1. Arrow of time determined by
life´s easiest direction for
computation
Entropy, Time and life
(Alberto G.Corona agocoronaDELETE@gmail.DELETEcom)
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2. Life is computation
• Living beings maintain homoeostasis by making predictions
about the environment so that they anticipate. So they must
compute.
• Computation is not only at the brain, but also at te chemical
level. Plants and bacteria also compute. chains of chemical
reactions are analogous to algorithms in a computer
language. its purpose is to produce an ouput that is good
for the organism, given an input.
• To open the mouth in the precise moment that the small fish
pass nearby, the big fish has to calculate in advance the
small fish trajectory.
• Even a seed has to compute the right moment for
germination given temperature, humidity etc.

3. What I want to demonstrate
• The increase of entropy is a precondition for life
• Therefore, the low entropy of the universe at the
beginning is a consequence of the anthropic principle
(and the concept of "begining" too)
• For computational restrictions, evolution and life
operates in the direction of systems that go from lower
to higuer probabilities
• Causality and time itself is a psichological experiece, a
product of the way life can predict to survive.
• Reichenbach “direction of time”: time proceed in the
direction of positive gradients of entrophy
• Time is just a perception product of the computations
living beings have to do to survive and specially,
conscientious beings that learn from experience.

4. Mathematical Multiverse Hypotesis
(MMH)
Reality is mathematical
Hilbert: mathematics means "absence of contradictions"
Progressive unification of phisical laws suggest that our
universe appears to be isomorphic with a single mathematical
structure.
Tegmark: each mathematical structure creates its own universe
http://space.mit.edu/home/tegmark/toe.html
To avoid paradoxes, Gödel incompleteness, non computability
a subset with good properties are the decidable, computable
structures
(tegmark The Mathematical Universe http://tinyurl.com/6zvv5h)

5. Life as criteria for universe existence
• According with MMH, existence of self aware structures
(SAS) is the requirement for an observable universe.
• An alternative criteria for existence may be the existence of
life, understood as self preserving structures (so they must
compute) without mathematical restrictions a priori
• Life then is not a criteria for observability but for existence.
• But life and natural selection demands a mathematical
universe somehow
• Existence of Intelligent life (self aware structures) remains
as the criteria for observability.
• This is not a topic of this presentation.
• A mathematical universe hypothesis is accepted as starting
point.

6. Causation
• According with general relativity, time is local, there is
no absolute notion of simultaneity, it depends on the
observer.
• All natural laws (KUN) are reversible, this do not match
with experience.
• Natural laws do not distinguish forward or backwards in
time
• Therefore, causation is also an illusion caused by the
arrow in which life and natural selection flow due to
computational restrictions (forward)

7. What "life computes" means in the static mathematical
figure of an spatio-temporal, immutable universe?
• Computations need computers and data. They need energy and
building materials and sensors. Living beings have to transport
them.
• To permit life, an Universe must facilitate smooth physical laws and
a direction in which predictions are feasible with a small set of
inputs and computational load. This direction is locally perceived as
arrow of time.
• Seeing from outside, living beings and his environment form
intermingled trajectories in the space-time that maintain low entropy
along their paths thanks to apropriate interactions of his
constituent particles and the environment.
• For the time-aware living being these internal collisions are the
computations that permits life and, if intelligent, interpret past
interactions with the external world as causalities, anticipations,
and sucessful actions for survival,

8. Causation and effects. forward and backward
examples
• Forward (in the arrow of time): Heat is applied to water, water
evaporates.
o Molecular collisions and photons excitate vibration in water
molecules, that evaporate.
• Backward (in reverse arrow of time): very unlikely and fortunate
molecular collisiona makes water molecules to increase its
speed in the down direction (while air molecules decrease its
own). Very unlikely, their directions make them to join and very
unlikely further collisions make then go down to the liquid
water of the recipient

9. Causation. forward and backward examples 2
electric light bulb
• Forward:
o electrons trough a resistence in the light bulb produces
infrared and visible photons that escape outside
• Backwards
o Very unlikely, reflected photons are focused in the light
bulb. The electrons of the philament absorb the photons
and its speed increases. Very unlikely their directions are
aligned so that their movement produce electricity back

10. Causation. forward and backward examples 2
backward ninja jumps
• Forward (entropy increase):
o A ninja fall from a building
o The legs muscles tighten to mitigate the impact, in
the process, heat radiation that is absorbed by
surrounding air molecules
• Backward (entropy decrease):
o Very unlikely the surrounding air molecules emit
infrared photons that impact the muscular fibers in
a way that they add to the energy of muscle
contraction and the ninja jumps back to the top of
the building. Air in the ground is colder now.

11. Entropy in terms of micro and macrostates
• A single macroscopic state (you in your room reading this)
has many microscopic states (the possible combinations of
positions and velocities of all the particles in the room).
• A macrostate has more entropy than other when the number
of possible combinations of microscopic states is greater. A
ninja in the ground after the forward jump and the
surrounding hot air has more entropy than the ninja in the
top of the building, because higer temperature has more
possible combinations of particle speeds.
• If I were living in the reverse arrow of time, to predict that the
ninja in the ground flexing his legs will jump to a three floor
building I have to track the concrete microscopic state of the
ninja, that is the positions and velocities of all the particles in
the legs of the ninja plus the surrounding air molecules
• In the right arrow of time, I can do an educated guess of

12. computational needs for survival in forward and backward arrow of time

13. • Distance in space-time is well defined
• Simultaneity appears when two objects
are in the same space and time
coordinates
• Space-time is four dimensional
• Time is an arbitrary name, it is the
direction of entropy increase
• Particle trayectories must not loop in the
entropic arrow or causality may not be
extracted

14. Causality as a consequence of life's computation
• Emission and absortion of photons, collisions with loss
and gain of energy are individually probable.
• But coordination of many of such phenomena to reduce
entropy are very very unlikely.
• Living beings can anticipate from ordereed to less
ordered states because the correlation of more
disordered states from less disordered states is
computationally easy while the opposite is much
more difficult. This also produces the psychological
sense of causality in conscious beings who learn
from experience.

15. Computation in other arbitrary direction is even more difficult
Weird time
Ordinary time
Collision between
Collision between
A particle in the "past"
Two particles in
With other in the "future"
space
They bounce back to
their time
• In four-dimensional coordinates, when two particles touch in the same
moment of time no matter where time coordinate points to. however the
weird time being see the particle going to and coming back from collision
before seeing the collision. Their computations must be very difficult