MolaKule
Staff member
The Speed Of Light ??
- Thread starter billt460
- Start date
MolaKule
Staff member
Do any of you ever read the links given so you get more background info?
https://speed-of-light.com/historical_measurements.html
https://math.ucr.edu/home/baez/physics/Relativity/SpeedOfLight/measure_c.html
From ScienceABC:
"Leon Foucault used an improved apparatus that comprised rotating mirrors and dragged down the value to 298,000 km/s...
The National Bureau of Standards in Boulder Colorado used helium-neon lasers and meticulously accurate cesium clocks to measure the speed of light. They defined the meter as the distance light traveled in vacuum for 1/299,792,458 of a second, such that the speed of light in a vacuum is *drum roll* 299,792,458 m/s or 299,792.458 km/s. Not instantaneous, but yes, extremely rapid!"
A slightly more mathematical treatment:
https://www.physics.purdue.edu/~durbin/Reports/SpeedOfLight/Dorjderem.pdf
https://courses.washington.edu/phys331/SoL/speed_of_light.pdf
I didn't watch the clickbait video but c, the two-way speed of light, has been measured
https://speed-of-light.com/historical_measurements.html
https://math.ucr.edu/home/baez/physics/Relativity/SpeedOfLight/measure_c.html
From ScienceABC:
"Leon Foucault used an improved apparatus that comprised rotating mirrors and dragged down the value to 298,000 km/s...
The National Bureau of Standards in Boulder Colorado used helium-neon lasers and meticulously accurate cesium clocks to measure the speed of light. They defined the meter as the distance light traveled in vacuum for 1/299,792,458 of a second, such that the speed of light in a vacuum is *drum roll* 299,792,458 m/s or 299,792.458 km/s. Not instantaneous, but yes, extremely rapid!"
A slightly more mathematical treatment:
https://www.physics.purdue.edu/~durbin/Reports/SpeedOfLight/Dorjderem.pdf
https://courses.washington.edu/phys331/SoL/speed_of_light.pdf
Last edited:
yes mostly, especially when provided by those like you.
I am not sure which comment this was pertaining to.
The speed of light (C) is at its theoretical maximum in a vacuum - 186,000 miles/s or 3 x 10^8 m/s.
It will be slower in different media, but never faster.
In optical glass (i.e. in fibre optic cables), the speed of light is "only" about 2/3 its speed in a vacuum. Optical glass's index of refraction (IR) is typically just under 1.5.
Light in glass with an IR of 1.5 travels at 2/3 C.
Light in glass with an IR of 2 would travel at 1/2 C.
Light in glass with an IR of 3 would travel at 1/3 C, and so on.
Man, yall jump on a fella quick. Yall are getting on my nerves.
Where did I say light would go faster? My argument, is that the word "constant" is used when people speak on light and its speed, and it (unlike anything else) has a constant measurable speed under any observation or observant. Sure, there is a resistance to the speed through objects, (which makes less sense as light has no mass). I reckon it has to do with the distance? My feeble mind just cant balance that out.
I am no expert, but my opinion is who cares? We aint going to go that fast, or anywhere near it. Ever. And even if we could, we could not come back. One way ticket. Sure GPS uses math and time dilation principles to accurately account for position, great.
It is fun to speak on it though, and display thought experiments to pay homage to the second smartest dude ever, seconded to Newton perhaps, or maybe George Carlin
.
Where did I say light would go faster? My argument, is that the word "constant" is used when people speak on light and its speed, and it (unlike anything else) has a constant measurable speed under any observation or observant. Sure, there is a resistance to the speed through objects, (which makes less sense as light has no mass). I reckon it has to do with the distance? My feeble mind just cant balance that out.
I am no expert, but my opinion is who cares? We aint going to go that fast, or anywhere near it. Ever. And even if we could, we could not come back. One way ticket. Sure GPS uses math and time dilation principles to accurately account for position, great.
It is fun to speak on it though, and display thought experiments to pay homage to the second smartest dude ever, seconded to Newton perhaps, or maybe George Carlin
.
Yeah, but here's the problem that most don't want to admit to, for fear of, "sounding dumb". I read them, but I'll be the first to admit that some of this stuff gets real complicated, real fast. And is hard to get through. And it is just plain difficult to absorb, and wrap your head around. Because it just doesn't seem to wash. You wind up even more confused.
Unlike breaking the sound barrier, that has been done 11 ways to Sunday for decades. And it takes place daily somewhere in the world. It has become commonplace, and today no one questions it. Like so many did before Yeager made it a reality decades ago.
Where as the speed of light, and how it affects time and distance, is a whole different game, with a lot more complicated theories and equations to prove them out. And unlike the speed of sound, we as humans will never be able to achieve anywhere near the speed of light.
Let alone experience time standing still. This is why I like guys like Cox and Neil deGrasse Tyson. They try to simplify it so the average audience who listens to them, can grasp how this stuff actually works. Instead of trying to prove to everyone how much they know.
The public education system in this country has a lot to do with this as well. Most require 4 years of English, but never touch on things that every person will require in life. Like how to apply for a home mortgage, along with what to look out for when doing it.
Or what to invest your money in after you start moving along in life. But they'll all be experts at diagramming sentences on a blackboard...... Until they all forget it 20 minutes after they graduate.
Today it's even worse, the way they pump these kids heads full of lunatic political ideologies. And as a direct result, many graduate totally unprepared for life.
And they think they should all get trophies for simply showing up. It seems every year we drop further down the education ladder....... OK, rant off.
Last edited:
This is a good example of why this can be so hard to grasp. He explains this very well and understandably... BUT, if freefall is the natural state of things, and the reason I feel weight sitting in my chair, is because I'm being accelerated upward at 9.8 meters per second squared.
Why won't I eventually reach the speed of light, and in the process be frozen in time?.... Because at that speed time will all but stop. I'm still heading forward to my 73rd birthday today, just as rapidly as I headed to my first one over 70 years ago.... And all this while I've been supposedly accelerating at a fairly rapid rate.
Why won't I eventually reach the speed of light, and in the process be frozen in time?.... Because at that speed time will all but stop. I'm still heading forward to my 73rd birthday today, just as rapidly as I headed to my first one over 70 years ago.... And all this while I've been supposedly accelerating at a fairly rapid rate.
A more analogous example IMO is flow of water in a pipe.
When a pipe is 100% filled with water and you turn on the tap on one end (apply pressure differential), you get almost instantaneous flow on the other. But the actual speed of the H2O atoms going through that pipe is much, much slower.
The flow of electricity in a conductor behaves very similarly to that of a water filled pipe. Voltage is the pressure differential and by applying it on one end, you get an almost instantaneous reaction on the other end.
Last edited:
You feel the acceleration because the earth is applying a contra force to you exactly countering the acceleration due to gravity. Objects in orbit similarly are falling toward earth, but have an outward force driven by their velocity and momentum that lets them maintain their orbit.
So while you are experiencing acceleration due to gravity, you are not moving and certainly not moving closer to the speed of light.
Good point. In my case, I realize I only know a little; I need to focus on keeping an open mind. I like being wrong, because it means I am learning.
Attending the public lectures around here is flat-out enlightening.
Stanford KIPAC lectures is highly recommended.
Hey if anything I posted is wrong or needs challenged I take no offense. When I suggest on any topic asking folks to think about it differently- this doesn’t mean it’s easy for me either.
I haven't watched the video but Richard Feynman developed his sum over all paths integral to describe the movement of a particle from point A to point B. He's a bit of a science hero of mine.
The water pipe is a good analogy.
MolaKule
Staff member
I don't assume anyone is dumb or uneducated.
I agree It can sound difficult but studying it and reviewing it will finally make sense.
I try to find background information that mostly uses algebra, which most high schoolers have taken. Without understanding the underlying math, it is difficult to fully absorb these concepts.
When a question such as this is asked, my main reason for responding is to educate and hopefully fill in the gaps, nothing more, nothing less.
Last edited:
What about when they first charge the dead line with power? Say for example, it ran from Chicago to Los Angeles. Would the electrons then travel through the line at close to light speed?
Would it then be like an empty pipe, with a time lag as the water first had to fill and pressurize the pipe?
And if electricity is the flow of electrons. And electrons have no mass. And no one has seen them. What is it you actually "feel" when you touch a live wire?
If we look at a lightning bolt are we actually "seeing" electrons? Or is it some type of plasma that is created from all that energy transfer?
Electrons sound like the guy that starts the bar fight, then runs out the back door when all hell breaks loose.
No.
I'm not a fan of the waterpipe for the simple reason of moving mass. AC Electricity in wire is not moving mass, but moving energy.
You feel the energy interacting with your flesh when shocked, but interesting. I wanna think on that.
Lightning is static electricity - different, here: https://en.wikipedia.org/wiki/Lightning
Kinda related, not at first. But watch when he talks about a light beam bending in the rocket
MolaKule
Staff member
The electrons are already sitting in the wire, like stagnant molecules of water in a pipe.
When a voltage (potential) is placed across a pair of wires, that potential places a force on the electrons causing them to move; moving electrons are called a current. As soon as the switch is thrown, the effect felt at the other end is essentially instantaneous, but the electrons are flowing at their "drift" velocity, post 108. A basic explanation is given here:
https://en.wikipedia.org/wiki/Electric_current
BTW, electrons do have mass:
https://en.wikipedia.org/wiki/Electron_mass
Last edited:
The electrons are always there in the conductor, like copper. So the "pipe" is always full when it comes to electricity.
The electrons are part of the atomic structure and are negatively charged. They orbit the nucleus, which is composed of protons and neutrons. The electrons can "jump" from one atom to another when enough energy is applied. Then there is a "void" left from the electron that jumped, which attracts another electron from the closes neighboring atom. It triggers a chain even, which leads to the flow of electricity, or the flow of electrons.
When you touch a live wire and get shocked, you experience electrons being transferred to your body. What separates good conductors from insulators like air, is the atomic structure and how tightly packed the atoms are. Metals have a nice, tight an uniform atomic structure which makes the electrons jumping from one orbit to another much easier. Air, on the other hand, has the atoms very far apart by comparison and their structure is random, which makes it very hard for the electrons to jump from one orbit to another.
Last edited:
MolaKule
Staff member
Lightning is caused by a difference in potential between a cloud and ground or between two clouds.
That potential forces moving electrons (a current) to flow through an ionized channel. The heating of the gases in the air causes a visible flash.
"Lightning is a natural phenomenon consisting of electrostatic discharges occurring through the atmosphere between two electrically charged regions. One or both regions are within the atmosphere, with the second region sometimes occurring on the ground. Following the lightning, the regions become partially or wholly electrically neutralized.
Lightning involves a near-instantaneous release of energy on a scale averaging between 200 megajoules and 7 gigajoules...The air around the lightning flash rapidly heats to temperatures of about 30,000 °C (54,000 °F)...There is an emission of electromagnetic radiation across a wide range of wavelengths, some visible as a bright flash. Lightning also causes thunder, a sound from the shock wave which develops as heated gases in the vicinity of the discharge experience a sudden increase in pressure..."
Google can be your friend for these basic questions: https://en.wikipedia.org/wiki/Lightning
You'd be surprised how similarly a hydraulic system behaves to an electrical system. The terms are difference, like resistance vs back pressure, voltage vs pressure or current vs flow, but their function, from the system view, and how they manage the energy are almost identical.
