IM Egdall

I think you are describing (at least in part) the Lamb shift. Electrons in atoms "jiggle" due to their interaction with virtual particles. This results in slight energy changes and shifts in spectral lines.

I believe it works like this: Say Tina Top is at the top of the hole, and Barry Bottom is at the bottom of the hole. Time for Barry runs slower than time for Tina because gravity is stronger at the bottom of the hole. So Tina Top sees Barry Bottom moving in slow motion. Conversely, Barry Bottom sees Tina Top moving in fast motion. And there is a light effect. The slower time at the bottom is equivalent to longer light frequency. (The regular up-down motion of the light's electromagnetic wave is a kind of clock.) So Tina Top sees light from the bottom shifted towards the red (longer frequency). And conversely Barry Bottom sees light from the top shifted towards the blue (shorter frequency).

Take a look at the link below. It gives a detailed explanation of the so-called Twins Paradox. Hope it helps. Go to : http://www.marksmodernphysics.com/ then click on Its Relative, archives, The Twins Paradox.

To clarify further, per E=mc**2, mass and energy produce equivalent physical effects. The presence of mass produces a gravitational field. And the presence of energy (e.g. photons) also produces a gravitational field.

I believe "the universe is flat" refers to the overall spacetime curvature of the universe. This in turn is determined by the overall mass/density of the universe. Estimates of the overall density of the universe (and other observations) say that it has just the right amount to produce a flat spacetime curvature. This is called the critical density. But this refers to the VISIBLE universe, that is the universe we can see. I think physicists believe the universe we cannot see is most likely curved (overall non-zero spacetime curvature). This flat visible universe is attributed to the exponentail expansion of the very early universe called inflation. See link: http://en.wikipedia....tion_(cosmology)

Brian Greene's The Elegant Universe is mostly about string theory, but has a chapter on special relativity and one on general relativity. They are excellent introductions to the subject for the lay reader (but way to brief).

Einstein's light postulate says that the speed of light is the same for all observers. In other words, no matter what speed the source of that light is going at, no matter what speed you are going at; you will always measure the speed of that light as the same value, about 671 million miles an hour (in a vacuum). This is the core principle behind special relativity. In his famous 1905 paper , Einstein proposed this light postulate. And then he came up with a new transformation formula to go from at rest to uniform motion. It is called the Lorentz transform because unbelknownst to Einstein, Lorentz and others had already come up with the formula (but didn't understrand its physical significance). Anyway, then in 1908, Einstein's former math teacher Minkowski took the Lorentz transform and from it, came up with the formula for the spacetime interval. So to make a long story short: the light postulatre leads to the Lorentz transfom, which leads to the spacetime interval. Why the minus sign? Because that is what comes out of the Lorentz transform mathematics. See links: http://galileo.phys.virginia.edu/classes/252/lorentztrans.html If link doesn't work, google Michael Fowler Lorentz transform

Correct. The big bang theory is an explosion of space itself. Where in the unverse did the big bang happen? Here, there, and everywhere. Think of blowing up a balloon. In this analogy, the balloon's surface represents the universe. Where is the center of that surface? There is no center. There is no single location on the balloon's surface which the balloon is expanding from. No matter where you are on that balloon's surface, you see the surface around you expanding. Similarly, there is no center of the universe. No matter where you are in the universe, you see intergalactic space around you expanding. Hope this helps.

If you want to convince most scientists that Intelligent Design is to be preferred over Evolution theory; make a prediction. That is, using so-called Intelligent Design theory, make a specific prediction that is not found in Evolution theory. Then once an independent scientist validates this prediction by observation and measurement (and this proves repeatable by others); then scientists will stand up and pay attention to the new theory. This is generally how science works. Scientists are skeptical. The reason why they overwhelmingly support the ephicacy of evolution is because of all the evidence supporting it. I suggest you read Finding Darwin's God by Kenneth R. Miller. It supports evolution and the existence of God. I found it quite interesting. He argues that evolution still fits within God's plan. Whether you agee with Miiler's point of view or not, you have to admit his arguments for evolution are most compelling.

Spyman is correct. Per special relativity, how fast you age depends on your relative motion. But you still age. Time still moves forward, albeit at a different rate (depending on relative motion). So this particular effect is a one-way trip forward in time.

In the over 100 years since Einstein first proposed his light postulate, literally "thousands of scientific observations" have confirmed its validity. In one example, a vastly more accurate version of the famous de Sitter experiment was performed by MIT physicist Kenneth Brecher in 1977. His tests using Uhuru satellite images of X-ray pulsars verified Einstein's light postulate to one part in a billion! See link to his article: http://www.ekkehard-friebe.de/Brecher-K-1977.pdf References: Victor J. Stenger, Quantum Gods, Creation, Chaos, and the Search for Cosmic Consciousness, p. 74. Nigel Calder, Einstein's Universe, The Layperson's Guide, p. 176-178.

It's like the famous time travel conundrum: You travel to the past to before you were born and accidentally kill your mother. So if you did, then you don't exist in the future. But if you don't exist in the future, you couldn't have gone back to the past to kill your mother. But then you do exist. But if you do exist, you did go back to the past and kill your mother . . . Etc. Etc. So is there a fundamental law of physics which prevents time machines? Or one which permits time machines but somehow prevents altering the past? I don't think any physicists has an answer. Or at least she/he doesn't have one which has been verified by empirical evidence. I like Hawking's comment that there is empirical evidence that time machines are not possible. If they were, we would be visited by tourists from the future. By the way, according to special relativity, we experience time travel into the future (in tiny amounts) all the time. See link: http://www.marksmodernphysics.com/index.html and click on Its Relative

A little history: Before Einstein Galileo's dictum in effect said that there is no way to tell internally whether you are in uniform motion or at rest. Uniform motion is relative. Physicists used the so-called Galilean transform equation to go from at rest to moving uniformly. Newton's laws of motion obeyed Galileo's dictum but Maxwell's equations of electromagnetism did not! In other words, Maxwell's equations were different for inside a moving vehicle than for inside one at rest. This impied that electromagnetism behaves differently when a vehicle is moving uniformly. This, of course, is not true. This was a great puzzle to physicists. After Einstein Einstein came along in 1905 and proposed that light always travels at the same speed (in vacuum), regardless of the motion of the source of that light or the motion of any observer. From this absolute speed of light postulate, Einstein then came up with a new transformation equation for relative motion. It showed that Maxwell's equations now do obey Galileo's dictum. It also meant that Newton's laws of motion had to modified when speeds approach the speed of light. Einstein didn't know at the time that his new transform equation had already been developed by Lorentz (and others). So it is called the Lorentz transform. (But Lorentz did not understand its full physical significance.) The point is that Einstein took Galileo's dictum on relative motion and extended it to electromagnetism. Einstein then declared that Galileo's dictum applies to all physical phenomena. So Einstein took Galileo's dictum and made it a universal law. And yes, all of special relativity comes from Einstein's light postulate. Reportedly, Einstein did not like the name "relativity" for his theory. He preferred it be called "invariance" theory, because the speed of light does not vary.

Historically, the matter which is abundant in the universe (including here on Earth) was called "matter". Then a new form of matter with opposite electric charge was predicted (by Dirac) and discovered (in the 1920's I think). It was called "antimatter", and is very rare. These are only names made up by humans to label these things. But the fact remains that what we call "matter" is abundant, and what we call "anti-matter" is very rare. So the differentiation does matter! (Matter matters?)

Terrific link. Thank you!

Now I'm doing a reply to my reply. This thing has really got my interest! I did a google search on "Flat Universe Net Zero Energy" and the results were consistent. It appears, as Spyman said, that the net zero energy universe IS for a net flat curvature universe. But per inflation theory, the reason we see a flat observable universe is because the highly curved overall universe expanded exponentially moments after the Big Bang (inflation). So its like blowing up a balloon to stupendous size. We ants on its surface see only a very small portion of this balloon. And so, to us, the part we can see appears to be flat. But the entire balloon universe is still highly curved. So the net energy of the entire universe IS NOT ZERO. All these conclusions from Hawking and others is based on only the portion of the universe that we can see. So Hawking's proposal does NOT apply to the entire universe. Is there something I am missing in my argument?

Could you please give us a link to these recent experiments?

Thanks, Spyman. If your guess is right; then, as I said, then maybe Hawking is wrong. The visible universe is flat, but cosmologists think the entire univere is most likely highly curved (see earlier link). I wonder what the balance or non-balance of gravity and matter/energy is in a highly curved universe?

The fact that the observable universe happens to appear flat is a very unlikely outcome. Physicists were at a loss to explain why this so unlikely outcome of nearly zero net spacetime curvature is so. Until Guth's inflation theory. Guth's theory says that the universe expanded exponentially about 10**-32 seconds after the big bang. This great expansion is given as the reason why we see a flat universe. Even though the entire universe is most likely not exactly flat, the expansion makes the region we see flat. It is like on the Earth. The Earth is curved , but an ant on a football feild thinks that it is flat because he/she is seeing only a very small portion of the curved surface. Per Wikipedia link http://en.wikipedia....tion_(cosmology) : "As a direct consequence of this expansion, all of the observable universe originated in a small causally connected region. Inflation answers the classic conundrum of the Big Bang cosmology: why does the universe appear flat, homogeneous and isotropic in accordance with the cosmological principle when one would expect, on the basis of the physics of the Big Bang, a highly curved, heterogeneous universe?" So that's my point. The observable part of the universe is flat. The entire universe is most likely highly curved. Is Hawking's net zero energy of the universe concept based on a flat universe? If so, it is wrong, because only the part of the universe we can see is flat. THe entire unseen universe is most likely highly curved. I need help hear to know whether Hawking's idea on zero net energy is based on a flat universe or if it has nothing to do with it. You are standing on the sidelines observing the surface of a football field. It appears flat. This is your observable universe. You conclude the entire Earth is flat. But the entire Earth is highly curved. And if you rise high into outer space, you see the entire Earth and know it is not flat. Similarly, the entire unobserved universe may or may not be flat. In fact, cosmologists believe it is highly curved.

I understand all that (or at least I think I do). But here's my point. Visible Universe: Observations tell us that the overall spacetime curvature for the visible universe is zero, i.e. a flat configuration. This says that the overall gravitational energy is balanced by rest of the overall mass/energy. But what we observe is a tiny portion of the overall universe. Unobserved Universe. The unobserved universe beyond what we can see may or may not be a flat configuration. It could have a net positive or net negative spacetime curvature. In fact, a non-zero curvature is most likely. So the unobserved universe most probably does not have a flat configuration. (It is closed or open.) Does this say that for the overall unobserved universe, gravitational energy does not balance the rest of mass/energy? That is my question. Am I oversimplifying here? Please advise.

Ya, I think that's it! Thanks. (I love this forum) Oh, I have another point to discuss. So the total amount of gravity (spacetime curvature) in the universe is equal to the total amount of mass/energy in the universe. Here by mass/energy I mean all the matter (ordinary and dark) and all the energy (including dark energy). Is this because the overall mass/energy density of the universe is the so-called critical value; implying a flat spacetime curvature? But here we are talking only about the observable universe. Per inflationj theory, our visible universe looks flat (and nearly uniform) because it is a miniscule part of a much much greater universe which expanded exponentially just after the big bang. So my question: Hawking is saying that this overall gravitation energy (negative) of the universe equals the overall mass/energy of the universe (positive); so the net energy is zero. Does this apply only to the observable universe or the entire universe? And if it applies to the entire universe, how do physicists know about something beyond what we can observe? What extrapolation are they making? Any thoughts on this would be greatly appreciated.

Physicists theorize that there must have been a very slight excess of matter over antimatter immediately after the big bang. Based on rough estimates of the number of photons in the microwave background and the number of protons and neutrons in the universe today, scientists estimate that for every billion antiparticles, there must have been a billion plus one ordinary particles, leaving a single particle per billion to survive after annihilation. This single surviving ordinary particle per billion is what makes up our universe today. The reason for this asymmetry is a subject of ongoing research. Some physicists attribute the existence of slightly more matter than antimatter in the very early universe to a slight asymmetry discovered by analyzing the properties of subatomic particles. This so-called Charge-Parity (CP) violation was found in the decay of neutral kaons by James Cronin and Val Fitch, then of Princeton University in 1964. Neutral kaons are made up of a down quark and an anti-strange quark; or the reverse, a strange quark and anti-down quark. (Ref:: Michio Kaku, Physics of the Impossible, p. 192.) However, the current Standard Model of quantum mechanics fails to fully predict the matter-antimatter results we see in today’s universe. There are only two ways to break CP symmetry per the Standard Model. The first is the so-called Quantum Chromodynamics (strong force) Lagrangian. It has not been found experimentally, and leads to no CP violation or one that is much, much too large. The second theoretical way to violate CP symmetry involves the weak force. It has been found experimentally (in the neutral kaon and B meson experiments discussed above). But here the theory accounts for only a small portion of the CP violation we see; “sufficient (only) for a net mass of normal matter equivalent to a single galaxy in the known universe”. (Ref: Wikepedia.org) I don't see what this has to do with black holes; but maybe its possible.

OK, so what does this so-called instability at cosmic scales have to do with Hawking's point that the universe can be created out of nothing?

Another question on Hawking and Mlodinow's book, The Grand Design. On page 180, they state: "Because gravity is attractive, gravitational energy is negative . . . This negative energy can balance the positive energy needed to create matter." Then they state: "Because gravity shapes space and time, it allows space-time to be locally stable but globally unstable. On the scale of the entire universe, the positive energy of the matter can be balanced by the negative gravitational energy, and so there is no restriction on the creation of the entire universe." I understand that per general relativity, gravity is a global effect. Because gravity (spacetime curvature) is effectively uniform in magnitude and direction over a local region of spacetime, one cannot detect the effects of gravity locally. That is over a small enough space and over a small enough time. Here all particles experience the same acceleration amount and direction. So in the reference frame of one of these particles. all other particles in this local region are at rest. But globally, the magnitude and/or direction of gravity does change, so we can detect its effects over a global region of spacetime, e.g. tidal forces. But what do they mean by "spacetime is locally stable but globally unstable? Please enlighten me.

Take a look at the wikipedia link: http://en.wikipedia.org/wiki/Relativistic_Doppler_effect Hope it helps.