The Senior Common Room at St Anselm’s was enjoying a cool morning of deceptive tranquillity. Rain tapped gently against the mullioned windows. Professor Quillibrace sat with his customary expression of faint disappointment in existence as a whole, peering over his spectacles at a stack of papers.
Mr Blottisham entered carrying toast and certainty in approximately equal quantities.
"I've solved time," he announced.
Miss Elowen Stray looked up from her notebook.
"You've solved it?"
"Yes. Everyone overcomplicates it. Things happen at the same time or they don't. If I ring the chapel bell and Cook drops a tray in the kitchen, either they happen together or they don't. One can't have different opinions about reality."
Quillibrace slowly lowered his teacup.
"Ah," he said softly, "you have arrived at precisely the assumption that physics spent the twentieth century murdering."
Blottisham sat down.
"No, no. Reality cannot depend upon who happens to be looking."
"Quite so," said Quillibrace. "And fortunately it doesn't. The confusion lies elsewhere."
Elowen leaned forward.
"The issue isn't really observation, is it?"
Quillibrace gave a slight nod.
"Indeed. People commonly tell the story badly. They say special relativity teaches us that observers disagree about simultaneity, as though two gentlemen were squabbling over the colour of a waistcoat."
"Which is often worthwhile," said Blottisham.
"It is not," said Quillibrace. "The issue is not disagreement. The issue is that what appeared to be a neutral procedure for determining simultaneity turns out not to be neutral at all."
Blottisham frowned.
"But surely simultaneous things are just simultaneous."
"Suppose," Quillibrace said, "you wish to determine whether two distant events happen together. One occurs at the chapel. Another occurs at the boathouse."
"Simple," said Blottisham.
"Excellent. Explain."
Blottisham opened his mouth.
Closed it.
Opened it again.
"Well...one checks the clocks."
Quillibrace folded his hands.
"And how do you make sure the clocks agree?"
"Set them together."
"They are miles apart."
"Send instructions."
"At what speed?"
Blottisham stared.
Elowen's eyes brightened slightly.
"Oh."
Quillibrace inclined his head.
"Yes. The difficulty enters quietly. To coordinate clocks, signals must travel. Einstein used light because its speed remains invariant. But the moment you use light signals to define simultaneity, the frame used to coordinate those signals enters into the procedure itself."
Blottisham blinked.
"So the clocks aren't revealing simultaneity."
"They are constructing it."
Silence.
Blottisham looked personally betrayed.
"Constructing it?"
"Not inventing it whimsically," Quillibrace said. "Constructing it structurally."
Elowen had begun writing rapidly.
"So simultaneity stops being a discovered feature of reality and becomes something instantiated within a particular system of relations."
Quillibrace smiled faintly.
"Very good."
Blottisham looked alarmed.
"Instantiated?"
"Within the framework we're discussing," Elowen said thoughtfully, "instances are always cut from systems of relations. So a frame isn't merely a viewpoint. It's a structured constraint on what relations can be coordinated coherently."
Blottisham stared at her.
"I'm afraid you've begun speaking Quillibrace."
Quillibrace looked mildly pleased.
"The essential point, Mr Blottisham, is that there is no hidden master clock sitting behind the universe keeping proper time for everyone."
"But there must still be a real ordering underneath."
Quillibrace sighed.
"Ah yes. Newton's ghost enters carrying a pocket watch."
He stood and walked toward the windows.
"Classically one imagines the world sliced neatly into universal layers: everything happening now, then everything happening later, and so forth. Reality resembles a loaf of bread passing through a slicer."
Blottisham brightened.
"Yes! Bread!"
"Special relativity quietly removes the slicer."
Blottisham's face fell.
"There is no uniquely privileged way to cut the loaf into universal presents."
Elowen looked out into the rain.
"So what collapses isn't temporal order itself."
"No."
"It's the privilege of one global ordering."
Quillibrace nodded.
"What disappears is not structure but a particular location of structure."
Blottisham frowned.
"I dislike where this is heading."
"Quite understandable."
"If there is no universal now, doesn't everything dissolve into chaos?"
Quillibrace returned to his chair.
"Curiously, no. This is where many people imagine reality becoming foggy and mysterious."
He lifted a finger.
"What survives are invariants: stable relations connecting different frames."
"So things still remain constrained," Elowen said quietly.
"Precisely."
She looked down at her notes.
"So instead of a shared present underlying everything, there are consistency relations connecting differently generated presents."
Quillibrace's eyes narrowed approvingly.
Blottisham sat motionless.
After a long pause he said:
"So reality is not one gigantic synchronised committee meeting."
"No."
"It is several committee meetings with rules governing correspondence between minutes."
Quillibrace looked surprised.
Elowen looked surprised.
Blottisham looked surprised.
Quillibrace slowly picked up his teacup.
"Mr Blottisham," he said, "I believe that may be the most correct thing you have ever said."
Blottisham sat up proudly.
Then he frowned.
"Though now I'm troubled."
"Naturally."
"If there is no universal present..."
"Yes?"
Blottisham looked around nervously.
"...how do I know whether Cook has already made scones?"
Quillibrace stared at him.
"My dear man," he said at last, "there are limits beyond which ontology cannot help us."
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