Puzzling thing about Speed of Light/Speed of Causality

[ignoramus]

Really Mat? You wanna ask theists highly technical questions? The answer is always "highly technical mysteriousness!"

I've learnt so much from them since coming here! hehe

[Anomalocaris]

Think of it this way.   When you push on a stick, what is happening at a microscopic level the atoms in our hand begins to encroach on the molecules at the end of the stick. The electron cloud  around your atoms begin to electromagnetically repell the electron cloud in the atoms of the molecule at the end of this stick.   This repulsion travels at speed of light.   So when your hand start pushing, it takes a small amount of time before end end of the stick even “knows”.   Hence speed of light information travel.

Once the first atoms in the top of the rod sense the encroachment of your hand atoms, it start to move out of the way in response to electromagnetic repulsion.  But they were held in place in the rod by electromagnetic forces with other atoms in the rod.   So information travels from one atom to another at speed of light and cause them all progressively become “aware” and move.    But it takes time not only for the first indication of movement of some atoms to travel to others for the others to move,  the atoms and molecules  are held in stable configurations that once disturbed takes more time to settle back down, so it takes more time than how long light would take to go from one molecule to another for the full effect of pushing one one side of the molecule to travel to the molecule on the other side.

Hence even though information travels from atom to atom st speed of light, deformation takes much longer to travel from molecule to molecule.

So this is why if you push on a stick, the other end doesn’t feel “ pushed” until long after information had time to travel at speed of light from one end of the stick to the other.

Let’s say you push a rigid metal stick about 90 million miles long going from the earth to the sun, pushing on an/off switch at the surface of the sun.  Typical rate of propogation of compression in metal is 2-3 miles per second.   So it will take 30 million seconds, or roughly 1 year,  before the other end of the stick feels the push.

Add another curve ball to assessing how long it will take for you to notice the sun went out after you pushed on the stick connected to the sun’s off switch.    What happens when you turn off the sun?   The sun derive all of its output from hydrogen to helium fusion at its core.   Let’s say the switch is wired to the core and electric signal travels from the switch to the core.   That will take about 1.5 seconds.   Let’s say the core turns off (some how) instantly.   There is reason to believe turning off the hydrogen-helium fusion reaction will simply initiate higher order fution reaction from helium upwards, but we’ll ignore that.   Instantly off means the core will immediately stop putting out more energy.   The sun goes dark, right?   No.    

First, the sun’s surface is incandescently hot, and the sun won’t stop shinning until the surface cools.    How long will that take?    Well, it won’t even start to cool, or even begin to show the first minute amount of dimmingand reddening, for 3 million years.   Why, because when energy is generated at the core in the form of high energy photons, these photons (mostly) don’t just zip out at speed of light taking their energy with them. They instead bounce from atom to atom inside the sun, getting reabsorbed and reradiated from atom to atom. It takes 3 million years for the photons generated the instance before you turned off the core, to actually make its way to the surface of the sun.  

So if you poke the off switch of the sun with a stick from the earth.    It will take a year before the switch actually move.  1.5 seconds for the off signal to get to the core, 3 million years before the effect of the extinction of the sun’s core becomes noticeable at the suns surface, and 8 more minutes before the very first faintest hint of the effect is noticeable on earth.   In this time you died, Jesus failed to come again, humans went extinct, anthropogenic global warming peaked and subsided, new ice ages came and went roughly a dozen time, Himalayas got a few hundred feet taller, Appalachians got a a few hundred feet lower,  Pacifica moved north along San Andreas fault to block the golden gate out of San Francisco Bay, and finally cockroaches gazed up in insect wonder at a sun that seems just infinitesimally dimmer and redder, and smaller.

[Whateverist]

Ever seen an arrow firing? It's like that.

Is this what you mean?  Still not quite getting it.






But that last explanation by Anomalocaris did the trick.  Never mind.

[The Grand Nudger]

Not the best vid (but they did do spine tests!).  

If you find a full side shot..you'll notice that the rear of the arrow..the part being pushed, begins to accelerate before the leading tip.  The mass of the point resists acceleration....and because arrows are designed and made of materials specifically to allow for this - they make a great and greatly exaggerated example of why pushing on the back of something doesn't mean that the front moves simultaneously.

It actually takes some pretty short, rigid shit to foist the illusion that it does on us. That's why it's counter-intuitive, we work with short rigid shit all the time.

Ladies....

[Anomalocaris]

Not the best vid (but they did do spine tests!).  

If you find a full side shot..you'll notice that the rear of the arrow..the part being pushed, begins to accelerate before the leading tip.  The mass of the point resists acceleration....and because arrows are designed and made of materials specifically to allow for this - they make a great and greatly exaggerated example of why pushing on the back of something doesn't mean the the front moves simultaneously.

I have to find it again, but I’ve seen a slow motion video of an automatic rifle being fired, and you see the rifle barrel actually deflect with each shot, and the receiver slightly bends as bolt slams forward, and the rifle noticeably compresses along it length before the recoil is transmitted to the firer’s shoulder.

[The Grand Nudger]

I've been getting a kick trying to imagine the downright orbital curve a rod that could reach the sun would end up in if you could flip it as fast as you could push a little wooden rod.

Hope that switch is made out of some pretty tough shit.