BONUS - the conversation Pg. 285
‘It’s natural for people to look at the world and see things happening in time. It’s natural for us to think of time as a totally
separate, constant thing, completely outside our physical world.
Turns out, that’s not quite true.’
‘It’s not?’ Craig prompted, finally getting something out of these two. David had read Shaun’s papers online, so many of these concepts weren’t foreign to him.
‘Time’s wrapped up in our physical world in a very real way. It even has shape.’
‘Wait a second,’ The reporter grinded the gearbox into third as he began to slow. They were reaching the outskirts of the city. ‘You’re telling me that time has shape?’
‘… and it’s not constant either. It’s running at all sorts of rates, faster and slower, all over the universe depending on what’s going on there. Time is affected by a whole bunch of things, physical things, things like gravity, and speed.’
‘Time is affected by gravity? But it doesn’t have any weight, how can gravity have an effect on it?’
Shaun smiled a little. It was nice to speak to someone who, although not familiar with the subject, had the brains to ask the right questions. It was a far stretch from the tenth grade at Masonville High.
‘Tell me, do you think light has weight?’ Shaun asked, warming to the challenge.
‘Ah, I don’t really know. I don’t think so,’ Craig stammered. ‘But gravity affects it?’
‘Sure, what do you think a black hole is?’
‘It’s what my mother told me I had instead of a stomach,’ David put in, hinting that he was coming out of his grump.
‘Ha! I’m sure she did. Still, a black hole is an object so dense, and with such a massive gravitational pull, that not even light itself can escape it.’
Craig held up his media credentials as he slowed for yet another ‘police’ checkpoint.
Outside the streets became more dense. The old mixed with the new in a strange dance of residence.
Shaun continued on, explaining the doppler effect and both sound and light.
Craig shook his head in wonder. This was a far cry from international politics, which was his specialty. He found it hurt his head.
‘The Doppler effect applies to all electro-magnetic waves, and its how police radars are used to trap us as we speed down the motorway. Don’t think they have any around here though!’ Shaun said, looking out the window at the low-tech city now creeping up all around them.
‘Okay, so how does all this relate to time?’
‘Well,’ Shaun began, ‘the word ‘frequency’ means the number of cycles per second, right? If the frequency of light goes down when something is moving away from us, the waves sort of stretch out like the sound waves from the ambulance that is speeding away. In the case of stretched-out sound waves, we get a lower pitch, but in the case of light, it gives us a ‘red shift’.
The same thing happens as a result of a gravity, you could say there is a gravitational ‘red shift’. Just as if it were moving away, In both cases the number of cycles of the wave that pass a certain point every second is reduced.’
‘So, if light arrives at us with a lower frequency, with a red shift, we could say that either the light frequency had been reduced, or equally that time from that object moving away runs a bit slower than where we are. After all, we can only measure frequency using clocks, and a change in frequency is the same as a change in clock rates.’
‘Hey, that’s cheating!’ David said, accusing.
‘Well,’ Shaun continued, now in full lecture mode, ‘The cycles of light would make a perfectly good clock. In that case, the gravitational red shift would amount directly to a change in clock rate. And hence, a change in time.’
‘Aw, I don’t know. What if you used another sort of clock? You don’t usually measure things with a light-wave clock. You can’t claim that time itself changes, unless all clocks are affected in the exact same way.’ David interjected. Craig was still wrestling with light being affected by gravity.
‘They are. All clocks, of any kind are affected in the same way. The activity of a clock has some associated energy, and, like all forms of energy, this has some weight.’
‘You mean like Einstein’s thing? His energy thing? Equation?’ Craig jumped in.
‘I mean exactly that. Einstein showed the relationship between energy and weight…or more correctly, mass. E=mc squared. The energy of something is equal to its mass multiplied by the speed of light squared.’
Shaun continued his lecture for the next half an hour, discussing the theories, the misconceptions and the work that had already been done on the subject.
‘Oh come on, you can’t tell me this stuff has been measured? Surely it’s too small to make any kind of difference,’ Craig said when Shaun told him that these things had been proven.
‘Well, yeah, but the effect of gravity on things is really tiny here on Earth, but on a universal scale, when you start dealing with masses, and speeds and distances that exist in the whole cosmos, then you really are getting to massive and easily measurable effects.’
The CNN news man accepted the information on face value. He’d stopped following a while back.
‘There’s a long stretch between seeing that gravity has an effect on time and building a time machine,’ he said.
‘Yeah I know. Tell me, how much do you know about ‘Relativity’?’
‘Not a lot. A bit I guess. All things are relative? For every action there is an equal and opposite reaction?’
‘That’s Newton, not relativity.’
‘Oh,’ Craig said, a tad embarrassed.
‘Relativity is all Einstein. In essence, what relativity says is that space and time are not absolute, but relative to both the observer, and the thing being observed. You see basically, the faster you go, the more compressed you become, relative to an observer, even your clocks run slower, but locally nothing is weird at all.’
‘And this happens? I mean it really happens?’
‘It happens every day. The issue is, of course, that the changes are far too small to make the slightest detectable difference to us, but on a universal scale, for other things: light, gravity, the universe itself –, these things are matters of consequence!’
‘So, gravity slowing things down … time running faster in space, that doesn’t seem right.’ Craig said, struggling.
‘We naturally base our understanding of the world on our experiences, the same went for Einstein. He couldn’t include gravity and motion in his special theory until he gave up something he thought was fixed, namely the normal rules of geometry. It was wrong to think that gravitation causes a warping in time, but rather that gravitation is a warping in time! Gravitation is not a field of force at all, but a curvature of space-time.’
Craig’s face furrowed with the effort of squeezing these new and foreign concepts into his brain.
‘How does all this come to something that may make time travel possible? Well, it brings us right back round full circle to black holes.’
‘So, what you’re saying is that a black hole is a big bend in space-time?’ David jumped in again.
It was a semester’s worth of work to get Shaun’s his high school students to get the idea that a wave could be used as a clock, let alone jump from ‘acceleration is the same thing as gravity’ to the effect of curvature in space-time … and he had explained the whole lot in the space of a few minutes in a Pakistani road trip.
‘David my friend, you sure you don’t want to come and teach high school physics with me when all this is over?’
David smiled. He was excited as he had found an intellectual equal, albeit in a different field, and was learning some really cool stuff.
‘So you think that black holes are the key to time travel?’ Craig threw back, his eyebrows still crunched together quizzically.
‘Sort of, not directly, but sort of. You see the size of a black hole is …’