The Biggest Day in History: The Big Bang

“Albert, How long have we been travelling?”

Oh a thousand years or so.

“That’s impossible?”

Why?

“Well, it seems like no time at all.”

Time, like most things in life, is relative. Talk to a pretty girl for an hour and it seems like a minute. Sit on a hot stove for a minutes, it seems like an eternity.

“So what year is it now on Earth?”

Let me check my watch…it’s the year 4BC.

“Four years to go until Jesus Christ is born.”

You’d think so wouldn’t you, but it seems that with all the messing around with calendars over the years and history being a bit woolly, things got a bit out of sync. It seems that Jesus was probably born four years earlier than he should. Around now in fact.

“How can you mess with time, and lose four years?”

Oh, it’s not so hard. History is what happens while people are just getting on with their lives. By the time history has become important time has moved on, and people’s memories aren’t as good as they think. As for messing with time, how about leap years? Every four years an extra day appears out of nowhere?

“Well it seems easier to get an extra day than loose one.”

In England in 1752 they lost eleven days. Wednesday September 2^nd was followed by Thursday September14^th when they changed the calendar to get back in step with the rest of Europe. Before that the English and the French couldn't even agree on what date it was. So time and dates can’t really be relied on, but sometime around this date back on Earth, three old men are on a journey too, trekking across Asia following a star.

“The star of Bethlehem! Was that a real star or just a story?”

Well that’s a big question that we sadly don’t know. There are lot’s of theories. It could have been a real star that suddenly exploded, or another bright object like some of the planets lining up or a comet. When we get near to Earth we’ll have a closer look at comets and planets, but for now no-one really knows.

“But Jesus’s birthday, that’s a big day in history even if they did get the date wrong.”

Not as big as the biggest day.

“What day was bigger than that?”

Well, the day the universe was born.

“You mean all this hasn’t always been here?”

It’s been here a very long time but not forever. We now think the Universe had its own birthday; the Big Bang.

"The Big Bang? We've been travelling through space for a thousand years and I haven’t heard a thing, apart from you talking in my head of course.”

Well, as we are imaging ourselves to be photons we don't have ears anymore. Also the Big Bang was around fourteen billion years ago and sound waves don't travel in space.

"Why not?"

Because sound waves are just vibrations in air or water or whatever they are travelling through. Without water there can’t be waves in the ocean and without air can’t be sound waves in space. There is no such thing as a sound particle.

“All those crashes and explosions in the Star Wars films wouldn’t really happen?”

Not at all. War in space would be totally silent, though I do hope by the time humans are flying around the galaxy for real they have come to realise that war is pointless.

"What about us, how can we… well how can light travel through space?"

We exist in our own right, we're photons, light particles. That's why we can travel through a vacuum like space. Don’t worry I’ll explain all about what light is and how it travels later.

"So what exactly was this silent Big Bang all about?"

The Big Bang was the start of everything when all the matter in the universe and space itself suddenly came into existence in one place which was very, very hot; about a trillion degrees or so. From this first huge explosion of creation, everything started expanding in all directions and the universe has been expanding ever since. The Big Bang is the cosmological version of the creation story in the Bible. In the bible God had six days to create heaven and earth and one to rest. In the science version the pattern of the next few billion years was sorted out in the first thousandth of a second, everything after that is supposed to be following physical rather than divine laws. Talking of God, I have to confess something about the Big Bang.

“Confess?”

When I first heard ideas like this I thought it was bunkum, complete nonsense.

“How did you think the universe started?”

Well, I thought like you that it had always been there and always would be. I had never asked myself the question of where it came from. Then a young Russian mathematician, Alexander Alexandrovich Friedman, tried to show that my own equations allowed the universe to be expanding. That was back in 1922.

“What did you do?”

To my shame I assumed he must be wrong and wrote a letter saying as much. Then a year later I re-checked and found out his calculations were right and it was possible that the universe could expand, but I still didn’t believe that it really was expanding. No-one else seemed to believe it either until a young Jesuit priest, Georges-Henri Lemaître, from Belgium who was studying physics went one step further.