When was the beginning of time?
The beginning of time and the creation of the universe has been a topic of much debate and speculation throughout human history. Different cultures and religions have various beliefs about when and how the world began. From a scientific perspective, the current most widely accepted theory is that the universe started with the Big Bang about 13.8 billion years ago.
The Big Bang theory proposes that space and time began at a single point which rapidly expanded to create the matter and energy that make up everything we see today. Evidence for the Big Bang comes from observations of the expansion of the universe, the cosmic microwave background radiation, and the relative abundances of light elements like hydrogen and helium.
While the Big Bang is the prevailing cosmological model for the origin of the universe, other theories have been proposed as well including steady state and cyclical models. The study of the birth of the universe continues to be an active area of research in physics and astronomy.
Major origin of the world theories
There are several major scientific and religious theories that have been proposed throughout history to explain the origin of the world:
Big Bang Theory
As mentioned above, the prevailing scientific consensus is that the universe began approximately 13.8 billion years ago with the Big Bang. All matter and energy in the universe emerged from an infinitely dense point called a singularity which rapidly expanded. Strong evidence for the Big Bang includes:
- Observation of galaxies moving away from each other shows the universe is still expanding.
- Detection of cosmic microwave background radiation which is remnants of the heat from the initial expansion.
- Abundances of lighter elements like hydrogen, helium, and lithium match predictions from Big Bang nucleosynthesis.
Steady State Theory
The steady state theory proposes that the universe has always existed in a static state, with no beginning or end. It suggests that as the universe expands, new matter is continuously created to fill the gaps. This theory avoids the need for an absolute beginning. However, evidence for the Big Bang and the observation that galaxies were closer together in the past contradicts the steady state model.
Cyclic Models
Cyclic or oscillating universe models suggest that the universe goes through cycles of expansion and contraction. Rather than a single Big Bang, there could be multiple expanding and contracting phases. While current evidence points towards a single Big Bang, cyclic models that include phases of dark energy or multiple “bangs” have been proposed as alternatives.
Religious Creation Myths
Religious texts and mythologies from around the world offer origin stories that date the creation of the Earth and universe to timescales of thousands to millions of years ago. Some prominent examples include:
- Christianity and Judaism – The Book of Genesis dates the creation of the world to about 6000 years ago.
- Hinduism – Hindu texts propose the universe goes through repeated cycles of creation and destruction over billions of years.
- Chinese Mythology – The Pangu myth dates the creation of the world to the separation of yin and yang.
While these creation myths share some parallels with scientific theories, most are not compatible with empirical evidence of the age and origins of the universe. They offer insight into cultural and spiritual belief systems rather than testable cosmological models.
When did time begin?
The beginning of time is directly linked to our understanding of the origins of the universe. According to the Big Bang theory, time itself began alongside the beginning of space at the instant of the Big Bang. Prior to the expansion of this singularity, the concepts of time and space as we understand them did not exist.
Going by our current physics models, we cannot extrapolate all the way back to a definitive “beginning” of time. However, we can trace the history of the universe back to one Planck time (5.39 × 10-44 seconds) after the Big Bang. In this earliest moment, the universe underwent extremely rapid exponential expansion called cosmic inflation. Our notion of time emerges from the measurement of change, so this marks the point where change first occurred.
Key points about the beginning of time:
- Time and space are intrinsically linked and emerged together at the Big Bang.
- We cannot definitively say time has a single discrete beginning.
- As far as we can extrapolate based on known physics, time extends back to one Planck time after the Big Bang.
- Before cosmic inflation, the universe was in a quantum gravitational state we do not understand.
- The Big Bang marks the point where change first occurred and time becomes measurable.
The closer we get to the Big Bang singularity, the less applicable our classical understanding of space and time becomes. A complete theory of quantum gravity would be needed to describe the universe before one Planck time.
When did the Earth form?
The Earth formed over 4.5 billion years ago, condensing from a cloud of dust and gases around the young Sun. The leading scientific model for the formation and evolution of the solar system and Earth is called the nebular hypothesis. This outlines how the solar system coalesced from a large rotating disk of interstellar gas and dust called the solar nebula.
Key milestones in the formation of Earth based on radiometric dating of meteorites and lunar samples:
4.6-4.5 billion years ago
- Gravity caused the solar nebula to condense and form the Sun at the center.
- Planets accreted as matter collided and merged into larger bodies orbiting the Sun.
- Heavier metals like iron sank forming the core while silicate rocks formed the mantle.
- The primordial Earth was bombarded by other space debris, a period called the Late Heavy Bombardment.
4.4-4.2 billion years ago
- The first oceans formed as water vapor in the atmosphere condensed into liquid water.
- Earth’s landmasses continued to take shape through volcanic eruptions and tectonic activity.
- The atmosphere transitioned from hydrogen-helium to gases like methane, ammonia, carbon dioxide, and nitrogen.
4.0-3.8 billion years ago
- The earliest evidence of possible microbial life on Earth.
- Bombardment by comets and asteroids brought water and organic compounds.
- First continental crust formed.
From this point onward, life played an increasingly important role shaping Earth’s atmosphere and environment. While exact dates have ranges of uncertainty, this covers the major stages of Earth’s formation derived from radiometric dating of the oldest known terrestrial and lunar rocks.
How old is planet Earth compared to the universe?
The age of the Earth is approximately 4.54 billion years. By comparison, the current scientific consensus is that the age of the observable universe is around 13.77 billion years. This means that the Earth formed about 9.23 billion years after the Big Bang and the beginning of the universe as we know it.
To put the age of the Earth in context of the whole universe:
- Age of the universe: 13.77 billion years
- Age of the Earth: 4.54 billion years
- Percent of universe’s history before Earth formed: ~67%
- Age difference: Earth formed about 9.23 billion years after the Big Bang
Some key points when comparing the age of the Earth versus the age of the universe:
- The Earth is relatively young compared to the total age of the observable universe.
- The first generation of stars and galaxies formed a few hundred million years after the Big Bang, before the solar system and Earth.
- The matter that makes up the Earth originated from dying stars that formed earlier in the universe’s history.
While around 4.5 billion years represents a huge amount of time from a human perspective, it is quite brief in cosmological terms. The formation of planet Earth was only possible because of the billions of years of cosmic evolution that preceded it.
Conclusion
Determining the precise age of the Earth and cosmos remains an active research area in astronomy and physics. However, empirical evidence strongly points towards an Earth that formed 4.5 billion years ago, approximately 9 billion years after the beginning of the universe according to the Big Bang model. Refinements in the age dates continue as dating techniques improve. Theories on the ultimate origin of time and the cosmos prior to the Big Bang singularity remain speculative. Moving forward, continued study of the evolution of the universe and planets will shed more light on the timescales and steps involved in the formation of our world.
