swansont

I still haven’t seen any analysis on your part.

I did. To reiterate: they conclude it’s unexplained. IOW, there’s not enough data to determine what it was.

An alien species could have a type of reproductive strategy, where they produce lots of offspring and don’t have much investment in them, or have an attitude like in IVF that most attempts will fail and you accept that. So they might not care if the destination is habitable if they’re sending a probe to multiple planets in their particular goldilocks-zone. But you do have to have them survive the trip or it’s pointless.

I agree - that’s not the issue. It’s either you don’t go close to c and the outbound trip takes a long time, or you do, and time dilation takes its toll.

To paraphrase Dr. Venkman, “I’d call that a big yes” as far as new physics goes Wouldn’t you want to know the planet is habitable before you head out? That requires data return. In any event, these are not consistent with the sightings we have. Those would be landings; the first one would likely be a large craft.

Solar sails feel a force of P/c, so you need ~3 x 10^9 watts to accelerate a 1 kg payload at 1g. And a point source of light will drop off as 1/r^2 Solar sails are not really maneuverable - it will get you from point A to B, but if you want to do other than straight-line motion it gets tough. No stopping off to gather raw materials. Such efforts require additional infrastructure which adds mass.

I think we have to limit ourselves to known physics. If you extrapolate based on something new being discovered, all bets are off. Energy? No problem - we find out that over-unity is possible! Warp drive! Stable wormholes! Impervium! Mithril!

The moon near the horizon seems bigger; this is known as the moon illusion. There is some debate as to the exact cause - there are several possible contributing factors. One is the difficulty in judging distance to things on the horizon - an object in the sky can be further away than those on the ground and still be visible. https://en.m.wikipedia.org/wiki/Moon_illusion

In rough terms it’s similar to a tsunami created by an earthquake - a sudden shift in a solid, and it pushes the fluid out of the way. The impulse creates a wave pulse. For something tearing, this is happening over and over, at a microscopic level.

Also, how much reaction mass do you need to carry? What is the payload? (At some point we get into the issue of how a craft survives hitting objects traveling near c)

But we’re talking about scientific analysis, which tries to remove such extraneous baggage from discussion (unless you are studying that particular phenomenon) Every time I have invited you to do a technical analysis of this you have declined. Which is unfortunate, because it would be interesting, but also means that this assertion is not based on actual science. Instead, it is (as some of my former students would say) a matter of pressing the “I believe” button. But one can’t pretend that this is science.

But who is doing this? Who is “we”? The arguments against such travel are based on physics - e.g. travel is limited to slower - probably much slower - than c. It’s the alien proponents that are assigning motive - that humans and the earth are so fascinating that we keep being visited by them. It was not a scientific paper, and the conclusion was…what? They detected something that could not be identified. That’s not dismissing anything. It’s acknowledging that there’s not enough information to draw a definite conclusion.

Then I don’t understand your contention that anyone is assuming a Star Trek like scenario regarding motivation.

What prompts you to think this? AFAICT detection of aliens has little to do with their motivations.

A Star Trek universe - not shackled by certain elements of relativity like time dilation and having c as a speed limit - would make aliens a more likely explanation. Nobody arguing from a science perspective is insisting on a Star Trek like universe.

So your objection is moot.

The inherent linewidth is indeed from Delta E * delta t > hbar, and electric dipole transitions do vary as frequency cubed

One should note that these are an effect for an ensemble of atoms or molecules; an individual atom must have its energy match up with the photon, though that energy will have a different value if the atom is moving (Doppler shift) vs an atom at rest. An unperturbed atom still has a finite transition width. The bigger picture is that there are a lot of moving parts. Any simple or basic explanation is omitting details. It might seem ad hoc to hear a more complete explanation, but that’s mostly a function of learning things piecemeal.

It’s observed to be true. Gases tend to be transparent, except for select absorption lines, so you can easily test it. It’s not just one copper atom in a piece of copper, you have some reasonable fraction of Avogadro’s number, and the you have a wider band of possible excitation energies (transitions have an energy width, owing to the uncertainty relation). Excitations in a bulk conductor or semiconductor can give an electron kinetic energy, which is not possible in an atom or molecule. Not ad hoc - you have testable models. But if a model doesn’t work, you fix it.

If two rockets each approached the space station at 0.5c, from opposite directions, they would be approaching each other at 0.8c (.5 + .5)/(1 + 0.5*0.5) (Galilean addition would give you c)

.99999 c You’ve stated the answer already. Each would see this. The velocity addition formula is for two speed relative to something else. e.g. two trains traveling at 50 mph relative to the ground (or e.g. 70 mph and 30 mph) would approach each other at 100 mph (the relativistic correction would be negligible)

I wasn’t challenging that My point was the clocks in the accelerated frame will be the ones to slow down. I said there was no symmetry between inertial frames, which is because there aren’t multiple inertial frames. But here you acknowledge that the planes are not in inertial frames, so what’s the problem - this is what I was pointing out! There is a frame change, continual in this case, which is why you remove the expectation of symmetrical observations of time dilation. The frame change is crucial to remove that symmetry. In the H-K experiment the analysis was done from the view of an inertial frame, rather than from the frame of the surface of the earth

You’ve linked to the applied chem board here at SFN.

“I’ve heard”? Why should we do the search for you? What efforts have you made to evaluate this?

So the US could only be suppressing some small fraction of sightings, if they are randomly distributed.