SuperCollider? I just met her.

I like Science Fiction.  It’s fun to read, write, watch and wear, particularly in hat format.

This impartiality has led me to conduct various sessions of low-quality research on the subject of cool space facts. 

Here’s some stuff I’ve picked up; hopefully there’s a thing or two in there that you didn’t know.

Part 1. Space n’stuff.

So space is curved.  huh?

It’s like this: If I throw a ball up in the air, it goes up for a while and then curves back down towards the earth.  The ball doesn’t turn a corner in the air; it travels in a straight line within curved space.

The gravity of the earth curves the space around it.

Everything that has mass (weight) has its own gravity.  You and I have our own gravity.  But the more mass you have the more gravity you have.  So our own gravity is completely overpowered by the earth. 

Imagine you had a big squashy floor, (like a really fat sheet of rubber or something) and you put a bunch of rocks on it.  Heavy rocks would make big depressions in the floor, while smaller rocks would make smaller dents.  This is a bit like space.  Heavy planets have more gravity.

Now imagine that you rolled a marble across the floor.  It would roll down the depressions and kind of get sucked towards the rocks.  This is how moving through space works; it’s just like a curved surface, except in three dimensions.

Another part of curved space is the concept of spacetime. 

Imagine we’re standing a short distance apart and I throw a ball to you.  If I lob it up in the air it might take two seconds to reach you, and if I throw it straight at you it might take half a second. 

What I can’t do is lob it up in the air in such a way that it only takes half a second to reach you, and equally I can’t throw it straight at you and make it take two seconds. 

This is because time is all wrapped up with the geometry of space.

Now, if we go back to rolling the marble across the bumpy floor, not only does the intrepid marble get sucked towards a heavy object, as it gets closer it also increases velocity (speed).  It’s like if you roll a marble down the side of a bowl, it picks up speed as it gets closer to the centre, and there’s a weird thing about this force.

If you’re in a car and you accelerate you feel g-force.  The car starts travelling faster than you, so it presses into your back which presses into your front and you get slightly compressed.  This is fairly mild in a car, but a car doesn’t travel that quickly. 

Too much g-force is bad.  This is the force that makes crashing your car unpleasant.  If it wasn’t for the g-forces involved you would just immediately come to a complete stop.

This was taken by Voyager.  The dot is Earth.

The satellite known as ‘Voyager’ is currently leaving the solar system at 61,200km per hour.  If you wanted to accelerate to that speed without suffering greater g-forces than what you experience normally in your car it would take about 50 minutes of accelerating.  But there’s a way to reach that speed almost instantly without any kind of g-force.

If you’re in an elevator and it suddenly goes upwards at 10 times the normal speed it would probably injure your legs.  But if the elevator suddenly falls downwards you immediately start accelerating towards the earth at high speed, but you don’t feel any g-force, in fact you’d be weightless.  That is, until it lands.

The reason that falling doesn’t involve g-force is that nothing is being compressed.  Gravity is pulling the elevator and all the different parts of your body downwards at the same speed. 

Now the earth isn’t that heavy, so its gravity is not that strong.  If you were free-falling on Jupiter you’d be accelerating 2.5 times as fast as you were on earth, but it would feel exactly the same. 

This is how Voyager came to be travelling at 61,200 km/h.  It travelled close by to Jupiter (the largest planet in our Solar System), it started falling down towards the planet and accelerating, then it just missed hitting the planet and got slingshot out the other side.

This is a good way to accelerate in space, but you have to already be going fairly fast if you want to avoid crashing into the planet.  It’s like skating on a half pipe.  If you want to fly off into the air you can’t just stand on the edge and roll down, you have to create some momentum that will fling you out the other side.

So how do you initially accelerate in space?

If you’re swimming in water you can accelerate by kicking your legs.  In effect you push against the water and that propels you forward.  But how do you accelerate in a vacuum? There’s nothing to push against.

The only current technique we have is by using rockets, which basically are forced to push off against their own exhaust.  The down side is that you have to be carrying enough fuel to leave a big trail of exhaust through space.  The up side is there’s very little resistance in space, so once you’ve accelerated you can just coast forever.

So that’s the basics of geometry in space.  Here’s where things start getting really strange.

Part 2.  Time is not constant.

Acceleration makes several strange things happen.

If I throw a ruler like a javelin, it will actually be slightly shorter while it’s accelerating.

Not only that but it will have slightly more mass (weight).

And here’s the weird one, it will experience slightly less time passing.

You heard me.

If I have two clocks set to exactly the same time and I throw one of them to you, the one that has travelled faster will be slightly behind the other one.

Of course at such low speeds the difference is almost completely negligible, but the effect becomes much more noticeable at high speeds.

If you have two twins and one of them gets in a spacecraft and travels at high speed for a while, when they get back to earth they will be younger than their twin.  Less time will have passed for them.

There is a limit to how fast you can go.  Light travels at about 1billion km per hour, and nothing that has mass can travel faster than that.  This was explained by Einstein with the famous equation E=MC^2. 

Basically as you go faster you gain more mass, and as you approach the speed of light the amount of mass shoots sharply upwards.  To be at the speed of light you need to have either no mass (like light) or infinite mass (which as far as I’m aware is not possible).

1b km/h is still pretty fast, but the universe is quite large.  The nearest star to earth (aside from the sun, obviously) is called Alpha Proxima, and it’s about 4 light years away.  (One light year is the distance that light travels in one year – roughly 10 trillion kilometres.)

This means that no matter how fast you go, it will always take more than 4 years to reach this star from earth.  To reach the centre of our galaxy (The Milky Way) will always take more than 27,000 years.  To get to the nearest galaxy will take more than 250,000 years.

So you see that there’s a bit of a problem getting around the cosmos, but fascinatingly you could still get there within a lifetime.

When you travel quickly, your time passes more slowly.  If you travel at just under the speed of light you could actually circumnavigate the entire observable universe (some 46 billion light years) in under, say, 30 years.

The only problem is that when you got back to earth you’d find that more than 92 billion years had passed there, and it would no longer exist. 

If you did go on this journey I wonder what you would see if you looked out your window.  I assume you would see the universe sped up 1.5 billion times its normal speed. 

Part 3.  Gone fission.

It’s currently believed that the universe began with a Big Bang.  The bang spread out a vast cloud of hydrogen.  Under the forces of gravity, portions of hydrogen started to coalesce into dense clouds, and then into blobs.  As there was so much gas in these blobs their combined weight was massive, which means that they had an equally massive amount of gravity which pulled them ever denser.  The pressures inside rose so high that they became extremely hot and bright.  They were the first stars. 

Inside the stars the heat and pressure were high enough for the hydrogen to undergo nuclear fission, turning into helium.  This is what our sun does.

In the biggest stars the pressures and heat would grow even higher, causing the helium to form into heavier elements like iron and carbon.

When a star runs out of fuel it sort of collapses in on itself and then explodes away most of its matter.  The iron and carbon that got sprayed out would sometimes form into big rocks that would get caught in orbit around another star.  This is what happened to the earth.

Sometimes after a star explodes away a bunch of its matter the heaviest elements remain.  Their gravity is so high that the elements keep compacting and their gravity becomes more concentrated until you have a sphere that is close to infinitely dense. 

This would be like compacting the entire earth down to the size of a grain of sand.

Strangely enough, light is affected by gravity.  Light is pulled towards heavy objects in the same way that matter is.  When a star has compacted enough, its gravity reaches a point where it is so strong that light can’t escape from it, forming what we call a black hole.

Light is bent by the gravity of a black hole

I’d always assumed that this compacted sphere known as a black hole would be very dark, but in fact it would probably be sending off an incredible amount of light, except that as soon as the light was expelled it would bend around and fall backwards.

Some people believe that a black hole curves space so much that it tears, meaning that you could pass through the tear into some other place or time.  The biggest problem is that there would inevitably be another black hole on the other side of the tear and you would then have to escape from the gravity, which is something that not even light can do. 

You’d also have to deal with the inconvenience of being instantly compacted into a microscopic point.

If you’ve read this far than my hat’s off to you.  Hopefully there was something in there that caused you a micron of interest.

If you noticed anything grievously erroneous in the above generalisations please leave a correctional comment.

I think next time I’ll write about aliens.  Stay tuned.