alien life possibility is pathetic

[Jaxe]

That's actually wrong, according to modern cosmological theory.

But isn't that more a matter of definition? Where the universe, as I understand it, is now defined as where there is any matter, and wouldn't that mean that you could indefinitly expand the universe by extending beyond the border of the current edge of the universe?

Theoreticly speaking you could travel beyond the edge of the universe, but since you're matter you wouldnt ever be outside it, just uh, expanding it?

 

[Lonewulf]

But isn't that more a matter of definition? Where the universe, as I understand it, is now defined as where there is any matter, and wouldn't that mean that you could indefinitly expand the universe by extending beyond the border of the current edge of the universe?

Theoreticly speaking you could travel beyond the edge of the universe, but since you're matter you wouldnt ever be outside it, just uh, expanding it?

The definition of the universe, as far as I know it, is wherever there is space (not necessarily matter), and the matter can only exist inside the space (and cannot travel outside it). The problem is (correct me if I'm wrong), the Big Bang *created* Space/Time, which expands.

There's a few theories, but the common one now (I may be wrong), is that if you traveled beyond the edge of the universe, you'd just end up on the other side, much as if you would if you ran around the globe. This has to do with the universe having four physical dimensions, and we can only see into the third (much like a 2-dimensional creature couldn't really perceive us as anything but a shadow of ourselves).

Keep in mind, I'm relying entirely on my own self studies, and an Introduction to Astronomy course at Del Mar College.

 

[dirtygreek]

You guys can go after kooks and woos and religious nutters all you like, but watch what you say about Douglas Adams

 

[Jaxe]

The definition of the universe, as far as I know it, is wherever there is space (not necessarily matter), and the matter can only exist inside the space (and cannot travel outside it). The problem is (correct me if I'm wrong), the Big Bang *created* Space/Time, which expands.

There's a few theories, but the common one now (I may be wrong), is that if you traveled beyond the edge of the universe, you'd just end up on the other side, much as if you would if you ran around the globe. This has to do with the universe having four physical dimensions, and we can only see into the third (much like a 2-dimensional creature couldn't really perceive us as anything but a shadow of ourselves).

Keep in mind, I'm relying entirely on my own self studies, and an Introduction to Astronomy course at Del Mar College.

Ah, that's the bubble universe theory, isn't it? I believe it had to do with more dimensions than just 4 though... Damn, off to study again, and here i thought i was going to have a nice evening lurking around as usual.

(who am i kidding, i love it )

 

[Cuddles]

c4, I too get dismayed when scientists say things like "there's no water there, so there couldn't be life." I've heard it said so many times on The Discovery Channel that it makes me want to throw things. Not that I'm hugely optimistic about the existence of alien life, though I bet it exists in some form somewhere, but yeah, I'm confused as to why people think that way too.

This really comes down to what Lonewulf said about resources. I also get annoyed when people say things like that, but generally what they mean is "There's no matter, so there couldn't be life as we know it.". As has been pointed out several times in this thread, all we know for sure about life is that it can exist and that it's happened at least once. We can speculate about possible other forms of life and where they might be able to occur, but the only type we know can exist is made of carbon and needs water. Given the needle in a needle-stack nature of the search for any life, it makes sense to focus on that which we know is at least possible, rather than waste time and resources speculating about things which not only may not be possible, but which we may not recognise even if they were.

Now, as for being carbon-based, that I can understand more clearly. Still, I don't think it should be seen as a 100% necessity.

The argument for carbon based life is one of the stronger areas of speculation about alien life. The problem is that life needs a large amount of variability, and carbon is the only element that can really provide it. Silicon can form long chains but they tend to be fairly boring repetitions, with anything more complex being unstable. Other than that, we don't know of any other way of forming large, complex molecules.

On the other hand, as far as I know this isn't really something anyone worries about. Carbon isn't all that uncommon. Finding more complex organic molecules may be something to get excited about, but the presence of carbon in any solar system can be pretty much taken for granted. Scientist might hail the discovery of the spectrum of water around a star as promising for the possibility of life, but I've never heard of anyone citing a lack of carbon as a reason to be pessemistic about it.

But isn't that more a matter of definition? Where the universe, as I understand it, is now defined as where there is any matter, and wouldn't that mean that you could indefinitly expand the universe by extending beyond the border of the current edge of the universe?

Theoreticly speaking you could travel beyond the edge of the universe, but since you're matter you wouldnt ever be outside it, just uh, expanding it?

No. There is no such thing as "outside the universe". It's not matter that's expanding, it's space itself.

I should note, howver, that not all theories say the universe is finite, and our observations are not yet good enough to tell for sure. The universe is certainly much larger than the observable universe, but beyond that we're just not sure.

 

[Lonewulf]

But of course, if the universe was infinite with an infinite amount of matter -- including stars -- then that would make one wonder why we don't see an infinite amount of light in the sky?

But if space WERE infinite, outside of where matter is... what is space expanding into, then?

 

[Lonewulf]

You guys can go after kooks and woos and religious nutters all you like, but watch what you say about Douglas Adams

He was a brilliant writer of comedy?

I hate to say it, but his books weren't exactly about total accuracy of present-day theories.

I wouldn't give his work up for all the money in the world. But going off him for good astronomical knowledge is... tricky. Then there's the time travel paradoxes he ignores!

 

[Cuddles]

There's a few theories, but the common one now (I may be wrong), is that if you traveled beyond the edge of the universe, you'd just end up on the other side, much as if you would if you ran around the globe. This has to do with the universe having four physical dimensions, and we can only see into the third (much like a 2-dimensional creature couldn't really perceive us as anything but a shadow of ourselves).

There's no such thing as the "edge of the universe", any more than there's an "edge of the globe". If you travel around the Earth you don't pass a boundary and suddenly end up back where you started, you just travel continuously in a circle. Same for the universe (if it is actually closed, which is by no means certain).

Where the globe analogy breaks down is that the universe is rather bigger than the Earth and is expanding. Even travelling at the speed of light, it would not actually be possible to travel in a circle and end up back where you started, since the distance you'd have to travel would be growing faster than you were traveling it. In fact, this is one of the ways we have of measuring the size of the universe. If it was fairly small, then we would see the effects of light traveling around and coming back from the other side. Since we can't see any of the effects that would be expected from this, we know that the physical universe must be many times larger than the observable universe.

 

[dirtygreek]

But of course, if the universe was infinite with an infinite amount of matter -- including stars -- then that would make one wonder why we don't see an infinite amount of light in the sky?

Because light fades. We can't see all the stars in existence, only those whose light can reach us. I'm not saying whether I buy the universe being infinite, because I'm far from being qualified to make that sort of judgment, but that's the answer to why we don't see infinite light.

 

[Lonewulf]

Thanks for the info, Cuddles.

Might I ask how you know all of this? Self-study also, or are you "officially" an expert in the field?

 

[Lonewulf]

Because light fades. We can't see all the stars in existence, only those whose light can reach us. I'm not saying whether I buy the universe being infinite, because I'm far from being qualified to make that sort of judgment, but that's the answer to why we don't see infinite light.

Sorry, but according to astronomers, that's the wrong answer. Light doesn't actually "fade"; the particles that make up light do spread, which makes it seem to "fade" to the casual observer, but the particles never stop, they just keep going at the speed c. If there was an infinite amount of light, there would still be an infinite amount of particles, so no amount of fading would stop the overall spread.

It's like saying that shotgun pellets would spread, so hosing an area with millions of shotguns would never touch a lone bear standing in a 20y by 20y square in the line of fire.

To put it another way, rain is just made up of droplets; a single droplet is unlikely to touch you. But in a storm, you're going to get wet. Particles of light would be that rain.

 

[JoeTheJuggler]

But of course, if the universe was infinite with an infinite amount of matter -- including stars -- then that would make one wonder why we don't see an infinite amount of light in the sky?

Because the Big Bang happened some 14 billion years ago, so that sets the limit for how far we can see (14 billion light years).

But if space WERE infinite, outside of where matter is... what is space expanding into, then?

That's the wrong way of looking at expansion. It's the expansion of space itself--there is no outside of space that has to have space for the universe (or space) to expand into. The Big Bang didn't happen in the middle of a big empty space.

At any rate, whether the universe is infinite or not is not a solved question in modern cosmology.

 

[Belz...]

Because the Big Bang happened some 14 billion years ago, so that sets the limit for how far we can see (14 billion light years).

I've heard an interesting hypothesis that the light from some of the furthest quasars actually looped once through the universe and we're actually seeing the same galaxy twice.

I suppose they have other means to determine the age of the universe, however, besides redshift.

 

[JoeTheJuggler]

I've heard an interesting hypothesis that the light from some of the furthest quasars actually looped once through the universe and we're actually seeing the same galaxy twice.

You mean like once as a young quasar and once as a mature galaxy billions of years later? I have no idea how they could test that hypothesis. I don't think there'd be any way of identifying any two quasars/galaxies as the same thing. (Also, why would they be two distinct images and not a streak from one to the other. If the light looped, there would be nothing causing a break from the older to the younger image.)

With gravitational lensing we can see the same galaxy twice (the light curved around a large mass between our eyes and the distant galaxy), but that doesn't sound like what you're talking about.

 

[dirtygreek]

If there was an infinite amount of light, there would still be an infinite amount of particles, so no amount of fading would stop the overall spread.

It's like saying that shotgun pellets would spread, so hosing an area with millions of shotguns would never touch a lone bear standing in a 20y by 20y square in the line of fire.

To put it another way, rain is just made up of droplets; a single droplet is unlikely to touch you. But in a storm, you're going to get wet. Particles of light would be that rain.

I think your metaphors break down because of a huge difference in scope. The photons spread, and therefore they don't all make it to our planet. In other words, assuming there is infinite space in the universe and infinite light, there's no reason we'd see it all.

 

[Belz...]

You mean like once as a young quasar and once as a mature galaxy billions of years later? I have no idea how they could test that hypothesis.

I don't think they could, unless some other indication could be used; but it's a neat idea.

I don't think there'd be any way of identifying any two quasars/galaxies as the same thing. (Also, why would they be two distinct images and not a streak from one to the other. If the light looped, there would be nothing causing a break from the older to the younger image.)

Not sure I understand. Wouldn't that apply to the single image as well ?

 

[JoeTheJuggler]

I hate to say it, but his books weren't exactly about total accuracy of present-day theories.

You've got to admit though that the passage I quoted sounds exactly like Makaya's argument. (The universe is mostly empty space, so "alien life possibility is pathetic". The number of stars and galaxies and planets doesn't matter, because most of the universe is empty, uninhabitable space.)

 

[JoeTheJuggler]

(Also, why would they be two distinct images and not a streak from one to the other. If the light looped, there would be nothing causing a break from the older to the younger image.)

Not sure I understand. Wouldn't that apply to the single image as well ?

Nevermind that point. It wasn't very thoroughly or thoughtfully thought through.

I'll just stick with my first point--there's no way to test the looping notion.

 

[Hitch]

The question is this:

Given that God is infinite and that the universe is also infinite, would you like a toasted tea-cake?

 

[JoeTheJuggler]

Sorry, but according to astronomers, that's the wrong answer. Light doesn't actually "fade"; the particles that make up light do spread, which makes it seem to "fade" to the casual observer, but the particles never stop, they just keep going at the speed c. If there was an infinite amount of light, there would still be an infinite amount of particles, so no amount of fading would stop the overall spread.

You're right that the answer isn't light fading. It also doesn't mean that the universe is necessarily finite. We can only see light up to about 14 billion light years away because the light hasn't had more time than that to travel. (We can't see galaxies that might be further away because that light hasn't reached us yet.) As the universe continues to expand, some of it will always be farther away than there has been time for the light to reach us.

If expansion stops or reverses, there could be a time when the "sky" would be infinitely white.

ETA: I'm pretty sure the current consensus is that it will not stop expanding or reverse (Big Crunch).