Universe book of records

[ChromeStar]

Hi guys :D

i opened this thread because i've wondering up some of the limits of the universe and everything in it. i want to start with: How Dense can something be - can you sqeeze the gravity of the earth, for example into an area of a space ship floor i.e. the shuttle

[downunder]

The maximum density that can be calculated from universal constants is 9.85*10^96 Kgm/cub metre. This is the density of a Planck mass within a sphere one Planck length in diameter. It's also a black hole :)

[StarLab]

There are no "limits." There are maximums and boundaries that can be crossed if only we tried. Aside from large densities, high temperature is one of them. And, all the Planck values (at the Planck scale) are actually the "root" limits.

[ChromeStar]

Do any of yopu read popular mechanics?, the one in South Africa has a page dedicated the Limits of the Universe by the same name as this thread.

it discusses limits of light, heat, and things like Quantum tunneling.

[ferg.c.]

As far as I can tell Limits to actual physical things like density, speed, size etc. are really representations of the limits of our ability to describe them or comprehend them.
What do I mean?
Well you can say that nothing can be denser than Plank's mass times Plank's length, but this is not so. We cannot measure (I don't mean physically measure but "calculate the reality" perhaps) a density higher than this but it does not mean that it cannot be reached. I was discussing this morning the limits of size and I explained it in this way: Imagine a ruler which you can measure planks length and it looks like it's about six inches. Then you look to see what happens when you cut this in two. It still looks like six inches because we have no concept of any thing smaller. We know that it's half the size because we cut it in half but it didn't get any smaller! It is already infinitely small! The same goes for the speed of light, c. You can add 100km/h to c and it's still only c! it's already infinitely fast! You can write c+100km/h and think what it might be like and write equations and calculate phenomena based on this new speed which exceeds c but they will make no sense because when you do the experiment the speed was not this new speed but only just c! Like looking at the ruler and seeing six inches again.
This is why we should never ban philosophy from this site, Frazer!
Cheers
Ferg B)

[ChromeStar]

I 've just bought Popular mechanics January 2005 and in chapter 12 of there Universe book of records they discusss the limits of knowlage. i'm going to try find a link.

[downunder]

Originally posted by ferg.c.@Jan 11 2005, 12:16 PM
As far as I can tell Limits to actual physical things like density, speed, size etc. are really representations of the limits of our ability to describe them or comprehend them.

Not really, the limits are imposed on the universe by its own constants. In the case of the Planck length you take 3 constants, c (speed of light), G (gravitational constant) and h (the Planck constant divided by 2pi, or h(bar) as it's called). Then you combine them in an equation that goes like this... square root(Gh/c^3)...and the answer comes out with the units of length which is 1.6*10^-35 metres. If you want a length shorter than this then you have to change at least one of the constants and then the universe would work rather differently to what it does now.

We of course can conceive of half a Planck length but that doesn't mean it's physically possible to have one.

[ChromeStar]

Couldn't find a link so i typed it out. :blink: ;)

The Universe Book of Records
Part 12 the limits of Knowledge
by Christopher Backeberg

A hundred year ago, it seemed to many that the quest for scientific knowledge
Was nearly at an end. The Universe was ruled by the unfailing laws of science built upon the work of Isaac Newton.

Every event in the Universe was ultimately predictable and could eventually be calculated.
Everything that could be known would soon be known. Or so it seemed at the beginning of the 20th centaury.

Then Einstein reinvented physics. Suddenly we faced with a universe that was no longer Uniform on the largest scale, or continuous at the subatomic level. Newton’s “clockwork Universe” gave way to cosmos where the most fundamental processes are decided by probability and uncertainty.
Nothing therefore could be deterministic.

Science at first grudgingly acknowledged that there were some things we could never know. Mathematics jumped in boots and all, with the suggestion that perhaps we could never know anything completely.

What, then, are the limits of knowledge? How much can we still build on our present understanding of the greatest and smallest limits of the universe?
We need to consider only history altering discoveries to know how little we will ever know.

The Incompleteness theorem. In 1931, a Czech mathematician, Kurt Godel, Published his devastating blow to the quest for ultimate knowledge. His Incompleteness theorem states very simply that no branch of any system of mathematics can ever be complete because it will always have more axioms then the mathematical system can prove.

It may be possible to develop a higher system of mathematics to prove that everything is true in the initial system, but the higher system would suffer from the same problem of incomplete proofs within it’s self. To fix this you would have to develop a still higher system to mathematics, and so on to infinity.

Godel’s theorem isn’t just a highbrow academic diversion. It could have a profound influence on our future. One implication is that we may never be able to develop artificial intelligence. Say goodbye to Hal 9000 intelligent computer, Robbie the robot R2D2 and all of those clever devices it may be possible to invent.

The Uncertainty Principle. Werner Heisenberg, who later worked on the Nazis Nuclear weapons project during world war two, proved that it is impossible to know precisely what is happening at the subatomic level.
In it’s basic form, this law of quantum physics states that it’s impossible to determine both the position and the momentum of an electron. The principle extends to other particles as well.

If this doesn’t sound particularly startling, imagine what it would be like if the Universe behaved in this way at the macroscopic scale of human beings and motorcars.

If a traffic cop were then to measure the speed of your souped-up VW beetle at 160km/h on the road between Durban and Johannesburg, there would be at least some probability that your VW wasn’t on the road at all, and could be anywhere between Kwa-Zulu Natal and the Moon. If, on the other hand the cop could determine with certainty that you were speeding through a trap exactly 20 km outside warden, there then be some probability that your VW
Was travelling at anything between a snails crawl and 360 000km/h.

At a practical level, the uncertainty principle makes it impossible to know exactly when any particular atom in a radioactive substance will decay, or in what order. It is impossible to balance a sharp pencil forever on it’s point because the exact position of its atoms at the tip of the point, and also the exact position of the pencil’s centre of gravity, cannot be known – there location is sort of fuzzy.

If you move a set of molecules from place A to place B you can never know if they’ll arrive there in exactly the same arrangement you had when you started moving them.

The future implications of heisenburg’s work may be discouraging. It’s greatly unlikely that we’ll ever be able to build matter transmitters (“beam me up, Scotty!”) to send cousin Fred from Cape Town to Bloemfontein in the blink of an eye. He may well arrive, but he would probably reach his destination as a disorganized clump of organic matter. Time travel looks equally unlikely because the information we send into the future or the past would be garbled when it arrived.

The Hubble Constant. Based on observations by American astronomer Edwin Hubble, this is a measure of the rate at which the universe is expanding. Recent discoveries suggest that the rate of expansion is increasing. The Hubble constant has not yet been established with convincing accuracy. One consequence of the expansion of space itself is that everything beyond a certain distance is moving away from us faster then the speed of light.

Space can expand faster then the speed of light but information can’t travel faster then light in a vacuum. Nor can physical objects. So we can never know what is happening in the Universe beyond the observable region of the Universe, and we can never reach the more distant part of it.

Chaos theory. At first it may seem paradoxical that scientists and mathematicians have based a whole area of chaotic, unpredictable systems.
There work has been greatly revealing, however. Chaos theory extends human knowledge by revealing there is a often a larger pattern of order is underlying the outward disorder of, say, the turbulent flow of water in a river.
At the same time, chaos theory has left no doubt that it is impossible ever to fully predict an inherently chaotic outcome.

Chaotic systems have several elements in common. One is that the tiniest change in the initial conditions can cause massive differences in the final outcome; you’ve heard the exaggerated story of how a butterfly flapping it’s wings in China can effect the weather in Mexico. Another common factor is that the line of mathematics of chaos usually involves a matrix of non-linear equations – a set of equations that cannot have an exact solution. The best we can hope for is a good approximation.

Most of the complex events and behaviours we encounter in everyday life are non-linear, chaotic processes. Weather forecasting is one such process.
If you have 1000 weather stations making local measurements to an accuracy of 3 decimal places, the forecast may be approximately accurate, but never exact.

If you increase the number of stations to 1 000 000 and the accuracy is to 10 decimal places, the forecast may be approximately more accurate, but still never exact.

Scientists – and educated others – know that they can never make 100 accurate predictions about the diffusion gases in a rocket exhaust, the speed of an epidemic, the shape of a tree when it grows or the psychology of the human mind. Oh yes, and think before you put your money down, because economic and stock predictions are also chaotic.

Short-sighted scientists were not only humbled, but also dismayed when they realized it was impossible to ever no everything. The more imaginative among them – and the same educated other we referred to earlier – were inspired by this fact. It means the scientific quest never has to end because the Universe will always have something new to reveal to us.

Cynics have asked what purpose science may ultimately serve if it admits there are universal limits to knowledge. There are two sensible responses to this type of criticism. The first is that any addition to the fund of human knowledge should be welcomed. And the second is that if science can’t answer all the questions, then surely nothing else can.

SOURCE:

Popular Mechanics, January 2005, South African Addition

I know it's long, but it really good hope you enjoy :D

[ChromeStar]

Any thoughts?