IM Egdall

The universe is expanding as observed by cosmological redshift - faster than the speed of light, and the speed of expansion is increasing.

 

How exactly is this reconciled with the speed limit of C?

 

 

Here is a proposal:http://www.sciencefo...852#entry675852

There is no need to reconcile. Special relativity says nothing (no information) can travel faster than the speed of light through space. General relativity says there is no limit to how fast space itself can expand.

10 billion light years away? 3.7 billion years after the big bang, wouldn't we be looking at unevolved galaxies, it makes no sense to compare them to ours, or am I thinking wrong? Is this a new article? I feel like I've read this before,

Why can't the acceleration be like Christos Tsagas states, just an illusion, that way it would define that all forces would work the same way, still retaining dark flow and relativity would still be in affect, for this to be true I think all that needs to be changed is the existence of dark matter, don't we already know that dark matter isn't really there? i'm not too advanced in the Christos Tsagas area but it's still a possibility given my current knowledge of the universe but hey i'm no genius

Dark flow? Your words sent me on a google search. I found an article on testing with supernovas that seems to say this dark flow theory isn't right.

http://arstechnica.c...k-flow-mystery/

So I think dark matter and dark energy are still the favored theories of current mainstream physics.

Comments?

Ya, the "laws" of physics are time-symmetric -- they do not show a direction of time. But the 2nd law of thermodynamics is a different kind of law. It is a deduction based on probability. This is because the odds of a number of constituents being highly ordered gets dramatically lower as the number gets larger.

For example, if you have three cards -- Ace, two, three -and you shuffle them, the odds of drawing them in order are one in six. (3! = 3x2x1) But if you have four cards -- Ace, two, three, four, the odds of drawing them in order grows to 24 (4! = 4x3x2x1). With 10 cards, its 3,628,800. The odds very quickly become astronomical.

So the increase in entropy or disorder we see as a indicating an arrow of time is just a probability-based argument, due to the very large number of constituents in the macro world. It is not a physical "law" in the same sense as other physical laws.

I don't think there is anything new in these arguments.So I think the "possible solution" to the "paradox" is interesting but nothing new.

So astrophysicists performed a measurement fully compatible with mainstream physics that constrains the parameters of some not-further specified set of other models such that the extra parameters cannot have arbitrary values, anymore - unless the model is expanded by even more free parameters, of course .

 

My first thought is: Boring.

(but hey, that's just my personal first impression, and possibly due to not being familiar with the motivation for "5th force"-models in the first place)

Ya but no one knows what is causing the acceleration of the expansion of the universe. The most popular theory is the vacuum of space itself is somehow producing this outward push. And physicists model this mysterious "dark energy" by adding a cosmological constant to the right side of Einstein's field equations of general relativity.

Or maybe its Einstein's general relativity itself which is wrong at cosmic distances? Maybe there is some fifth force or other idea which accounts for the acceleration of the expansion.

I've heard these arguments for a number of years now. The link I gave is the first actual test I have come across which examines this question. And the test results tend to support general relativity. They point to this vacuum energy as the cause. I think this is a very big deal. And not at all boring.

Saw interesting article on testing dark energy and general relativity versus the idea that there is a fifth force affecting gravity out there. Seems like Einstein wins, at least so far:

http://spaceandearthsciencearticles.blogspot.com/2012/05/is-there-fifth-force-that-alters.html?spref=tw

Comments?

That percent of dark matter is obtained from the difference between the observation and the prediction done using GR. If instead GR you use some other theory, then you do not need dark matter to explain the observations.

Ya, I knew that -- its obvious. But do you know exactly what theory other than dark matter predicts the critical density needed for a flat universe without the use of dark matter? I need specifics, please.

Understanding that time is relative to the speed of an object or the gravity surrounding an object and that time will appear normal to an observer stood in the moment looking at his surroundings even on the event horizon of a black hole, the documentary said that if a spaceship were to travel at the speed of light to a planet say 10 light years away and back, that when the ship returned the crew would have experienced for 20 light years of time however during that time Earth would have experienced a thousand years.

Say the rocket took off into outer space and returned to Earth 1000 years later, as measured on Earth. This is 1000 years Earth-time for the round-trip.

If the rocket traveled at 99.98 percent the speed of light, then only 20 years will have elapsed for people on the rocket for the same trip. This is 20 years rocket-time.

The rocket's speed relative to Earth is what determines how much time slows down in rocket time versus Earth time. This is given by the time dilation factor:

square root ( 1 - v^2 ) where v is a percentage of the speed of light.

Here v = 0.9998 which gives a time dilation factor of 0.02, and 1000 years times 0.02 equals 20 years.

(Gravity effects on time are ignored, as they are a small effect here.)

I hope this helps.

How about the idea that the (observable) universe contains roughly 5% ordinary matter, 25% dark matter, and 70% dark energy. This sum gives the so-called critical mass/energy density needed for a flat universe (zero overall spacetime curvature). And observations show the observable universe is indeed flat. Analysis of the Cosmic Microwave Background is one example.

So if there is no dark matter (which I doubt), then the total matter/energy in the observable universe would be too little for the flat universe we see, wouldn't it?. It would imply an open universe of negative overall spacetime curvature. Does anyone know if MOND or any other theory has an answer for this? Or am I missing something here?

General theory of Relativity is considered to be beyond reproach and therefore generally accepted as correct, provides the reason why other concepts of gravity, however logical, unless provided by a well known Ph D, will always be ignored as pseudoscience. My 16 year attempt to have my 160 page work evaluated by those in academia has been met with only two replies thanking me for the offer but stating that they cannot spare the time.

In order to get the attention of the scientific community with your new theory of gravity, make a specific, detailed measureable prediction -- one which is different from general relativity (GR). If it explains current observations which disagree with GR, it should generate some interest. If it explains an observation which has yet to be made; once that observation is made and it agrees with your theory and not with GR, I think then it will really draw attention to your theory.

This is typically how any new theory gets recognized -- through measurements which verify its unique predictions.

Good article explaining the latest evidence putting dark matter into question:

http://www.newscientist.com/article/dn21732-nearby-darkmatterfree-zone-poses-cosmic-conundrum.html

I am not an expert in quantum mechanics, so please feel free to educate me here. I thought there are two basic ways to model in quantum mechanics.

In the first way, quantum field theory, a wave function travels from place to place. When an interaction occurs, the wave function collapses to a local wave packet of energy we can refer to as a particle. The wave function gives the probability of detecting this particle at a certain place and time.

The second method, Quantum Electrodynamics (QED), models particles as single points. The sum of all paths method is used to determine the probability that the particle is detected at a given place at a certain time. The probability amplitudes for each possible path the particle could take are summed, then squared to compute this probability. There is no wave in QED.

(Summing amplitudes from Feynman diagrams of interaction events and squaring is also a way to determine probability.)

The first method uses waves and wave mechanics. The second uses particles and the sum of all paths. I think they both give equivalent results.

Fine opinions above. If only we knew just what's inside that event horizon. Maybe some day we/they will.

 

However, one thing that frustrates me is how some geniuses have the audacity to claim that the singularity (condensed matter) inside the black hole is infinitely small -- or atomic -- in size. I'm not a rocket scientist, but that seems ridiculous! Something the size of an atom can affect an entire galaxy with it's gravity hole??? Right.

When a star like our Sun runs out of nuclear fuel, its core collapses to a white dwarf. The gravitational collapse is stopped by electron Fermi pressure.

For a star I think 4 to 8 times larger, the core collapse overcomes electron Fermi pressure to become a super-dense neutron star. The collapse is stopped by neutron Fermi pressure.

For even bigger stars, we know of nothing which can stop the collapse. So a black hole is formed.

For an idealized non-rotating black hole, all the mass of the black hole star's core is crushed into an infinitessimally small point. It may seem ridiculous to you, but this is our current best understanding. This "singularity" is a place-holder until a new theory combining general relativity and quantum mechanics gives us a better explanation.

The energy that was in the form of mass is converted to the energy of the photons.

You statement is how I always understood it.

Maybe this is quibbling with the words, but "energy in the form of mass" does not sound exactly like "an object of mass m contains simultaneously an energy E".

Hope this helps-

 

Extract from 'Concepts of Mass' by Max Jammer (year 2000)

 

"It is evident from many recent writings...that a serious misconception still persist, not only in the popular press but also in the minds of some scientists. The idea that matter and energy are interconvertible is due to a misunderstanding of Einstein's equation E = m[c squared]. This equation does not state that that a mass m can be coverted into an energy E, but that an object of mass m contains simultaneously an energy E".

 

So when an electron and positron interact, they can annihilate each other and give off energy in the form of photons. The mass of the electron and positron are converted to photons per E=mc2. Is this too simplistic? If we are to think of the electron and positron as having mass and energy simultaneusly, then the mass is destroyed in the interaction and the energy released.

Is this a correct interpretation of the physics?

Yes, we agree, timetravel is not ruled out. What I have been trying to say is that it is not ruled in either, it is still an open question.

Well put.

No, there isn't. That's a wikipedia article on a fringe subject. Those kinds of subjects tend to attract lots of cranks with lots of free time on their hands. Do not trust them. Wikipedia's quality has gone downhill as its popularity has increased. The main source of information from this article comes from Umberto Bartocci, an anti relativity and anti Einstein crank. There are lots of those cranks out there, and many of them have lots of free time on their hands. The premise of this group of nuts is "Relativity is wrong, and even if it isn't, Einstein didn't even come up with it." And that's leaving the ugly antisemitic bits out of their arguments.

 

Given any two physicists in Europe in the early 1900s and it is almost a certainty that a three degrees of separation connection can be found between them. Just because the connection existed does not mean that it has any meaning. It is pure happenstance that Olinto's brother's coworker's nephew worked in the same office as did Einstein.

Thanks for the info. Wikipedia or for that matter, other sites on the internet are not always reliable. I appreciate the heads up.

In any event, it was Einstein and only Einstein who came up with the mass/energy equivalence under the relativity construct. And that is what is most important (and most impressive).

Spayman: If by "assured possibility", you mean guarantee of time travel in physics, I agree. But as I said, physics hasn't ruled it out completely.

For example, see interesting time travel possibility using general relativity and quantum mechanics: http://physics.aps.org/story/v23/st18

But like the article says, we won't really know until we have a theory of quantum gravity.

Hmmm. It seems there may be something to this De Pretto and E=mc2. see link: http://en.wikipedia.org/wiki/Olinto_De_Pretto

Their internal timing tests have shown that the improperly-connected fiber caused around 60-70 ns of delay.

I read that an problem with an oscillator caused a problem in the opposite direction. Does anybody know by how much?

We aren't going to get a convincing argument for what happened before the big bang, because no one knows what happened before the big bang. Our current theory, general relativity, breaks down at time zero.

One possibility is that time and space began at the big bang, so there is no "before" before the big bang. This is pure speculation, but its fun to think about (though it boggles the mind.)

Some say there had to be a "before" before the big bang. Why? How do we know the true essence of space and time. It remains a deep mystery which, perhaps with new physics someday, we will have a better answer.

AFAIK there is no theoretical evidence that we should be able to travel backwards in time.

I donno. I thought the equations of general relativity do not rule out time travel. And quantum mechanics says particles can travel backwards in time.

That's crap put out by crackpots who for one reason or another want to knock Einstein down a notch or ten.

Who invented E=mc2? Found an interesting link. Apparently a German scientist named Fritz Hasenöhrl went part of the way. (This is like Lorentz and Poincare, who sent part of the way with other relativity ideas). But only Einstein took the full leap to relativity. See link: http://physicsworld.com/cws/article/news/2011/aug/23/did-einstein-discover-e-mc2

Of course

OK. Thanks for the clarification.

So if you walk down the road and return, your wristwatch will show that less time went by for you than the clock at rest on the road (assuming extremely accurate clocks). So more time has gone by on that spot on the road than time for you. So you return to that spot on the road a tiny bit into the future. (I think I got this right).

This kind of time travel is just what happens any time we leave a place and return to it. It's just that the effect is so small we don't notice it.

Whether finite or infinite is of no consequence, we do know that it cannot be bounded, Otherwise you need to account for the 'other' side of the boundary.

 

As for THoR's opinions that the universe is finite and positively curved, since its predicted by Newtonian gravity and the outdated Freidman model, perhaps he should also consider using General Relativty and alternative flat ( Euclidian ) or negatively curved models which are by definition infinite in extent.

3D space or 4D space-time has an intrinsic curvature, ie. it is not embedded in a higher dimensional space. Certainly not the 10 or 11 dimensions of the totally separate Sstring theory where the extra 6 or 7 dimensions are compacted Calabi-Yau manifolds.

Also when we speak of expansion we don't mean the boundaries are expanding, since THERE ARE NO BOUNDARIES,we mean separation between objects such as galaxies and galactic clusters is increasing.

I agree. And ThoR should consider the evidence. The Cosmic Microwave Background and other observations indicate the universe is flat. So infinite in extent.

(But this is evidence for the observable universe.)

Technically as you walk down the road, you are travelling back in time a small amount, wether we can abuse this fact is I feel unlikely, but still possible, I feel that this is a law that will not be easily messed with, but then you could say the same thing about the laws of electromagnetism and I'm sure they did back when they weren't fully understood I imagine we will not be able to abuse these laws for a good while yet tho as it will take very advanced spaceships to do so

Do you mean by moving down the road, your time is running slower than time for a clock on the road? In other words, time dilation?