How Old is Universe?

The Universe is about 13.7 billion years old. At its beginning it looked nothing like it does today. Yet, everything in today’s Universe did exist in some form back then. It all started with the Big Bang, a kind of explosion that would not only go on to produce all the matter in the Universe but also marked the start of time.


The term “Big Bang” was coined by Fred Hoyle in 1950 to illustrate to his radio listeners the difference between it and his own theory, “Steady State”, where the Universe has no beginning.

Everything in the Universe produces energy – you produce energy when you exercise, and light energy is produced by nuclear reactions inside stars,

FAST FACTS: Creation of the Universe

  1. At the start, Universe was a hot and dense ball of radiation energy.
  2. In one-thousandth of a second, tiny radiation particles produced tiny particles of matter. These combined to form the first ever chemical elements, hydrogen and helium.
  3. Some regions of the young Universe contained slightly more hydrogen and helium than others. These shrank to form the first stars.
  4. Nuclear reactions inside the stars produced many other chemical elements, including carbon and oxygen.
  5. The elements in the Universe today were produced from elements created in the Big Bang.

Elements in the Sun

elements of the Sun
The Sun. Photo: NASA / SDO / Seán Doran

The top ten chemical elements that make up the Sun are:


Hot stuff!


In the first trillionth of a second of its creation, the temperature of the universe was ten billion trillion trillion degree celsius.

Looking back

  • We see objects in space because of their light. Stars produce their own but others, such as the Moon and planets, shine by reflecting light.
  • Light travels at 299,800 km per second (186,287 miles per second) – faster than anything else.
  • Distant stars are seen as they were in the past – when the light left them.
  • The most distant galaxies we see are about 13 billion light years away, and as they were in the early Universe.

Blasts from the past

Belgian Georges Lemaitre suggests that all material in the Universe started as a single condensed sphere that exploded.

Russian-born physicist George Gamow explains the first elements formed in the explosion.

Englishman Fred Hoyle shows how heavier elements are produced by massive stars.

American physicists Arno Penzias and Robert Wilson discover cosmic microwave background radiation, the leftover radiation initially produced by the Big Bang.

American Alan Guth modifies the Big bang theory by introducing the idea of inflation – a short period of extra expansion within a split second of the start of the Universe.

The Universe is expanding by about
70 km (43 miles) every second.

Human origins

5 bullion years ago
The Sun formed from hydrogen and helium and small amounts of other elements.

4.5 billion years ago
Some of the material not used up in the Sun joined together to form Earth.

About 3.7 billion years ago
Carbon-containing molecules in young Earths oceans evolved into bacteria-like cells; the first forms of primitive life.

1 million years ago
The first humans walked on Earth.

Near, far… and really far

Depending on how far away objects are, distances in the Universe are calculated using a variety of measuring units.

  • Kilometres or miles
    Useful for measuring the distance of relatively near objects in our Solar System, such as the planets, moons, and asteroids.
  • Astronomical units
    Used for measuring planetary distances within the Solar System. The distance from the Sun to Earth equals one astronomical unit (AU).
  • Light years
    This measurement is useful for distances within our galaxy, the Milky Way, and across the Universe. One light year is the distance light travels in one year – equal to 9.46 million million km (5.88 million million miles).

What about you?

All the elements on Earth, including all the elements in your body, were produced in stars.

Bigger and bigger


planet earth
Planet Earth

Earth may feel big to us, but at 12,756 km (7,926 miles) across, it is just a speck in an expanding Universe.


The Sun
The Sun

Planets orbit stars- our star is the Sun. Without it there would be no life. It measures 1.4 million km (870,000) across.



Stars exist in galaxies, colossal star systems that come in a range of sizes and shapes. Earth is in the Milky Way Galaxy.


star clusters
Clusters. Credit: NASA

Galaxies exists in clusters – the Milky Way Galaxy is in the Local Group cluster, stretching 10 million light years across.


Supercluster. Image: AKVO

Galaxy clusters are within superclusters – we are in the Virgo Supercluster, 200 million light years from one side to the other.


The largest structures in the Universe are chains o superclusters that are separated by huge empty voids.

The Universe is everything we can see, and a lot we can’t see. It was created in the Big Bang explosion and has been changing and expanding ever since.