Einstein WAS right....

....Einstein was probably one of them!

(Close Encounters of the Third Kind)

In my last post on relativity, I intimated that the speed of light IS constant. By constant, this means the same for all observers.

Those smart-asses who say 'but the speed of light in glass and water is different, so it can't be constant' have entirely missed the point. "Constant" refers to all observers travelling in the same medium that light is travelling through at the time, be it water, air, or a vacuum.

Indeed a vacuum is always chosen because in all measurements of the speed of light, none is ever bigger than that measured in free space.

NOW we start. I doubt many people do not know where all this came from, but it is quite simple, and is called "The Principle of Relativity".

To make you realise what it is, perhaps a few questions would suffice.

How fast are you going right now? Most of you will say you are sitting, and are therefore not moving. A few will say " At about 100kph, I am on a train". The question really is, how fast you travelling relative to the Earth. The first group has answer 0 kph, and second group 100 kph, relative to the Earth.

But how fast is the Earth moving? Well, relative to the Sun, about 30,000 kph, as the Earth goes around it.

How fast is the sun moving? Well, relative to the galactic center, about another 250,000 kph.

We don't notice this because of a blanket surrounding us called "The Atmosphere" which travels along with the Earth, so we are only aware of travel on the Earth.

So, how fast are we really travelling? 100kph? 30,000 kph? 250,000 kph?, or their sum, 260,100 kph?

Yes, but what is the Galaxy moving relative to? The answer is the Local Group, and the point is, the process can go on for a long time to calculate real speeds.

So, how fast you are going actually means "How fast are you travelling past object X".

Simple mechanics with a little thought.

However, Einstein went further. His question was this:

" If in free space, with no 'object X's' to measure with, how fast are you travelling past that there other spacecraft? With a little more thought, you can see that the answer is not clearly cut, for you could be stationary, and the other spacecraft is moving past you. SO, who , in the end, can say which one is moving and which stationary? Indeed, BOTH spacecraft could be moving and you would never know the difference!

Next time you take the kids out for a drive, get in and ask them to hide under a blanket at the back, so they cannot see out. Next, jump up and down in your seat a little, your wife too, and the kids will be convinced you have started!

Point is, if you have nothing by which to tell you if you are moving (a tree, a bump in the road, another spacecraft), it is impossible to tell if you are or not! Ask the pioneers of sea exploration 200-300 years ago, they knew all about it.

Put succinctly, "free motion is impossible to detect" - the Principle of Relativity. This is where the word comes from - you have to be moving relative to something to tell that you ARE moving. THIS is the central tenet of Relativity.

What has the speed of light to do with this? Well, if true , there are certain consequences.

Einstein realised that the speed of light simply cannot be anything else BUT the speed of light, and that it was the same for all travellers, no matter how fast they travel. Otherwise they could work out how fast they were moving. For instance, if you are travelling towards another planet at 30,000 kph, the speed of light would be (speed of light (minus) 30,000 kph). SO you can calculate your speed. BUT the Principle of Relativity forbids this, therefore the speed of light is the same for them, as it is for us, here on Earth.

This principle has explained many things, a good example is a star going round another. Try to think what you would see if the speed of light were slowed down when the rotating star moved away, and what you would see when it was speeded up as it moved towards you. You would see the star in two places at once! This of course, does not happen, and is well explained by the constancy of the speed of light.

Another proof of the Principle of Relativity is in electromagnetism. Sometime back I was writing about the speed of light and electricity, and that it had actually been derived (logically deduced from) electricity and magnetism considerations alone. This also means it does not change.

Contrary to popular belief, light is not a barrier like sound is, it is more like a forcefield that grows stronger the nearer you get to it. Whereas sound barriers can be broken, it is physically impossible to go even as fast as light, let alone go faster.

When I say physically impossible, this is fact, because the harder you push to go faster, the energy you put in goes to increasing the mass (according to E = Mc**2), not to increasing the speed. Ask any particle physicist or nuclear scientist. BUT this is the realm of Special Relativity, and deserves another post, as does General Relativity. Both theories came about because of the simple tenet of the "Principle of Relativity".

From little acorns do mighty oak trees grow.

Harry Potter and the Order of the Phoenix

(VERY SUBJECTIVE POST!!)

Yes, here we go again.

As a dedicated fan of Harry Potter, I also await the new (and last) book "Harry Potter and the Deathly Hallows" with abated breath.

I STILL think that Sirius Black (Harry's Godfather, played by Gary Oldman) is alive. I have maintained it ever since he was apparently killed in the above episode.

I am also in love with HIM: (Harry Potter)





































AND desperately jealous of HER: (Cho Chang)

















Because she gets to do THIS:






















with him.....GRRRRR.

I can at least take solace in the fact that he seems to prefer the oriental type.

Maybe I can weave some of my own magic on HIM! Expelliamus!