankind, they do just the opposite.

So the next time I hear someone talking about slowing down time by traveling at the speed of light I'll be sure to point out that you have to slow down matter to an equal degree as well.

But hey, what do I know

18. not entirely true.

matter traveling at the speed of light will experience a slowing down of time while moving at the fastest speed.

19. Originally Posted by wallaby
not entirely true.

matter traveling at the speed of light will experience a slowing down of time while moving at the fastest speed.
This statement is 100% illogical. You can not have time without movement, movement comes from matter. So unless your also factoring the forward velocity as being part of that movement in order for time to slow the internal workings of matter must also slow. Notice I said the internal workings and not the forward velocity.

20. Originally Posted by (In)Sanity
I understand time very well, it's very simple. I know what it is, and I know what it is not.
It is interesting that you say this. Your ideas about time are unique, such that if you truly understand what time is then most if not all scientists of the world are wrong. How is it that you are so sure of your understanding, such that you claim it to be simple, yet only you understand the true nature of time?

21. Originally Posted by (In)Sanity
You can not have time without movement
you state this as a fact.
i am not even in high school physics yet so please explain the theory that states this in laymans terms please.

any evidence would be nice too.

22. Interesting URL:
http://en.wikipedia.org/wiki/Time

"What is time? If nobody asks me, I know; but if I were desirous to explain it to one that should ask me, plainly I know not." - Augustine of Hippo

"Life holds one great but quite commonplace mystery. Though shared by each of us and known to all, seldom rates a second thought. That mystery, which most of us take for granted and never think twice about, is time." - Michael Ende

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