Ever wonder why?

[Nick]

Ever wonder why the sky is blue or the sea green?

I thought it'd be a bit of fun, as well as educational, to ask these questions.

The idea is, someone asks a question, then others go off to find an answer. Once its done, the next question can be asked.

To make it more fun, how about we try it with no links to other pages... copying and pasting is ok, but linking to a whole page or site is out.

So, first question.

What is the maximum theoretical speed of a silicon based CPU, and what limits it?

[TiG]

To be honest you are asking the wrong question as it is not the silicon that is the problem, well it is and it isn't..... let me explain what i know...

Silicon CPU's are made by a process of "putting" tracks on the silicon, the increase in speed is down to how small they can make the tracks, currently mainly .13 Micron, thats 1.3*10^-7 i.e bloody tiny.

They are already working on .09 micron and this won't be a problem, but from what i understand you start getting problems here as what you can get is that electrons get rather frisky when you get tracks closer together and you could find that they could jump to places they shouldn't be going etc....

To do this you need ensure the silicion is as pure as you can make it, which obviously increases costs etc, so the answer is dependant on A) how small they can lay the tracks and B) how pure they can make the silicion to stop the CPU being worthless if electrons can jump tracks....

All of the above HAS NO bearing on the way the CPU will perform tho, all it means is that it could run cooler, therefore be overclocked more. The clever stuff comes with the CPU designers, and for CPU's inside computers they are made pretty generic to be honest, NO special sets of processors like GPU's to do just graphics transforms etc.

If you want something to do a specific set of tasks then its easy to make a CPU much more designed for it, otherwise as people get to understand more about what you can do with CPU's the more complicated the design.

If you want a quantum leap forward in CPU speed, then you need to use quantum based CPU's, but then maybe that should be your next question Deckard

TiG

[silent ben]

edit: being stupid

[Nick]

lol TiG... nope, I'm not asking the next question... someone else can have a go.. although I DO have a couple of juicy ones I'll save for later!

[TomWilko]

Ok, i have a question...not being a space person i sometimes think about this:

Whats the fastest a human has been in space? And why can't we go any faster??

[Ceryndrion]

During re-entry the US Space Shuttle flew at a record 16,000 mph (7153 m/s).

If this is taken as being the fastest any human has gone, then the reason that we cannot go faster, becomes a factor of gravitational pull and engine thrust, with gravitational pull being almost constant, it can be factored out, leaving the thrust of the shuttles own engines, these are limited by size, fuel and of course, the incediary properties of the fuel.

[Tumble]

think the figure is more like 18,000 odd, on an Apollo re-entry... think it was Apollo 8, when they went round the moon but didn't land, and were on the maximum energy return orbit or something....

EDIT: Just looked into it.. it's actually a lot higher....


New world speed record: 24,200 mph (38,938 km/hr).

[Ceryndrion]

okay ..

The J-2 engine increases Apollo 11's speed to 24,182 mph, easing it out of the earth parking orbit and on towards the moon.

Incidentally, to fully escape the earths gravitational pull you have to be going, slightly above 25,000mph (40,000kmph)

[Russ]

depending on your angle of attack...

[Tumble]

okay ..

The J-2 engine increases Apollo 11's speed to 24,182 mph, easing it out of the earth parking orbit and on towards the moon.

Incidentally, to fully escape the earths gravitational pull you have to be going, slightly above 25,000mph (40,000kmph)

ACTUALLY.... pure speed doesn't really come into it... If you're a rocket, sitting on the launch pad, relative to the bit of space you want to get to, you're still zipping along at a fair old rate... the Earth is roughly 40,076 km round its middle... takes 24 hours to rotate completely so a given point on the surface can be said to be travelling through space at around 1600 km/h already.. what you are trying to do is get out of the gravity well, not go faster than the planet - you can do that by walking west. No, what you need to do is ACCELERATE faster than the planet... everything is drawn to the planet's centre at a constant rate of 9.81 metres per second per second... so for every second you fall, you go 9.81 m/s faster until terminal velocity is reached. So to escape into orbit, you need to accelerate faster than 9.81 m/s/s for quite a long while... which has the effect of making you go awfully fast relative to the earth. The bit where the J2 boosts the Apollo spacecraft onto it's track to the moon is again, overcoming the 9.81 m/s/s acceleration the Earth is exerting on the spacecraft, but seeing as the ship is moving at better than 10,000 km/h anyway, it goes faster, and the speed it reaches depends entirely on the length of the burn..

[Nick]

riiight... so I understood that lot...

And the next question is....

Why does the Moon look massive when it's low on the horizon?

[GreenPiggy]

It's an optical illusion. Objects always look bigger when you have reference objects in the same line of sight.

[Nick]

Yeah, I can see that... but how come I can see so much more detail sometimes... normally its just there with a few mottled bits on it and thats about it. Sometimes though, I can see individual craters, shadows, the whole shooting match... how's that?

[GreenPiggy]

hmm, can't answer that. Could be something to do with the glare of the sky obscuring the view perhaps

[Tumble]

it's to do with the earth being round.... the atmosphere acts like a lens, and magnifies the image. It's the same reason that sunlight is red when the sun's on the horizon... called REFRACTION. Basically cos you're looking at the moon/sun through lots more material, air, dust, whatever, when it's on the horizon than you are when it's directly overhead.

[GreenPiggy]

Thats not true, The differential refraction on the horizon actually acts to flatten the moon slightly and would not produce a magnified image.
The sunlight appearing red is nothing to do with refraction, it's the remainder of the light that hasn't been Rayleigh scattered. White light - the Blue light. Same reason the moon is orange during a lunar eclipse.