IM Egdall

Before I reply to the others let's get this straight:

 

If I got into a spaceship and circumnavigated the Earth indefinitely at the near speed of light, the hands of the spaceship clock would run slow(Hafele-Keating experiment but quicker). Would I or would I not be virtually frozen in time? If not why not? The hands of the clock on the wall of the spaceship would be. Why shouldn't my hands be frozen in time? Are you saying thet biological systems "are not" affected by time dialation?

In your example, if you were on that spaceship cicumnavigating the Earth, the hands on the spaceship clock would be running normally as you see it. From your perspective on the spaceship, you are at rest and the Earth is moving. From your point of view, you are not virtually frozen in time.

But we on Earth see your spaceship clock running much slower than our Earth clocks and, as Swansont pointed out, your heart beating much slower. To us on the Earth, you appear to be virtually frozen in time.

You on the spaceship measure the hands on the spaceship clock running at a different rate than we measure from here on Earth. As strange as this sounds and as hard as it might be to accept it, this is what relativity is telling us.

So, Einstein views space-time as smooth. Long sweeping curves, like heavy objects on a wide sheet of stretchy rubber. However, WMAP has measured the curve of the universe and shown that over all, the universe is flat. Frankly, that makes no sense. With all this matter in it, space should have SOME sort of curve to it, either negative or positive, but no. It's flat. So, how is this possible?

 

The huge sweeping curves of Einstein's general relativity seems like a great deal of wasted, errr… "space". I mean, if you think about it, it has to be curving into SOMETHING. But the universe is flat. Yet space time curves. How can it APPEAR to be curving so much on a local level, yet be flat across the universe?

 

Observations indicate the observable universe is flat. But I think the entire universe -- which includes objects so far away their light has not had time to reach us yet -- may very well be curved. Inflation theory predicts the universe underwent an exponential expansion just after the big bang, making the region of the universe we see appear flat. (Sort of like blowing up a balloon to gigantic size so that an ant on the surface of the balloon sees the region it lives on as flat.)

I don't think anyone knows for sure what the curvature of the entire universe is.

Are you then saying biological systems function to a point of view in actuality?

Here's an example. Muons are a heavier form of electrons. They are unstable particles and only exist for a small fraction of a second before transforming into lighter particles. When they are made to go at speeds near the speed of light, e.g. in particle accelerators, they last much longer than they do when at rest. What gives these muons a longer life (as seen in the laboratory reference frame)? Time dilation. This increase in lifetime matches predictions of special relativity.

So here we have evidence for a subatomic particle and the relativitity of time. Since biological systems are made up of subatomic particles, this implies biological systems in uniform motion also experience slower aging as seen from a frame at rest.

Muon time dilation has also been verified in our atmoshpere. See link: http://home.fnal.gov...ght_page18.html

It would only be when travelling at extreme speeds approaching to that of light that the fact that the laws of physics are not the same in all rest frames becomes apparent. Time and matter actually run slow in the FOR of the spaceship travelling at a near light speed when time and matter actually run normally in the FOR of Earth.

Nah. The laws of physics are the same in any uniformly moving reference frame. Say you are in a rocket going at a constant speed of 99.9 percent the speed of light relative to me.

From your point of view, you and your rocket are at rest and I am moving by you in the opposite direction at 99.9 percent the speed of light.

But from my point of view, I am at rest and it is you who are moving.

Since in your reference frame, you are at rest, time for you goes by "normally." You see no effects of motion on the rate of passage of your time. But you see me going at 99.9 the speed of light. So from your point of view, my time is running much slower. (By a factor of 0.045X.)

What do I see? I see myself at rest, my time running normally, and your time running much slower by the same factor.

Whose point of view is correct? They both are. Time is relative.

Bell's theorem is a rather disturbing part of quantum mechanics. Basically, you can't have both locality (quantum mechanics is restricted by the speed of light) and scientific realism (The Moon is still there when you don't look at it). You have to discard one or the other, or both. Pick your poison.

 

So do you mean by this to say that per Bell's theorem experiments either:

1) Local but no scientific realism - the universe is local but a particle's variable attributes are not there until you "look at them", or

2) Non-local but there is scientific realism - the universe is non-local but a particle's variable attributes are there before you "look at them"?

I thought Bell's theorem experiments show the universe is non-local, period. And the interpretation using standard qm says there is no scientific realism -- a particle's variable attributes are not there until you look at them. However other interpretations like Bohm's qm are non-local but do maintain scientific realism.

Do I have this right?

After conducting his own analysis, skeptic physicist Richard Muller now convinced "global warming is real and humans are causing it."

http://www.scientifi...=SA_WR_20120801

Einstein's field equations of general relativity has proven to be the most accurate theory of gravity to date. And when it is applied to the universe as a whole, it predicts the universe is not static -- it must change size over time.

In 1928, I think, Georges Lemaitre combined Hubble's galaxy distance measurements with known redshiift data to show that in general the further away a galaxy is the more its light is redshifted. Lemaitre proposed this as evidence for the expansion of the universe as predicted by general relativity.

Observations of supernovae in 1998 and later observations show the expansion of the universe is speeding up over time. The cause of this acceleratation-- dubbed dark energy -- remains a mystery.

I hope this helps.

In the expansion of space, the distance between galaxy clusters is increasing. Does this mean there is more space between the clusters as time goes on? Yes. Thinking of space as a fabric is just an analogy, not to be taken literally.

I believe the NASA figure above is meant to show how the spinning of the Earth drags space around with it -- a phenomenon called frame dragging. In the Gravity Probe B satellite, a set of gyroscopes were set to point in a certain direction. Over time, they drifted ever so slightly. The average amount of drift agreed with frame dragging predictions (to about 20%, I think). Objects in "empty" space (gyros) were affected by the spinning of a distant object (the Earth). Another strange prediction of general relativity confirmed.

 

"A quantum mechanical explanation sees it as a meeting point of parallel worlds that normally exist separately. But an area of interpenetration could make objects and beings from one world cross over into another. "

 

http://www.lifeposit...da_Triangle.asp

 

I think this is a bunch of baloney. It uses physics terminology to justify pseudoscience.

Light always goes at the same speed, no matter what the (uniform) speed of the source of that light or the (uniform) speed of someone observing the light. This is Einstein's light postulate -- verified in countless experiments and tests.

Eisntein's light clock thought experiment shows that -- due to the light postulate -- time runs slower with relative motion. Take a look at this link:

http://galileoandein.../lightclock.swf

In the link, a photon (particle of light) in the left clock (Jack) goes up and down between the two mirrors of the light clock. Imagine that when the photon hits the top mirror, the clock goes tick. When it hits the bottom mirror, the clock goes tock. So we hear tick, tock, tick, tock.

Now set the speed dial above to say 0.87 c and press play button. The clock on the right (Jill) is now moving relative to you. But the photon in the right clock is unaffected by this uniform motion. So it goes at the same speed as the photon in the stationary clock on the left. But because the right clock is moving, the photon has to travel a longer diagonal path between the mirrors. Longer path at same speed means longer time. So the right moving clock goes tick . . . tock . . . tick . . . tock . . .

This is called time dilation. As you see it, time on the moving clock runs slower than time on the clock at rest. Numerous epxeriments and observations have verified this strange phenomenon. Time is relative!

I think the documentary was talking about speed through spacetime. This is a combination of speeds through space and through time. As I understand it, speed through spacetime is always c, the speed of light.

 

I would not say that the two theories are necessarily incompatible. The trouble is that standard tools built for the quantisation of field theories on Minkowski space-time do not allow us to directly quantise general relativity, at least not in perturbation theory.

 

The statement is that quantum general relativity in four dimensions is not perturbatively renormalisable. That is one cannot remove the infinities that arise when applying quantisation via perturbation theory, via the path integral formulation.

 

Canonical approaches also have troubles as the Hamiltonian theory has secondary constraints. For example in Loop Quantum Gravity it has not been shown that general relativity (+ small corrections) is the classical limit of the theory. Also, coupling the theory to other fields is problematic. Understanding gravitons is also very difficult.

 

String theory however necessarily contains the graviton in its spectrum and the classical limit here is known to be general relativity.

Thanks, ajb, for the enlightenment.

This article suggests its not the Higgs, but the top quark "super-particle" or stop squark. Seems a bit premature to announce it, but what do I know.

http://physicsworld.com/blog/2012/07/the_higgs_seven_days_on_what_h.html

Deosn't string theory propose that all fundamental particles are made of one-dimensional vibrating strings? And most strings are open-ended, so their ends stick to the "brane" that is our 3-d universe. But the strings for the gravity particle are a closed loop. They are not stuck to our universe but can travel to other universes. This, I think, is the general idea.

So since gravity particle strings, unlike other forces, can escape our 3-brane universe, this explains why it is such a weak force compared to all the others. And if gravity strings are free to travel from one universe to another, maybe they can be used to communicate between universes.

This is all speculation. So far, there is no substantive evidence which supports a prediction of string theory.

Sorry for the double post. Either I pressed submit twice, or its a post from a parallel universe.

Deosn't string theory propose that all fundamental particles are made of one-dimensional vibrating strings? And most strings are open-ended, so their ends stick to the "brane" that is our 3-d universe. But the strings for the gravity particle are a closed loop. They are not stuck to our universe but can travel to other universes. This, I think, is the general idea.

So since gravity particle strings, unlike other forces, can escape our 3-brane universe, this explains why it is such a weak force compared to all the others. And if gravity strings are free to travel from one universe to another, maybe they can be used to communicate between universes.

This is all speculation. So far, there is no substantive evidence which supports a prediction of string theory.

As I understand it, quantum mechanics and general relativity are based on fundamentally different views of nature:

1) General relativity assumes the universe is deterministic. For example, if you know the location of a particle and its velocity (speed and direction), you can know where it will be in the future (and where it was in the past) -- in principle to arbitrary accuracy.

But according to the Uncertainty Principle of quantum mechanics, you cannot know a particle's location and velocity simultaneously to arbitrary accuracy. The lower the uncertainty in one parameter, the higher the uncertainty in the other. Quantum mechanics says all you can do is predict the probability of where a particle will be in the future or where it was in the past.

But there is no Uncertainty Principle in general relativity.

2) According to general relativity, space and time (spacetime) are warped by mass/energy. There is no such warping of spacetime or spacetime curvature in quantum mechanics.

These differences are big reason why the two theories are not compatable.

I did read in "The End of Certainty" (by Prigogine) but he gives no further info/references. I found this link to a book with some more info:

 

http://books.google....ved=0CFkQ6AEwAw

Thaks for the link. Really cool discussion. I'd never considered that a star could have overall zero energy.

There is an inherent logic to the universe. That is why humans can construct mathematical equations to represent physical behavior. It underlies all the so-called laws of physics. This logic, I think, represents Einstein's "God".

This idea is named the free lunch cosmology. It is a plausible speculation.

 

 

 

Yes, although it seems that the original idea was by Pascual Jordan.

Do you know of a link to Jordan's idea?

I'd like to add my happy birthday wishes as well. I love this forum and have learned so much. Keep up the good work, staff and members!

For QM, just think of an observer as something that interacts with the system. If a particle hits a brick wall, the wall has "observed" the particle.

 

It's not a perfect analogy, but it's closer than the image most people bring up in their minds when they hear the word 'observer' used in quantum mechanics.

I think your explanation is really good. Some writers talk about this so-called quantum consciousness, as though you need a conscious observer to collapse the wave function to get a localized particle like an electron. But its really an interaction which results in the wavefunction collapse, and that, as you say, can be with a brick wall -- so human or other consciousness is not needed. At least that's my take on the subject.

CERN says it found a new particle and it is a boson. This alone is a remarkable achievement. But they say they need more analysis to know whether it is the Higgs boson predicted by the standard model of quantum mechanics or something more exotic. My bet is that it's the standard Higgs. See link:

http://physicsworld.com/cws/article/news/2012/jul/05/its-a-boson-but-what-sort

quote name='Seventh cavalry' timestamp='1340042139' post='685009']

I finished the book well, because i understood the theory briefly before i read it, i can't understand the old theory that dominated the physics in 1800s the ether wind theory. So can some good people help me understand it ?

In the nineteenth century, physicists believed that electromagnetic radiation (like visible light) had to propagate through some kind of medium -- which they labeled the ether. (Just like sound must travel through some kind of medium like air. In a vacuum, there is no sound.) They believed this ether permeated all of space.

But in 1905, Einstein declared that there is no ether -- electromagnetic waves travel through empty space.

and last question, in the book it stated that in a space ship traveling at high speed, lets say 50% speed of c. lets say the ceiling and floor of the rocket is parallel, and a light bulb's from ceiling is going down strait. and reflect up. and it said 2 observer is different. The guy inside see a light go down and up | just like this, but someone out side not moving will see the light go like this \ and reflect up / Yes i understand because the space ship is moving at the same time, but it is because that the time is passing slower for him but the light is constant so this is possible or opposite ?

 

I think the idea is this. Light always travels at the same speed, c (about 670 million miles an hour). This leads to time dilation:

From the view of someone inside the moving rocket, the light beam goes from the ceiling to the floor and back in a straight vertical line.

But to someone at rest outside the moving rocket, the light beam must take a diagonal path to go from the ceiling to the floor and back to the ceiling. And this diagonal path is a longer path. But the light is still traveling at c. So the light traveling at the same speed takes a longer time to go from ceiling to floor to ceiling. Thus to the person at rest outside the moving rocket, time is running slower on the rocket (than for the person inside the rocket).

I hope this helps.

I've gotten into this before and don't really want to again, nor do I want to derail the thread; however, I feel obligated to point out that what you're saying here is patently false.

 

The equivalence principle is certainly present in GR, and is in fact one of its core principles. It is equivalent to the statement that spacetime is locally flat and the "comma-goes-to-semicolon rule" which is mentioned in many GR texts. The EP itself does not yield bad predictions - it is the EP + Newtonian gravity which does so.

Question: I have read that an acceleration produces only half the bending of light of an equivalent gravitional field. For example, consider the famous accelerating elevator in zero gravity with a light beam traveling across the elevator. An observer outside the elevator sees the light bend due to the elevator's acceleration. But the amount of bending is only half what one would measure for a light beam in an elevator at rest in a gravitational field of the same magnitude.

Doesn't this say the Equivalence Principle fails? I'd appreciate your thoughts.

Ref: Ohanian, Einstein's Mistakes, p. 226.

So there is no limit to how fast space-itself can expand? Can space expand at infinite rate?

Hmmm. Interesting. Recent observations say the expansion of space is accelerating. No one knows what is causing the expansion to speed up -- its been given the name dark energy. If we assume this mysterious dark energy stays the same over time (a big assumption since we don't know what it is) and we assume the universe will exist for an infinite amount of time, then I guess this says the expansion of the univere will reach an infinite rate.

Have I missed something here? Comments?

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