The Universe consists of energy and matter irregularly spread out,
scattered or divided up throughout the Universe is expanding of curving space-time,
but most of the matter and energy is not visible to humans.
- scientists now believe that the Universe is made of 70% dark energy (see Big Bang), 27% dark matter, and around 3% ordinary “luminous” matter in the form of stars and galaxies.
- ordinary luminous matter is clumped together in objects of varying size and densities – the term “objects” refers to individual items that astronomers can examine through telescopes.
- on Earth matter supports in three forms, as gas, liquid and solid – there are fourth form of matter; a completely converted totally ionized gas known as plasma – that can only be made in the laboratory. (example diagram)
- beyond Earth’s atmosphere, however, plasma is extremely common and is the main component of the “wind” produced by stars and the intergalactic medium from which they form.
- largest astronomical objects are galaxies; following in terms of diminishing size by nebulas, stars, planets, moons, asteroids, comets and meteorites.
- all galaxies are made up of many billions of stars – they are considered to be a single – “one object” – this is because their stars orbit around common centre of gravity and have the same relative motion with respect to the rest of the Universe.
- objects be given tending towards a spherical shape because of gravitational forces across the surface of a sphere are in equilibrium.
- rotation making twist and press out of a shape – spherical objects into a discus-shape; for example, our Earth bulges around the Equator. (diagram)
- objects of less than about 50 miles in diameter have insufficient mass to achieve a spherical shape – that’s why smaller asteroids all have irregular shapes. (diagram)
Back to The Universe page.