0 Members and 1 Guest are viewing this topic.
quote:Originally posted by neilepDoesn't everything have a centre ?..Ok...hypothetically then..if one could freeze the Universe into a Universal Ice cube...would it not stand to reason that it would have a centre ?
quote:Originally posted by HadrianPlease explain to me even if it had a centre what force could act on it to make it spin.
quote: What would it be spinning relative to?
quote:Originally posted by Soul SurferI think that we discussed this some months ago but I haven't been able to find the topicThe universe is generally agreed to be expanding and has expanded from a very small size. If the universe was spinning as fast as it could be when it was very small, the conservation of angular momentum would make it spin very slowly now. As to whether it is possible to detect the rotation of the whole universe. This is an interesting question and astronomers have looked seriously to see if they could find any rotation or any other irregularities in the visible universe.Consider our galaxy, we cannot see it rotating but can inferr that it is, by looking at the average radial velocities of stars and clouds of neutral hydrogen gas in different directions. We can also see similar effects in other disc shaped galaxies like ours. If there was any net rotation or difference in our whole univese it would appear in the average velocities of lots of galaxies or the cosmological microwave background radiation but no great anomalies have been detected altough there are a couple of small anomalies that may relate to an overall structure symmetry but this is subject to question.The concept of inflation has been introduced partially to explain this great unifomity in the visible universe. If we can only see a tiny part of the whole of the big bang it is much less likely that the bits we can see will vary very much
quote:Large Laser Gyroscopes for Monitoring Earth RotationObjectivesToday, Earth rotation parameters are routinely obtained using the geodetic space techniques VLBI (Very Long Baseline Interferometry), SLR (Satellite Laser Ranging), GPS (Global Positioning System) und DORIS (Doppler Orbitography by Radiopositioning Integrated on Satellite). Technical progress over the last decades resulted in a precision of recently 0.01 milliseconds in length of day and 0.1 milliarcseconds in pole coordinates. The common principle is the relative measurement of rotation by observing reference points, stars or satellites, outside the rotating Earth. All these techniques require global networks and structures for the observation and data handling, which are coordinated by the international services IVS, ILRS, IGS and IDS.The absolute measurement of rotation using inertial rotation sensors is a completely different approach. Mechanical gyros measuring the coriolis force are by far not sensitive enough to detect Earth rotation variations. Instruments measuring the centrifugal acceleration as a part of the total gravity vector, gravimeters and tiltmeters, are basically sensitive to Earth rotation variations, but even the excellent resolution of superconducting gravimeters of 10-11 g is not sufficient to resolve short-period Earth rotation variations. In contrast, laser gyroscopes use the Sagnac effect, whereas the small wavelength of the laser light allows an extreme high resolution. An adequate sensitive laser gyroscope attached to the Earth gives us instantaneous access to the spin of the Earth and the orientation of its axis. For the determination of the complete rotation vector, three linear independent laser gyroscopes are required.Installation and EnvironmentThe "G" ring laser is operating at the Fundamentalstation Wettzell (Bavaria). It is resting on a polished granite table being embedded in a 90 t concrete monument. The monument is attached to a massive 2.7 m diameter concrete pillar, which is founded on crystalline bedrock 10 m below the former surface. A system of concrete rings and isolation material shield monument and pillar from lateral deformations and heat flow. The instrument is protected against external influences in a subsurface installation, where a passive thermal stability is reached by a 2 m alternating layer of styrofoam and wet clay, and a 4 m earth mound. A lateral entrance tunnel with 5 isolating doors and a separate control room minimize thermal perturbations. After 2 years of thermal adaptation, the average temperature reached 12.2 deg with seasonal variations of less than 0.6 deg.
quote:Originally posted by PrajnaDhyanaHowever, since the Universe doesn't have edges
quote:You would have to be able to find where it ends in order to find the center.
quote:The distance between you and the computer screen you are reading this on is getting larger and larger every instant. The reason you don't notice is that you and the computer screen are also getting larger and larger at the same rate.
quote:As for the question: “All of this is fine, as far as it goes, but if rotation is purely a matter of external observation, then how is it possible for laser ring gyroscopes to measure the Earth's rotation without having sight of the sky? “You can measure the Earth's rotation relative to the gyroscope. And if that wasn't confusing enough, without having sight of the sky it's equally valid to say that the gyroscope is turning and the Earth is stationary. 
quote:Originally posted by Soul SurferThe earth rotates once in one day and is as you say well within the range of inertial navigation systems like laser gyros. Our part of the galaxy rotates once in about 250 million years. The whole universe if it is rotating will take many times this period to rotate.As I explained earlier it it quite possible to measure rotational velocities on an object without an outside source of reference because a galaxy or the universe as a whole is not a rigid body and rotates under the influence of its self gravitation.Remember also that the rotational velocity of the earth is approximately 1000 mph at the equatorLearn, create, test and tellevolution rules in all thingsGod says so!
quote:Do we know this for a fact, or is this merely supposition?
quote:You know that the number zero is exactly halfway between negative and positive infinity, and you can know this even without ever being able to physically approach infinity.
quote:But, in a laser gyroscope, there are no moving parts except the light itself.Even if this was not the case, the scenario you describe would imply an arbitrary rotation that is dependent upon the setup of the gyroscope; but it so happens that the laser gyroscope is measuring the rotation that is very close to that measured by astronomical observation, and so the value is clearly not arbitrary.
quote: If everything was expanding at the same rate, then we would never notice any expansion anywhere in the universe. Yet, the reason we do perceive the universe to expand is because the distance between ourselves and distant galaxies is apparently increasing. This would not be apparent if our own size was also increasing.
quote:Originally posted by PrajnaDhyanaquote:You know that the number zero is exactly halfway between negative and positive infinity, and you can know this even without ever being able to physically approach infinity.At first glance this seems a perfectly reasonable statement. But what do you say we take it out for a test drive and see how it handles in the curves? “ You know that the number zero is exactly halfway between negative and positive infinity” Ok, lets think about that. There are an infinite amount of number between zero and negative infinity. There are also an infinite amount of number between zero and infinity. So this seem like a perfectly legitimate statement. But now I say this:“The number 1,256,984.3578 is the exactly halfway between negative and positive infinity.” Ok, lets think about that one. There are an infinite amount of numbers between 1,256,984.3578 and infinity. There are also an infinite amount of number between 1,256,984.3578 and infinity. So this seems like a perfectly legitimate statement. In fact, you can say this about any number you can think of, since there will always be an infinite amount of numbers before and after it.
quote:The same could be said about any point in space. Since there is an infinite amount of space in every direction from me, I could say that I am the center of the Universe. But you could say that the Andromeda galaxy is the center of the Universe and it would be just as valid, since there would be an infinite amount of space in every direction from it. You can say this about any point in space.
quote:quote:But, in a laser gyroscope, there are no moving parts except the light itself.Even if this was not the case, the scenario you describe would imply an arbitrary rotation that is dependent upon the setup of the gyroscope; but it so happens that the laser gyroscope is measuring the rotation that is very close to that measured by astronomical observation, and so the value is clearly not arbitrary. What you are measuring is the motion of the light relative to the Earth. The motion is still being measured by comparing the relation of one object to another in a common frame of reference. But since there is nothing “outside” of the Universe, there is nothing to compare the Universe too. How can it be moving if there is no frame of reference to measure that movement against? What would it be moving in? Anything you can find to measure it against, or for it to be moving in, would, by definition, be part of it. And therefore not outside of it. Saying "the Universe is moving" is the same as saying "41 plus green equals tomorrow". You can say the words, but they are nonsensical in meaning.
quote:Think of it as an illusion caused by a combination of the distances involved and the way light moves.Astronomers where amazed to find data showed that some galaxies where moving away from us faster than the speed of light. Knowing that this wasn't possible they investigated more to find out what was causing it to appear that way. The culprit turned out to be the expansion of the universe. As the light was traveling towards the Earth, the distance it had to travel was getting larger and larger as the universe expanded. Not only were the galaxies traveling away from us with their own speed, but the actual space they were in was getting farther and father away due to the expansion of space between the galaxy and us. Think of two dots drawn on an uninflated balloon. As you blow up the balloon and the rubber stretches, the dots get further apart, even though they are stationary on the surface of the balloon. The Combination of the speed the galaxies were moving through space with the "speed" of the Universe's expansion produced the illusion that the galaxies were traveling faster than light. An example is an airplane flying in the jet stream. The plane is moving at 525 mile per hour on it's own. But the air in which it is flying is also moving at 200 mph. So even thought the plane is only moving at 525mph relative to the air around it, compared to the ground it's moving at 725mph, or faster than the speed of sound. (I've actually done this on a flight from Tokyo to Seattle.)On a personal note: Thanks for your reply. You made very good points and I enjoyed thinking about them while I was grocery shopping. I look forward to hearing any other thoughts you might have on this topic. Frankly I would love it if you could come up with something to show me that I am incorrect. I hope that doesn't come off as arrogant, it's not meant to be. This is just a topic that has fascinated me for many years and I have studied it extensively. So any new insights you might give me would be wonderful.
quote:As Ian (Soul Surfer) pointed out, rotation does create radial motion, and it does this because rotation is not steady linear motion, but in fact is continuous acceleration (i.e. the rim of a rotating object is constantly accelerating towards its centre). One consequence of this is the oblate shape of the Earth, that bulges out around the equator because of the outward force caused by the absolute rotation of the Earth. If the rotation was relative, and not absolute, then the shape of the Earth would have to look different to different observers, and a geostationary satellite (which sees no apparent rotation of the Earth) should perceive the Earth as a perfect sphere (aside from the surface topology).
quote: The problem is that with this you do not explain why one would be able to measure an increase in the increase distance between galaxies, but not measure the distance between you and the computer screen. The clear implication must be that the nature of the space between you and the computer screen must be behaving differently from the space between you and a distant galaxy. In other words, the space between you and the computer screen is not increasing, because the local forces are strong enough to overcome the expansion of space, but distant objects that are not so strongly bound, are indeed being forced apart by the expansion of space.
quote: A gravitational field extends for infinity, and yet has a centre, because it is not uniform.
quote:while one value (where A = 0) will not resolve into a value in either set.