Kaitiakitanga. Guardianship. What does it mean to protect the land? The land does not exist independently of life. Is the land separate from the heavens? Or, is matter separate from space? In physics, we say that the moon does not exist if no one looks at it. And this is true, once you see that your reality is constructed in your mind. You observe the universe from where you think you are, and you are because you think.
In the Big Bang view of the universe, there is no place for the present time. We are supposed to believe that homo sapiens randomly appeared some 14 billion years after the origin of space and time. Instead, we should look back to the illusion of the Big Bang from our place, here and now. The most universal object in our sky is the cosmic microwave background radiation (CMB). It arrives at Earth from all directions in space, with a temperature close to 3 Kelvin. The temperature of this light is not exactly the same everywhere, but it almost is, a fact that is impossible to explain in the Big Bang picture. And yet, a precise value for the frequency of light is not a strange idea in physics. The quantum states of atoms are defined by precise frequencies of light, and the annihilation of a particle and its antiparticle results in a photon (a quantum of light) with an energy equal to twice the mass of the original particle.
Did we just say that photons have mass? Not exactly. When we talk about a photon travelling at the speed of light, it has no mass at all, but it has an energy, and this energy might have been borrowed from particles that carry mass. For the CMB photons, these particles will be neutrinos. Neutrinos are everywhere. They became a theoretical necessity in the early 20th century, when missing energy was observed in the beta decay of radioactive elements. In this process, a neutron in the nucleus of an atom lets out an electron, and becomes a proton. Now in particle physics, there are many conservation laws. What goes in, must come out. A familiar conserved quantity is energy. Another one is lepton number. An electron is a lepton, but neutrons and protons are not, so we need the antineutrino (an anti-lepton) to balance out the electron in the beta decay process. This is the basis of the so called weak interaction in particle physics, which we now consider as a foundation for a theory of quantum gravity. In other words, the oddity of neutrinos is the key to seeing how all the forces of nature may be unified.
To give particles mass in the Standard Model of all known particles, we usually introduce the Higgs boson, but the Higgs need not be a fundamental concept in the bigger theory of quantum gravity. Our Higgs energy comes from a combination of two measurement scales: the neutrino mass scale, which defines the largest possible scale of observation, and the Planck scale, which defines the smallest scale. The largest scale is the size of our observable universe, and is associated to the creation time of the CMB. Cosmological time is therefore determined by the measured temperature of our environment.
The weak force carriers (the W and Z bosons) were needed to explain why nuclear processes are short ranged, in contrast to electromagnetism, which is mediated by the massless photon. In the Standard Model, we needed to cheat with the neutrinos and pretend that they are massless too, but oscillation experiments prove that all neutrinos carry a small mass. The CMB temperature corresponds to a mass of only 0.00117 eV, in convenient electron volt units. Once we understand that the quantum vacuum pairs small and large scales to create rest mass, we can also explain why some neutrino experiments see a sterile state at around 1.3 eV, because this is the energy of a CMB neutrino in the early universe.
Matter is not separate from space and time. The Earth is the center of your universe. Papatuanuku and Ranginui hold each other up, wherever life is created. You carry one small hourglass, that marks off one hour of local time, sufficient to make precise the hour after sunset. The southern night sky is full of stars and galaxies, slowly revolving around the celestial pole. You know that the time difference between the setting of certain stars marks your latitude. But you know more than a few stars. You are familiar with the stories of thousands. In the dim twilight, you spot a familiar rocky outcrop in the distance. Then you sit down in the sand beside the hourglass, waiting for the last few grains to drop, as you observe which stars fall below the horizon.
The ticking Swiss clock fixes in your mind the idea that time is out there with space, independent of the Earth, independent of the observer. Yet, if you watch the birds fly over the sea, if you watch the sun’s shadows, and if you measure the tides accurately on the mangrove flats, you will know your longitude relative to your neighbours without using a mechanical clock. Nature provides a multitude of clocks.
In physics, there is no such thing as absolute time. For convenience, we define a second as a certain fraction of a day, and we make sure that this time interval matches the definition of a second on an atomic clock. Only the speed of light is locally constant, as it compares time and space. One might carefully consider all possible mathematical rules for the passage of time measured by an observer, and this was done by the modern philosopher G. J. Whitrow. He came up with a list of axioms for clocks, including:
Axiom I: if the unit of time on John’s clock is altered, then all times measured by John are multiplied by the same factor.
Axiom II: the time interval between two events, as seen by the observer John, are independent of the origin of the cycle of time on John’s clock.
Both axioms seem eminently sensible, and are quite true for the old theory of Special Relativity. However, we have already thrown out Axiom II, because our cosmological clock does have an origin in time. Taking only Axiom I as a necessary feature, and remembering that energy is related to time by the Uncertainty Principle, we find the rule (a geometric mean) that relates the Higgs scale to neutrinos.
By studying anomalies in neutrino experiments, we have been forced us to consider both kinds of clock: a local clock and a cosmic clock. Neutrinos have shown us that the quantum vacuum is a cosmological concept. Local rest mass, it turns out, is a stable quantity except in environments where relative accelerations are extremely low, like on the outer rims of galaxies. A particle that is truly free, and not accelerating at all, has zero mass. This gets rid of the dark matter problem that plagues the Big Bang theory. Our old ideas about gravity only make sense locally.
In classical physics, Maxwell’s demon is promised immortality in a clockwork machine, but we all know from experience that our perception of time depends on the task being processed. In a single moment, we may live an eternity, returning to our roots in the heavens.
Classical prejudices about time in complex systems belong to thermodynamics, the science of engines and refrigerators, where there is no true arrow of time. Entropy (disorder) in a system appears to increase in a forward time direction only because we have set up special initial conditions. A coffee mug that you smashed on the floor this morning is not a random bit of space junk, but something that evolved together with you over millions of years. At a fundamental level, some argue that entropy comes down to the asymmetry between the emission and absorption of radiation, where the process of emission must take into account every atom in the distant universe that eventually absorbs a photon of the light. But each individual photon is simply emitted somewhere and absorbed elsewhere. Complex correlations between events ultimately depend on the arrow of time for an observer like us.