Could ME thrusters be used to produce torque?

TallDave · Post by **TallDave** » Sat Oct 03, 2009 4:13 pm

Helius wrote: Perhaps someone should inform the SETI folks they might take as evidence the existence of civilizations on the far side of the Universe by otherwise inexplicable local energy losses. I know a bunch of UFO folks that'd be on board with that explanation in a heartbeat. Personally, I think it's all a far fetch.

Actually, you'd be looking for inexplicable gains. The losses are to the entire Universe. Doubt they're big enough to see, though.

alexjrgreen · Post by **alexjrgreen** » Sat Oct 03, 2009 6:38 pm

chrismb wrote:
alexjrgreen wrote:Why do you think that space is expanding at the speed of light?
Because the 'deepest' space objects [to us] are ([age-of-the-universe].[speed-of-light]) away

The visible universe, then.

chrismb · Post by **chrismb** » Sat Oct 03, 2009 6:46 pm

Only the [3D] visible universe we can see is expanding at light speed. At least, that's all we can tell at the moment. 'Visible universe' and 'light speed' would seem to be attributes that one might expect to find together and associated, no?!

Helius · Post by **Helius** » Sat Oct 03, 2009 6:54 pm

TallDave wrote:
Helius wrote: Perhaps someone should inform the SETI folks they might take as evidence the existence of civilizations on the far side of the Universe by otherwise inexplicable local energy losses. I know a bunch of UFO folks that'd be on board with that explanation in a heartbeat. Personally, I think it's all a far fetch.
Actually, you'd be looking for inexplicable gains. The losses are to the entire Universe. Doubt they're big enough to see, though.

It was a joke. From "their" perspective, we're part of the rest of the entire universe. Their gain is our loss. A high school physics experimenter who's energy experiment doesn't balance, can mutter under his breath "Those dang Tralfamadorians", then add in his Tralfamadorian fudge factor to balance his energy budget. Get it? Blame the civilizations beyond the visible redshifted galaxies for the experimenter's energy loss errors.

TallDave · Post by **TallDave** » Sat Oct 03, 2009 6:57 pm

Oh, I see. I thought you meant local in the sense of over a small area in a distant location.

TallDave · Post by **TallDave** » Sat Oct 03, 2009 7:02 pm

chrismb wrote:Only the [3D] visible universe we can see is expanding at light speed. At least, that's all we can tell at the moment. 'Visible universe' and 'light speed' would seem to be attributes that one might expect to find together and associated, no?!

As we get farther from things, they are moving away faster. The limit of perception of the speed of expansion isn't a limit on the speed of expansion.

Eventually our observable universe will be one galaxy, and all the other ones we can see right now will be moving away faster than c.

chrismb · Post by **chrismb** » Sat Oct 03, 2009 7:07 pm

TallDave wrote:
chrismb wrote:Only the [3D] visible universe we can see is expanding at light speed. At least, that's all we can tell at the moment. 'Visible universe' and 'light speed' would seem to be attributes that one might expect to find together and associated, no?!
As we get farther from things, they are moving away faster. The limit of perception of the speed of expansion isn't a limit on the speed of expansion.

Eventually our observable universe will be one galaxy, and all the other ones we can see right now will be moving away faster than c.

It's not 'other points in our [3D] universe' that we're expanding away from.

All points in the universe are expanding away from the same point, at the same speed, and are now as far away from it as any other. Clearly, then, that point doesn't exist in our 3D universe, it wouldn't make geometric sense (as you highlight). Any movements we make in this 3D volume are therefore orthogonal to the direction of expansion.

In a sense you may be right that there may be points in the universe that are 'expanding' away from our point at faster than light speed, peaking at 2x light speed for such points as those that are directly opposite ours, the other side of the origin's axis.

TallDave · Post by **TallDave** » Sun Oct 04, 2009 2:43 am

That's a fairly common misunderstanding of the Big Bang and the expansion of space.

We are not -- I repeat NOT -- moving away from some central point. All points are moving away from each other.

At the time of the Big Bang, all of space was compressed. It has been expanding ever since. Therefore, the farther away something is from something else, the faster the two are moving away from each other. There is no c-related limit on how quickly the distance could be growing.

There is no axis. Remember, there are no reference points to say "Here is where the Big Bang happened." It was everywhere.

You should pick up Brian Greene's Elegant Universe for a thorough explanation of this. Here's a quick overview:

http://en.wikipedia.org/wiki/The_big_bang

http://en.wikipedia.org/wiki/Expansion_of_the_universe

While special relativity constrains objects in the universe from moving faster than the speed of light with respect to each other, there is no such theoretical constraint when space itself is expanding. It is thus possible for two very distant objects to be moving away from each other at a speed greater than the speed of light (meaning that one cannot be observed from the other). The size of the observable universe could thus be smaller than the entire universe.

It is also possible for a distance to exceed the speed of light times the age of the universe, which means that light from one part of space generated near the beginning of the Universe might still be arriving at distant locations (hence the cosmic microwave background radiation). These details are a frequent source of confusion among amateurs and even professional physicists.[1]

It's intuitively hard to get your mind around.

TallDave · Post by **TallDave** » Sun Oct 04, 2009 3:02 am

Actually, Helius, you might be onto something there (assuming, as still seems unlikely, there is something to the Mach effect).

Conventional wisdom is that highly advanced civilizations might be very hard to find because they would tend to build Dyson spheres in order to fully utilize the energy of their stars. But if you can use the Mach effect for essentially infinite power, they might be considerably easier to find. Depends on the power density I suppose.

MSimon · Post by **MSimon** » Sun Oct 04, 2009 3:42 am

Look at Lorentz geometrically.

Anything "stationary" in this universe is moving at the speed of light.

As soon as it starts moving it is actually moving at less than the speed of light.

Remember I was saying something about this about a year, year and a half ago?

Betruger · Post by **Betruger** » Sun Oct 04, 2009 4:59 am

Unless I'm mistaken (apologies in advance if I am), Woodward or one of his colaborators either based their hypothesies on, or their hypothesies were well-fitting with Barbour's non-time theory.
http://www.youtube.com/watch?v=WKsNraFxPwk

chrismb · Post by **chrismb** » Sun Oct 04, 2009 8:04 am

TallDave wrote:That's a fairly common misunderstanding of the Big Bang and the expansion of space.

We are not -- I repeat NOT -- moving away from some central point. All points are moving away from each other.

That seems to me to be a fairly common misunderstanding of fairly common misunderstandings!

Once you drop the idea that we're expaning through 3D space but recognise it is through higher dimensions (which, frankly, doesn't take a genius to accept is possible) then you have both satisfied - all points in space are expanding uniformly with respect to each other AND we're expanding from a single point (which is a point no longer in our 3-space). Seems self-evidently the most satisfactory answer to me.

chrismb · Post by **chrismb** » Sun Oct 04, 2009 8:12 am

MSimon wrote:Look at Lorentz geometrically.

Anything "stationary" in this universe is moving at the speed of light.

Exactly. Agree entirely. And that's my point/evidence I would claim.

We're moving within a 3D space which is expaning AWAY from a point in higher dimensions (I believe I can say exactly how many as well). That means we're travelling through that space and any motion we undertake here is at right anlges to that expansion. So, any vector sum is just the sum in quadrature of the motions. viz. you go V and I go Vo and together we're going c, so we have V^2 + Vo^2 = c^2

V^2 + Vo^2 = c^2
Vo = sqrt(c^2 - V^2)
Vo/c = sqrt(1 - [V^2/C^2])

How many lines did Einstein/Lorentz take to get to that ratio?

alexjrgreen · Post by **alexjrgreen** » Sun Oct 04, 2009 11:18 am

chrismb wrote:Once you drop the idea that we're expaning through 3D space but recognise it is through higher dimensions (which, frankly, doesn't take a genius to accept is possible) then you have both satisfied - all points in space are expanding uniformly with respect to each other AND we're expanding from a single point (which is a point no longer in our 3-space). Seems self-evidently the most satisfactory answer to me.

This extra dimension, orthogonal to 3D space, that we're travelling along at the speed of light.

I would call that time...

chrismb · Post by **chrismb** » Sun Oct 04, 2009 11:20 am

alexjrgreen wrote:
chrismb wrote:Once you drop the idea that we're expaning through 3D space but recognise it is through higher dimensions (which, frankly, doesn't take a genius to accept is possible) then you have both satisfied - all points in space are expanding uniformly with respect to each other AND we're expanding from a single point (which is a point no longer in our 3-space). Seems self-evidently the most satisfactory answer to me.
This extra dimension, orthogonal to 3D space, that we're travelling along at the speed of light.

I would call that time...

You surely can. And the interesting corollary is that time can be measured as a length - but not one of the dimensions we know. 1 light year in this other dimension = 1 year.

(If you're thinking "eh? so you're saying velocity is a dimensionless quantity??" I say; yes, naturally. It is the tangent of the angle subtended between your velocity vector and the direction of expansion (viz the line subtended back to time=0))