Finite or infinitely expanding?

11/10/2005 3:06:45 PM

Infinitely expanding. Next...

11/10/2005 3:08:18 PM

it would seem neither really makes sense

finite implies a magical border with nothing on the other side. infinately expanding just means the border is just growing. so again, i dont like either.

11/10/2005 3:14:14 PM

^^
On that same note, something crossed my mind in physics class the other day:

Even though on paper astrophysicists have shown it's possible for an object to travel faster than the speed of light without exceeding light speed, could we even really do intergalactic travel when we would have no clue where the galaxies are? (since the light we get shows their position from hundreds / thousands / millions of years ago...)

Meaning even if we aren't alone, for all practical purposes we are alone


[Edited on November 10, 2005 at 3:16 PM. Reason : to Gamecat]

11/10/2005 3:14:44 PM

as much am I'm sure astronomers appreciate this thread, they already have an enormous amount of literature that you can peruse to educate yourself on the subject

11/10/2005 3:15:55 PM

I imagine we'd probably practice by going to the closer star systems first. We'd still miss if we aimed at them, but our margin of error wouldn't be as wide, leaving a short hop after our first shot.

I could be wrong, but the Doppler effect might be able to give us a clue as to what direction the galaxies are going. Since it's unlikely that their paths would be interfered with, we could probably just lead the galaxy in the direction it was moving.

Also...

Quote :

"TGD: on paper astrophysicists have shown it's possible for an object to travel faster than the speed of light without exceeding light speed"

Plz to enlighten. I love some bizarre physics.

[Edited on November 10, 2005 at 3:19 PM. Reason : ...]

11/10/2005 3:18:29 PM

let's just worry about getting our ass back to the moon

ok?

11/10/2005 3:18:59 PM

Finite and expanding, perhaps infinitely but perhaps periodically.

11/10/2005 3:21:32 PM

OH DEAR, PENIS HAT

NEGATIVE VACUUM ENERGY WHAT WHAT?

11/10/2005 3:22:39 PM

paging Wintermute

11/10/2005 3:23:19 PM

You'd only be traveling at superluminal speeds as measured by outside observers, right?

Or something like that?

11/10/2005 3:23:35 PM

isn't this one of those things where we can truly say "it doesn't matter"... and mean it?

11/10/2005 3:24:03 PM

i'm gonna hook you up

11/10/2005 3:24:46 PM

Is DH Hill finite or infinitely expanding?

11/10/2005 3:26:07 PM

i bet if you went there

you could find out

11/10/2005 3:26:50 PM

Quote :

"Quote : "TGD: on paper astrophysicists have shown it's possible for an object to travel faster than the speed of light without exceeding light speed" "

yea but didn't it require a tremendous amount of energy to warp the space-time around the vehicle. Like half of all the energy in the universe.

11/10/2005 3:34:49 PM

The purpose of this thread that I had in mind was to see what others viewpoints were. I was on another message board where we were discussing teaching intelligent design theory along with other theories of creation. The Law of Conservation of Matter and The 1st Law of Thermodynamics were mentioned, as neither matter nor energy can be created or destroyed, just change forms.

Someone else mentioned that these are only applicable for closed systems, which got me to wondering...is the universe a closed or an open system? And it matter or energy cannot be created or destroyed, how did we get all this matter and energy here in the first place?

11/10/2005 3:37:13 PM

The universe is a big place, perhaps the biggest...

11/10/2005 3:59:41 PM

It could be very small in the entire scheme of things. The universe as we know it could just be an atom sized component of a macro universe.

11/10/2005 4:02:42 PM

Quote :

"Gamecat: Plz to enlighten. I love some bizarre physics."

clalias is basically on the right track, although the newer stuff seems to indicate the energy needs aren't that big at all (we just have to figure out how to generate anti-gravity )

It's all basically string theory stuff and the string theory model of gravity. Essentially you generate a gravitational field around a ship, slightly offset from the ship's center of mass, so the space in front of the vehicle is artificially compressed while the space behind it is artificially expanded. At the same time you would have to create some type of reverse-/anti-gravitational field with a smaller radius to stop the ship from being crushed.

The warping of space allows the vehicle to cover faster-than-light-speed distance, while the gravitational "bubble" the ship is in means it never actually approaches the speed of light.

[I'm only able to comprehend about a fifth of the actual math and physics behind it (if that), but damn if I won't try and read this stuff for hours anyway ]

But that all misses the point: how would we actually find other galaxies once we reach post-light speeds?

[Edited on November 10, 2005 at 5:04 PM. Reason : ---]

11/10/2005 5:03:01 PM

^^^^^^^^wow, are those rooms above the atrium new, or was i just too oblivious to notice them when i was an undergrad?

11/10/2005 5:04:31 PM

They've been there since the beginning IIRC. Faculty Senate chambers and some other office/meeting spaces are up there I believe.

11/10/2005 5:06:25 PM

ah, so

11/10/2005 5:16:59 PM

Quote :

"wow, are those rooms above the atrium new, or was i just too oblivious to notice them when i was an undergrad?"

It's actually a secret nazi research facility, or that's what I had assumed them to be, but yeah, they've always been there.

11/10/2005 5:17:50 PM

Hologram.

11/10/2005 5:24:55 PM

no, this is a picture I took at the facility one day:

11/10/2005 5:31:06 PM

Quote :

" Even though on paper astrophysicists have shown it's possible for an object to travel faster than the speed of light without exceeding light speed, could we even really do intergalactic travel when we would have no clue where the galaxies are? (since the light we get shows their position from hundreds / thousands / millions of years ago...) "

Please to watch any sci fi show, ignoramus! They always have some sort of method for calculating the drift. Even asimov has this in his old books.

11/10/2005 6:00:01 PM

omg I was called an ignoramus by skokiaan...and then told to get my knowledge from sci fi movies. I feel so unworthy of being in the presence of such greatness

11/10/2005 7:07:28 PM

2 amazing books all of you should read if you haven't already:

The Elegant Universe: Superstrings, Hidden Dimensions, and the Quest for the Ultimate Theory

The Fabric of The Cosmos: Space, Time, and the Texture of Reality

both are writtn by Brian Greene, and the first one was made on pbs nova as a 3 part show, which you can watch for free on nova's website.

11/10/2005 7:25:07 PM

Quote :

"infinately expanding just means the border is just growing."

I don't pretend to be an authority on astro-physics, but I think that this idea isn't completely right. The border is expanding, you are right about that, but I think there's a little bit more to it than that.

I don't remember which issue, but according to a Scientific American article that actually covers common misconceptions about the universe, space itself is actually expanding. In order for that to make any sense, think back to the Big Bang. The name implies that there was initially an area of extremely intense pressure and extremely small volume, but it then spread out, increasing its volume and decreasing its pressure (like an explosion, hence the name). However, the "Bang" was not an explosion in the sense that there was a sudden increase in volume, but rather an increase in space itself. The key here is to keep in mind that volume and space are two different things.

The analogy that the article gives is ants sitting on the surface of a balloon (that is assumed to be perfectly spherical) that is being inflated. Each day the balloon gets filled with slightly more air, and so it becomes larger. However, if the ants stay perfectly still, they're not getting larger or smaller with respect to each other. They're also standing still relative to themselves, but if they want to interact with each other they have to travel an ever-growing distance each day. Even though nothing is actually moving, space is becoming bigger. The surface of the balloon, then, can be thought of as the universe, and the ants can be any gravitational body. If the volume of the universe was increasing, stars would have to lower their pressures in tandem. However, we know that they do not do this. It is therefore not volume that is expanding, but space. Hopefully that made some sense (I'm quoting the article from memory).

I guess my interpretation of your assertion is that there is some border beyond which nothing exists, but as it moves more "universe" suddenly appears. However, this is not really what's happening. Space itself is actually expanding, and entire galaxies are spreading out, getting further and further away from one another (although the article mentions that gravitational effects can overcome this expansion, causing galaxies and other very large masses to clump together and move as one body).

[Edited on November 10, 2005 at 7:36 PM. Reason : blah]

11/10/2005 7:33:31 PM

i understand what you mean and the concept, and i agree...it is just the "nothingness" that confuses me. i mean, we really have no concept of this nothingness as even our blank space has waves of energy and whatnot going through it. conceptually it is easy to discuss, but in actual practice...i mean...how does even that nothingness exist where the universe can expand out to it (though obviously not magically including as it is...nothing)? its just like the concept of infinity, so hard yet so easy to grasp. wonders of the universe you know?

11/10/2005 7:50:40 PM

ooh i made this thread a long time ago

Quote :

"It could be very small in the entire scheme of things. The universe as we know it could just be an atom sized component of a macro universe."

i still say the universe can't be expanding or have boundaries...there is only one universe...it's everything, including space... it's infinite...space can't be expanding...space is the absence of anything. it really doesn't seem that difficult to me. maybe the part of the universe we know of is expanding, but outside of that there's still more empty space.

11/10/2005 9:43:41 PM

I would say we do not know what the large-scale structure of the universe is. For that matter we don't really know what the basic structure of spacetime is. If physics is a consequence of geometry then what is that geometry? Is the universe we live in a hypersurface formed by some number of intersecting D-branes(coming decades)? Is the universe simply a 4-dimensional manifold with maximal symmetry in the spatial directions(still popular, essentially the Robertson Walker model)? Is the universe a static always existing one(Popular in Einstein's time)? Imagination is the only limit when the data is scarce, and now with the advent of M-theory we will soon have an infinity of cosmologies to pick from. This will make many cosmologies experimentally viable, wait and see... So what is the true structure of the universe? Can we know it? I doubt it. The best we can do is to approximate it with what we know as physics. It would be wise not to confuse that with reality. Physics is only a model, relax.

11/10/2005 9:53:42 PM

Since its free, can we get it off a torrent so we don't have to watch it on our computer? If so, any good ones?

[Edited on November 10, 2005 at 10:15 PM. Reason : The PBS Nova documentary that is]

11/10/2005 10:15:24 PM

yea i'm pretty sure you can find it on torrent, not sure where though i always just streamed it from the pbs site :/

11/10/2005 10:41:59 PM

nastoute won this thread a long time ago.


Anyway, Greg, we've been taking observations of the sky long enough that we should be able to extrapolate fairly accurately where to go to get to a particular galaxy. However, there are always going to be some errors due to our inability to accurately and precisely determine interstellar distances and ages. Those are two of the most fundamental questions in practical astrophysics, but are also two of the most difficult to really pin down precisely. My guess is that we would be limited to aiming for a general neighbourhood, coming out of "warp speed" a few times to adjust based on new observations, rinse repeat until you're within a small enough distance to approach your target at subluminal (is that a word?) speeds.

11/10/2005 11:48:05 PM

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11/11/2005 12:07:11 AM