Sunday, 24 October 2010

Of Doctors and Fools

So I was talking to someone at the university I attend the other day. The person in question was recently granted his Ph.D.

To celebrate, he and his friends went for a few drinks down the pub. One of his friends' girlfriend asked him in what field he had become a doctor. He told her that his Ph.D was in astrophysics.

She responded with "Really? What's my star sign then?"

At times like this I weep for humanity.

Saturday, 23 October 2010

Quantum Immortality (or how to be the luckiest person alive)

Firstly, I'd like to thank you all for visiting my blog, and I'm delighted with the positive reception there's been to my first few posts. Hopefully there'll be many more to come.

Today I thought I'd talk about quantum immortality, as it's quite an intriguing theory that can drive you mad thinking about it.

It's quite important that I first explain a little about quantum mechanics (don't worry, there won't be a test). In quantum mechanics, particles are described as wave functions. I don't want to go too in depth, so let's just say a wave function is 'a bit of maths' that describes how the particle behaves. The thing about wave functions is this - they describe the different possibilities of what the particle could be doing, and the probability of each possibility being observed. Confused yet?

The Everett many-worlds interpretation of quantum mechanics states that for each possible outcome of an observation of the wave function there is a universe in which that outcome is observed.

A way of looking at this is a coin toss. Before the coin is tossed, the outcome could be heads, or it could be tails. In the Everett many-worlds view, there is a different universe for every possible outcome of the coin toss - one in which it is heads, one in which it is tails, one in which the coin is dropped, one in which it spins five times before landing, one in which it spins six times, etc.

Now we get on to quantum immortality. Suppose I take a pistol, and point it at my head. Then I pull the trigger. Despite the overwhelming number of outcomes that involve me laying on the floor with a rapidly expanding pool of blood forming underneath my head, there will be a few universes in which I miraculously survive - the gun has jammed.

Now, let's say I'm in one of these universes in which I survived. I then take another pistol, and repeat the experiment. Again, there are a few universes where I remain unscathed.

This process continues ad infinitum - no matter how many times I repeat the process, a universe exists in which I survive.

From our perspective, this is merely a statistical inevitability. From the perspective of myself inside that universe, I have attempted to shoot myself in the head a hundred times, and not been successful once.

Wrap your brain around that one.

Thursday, 21 October 2010

The cosmic speed limit always holds

There's a question I've come across that often sparks some debate, and I feel I'm in a position to give some clarification.

The question in hand pertains to the cosmic speed limit - that of light. As I'm sure most (if not all) of you know that no object can travel faster than light, which has an astounding speed of 300000000 metres per second. That's pretty fast.

It is also accepted that information cannot travel faster than light. Let's say a coin is tossed, and if it lands on heads a red light will immediately activate, or green for tails. Since information cannot travel faster than light, there is absolutely the no way an observer at any distance could know the result of the coin toss before the light emitted reached them.

The question is this -  Two people are at a great distance from each other, holding a long rod between them. If someone at one end pushes the rod, will the other person feel the push before any light could have traveled between the two?

At first, the answer seems to be yes. For instance, let's imagine the distance is a lightyear (the distance light will travel exactly 1 year). It appears illogical that it could possibly take the recipient one year to feel the push.

However, information CANNOT travel faster than light. When the rod is pushed, the entire object does not move at once. Instead, a pressure wave is formed at one end of the rod which travels through the entire object. Imagine a slinky. Holding it horizontally, should you push one end quickly while keeping the other end still, you would see a wave travel from one end to the other. This is what is happening in our rod. You don't seen this on an everyday level, for objects like pencils and rulers this takes place in under nanoseconds.

The wave in the rod will travel slower than the speed of light, and Physicists can sleep easy knowing that the laws of relativity remain intact.

Tuesday, 19 October 2010

Tunnel Systems

I was asked an interesting question by my tutor today.

We had just finished working out a question concerning a tunnel drilled straight through the earth (ignoring the liquid core, the intense heat and all the other reasons it would be completely impossible to create such a tunnel). If one were to drop a stone though such a tunnel, it would accelerate, pass straight through the core and then start decelerating on its way back out. Assuming the earth to be a perfect sphere, and a complete absence of friction, the stone would forever pass back and forth through the tunnel.

Our tutor then asked us to consider a shorter tunnel, still passing through the earth but not through the center. Would the time it takes the stone to travel from one end to the other be shorter, or longer? At first it may seem obvious that the time would be shorter, due to the reduced length of the tunnel. It may also seem obvious that the time would be longer, since gravity would be weaker, due to more of the mass being one side of the stone than the other.

It turns out that for any two tunnels, the time would always be EXACTLY the same.

I think it's a beautiful example of how ingrained maths is within nature.


So, I decided to set up a blog.

I've decided to start a blog to share my various thoughts on basically anything. I love talking about science, music, video games and life in general, and thought his way I'd be able to broadcast my views without my friends having their ears talked off.

Please stick around and have a read, and I hope you enjoy your time here!