[time-nuts] Einstein Special on PBS

Bob Stewart bob at evoria.net
Fri Nov 27 16:30:50 EST 2015

```Hi John,
I hadn't run into this idea before, and I like it.  But I have a problem with the statement:.  "If you move through space at 100,000,000 meters per second in space, then your velocity in the t direction is 283,000,000 meters per second (because sqrt(100E6^2 + 283E6^2) = 300E6.)"  The problem is that your velocity in the t direction remains the same to yourself, because your velocity as compared to yourself is always zero.  So, yes, velocity with respect to some other object does change the rate of time as compared to that other object.  But, as is understood from reading your whole post, time is always moving at the same rate for the one observing himself.
Bob

From: John Miles <john at miles.io>
To: 'Discussion of precise time and frequency measurement' <time-nuts at febo.com>
Sent: Friday, November 27, 2015 2:54 PM
Subject: Re: [time-nuts] Einstein Special on PBS

So, here's how I finally grokked this stuff.  c, the speed of light in a vacuum, is often spoken of as a "speed limit" that nothing can ever exceed.  That's a bad way to put it, and people who have expressed it that way in popular science writing for 100 years should feel bad.

Instead, the way to visualize relativity is to realize that c is the *only* speed at which anything can travel.  You are always moving at 300,000,000 meters per second, whether you want to or not.  But you're doing it through all four dimensions including time.  If you choose to remain stationary in (x,y,z), then all of your velocity is in the t direction.  If you move through space at 100,000,000 meters per second in space, then your velocity in the t direction is 283,000,000 meters per second (because sqrt(100E6^2 + 283E6^2) = 300E6.)

It doesn't make sense to speak of moving a certain number of "meters" through time, so your location in time itself is what has to change.  You won't perceive any drift in your personal timebase when you move in space, any more than you will perceive a change in your location relative to yourself.  ("No matter where you go, there you are.")  But an independent observer will see a person who's moving at 100,000,000 meters per second in x,y,z and 283,000,000 meters per second in t.  They see you moving in space, in the form of a location change, and they also see you moving in time, in the form of a disagreement between their perception of elapsed time and your own.

Likewise, if you spend all of your velocity allowance in (x,y,z), your t component is necessarily zero.  Among other inconvenient effects that occur at dt/dt=0, you won't get any closer to your destination, even though your own watch is still ticking normally.  Particles moving near c experience this effect from their point of view, even while we watch them smash into their targets at unimaginable speeds.

This is special relativity in action.  The insight behind general relativity is twofold:  1) movement caused by the acceleration of gravity is indistinguishable from movement caused by anything else; and 2) you don't even have to move, just feel the acceleration.  That second part was what really baked peoples' noodles.  It is what's responsible for the disagreement between the two 5071As.

-- john, KE5FX
Miles Design LLC

> Hi Mike,
>
> The time rate does remain the same - at the device.  The problem is the idea
> that it is the hyperfine transitions that determine the time...

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