PDA

View Full Version : how big is the universe?



elizabeth25
2011-Feb-09, 01:39 PM
i recently read on another forum someones view on how big the universe is. here is what it says.

''I thought if the universe is 14 billion years old....and we measured the speed of light at 186,000 miles per second! Wouldn't all we need to find out is how far light traveled in that time frame? So I looked up and found how many seconds are in a year and it came out to be 31,556,926 seconds in 1 year. I took that number and multiplied it by 14 billion to get the age of the universe in seconds and it came out to be 441,796,964,000,000,000 seconds in the universe. Now my first thought was no way...its got to be more??
But anyway I continued my math. I took that number which represents the age of the universe in second and multiplied it by the speed of light and I got this super big number 82,174,235,304,000,000,000,000 and that would be the distance light traveled sense the Big Bang in 1 direction. Then I figured all you would have to do to get the universes total Diameter only would be to multiply that number by 2. And you get the whole diameter of the universe which comes out to be 1.6438471*10 to the 23rd power. Or this very long number. 164,348,470,608,000,000,000,000 miles in the universe.''

now im not saying that this is wrong, im not very good with math to this level. but i always thought that the universe is never ending, i constantly have this argument with people i know and they say that the universe does end, and im thinking.. HOW? i dont believe that there is an edge to space. just imagine we had the ability to travel far distances, we wont go crashing into a wall, will we? :think:

Strange
2011-Feb-09, 04:54 PM
I haven't gone through the numbers to see if they are correct. But there are some caveats. The observable universe is larger than calculated like that because it has carried on expanding since the light left the most distant thing we can see. Also, the distant parts of the universe are expanding fast than the speed of light (from our perpective). But we don't know how much bigger the whole universe is than the bit we can see. It may be infinite it may not. We will probably never know.

But this might be of interest: http://www.universetoday.com/83167/universe-could-be-250-times-bigger-than-what-is-observable/ (recently posted in another thread).

Phylomon
2011-Feb-09, 04:57 PM
Nobody knows if the universe ends or not. There is some serious speculation that it curves back around on itself. For example, if you started walking East, you would eventually circumnavigate the globe (ignoring large bodies of water, of course) and return to your starting point. The earth is finite, but doesn't have any edges or walls to run into. We believe the universe has been around for at least 14 billion years or so, but that doesn't mean that there's not something beyond 14 billion light years, it just means that we can't detect it (yet).

Hope this helps.

Jerry
2011-Feb-09, 09:30 PM
The reality is, we can only place a minimum age on the universe, based upon some pretty broad assumptions. We can put a theoretical cap on, too; but since our most distant observations don't detect drastic changes (yet); that lid could easily pop off with the first light of the JWT.

LotusExcelle
2011-Feb-09, 09:35 PM
This should answer it directly:
Space is big. You just won't believe how vastly, hugely, mind-bogglingly big it is. I mean, you may think it's a long way down the road to the drug store, but that's just peanuts to space. Douglas Adams

whatdoctor
2011-Feb-10, 04:18 AM
The numbers become a bit more readable if you use light years as your unit of distance (a light year is a distance - not a time). So, in theory we are 15 billion light years from the centre of the Universe - making it about 30 billion light years across. Current theory is that the Universe is expanding in all directions at the speed of light - so we are basically on the outer rim. What we see when we look back into the middle is stuff that was there years ago - but has since moved out. What is beyond our sphere? I think the theory goes something like this: Space is created by matter. Beyond the matter, space has not yet been created. I don't fully understand that theory - I think it involves some complicated maths. I also currently believe that we are in recursive big bangs - which sort of puts a big hole in everything and makes the Universe infinite again - but we will never be able to detect anything outside out own big bang existence so it is sort of irrelevant.

Shaula
2011-Feb-10, 07:56 AM
@Whatdoctor
Uh? Lot of non-mainstream there...
The universe is not all expanding at the speed of light. Nearer to us it is slower than this, further away it is faster (and ends up faster then the speed of light from our frame of reference).
How does it expanding like that imply we are on the rim? Observationally we seem to be in the centre (which is one of the reasons why expansion of space is a better answer than stuff just flying apart)
Beyond our sphere is just more space. Matter doesn't create it according to current theory. As you go further out all you see is more of the same.
There is no strong evidence for recursive big bangs.

Ivan Viehoff
2011-Feb-10, 01:45 PM
Basically you calculated how many miles is 14 billion light years. Would have been quicker to look up on wikipedia how many miles is a light year, etc.

This article from Scientific American on universe expansion might be useful. It suggests the observable universe has a radius of about 46 bn light years. http://www.mso.anu.edu.au/~charley/papers/LineweaverDavisSciAm.pdf

elizabeth25
2011-Feb-10, 02:06 PM
Ivan i didnt calculate it, i simply read it on another site's forum, and thought id share it on here to see what everyone thinks about it, like i said im not very good with math to that standard so i wouldn't know if it is right.

Trakar
2011-Feb-10, 10:55 PM
This should answer it directly:
Space is big. You just won't believe how vastly, hugely, mind-bogglingly big it is. I mean, you may think it's a long way down the road to the drug store, but that's just peanuts to space. Douglas Adams

Actually, due to inflation, it is not just "biggest," it is actually "biggester!" (and I guess when you clarify that this includes - Uni = 1 - all parallel aspects and dimensionalities it might even be "biggestest.").
:)

Infinitenight2093
2011-Feb-10, 11:14 PM
i recently read on another forum someones view on how big the universe is. here is what it says.

''I thought if the universe is 14 billion years old....and we measured the speed of light at 186,000 miles per second! Wouldn't all we need to find out is how far light traveled in that time frame? So I looked up and found how many seconds are in a year and it came out to be 31,556,926 seconds in 1 year. I took that number and multiplied it by 14 billion to get the age of the universe in seconds and it came out to be 441,796,964,000,000,000 seconds in the universe. Now my first thought was no way...its got to be more??
But anyway I continued my math. I took that number which represents the age of the universe in second and multiplied it by the speed of light and I got this super big number 82,174,235,304,000,000,000,000 and that would be the distance light traveled sense the Big Bang in 1 direction. Then I figured all you would have to do to get the universes total Diameter only would be to multiply that number by 2. And you get the whole diameter of the universe which comes out to be 1.6438471*10 to the 23rd power. Or this very long number. 164,348,470,608,000,000,000,000 miles in the universe.''

now im not saying that this is wrong, im not very good with math to this level. but i always thought that the universe is never ending, i constantly have this argument with people i know and they say that the universe does end, and im thinking.. HOW? i dont believe that there is an edge to space. just imagine we had the ability to travel far distances, we wont go crashing into a wall, will we? :think:

your probably right, there is no wall. your perception of what the "edge" really means might need a tweak though, because there really is no edge to the universe, at least to those of use incapable of traveling faster than light. The technical limit of our universe is the boundary in which space is expanding faster than the speed of light, therefor trapping us within the more hospitable conditions, those being our universe 46 billion LY in radius.

as a side note, infinity can be thought of the same way. it was said here once before that infinity is not a number or a size. what this means to me is that our universe is infinite simply because we will never reach the end.

astromark
2011-Feb-10, 11:52 PM
Douglas Adams was right... IT, meaning the Universe is very, very big. It is after all, all of everything...
and that the fact that it is expanding at a ever faster rate makes ever reaching a location remotely resembling the edge is just never going to be possible. IT is rushing off ahead of you faster than you can go. End of problem...
So the glib style of Douglas Adams has proven to be right again... "Mind bogglingly big."