Dekan

Well of course there's an actual difference in the wavelengths of light. No-one's disputing that. I'm saying that colours are a subjective impression which the wavelength differences give rise to in our brains! Gosh, this is hard work.

I think Wso is right, - Zeno's argument is invalid. Doesn't it mean that you can't get shot by a gun, if you're running away - the shell/bullet can never catch up with you?

You mean there are two kinds of electrons - one in virtual particle pairs, and the other in materials?

Don't you mean, we associate wavelength with colour? The wavelength is objective and actually exists. The colour is a mere subjective product of the visual processing bits of the human brain.

The OP, and the following replies, leads me to wonder this - can electrons really pop in and out of existence? Electrons seem to have a steady existence. You can see that when you use an electrical device, such as hoover or a computer. In these devices, the electric current works every time you switch on. The electrons are reliable. They flow smoothly and evenly through the wires,. They show no signs of capricious "popping in and out of existence". If they did, wouldn't our computers keep cutting out?

I suppose "texture" and "heat" can be said to objectively exist. Especially heat, which as Swanson says, is energy transfer. Such transfers make the Sun work, and if they didn't, we'd all be frozen to death. But colour - surely that's only a subjective impression. Generated by our human eyes and brains. Which have evolved to distinguish wavelengths into "colours" such as "RED" and "GREEN". But this distinction doesn't exist for a Daltonian, or indeed any blind person. So wasn't Galileo right at least about colour?

Well it's not a Universal constant then. It only applies to a vacuum. If it was truly a constant, it would apply everywhere. I mean suppose someone said - The diameter/circumference ratio of a circle is Pi. This is a constant - provided it's measured in a vacuum. But if it's measured in air or underwater, it may vary a bit.

As I already pointed out, light goes at different speeds, depending on the local medium it's travelling through. For example, Its speeds through air,water and glass are quite different. Isn't that hard to reconcile with the idea that light-speed is a Universal constant?

Just to add a point to the excellent posts by AJB and Swansont: The speed of light is a constant 299,792,458 mps in a vacuum. But when light passes through matter, such as air, or glass, or water, its speed can vary. This accounts for how glass lenses work. They slow light at a variable rate, according to the type of glass and how much it's curved. The slowed-down light is bent and converged to a focus, where an image is formed. This same principle applies to human eyes of course. Otherwise you wouldn't be looking at this!

Are you being wilfully obtuse? I'm saying that Newton's theory is a nuance, or subset, of Einstein's! Which is what you're saying! These Americans, they're great guys, but no wonder they don't do cryptic crosswords.

for EdEarl#15 Yes, accepted, which is why I thought it would be better put, that Newton discovered nuances of Einstein's theory, not the other way round!

Hm, Relativity is merely "nuances" that Newton hadn't discovered? Surely you can't defend that!

Up to about 1890, Physics was run by Newton's very rational Lawa. Then Einstein upset things, by bringing in eldritch new Laws, which physicists now use, with fingers crossed behind backs. Will there be any more Law changes, or is that it, do you think?

"Infinite" means "endless". And "Infinity" means "Endlessness", or going on without end. I think the trouble is that the word "Infinity" looks, to modern English-speakers who don't know Latin, like a noun for a specific thing. Like "Mile" or "Kilometre" But really it's just an abstract concept. Something that goes on "to infinity" just goes on endlessly - there's no "infinity" to be arrived at.

Hopefully your 99 year-old father-in-law doesn't need to rely on food stamps, as you're looking after him?

There weren't any food stamps in 19th century America. Everyone had to fend for themselves, without government handouts. No safety net. That's how the strong USA was created. Now the USA is being weakened by food stamps, which reward incompetence. And that will lead to the end of your country. Isn't that Darwinian reality?

Isn't Hydrogen amazing. It's just an electron orbiting a proton. Yet this simple combination has "chemical" and "physical" properties. The physical properties enable it to ignite the Sun, and create the Earth. And then on Earth, chemical properties enable it to combine with Oxygen, to make water. which provides the basis for life.

Like I said, it's numbers sorted into order. Thus 1,2,3,4,5,6,7,8,9 is maths. But 7,2,5,3,9,1,8,4,6, is only random numbers.

Why do some people in America need "food stamps". Surely they could get a job, earn some money, and buy their own food I mean, can anyone in 21st century America really be hungry, except through personal incompetence?

Maths is numbers sorted out?

I suppose we can always travel backwards in time, by using memory and records. And can't we change the laws of Physics, by using Relativity instead of Newtonian laws?

Thinking about your two protons, each shot at 0.999 light-speed from opposite ends of the LHC, to collide in the middle. Each proton "sees" the other approaching at only 0.999c. But that's an illusion. The combined speed must really be 0.999c + 0.999c. As is shown by the high-energy particles showering out from the collision. To prove this, suppose a proton were shot at 0.999c from one end of the LHC. It then collides with another proton which is static - held in suspension as part of a water droplet or something. Each proton will still "see" the other approaching at 0.999c, as before. But will the collision give the same results?

Thanks John and jduff. Your posts show how programming has changed since my time, back in the 1980's. In those days, I used Sinclair Basic. That was very simple, and required only thinking step by step, logically, to write a program. And it was easy to learn - it had a syntax-checker, which wouldn't allow a wrong line to be entered. I still think that was a good way to teach programming. These days we have modern languages like C++. But doesn't C make you declare all variables in advance? That's quite annoying. It's not like Basic, where you can make up a variable as needed, when you want, "on the hoof" without having to go right back to the start and "declare" it. I suppose the "declaring" is necessary because C is designed to be compiled into machine code. And compilation is much easier if all the variables are known at the start, rather than suddenly popping up. But the requirements of a compiler shouldn't interfere with human freedom. Why should we comply with the machine? Basic isn't intended to be compiled, so it gives the programmer complete freedom to create variables as needed. It's a very nice logical language to work with.

I suppose we all know who's clever and who's stupid, you can tell the difference as soon as you meet them.