Posts Tagged ‘relativity’

I do wonder why the speed of light is 299 792 458 m/s instead of 400 000 000 m/s or 50 billion m/s.  I know it’s constant and like other constants the universe just sort of has them and299 792 458 m / s whether they are this value or that value, the point is, they have a constant value.299 792 458 m / s.

It’s still fun to think about.

Here are two decent resources explaining the situation with the finiteness and constance of the speed of light.

Why is the speed of light constant

Many novel ideas are found on the Internet. One not so novel notion is that Einstein was wrong and that the “lightspeed limit” is really just some international conspiracy of conservative “establishment” scientists. Those who make this point neglect the fact, however, that the deduction about the speed of light is not a result of some exotic assumptions or blind speculation, but a fairly simple consequence of some fundamental assumptions about nature: in other words, if you wish to prove that Einstein was wrong, you have to show that either elementary logic is incorrect, or that some of our basic assumptions about nature are outright false.

Here is why.

Why isn’t the speed of light infinite

The fact that space and time must get mixed up to keep the speed of light constant implies that, in some sense, space and time must be the same, despite our habit of measuring space in meters and time in seconds. But if time and space are similar to the extent that they can be converted one into the other, then one needs some quantity to convert the units–namely, something measured in meters per second that can be used to multiply seconds of time to get meters of space. That something, the universal conversion factor, is the speed of light. The reason that it is limited is simply the fact that a finite amount of space is equivalent to a finite amount of time.

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This morning laying in bed I was thinking about time, as I often do. 

In common language, we talk about time as something unto itself.  Time marches on, time flies, where has all the time gone…  We all know what we mean when we say and hear those cliches, however, “time” does not really fit.  Time is a measurement for the rate of change (rotation of the earth, orbit around the sun, oscillation of crystals, atom energy transitions).  

The official SI definition of a second (SI considers this the “base unit” of time): “The second is the duration of 9 192 631 770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the cesium 133 atom.”

So basically it’s the rate of change of energy levels of the cesium atom.  I leave it as an exercise to the reader to go figure out why SI uses cesium 133 and what SI means with “hyperfine levels.”

If we substitute this definition in to common time cliches the cliches lose their power.  Cesium Atoms transition a lot without you noticing when you are having fun. (Time flies when you’re having fun.)  Where have all the cesium atom energy transitions gone.  Yes, this is tongue in cheek.

The point is TIME is not what we’re talking about when we drop a time cliche in conversation.  We’re talking about behavior.  When you’re having fun, you typically have a huge amount of behavior and adrenaline.  You’re rate of behavior and the reinforcements come fast and furiously.  When you have a glut of stimulus to process, your rate of change (… time …) typically is higher than in less “fun” situations.  [Fun, as a concept, deserves a whole write up unto itself].  When you lament the passage of time, you actually lament the missed behavior, the non-change, and/or the changes you didn’t notice.

In some sense the more change you experience, the more change you notice, the less you’ll sense missing time and the more time will fly (the less you habituate to the routine of life).  Nothing profound here, just a reflection on a day of memory, relaxation, and family/friends.

Resources you might enjoy:

Philosophy of time:


SI Units


Fundamental Units


World Line



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