# Lesser-Known Concepts Of Physics

We know that Newton’s law, Kepler’s law, Carnot’s theorem, thermodynamics and many other commonly heard laws and concepts had gained recognition since they form the basis of physics. These commonly known concepts are known by everyone who studies science since it is elementary to know for the sake of knowledge and examinations too.

There are some lesser-known concepts which convey important concepts that we should know. In this article, we shall learn and understand two such concepts, Casimir Effect and Hubbles Law.

## Force Between Surfaces In A Vacuum

As we are aware, the force of attraction is seen among the objects on the earth. Do you know the force of attraction exists in a vacuum too? Casimir Effect explains that “The attractive force exists in a vacuum between two surfaces“. This theory was first predicted by Hendrik Casimir, the Dutch Physicist. This theory holds for the molecular forces to cosmology and elementary particles of physics.

Casimir effect is explained as a feeble attractive force that is present between two close parallel uncharged conducting plates. This force is developed due to the quantum fluctuation of the electromagnetic field.

Applications of the Casimir effect are:

• They are used in the nanotechnology sector mainly for silicon integrated technology.
• Casimir effect has contributed to the development of applications regarding the advancement of levitating devices.
• Casimir effect helps to understand the chiral bag model of the nucleon in the best way.
• Now let us understand the Hubbles Law and its formula.

## Law On Velocity Of The Galaxy

Before we know about Hubbles law, let us know what is meant by redshift. Redshift is a phenomenon in which the electromagnetic radiations from an object undergoes an increase in wavelength. Redshift is the fundamental concept to be understood for astronomers.

Blueshift is the opposite phenomenon of redshift. Blueshift is also known as negative redshift where the energy increases due to shorter wavelengths.

Redshift occurs due to:

• The movement of objects either closer or apart from each other in space, i.e. the Doppler effect.
• Strong gravitational forces result in gravitational redshift.
• Cosmological redshift is an expansion of space such that objects are separated without the change in their position.

In the year 1929, Edwin Hubble observed the relation between distance and recession velocity of galaxies and developed the law. Hubbles law is also known as Hubble-Lemaitre law. Hubbles law states that “The velocity of the galaxy which is also known as the redshift is directly proportional to its distance“.

The value of Hubble’s constant was determined by Planck and found it to be equal to 46,200 mph per million light-years.

The law is mainly used for studying the motion of the astronomical objects due to the expansion of the universe. Hubble’s law was first used for understanding the expansion of the universe and is used as the evidence for the big bang model. Hubble’s law is also used for analysing the dark matter and dark energy.

These laws and theories are some of the best contributions to the field of Physics. These concepts help to understand the fundamental molecular topics and also the vast universe and galaxies.