swansont

The speed of light was measured long before Einstein. It had a value. c refers to that speed. Not rational to you, but your demonstrated confusion about all this points to you as the problem. The argument is quite rational to people who can follow it. Yes, exactly. So when the rod is moving at v, light should move at c+v if they are moving in the same direction. We can find the time to travel the distance of the rod + the distance the rod moves (which we have already established as r + vt) using d = velocity * time t = d/v = r + vt/c+v rearranging, we get ct + vt = r + vt, which simplifies to ct = r, so t=r/c But Einstein’s equation, using the constant c in all frames, is t = r/c-v The equations are different. One of the motivations for the paper Light has a speed, so of course it has a value. Einstein never specified that value; the actual number doesn’t matter for his argument. He never refers to it as “consistency of motion” he calls it the “constancy of the velocity of light” meaning it is a constant and not variable Yes, a fixed value. Not variable. The number attached to this isn’t mentioned. Einstein was not advocating an absolute system. He was arguing for a relative system. Hence the name, theory of relativity Einstein wasn’t spelling out the current (prior to 1905) state of physics, he was proposing something new Whatever What? His proposed solution is the explanation I fixed the post, but it would help if you could learn how to use the quote function properly Einstein’s equation did not use “classical” physics. He used a constant c for the moving frame!

! Moderator Note It’s been moved to Speculations, wei guo, you need to follow our rules - post your material here, and provide evidence to support your claims

We know this now, but that was not the state of physics in 1905. In “classical” physics, as you are calling it (it’s Galilean relativity and Newtonian physics), the speed of the source was added to the speed of whatever is being sent. The speeds added linearly. If c were acknowledged as being constant in Newtonian kinematics, there would have been no point in writing the paper. None of this is mentioned in the paper (no numerical value for c, no Zylon), and I thought we were limiting ourselves to the paper. No, this is wrong. You are misinformed or misunderstand that state of physics before relativity. The constancy of c is a postulate of relativity. It is taken as a given in the paper, to investigate the ramifications of this deviation from Galilean relativity. A problem here is that Einstein assumed readers of the paper would understand the state of physics at that time, and you don’t seem to.

And you were told that it needs to be posted here. People have to be able to participate without clicking on links, per the rules.

At the end of section 2 he has shown that time is relative, owing to the constancy of c, which was not part of “classical” physics. If that had been applied to the problem, the light would have acquired the speed if the source rather than being constant, and the time in both frames would be simply r/c

In QM superposition is in regard to the state of the particle, not its position. You can describe such a system with one state if you change the basis. In classical physics it’s about the addition of wave amplitudes in e.g. interference. “Super” simply means “on top of” in this context, as in the word “superimpose” It’s probably a mistake to read too much into the verbiage used; the equations are the proper description. A superposition of two states is a|1> + b|2>

If the tick of the clock is a round trip of light, the tick will be r/(c-v) + r/(c+v) in the moving frame. In the rest frame (v=0) that same tick is 2r/c They are not equal. Thus, the ticking of the clocks are not synchronous. This can be easily checked for any value of v (less than c, of course) It’s a consequence of the constancy of c. There is no force. They tick at different rates, though they can both start at the same time

! Moderator Note ChatGPT is like predictive text with a larger database. The results are fictional. What is the goal of this thread?

Right. And we’re discussing the equation at the end of section 2, which Logicandreason just acknowledged as being correct, and why Einstein claims that clocks will not be synchronous between the two frames.

Radiated power of ~2 x 10^18 watts, mentioned in the abstract of the paper, is probably why we aren’t doing it, and why it’s detectable.

LOL, that’s not what superposition means.

But, when combined with the first postulate, “Any ray of light moves in the “stationary” system of co-ordinates with the determined velocity c, whether the ray be emitted by a stationary or by a moving body” the result is that speed of light must be the same for all (inertial) observers, since any frame can be considered a stationary frame. But Logicandreason isn’t challenging the postulates as being in error.

! Moderator Note You need to cite some peer-reviewed work to support this position, because assertions aren’t going to cut it.

Different events? No. They are both tracking the light traveling from A to B and back to A. Yes, there is error in “classical” physics, in assuming that everyone measures the same time interval. That’s one of the points of the paper! It happens because of the constancy of c. If light acquired the speed of the source, as with other phenomena, the times woul be the same. Also true, owing to relativity, but in “classical” physics they would be the same. But this is all based on the constancy of the speed of light, which is a postulate of relativity. It is not what “classical” physics reports. We have not analyzed that case.

It’s more than this; it’s that each of the times in the moving frames are different than in the rest frame, and more importantly, the round-trip times will be different in the two frames. Einstein showed that the time for a tick is different in the rest frame (trest = 2r/c if a tick happens once per round trip) than the ticks in the moving frame because the round-trip time will differ. He didn’t explicitly show this because it’s pretty obvious. The people one would expect to read his paper (physicists) would know this.

I haven’t been paying attention to Mordred’s line of discussion. I’m more interested in your contortions to deny the algebra I presented. If you can’t come up with the equation I requested -it’s pretty simple - you really have no business arguing that my derivation is wrong (and it isn’t; but you have to not fabricate statements that you attribute to me)

A little math/physics might explain why (imagine that!). What signal strength is needed for detection, and what can be supplied? That will tell you how far away you can expect it to be effective. The deep-space network that communicates with e.g. the Voyager craft have the power drop off by a factor of around 19 orders of magnitude. It’s a bit more than 10^9 km. The inverse-square law is brutal. It works because we know what signal we’re looking for, so it can be picked up among the noise. That’s ~10 light-hours. A signal that goes light years (at least ~1000x the distance, so a million times more attenuation) would need a proportionally larger power to stand out. You can boost reception with an larger area, but DSN starts with a pretty big dish. Who is “we”? Link? Who is doing this? edit: looks like SETI is using data from the VLA, and not doing it as a dedicated search. The large aperture and number of dishes bumps this up to possible https://www.seti.org/press-release/massive-radio-array-search-extraterrestrial-signals-other-civilizations ”COSMIC operates commensally, which means it works in the background using a copy of the data astronomers are taking for other scientific purposes,” said Paul Demorest, Scientist and Group Lead for VLA/VLBA Science Support at the National Radio Astronomy Observatory. “This is an ideal and very efficient way to get large amounts of telescope time to search for rare signals.”

So robots, not alien life. And yet we were just subjected to a thread where alien beings are allegedly sighted. You can’t have it both ways. Citation?* The US government classifies material for which “unauthorized disclosure could reasonably be expected to cause damage to the national security” (serious/exceptionally grave damage for secret/top secret. The thing is, the US only represents a small fraction of the world. Why so many sighting in the US? The US can’t classify info from other countries - why not get data from sources outside the US? *edit This says it was the CIA, and that the docs were declassified in 2011 https://www.cia.gov/stories/story/secret-writing-cias-oldest-classified-documents/

The Voyager missions were approved in 1972 and launched in 1977. It takes time to build and test a space probe.

You asked a question, so this was moved into the mainstream physics section. “Alternative” views need to be raised in the speculation section.

A proton and electron would accelerate in opposite directions in an electric field. F= qE (positive meaning directed in the +x direction) An electric field can’t be both positive and negative at a given point.

You can’t use your pet theory about QM to conclude anything about how mainstream physics treats the issue.

Yes. They would have trouble dropping in and visiting the surface of a planet that has higher gravity than what they’ve become adapted to. Their muscles would have atrophied and they would have a lower bone density, relative to the original state. (the sci-fi show “The Expanse” touches on this, using 1g to torture someone who’s adapted to lower gravity) It’s why one can infer that it’s likely that any aliens sighted on earth, if there are any, must be adapted to something close to our gravity.

Nomadic aliens need to get their material from somewhere. There’s an energy cost to this - maneuvering, going in and out of gravity wells, for both the main craft and whatever is used for retrieval from wherever they are getting the stuff. Then there is the time spent these “oases” where they are using up these resources, which dictates how much material has to be obtained, and how big the ship needs to be. That’s the analysis that always seems to be absent or glossed over A being adapted to low-g would have difficulty existing in higher-g environments. For a being adapted to much higher than 1 g, they might not have developed space travel at all, owing to the energy required to lift payloads into space.

I takes years to prepare this kind of a mission.