My Science School

We don’t know. Life might be such a fluke that it only exists on Earth. But if scientists can find just one other place where there is life, we’ll know life’s no accident - and that there could be millions of aliens!

How will we find out?

People around the world have joined the Search for Extra-Terrestrial Intelligence (SETI). They spend their spare time on computers, studying waves from space, hoping to find alien messages.

Do aliens know about us?

It’s unlikely. Humans have only been making radio waves for about a century, so aliens would have to live very nearby to tune in.

Is it true? Aliens have visited the Earth.

Probably not. There’s no proof that aliens have visited us. Even if they could travel at the speed of light, they would take at least four years to reach us from the nearest stars.

Amazing! Some people think that the Universe is a living thing - and that the planets, stars and galaxies are just parts of its ‘body’!

Picture Credit : Google

Gravity is one of the basic forces in the Universe, like electromagnetism. It makes things with mass pull towards each other. More massive objects, such as the Earth, pull smaller objects, such as you, towards them until they stick together.

Is it true? An apple taught us about gravity.

Maybe. According to legend, super-scientist Isaac Newton first realized how gravity works over 330 years ago, after gravity pulled an apple from a tree he was sitting under, and it landed on his head!

Is the Universe expanding evenly?

No - the force of gravity stops everything from flying outwards. Lumpy bits of space become even lumpier, moving at different speeds. Gravity locks together little pockets of space and matter, such as galaxies.

Amazing! There are walls in space! Galaxies aren’t evenly spaced through the Universe. They are arranged more like walls around emptier regions of space. One wall has already been measured – it’s about a billion light years across!

What is the Great Attractor?

It’s a strange little knot in space that has the pulling power of 50 million billion Suns, but is not a black hole.

Picture Credit : Google

No, time slows down when you’re travelling very quickly. Brainy boffin Albert Einstein predicted this odd effect in 1905 but we only proved it a few years ago by sending a super-precise atomic clock into orbit around the Earth.

Could time stand still?

Only if you travelled as fast as the speed of light - which most scientists agree is impossible! Some scientists think that time must stand still inside a black hole, but who’d want to find out?

Is it true? Einstein was the world’s best mathematician.

No. Although he was very clever, Albert Einstein often asked his wife to check over the trickier sums for him.  

Amazing! There might be ‘tunnels’ through space and time, which connect distant parts of the Universe. Scientists call these shortcuts wormholes. If light or even an object entered a wormhole, perhaps it would pass through incredibly quickly. It would be possible to travel billions of kilometres in an instant!

Is time travel possible?

Not as far as we know. If you could invent a machine which seemed to take you back or forwards in time, it would probably be taking you to different universes.

Picture Credit : Google

Our galaxy, the Milky Way, is a spiral galaxy. Viewed from above, it looks like a giant Danish pastry with swirls of white icing. From the side, it looks more like two fried eggs stuck back-to-back!

Amazing! Our galaxy has a twin. Andromeda is the biggest galaxy near the Milky Way. It’s the same age and a similar shape, but has many more stars.

What’s at the middle of the Milky Way?

The centre (the two ‘egg yolks’) is called the nuclear bulge. There’s probably a monster black hole there, more than a million times bigger than our Sun. Scientists call the black hole Sagittarius A*.

How big is the Milky Way?

The Milky Way is almost too big to imagine. It would take the world’s fastest jet, the Blackbird, about 30 billion years to cross the galaxy.

Is it true? We’re near the centre of the Milky Way.

No. Our Solar System is closer to the edge, on one of the spiralling arms. Our Sun takes 225 million years to go around the centre once!

Picture Credit : Google

A galaxy is a group of stars, dust and gases that are held together by gravity. Our galaxy is the Milky Way and contains about 100 billion stars, one of which is our Sun.

Is it true? All galaxies have names.

No. Each one that we detect is given numbers and letters, but only some, such as our Milky Way, are given a name as well. ‘Galaxy’ comes from the Ancient Greek word for ‘milk’.

How many galaxies are there?

No one knows for sure. There might be hundreds of billions of galaxies - and new ones are forming right now at the edges of the Universe.

Are there different kinds of galaxies?

Yes - each galaxy is unlike any other. Some are bright and some are dim. There are three basic galaxy shapes, though - spiral, elliptical (oval) and irregular. Of course, irregular just means no particular shape!

Amazing! There’s a galaxy named after a wide-brimmed Mexican hat. ‘Sombrero’ is the nickname of galaxy M104. Can you guess the galaxy’s shape?

Picture Credit : Google

A black hole is a place in space that forms when a really huge star collapses. Everything around a black hole is sucked into it, like water down a plug hole. The force of gravity in a black hole is so strong that nothing can escape from it - not even light.

Amazing! No one has ever seen a black hole. Because beams of light cannot escape black holes, astronomers cannot see them - even with the most powerful telescopes.

What is dark matter?

Dark matter is what scientists call all the stuff in the Universe that they know is there but can’t find! They think it might be made of ghostly little particles called neutrinos.

Is it true? Black holes turn you into spaghetti.

Yes. Scientists think that, in the last moments before you disappeared forever into a black hole, the force of gravity would stretch you until it pulled you apart. They call this being ‘spaghettified’!

How do we know that dark matter is there?

Scientists can guess how much matter is in the Universe by measuring how galaxies move. This shows them that stars and planets only make up a small part of the Universe. The rest is invisible!

Picture Credit : Google

Scientists have argued about this for centuries. At the moment, most people agree that the Universe began between 12 and 15 billion years ago. It all started with a mind-boggling explosion called the Big Bang.

Amazing! The Big Bang was super-hot! Scientists don’t even bother writing out all the zeros in its temperature. They write 1027 C meaning 10 with 27 zeros after it!

What was the Big Bang?

It was a huge explosion that created all the mass and energy in our Universe in less than a second! The effects of the blast are so strong that the Universe is still expanding.

What if the Big Bang happened again?

It couldn’t happen again in our Universe, but some people think it may be happening millions of times, making millions of different universes. Only a few would last as long as ours — most would pop like soap bubbles.

Is it true? You could see the Big Bang through a telescope.

Nearly. Our telescopes aren’t powerful enough yet - but we can already see light from the other side of the Universe that began its journey just after the Big Bang!

Picture Credit : Google

LGM stands for ‘Little Green Man’. LGM1 is a light deep in space that flashes 30 times a second. It is a pulsar - a tiny, dense neutron star (the remains of a supernova) that flashes out light and radio signals as it spins.

Is it true? Scientists thought pulsar signals were messages from aliens.

Yes. The astronomers in Cambridge, England, who discovered LGM1, wondered at first if they’d come across an alien distress beacon or some other kind of coded message!

Amazing! Neutron stars are super-heavy! They can be just 20 km across, but weigh 50 times more than planet Earth!

How many pulsars are there?

No one is sure, but hundreds have been found since the 1960s, when scientists first spotted the Little Green Man. Special telescopes called radio telescopes are used to ‘listen’ for more pulsars.

Do all pulsars spin at the same speed?

No — even the slowest spin about once every four seconds, but the fastest whizz round many hundreds of times in a single second! Their incredible speeds are thought to be caused by magnetic forces left by a supernova.

Picture Credit : Google

Every person, planet, star and galaxy is part of the Universe — and even every empty space! The Universe is the biggest thing we have a word for.

Amazing! The Universe is too big to measure in kilometres. Even if you could travel at the speed of light, it would take at least 15 billion years to cross it - as far as we know!

What’s outside the Universe?

It’s impossible to say. Scientists are still trying to guess, by using clues left behind from the birth of our Universe. They are pretty sure there would be no time, distance or things there.

Where are we in the Universe?

People once thought Earth was at the centre of the Universe. Now we know Earth is one of many planets moving through space. It’s hard to tell where we are because we can’t see the Universe’s edges.

Is it true? There are more stars than people.

Yes. As a rough guess, scientists think that there are about 1.8 million million stars for every human being alive in the world today.