1.the Universe

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In this post we will study about The Universe-Big Bang-Redshift and Blueshift.

Very few questions are asked in prelims [time to benefit ratio is too low] from this section.

You can ignore these concepts if you found them too scientific.

The Universe

Universe ==> all existing matter and space.

Tiniest subatomic particles to galactic super-clusters.

The universe is incomprehensively large in size and dimension.

Made up of 100 billion galaxies, each comprising an average of 100 billion of stars.

Most scientists believe that the universe began about 13.8 billion years ago in what

has become known as the Big Bang.

This gigantic explosion caused matter to expand to form billions of swirling galaxies and

over the time, the stars and their planets.

Big Bang Theory and Expanding Universe

The Big Bang theory is the prevailing cosmological model for the birth of the universe.

It states that at some moment all of space was contained in a single point from which

the Universe has been expanding ever since.

Modern measurements place this moment at approximately 13.8 billion years ago,

which is thus considered the age of the universe

After the initial expansion [inflation], the Universe cooled sufficiently to allow the

formation of subatomic particles, and later simple atoms.

The majority of atoms produced by the Big Bang were hydrogen, along with helium.

Giant clouds of these primordial elements later coalesced through gravity to form stars

and galaxies.

According to this theory, the universe, ever since its birth, is expanding in all directions

uniformly


Exapnding Universe

Big Crunch

Universe would reach a maximum size and then begin to collapse.

It would become denser and hotter again, ending with a state similar to that in which it

started—a Big Crunch.


Time Temperature

in ◦c

Event

10-43 Sec 1032 The cosmos goes through a superfast "inflation,"

expanding from the size of an atom to that of a grapefruit

in a tiny fraction of a second.

10-32 Sec 1027 Post-inflation, the universe is a seething, hot soup of

electrons, quarks and other particles

10-6 Sec 1013 A rapidly cooling cosmos permits quarks to clump into

protons and neutrons.

3 min 108 Still too hot to form into atoms, charged electrons and

protons prevent light from shining: the universe is a

superhot fog


3,00,000

years

10,000 Electrons combine with protons and neutrons to form

atoms, mostly hydrogen and helium. Light can finally

shine.

1 billion

years

-200 Gravity makes hydrogen and helium gas coalesce to form

the giant clouds that will become galaxies: smaller

clumps of gas collapse to for in the first stars

15 billion

years

-270 As galaxies cluster together under gravity, the first stars

die and spell heavy elements into space: those will

eventually turn into new stars and planets

Ans) a

Cosmic microwave background

The cosmic microwave background (CMB) is the thermal radiation left over from the

"Big Bang".

The CMB is a cosmic background radiation that is fundamental to observational

cosmology because it is the oldest light in the Universe and can be found in all

directions.

With a traditional optical telescope, the space between stars and galaxies (the

background) is completely dark. However, a sufficiently sensitive radio telescope shows

a faint background glow, almost exactly the same in all directions, that is not associated

with any star, galaxy, or other object. This glow is strongest in the microwave region of

the radio spectrum.


The CMB is well explained as radiation left over from an early stage in the development

of the Universe, and its discovery is considered a landmark test of the Big Bang model

of the Universe.

What Are Redshift and Blueshift?

Redshift and Blueshift describe how light changes as objects in space (such as stars or

galaxies) move closer or farther away from us. The concept is key to charting the

universe's expansion.

Visible light is a spectrum of colors, which is clear to anyone who has looked at a

rainbow.

When an object moves away from us, the light is shifted to the red end of the

spectrum, as its wavelengths get longer.

If an object moves closer, the light moves to the blue end of the spectrum, as its

wavelengths get shorter.

American astronomer Edwin Hubble (who the Hubble Space Telescope is named after)

was the first to describe the redshift phenomenon and tie it to an expanding universe.

His observations, revealed in 1929, showed that nearly all galaxies he observed are

moving away.


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1.the Universe