by Stuart Clark
Night assistants were readying the telescope, all in matching suits with heavy scarves and flat caps. Hubble ordered them around in tones that Lemaître had not heard since the battlefield, then led him to the base of the telescope.
The 100 inches of the telescope’s name referred to the diameter of the mirror, and only when Lemaître was standing under it did he realise how big 100 inches really was. The mirror was two and a half metres in width, held at the base of the telescope’s enormous tube by a great metal cradle.
‘Two tons of fused glass,’ said Hubble, patting the metal casing.
‘Took a year to cool it down so it wouldn’t crack.’
Lemaître stared dumbfounded. His eyes traced the telescope’s tube, which stretched upwards as tall as a house.
‘First target, sir?’ called one of the assistants.
‘Not just yet, I’d like to show our guest M31 first.’
‘It’s a bit low.’
‘Only a visual inspection, we don’t need photographic conditions.’
Lemaître followed as Hubble stepped assuredly in the darkness and they ended up on a gantry. From there they watched as the assistants worked a noisy control panel that fired motors to guide the telescope into place.
The great metal beast moved from bolt upright to a recumbent position and the workers manually swung a platform close to its side, where an eyepiece was fixed into a metal plate. They continued to nudge the telescope for a few moments until they called out ‘Ready’.
Hubble led the way and checked the view. ‘There you go, old boy.’ He pointed to a seat that had been cemented to the edge of the platform. Lemaître sat down gingerly, legs dangling over the edge.
He leaned into the eyepiece. The view was dark but textured and swam around as he adjusted his position. He relaxed his shoulders and, as he had learned, waited for his brain to catch up with his vision. When it did, the Andromeda galaxy resolved itself into magnificent life. It was a smudge, an indistinct pale oyster that looked as if it might disintegrate if he breathed out too quickly.
‘The light that’s striking your eyes started its journey almost a million years ago,’ said Hubble, ‘before any human being was alive. The galaxy you’re looking at tonight is how it appeared a million years ago, not as it exists today.’
Lemaître shivered with excitement. ‘Amazing.’
‘Quite a thought, isn’t it?’ agreed Hubble.
‘Have you read the H.G. Wells story about the time machine?’
‘I don’t really go for such works.’
‘It concerns a man who builds a machine to take him into the future. It strikes me, Dr Hubble, that your telescope allows you to see into the past.’
Hubble made a contented sound. ‘Never really thought about it like that, but I suppose it does.’
‘What, I wonder, does this galaxy look like today?’
‘I can tell you how to find out.’ Lemaître looked round in surprise.
‘Just sit there patiently for a million years, old chap. The light will have arrived by then.’
Hubble began his scheduled observing shortly after. An assistant manoeuvred the telescope into a different direction, this time setting the base close to the floor so that the great cylinder pointed closer to the zenith. Then the dome filled with an almighty rumbling as its motors moved it round to put the opening in front of the telescope.
Hubble grabbed a battered bentwood chair from near the wall and positioned it next to the eyepiece. He loaded a photographic plate into the camera slot and changed the eyepiece for one with a crosshair. He lit his pipe and settled in. For an hour he watched as the photograph collected light and slowly built up the picture, constantly checking the way the telescope was tracking, correcting for any drift in alignment.
One assistant showed Lemaître how to control the dome, edging it round as the telescope tracked to make sure it provided an unfettered view of the heavens. It gave him something to take his mind off the cold.
During a break Hubble came sauntering over, rolling his shoulders and drawing on his pipe, lighting his face with an orange glow every time he took a lungful of smoke.
‘Now you know how we track down the Cepheids in these distant galaxies. Patience and careful guiding. The pictures of the stars they take at Harvard are child’s play compared to the galaxies.’
‘And what, if I may ask, do you make of the spirals and their astounding velocities?’ Lemaître added one of Eddington’s crowdpleasing witticisms: ‘They shun us like the plague.’
Hubble rubbed his chin. ‘I must admit to being sceptical. It still seems extraordinary to me that such structures could be accelerated to such vast speeds. How could that possibly be true?’
‘How indeed?’ mused Lemaître, his mind brimming with possibilities.
‘Do you know something you’re not telling me?’
‘I thought you hated theory.’
Hubble’s face coloured briefly with the demonic glow of the pipe. ‘I do, but it doesn’t mean I’m not curious. Observations have a purity about them, whereas theories are always a matter of interpretation.’
Lemaître filled the dome with a belly-laugh. ‘I think of it the opposite way round.’
‘Come along, tell me what you know.’
Lemaître grinned. ‘Have you heard of the de Sitter effect?’
27
Brussels, Belgium
1927
Max Planck’s baggy eyes were duller than Einstein could ever remember them. Although the old master was nearly seventy now, it was not that long ago that Einstein had seen them blazing with a steel-blue challenge. The voice was diminished, too. ‘Why must you insist on derailing this conference?’
‘Because it threatens to derail physics,’ said Einstein unrepentantly.
‘You’re behaving like a curmudgeon. You contest every speaker even when they are delivering peer-reviewed and published work.’
‘The quantum theory is weak, yet you all discuss it as if it were proven.’
‘It is proven. It explains the structure of the hydrogen atom and why it absorbs only certain wavelengths of light perfectly.’ Planck sounded weary.
Einstein formed his words carefully: ‘It cannot be perfect if it relies on probability. How many times must I say this?’
They were standing to one side of the tearoom. Around them the invited physicists bubbled with conversation but did not approach. Outside in the autumn mists of Leopold Park lesser scientists waited, having made the trip to Brussels just to buttonhole the invitees as they were leaving.
‘Your objections are not scientific,’ said Planck. ‘This is about your hatred for German achievement, but remember this. The world has excluded us from experimental projects, theory is all we have left, and we have built a way of understanding the submicroscopic world that is the envy of other countries. Now the Danes have taken up our ideas, and you detest that success. Honestly, you can be as poisonous as the rest of the world.’
‘If you believe that, we can no longer be friends.’ Einstein crossed his arms, hoping to disguise his embarrassment at the schadenfreude he relished whenever German nationalism was damaged.
‘These men are brilliant,’ Planck continued, indicating the gathered scientists. ‘Bohr, in particular.’
The man in question was standing across the room, animatedly talking over the top of his teacup. He was just six years younger than Einstein, yet the gangling Dane still had the aura of youth about him. His hair was slicked back, as was becoming the fashion. Einstein had tried wearing pomade once at Elsa’s request and hated it so much he had refused to leave the apartment until it had been washed off.
‘They’re young and impulsive. They jump to conclusions without thinking about the consequences,’ said Einstein.
Planck pushed his round glasses up his nose. ‘They can’t understand why you’re being so obstructive, especially because you’re one of the fathers of quantum theory. This whole conference is about the consequences of these new rule
s. Think back to when I first talked about light as packets of energy. I intended the notion only as a mathematical trick to get the right answer, but you convinced us all that light really could be photons, little particles of light flying around instead of rays of light. It’s what got you your Nobel Prize.’
‘Don’t remind me of that.’ The mere mention of it caused him to shudder. When he had found the official letter waiting on his return from Japan, he had read with dismay that he was to be given the deferred 1921 award after all, but not for general relativity. The letter informed him it was ‘for his services to theoretical physics, and especially for his discovery of the law of the photoelectric effect’. If that had not been bad enough, the letter went on to make it clear that the award was being given ‘without taking into account the value that will be accorded your relativity and gravitation theories after these are confirmed in the future’.
Einstein had dropped the letter. ‘Confirmed in the future! Does Eddington count for nothing with these idiots?’
His annoyance had risen still more when he discovered that at the awards ceremony, which had taken place while he was in the Far East, the chairman of the awards committee had dismissed relativity as a branch of epistemology and therefore of interest only to philosophers. Incensed by the insult, when Einstein had turned up to give his belated laureate lecture the following summer, he had delivered it exclusively about general relativity.
He clattered his cup and saucer on to a nearby table. ‘Yes, Max, I did propose the photon of light, but I also pointed out the weakness of the approach – the way it leaves the time and direction of the emission of the light to chance – but no one has heeded the warning.’
Planck looked suddenly exhausted. ‘Oh, Albert, you talk in such dramatic terms.’
‘I will not have absurdities destroy physics.’
‘Even if the universe itself is absurd?’ Einstein scowled. ‘Particularly then.’
The delegates returned to the main room and sat around a horseshoe-shaped table arrangement, with the open end facing a blackboard. Einstein took his seat as Bohr called the meeting to order with the informal air of a bumbling schoolmaster.
‘This year,’ said the Dane, ‘a quite remarkable piece of work was published by our next speaker, Werner Heisenberg. I say, without doubt, that this is one of the presentations we have all been waiting to hear: Uncertainty as a Fundamental Constituent of Nature.’
Heisenberg marched to the front amid scattered applause. Unlike Bohr, who feigned youthfulness, Heisenberg really was in his mid-twenties and possessed the overt self-confidence that Einstein realised he himself had once displayed.
The young German placed his notes on the lectern, checked that there was chalk at the board and straightened his jacket. He was soon into the mathematics, filling the board with the runic symbols of science.
Einstein knew he should be impressed, both with the assurance of Heisenberg’s delivery and the robustness of the calculations, yet he experienced a visceral revulsion. He could see what none of the others could, with their wide eyes and enthusiastic nods of approval: the elegance of the mathematics was a Lorelei, and it was luring them all to destruction.
Heisenberg’s delivery became even more emphatic as he reached his conclusions. Writing his final equation on the board, he underlined it and punched such an emphatic full stop that the chalk split in two.
‘The mathematics can mean only one thing, that one can never know precisely both the position and momentum of a particle. The more precisely we measure one quantity, the less precisely we can determine the other. This is not a question of developing more precise instruments or measurement techniques; this is inherent. Uncertainty is a fundamental constituent of Nature.’
The physicists went into rapture, clapping their hands together and talking excitedly to each other. Heisenberg soaked it up, virtually standing to attention at the front.
Bohr rose from his seat, grinning from ear to ear. ‘Any questions?’
Einstein let the sycophancy die down before raising his own hand. He did not wait for Bohr to acknowledge his request.
‘Physics is about determining cause and effect. By weaving randomness into the fabric of reality, you lose that battle. Physics will no longer be about determining why things happen. You will destroy our subject if you cling to this line of reasoning.’ There was plenty of muttering at that. ‘There must be an objective reality from which all of the observable phenomena spring …’
‘Like Plato’s shadows on a cave wall?’ challenged Heisenberg.
‘What good does such thinking do us? We are physicists, not philosophers. We work with what we can see and what we can measure, and we test our theories by predicting what more we can see and measure. We must allow nothing into theory that cannot be tested. The uncertainty principle can be tested because no experiment will ever give both quantities precisely.’
Einstein made a dismissive sound. ‘I cannot hold with this new fashion for believing only in the things that can be measured.’
There was a change in the room, like water turning to ice.
‘But you’re the architect of that approach,’ stuttered Heisenberg, his confidence crumbling into incredulity.
Einstein moved his shoulders in a parody of a French shrug. ‘A good joke shouldn’t be repeated too often.’
Bohr spoke immediately, his tone firm. ‘No, you can’t fob us off like the reporters. This needs an answer. In 1905, while all other physicists were labouring under a belief in the ether, you said that if the ether could not be observed, it could not form part of a theory. Without it, you went on to derive special relativity, and now you tell us that such an approach is worthless?’
Einstein leaned back to try to hide a twinge of embarrassment.
‘It’s possible that I did use that kind of reasoning.’ The room stirred at the admission. ‘But it’s nonsense all the same.’
Bohr wagged a finger. ‘The mistake you make is to think that physics is about finding out what Nature is. But physics must concern itself only with what it can say about Nature. Scientists are not about the discovery of truth, we leave that to the Church.’ There was a ripple of laughter. Einstein waited for a beat. ‘Have your quantum theory if you want, but don’t believe it’s the final word. It’s a stepping-stone to a unified theory where certainty will exist whether we can observe it or not.’
‘And who will give us this unified theory?’ called one of the other physicists.
‘I am close to its completion.’ He looked around the tables and smiled inwardly. He had rattled them. It emboldened him to continue. ‘I’m not the lone voice you all think I am. Eddington in Britain works on this, too.’ A new thought fired him. ‘When Johannes Kepler asked Tycho Brahe whether he had observed the parallax and proved the movement of the Earth around the sun, Tycho told him he had not, and said that this proved that the Earth was stationary at the centre of the universe. Kepler believed that all it proved was that Tycho’s instruments were incapable of detecting the parallax, and in 1838 science finally developed telescopes capable of seeing the parallax. Without Kepler’s belief, he would never have devised his three laws of planetary motion, now thoroughly tested.’
‘But this is different,’ said Heisenberg, drawing attention back to the front of the room. ‘It’s not about better technology; it’s about there being a fundamental limit to the knowledge we can hold about particles. If we measure the mass of a particle with increasing precision, we automatically lose the precision we have about its position.’ As he spoke he regained his earlier certainty.
‘The same is true for the energy involved in a reaction and the time the reaction takes. Unless you can show that there is a mathematical error in the derivation of the equation, it shows that uncertainty is woven into reality – that the very act of observing changes the situation.’ His eyes filled with courage. ‘I will not listen to opinion or belief, even from you. But I will give up the uncertainty principle if you can prove – and I m
ean prove – that my equation is in error.’
Einstein pursed his lips. ‘Very well, I accept the challenge.’
Next morning, he spotted Bohr and Heisenberg chatting over breakfast. He sauntered over, trying not to grin. ‘Mind if I join you gentlemen?’
‘Please do,’ said Bohr.
Einstein pulled up a chair. ‘I have a little problem for you both.’ Heisenberg stopped eating.
‘It concerns the trade-off between knowing the energy of a process and the duration of the process.’ Einstein paused as the waiter poured him coffee. ‘Poached eggs, please.’
‘Yes, sir.’
Bohr and Heisenberg were as still as statues until he returned his attention to them. ‘Imagine a box filled with light and placed on a weighing machine …’
They both nodded, knowing that the weight of the radiation would be measured, too, and that this would be an excellent measure of the energy contained within the box.
‘Next to the box is a clock. The box opens at a particular time and a single photon is emitted. The weight of the box instantly changes, and that will give us the precise amount of energy released. The clock will have told us exactly when the photon was emitted. Both can therefore be known with certainty. There is no uncertainty between energy and time.’
‘It would be impossible to build such an apparatus,’ said Heisenberg quickly.
‘I’m not saying it would be possible to build such equipment now, but in principle such an experiment is possible. If the uncertainty principle is true, you should be able to give me a theoretical reason why the clock will be affected by the release of the photon. How can those two things be physically related?’
Einstein unfolded his napkin and dropped it on his lap as the waiter served his eggs.
‘It’s a nonsense without being able to perform the experiment.’ Bohr placed a hand on the arm of his companion. ‘He’s right.