Thoughts on the Universe

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Iceman

Iceman

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I just read a book by Isaac Asimov where he was talking about large numbers and how they related to the size of the universe. It got me to thinking, how can the universe really have a "size". Since space has no matter how can it end? And if it does end this must mean there is a new beginning. In either case the universe would never truly "end" but become something new or go on forever and ever. There is reasonable information that shows matter in the universe is getting farther apart and thus "expanding," but if it is expanding, are the limits of this universe getting bigger also? How can something that is in effect "nothing" get bigger? Maybe I am missing something here, but it just seems incomprehesible to me.
 
According to Douglas Adams, The answer to life, the universe, and everything is 42.

Google has proven it, as can be seen here

Anyways, to answer your question, I honestly don't understand this universe stuff. Once I start to understand one theory, something else comes up and I'm completely confused once again.
 
Hawking describes the universe as spherical in shape, expanding, yet with no barriers. I don't understand either.
 
here's a question - what exactly is it expanding into? We know that the universe is expanding but that probably means that something else is shrinking. What is that "something"?
 
Assuming the universe's age to be roughly 18.5 billion years, and assuming it is expanding equally in all directions at a constant rate of the speed of light (c), it can only be 18.5 billion light years in radius. This translates to a sphere 39 billion light years across and 26,521 billion cubic light years in volume. One light year is 5,881,464,000,000 (say it's 6000 billion) miles, so the universe is approximately 5.7 x 10 to the 45th power cubic miles in volume.

Each day the universe expands, uniformly given the assumptions above, by 16,113,600,000 miles (or one light day - call it 16 billion miles) in each direction, resulting in an increase of 5.8 x 10 to the 18th power cubic miles, or 21 million times the volume of the Earth.

Space does have matter. In fact it has rather a lot of it. But you are correct to say that, while there is categorically a size of the universe, there is no actual size of the universe. Space-time is curved. If it were possible to reach the "edge" of the universe, you'd probably find yourself coming back again without knowing it.


What it is expanding into is a rather nonsensical question. The universe IS everything. "Outside" the universe does not exist, therefore the universe is just expanding, not expanding into anything.


It is, of course, completely incomprehensible. Still, it's a good laugh watching people trying to work it out.
 
I don't. Because it doesn't actually make any sense at all.

If you were to understand the universe then you'd be, for want of a better word, God. But, since the Christian/Jewish/Islam definition of God fits nicely the definition of the universe you'd also BE the universe.

Hurrah!

Anyone who's found their brain melting at this point needn't worry. Go and have a cup of cocoa and a nice lie down. Or possibly a nice lie sideways.
 
The one thing I don't in the slightest bit understand is the concept of space-time itself – Is it an axis? And why does it curve? And how come that curvature would cause one to not be able to reach the "edge"?
 
One of the few theories about the universe modern science has created that I have understood is Einstein's gravitational theory that objects with mass "warp" the universe. Even with the basic understanding of this, I have never understood the 3 dimensional aspect of this warping and how an object passing into this warp is able to keep in orbit. I can see how an object path through space might be altered through this warp but not how it can continually orbit a mass. Famine, do you have any knowledge of reading material that might better explain this space-time you are speaking of? I've heard of it but never understood what it really meant. I guess all these theories and ideas about our universe can be summed up as human's never ending curiosity about why things are the way they are.
 
Imagine space-time as longitude/latitude lines on the planet Earth. The two are perpendicular to one another - and any given point can be described by referring to one, then the other. In fact, you can even lay it out flat on a single sheet of paper and, at all points, every line of longitude is precisely as far away from the previous one as it is to the next one.

But in fact the planet is curved and, although you perceive the lines of longitude as equidistant, they do in fact converge at the North and South Poles. If it wasn't for the fact that the North and South Poles are marked by a bunch of flags and a pole stuck into the Earth, you could carry on treading the same line of longitude right through the North (or South) Pole and down the other side. There is no actual "edge" of the longitude/latitude grid, it just converges in on itself.

Space-time is slightly more complex, in that it occurs in four dimensions*, not just two and a a half (by following lines of longitude/latitude, you perceive yourself as moving in two dimensions, but really it's three, technically four. But actually two, probably - or at least that's what gravity thinks). There'd be a West and East Pole too (there sort of is on Earth as well, at 90/0 and 90/180, but they're defined by perception and English map-makers) and a Pole at the centre of the Earth and all four dimensions would meet at all five poles.

I'm actually confusing myself now. It really is such a phenomenally difficult idea to conceptualise, and my analogy is more or less completely wrong, but it's about the only chance people as stupid as us could possibly have to begin to grasp it.

*Actually 11, at the last count
 
I love stuff like this.

If the Earth is round and the universe is round, how can it not expand into something ? A spherical object has edges, I cant get my head around something spherical with no edges as it surely cant be spherical if it doesnt have edges. So, if the universe is spherical in shapr their has to be edges, where are they and what is on the other side of them ??

This thread will stick for a while I think as this kind of stuff is amazing.

Sorry for going a little of topic but I always wonder how there can be nothing when you die - how can nothing exist and you be in it (or not as the case may be)
 
BigJamesGTI
I love stuff like this.

If the Earth is round and the universe is round, how can it not expand into something ? A spherical object has edges, I cant get my head around something spherical with no edges as it surely cant be spherical if it doesnt have edges. So, if the universe is spherical in shapr their has to be edges, where are they and what is on the other side of them ??

This thread will stick for a while I think as this kind of stuff is amazing.

Sorry for going a little of topic but I always wonder how there can be nothing when you die - how can nothing exist and you be in it (or not as the case may be)
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That's the thing. The universe isn't AN object at all. It IS spherical, probably, and has a defined volume, possibly, which is increasing at a given rate, perhaps. But it is everything so isn't expanding into anything - it is just expanding.

There is no "outside" of the universe, because the universe is everything. This is why it's not expanding into anything - there isn't anything outside for it to expand into because there is no outside.

Even more confusingly, while the volume of the universe may be expanding, perhaps, the total amount of matter and energy in it is not changing in any way - the first law of thermodynamics. So what the universe is remains constant.


Anticipating the next question, although time - and indeed space-time may have existed before the Big Bang (current theory is that the universe prior to the Big Bang was a pre-animate particle, less than 2cm across), nothing happened before the Universe created as, without the Universe there is no space-time and thus no time. "Before" becomes a completely nonsensical word.
 
That's just the thing about infinity and other such concepts (like the size of the Universe). Our minds can't comprehend how big it is. I have a limited understanding of it that allows me to post this gibberish:
if N =
allrealnumbers.gif

N / 0 = ∞
N / ∞ = 0
0 / 0 = N
∞ / 0 = N
∞ / ∞ = N
∞ = 0

There's a whole long string of these things, I could go on for hours but I won't...
 
Jpec07
That's just the thing about infinity and other such concepts (like the size of the Universe). Our minds can't comprehend how big it is. I have a limited understanding of it that allows me to post this gibberish:
if N =
allrealnumbers.gif

N / 0 = ∞
N / ∞ = 0
0 / 0 = N
∞ / 0 = N
∞ / ∞ = N
∞ = 0

There's a whole long string of these things, I could go on for hours but I won't...
Click to expand...
∞ is not a number. It simply signifies that something is unbounded.

You say that N is the set of all reals. How do you divide a set by a set? Last time I checked, the set operations were union, intersection, and complement.
 
You do it once for each number in the set on top for the first number in the bottom set, then repeat until all the numbers in the bottom set have been divided. The resulting numbers are your answer, simply put. And besides, nowhere does a set get divided by a set.
 
Technically, if no one has ever reached the "end" of the universe, and thus not had a chance to see what lies beyond, how do we know the end of our universe is the end of everything? What if you could poke a hole through the "end", as though it were an eggshell of sorts, and peer through, only to discover another world in which our universe exists inside a tiny molecule of, say, a blade of grass or a marble (like at the end of MIB)? What then? Huh? How many universes would exist? Could we develop a way to jump between th--

BOOM!

(Anderton just blew his own mind)
 
Heh, I love this stuff. It's all absolutely mind boggling. The whole idea of black holes and worm holes just blows my mind.

There's this program called Celestia, let's you "travel" through space. Neat.
 
Although I have read every single post in this thread, I have only one thing to say. Watch the end of Men in Black I, it will explain it all.

Oh, please continue, I love hearing other peoples ideas on this stuff.
 
@Famine What I don't understand is what could the other dimensions possibly be? What comes after time? THAT is what gets me...
 
Blake
@Famine What I don't understand is what could the other dimensions possibly be? What comes after time? THAT is what gets me...
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dont you just love the headaches thoughts like this cause? Especially when it's 1am and you know you have to wake up at 7 the next morning in order to be on time to a class where the entire lecture time will be spent on your laptop playing games and chatting on msn?

I do :)
 
Some random thought:

Voyager I, launched in 1979 - If my memory serves me correctly - and currently travelling through interstellar space at 13km/sec has only covered the equavalent of 25 light hours. Well, according to the JPL/Voyager website anyway. 25 light hours in over a quarter of a century! Feels small.

Also, I read in some physics book, that if you were an astronaut in space and possessed uber-powerful binoculars, you would be able to see the back of your own head. This is atributable to the effects of warped space time at the extremeties of the Universe.

Also, reaching the edge of the Universe is itself an impossibility. It is assumed to be expanding at the speed of light. So, even if Earthlings somehow got a spacecraft to achieve the speed of light as a travelling velocity (which we know is not possible), the edge of the Universe has had a 18.9 Billion year head start on us.

<end of randomness>

Oh, and great stats Famine 👍
 
I've been told it is possible to travel at the speed of light, can you explain why all those star wars movies are wrong?
 
Blake
I've been told it is possible to travel at the speed of light, can you explain why all those star wars movies are wrong?
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It is impossible. I can explain it to you, but it's too early in the morening and I have to get ready to school. basically, the amount of energy it takes to accelerate you closer and closer to the speed of light actually makes you more massive, so it then requires even more energy to go even faster. There is an equation that explains energy and mass relations (similar to E=MC²) that has a denominator in the equation somewhereof c-v (Speed of light minus your velocity). If you are travelling at c, then it would be c-c=0, and you can't have that, so It is mathematically impossible. :)
 
Well whom ever told you it is possible to travel at the speed of light is about as right as a left hand.

I cant remember the physics behind why it is impossible, but alternatively, consider this. The Cassini space prabe launched to Saturn in 1997 had the latest technology in rocketry, yet even then, its rockets werent powerful enough to push it to Saturn independently. Instead, the probe had to be "slung-shot" around Earth, Venus and Jupiter in order to obtain enough speed to reach the ringed planet.
 
It's not possible to travel at the speed of light.

But it IS possible, theoretically, to seem to the rest of the universe as if you ARE travelling at the speed of light. This is the Star Trek version - the engines create a "Warp Field" which warps (hence the name) the space around it so that there is more behind it than there is in front of it.

No positive rest-mass particle or object can generate enough energy to propel itself to 186,500 miles per second.

That said, it's only a speed - what do you think makes 186,499 miles per second possible and 186,501 miles per second impossible? :D
 
I watch a show about the universe. They had this guy that said we can travle much faster than the speed of light, by travling through time. Whatever the hell that means. He also said that traveling faster than the speed of light was still possible, but without the use of time travel. But, he meant for particles and signals, and not humans on this one.

On the same show they had the this guy that said the universe is pulsating much like a heart is beating. He said the universe will expand and then contract, and will do this for all of eternity.
 
Solid Lifters
On the same show they had the this guy that said the universe is pulsating much like a heart is beating. He said the universe will expand and then contract, and will do this for all of eternity.
Click to expand...

There are three theories regarding the expansion of the Universe.

1. Big Bang, Big Crunch. The Universe expands from the Big Bang until it reaches a critical size, then contracts again. Since the Universe, at 18.5 billion years old, is showing no signs of deceleration, this is unlikely.
2. Steady State. The Universe has always been here in its current state and will always persist. Since the Universe is expanding at a constant rate this is also unlikely, and points to a Big Bang event.
3. Big Bang... The Universe expands from the Big Bang and continues to do so. This is most likely, given the evidence above and the second law of Thermodynamics, which can be paraphrased as "The Universe tends towards chaos/entropy". If the Universe is forever expanding then, at some point, given that the total matter and energy in the Universe cannot change (the first law of Thermodynamics), the average amount of energy in the Universe will be nil. This is fairly incredible when you think about it, since to all intents and purposes the Universe is infinite and the energy and matter contained within it is thus also infinite. But the Universe is finite with a defined area and the amount of matter and energy within it is less than the area of the Universe and thus also finite. So the amount of an infinite yet finite resource spread out inside a finite yet infinite area gives an average of zero.


My head hurts.
 

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