To truly understand relativistic effects, one had to begin with the concept of Four-Dimensional Space-time.
According to the current cosmological theories of the civilizations within The Great Voyage Organization, the Great Universe they inhabited was a Three-Dimensional Space, and with time added, it became Four-Dimensional Space-time.
And within this Four-Dimensional Space-time, relativistic effects had indeed already been proven correct.
Back in the Earth Era, humanity had already carried out relevant experiments, proving that the space-time Earth existed in was curved, and that the flow of time on Artificial Satellites moving in Earth's orbit was slower than the flow of time on the ground. There was no problem with that at all.
Then the question returned to The Great Voyage Organization's voyage.
Now, the various civilizations already knew how they should travel. To put it simply, they would use conventional thrust to push the fleet to extremely near light speed, then shut down the Strong Magnetic Propulsion Engine and let the fleet drift to its destination on its own.
It could be summed up in one sentence, but within that sentence, The Great Voyage Organization's fleet had to go through many stages. During this process, they would experience two changes to the Proper Time Axis. Their Event Light Cone, as well as the light cones of their point of departure and destination, would also undergo a series of changes. Four-Dimensional Space-time would also flip and invert during this process. The so-called past and future would also play out during this process, and these changes were the inner logic behind Time Dilation and Length Contraction.
But to truly understand The Great Voyage Organization's act of brute-forcing a two-million-light-year journey at conventional light speed, one had to start with the Twin Paradox.
The Twin Paradox was presumably already common knowledge.
Put simply, it