If you followed this through, you’ll realise that you and Nefertiti don’t agree and we can’t have that. Never let the sun go down on an argument. So how can we reconcile your apparently irreconcilable views - how can illumination be both simultaneous and not simultaneous? Time for Uncle Albert to whisper in your shell-like: “I only said the speed of light must always be the same, regardless of any relative movement of the light source and the observer - I didn’t say that about time". So what we can propose is that the time at which an event occurs depends on the movement of the observer. If two observers are moving relative to one another, it is indeed possible for events that seem simultaneous to one of them to occur at different times, from the point of view of the other.
Best to bear this in mind next time you are flying to the other side of the world and you make a romantic agreement with your true love at home, each to kiss the other’s photograph at exactly the same instant during the flight. What does it mean, at the same instant? “It’s complicated” is not the phrase you want hear in relation to your one true love. The best answer is to go for a really long kiss, either side of the agreed time, to give you a reasonable margin of error. Your fellow passengers may find this a little weird but it’s a small price to pay (oh, but who stopped kissing first? On reflection, your love is probably doomed anyway, so let’s just focus on the relativity).
Our next job is to investigate this mathematically. To start this we’re going to need a new Gedankenexperiment. This is because – as we shall see – relative motion messes with both time and space and to begin with we need to separate these effects to make the analysis manageable.
