IN­FI­NITE SKIES

Space is vast and full of won­ders – let’s find out more about the end­less uni­verse

DRUM - - Soapwatch -

WHEN you look at the sky on a dark, cloud­less night you can see count­less stars and the moon. In the day­time you can see the sun ris­ing and set­ting. We take a look at how the uni­verse be­gan and learn more about celestial bod­ies.

THE BIG BANG

Most as­tronomers be­lieve the uni­verse started about 14 bil­lion years ago with a mas­sive ex­plo­sion – the Big Bang. They spec­u­late that be­fore the Big Bang the uni­verse was just a tiny ball, a thou­sand times smaller than a nee­dle’s point. But it was ex­tremely hot and dense and sud­denly ex­ploded with im­mense force. The re­sult­ing Big Bang, sci­en­tists be­lieve, was what cre­ated time, space and mat­ter, and gave birth to the uni­verse. In a split sec­ond the uni­verse ex­pan­ded, from be­ing smaller than a sin­gle atom to be­com­ing big­ger than a gal­axy – and ac­cord­ing to science the uni­verse con­tin­ues to ex­pand to this day at an in­cred­i­ble pace. Sci­en­tists base their the­o­ries in this re­gard on ev­i­dence such as the night glows or cos­mic back­ground mi­crowave ra­di­a­tion from the Big Bang that can be ob­served with sci­en­tific in­stru­ments. Amer­i­can sci­en­tist Ed­win Hub­ble (18891953) doc­u­mented the move­ment of the gal­ax­ies in the 1920s. He de­ter­mined that the speed of a gal­axy is equal to its dis­tance from Earth. This com­par­a­tive rate is known as Hub­ble’s Law.

OUR PLACE IN SPACE

Cen­turies ago peo­ple thought Earth was at the cen­tre of the uni­verse and every­thing re­volved around it – the sun, moon and stars. To­day we know Earth and the other plan­ets in our so­lar sys­tem move around the sun.

We also know that our so­lar sys­tem is part of a vast spiral-shaped gal­axy known as the Milky Way.

There are sci­en­tists who think our so­lar sys­tem orig­i­nated when large clouds of dust and gas im­ploded, caus­ing a down­ward cir­cu­lar mo­tion – like wa­ter wash­ing down a drain. The sun and plan­ets then emerged out of the mist (neb­ula).

THE MILKY WAY

Our so­lar sys­tem is lo­cated in one of the spi­rals of the Milky Way, a ga­laxy made up of bil­lions of stars and their plan­ets, as well as dust par­ti­cles and gas. It re­sem­bles a gi­ant whirlpool that turns at its cen­tre once ev­ery 200 mil­lion years.

This gal­axy is so vast that it takes light about 100 000 years to travel from one end to the other.

There are bil­lions of other gala­xies in the uni­verse. OUR SUN The sun is mas­sive and com­prises about 98% of the mat­ter (any sub­stance that takes up space) in our so­lar sys­tem. Be­cause of its enor­mous mass, the sun’s grav­ity is the strong­est in our so­lar sys­tem and draws every­thing else to­wards it. But the plan­ets also have their own grav­ity, which causes them to re­main in set or­bital paths around the sun.

The sun is the clos­est star to Earth and emits life-giv­ing sun­light and heat. But sun­light also con­tains po­ten­tially harm­ful ul­tra­vi­o­let rays that can cause sun­burn and skin can­cer. The sun is ac­tu­ally a huge ball of su­per-hot gas some 1,4 mil­lion km in dia­me­ter (the size of 109 Earth-sized plan­ets placed next to one an­other). Its mass is equal to 330 000 Earths, and about 1,3 mil­lion Earths could fit in­side it.

Look­ing at it from Earth the sun might not seem that big, but re­mem­ber it’s about 150 mil­lion km from us. At this dis­tance it takes sun­light (at a speed of about 300 mil­lion m/sec) about eight min­utes to reach us. THE PLAN­ETS In ad­di­tion to the sun, our so­lar sys­tem con­sists of eight main pla­nets. The four rocky ones clos­est to the sun – Mer­cury, Venus, Earth and Mars – are rel­a­tively small.

Be­yond Mars there’s an as­ter­oid belt – a col­lec­tion of rocky ob­jects and space de­bris left over af­ter the plan­ets were formed.

Be­yond this rocky belt we find the four gaseous giants – Jupiter, Saturn, Uranus and Nep­tune. Al­though much big­ger than Earth, these plan­ets are rel­a­tively light in weight be­cause they’re made up mainly of hy­dro­gen and he­lium gas.

Pluto, an icy world on the out­skirts of our so­lar sys­tem, is re­garded as a dwarf planet be­cause it’s con­sid­er­ably smaller than our moon. THE MOON Earth’s nat­u­ral satel­lite, the moon, is made of rock. The moon’s or­bit around Earth takes 27 days, but the moon also takes 27 days to make a full turn on its own axis. Be­cause Earth also turns (on its own axis as well as around the sun) it seems to us like the moon’s or­bit around Earth takes 29 days. The moon’s grav­ity is re­spon­si­ble for ocean tides on Earth.

Sci­en­tists be­lieve the moon orig­i­nated 4,5 bil­lion years ago when Earth was cre­ated. They spec­u­late a mas­sive rock col­lided with our newly formed planet, slic­ing off a part of it which then be­came the moon.

The moon doesn’t have an at­mos­phere (layer of gas and liq­uid) around it to pro­tect it against comets and me­te­ors, or ra­di­a­tion from the sun. It there­fore gets ex­tremely hot and cold.

Earth’s at­mos­phere causes most in­com­ing me­te­ors to burn out be­fore they can hit the ground, but on the moon me­te­orite strikes can cause huge craters. Its sur­face is cov­ered in a dust layer about 5cm thick. This dust prob­a­bly comes from space or is the re­sult of the im­pact of me­te­orites.

An artist’s im­pres­sion of the WMap (Wilkinson Mi­crowave Anisotropy Probe) space­craft that was used to mea­sure the night glow or cos­mic mi­crowave back­ground ra­di­a­tion be­tween 2001 and 2010 to help sci­en­tists un­der­stand more about the Big Bang.

The Milky Way gal­axy has be­tween 100-400 bil­lion stars (in­clud­ing our sun), but when you look up into the night sky the most you can see is about 2 500. The heat and light from our sun come from nu­clear fusion, quite a dif­fer­ent process to that of fire...

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