In connection with the landing of the Perseverance rover on Mars yesterday. Do you want to feel like the owner of secret knowledge inaccessible to mere mortals? We'll arrange it now.
The recipe is simple: we take the special theory of relativity (SRT), which describes the mechanics and kinematics of motion at near-light speeds, and we find that in it the speed of light is invariant when passing from one inertial frame of reference to another. What does it mean? This means that in any inertial system (that is, one that does not move under acceleration) the speed of light is the same in all other inertial systems, even if they are moving somewhere relative to ours. And it doesn't even matter at what speed and in which direction.
From this, by the way, follows one cool brain-enduring conclusion, which is briefly mentioned in textbooks and is immediately forgotten forever - in an inertial system, the sum of any sublight speeds cannot exceed the light speed. For so bequeathed the great Hendrik Lorenz, who poked his coefficients into transforming the name of himself.
But we got distracted. What's with the rover? With him, everything is in order, but numerous enthusiastic streams, articles, notes and podcasts have broken off like a chain - they say that now the signal from Mars goes to Earth for 11 and a half minutes, so we cannot monitor the landing and control it in the mode real time, so machine learning automatics control the landing there, and when the signal of success comes to us, it means that the rover has already landed 11 and a half minutes ago. Well, stuff like that.
And, damn it, even, at first glance, technically literate people, who seem to be versed in space, astronomy, celestial mechanics and everything else, are joyfully carrying this nonsense with powerful streams. So, I responsibly declare that this nonsense is nonsense !
There is no "11 and a half minutes delay"! That is, yes - the signal from Mars now takes just that much time, if you measure this time in such a system where the Earth and Mars are more or less calm. But this is not a "delay" in relation to the time of the event, about which we know that it came according to our clock, that is, the signal about which came from Mars in our direction. Why? Because in SRT, "simultaneity" is just as relative as speed and in the same way cannot exceed the speed of light in an inertial system!
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This is a kind of mind trick, caused by the fact that people are used to considering their inertial reference system as something more special than an infinite number of others, and also by the fact that distances of such orders as hundreds of millions of kilometers are difficult to perceive by consciousness, accustomed to operate with more everyday values ... Something like "northern hemispheric chauvinism", when we subconsciously wonder how it is summer in Australia in January, or perceive the map of the world with the south at the top as something unnatural.
And, of course, all this is nothing more than an attempt to idly add more information, as the title of the article is about. Happiness to you.