michel123456

How do we reflect light from the Moon? There is an approximate 2 sec gap with the Moon. That means 4 sec to go forth and back. During those 4 sec the Earth & Moon have moved respectively. How do we catch back the signal? from another location?

I don't question the speed of light. The question is: when I look at the (speculated) alien, does he see me? The answer is : No. The next question is: what is he looking at? Strange's answer is: he is looking (he was looking) at the Earth as it was 2 million years ago. I am questionning Strange's answer. I say: how can we check that?

Physical interaction. In this case gravitational and electromagnetic. What is troubling me is this: We are traveling in the universe together with planet B, that we observe 1 million LY away and 1 million years in the past. There is no physical way (no bridge) to go to planet B and check what the observer there was looking at . All the travels that we can do are limited by the speed of light. IOW we suppose that the observer there was in the universe with the company of a younger Earth. Respectively, today we may be observed by future astronomers looking at us in their telescopes from distant planets. We cannot see them, but we suppose that they will be on one of those planets we observe today. Again, it is a supposition, there is no physical way to prove that. Those suppositions are based on the way we picture ourselves how time works. It may be correct but it may be wrong, we cannot check.

IOW, correct me if i am wrong, what we call "interaction" is not exactly an "interaction" between 2 objects, it is a triangle connecting (to make it simple) A the observer, B the observed object and C the observer "as it was in the past". And when we speak about "interaction" we suppose that A and C are the same objects.

OK I can understand that. Agree. This part of your answer is based on our current understanding of time. Does that mean that by any means (gravity & EM radiations), the interactions are delayed? I mean we are receiving EM radiation from this planet today, and this planet is NOT receiving EM from us now, but from the Earth as it was 2 million years from now ?

I cannot see the depiction on my computer here. Am I missing some instructions?

This is a question: Suppose that I am looking in my telescope to a distant star 1 million light years away. Around this star is a planet. On this planet I see an alien observatory and an alien scientist looking in my direction. Can he see me?

That sounds like a search for absolute motion.

The answer is clear like crystal water.

Agree. That would be a constant. But isn't it relative as well, in the sense that there exist no absolute horizon?

When you say "single photon" what do you have in mind? A point particle? Or a wave, like a line? or the circumference of a circle? Or a wobbling surface?

I am not questionning invariance of C. --------------------------------------- If the neutrino has mass, its velocity is relative and thus a neutrino should not have a velocity. It would be like asking "what is the velocity of Swansont" ans someone to shout "MOVING IN WHICH REFERENCE FRAME!?!?"

Correct. (BTW I looked in wiki the distance on Earth is approx. 5km, not 11) The horizon is the same for all observers that are in the same conditions (on Earth at sea level) no matter their state of motion. If you run to the horizon, you will never catch it. The distance to the horizon does not change. How do you call that in physics?

I am not questionning invariance of C. There are too many concepts here where none is synonym of the other. Frame dependent, relative, constant, absolute etc. IMHO something can be alltogether invariant and relative. As an analogy: When you stand upright at sea level, you horizon is at approximatively 11km away. The distance to horizon is relative, because it comes from you, you are at the centre of vision. The distance is also constant, if you walk to your horizon, the distance will not diminish. I know it is simply an analogy, distance is not velocity, but it is an example where something relative is also constant.

My comment was related to DimaMazin's statement that: the first part is understandable: "Neutrino has mass therefore has only relative velocity". Agree, I question the second part: "velocity of light isn't relative"

That doesn't make much sense. If all velocities under SOL are relative, if a velocity very very close to SOL is relative, then SOL is relative too. Only that this relativeness is the same for all observers.

Also I have to admit i have no idea how swims a fish.

No, i was thinking about the butterfly effect. In fact I was thinking that the butterfly effect does not appear, IOW you do not observe a large wave coming out from the fact that small fishes are swimming in an aquarium.

Yes. Beejewel looks like a wonderful person.

This is the field of research of physics Nobel Prize Serge Haroche. it goes far over my head. Search this below Quantum non-destructive observation of trapped photons, detection of field quantum jumps, reconstruction of non-classical field states, direct monitoring of decoherence and quantum feedback demonstrations (2006-2011)

When swimming, a fish must displace some amount of water from front to behind, since water is incompressible. This movement must (I suppose) create some wave at the surface. The wave will be distributed according to the distance from the fish to the surface, as you said. Anyway, since there are a lot of fish in the sea, there should always be some waves even without any wind. In your tank, when the fish are swimming, do you observe anything like that or is the surface perfectly calm?

When a fish swims, does that provoke some turbulence at the surface? If not, how is that possible?

From your description it looks to me you are doing great. Maybe you need a new challenge."more experimental work, or more reading, give classes, go to conferences" would not be my personal dream but that's up to you. My goal was always to escape from studies and engage the real world with a good diploma. I have absolutely no respect (sorry for that) for the people who remain a life long in the academics cocoon no matter how intelligent they are. My simple life advice is the same I say to everyone (at the risk of being gnagna): Never look back. Like an mountaineer, always proceed. Also it is interesting to note that you have the chance to choose what you will do next. The vast majority of human kind does not have that chance, did not and never will You are one of the few. And always keep in mind that some other people will hate you for that.

I believe Syn5 is trying to make a fool of this forum.

It looks to me I have seen that before.