Mae-Wan Ho Bioelectrodynamics Laboratory, Open
University, Walton Hall, Milton Keynes, MK7 6AA, U.K.
Fritz-Abert Popp - International Institute of
Biophysics, Technology Center, Opelstrasse 10, 6750 Kaiserslautern 25, FRG.
First presented at the 3rd Camelford Conference on The Implications of
The Gaia Thesis: Symbiosis, Cooperativity and Coherence, November 7-10,
1989, The Wadebridge Ecological Centre, Camelford, Cornwall; revised
The Ufaina Indians in the Colombian Amazon believe in a vital force
called fufaka which is present in all living things. The source of
this vital force is the sun. From the sun, it reaches earth and is
constantly recycled among plants, animals and human beings. Each group of
beings requires a minimum of the vital force in order to live, and is seen
to be borrowing the energy from the total energy stock. When any being
dies, the energy is released and goes back to the stock. Similarly, when a
living being consumes another, for example, when a deer eats the leaves of
the tree, or a tree extracts nutrients from the soil, or when people cut
down trees to make a clearing, the consumer acquires the energy of the
consumed. What is of importance to the Ufaina is that the vital force
continues to be recycled from one species to another in such a way that
not too much accumulates in any one of them, since this could deprive
another of its vital force, and upset the natural balance (von Hildebrand,
It is a remarkably coherent cosmology: a natural ecological wisdom that
understands nature as a dynamically balanced whole linked by energy flow,
with the energy arising ultimately from the sun. This cosmology is based
on a total understanding that comes not just by scientific observations,
but from an intimate experience of nature from within. It took Western
science hundreds of years with many sophisticated instruments and a number
of false starts and turns in order to arrive at a similar picture. As
Peter Bunyard (1989) says, 'The Indian conception ... is not in principle
far removed from... [our own] notion of energy flows and foodweb and
chains, with the sun providing the necessary energy.' The major difference
between them and us is that whereas they live by their wisdom and see
themselves as part of nature, we have placed ourselves above and outside
the balance of nature, to the peril of all.
What we want to do in this paper is to present a vision of ecological
balance from contemporary Western biophysics which shows just how
intimately we are connected with one another and with nature. How all
nature is one resonating and intercommunicating whole. We shall be drawing
from the work of many, including ourselves, who have derived inspiration
from the union of biology and physics.
Let us begin with the western ecological versionof energy flow. The
energy of sunlight is absorbed in individual packets or quanta called photons
by chlorophyll, the colour pigment in green plants. This energy in
each quantum goes into an excited electron, which, in the course of
falling back to the ground state, travels around the body, its energy
meted out to support all vital activities such as growth and
differentiation, sensations, and movements. When animals feed on plants or
on other animals, they are taking in the energy stored in the food to
serve their own growth and development and all the activities that
constitute being alive. Hence, the energy absorbed from the sun is
circulated a long way round all the organisms in the biosphere, with
fractions of the total being lost as heat on the way till finally it
becomes spent, or reaches the ground state. The energy cycle is
accompanied by the parallel cycling of chemicals. Both cycles branch and
anastomose in a very complicated way as ecologists who study foodwebs or
nitrogen and carbon cycles are well-aware. But it leaves us in no doubt
that all life is a dynamic unity, it is the consequence of sunlight
streaming through an open system, to maintain it far away from
Albert Szent-Gyorgi (1960), a founding father of modern biochemistry,
had a nice way of putting it: that life is an interposition between two
energy levels of an electron: the ground state and the excited state, and
furthermore, as it is the electron that goes round the circuit, life is
really a little electric current going round and connecting up all nature
with the sun and the earth. This fundamental unity of physics and biology
has indeed inspired a lot of people who felt that here was the key to
unlocking the mystery of the living state. But as Szent-Gyorgi remarked
then, and it is still largely the case now, biochemistry and molecular
biology do not address such questions. They tell us a great deal about
what the molecules that make up living organisms are, but very little
about how they are supposed to act. How the energy plucked originally from
the sun is translated so very efficiently into various forms of work -
chemical, mechanical, electrical and osmotic - and in organizing matter
into the splendid diversity of organisms in the biosphere. Szent-Gyorgi
suggested that we can only begin to understand these characteristics of
living systems if we take into account the collective properties of the
molecular aggregates in terms of solid state physics. There, we would find
a clue to the mystery of life.
We know, for example, that although at ordinary temperatures, the
molecules in most physical matter have a high degree of uncoordinated, or
random motion. The situation can change when the temperature is lowered to
beyond a critical level. At that point, all the molecules so to speak,
condense into a collective state, and exhibit the unusual properties of
superfluidity and superconductivity. In other words, all the molecules of
the system move as one, and conduct electricity with zero resistance (by a
coordinated arrangement of all the electrons). Liquid helium at a
temperature close to absolute zero is the first and only superfluid
substance known. And various pure metals and alloys superconduct at liquid
helium temperatures. Recently, technology has progressed to materials
which can superconduct at much higher temperatures above absolute zero.
The solid-state physicist Herbert Frohlich (1968) in Liverpool was among
the first to point out that something like a condensation into a
collective mode of activity may be occurring in living systems, such that
living organisms are in effect, superconductors working at physiological
temperatures. He suggested that much of the metabolic energy, instead of
being lost as heat, is actually stored in the form of coherent
electromechanical vibrations in the body. He called these collective
modes, coherent excitations.
Coherence refers to highly correlated activities in both space and time.
In physics, it is usually understood as the ability of electromagnetic
waves to interfere. For instance, in a version of Young's pioneering
experiment (Fig. 1), two narrow slits and are illuminated by light from a
light source. The light beams, on passing through the slits, fall on the
screen and form an interference pattern of differing brightness in
accordance to where the oscillations in the two light beams are in phase
or out of phase. The ability to form interference patterns depends on the
stability of the oscillations in the two light beams, or more specifically
their phase relationships. This phase stability is referred to as
coherence; the more coherent the light, the sharper the interference
pattern. The coherent state is fluctuationless and has the further
characteristic that it is factorizable (Glauber, 1969). This means
that the parts paradoxically behave statistically independently of one
another while maintaining a coherent pattern as a whole. In other words,
coherence does not imply uniformity, or that every individual part or
molecule of the system is necessarily doing the same thing all the time.
An intuitive way to think about it is in terms of a grand symphony, or a
grand ballet; or better yet, a jazz band in which individuals are doing
different things and are yet in tune or in step with the whole. It is a
state of cooperativity in which the individuals cooperate simply by doing
their own thing and expressing themselves.
What are the consequences of coherence? It results in properties that
are characteristic of biological systems. These include the high
efficiency of energy transfer and transformation which often approaches
100%; the ability of communication at all levels within cells, between
cells and between organisms capable of resonating to the same frequencies;
the possibility for sensitive, multiple recognition systems utilizing
coherent electromagnetic signals of different specific frequencies, such
as for example, the organization of metabolic activities within the cell,
the operation of the immune network and a host of other biological
functions involving specific recognition between hormones or ligands and
their receptors; and finally, the stable persistence of the working system
arising from the inherent stability of coherent states. A more detailed
description of coherence is given in Ho (1993a).
2. Biophotons and coherence in living systems
Evidence for the existence of coherent excitations in biological systems
came from the study of biophotons (see Popp et al, 1981; Popp,
1986). Practically all organisms emit light at a steady rate from a few
photons per cell per day to several photons per organism per second. An
increasing number of observations within the past 15 years from different
laboratories all over the world suggest that biophotons are emitted from a
coherent photon field within the living systems. Organisms are thus
emitters and most probably, also receivers of coherent electromagnetic
signals which may be essential for their functioning (see next Section).
The nature of the light emitted from living organisms is best studied
after a brief exposure to weak illumination. It has been found, without
exception that the the re-emitted light from living tissues follows, not
an exponential decay curve as characteristic of non-coherent light, but a
hyperbolic decay function which is exhibited only by coherent light (see
Fig. 1). This unusual behaviour can be intuitively understood as follows.
In a system consisting of non-interacting molecules emitting at random,
the energy of the emitted photons are lost completely to the outside or
converted into heat, which is the ultimate non-coherent energy. If the
molecules are emitting coherently, however, the energy of the emitted
photons are not completely lost to the outside. Instead, part of it is
coherently reabsorbed by the system. The consequence is that the decay is
very much delayed, and follows characteristically a hyperbolic curve with
a long tail. This result can be derived rigorously from both classical and
quantum mechanical considerations (Popp, 1986). A coherent system
stabilizes its frequencies during decay whereas a noncoherent system
always suffers a shift in frequencies. That, and the capability to
reabsorb emitted energy account for the stability of coherent states.
3. The characteristics of biophotons
Where do biophotons really come from? We know that all sorts of excited
molecules can emit light when they relax back to the ground state, the
frequency of the emitted light being specific for each kind of molecules.
When the spectrum of biophotons is examined, however, it was found that
the light is always in a broad band of frequencies from the infra-red to
the ultraviolet, with approximately equal numbers of photons distributed
throughout the range. This is very different from the Boltzmann
distribution which characterizes a system at thermodynamic equilibrium at
the physiological temperature of the biological system, thus indicating
that the latter is far, far away from thermodynamic equilibrium (see Fig.
2). Not only is there an excess of photons at the high energy (short
wave-length) end of the spectrum, but the distribution is very nearly
flat. In other words, it does not depend on the wavelength: f(l)
= const. This means that the light is emitted from all kinds of molecules
all over the cell. The photons are stored in a delocalized manner within
the system, and all the frequencies are coupled together to give, in
effect, a single degree of freedom.
Evidence for the delocalization of coupled photons come from the
observation that the emitted light retains its broad spectral distribution
when organisms are stimulated with monochromatic light or light of limited
spectral compostion. Moreover, the hyperbolic decay kinetics has the same
form over the entire spectrum of emitted light (see Popp, 1986; Musumeci
et al, 1992).
The Boltzmann distribution characteristic of a system at thermodynamic
equilibrium arises from the maximization of entropy (molecular disorder,
or degrees of freedom) under the constraint of a fixed energy in a closed
system. As biological systems are open instead of closed, the constraint
of a fixed energy does not apply. This does not mean that energy
conservation is violated, as biological system + surroundings are still
subject to energy conservation. Nor does it mean that there is always an
overflow of energy within the system. It only means that there is always
enough energy available for the system. Living systems store
energy (or photons) over the whole range of space and time scales - from
10-10m to metres or more, and 10-9s
to days or longer time intervals - in a readily mobilizable form. They do
not suffer from energy shortage on account of their high storage capacity
within the intricate space-time organization (see Ho, 1993a,b for
The f(l) = const.
distribution can also be seen as the consequence of the maximization of
entropy when the constraint of fixed energy is removed in an open system
far from equilibrium. The f(l)=
const. profile looks somewhat like the expression of "white noise"
within the system, but this is far from the case. As this distribution
represents the highest possible entropy in a system far from equilibrium,
fluctuations cannot be interpreted in terms of noise - in contrast to a
system at thermal equilibrium. Rather, they are "signals"
generated within the system. In other words, by maximizing entropy
according to f(l) = const.,
the signal/noise ratio of the biological system is optimized over all
wavelengths (Popp, 1989). On the other hand, as the frequencies are all
coupled together, the absolute value of entropy representing the maximum
can also become arbitrarily small, theoretically even zero.
In summary, the fact that there is always enough energy available in the
biological system confers on it the following properties:
Optimal signal/noise ratio for communication,
Existence at a phase threshold between a chaotic (S - , N
- ) and a coherent (S - 0, N - 1) regime, where S
is the entropy, and N is the number of degrees of freedom,
The possibility to extend energy storage, or the f(l)
= const. distribution to longer and longer wavelengths in the
course of evolution, and hence to expand the range of communication from
distances between molecular within the cell all the way to distances
between individuals in a population.
4. Long range communication
The hypothesis that the f(l)
= const. distribution of biophotons can extend into infinitely long
wavelengths is admittedly an extrapolation from measurements within and
near the visible range. However, it can explain a variety of phenomena
such as cancer development or group formation in organisms.
We are postulating the existence of very weak, long-range (long
wave-length) interactions between living systems. These weak long-range
emissions cannot be detected directly with the instrumentation now
available. However, this is not a sufficient reason for excluding them
from consideration, as there are methods of obtaining indirect evidence of
their existence, as we shall describe below.
a. Normal and cancer cells in culture
A first experiment of this kind was performed by Schamhart and van Wijk
(1987). They exposed suspensions of cultivated rat liver and rat hepatoma
cell lines H35 and HTC for some seconds to white-light from a 150W
tungsten lamp and registered the re-emitted light afterwards. The decay
curves are, as usual, hyperbolic rather than exponential. On altering the
number of cells in the suspension, the found that normal cells exhibit
decreasing light re-emission with increasing cell density, whereas tumour
cells show a highly nonlinear increase with increasing cell density (see
Fig. 3). If there were no long-range interactions between the cells, the
intensity of re-emitted photons would increase linearly with increasing
number of cells, corrected by a term for self-absorption within the
population. Neither the nonlinear increase of re-emission intensity from
tumour cells nor the significant decrease of re-emission from
normal cells could be explained unless there are long-range interactions
between the cells, which are furthermore, correlated with their differing
social behaviour, the tendency of tumour cells to disaggregation as
opposed to the tendency of normal cells to aggregate.
These phenomena can be interpreted in terms of Dicke's (1954) theory of
photon-emission from an ensemble of emitters. He showed that photon
emission tends to bifurcate into the two branches of superradiance
and subradiance as soon as the wavelength of the emitted light is
large compared to the distances between the emitters which are also
absorbers. Superradiance is the increase of emission intensity
concomittant with a shortening of the relaxation time. The opposite branch
describes the regime of subradiance where emission intensity decreases
with a more and more prolonged decay time, corresponding to photon storage
within the system.
In terms of Dicke's theory, normal cells have a greater capacity for
subradiance the closer they are together, while the malignancy of tumour
cells is associated with the opposite behaviour, that is, the loss of
subradiance. This suggests that long-range interaction is based on the
coherence of the subradiance regime, with the coherence volume extending
over the entire cell population. By changing the degree of coherence the
cells can control and regulate their social activities. According to this
model, tumour cells, unlike normal cells, seem unable to communicate. This
may account for the repulsive forces that are responsible for metastasis
in the malignant cells as opposed to the attractive forces responsible for
population formation in normal hepatocytes (for further details see Nagl
and Popp, 1987).
b. Populations of Daphnia
Even more clear-cut results are obtained in organisms, such as Daphnia;
where self-emission is measured instead of stimulated re-emission. Figure
4 depicts the results of measurements made by Galle et al (1991).
Instead of the expected linear increase in photon intensity with
increasing number of individuals, a pattern of maxima and minima is
observed, where the maximum and minimum values of photon intensity can be
reproducibly assigned to definite numbers of individuals in the cuvette.
It turns out that they invariably correspond to integer ratios of the
average distances between individual animals to their body size. The
results cannot be interpreted in terms of ordinary biochemistry. Instead,
by treating the daphnia as a population of antennae interacting by means
of resonance wavelengths related to their geometrical dimensions, a good
fit to the experimental data is obtained. Regardless of whether the
details of the hypothesis are correct, the experiments clearly demonstrate
the existence of long-range interactions between individuals in a
population. These interactions may be the basis for swarming and the
regulation of growth and other collective functions. The link to body size
indicates communication wavelengths in the microwave to millimeter range.
c. Superdelayed luminescence in Drosophila
We have recently discovered the remarkable phenomenon of superdelayed
luminescence in synchronously developing populations of early Drosophila
embryos, in which intense, often prolonged and multiple flashes of light
are re-emitted with delay times of one minute to eight hours after a
single brief light exposure. Some examples are presented in Figure 5 (see
Ho et al, 1992). The phenomenon depends on the existence of
synchrony in the population, and furthermore, the timing of light exposure
must fall within the first 40 minutes of development. However, the
occurrence of the flashes themselves do not obviously correlate with
specific embryonic events. They give information concerning the physical
state of the embryos at the time of light stimulation - such as the
existnece of a high degree of coherence - rather than at the time during
which the flashes themselves occur. Superdelayed luminescence bears some
formal resemblance to the phenomenon of superradiance described above in
which cooperative interactions among embryos within the entire population
lead to most, if not all the embryos emitting light simultaneously. This
implies that each embryo has a certain probability of re-emitting after
light stimulation, so that it can either trigger re-emission in other
individuals, or alternatively, its re-emission could be suppressed by
them. Only whe the population is re-emitting at the same time is the
intensity sufficient to be registered as the intense flashes that is
detected by the photon-counting device. On the other hand, re-emission in
the entire population could also be suppressed (i.e., in the subradiant
mode), such that in approximately 30 to 40% of the cases, there is no
clear indication of any superdelayed re-emission.
We do not know if any functional
significance could be attached to superdelayed luminescence. Drosophila
females typically lay eggs just before sunrise, so the external light
source could be used as an initial synchronizaing signal or Zeitgeber,
which maintains the circadian and other biological rhythms. The
superdelayed re-emission could then be a means of maintaining
communication and synchrony among individuals in the population. On the
other hand, the flashes may simply be the embryos' way to inform us of
their globally coherent state at the time when light stimulation is
applied, enabling the embryos to interact nonlinearly to generate light
emission that is coherent over the entire population, and orders of
magnitude more intense than the spontaneous emission background (see Ho
et al, 1992; and Ho, 1993a for further details).
5. Coherence and the evolution of consciousness
What does the study of coherence contribute to our understanding of the
unity of life? To return to our overview on the cycle of life, we can see
that sunlight is the most fundamental source of energy, which is supplied
at the high frequency end, and biological systems as a whole display the
natural tendency to delay the decay of this high level energy for as long
as possible. This is why the earth's natural biosphere is not a
monoculture, indeed, it is the very diversity of life that is responsible
for delaying the dissipation of the sun's energy for as long as possible
by feeding it into ever longer chains and webs and multiple parallel
cycles in the course of evolution. But that is not the entire story, for
the the most effective way of hanging on to this energy for as long as
possible is by the formation of a coherent platform of oscillations which
expands the photon field into a coherent state of growing bandwidth. This
is the f(l) = const.
distribution which allows the sun's energy to spill over into longer and
longer wavelengths. This may be why organisms have such different
life-spans; the trend in evolution is towards the emergence of organisms
with longer and longer life-spans and finally in the case of social
organisms and human beings, we see the emergence of social traditions that
span many generations. The link with social tradition is the clue to the
meaning of this energy flow through a coherent field of ever increasing
bandwidth. For it is at the same time a flow and a creation of
information. Electromagnetic signals of different frequencies are involved
in communication within and between organisms, and between organisms and
the environment. The coherent platform is a prerequisite for universal
Thus, it seems that the essence of the living state is to build up and
extend the coherent spatio-temporal platform for communication starting
from the energy of the sun initially absorbed by green plants. Living
systems are thus neither the subjects alone, nor objects isolated, but
both subjects and objects in a mutually communicating universe of meaning.
In contrast to the neo-Darwinist point of view, their capacity for
evolution depends, not on rivalry or on might in the struggle for
existence. Rather, it depends on their capacity for communication. So in a
sense, it is not individuals as such which are developing but living
systems interlinked into a coherent whole. Just as the cells in an
organism take on different tasks for the whole, different populations
enfold information not only for themselves, but for all other organisms,
expanding the consciousness of the whole, while at the same time becoming
more and more aware of this collective consciousness. Human consciousness
may have its most significant role in the development and creative
expression of the collective consciousness of nature.
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Fig. 1. Hyperbolic decay of re-emitted photons from a synchronously
developing population of Drosophila embryos. (From Ho, 1993a).
Fig. 2. Spectral distribution of biophoton emission compared to the
Boltzmann distribution of a system at thermal equilibrium at physiological
Fig. 3. Total photon counts within the first seconds after exposure of
cell suspensions to white light. Malignant HTC cells, -o-o-; normal
heptocytes, -o-o-; and H35 cells which are only weakly malignant, -x-x-.
Fig. 4. Self-emitted photon count-rate in daphnia as a function of
Fig. 5. Superdelayed luminescence in Drosophila. Continuous
recordings of light emission from synchronously developing baches of
embryos. Each data point on the graphs represents the aggregated photon
count for 20s. Top trace, control batch not exposed to light. The other
traces are from batches which have all been exposed to white light for one
minute before the recording, and show different forms of superdelayed
luminescence. Traces on the right are expanded versions of those on the
left. (From Ho et al, 1992).