Thursday, September 22, 2016

TIME 3 - Time under duress

You're still with me?  Great.  Buckle up, because time is only going to get wierder.

Thank your uncle Albert for that...

Albert Einstein is of course famous for a couple of theories of Relativity which describe interactions between energy and matter, and particularly discuss how time changes with speed.  It also imposed a speed limit on the Universe.

And I mean an absolute speed limit.  Not like where we have a 55mph road, and you do 56mph and feel all ...

You can't go faster than the speed of light.  You don't get to play Spinal Tap, and do the speed of light ... plus 1.

And as my reader Ben pointed out, there's certainly no going .5 past the speed of light.  Also a parsec is a unit of measurement not time.  Your dad's been lying this whole time kid.

Let's try a thought experiment

Okay - we have the scenario below,

  • Star Destroyer - slow enough to be considered stationary
  • Millennium Falcon - moving away from the Star Destroyer at half the speed of light.  It is also firing it's forward laser cannons, the energy for which moves at the speed of light.

Let's look at it from the point of view of a couple of observers.

Darth Vader is on the Star Destroyer, and he can see the Millennium Falcon moving away at half the speed of light.  He can also see the laser beams which also are moving away from him at the speed of light.

The lasers go no faster for leaving an object which is already at half the speed of light.  You would think this would be a good case for .5 past the speed of light.  But no, the speed limit still applies for any observer.

Chewbacca is flying the Millennium Falcon.  I guess you can say he's flying it Hans-free.  Surely he sees the laser beams travelling slower?

No - he sees the laser also travelling away from him at the speed of light.  How can it be that two people at vastly different speeds are seeing those lasers travel at the same speed relative to their speed of motion?

The answer is they're observing time very much more differently.  For Chewbacca, time is going much slower than for Darth Vader.  That different is enough for the light to look like it's moving at the speed of light from his slowed-time framework.  This is called time dilation.

It's just a fancy theory isn't it?

All this of course sounds like a fanciful theory, with a bit of mathematical jiggery-pokery to make it work on paper.  Except science doesn't work like that (you're thinking of religion).

All my critical thinking senses are dubious.  As I've said to my office quite regularly, I'm a tester, I don't tend to overthink things when I can come up with an experiment to prove or disprove something.

Once Einstein had written his theory, it was up to physicists to look for proof ... and they found it!


We obviously don't have spacecraft capable of travelling quite so fast as the Millennium Falcon - but we have the next best thing ... the mighty muon.

Muons are an exotic subatomic particle.  It is pretty much a heavy electron - it has the same charge, half the spin, but 300 times the weight.

They're also highly unstable, with a mean life of 2.2 microseconds - that's 0.0000022 seconds - observed in the lab.  It decomposes into an electron and a couple of neutrinos.

They're found in nature - when cosmic rays (essentially high energy protons or helium nuclei) from outer space collide with the atmosphere they can create muons.  These muons are moving incredibly fast - 95 to 99% the speed of light.  But even at those speeds, the best they could travel in our atmosphere is about 600m.

So how are these particles, produced miles above us, able to be detected on the ground?  When we do the analysis, and apply relativity, this isn't surprising.  Moving at that speed, the particle has experienced much less time - and as we talked in part 1.  That means less change has occurred - so these particles reach the ground having yet to decay.

This brings us right back to part one.  We can't measure time, but we can measure change, which can give us an indication of time.

You can read more about other observations of time dilation here or can see the maths being explained a bit here.  It's not just a theory, we've managed (by thinking about it, and applying a little cunning) to do some neat experiments to observe it.

So what was the point of the "Time"series?

When I saw Jasper Fforde earlier this year, he talked about writing as a mental challenge.  To take an idea and work out how far you can explore and push things.  Start with something, an idea or definition, and keep pushing.

After seeing definitions like this ...

I wondered if I could take something that I knew, try to define it, explore the definition, try new things as I learned.

This thirst to think and play with ideas - I'm not sure if it's exclusively a critical thinking thing.  It's definitely a science thing.  But it's something that drives me a lot - why so much of this blog is about playing with ideas to understand them better.

This blog series was actually originally written several months ago - and part of the reason I've thought very hard about trying covering more science in my spin-off I've talked about here

Now Playing - "To Love Somebody", the amazing Nina Simone


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