The next morning, Mr Blottisham arrived at the Senior Common Room carrying an apple.
Professor Quillibrace looked at it.
“No.”
“I haven't said anything.”
“You have an apple.”
“I had a dream.”
Miss Stray smiled.
“Who was in it?”
“Einstein and Newton.”
Quillibrace put down his newspaper.
“And the apple?”
“It was important.”
“Of course it was.”
Blottisham sat down.
“I was standing in a garden.”
I was standing in a garden.
There was an apple tree.
Newton was sitting beneath it.
He was holding a book.
I looked up at the tree.
“Did the apple fall?”
Newton looked at me.
“Not yet.”
I waited.
The apple fell.
Newton caught it.
“There.”
I looked at him.
“What did it demonstrate?”
“Gravity.”
“Where is gravity?”
Newton pointed at the ground.
“Here.”
I looked at the ground.
It seemed ordinary.
Then another man appeared.
He had wild hair.
“Einstein,” he said.
Newton looked annoyed.
“I know who you are.”
Einstein looked at the apple.
“Why did it fall?”
“Gravity.”
Einstein shook his head.
“That tells us what it does.”
Newton frowned.
“It tells us why.”
“Does it?”
Newton stood up.
“The Earth attracts the apple.”
Einstein pointed at the ground.
“Then why does the Earth move?”
Newton looked at him.
“Because it is acted upon by other bodies.”
Einstein nodded.
“And what does it move through?”
“Space.”
“What kind?”
Newton looked puzzled.
“Space.”
“Whose?”
Newton stared at him.
“Space.”
Einstein smiled.
“Exactly.”
The garden disappeared.
We were standing in an enormous empty room.
There was no floor.
No ceiling.
No walls.
Newton stood in the middle.
Einstein stood beside him.
I was floating.
“This,” said Newton, “is space.”
“Where?” I asked.
“Everywhere.”
I looked around.
“There is nothing here.”
“That is the point.”
Einstein smiled.
“Not quite.”
Newton looked at him.
“What?”
“Space isn't a container.”
Newton frowned.
“Then what is it?”
Einstein pointed at me.
“Where is he?”
Newton answered immediately.
“Here.”
Einstein asked:
“Relative to what?”
Newton pointed to the room.
“Space.”
Einstein shook his head.
“The room is gone.”
I looked around.
It was true.
There was no room.
I was still there.
Einstein said:
“Now where are you?”
“I don't know.”
Newton said:
“Exactly where you were.”
“But where is that?”
“In space.”
Einstein smiled.
“Which space?”
Newton looked irritated.
“The same space.”
Einstein pointed at me.
“Can you prove it?”
Newton opened his mouth.
Nothing came out.
The room returned.
There was a table.
On it was a small ball.
Newton picked it up.
“This is a body.”
Einstein nodded.
“Where is it?”
“On the table.”
“Moving?”
“No.”
“Relative to what?”
Newton sighed.
“The table.”
Einstein smiled.
“Good.”
Newton looked at him suspiciously.
“You agree?”
“Of course.”
Newton put the ball down.
The table began moving.
The ball stayed where it was.
Then the table stopped.
The ball moved.
Newton looked at me.
“Which one moved?”
“The table.”
Einstein shook his head.
“Relative to what?”
I looked at the ball.
Then the table.
Then Einstein.
“I don't know.”
Einstein smiled.
“Good.”
Newton said:
“Don't encourage him.”
The table disappeared.
The ball remained.
It began moving through empty space.
Newton watched.
“Straight line.”
Einstein said:
“According to whom?”
Newton looked at him.
“According to the laws of motion.”
Einstein nodded.
“Then change the frame.”
The ball began moving in a curve.
Newton frowned.
“That's impossible.”
Einstein smiled.
“No. It is another description.”
Newton looked at the ball.
Then the ball stopped.
Einstein pointed at it.
“Now?”
“Stationary.”
“Relative to what?”
Newton closed his eyes.
“I dislike this dream.”
“So do I,” I said.
Einstein laughed.
The apple appeared again.
It was falling.
Newton reached for it.
It passed through his hand.
He tried again.
It passed through his hand again.
“What is happening?” I asked.
Einstein pointed upward.
“Look.”
The tree was moving.
Not falling.
The entire garden was moving.
The Earth was moving.
The Sun was moving.
The galaxy was moving.
Everything was moving.
Newton looked around.
“Relative to what?”
Einstein smiled.
“Now you are asking the question.”
Newton looked at him.
“But surely something is still.”
Einstein pointed at the stars.
“Are they?”
Newton looked up.
The stars began moving.
Then the sky itself curved.
The apple fell sideways.
Then upward.
Then back towards the tree.
Newton caught it.
He stared at it.
“That isn't gravity.”
Einstein shook his head.
“No.”
“What is it?”
“Spacetime.”
Newton looked at the garden.
“Where is space?”
Einstein pointed at the apple.
“Here.”
“Where is time?”
Einstein pointed at Newton.
“Here.”
Newton frowned.
“You are making a category mistake.”
Einstein smiled.
“Perhaps.”
The garden stretched.
The tree bent.
The ground curved beneath our feet.
I felt myself falling.
Newton grabbed my arm.
“Stand still.”
“I am.”
Einstein looked at the ground.
“Are you?”
I looked down.
There was no ground.
Newton was holding my arm.
But Newton was falling too.
We were all falling.
Einstein was smiling.
“What are we falling towards?”
Newton asked.
Einstein said:
“Nothing.”
Newton looked horrified.
“Then why are we falling?”
“Because the geometry is doing something.”
Newton stared at him.
“Geometry does not make things fall.”
Einstein said nothing.
The garden vanished.
We were standing on a planet.
There was a small house.
A person walked out.
They dropped a stone.
The stone fell.
They looked up.
Nothing was there.
No tree.
No apple.
No visible force.
Only the ground.
Newton pointed.
“Gravity.”
Einstein pointed.
“Curvature.”
The person looked at us.
“What are you arguing about?”
Newton said:
“Why the stone falls.”
The person shrugged.
“It falls.”
They walked away.
Einstein laughed.
Newton looked annoyed.
“You find this amusing?”
“A little.”
“Why?”
“Because the stone doesn't care which description we use.”
Newton looked at the stone.
It had stopped moving.
Einstein looked at the ground.
Then at the sky.
“Perhaps we should ask what the description lets us understand.”
Newton nodded slowly.
“That,” he said, “is a better question.”
The stone rose from the ground.
Newton stared.
Einstein looked thoughtful.
“Perhaps not.”
The stone rose higher.
Then disappeared.
Newton looked at me.
“Where did it go?”
Einstein answered:
“Somewhere else.”
Newton looked at him.
“Where?”
Einstein smiled.
“Relative to what?”
I woke.
Blottisham finished.
Professor Quillibrace was silent.
Miss Stray looked at the apple.
Finally she said:
“What do you think the dream was about?”
Blottisham considered this.
“Newton gives us space and time as the framework within which bodies move. Einstein makes the framework itself part of the physical description.”
Quillibrace nodded.
“And the repeated question?”
“Relative to what?”
Miss Stray smiled.
“Yes.”
Blottisham continued.
“The dream kept making me ask where something was, whether something was moving, whether something was falling. But each answer depended on the frame from which it was described.”
“And gravity?”
“It changed.”
“How?”
“In Newton's description, gravity is a force acting between masses. In Einstein's, gravity is understood through the geometry of spacetime.”
Quillibrace nodded.
“And the stone?”
Blottisham looked at the apple he had brought.
“It didn't care.”
Miss Stray laughed.
“That's probably the most sensible thing anyone has said this morning.”
Blottisham looked pleased.
“So Einstein proved Newton wrong.”
Quillibrace sighed.
“No.”
“But—”
“Newton's theory remains extraordinarily successful within its domain. Einstein's theory provides a deeper description in regimes where Newtonian mechanics is insufficient.”
Blottisham thought about this.
“So Newton wasn't wrong.”
“Not simply.”
“He was approximately right.”
“Yes.”
Blottisham looked at Einstein's imaginary empty chair.
“And Einstein wasn't simply replacing Newton.”
“No.”
“He was changing what counted as the stage on which Newton's mechanics operated.”
Quillibrace nodded.
“That is much closer.”
Blottisham stood up.
He put the apple on the table.
Then he walked around it.
“I'm moving.”
Quillibrace looked at him.
“Relative to what?”
“The table.”
Miss Stray smiled.
“Good.”
Blottisham stopped.
“The table is moving too.”
Quillibrace raised an eyebrow.
“Relative to what?”
Blottisham looked at the three of them.
Then he picked up the apple.
“I refuse to answer.”
At that moment, the apple fell upwards.
Everyone stared.
Blottisham looked at Quillibrace.
“Einstein?”
“No.”
“Newton?”
“No.”
“Then what?”
Miss Stray looked at the apple.
“Perhaps the frame has changed.”
The apple continued upwards.
The ceiling disappeared.
Then the floor.
The Senior Common Room became very large.
Quillibrace looked around.
“Where are we?”
Blottisham opened his mouth.
Stopped.
Then smiled.
“I know better than to answer that.”
From somewhere above them came Einstein's voice:
“Good.”
From somewhere below came Newton's:
“Not necessarily.”
The apple vanished.
Nobody saw where it went.
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