Is the universe infinite? Does it end somewhere? Is the volume endless? If it expands, what does it expand into? What was the location in the universe where the Big Bang took place? What does the Big Bang Day Logo stand for? What is our purpose in life?

There are some relatively simple answers to these questions. Well except for the last one. We’ll leave that one up to you, but will try to answer the others below. We make no claim that these answers are in any sense definitive or complete. Our knowledge always has and to our personal estimate probably always will be limited. Will have a horizon. Not everyone within our movement or within the science community thinks so, but that is a topic for another post. But whereas we do indeed not claim these answers to be perfect, they do cut the observable facts very elegantly.

We’re gonna take three simple concepts:

  1. A bit of twentieth century data from our telescopes: that almost all galaxies move away from ours;
  2. A concept that an ancient Greek, Babylonian or Indian thinker might have thought up just as well as us: seeing time as an extra dimension in addition to the three spatial ones we experience, and
  3. This nineteenth century knowledge: that light travels at a limited speed

Piecing these three together will end us up with a map of our universe including its history. Incidentally, that map looks just like our Big Bang Day logo. As we go, we will also find out why the Big Bang was not an explosion of a lot of stuff from some point within a huge dark and empty space. So let’s start the lecture.

(1)  Everything wants to get away from us!

If we look up into the skies, we find that almost all galaxies move away from us, and the further away one looks, the faster they move. A first guess might be “Hey, we are special after all: the Big Bang took place right where we are. We are the centre of it all!” Sorry, that does not fly. It is easy to show that the ‘everything moves away from me and the further away it is, the faster it does so’-rule applies to all places in the visible universe.

So the total volume (in cubic litres) of the universe is growing. But into what? And are there borders to it? Can I run into a Great Wall if I travel far enough? Or fall of the edge like sailors feared to in Columbus’ time? The simplest interpretation of the data seems to tell us: no there’s no edge, all you might run into if you travel upwards from, say, a launch station at the Earth’s North Pole, is the South Pole. And indeed: there is a limited number of litres the Universe contains. A lot, but limited to a finite number. But why? We’ll have to simplify things a bit before we get to the answer.

(2)  A one-dimensional philosopher

Imagine the simplest universe one can have: one that is line-shaped or one-dimensional. You are a line-shaped person living in it. Undoubtedly, you will wonder if your world extends endlessly, and if there is finally a boundary to it. If you will either run into a wall (dot-shaped), or fall off if you travel far enough. What you will definitely not come up with though, being one-dimensional and all, is that you do not actually inhabit a line-shaped world, but in fact one that curves back into itself to form a ring. That however, seems to be exactly the case.

Now your next door-neighbour would block everything else from view to your left, and your own house would to the same to the right, but let’s say you are somehow able to X-Ray your universe, or everything in it is see-through. What you would then find is that everything moves away from you, and the further away it is the faster it does. A troublesome conclusion, but not for us three-dimensional humans. We’ll easily see: your universe is indeed a ring expanding outwardly, like ripples in a pond after throwing in a pebble.

 

 

 

 

 

 

 

Your Big Bang did not happen anywhere within you current universe, but in a point at the centre it has abandoned immediately at that moment, just as it abandons its entire previous location at every moment in time. Your universe started out as a single point, formed a ring around it at the Big Bang and has constantly rippled outward from that time on. What you consider ‘space’ is fully contained in that ring-shaped line, and its past is the two-dimensional content of that ring: a circle with the Big Bang as it’s centre with this moment as it’s edge. The future radiates out in all four directions open to a two-dimensional shape. ‘Time’ is measured by one’s distance to the T=0, or the Big Bang.

 

 

 

 

 

 

And a two-dimensional astronaut

Now add one layer. We’ll stick an axis through the ring and give it a spin. Do you see it makes a sphere? Now we can imagine being a two dimensional being in a flat world, as if you lived on the surface of a piece of paper.

 

 

 

 

 

 

 

 

 

Viewed like this, we can take a two-dimensional action and ‘fixate’ it into a three-dimensional object. Take for instance a flat ‘surface’ (a line) on which two beach balls (ring-shaped) bump into each other and then bounce back. Take pictures of this occurrence and place them behind each other. Now connect the lines. Do you see it forms an ‘X’ made of converging and then diverging tubes? Brilliant, we’ve just converted time into space, an activity into an object, movement into stillness!

 

 

 

 

 

 

 

Now, being a two-dimensional person, circles hold no mysteries for you, but spheres are surely beyond your grasp. The concept just does not make sense. But when you aim your telescopes at the sky and find that everything moves away from you, you might conclude that you live on the surface of what you might call a ‘hyper-circle’ that expands outwardly.

 

 

 

 

 

 

Us humans call this hyper-circle a sphere and can see that a two-dimensional universe is like a balloon that someone – ah, God must be a balloon-blower! – is blowing up. All of its space is contained within the surface. Our flat friend cannot fall out and will not stumble on an edge anywhere, but his universe counts only a limited number of square metres. It is finite but without borders. ‘History’ is the content of the balloon, particles and persons and stars slavishly drawing lines outward in all the six directions a three-dimensional person can choose freely from.  All galaxies on the balloon move away from each other as it expands, and the further away one looks, the faster they move. And this goes for every galaxy there is. If a flat astronaut travels far enough from her planet’s North Pole, she will finally end up to her bewilderment flying into the South Pole she is so familiar with.

Which gets us to: us

So you, human, seem to live within the three-dimensional ‘surface’ of a four dimensional ‘hyper-sphere’, expanding in eight directions from a point within its long abandoned centre. At that point, some thirteen point seven billion years ago, everything took off, an event we call ‘the Big Bang’ nowadays. And by ‘everything’, I do not just mean all matter, but indeed space itself as you now understand. Your universe contains a limited number of cubic litres but has no edge. And if you fly far enough, you will end up at your own foot soles. A four dimensional nerd is currently explaining this to one of his friends, and they easily understand the exact shape of this ‘hyper-sphere’ we find so hard to grasp but takes a five dimensional person to understand exactly what their universe looks like.

(3)  Lazy Light Particles and a small tour of the Universe

Here, we need to add our final ingredient to this story: the fact that everything in our universe has a speed limit. If it has no mass – such as a ‘photon’ or light-particle – it moves at a steady pace of almost three hundred thousand kilometres a second. If it does have mass – such as an electron or you and me – it moves slower than that. Incidentally, this means we will never be able to actually fly upwards from the our North-Pole launch station and end up arriving at our South-Pole Welcome Home Universal Columbus station, but that is not my point now.

Point is this: as light travels at a limited pace, if you look at me, you will see me one tiny fraction of a second younger than I ‘currently’ am. It takes light just under one and a half seconds to reach Earth from the Moon. Our Sun if further away from you than I am, and even further away than the Moon is and from the Sun, light takes some eight minutes to get here. If the Sun were to explode right ‘now’, we would not burn to a crisp until eight minutes later.

Fly a bit further with me. After the Sun, Alpha Centauri is the closest star from here. We see it four years younger than it is. That’s nothing though. A distant star within our ‘Milky Way’ galaxy can be some one hundred thousand ‘light years’ away. So if someone from there is looking right at us as we speak, he would not see you reading this website, but a Homo-Erectus being chased by a sabre-tooth tiger. And that too, is nothing yet. The farthest object our telescopes can see, is some thirteen billion light years away. We stare down a steep abyss into the distant past.

Hey, but did we not say the Big Bang occurred thirteen point seven billion years ago? Indeed, if we look far enough, we see a baby universe and make baby pictures of it. As it is small, it is dense and hot. We stare into the eye of an explosion. A Big Bang indeed. The Big Bang. Light is a time travelling messenger bringing us a birth certificate of our own universe. And if something is looking back at us from those far reaches right now, it sees the same thing we do: a baby universe in which neither Earth nor Sun exist yet.

And to conclude, we return to our starting position. But now it makes sense

Back to the ripples in the pond. And to the Big Bang Day logo below. Where you threw your pebble, the Big Bang occurs. That’s the centre of the logo. Each next concentric ring is a next moment. Space is contained in the rings, time flows outward in four directions from the centre. We’ve only included one of those circles: the current moment, which is the outer circle of the logo. We find ourselves at just one unremarkable point – the dot on the right – in the circle that is marked thirteen point seven billion years outward from T=0. We call the whole ring with T=0 as its centre ‘this moment’, but will have to confess that the visible universe is something very different. At our own eye’s retina, what we actually see starts breaking away from the fictional construct called ‘now’, eventually forming a smaller circle within the other one. The further away we look, the larger do they differ, the visible universe forming a smaller circle within the ring, ending up exactly in the hot and dense ‘explosive’ centre which is our baby universe just after the Big Bang:

 

 

 

 

 

Awesome BBD!

 

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