h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

Pardon me for disagreeing with you (just a bit) Hiram Abif. It's not that I know anything whatever about the big bang but I must say I have a preference for short sentences, especially when reading a difficult subject. I find this kind of subject quite taxing, so small, 'digestible bites' make it easier for me to absorb.

Regarding the point about people believing the world to be flat: I read somewhere that was a common misconception and that even very ancient peoples could tell the world was round. They could tell from the horizon. Still, some people believe some pretty peculiar and unlikely things, so who knows

I appreciate the input and will update the spelling, capitalization etc. I do however disagree with the Axiom that Time and Space are quantities. I consider them dimensions.

cosmologists also consider space and time to be dimensions (in fact a four dimentional space-time, which can not be reduced further without causing serious problems with theory).

As regards the point a few posts ago, about not knowing if stuff works the same elsewhere, science itself (and cosmology in particular) take a great deal of care not to presume on the specialness of where you happen to be.

The ancient greeks (aristarcos I think) discovered the roundness of the world using midday shadows being different in different places, and managed to measure how big the world was to within a small fraction of the current value.

You then prove that stuff works the same out there by using observational science to collect data, which you compare against current theory. if the theory is found not to fit, you try and modify it so that it does fit, which will make it produce predictions which you can check (either experimentally, or observationally). you also cross-check various sciences against each other to make sure that you are not predicting the imposible (like presuming c to have a larger value).

This is called the scientific method, and has worked fairly well for hundreds of years.

an interesting point, latest theories which don't like antigravity try replacing it with a constant speed of light which varies over time.

strange!

What, mathematically speaking, is a dimension? It is a quantity is it not? If you tell the "dimensions" of something you are generally giving a quantity of the three dimensions of space.. when you tell the date and time of right now, or some other time, you are giving a quantity in the one way (for us) dimension of time.... The more things you give quantities for, the more dimensions there are...in a mathematical sense...but if cosmology isn't math then what is it? You say the universe was so big at such and such time and had temperature X and its been going on about this long and the wavelengths are just so... It is nothing but quantities.....

the first BBC link has this definition:
"theory about,or study of, the origin or nature of the Universe.
look at it this way- If the universe were a bag of apples
studying how many apples in the bag would deal in quantities,however
studying the bag itself would not; as the apples have a quantity, but the he bag is not a quantity,and stdying the bag is not studying a quantity. You say the bag is red. you say it is porous. you are studying the bag. you are not studying quantities.

An interesting sidenote. If you make the unit of measure the right size the quantity can be what ever you choose, so with the proper unit of measure the size of the universe is 42.

but the relationships between the quanities are much more interesting.

also, a universe with the size 42 would be very hard to talk about, what with all those zero's after the decimal point before you get to the interesting bit of the quantity's.

I have yet to see any talk of the color or permeability of the universe, that might be interesting... What I have seen is talk about the age, size, amount of matter and/or energy, rate of expansion, temperature, etc... all of these are nothing more than quantities...

In my original post, I did begin to talk about possibilities for the fabric of the universe, and welcome any other theories about the nature of reality...I would love to talk about the "bag", but that isn't what has been happening...

You say "A dimension is not a quantity" OK, I would also love to hear any alternate definitions of the word "dimension". When you say it, what exactly are you refering to?

On another note...the Hindu creation myth has quite a few similarities to Big Bang theory... any comments on that?

According to the Encarta online World Dictionary of English:

di.men.sion 1. measurement of the size of something
2. size
3. aspect
4. lifelike qulity
5. level of reality
6. "MATHEMATICS" coordinate for space and time
7. "PHYSICS" property defining physical quantity


I rest my case

a fairly strong case. I was just checking the Handbook of chemistry and Physics. It lists the fundamental quantities as mass ,length,time, temperature, dielectric constant of a vacuum, and magnetic permeability of a vacuum. As I am trying to keep the language of my article simple( and don't know much about dielectric constants anyway) I think I'll keep the article te way it is.
As to creation myths. That is something I'll give some thought to, but not right now.

Sorry Shagbark. I forgot to say: singularity definition

I thought my footnote defined the singularity. It is only here in peer review that we are discussing the definition of dimensions.
By the way I read your note on the home page thread. always read your posts.

I liked this article. Before I read it, I was worried it may be filled with masses of hypothetical conjecture that would date quickly, but actually it strikes just the the right balance for me at any rate.

'If the critical density is exceeded then the rate of expansion will increase' needs a revisit perhaps.

Regarding alternative theories and extraneous detail, I'd make use of Occam's Razor whereever possible. By all means mention in the introductory paragraph that, there are possible alternative (but unnamed) points of view, but remember that the article is about the Big Bang theory, nothing else. Let other researches write articles on 'Tim the Magician did it' or whatever.

I'm not sure why this talk of dimensions got on to the thread. If your dimension relates to a quantitative parameter (eg dielectric constant), then the dimension has an axis of quantity. But if the parameter is qualitative (eg existence) then it doesn't. Such artifice abounds in set theory, quantum theory etc, but a couple of examples of dimensions necessary to define (holistically) everyday subjects :

Beethoven's Pastoral Symphony has a lyrical dimension.

My car has dimensions of Westminster Blue exterior and broken exhaust.

It's irrelevant. The tone of the aricle is fine.

Well spotted Wilfrid, 'If the critical density is exceeded then the rate of expansion will increase' is bad. This may be partly my fault so I'll try to explain.

There are three possible scenarios:

1. The closed universe, has a density greater than the critical density. The gravitational attraction dominates. The universe expands to a maximum size then collapses back on itself.

2. The flat universe, has a density equal to the critical density. The expansion of the universe is exactly balanced by the gravitational attraction. It will expand forever, but at an ever slowing rate so that infinitely far into the future, the rate of expansion will be zero.

3. The open universe, with density less than the critical density. The expansion of the universe is so great it will never be brought to a halt, it will continue expanding forever at a non-zero (but still decreasing) rate. Infinitely far into the future, the universe expands to an infinite size.

In all three cases the rate of expansion of the universe is decreasing. The vast majority of current theoretical and experimental evidence suggest we live in universe scenario 2. The flat universe.


But, recent measurements of the redshift of distant supernovae show that the expansion of the universe appears to be accelerating. This is not the case in any of the three models above. This suggests that the universe is more complicated than previously thought, there may be more forces at work. Qunitessence or dark energy, vacuum energy and non-zero cosmological constants.
However this final point is rather speculative, and really needs a guide entry of its own to be properly explained. I suggest you don't mention this in the Big Bang entry.

Apart from this the entry looks pretty good now.

MP

Sorry Shagbark, I'm not sure what you mean. I was just saying I liked your singularity definition.

Editorial Note: This conversation has been moved from 'Peer Review' to 'The Big Bang'.

This thread has been moved out of the Peer Review Forum because your entry has now been recommended for the Edited Guide.

You can find out what will happen to your entry here: http://www.h2g2.com/SubEditors-Process

Congratulations!

Congratulations!

Thanks for a great entry!


:x

Hi folks,

I dropped in to tell you that I've been given this fabulous entry to subedit.

The first draft of this is finished and is located at http://www.bbc.co.uk/h2g2/guide/A653230, if you like to have a look. If there's something that has still to be corrected or if you see something you'd like to comment upon, please drop me a note.

SchrEck Inc.