Tag Archives: relativity

April Fools’ Day Model of Space-Change

It is 1 April. This is NOT a joke but it may not be real. It’s a science thought experiment.

There’s a tiny bit of physics in my distant past but I am not a real physicist. In the last few years I’ve noticed the models of information I’m investigating resemble the ‘multi-worlds interpretation’ of quantum mechanics, which I have only heard about via radio, TV and Wikipedia. Quantum Mechanics is always rubbing up against Relativity, another idea about which I have a frustratingly inadequate understanding. I decided to investigate these worlds of weirdness but I find my brain getting horribly scrambled when I try to visualise space-time. I can’t and I don’t think anyone can. Our visual system has evolved for seeing a 3D world and that world changes. Humanity had lived, before the early 20th Century in a non-relativistic world. Those who do ‘get modern physics’ seem to rely on a mathematical understanding of the concepts.

In my models of information, I’d been thinking about the lack of a time-dimension in most computation. We usually model change in the world as a series of states, where data about a new state replaces the previous states. This starts to cause difficulties when computers have parallel paths of computation, as current multi-core processing chips do. Software has begun to address the problems with ‘immutability’. In simple terms, instead of replacing a value, a new value is added to the end of  a sequence, so historic values are retained. We have gone back before the memory-constrained computer age to learn from the Victorian hand-written ledger.

I became aware of research work at Cambridge University to reconcile ‘QM and R’ which also modelled time as state-change but I’ve found it very difficult to think about ‘the state change dimension of space’ as a sequence of events without falling back on ideas of time, speed and rate of change. The ‘idea of time’ which may be a cultural concept is deeply woven into our current paradigm.

In trying to free my mind of time, I’ve been hanging out in ‘the difficult time questions’ corner of Quora. Someone gave me a breakthrough by describing a simple clock:
Imagine going into deep space where gravity and friction to movement can be assumed to be zero. Throw an object. The distance it has travelled is a clock.

An April Fool thought experiment of time:
Make the object a spacecraft containing a holographic camera. Time passed can now be measured as a distance. Let us assume we prepared by asking someone to invent a unit of distance and mark it repeatedly on a very long tape, alongside the path of our space-craft. We don’t know the size of that unit. Now retrieve the holographic camera and put the recording medium in a holographic projector and project it onto a screen.
Think of the ‘slide-show’ as you being equivalent to you travelling along a sequence of equally spaced ‘holographic plates’. Consider changing the distance between plates in some regions of the recording (analogous to compressing time) or having instantaneously (enough) reversed the spacecraft during recording. Evidence of events would be passed in the opposite order but time would still be one way. Time could appear to be reversed if the projector was modified to play the recording in reverse order but that’s model hacking not reality.

Stage 2 – imagine this model as a streamed live-view of the universe, with the universe interfering with distances, as Relativity tells us it does, and has been observed. The problem is that a lot of the science assumes time is constant and that’s difficult to disprove from inside the space-time paradigm. We can only observe a space/state-change view and we may have invented time. Have fun with it.

Idea-bending minds, mind-bending ideas

Long ago, I took 4/9ths of an undergraduate physics degree, along with 4/9ths computer science and 1/9th mathematics. Having had little or no contact with physics in the intervening years, I’ve started to do some light reading about relativity in the last couple of years. This week, I came across a tip on Quora * to a fellow traveller in space-time: “stop thinking of the speed of light as a number”. Erm… WHAT?! As every school child knows, the maximum  speed of light (or any other form of electromagnetic radiation) in a vacuum is about 600,000 Km/s. That sounds like a number to me. The problem with speed in Einstein’s relativistic model of reality though, is that distance and time get very weird. That makes them hard to think about, so the advice was to ignore what we think we know and look at things in a new way.
[* – I’ll add an acknowledgement to the author of  the comment on Quora, if I ever find it again. It took me a while to understand what I’d read. ]

I’m not sure I was entirely paying attention when I studied physics last time. I don’t remember anyone explaining the precise nature of the the scientific method, or indeed what physics actually is; that’s metaphysics. This time around I see science as the process of understanding how nature works, using evidence rather than guessing then arguing the case for your beliefs. That is philosophy, or a religion. Physics, in particular, is about observing reality and working out what the rules are. It is NOT about saying why things happen. As science was becoming formalised, it was known as ‘natural philosophy’ i.e. philosophy that refers to evidence from nature.

Einstein’s Theories of Relativity say that matter and energy are equivalent. His equation of mass-energy equivalence records the relationship between the alternative mass and energy forms of matter. It is a very well known equation, even with people who have no idea what it refers to.

The form of the equation we are most familiar with is

E = mc²

E is the concentrated energy contained in a mass, m. E is a much bigger number than m because we know that c is a big number AND it’s squared.

This equation can be re-arranged to a form I don’t remember seeing or taking note of before:

c = √(E/m)

This new way (at least to me) of looking at this century old theory says that c is related to the ratio between the Energy and mass of an object. This ratio stays the same, even as space-time expands or contracts, according to the General Theory of Relativity. The recent confirmation by the LIGO project of gravitation waves that also travel at c, were also predicted, so this gives extra weight to the theory

I’ve realised that physics often relates things to each other, without saying which is the ‘fundamental thing’. Does gravity bend space-time or is the curvature of space-time what causes gravity? The equations work either way.

John Archibald Wheeler said it a different way: “Space-time tells matter how to move; matter tells space-time how to curve” and matter can be converted to energy, energy to matter.
Continue reading Idea-bending minds, mind-bending ideas