Earth's absolute speed

ClaysGhost · Post by **ClaysGhost** » 2003-07-08 05:42am

kojikun wrote:
SyntaxVorlon wrote:Gotta love AL.
I hate the incestuous German prick. EINSTEIN KILLED NEWTON!! And our hopes of FTL

Physics killed Newton, and FTL isn't necessarily dead. It will just require a lot more effort than using a very big rocket.

The Duchess of Zeon · Post by **The Duchess of Zeon** » 2003-07-08 06:48am

DON'T LISTEN TO THEM! SPACE IS REALLY FILLED WITH ETHER AND YOU CAN KEEP ACCELERATING IN A NEWTONIAN FASHION TO WELL ABOVE THE SPEED OF LIGHT!

Okay, seriously, Howedar, this is, quite simply, the point at which things become easy in physics. There's confusing stuff beyond this out there which would really make your brain bleed.

Zoink · Post by **Zoink** » 2003-07-08 08:57am

Sindai wrote: The next best thing would be finding Earth's velocity relative to the point at which the Big Bang originated. But then, I believe it's been establshed that that's increasing.

I see people have addressed the relativity of speed, but this point hasn't been addressed:

There is no point in the universe where the big bang originated. Imagine a sphere that expands from a point to a larger size. Imagine that the surface area is the universe (just the surface area). There is no point on the surface which is the originating point. In fact "every" point on that sphere is the big bang. Where you are standing right now is the big bang, where I'm standing is also. Had you lived from the big bang t'ill now, from your perspective, the universe has expanded from your location away from you (ie. you're the center of the universe... how's that for an ego booster?).

This is why the universe appears to be the same and also appears to be moving away from us, no matter which direction you look.

PS. Observation of the cosmic background radiation seems to indicate that the universe's big bang was actually an infinite sheet (instead of sphere) that began expanding, with our known universe being a point on that sheet, but the sphere analogy is still relevant to illustrate the relative motion (and is easier to visualize).

Durandal · Post by **Durandal** » 2003-07-08 10:06am

Alyeska wrote:
kojikun wrote:
Alyeska wrote:I don't care about appearances, I want to know absolutes. If a ship is moving at half light speed and fire a laser, its real speed is only half light speed?
The beams speed is C. Always, regardless of frame of reference.
That is quite literaly impossible. Light can not travel at two different speeds at two different reference points. If light is traveling at .C PLUS the speed of the reference point, it MUST be traveling FTL to a "stationary" reference point.

Again, the speed of light is constant from all frames of reference. Nothing on relativistic scales is linear.

Gil Hamilton · Post by **Gil Hamilton** » 2003-07-08 10:42am

There really is a simple explaination to why relativity, both special and general, works. Every morning, after brushing it's teeth and taking a shower, the universe snorts line after line of blow until it's sufficiently fucked up that Einstienian physics work.

Sindai · Post by **Sindai** » 2003-07-08 11:52am

Zoink wrote:There is no point in the universe where the big bang originated. Imagine a sphere that expands from a point to a larger size. Imagine that the surface area is the universe (just the surface area). There is no point on the surface which is the originating point. In fact "every" point on that sphere is the big bang. Where you are standing right now is the big bang, where I'm standing is also. Had you lived from the big bang t'ill now, from your perspective, the universe has expanded from your location away from you (ie. you're the center of the universe... how's that for an ego booster?).

Nuts. I thought the expansionary universe might screw me up on that one. Oh well; learn something new every day.

Darth Yoshi · Post by **Darth Yoshi** » 2003-07-08 04:41pm

Zoink wrote:
Sindai wrote: The next best thing would be finding Earth's velocity relative to the point at which the Big Bang originated. But then, I believe it's been establshed that that's increasing.
I see people have addressed the relativity of speed, but this point hasn't been addressed:

There is no point in the universe where the big bang originated. Imagine a sphere that expands from a point to a larger size. Imagine that the surface area is the universe (just the surface area). There is no point on the surface which is the originating point. In fact "every" point on that sphere is the big bang. Where you are standing right now is the big bang, where I'm standing is also. Had you lived from the big bang t'ill now, from your perspective, the universe has expanded from your location away from you (ie. you're the center of the universe... how's that for an ego booster?).

This is why the universe appears to be the same and also appears to be moving away from us, no matter which direction you look.

PS. Observation of the cosmic background radiation seems to indicate that the universe's big bang was actually an infinite sheet (instead of sphere) that began expanding, with our known universe being a point on that sheet, but the sphere analogy is still relevant to illustrate the relative motion (and is easier to visualize).

In other words, just as people can really only move in two dimensions on a three-dimensional earth, the earth can only move in three dimensions on a four-dimensional universe. At least that's the analogy my physics teacher used.

And it doesn't matter that light isn't suppose to move at c regardless of the perspective. It just does.

Durandal · Post by **Durandal** » 2003-07-09 10:23am

No, no and no again. My high school physics teacher made a similar fuck-up (as much as I consider him an inspiration to me getting into the field) by doing exactly what yours apparently did, take the idea of a "flat" universe entirely too seriously. A flat universe doesn't mean that the universe is sitting on a table top. It means that the spatial distortions created by gravity essentially cancel each other out, leaving an undistorted spacetime on average.

Zoink · Post by **Zoink** » 2003-07-09 01:34pm

I had read that flat geometry implied the universe should be infinite in size, thus had to be infinite at all points during existence. The universe would be an expanded point on an infinite sheet (analogy for visualization purpose only), with different points having different properties, expanding at different rates, which is the founding requirement for the anthropic principle.

That, curved spacial geometry allowed for the universe to be finite in size (although not required), allowed for the sphere analogy, which causes problems for the anthropic principle, which requires an infinite universe.

Rye · Post by **Rye** » 2003-07-09 01:34pm

The way i always thought of it was a s soon as light is emitted from somewhere, it has no momentum(and thereby not travelling at the speed of what it was emmited from +/-c) , and so travels at a constant speed, but takes longer routes through denser materials.

kojikun · Post by **kojikun** » 2003-07-09 02:03pm

Zoink wrote:I had read that flat geometry implied the universe should be infinite in size, thus had to be infinite at all points during existence. The universe would be an expanded point on an infinite sheet (analogy for visualization purpose only), with different points having different properties, expanding at different rates, which is the founding requirement for the anthropic principle.

That, curved spacial geometry allowed for the universe to be finite in size (although not required), allowed for the sphere analogy, which causes problems for the anthropic principle, which requires an infinite universe.

Thats a different version of a flat universe. That involves the geometry of space as a whole outside of gravity's effect on it.

Rye wrote:The way i always thought of it was a s soon as light is emitted from somewhere, it has no momentum(and thereby not travelling at the speed of what it was emmited from +/-c) , and so travels at a constant speed, but takes longer routes through denser materials.

No no, light has momentum, always did. It has to do with einsteins famous equation E=mc². If you have, say, 1 joule of light, it has a "virtual mass" of 1.1E-17 grams. Or roughly so.

Howedar · Post by **Howedar** » 2003-07-09 03:38pm

Rye wrote:The way i always thought of it was a s soon as light is emitted from somewhere, it has no momentum(and thereby not travelling at the speed of what it was emmited from +/-c) , and so travels at a constant speed, but takes longer routes through denser materials.

That was sorta my understanding.

Zoink · Post by **Zoink** » 2003-07-09 04:19pm

kojikun wrote: Thats a different version of a flat universe. That involves the geometry of space as a whole outside of gravity's effect on it.

The article I read had the two linked. The implication was that if you measured the curvature of spacetime to be flat (via patterns in the cosmic background radiation) or hyperbolic then the universe should be infinite in size, which would make the sphere analogy false.

kojikun · Post by **kojikun** » 2003-07-09 06:29pm

Zoink wrote:The article I read had the two linked. The implication was that if you measured the curvature of spacetime to be flat (via patterns in the cosmic background radiation) or hyperbolic then the universe should be infinite in size, which would make the sphere analogy false.

They actually have measured it, and the universe is indeed curved. Atleast, it should be if it were looked at from the 4th dimension. But this is unrelated to gravitation.

Durandal · Post by **Durandal** » 2003-07-09 06:35pm

Measurements taken from the CMB indicate a Euclidean, flat universe.

kojikun · Post by **kojikun** » 2003-07-09 06:46pm

Durandal wrote:Measurements taken from the CMB indicate a Euclidean, flat universe.

When was this? Recent studies show that at certain angles in the sky various frequencies of radiation are excluded but only from those angles, indicated a closed universe, either cylindrical or toroidal in nature.

Durandal · Post by **Durandal** » 2003-07-09 07:07pm

kojikun wrote:
Durandal wrote:Measurements taken from the CMB indicate a Euclidean, flat universe.
When was this? Recent studies show that at certain angles in the sky various frequencies of radiation are excluded but only from those angles, indicated a closed universe, either cylindrical or toroidal in nature.

The MAP data showed that the universe is flat, and about 13.7 billion years old.

kojikun · Post by **kojikun** » 2003-07-09 07:55pm

so we have two different types of experiments showing two different things

i'll take yours as more valid since i cant find a link to the article i was talking about.

Durandal · Post by **Durandal** » 2003-07-09 08:21pm

kojikun wrote:so we have two different types of experiments showing two different things i'll take yours as more valid since i cant find a link to the article i was talking about.

I'm surprised that you didn't know about this. It was a very big deal when it was originally reported a few months ago.

kojikun · Post by **kojikun** » 2003-07-09 08:24pm

Durandal wrote:I'm surprised that you didn't know about this. It was a very big deal when it was originally reported a few months ago.

Well, honestly, I don't pay much attention to the distribution of darkmatter because I do not see a logical explanation for why curvature of space would affect it or vice versa unless the universe is closed.

Durandal · Post by **Durandal** » 2003-07-09 09:06pm

kojikun wrote:
Durandal wrote:I'm surprised that you didn't know about this. It was a very big deal when it was originally reported a few months ago.
Well, honestly, I don't pay much attention to the distribution of darkmatter because I do not see a logical explanation for why curvature of space would affect it or vice versa unless the universe is closed.

Whether or not the universe is open or closed depends upon the critical mass density versus the distribution of matter. If the mass density is not sufficient (i.e. does not meet the critical mass density), the universe is negatively curved and will expand forever. If the mass distribution of the universe is the same as the critical mass density, the universe is flat and will expand forever, which is what it's looking like. If the mass distribution exceeds the critical mass density, the universe is closed, and we'll end up seeing a Big Crunch. The distribution of dark matter heavily affects the mass density of the universe because dark matter makes up almost 3/4 of all the matter in the universe, and thus it heavily affects the curvature of spacetime.

kojikun · Post by **kojikun** » 2003-07-09 09:07pm

Durandal wrote:Whether or not the universe is open or closed depends upon the critical mass density versus the distribution of matter. If the mass density is not sufficient (i.e. does not meet the critical mass density), the universe is negatively curved and will expand forever, which is what it's looking like. If the mass distribution of the universe is the same as the critical mass density, the universe is flat and will expand forever. If the mass distribution exceeds the critical mass density, the universe is closed, and we'll end up seeing a Big Crunch. The distribution of dark matter heavily affects the mass density of the universe because dark matter makes up almost 3/4 of all the matter in the universe, and thus it heavily affects the curvature of spacetime.

Thats circular tho. WHY is critical mass density able to affect the universe's shape? It makes no sense.

Durandal · Post by **Durandal** » 2003-07-09 11:48pm

kojikun wrote:
Durandal wrote:Whether or not the universe is open or closed depends upon the critical mass density versus the distribution of matter. If the mass density is not sufficient (i.e. does not meet the critical mass density), the universe is negatively curved and will expand forever, which is what it's looking like. If the mass distribution of the universe is the same as the critical mass density, the universe is flat and will expand forever. If the mass distribution exceeds the critical mass density, the universe is closed, and we'll end up seeing a Big Crunch. The distribution of dark matter heavily affects the mass density of the universe because dark matter makes up almost 3/4 of all the matter in the universe, and thus it heavily affects the curvature of spacetime.
Thats circular tho. WHY is critical mass density able to affect the universe's shape? It makes no sense.

No, it's not. The universe's "shape" is determined by the net amount of spacetime curvature it has, which is in turn affected by gravity, which is in turn affected by mass. Critical mass density affecting the shape of the universe is a simple consequence of general relativity.

Malecoda · Post by **Malecoda** » 2003-07-10 04:04am

I can't believe the first few posts come from people who've been here any length of time. Any length of time at all.

kojikun · Post by **kojikun** » 2003-07-10 09:43am

Durandal wrote:No, it's not. The universe's "shape" is determined by the net amount of spacetime curvature it has, which is in turn affected by gravity, which is in turn affected by mass. Critical mass density affecting the shape of the universe is a simple consequence of general relativity.

Been through this before. Mass cannot affect the curvature of spacetime without an external force acting upon it.