Quick Question About Space/time

So I was pondering the theory of relativity one day, trying to figure it out and I came to a question.

Since space/time around a large mass is actually traveling towards the mass, does that mean, that we on earth are technically ALWAYS traveling away from the center of the earth?

Er...

What if we were wanting to fall towards the center of the earth but it was always in the way?

What I mean is, since the earth is already as compacted as it is going to get anytime soon, and space/time is going towards the center (due to the nature of gravity) does this mean that the mass of the earth is actually moving away from the center(relative to space/time)?

Accelerating away from the planet, not traveling away, according to one interpretation of the Einstein equivalency principle. There is a subtle difference between the two in this context that is quite important.

It's not like matter is a drain into which space is flowing, it's more like the rock-on-a-rubber-sheet analogy you see in pop-science books all the time. I understand that that analogy requires gravity in order to explain gravity, but think of it this way (which is a horrible analogy, but it should work so long as you don't intend to study the subject in too much detail):
As the sheet is stretched out, it is pulled thin. Since there is less sheet in each square inch of it, that can be thought of as being less dense, and a sort of spacetime pressure, which is lower in the presence of mass, can be thought of as what pushes us towards the earth.
(Please don't shoot me, those who know this subject well! It's just a bad analogy!)

Ah I see what you are getting at now. so if we looked at the earth, the space/time that the earth is taking up, would be somehow less (in some way or another) and that makes all the matter around it to want to go towards it.

This is what I'm sort of picturing in my head, imagine from star trek, one of the ships is warping away from a black hole, and technically they are at warp compared to all the space around them, but relative to the black hole they are standing still.

Since, in relation to the center of the earth we are standing still, does that mean that we also are accelerating or traveling away?

Pretty much, but as I said, this is just an analogy, it's not what is actually happening, AFAIK.

Well, the warp drive in Star Trek is (according to the producers) more like what they usually call a hyper drive; it takes them out of normal space and they travel through this other space they call subspace (but is usually referred to in other media as hyper space). However, the show depicts it as travel through our space, so I've considered that the whole warp bubble thing might create a sort of spatial 'marble' disconnected from the rest of space, but adjacent to it, that they can then 'roll' much faster than the speed of light through the use of other means of propulsion, which would seem to match what's depicted in the show. But that's just my thoughts on their particular form of FTL travel.

An actual warp drive is a real theoretical construct, first discussed by Miguel Alcubierre, which uses the principles of general relativity to create a means of 'faster than light' travel. I enclose the term in quotations because no matter actually moves faster than light, it simply allows one to move 1 light year in less than 1 year, for instance. You can read more about that at the wiki article:
http://en.wikipedia.org/wiki/Alcubierre_drive
But don't get your hopes up... It uses an incredible amount of energy, and must produce a sort of energy which we don't yet suspect to even exist! For more about this, see the following thread in which I compared the energy needed to move 12 grams of carbon with an Alcubierre Drive to the energy output of your average large electrical service utility provider (and I do mean large, the one I used was among the ten largest in the world.)
http://www.physforum.com/index.php?showtop...ndpost&p=346564

We are accelerating away, yes: Hence the force we feel pushing us down, just like the way you feel pushed back into your seat when you accelerate in your vehicle. But we are not traveling away, because then we'd fly off the planet. It's a bit of a complicated issue, here are some links that might help explain better than I can:
Gravitation
Introduction to general relativity
General Relativity
Equivalence principle
Acceleration

I reccommend you bookmark the following link, it's an incredibly useful one:
Hyperphysics

awesome =]

I am just getting started researching this on my own, Iv read all the wiki's and such on relativity, sometime I hope to understand the theory.

Quote MP
"An actual warp drive is a real theoretical construct"

MP,
Your own wiki reference describes it as a "speculative mathematical model". Would you ever at least look at your references before you dish out any more of your pseudoscience - this is worse than any crackpottery or crank theories - because you mislead people into thinking that you actually know something about mainstream science and that your posts reflect mainstream thinking. And over on a neighbouring thread you are pretending to know something about String Theory -yet you have demonstrated clearly that your self-proclaimed "knowledge" of gravitons runs totally counter to current mainstream physics.

Al Gore would not like the Alcubierre Drive.

"Speculative mathematical model" can be read as meaning it's a mathematical concept derived with a slight lacking of rigour. Thus it's a theoretical construct which isn't justified by evidence. Thus it's a real theoretical construct, where 'real' means the theoretical construct exists, not the thing itself.

So there's no big contradiction. You're just doing your usual thing of falling over yourself in your rush to throw an insult.

Pipe down Mr Pot.

Yes Edward, take heed, AN knows how to insult the right way at the right time.

hey, no physics flame wars.

Young Padawan, you have much to learn.




In other news the Hershy (chocolate) observatory is being launched Thursday.

haha. They should send a giant piece of chocolate into orbit, which would make us humans a very funny bunch to whoever is watching.

Here, I really think you need to read this:
Guide to Grammar and Writing

The word "real" in that quote qualifies the phrase "theoretical construct," in which the word "theoretical" qualifies the word "construct."
There's a reason they appear in that order.

Would it make you happy if I copied and pasted every answer I give or claim I make about physics, instead of demonstrating some limited (but still vast, by your standards) understanding of the subjects by answering in my own words?

Look at AlphaNumeric's post above. He is heavily involved in mainstream physics, and he has no problem with what I said. So how exactly have I deviated from the mainstream, here?
This means you are either lacking in the necessary intelligence to understand me, are blinded by your own distaste for me (which would need to border on hatred to explain this...) to form an accurate interpretation of my words, or you yourself are purposefully attempting to deceive others into thinking that I don't know what I'm talking about.

For the record, if you look at my posting history, you will see that it's rife with references to how little I know in comparison to an actual physicist. In fact, the only times I speak favorably of my own level of knowledge is when I'm comparing myself to someone like you.

So you are claiming that I never actually read any pop-science books on string theory? Or that I haven't retained any of the information gleaned from them?
Maybe you're claiming that I don't know that the name of string theory derives from the postulate that many particles are composed of one dimensional, vibrating strings. Or maybe you're claiming that I don't know that Polchinski helped discover the concept of D-branes, which are extended objects upon which open strings can end, and that this discovery helped to formulate a new sort of cosmology, known as "Braneworld Cosmology," in which the universe we perceive is itself a D3-brane, and that since gravitons are closed strings (Oh no, not more about gravitons!) this might help explain the relatively weak strength of gravity in comparison to other forces. Yeah, I know absolutely nothing about string theory.
Even though I may have just written more about string theory than you ever knew, bear in mind that I'm still very well aware of just how little I know in comparison to a string theorist.

Now that's just complete BS. I asked you to give me even a single argument that didn't rely on an appeal to authority and you ignored the challenge. I acknowledged that I may have used a phrase incorrectly to describe an idea, but as yet, not one person has come forward to defend your claim that the idea I presented was wrong.
In fact, my position is one which is blatantly obvious to any physicist, astronomer, or fan of science fiction: That black holes have gravitational fields, and that the messenger particle of these fields are not inexorably drawn into the black hole by the very field which they constitute! The fact that you feel the need to claim I am twisting mainstream science in order to support this position indicates nothing more than your own lack of principles, intellect and ability to hold up your end of a debate.

This post has been edited by MjolnirPants on May 12 2009, 04:04 AM