What do we know about the place of the Earth in the Universe?
In I/GCSE Physics,
The Earth is one of eight planets orbiting the sun in almost circular paths, together with other smaller objects including asteroids, dwarf planets, comets and moons. The solar system is made.
The smaller masses in our solar system are:
- Planets – eight large masses that orbit (move around the sun)
- Moons – small masses that orbit the planets
- Asteroids – small, rocky masses that orbit the Sun
- Comets – small, icy masses that orbit the sun
- Dwarf planets – small spherical objects that have not cleared their orbits of other objects
The solar system was formed over a very long period of time, about 5000 million years ago:
- The solar system started as clouds of DUST and GAS, which were pulled together by the force of gravity
- This created intense heat. Eventually, NUCLEAR FUSION began to take place and a star was born: the Sun
- The remaining dust and gas formed smaller masses, which were attracted to the sun
In I/GCSE Physics, our sun is one of thousands of millions of stars which form the Milky Way. There are thousands of millions of galaxies and every galaxy is made up of thousands of millions of stars – all these galaxies make up the UNIVERSE.
Because stars are so far away, all the evidence we have about distant stars and galaxies come from the RADIATION astronomers can detect. A lot is shown when studying the ELECTROMAGNETIC RADIATION it emits – e.g. the colour the star appears shows its surface temperature.
Light travels at very high but FINITE (limited) speeds. This means that if the distance to an object is great enough, the time taken for light to get there can be measured.
The speed of light is 300,000km/s in a vacuum.
In I/GCSE Physics, vast distances in space are measured in LIGHT YEARS. One light year is the year is the distance light travels in one year (approximately 9500 billion km). The finite speed of light means that very distant objects are observed as they were in the past, when the light we now see left them.
E.g. the nearest galaxy to the Milky Way is 2.2 million light-years away. This means that light from this galaxy has taken 2.2 million years to reach the Earth, and so we are now seeing the galaxy as it was in the past.
Good Job! You finish it.