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“Hubble’s colourful view of the Universe” by Hubble Space Telescope / ESA is licensed with CC BY 2.0. To view a copy of this license, visit

The universe encompasses an enormous amount of phenomena and events. Some of them have been discovered and successfully described in the past, while some other remain unknown, waiting there to be unveiled.

Among all those occurrences, we can distinguish some rules that the universe seems to obey “no matter what”. These are called laws, and as their name suggests, they are always fulfilled.

It does not matter what is the instance under study, the laws of the universe are always satisfied. These laws then separate the occurrences that can happen in our reality, from other that are inconceivable.

For example, it is not possible for an object in rest to spontaneously start moving on a random direction, without any force that prompts such motion. Or we cannot find, nowhere in the universe, liquid water with moderate pressure conditions at temperatures higher than 100°C.

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“Kick off” by abfall is licensed with CC BY-NC-SA 3.0. To view a copy of this license, visit

The implications of these laws, rather than involving killjoy limitations, are that they shape the universe in its current form. They endow our reality with a well-defined basis to exhibit ordered patterns. Without such laws, the universe would not only be “funny” as a cartoon, but it could be potentially unstable, as to prevent the formation of planets and galaxies, and by all means life.

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“Fantasy-Land” by lundrah.sawson is licensed with CC BY-NC-SA 2.0. To view a copy of this license, visit

To account for this, we can say that among the many laws that we could discuss, there is one in particular that can be the simplest one and also the foundational basis for many other. Namely, the first law of thermodynamics. This law is about conservation of matter and energy. Basically, they cannot be created or destroyed, they can only change their form.

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“Energy concept map” by coach_robbo is licensed with CC BY-NC-SA 2.0. To view a copy of this license, visit

For example, in real-life if you buy a portable battery at the airport, the amount of energy that you will be able to transfer to your phone is bounded by the amount of stored energy available in the portable battery. Moreover, that energy had to be stored there before, by previously charging the portable battery from electricity that was supplied by a utility.

The utility itself also had to get the energy from a generator whose spinning is induced, most of the times, by the work produced by burning a fossil fuel, which was also “charged” through actually millions of years, by concentration of organic material.

This sounds rather like common sense. If we want something we have to pay for it, including all the people involved in the whole supply chain. From the workers in charge to extract the fossil fuel, to the guy that sold the portable battery at the store.

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“Oil Drilling Platform” by chumlee10 is licensed with CC BY-SA 2.0. To view a copy of this license, visit

There could be an open debate and even controversy about many aspects of physics, but there is no question about the validity of the first law of thermodynamics. Is so fundamental, that failing to satisfy this law, at least one time, would overthrow all the understanding that we have about the universe where we live.

For instance, in the past example of the portable battery, imagine that miraculously there was some “extra energy” that spontaneously appeared. Who paid for that? That would not be only the end of a well-established energy market, but would be also dangerous.

If energy was not a conserved quantity and can be spontaneously created:

— What would prevent objects with kinetic energy to suddenly start moving faster? This includes a tree leave that increases its weight, in the form of the force with which it hits the ground, or the head of an unfortunate pedestrian.

— What would prevent our planet to start moving faster, abruptly pushing everything on earth including us, into an involuntary motion due to the acceleration.

— What would prevent the sound of ants walking near us, to be suddenly amplified as to damage our eardrums?.

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“Fantasy Faire 2010” by Daniel Voyager is licensed with CC BY 2.0. To view a copy of this license, visit

The latter are events derived from a sudden creation of energy, but sudden destruction is equally catastrophic. For example, what happened if the energy stored in our cells suddenly disappeared, spoiler alert: we die. What happened if the heat irradiated by the sun sometimes vanished on its way to earth?, a catastrophe.

At this point we can possibly agree that the first law of thermodynamics is necessary to keep an adequate equilibrium on the universe. Energy can pass through different processes and transformations, but it always remains constant. This is due to the fact that applying energy to a process has only to possible outcomes: 1) it generates work, or 2) it produces heat.

Applying energy will end up producing work which has to do with the change of energy with time (“-dynamics”). Or it will produce energy dissipation as heat (“Thermo-”).

Energy supply rate can be measured in terms of the power delivered to perform a physical process.

Work is the rate of change of energy with respect to time, it has to do with dynamics such as motion and transfer of energy.

Heat is produced in the form of dissipation, that is released from the process to the environment.

The above is probably the most accurate way to describe the first law of thermodynamics, since it permits to avoid confusion, especially in those cases that seem paradoxical.

For example, imagine that you connect a refrigerator inside an hermetic room, which prevents exchange of heat with the outside world. Then you leave the refrigerator door open.

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“The almost-empty-fridge blues” by clhendricksbc is licensed with CC BY 2.0. To view a copy of this license, visit

What would happen with the room temperature? will it get hot or cold?

The surprising answer is that it will get hot. The reason is that the energy supplied to the refrigerator (in this case by electricity) must find a possible outcome as work and/or heat. But work cannot take place since there is no transfer of heat to the outside world and then there is no exchange of energy changing with time. Consequently, the only possible outcome is that the energy supplied is transformed into heat dissipation.

Moreover, unlike many other processes in physics, the process of heat dissipation is irreversible, but that matter has to do with another law that deserves more space for elaboration, i.e. the second law of thermodynamics.

Jonathan C. Mayo-Maldonado

Written by

Mexican scientist, engineer and educator. PhD, MEng and BSc in Electrical and Electronic Engineering.

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