18
What David had in his box was a sheet of some stretchy netted material with holes, a couple of marbles, a large elastic rubber band and a pencil and he was really quite keen to move on from this frivolous moment that Brian and Helen seemed to be sharing so that he could discuss his ideas about gravity and black holes.
Like a magician preparing for his greatest trick ever, David removed the lid of his shoebox and one by one he removed the items from the box, placing them side-by-side between himself and Helen.
In the merriment of the moment Helen did not notice how her shirt was sticking to her until Brian’s laughter abruptly stopped as his gaze paused well below Helen’s chin, before he could tear his eyes away and onto David’s presentation.
Suddenly Helen felt the clinging of her shirt and she stopped laughing as she pulled her cardigan around her. Annoyingly she felt her own flesh heat-up as she too turned a delightful pink to match the colour Brian had displayed only moments before.
She too focused on David’s presentation.
“Right,” said David, “yesterday we parted after deciding that time was a static and inert state and that time was experienced within a universe and varied with the relative speed of that universe through what we have been calling ‘bigger space’.
“We also agreed that if a universe were to slow to a stop within bigger space then it would cease to have time as we know it and that in all probability the universe would simply restore itself to the same state as that of bigger space.
“This ‘bigger space’ is the next dimension that I have been saying we cannot perceive from within our own dimension.
“Now, if a universe can lose bits of itself to bigger space, how do you think that would appear from within the universe?”
Helen and Brian gazed at David. Neither of them had fully recovered from their giggling fit and neither of them had fully recovered from their respective embarrassments. They continued to say nothing.
David sighed, he wasn’t sure what was happening with these two but he was determined to make his point. Reaching for the stretchy netting, David placed it over the open top of his shoebox. He secured the net by placing the elastic band around the sides of the shoebox so that it trapped the edges of the net leaving the clear surface of the net smooth over the open box top.
Next he placed the biggest of the marbles onto the net so that it stretched slightly at the point where the marble rested.
Realising that neither Brian, nor Helen, were likely to say anything for the moment, David went on. “I think that from within the universe, if any part were to ‘slow’ it would appear to drag and make a sort of gravitational well within the universe.
“I think it would start to attract other bits from near it towards itself and I think that as it became more and more substantial it would make a deeper and deeper gravitational well in the universe.” David set the second, smaller, marble and pushing it caused it to travel round the first marble is a rapidly decaying orbit before it settled touching the first. The stretchy net sank further into the box.”
Brian recovered first. “That looks like those models that depict gravity and black holes.” he said.
David took the second of his marbles from the net and once again set it in motion so that it spiralled around the first marble before coming to rest touching it.
“Imagine how that would look if there were hundreds of thousands of smaller marbles all spiralling into the centre.” he said.
“It would be like stars spiralling into the middle of a galaxy – like the milky-way.” said Helen.
“And what if the mass in the middle gathered so many stars…” as David said this he used the flat end of his pencil to push down on the big marble “that it was able to leave the universe altogether?” and with that the marble dropped through the net into the shoebox.
“What would that be like from within the universe?” asked David.
Brian looked into the box. “It would be exactly like the black hole effect that’s currently being reported by scientists. Current belief is that at the centre of every galaxy in the universe, there is a black hole which is acting as the engine driving the Galaxy to spiral in on itself”
“And Steven Hawkings came up with a theory of ‘Event Horizons’ as being the point at which an object – including light – when approaching a black hole could not escape the pull of the black hole,” continued David.
“So if this box was very big, the dip caused by the large marble would localised so that most of the stretchy net would be flat. That would mean that a marble placed on the net where it is flat would not, automatically, travel towards the bigger marble nearby but if it did drift too close then it would start to roll toward the bigger marble.”
Helen joined in. “and the point where the newly attracted marble could not change its commitment to the big marble would be the event horizon?”
“Yes.” chorused the men.