Changing ideas about universe (Edexcel GCSE Physics): Revision Notes
Changing ideas about universe
Geocentric Model (Up until the 1500s)
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The Geocentric Model suggested that the Earth was at the centre of the universe, and everything, including the Sun, Moon, planets, and stars, orbited the Earth in perfect circles. Why did people believe this?
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Lack of technology: People didn't have telescopes to observe the universe in detail.
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The Sun and Moon appeared to move across the sky in a consistent way, leading people to think Earth was the centre of everything.
Heliocentric Model (16th Century)
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The Heliocentric Model proposed that the Sun was at the centre of the solar system, and the Earth along with the other planets orbited the Sun in perfect circles. Galileo's Evidence:
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Galileo Galilei made a key discovery using his telescope: He observed four moons orbiting Jupiter (now called the Galilean moons).
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This proved that not everything orbits Earth, challenging the Geocentric model.
Current Model of the Solar System
In the current model, the planets, including Earth, orbit the Sun in elliptical (oval-shaped) orbits, not perfect circles. This model is widely accepted based on modern astronomical observations.
Theories About the Creation of the Universe
As scientists observed that the universe is expanding, various models were developed to explain how the universe came to be.
1. Steady State Theory
- The universe has always existed in the way we see it now, and it will always remain the same.
- As the universe expands, new matter is constantly being created, so the density of the universe stays roughly the same.
- There is no beginning or end to the universe in this model.
2. Big Bang Theory (Accepted Theory)
- The Big Bang Theory suggests that the universe began as a small, very dense, and hot space.
- About 13.8 billion years ago, the universe exploded and started to expand, and it continues to expand today.
- The Big Bang Theory is widely accepted because of the evidence supporting it, such as the cosmic microwave background radiation and the observation of galaxies moving apart.