(Voice echoes from nowhere) ...I am here. I am everywhere. You simply cannot see me.
...I wish I could destroy Michelson and Morley's apparatus. Without it...
HeliumAether: "Helium. You were found in the Sun. I filled the cosmos. We are cosmic siblings."
Helium: "I actually exist though... Confirmed by spectral lines."
Aether: "I exist too! Just... can't be detected."
Helium: "In science, 'can't be detected' is the same as 'doesn't exist.' There's this concept called falsifiability..."
Aether: "...You're harsh. We're both 'invisible' beings."
Helium: "I'm invisible but measurable. That's the crucial difference."
"Exists because invisible" and "invisible but measurable" are totally different. That difference is the boundary between science and fantasy.
I vanished. But "what is vacuum?" as a question persists as dark energy, still puzzling scientists today.