There are two kinds of electronic systems that we
encounter in our daily life – digital and analog. Digital systems are the ones
in which the variables to be dealt with can presume only some specified values
whereas in analog systems, these variables can assume any of the infinite
values. The superiority of digital devices over analog devices has ever been a
topic of discussion. This is the reason why digital devices have taken over
analog in almost all the areas that we encounter today. Digital computers,
digital watches, digital thermometers etc. have replaced analog computers,
analog watches and analog thermometers, and so on. Digital devices have
replaced the analog ones due to their superior performance, better ability to
handle noise and reliability in spite of being more costly than analog ones. Although
most of the devices used today are digital, but in general, the world around us
seems to be analog. All the physical quantities around us; i.e. Light, heat,
current are analog. The so called digital devices have to interface with this
analog real world only. For instance, a digital camera interfaces with analog
signal (light) and converts it into information in the form of pixels that
collectively form a digital image. Similarly, a music system converts the digital
information stored in a music CD into pleasant music which is nothing but
analog sound waves. All the digital devices that we know have this
characteristic in common. Simply speaking, there are devices known as Analog to
Digital converters (ADC) and Digital to Analog converters (DAC) that acts as an
interface between the real analog world and the digital devices and converts
the data sensed by analog sensor into the digital information understood by the
digital system and vice-versa. They all interface with the so called analog
world. But is the analog world really analog? Is it true that analog variables
can take any number of values? Or is there some limit of granularity for them
too. Is this world inherently digital or analog in nature? Is digital more
fundamental than analog?
As we all know, there are many fundamental
quantities in this universe viz. Mass, length, time, charge, light etc. We have
been encountering these ever since the world has begun. Now the question arises
– whether all these quantities are inherently analog or digital? Finding the
answer to this question will automatically bring us to the answer of our main
question; i.e. whether the basics of this world lie in analog or digital. It is
often said that “Heart of digital devices is analog.” (See figure below). This
is because, as visible on a macroscopic scale, the current and voltage
waveforms produced by a digital circuit/system are not digital in fact. This
can be observed from the fact that the transition from one logic state to
another cannot be abrupt. Also, there
are small spikes in the voltage levels even if the system is stable in one
state. But, seen at microscopic level in terms of transfer of current by
transfer of electrons, since, there can only be
transfer of an integral number of electrons,
current can only take one of numerous values, and not just any value. Let us
take an illustration. The charge on an electron is 1.6E19 (or
0.00000000000000000016) represented as ‘e’. It is the smallest charge ever
discovered. It is well known that charge can exist only in the multiples of
‘e’. Thus, electric charge is a digital quantity with the smallest unit ‘e’. When
we say that the value of charge at a point is +1C, we actually mean that the
charge is caused by transfer of 6250000000000000000 electrons. Since, the
smallest unit of charge is 0.00000000000000000016 C, hence, there cannot exist
any charge of value 1.00000000000000000015 C, since that will make the number
of electrons to be a fraction. Since, the magnitude of 1C is very large as
compared to charge on 1e, it appears to us as continuous and not discrete. For
us, there is no difference between 1. 00000000000000000015 and 1 as the devices
we use don’t measure with that much precision. Hence, we infer these quantities
as analog. Similar is the case with other physical quantities.
Many laws have been formed by our great scientists postulating
about the quantization of some basic physical quantities. Viz. Planck’s quantum
theory states that angular momentum of an electron in the orbit of an atom is
quantized. Simply stated, it states that the angular momentum can take only
specified values given as multiples of h/2Π. Thus, the smallest angular
momentum an electron can have is h/2Π and the angular momentum can increment
only in steps of h/2Π. If we take h/2Π as one unit, then we can say that
angular momentum of an electron is a digital quantity. Similarly speaking,
Light is also known to consist of photons. According to Planck’s quantum
theory, the light intensity is also an integral multiple of the intensity of a
single photon. Thus, light is also inherently a digital quantity. Also, as
stated above, the charge is also quantized.
But there are some physical quantities of which
quantization is yet to be established. Mass is one of those quantities. But, it
is believed that the quantization of mass will be established soon.
Thus, we have seen that most of the physical
quantities known are known to be digital at microscopic level. Since, we
encounter these at macroscopic level having billions and billions of basic
units, the increments in these seem to be continuous to us as the smallest
incremental unit is negligible in comparison to actual measure of the quantity
and we perceive them as analog in nature.
Thus, we can come to the conclusion that most of
the quantities in this world are digital by their blood. Once the quantization
of mass will be established, we can conclude with surety that digital lies in
the soul of this world. This digital is similar to our definition of digital
systems; just the difference is that it occurs at a very minute scale which we
cannot perceive at our own.
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