Expansion of the Universe

Introduction

• The expansion of the universe is a fundamental concept in cosmology, explaining how the cosmos has evolved over time.
• Recent scientific measurements have revealed that the rate of the universe's expansion is increasing, challenging our understanding of its dynamics.

Variable Expansion

• Contrary to previous assumptions, the expansion of the universe is not constant but variable.
• Recent discoveries indicate that the rate of expansion is accelerating, suggesting the presence of mysterious entities known as dark matter and dark energy.

Dark Matter and Dark Energy

• Dark matter and dark energy are hypothetical components of the universe that cannot be directly observed but are inferred from their effects on cosmic phenomena.
• They play a crucial role in explaining the variable expansion of the universe.

Evidence from Galactic Rotation

• Observations of galaxies, including our Milky Way, provide evidence for the existence of dark matter.
• In a spiral galaxy like the Milky Way, stars and matter rotate around a central point.
• According to gravitational principles, the orbital speed of stars should decrease with distance from the centre, but observations show a relatively constant orbital speed.
• This inconsistency implies the presence of unseen dark matter, which exerts gravitational influence beyond what can be explained by visible matter like stars, gas, and dust.

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Expansion of the Universe

Dark Matter's Role

• Dark matter constitutes a significant portion of the universe's mass, as inferred from its gravitational effects.
• It is believed to be a form of matter with unique properties, including strong negative pressure.

Proportion of Dark Matter

• Observations of galaxy rotation and other phenomena suggest that most of the mass in the universe is composed of dark matter.
• Dark matter's influence on cosmic dynamics is a key factor in understanding the expansion of the universe.

Dark Energy

• Dark energy is another mysterious component of the universe that counteracts gravity's attractive force.
• Unlike gravity, which tends to slow down cosmic expansion, dark energy acts as a repulsive force, driving the universe to expand at an accelerated rate.

Changing Proportions

• Ongoing research indicates that the proportion of dark energy in the universe is increasing over time.
• This acceleration in the expansion of the universe is attributed to the increasing influence of dark energy, counterbalancing gravitational forces.

Summary

• The universe's expansion rate is not constant but accelerating, driven by the presence of dark matter and dark energy.
• Dark matter, inferred from gravitational effects, constitutes a significant portion of the universe's mass.
• Dark energy, acting as a repulsive force, counteracts gravity and speeds up cosmic expansion.
• Ongoing research suggests an increasing proportion of dark energy in the universe, contributing to the acceleration of its expansion.