High School Is the Speed of Light Affected by Human Measurement Methods?

[Chris Miller]

Sorry, I should have been more specific. I meant that you need to understand the current body of knowledge within the domain that you wish to expand. Clearly you cannot know everything in every field, but wherever you seek to expand the body you must first learn it.

Sounds reasonable. Thanks. But aren't all the domains kind of intertwined or interconnected?

 

[Chris Miller]

Impossible. If you took all of the mass-energy in the observable universe and converted it to the kinetic energy of your body, you would still not be this close to c.

How small do you think I'd need to be for a few hundred gigatons to get me there?

 

[phyzguy]

How small do you think I'd need to be for a few hundred gigatons to get me there?

Why don't you try to do the calculation?

 

[Ibix]

Yay! I guessed one right. So, 100 years pass on Earth in 1 Planck interval of my time. I wonder, how much would the u would expand in my next second?

The "hundred years" bit is flexible and depends on your choice of synchronisation convention. And you are moving into GR territory with talk of the universe (is it really too much trouble for you to write the whole word?) expanding. So the answer is "it depends". The universe around you would be cold and dark by the time one second passed for you, however.

Note that @phyzguy's point about energy consumption makes this purely academic.

 

[dm4b]

What Dale is explaining is the difference between a number like c, which has units or dimensions, and a unitless or dimensionless number like pi or the fine structure constant. The number c will depend on the units you use to measure it. It is a different number in meters/second than it is in miles/hour. By contrast, a number like the α, the fine structure constant, has a value of about 1/137, and this number has no units, so we say it is "dimensionless". I will get the same number regardless of the system of units I use to measure it. Another example is the mass of the electron, which has units and depends on what units you use. However, the ratio of the mass of the proton to the mass of the electron is about 1836, and is independent of the units you use.

This a very clear and lucid explanation. I still can't help but think it's getting lost in semantics, at least as far as related to what the OP is asking. There are physical photons out there in the real world that behave a certain way. Whether, or not, this behavior is consistent, constant, or w/e, has nothing to do with how we choose to define c. Likewise, with the mass of an electron.

 

[Chris Miller]

Why don't you try to do the calculation?

found the formula for determining the Lorentz factor for ~c (which I still have to compute for the length foreshortening mentioned) and for determining KE to accelerate a specified mass to that. My compiler doesn't support the necessary floating point accuracy so I'd also have to convert the problem to huge integer arithmetic... and then solve for mass. Fun exercise. You're probably way more qualified to guesstimate.

 

[Chris Miller]

The "hundred years" bit is flexible and depends on your choice of synchronisation convention. And you are moving into GR territory with talk of the universe (is it really too much trouble for you to write the whole word?) expanding. So the answer is "it depends". The universe around you would be cold and dark by the time one second passed for you, however.

Note that @phyzguy's point about energy consumption makes this purely academic.

Thanks. Figured the universe (sorry, as a programmer I tend to use variables more than I should maybe) would blink out for me at that velocity. Interesting that my space-time frame could impact the entire universe like that.

 

[jbriggs444]

Whether, or not, this behavior is consistent, constant, or w/e, has nothing to do with how we choose to define c. Likewise, with the mass of an electron.

Whether c changes has everything to do with what we mean when we ask whether "c changes". What physical experiment can you do to compare c at one time and place with c at another time and place? For instance, what unchanging standard will you cart around to do your speed tests with?

And what makes you think that it is c that is changing rather than your standard?

 

[Ibix]

Thanks. Figured the universe (sorry, as a programmer I tend to use variables more than I should maybe) would blink out for me at that velocity. Interesting that my space-time frame could impact the entire universe like that.

Frames don't do anything. All that's happened here is that (loosely) you took a short-cut to the end of the universe. It doesn't affect anyone else.

 

[phyzguy]

found the formula for determining the Lorentz factor for ~c (which I still have to compute for the length foreshortening mentioned) and for determining KE to accelerate a specified mass to that. My compiler doesn't support the necessary floating point accuracy so I'd also have to convert the problem to huge integer arithmetic... and then solve for mass. Fun exercise. You're probably way more qualified to guesstimate.

If you take the time to learn the physics involved, you will find that it is a simple calculation that takes seconds. No compiler or conversion to huge integers required - except the "wet" compiler between your ears.

 

[Ibix]

If you take the time to learn the physics involved, you will find that it is a simple calculation that takes seconds. No compiler or conversion to huge integers required - except the "wet" compiler between your ears.

Indeed. And the $\gamma$ factor ought to be well within the capability of a double precision number anyway. Sounds like @Chris Miller is doing something wrong somewhere.

 

[dm4b]

Whether c changes has everything to do with what we mean when we ask whether "c changes". What physical experiment can you do to compare c at one time and place with c at another time and place? For instance, what unchanging standard will you cart around to do your speed tests with?

And what makes you think that it is c that is changing rather than your standard?

You're only reinforcing my point. Light did what it does, long before we arrived on the scene and started asking "what we mean when we ask whether 'c changes'"

 

[jbriggs444]

You're only reinforcing my point. Light did what it does, long before we arrived on the scene and started asking "what we mean when we ask whether 'c changes'"

That seems to miss the key point that in order to meaningfully ask whether c changes, one must know what it means to ask whether c changes.

 

[Dale]

You're only reinforcing my point. Light did what it does, long before we arrived on the scene and started asking "what we mean when we ask whether 'c changes'"

The point is that whether c changes is not a question about light, it is a question about your system of units.

 

[dm4b]

The point is that whether c changes is not a question about light, it is a question about your system of units.

That seems to miss the key point that in order to meaningfully ask whether c changes, one must know what it means to ask whether c changes.

Do you guys not realize how anthropocentric your replies are? Again, this is only reinforcing my original point. Light doesn't care about any of this, or what we're capable of asking, understanding, defining, measuring, or about any other human based activity.

Also, it's not just a question of units, as one can try to break past that limitation (even if the theories that do so are rather implausible sounding). To quote Sean Carol:

"The whole game of varying-c theories, then, is to find ways that the real dimensionless constants of nature (like the strengths of the fundamental forces, or ratios of particle masses) could change in perfect harmony such as to give you the impression that what’s really changing is c"

 

[jbriggs444]

Do you guys not realize how anthropocentric your replies are?

Our replies are anthropocentric because we're answering a question asked by a human being. Sure light does what it does. That's an empty tautology. The question is what does it do? And does it do it faster or slower now than it did then. That question is not particularly well posed. If we are going to ask it at all, we'd better nail down the question before we go haring off after answers.

Which is, I think, basically the same thing you are saying, albeit with a different emphasis.

 

[Dale]

Also, it's not just a question of units, as one can try to break past that limitation (even if the theories that do so are rather implausible sounding)

Sure, one can break past that limitation by asking a different question. Asking if c varies is a question about the units. Asking if the fine structure constant varies is a question about the physics of light.

To quote Sean Carol:

"The whole game of varying-c theories, then, is to find ways that the real dimensionless constants of nature (like the strengths of the fundamental forces, or ratios of particle masses) could change in perfect harmony such as to give you the impression that what’s really changing is c

Exactly. C is not dimensionless. The fine structure constant is.

 

[Herman Trivilino]

Do you guys not realize how anthropocentric your replies are? Again, this is only reinforcing my original point. Light doesn't care about any of this, or what we're capable of asking, understanding, defining, measuring, or about any other human based activity.

And light doesn't care what you as a human get when you measure its speed. To do that you need to invent a length standard and a time standard. Light doesn't care about any of that, either.

So when you ask about the speed of light changing, you're not asking anything at all about light. You're asking about human measuring methods. The responses are anthropocentric because the question is anthropocentric.