swansont

As I recall, trying to get you to give scientific/analytical support for your conjecture about interstellar travel in the past has been like pulling teeth. I’m not interested at this time.

Please show the derivation

Please don’t respond to obvious spam. You aren’t going to shame them or reason with them. Use the “report post” function to bring it to the attention if the moderators.

I agree with Greene to some extent; the earth would not stand out. If they are more than ~100 LY away, what would make us “interesting”? It’s not communicating with an anthill so much as communicating with a rock. Why would they care about this rock?

How fast is this drone traveling? i.e. how far away are the Lax? A few thousand LY? (~0.001c) What made the earth stand out among all the systems within that radius, that they sent a drone, expecting to communicate? The earth would not be forming, with only a potential for life, if the time span is only a few million years. But earth would have no technology beyond crude stone tools. They could be sending drones to all “goldilocks” planets, of course.

What, again? Why do my previous posts not suffice? Speculation does not absolve you from basing things on science. https://www.scienceforums.net/topic/86720-guidelines-for-participating-in-speculations-discussions/ this is a science forum, and speculations are still to be discussed in that context. If it doesn't fit as a science discussion, or you refuse to discuss the idea as such, the thread will be closed down. It can’t be both. If you want to discuss a framework for sci-fi, you need to make that clear.

Like how 18.92 mm is smaller than 1 cm?

That’s science fiction. You can cite e.g. Star Trek all you want, but don’t pretend it’s science. It’s your list. You numbered them and I referred to the numbers. I think such lists generally build on previously stated assumptions because if there is a dependence it’s less confusing that way; there’s a logical order. You can have 3 or 4 without 2. Once you’ve stated 2, there is no need for 3 or 4, since that’s already implied, unless you are invoking magic. But to go further, 3 and 4 do not guarantee 2

Are they citing the equation based on an aether, or one based on special relativity? Since you cite pages early in the book, it seems the former is likely. You can’t use SR applied to an equation derived assuming the existence of an aether. The assumption is invalid, so the equation can’t be assumed to hold. Saying ∆x = 0 and ∆t = 0 is an assertion that time dilation and length contraction don’t happen, which is a circular argument. And we have experimental evidence that SR is correct.

2 kinda requires 3 and 4, and 2 is a bad assumption, given the physics we know.

With what, specifically?

Is there any evidence that they do?

The M-M experiment failed. There was no fringe shift. Do you have an equation that works, i.e. is consistent with relativity, to discuss?

If they have discovered us, it’s a discovery of us in the past. And communicating with us requires the same amount of delay in getting a signal to us. Keeping their distance is not a problem, since one can’t travel fast enough.

The Sagnac effect is for rotational systems, which are not inertial frames. Any article that mentions absolute velocities isn’t a reliable source of relativity information ; it is not mentioned in the body of the wikipedia article (which you should link to if you’re going to reference it) What the article actually says is “the fringes of the interference pattern should shift when rotating it by 90° as the two beams have exchanged roles. To find the fringe shift, subtract the path difference in first orientation by the path difference in the second, then divide by the wavelength, λ, of light” and rather importantly this is an equation that assumes an aether, and was found to be wrong. It’s not derived from SR. So how does this show anything about SR?

I think the primary reason aliens don’t communicate with us is that they would be many light-years away from us and the speed of light is finite. That’s a show-stopper even before you consider other confounding effects.

And in practice, "Swanson" is not pronounced as "Swans + on" (i.e. it's not pronounced Swanzon) My username itself out loud would be "Swanson T" And I often spell my last name when conversing on the phone, since any garbling will sometimes have it register as Watson, and that causes all sorts of problems. Some people here have introduced typos and called me e.g. swansnot (Some doing so repeatedly, such that one begins to wonder if it was deliberate)

I joined when I was creating a number of online accounts (some personal, some for work), and wasn't going to try and get too clever. Last name, first initial. Reduced chance of registering a name already in use, so I wouldn't have to be Gandalf7 on one site and Gandalf44 on another and keep track of which one was associated with which site. My now-dormant blog's name (Swans on Tea) is a phonetic derivative of this.

! Moderator Note Discussion of religion in a science thread is a hijack; I've moved this to speculations in case people want to follow up on the nonsense posted in the OP Unsubstantiated claims carry no weight; if you don't follow scientific rigor this will end up in the trash Such as "May I also add that the beaks had differences of less than a centimeter, only about 18.92 millimeters." 18.92 mm is almost 2 cm, so this makes no sense. And that's a lot for a beak of a bird that are between 10 and 20 cm in length. If the beak itself were a cm or 2, even a couple of mm difference would be a large variation https://en.wikipedia.org/wiki/Darwin's_finches "Carbon dating can't tell how old the earth is, it's incredibly inaccurate, it once showed a 3 year old bone to be thousands of years old, and animals that have different carbon dating for different parts. There are some large animals that were carbon dated and they got different dates for different parts of the body." Nobody uses carbon dating to show the age of the earth; all this shows is how little you actually understand about it And if you're going to cite examples you will need to link to where you found the claim, because the source may have fabricated it (not uncommon) or it may be taken out of context so that the meaning is distorted (also not uncommon). Unfortunately a lot of people claiming evolution is wrong do not hesitate to lie about the evidence, so simply pulling material from somewhere is problematic.

When I look up the equations in wikipedia, there is an additional term that includes the cosmological constant https://en.wikipedia.org/wiki/Friedmann_equations The version you present is referred to as the "matter only" form You note that the vacuum energy density is negative, which is the source of the negative pressure, and there is no kinetic energy associated with this. Vacuum energy and matter are two different things

I think mods can read them if one of the people involved reports it (i.e. as a rules violation) That's the only exception, AFAIK.

Makes sense if they were doing some kind of "response to being fed" experiment Since it's a book on rationality, I'm guessing explanations of probability and randomness have to do with how humans are generally bad at determining randomness and doing risk assessment

Because decay is probabilistic, it’s related to the chance of recording a decay in some time interval. http://www.ciphergoth.org/crypto/unbiasing/ place a Geiger counter close to a radioactive source, and the "clicks" are randomly distributed. If the source is large enough and has a long enough half life, we can ignore its slow decay, and treat each "click" as an independent event - the probability of a click in the next millisecond is the same no matter what the history is (there are many sites explaining how to build such a device using a Geiger counter)

I’m not sure what specific advantage LIDAR would give you. A laser beam with a small divergence means you only cover a tiny solid angle, so you’d likely only use it if you already knew where to look But the answer would depend on how much laser power you have. They use laser ranging with the retro-reflectors on the moon At the Moon's surface, the beam is about 6.5 kilometers (4.0 mi) wide[21] and scientists liken the task of aiming the beam to using a rifle to hit a moving dime 3 kilometers (1.9 mi) away. The reflected light is too weak to see with the human eye. Out of 1021 photons aimed at the reflector, only one is received back on Earth, even under good conditions.[22] https://en.wikipedia.org/wiki/Lunar_Laser_Ranging_experiment The intensity would drop off with distance squared (the beam gets bigger) and other objects would be less reflective than the mirror array, and the aiming problem gets worse, since you still want to hit it with the middle of the beam

! Moderator Note Posting a video alone violates rule 2.7 and we assume link-shorteners denote sma links. Do it again and you will be banned