I am vindicated!
It was only by accident, though — the video above is about Conservapædia, and you may recall that there was a period over ten years ago that Andy Schlafly was obsessed with me. It still counts!
Pharyngula
Evolution, development, and random biological ejaculations from a godless liberal
Does Conservapedia still exist? Oh holy fartleberries it does! Here it is, ugly as the sins it’s supposed to denounce. A distillate of ignorance second to very few…
“Nothing historical, from writings to civilization to long-living organisms like trees, has survived from prior to 3000 or 3300 B.C” (due to the Flood obvs). Oooooorg.
And now we have El Muskorat personal Rubbishpedia, “Grokipedia”. Another flood, but this one of idiocy, just what we needed.
But anyway, thanks for clueing me in on Queen Coke Francis channel, it’s very appreciated.
E = mc² is liberal claptrap. Boom. 🍄🟫☁️
Jennifer Welch says JD Vance is secretly gay and was a failed drag queen
[meta]
Reginald, anyone can say anything about anyone.
“Welch, nicknamed “The Sheriff” on the show, established a career after Sweet Home as a commercial and residential interior designer when she launched her own firm, Jennifer Welch Designs. Welch’s work focuses on achieving high attention to detail while designing large luxury kitchens and high-end offices.” sez Google
(Where’s the cred?)
I’ve noticed that Jennifer Welch doesn’t worry about that little thing called “evidence”.
I stopped watching her show when they brought on an astrologer, in complete seriousness, to explain some nonsense about how different planetary cycles affect people. No thanks.
Hadn’t heard of Queen Coke Francis before! Cheers!
“E = mc*c is liberal claptrap?” Even creationists leave Einstein strictly alone!
The Simplest Derivation of E = mc^2
Reginald Selkirk @8: That is the worst ‘derivation’ I’ve ever seen. It’s as though the author is trying to be confusing. Any proper derivation rests on the two postulates of Special Relativity:
(1) The laws of physics (e.g. Maxwell’s equations) are the same in all inertial frames.
(2) The speed of light in vacuum is the same in all inertial frames.
So it boils down to finding how various quantities (most importantly position, the electromagnetic fields, and thus electromagnetic energy) transform between inertial frames. And then Bob’s yer uncle, E = mc², relating rest energy to rest mass. And the relativistic definition of momentum follows
Since he’s a far-right-wing Cat-lick, i’m pretty sure Schlafly’s sole argument with relativity boils down to one thing:
Einstein was one of those sneaky, godless, JOOOOOOS!
Ted Lawry@7:
“Even creationists leave Einstein strictly alone!”
NO THEY DON’T. Your claim is exactly counterfactual. Young Earth creationists have spent several decades trying to “prove” the speed of light has not been constant. See Barry Setterfield’s claptrap from many decades ago. More recently, Young Earth creationist Jason Lisle (PhD in astrophysics, but still a creationist obscurantist, and employed by a creationist organization to peddle YEC nonsense) claims that the speed of light coming towards the earth is infinitely fast (what any of the astronomers observe is happening exactly as they see it) but the speed of light leaving the Earth is C / 2. Those two properties make the two-way speed of light C, which has been confirmed so many times that Lisle cannot discard it, since it is fairly well known to his intended audience of dunces. Unfortunately for him, the one way speed of light has been confirmed so many times that it is not in doubt, but that is generally unknown to his willfully ignorant audience. Even “Veritasium” and “Smarter Every Day” gets this completely wrong! If his claim was true, NASA space probe communications could not work the way that they do. Space probe communications require compensating for the constant speed of light. Probes moving away from or towards the Earth at high velocities (but at a very tiny fraction of the speed of light) require frequency shifts for receiving and sending radio transmissions. Even the GPS system utilizes corrections for both general and special relativity, or else their locational accuracy would be off by several kilometers per day. Of course, there are crackpots who dismiss this with no more than hand waves (all too often, scientifically illiterate engineers).
Even anyone with sufficient electronic test equipment can measure the one way speed of light, and show that it is isotropic (the same in all directions). A high bandwidth oscilloscope used along with a fast rise time pulse generator and a section of air-line can measure the speed of light of radio waves (which, being electromagnetic, are also longer wavelength photons). I can do this at home, as can anyone else, with suitable electronic equipment. Doing the one way measurement using radio waves is far less involved than when using light, since the latter generally requires using atomic clocks, etc. Both methods can be done for accurate one-way speed of light measurements. I have even seen sloppy university level presentations that incorrectly state that the 299,792,458 m/s speed of light in a vacuum is approximate, while it is, in fact, EXACT! The speed of light had been previously defined by the length of platinum-iridium meter bars, but now it is the opposite, since measuring the standard meter to 9 significant digits in a very tightly temperature, humidity, and pressure controlled environment is impractical.
https://www.icr.org/content/has-speed-light-decayed
https://christianity.stackexchange.com/questions/2932/how-do-young-earth-creationists-reconcile-the-age-of-the-universe-with-the-speed
https://creation.com/en/articles/the-velocity-of-light-and-the-age-of-the-universe
https://www.youtube.com/watch?v=pTn6Ewhb27k&t=134s
Oddly enough, some of my links have disappeared from my above posting. So here is another attempt to test if they were being censored.
https://en.wikipedia.org/wiki/Metre
zetopan @11:
No, it has not been confirmed. Apparently, you think most physicists are willfully ignorant.
I may engage on this if I have the time and energy, but I’ll leave this for now;
https://physics.stackexchange.com/a/591436
*ε = 1/2 corresponds to constant c, while ε=1 corresponds to infinite speed in one direction, and c/2 in the other.
@outis:
As you note yourself, yes, it does… but it’s very much a shell of its former self from everything I’ve heard. There are, when you get right down to it, three reasons for that:
– Andrew Schlafly has other obsessions and isn’t focusing on it so much anymore (especially given how much of a hassle it has caused him).
– The entire original purpose of Conservapedia was to act as the basis for a series of new conservative-approved textbooks and lesson plans for home-schooling, and other companies have already filled that niche, and without any formal purpose it’s now even more just Schlafly’s vanity project than it started as.
– The site has very few regular editors anymore: they keep losing editors to internal conflicts, and they have an inverted Poe’s Law problem in attracting new ones, in that anybody who applies is either not openly conservative enough to get in, or so over-the-top conservative that they look like a satirist. There have been enough satirists actually getting approved in the past that Schlafly is a bit twitchy about that now, and I suspect that you basically need to already be one of Shlafly’s friends to get in, and he just doesn’t have that many friends willing to provide volunteer labour for a project that has been dying a slow death for years.
@Akira MacKenzie:
One of the reasons people like Schlafly hate relativity is that they absolutely hate hate hate the concept of moral relativism (from their standpoint, there is one set of absolute morality for everybody: they are right and everybody else is wrong) and they extend that to any sort of relativism or relativity. Just the concept that there isn’t one absolute perfect vantage point for everything, or even that there is nothing special about our particular vantage point, is essentially heresy.
The fact that Einstein was Jewish almost certainly doesn’t help either, but I suspect it wasn’t actually the core complaint.
I seem to recall that Schlafly doesn’t believe in imaginary numbers, either, which is quite an interesting statement coming from an electrical engineer.
Rob Grigjanis@13 “No, it has not been confirmed. Apparently, you think most physicists are willfully ignorant.”
There are at least two ways to measure the one way speed of light, one of which I pointed out can be done at home by nearly anyone. While some physicists claim that it is impossible due to clock synchronization problems over very long distances, it is not that difficult over much shorter distances. You can also build a box around yourself and then claim to be trapped. The way that they are claiming to perform the measurement is, in fact, impossible, or at the very least very impractical. But this is only in the same way that measuring the volumes of all the world’s ocean waters with a teaspoon is not really possible. If you select a terrible measurement problem to begin with, you can expect severe problems when trying to use it.
The communications with space probes utilizes the fact that space is isotropic over the distances involved. If the one way speed of light was dependent on direction, that communication would obviously be compromised. That is one test of speed of light isotropy over the distances involved (out well beyond the dwarf planet Pluto’s eccentric orbit). This is also true for the GPS system, which depends on the speed of light being isotropic over those distances involved. Creationists can never show actual supporting evidence for their evidenceless claims. The main issue here is the isotropy of space and the speed of light (which is more correctly: the “speed of causality”) over various distances.
This is going to be a bit technical, but anyone skilled in electronics can easily perform this with equipment that you can get for cheap in the used marketplace, if you don’t already own this equipment.
Take a high bandwidth oscilloscope (sampling scopes have the highest bandwidths, over 1GHz was available in the 1960s). Connect the sync (trigger) output of a fast rise time pulse generator or a high frequency oscillator (say 1GHz for the latter) to the trigger input of the oscilloscope. Connect the main output of the signal generator using a high frequency coaxial cable to an oscilloscope input channel. 50 ohm terminations are required if using 50 ohm coaxial cables (which should always be used at these frequencies), to prevent reflections. Now, the oscilloscope channel is displaying the pulse or sine wave output of the signal generator. If you now insert a 1-foot long coaxial air line (a coaxial electrical conductor that uses air as its only dielectric) into the main output of the signal generator and observe the oscilloscope displayed signal be delayed on screen shifting by close to 1 ns to the right (indicating a time delay), since light in air travels at nearly the same speed as light in a vacuum (about 299,704,000 m/s vs 299,792,458 ms, respectively, a difference of only about 0.03%). Electrons travel at relatively slow speeds in conductors, but their electric fields travel at the speed of light in that medium. The speed of light in 50 ohm coaxial cables with non-air dielectrics is approximately 2/3rds of the speed of light in the vacuum, but this setup does not rely on that, since the “air line” has air as its dielectric. You can orient the air line in any direction to show that the direction of travel does not matter over that 1 foot of travel distance. The Tektronix Museum even has this very demo demonstrating the measurement.
Can we measure the one way speed of light to the second-nearest star? Not really. Two atomic clocks would need to be synchronized out in space, and then one very slowly transported to the target star. Slowly, because achieving high travel speeds would desynchronize the moving clock due to relativity. Since the second-closest star is over 4 light years away, the atomic clocks have to be exceptionally stable and remain reliable for many centuries. And the changing gravitational fields will also alter the clock synchronizations due to relativity.
[Theoretical vs applied physics — not irreconcilable]
@16 zetopan. This is the engineering disease. Technical details about measuring the speed of radio wave do NOT address the conceptual problems. You cannot synchronize clocks in two locations by moving one very slowly, without assuming the Einstein convention about the one way speed of light. There are serious complications of which you seem totally unaware. You know best, of course, everyone else is an idiot. Look up Reichenbach or read the Wikipedia article on “One-way speed of light.”
Reginald Selkirk@8–
The simplest derivation is probably the one Einstein first published in 1905 as a follow-up to his Special Relativity paper. It’s a smidge over 3 pages long and uses only 9 lines of algebra. It does not contain the famous
equation exactly, but does arrive at “If a body gives off the energy L in the form of radiation, its mass diminishes by 
“, which is a simple rearrangement away.
Most “simplifications” I have seen are longer and have more steps. Some of them have the benefit of being easier to follow, but they are not actually simpler.
chrislawson @19: I wouldn’t count that paper alone as a derivation since, as you imply, it uses a result from the previous paper; the transformation of electromagnetic energy between inertial frames. So the derivation starting from the two postulates is more involved, but still remarkably simple for such a profound result.
Just for the halibut, I’ll give my preferred version* of the argument Einstein makes in his paper “Does the Inertia of a Body depend on its Energy-content?”. It uses a result of “On the Electrodynamics of Moving Bodies”, so it is not (as I said above) a complete derivation.
The scenario: we want to come up with an expression for the energy of a body of mass m which is consistent with relativity, and agrees in the non-relativistic limit with E= mv²/2 + a possible term independent of v (where v is the speed of the body in a frame moving wrt the rest frame). We’ll assume energy conservation within an inertial frame (as we do with Newtonian physics).
So we’re looking for a function E(m,v). In the rest frame of the body, it emits (by an unspecified mechanism) em radiation in two opposite directions, with the same amount of energy L/2 in each direction, so the body itself will remain at rest.
In the rest frame, the initial energy is just E(m,0). The final energy includes the em energy L, so we can see right away that the mass must change, and the final energy in the rest frame is E(m’,0) + L (m’ is the new mass).
In a frame moving with speed v wrt the rest frame, the initial energy is E(m,v). For the final energy, we need the result from the previous paper, which tells us that the em energy in this frame is γL, where γ = 1/√(1 − v²/c²).
So conservation of energy in the moving frame gives us equation 1;
E(m,v) − E(m’,v) = γL
Let’s expand the function E(m,v), and γ in powers of v²
E(m,v) = E(m,0) + a(m)v² + higher order tems in v²
γ = 1 + v²/2c² + higher order terms in v²
Because of the non-relativistic limit, we know that a(m) = m/2, so equating coefficients of v², we get equation 2;
m − m’ = L/c²
That’s the result, but let’s take an extra step. We can now write equation 1 as
E(m,v) − E(m’,v) = γ(m − m’)c²
The simplest solution to this is
E(m,v) = γmc²
*It might look quite different, but it is, I think, equivalent.