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IM Egdall

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Everything posted by IM Egdall

  1. We all perceive the world within the limitations of the human mind. But I still think there is a big difference between theory and observation. Someone comes up with a new theory. It may or may not reflect reality. Then someone else independently conducts tests which determine that the predictions of the new theory agree with observations (to a significant level of accuracy.) The test is then repeated by yet someone else. And then more and more predictions of this new theory are substantated by additional observations by yet more people. After a while, you have to admit that this new theory has some merit. It must reflect something about reality. The chance that all these independent observervations are mistaken due to mental illness or something else is highly unlikely. Repeated, detailed, independent observations allow us to peek behind the veil of human perception and give us a glimse at reality.
  2. But there is no absolute time. It is different for everyone and everything in motion with respect to everything else. It is different depending on location in a gravitational field. So this means an infinite number of time dimensions? And space is also affected by motion and the presence of mass/energy. For example, space on the surface of the Earth is warped more than space above the Moon (in the radial direction)because of its greater mass/energy density. Because of this, in the theory does space also have an infinite number of dimensions?
  3. You say "the further back in time we look the faster objects were receding." The object is NOT receding. The space between the object and us is expanding. This is a fundamentally different point of view which must be taken into account to understand what's going on. So why is there a cosmic red shift? Because expanding space stretches all light waves they propogate, not because receding galaxies are moving though space and exhibit Doppler shift. REF: C. H. Lineweaver, T. D. Davis, "Misconceptions about the Big Bang", SciAm Mar 05 In fact, "galaxies, on average, hardly move through space at all.Their motion is due almost completely to the stretching of space itself." REF: B. Greene, The Fabric of the Cosmos, p. 237.
  4. I think the word "theory" confuses the public, because it is used so generally. For example, quantum theory and the theory of general relativity have survived nearly a hundred years of rigorous testing. The predictions of these two theories have been examined in thousands, maybe millions of actual experiments and observations. And results show extraordinary agreement between prediction and measurement. But string or M-theory has been around for what 30 or more years, and there is still no single compelling piece of evidence to support or refute it. But it too is called a theory. Yes, technically you can't "prove" a theory. This would require testing it for all possible conditions, which is an infinite number; thus impossible. But certainly some theories have been experimentally tested to great success. Others can make no such claim. We need a different word for the two types. (and for those in between that have some empirical support.) Any ideas?
  5. Huh? Why dark matter and not ordinary matter? Do you have a link which explains how this theoretically would work?
  6. I know that time dilation doesn't happen only in the acceleration phase. If you look at my prior post (and link) on the twins paradox, you'll see that time dilation occurs during the entiire trip. But the reason the traveling twin is the one who shows the slowing of time (and not the stay at home twin) is because only the traveling twin has experiences acceleration (when she turns around to head back to the Earth). And acceleration is both a change in speed and/or change in direction. The traveling twin does both when she turns around to return to the Earth. So I think we agree here.
  7. Electrons (and every other type of particle) have both wave-like and particle-like behavior. An electron travels from place to place like a wave, but interacts (is detected) like a particle. Say a single electron is emitted from an electron gun It spreads out like a wave. Say we have a whole series of electron detectors spread out to detect this electron-wave. Only a single detector "clicks". That is only a single detector registers the location of the electron from that gun. And if we repeat the exact same experiment, we find the single electron experiment is not repeatable. Each time we do it, the electron can show up somewhere else. No one can predict exactly which detector will detect the electron at any given time. Physicists can only predict the probability that the electron will be detected by a certain detector. Nature's inherent uncertainty limits us to only a statistical prediction. And this single electron can interfere with itself. Why? Again because the electron travels like a wave. That is until it is detected. Then it is found as a local clump of energy.
  8. Say Al is moving uniformly (at a constant speed and in a constant direction) with respect to Betty. From Al's point of view, he is standing still, and Betty is moving. So Al sees his clock running normally and Betty's running slower. From Betty's point of view, she is standing still and Al is moving. So Betty sees her clock running normally and Al's running slower. Now let's say Al is stationary on the Earth and Betty takes a rocket flight at 87% the speed of light into outer space and back. Al's clock on Earth says that 10 years have passed from the time Betty left Earth and returned. Per special relativity, Betty's clock on-board the rocket says that only 5 years have passed for her round-trip. So it is Betty and only Betty who experiences the slowing of time (by half). Why? Because it is Betty who has experienced acceleration, On her trip, she had to turn-around to return to Earth. Duiring this turn-around, she undergoes a change in speed and direction or acceleration. So Al has in the same inertial (uniform motion) reference frame. But Betty has been in two inertial reference frames; one going outbound and another coming back. (They can't be the same inertial frame because they are going in opposite directions.) This is why it is Betty whose time is slowed and not Al. When they meet again back on Earth, Betty will have aged 5 years but Al will have aged 10 years. Please read the link I mentioned earlier for details. Again it is: http://www.marksmodernphysics.com/Mark's%20Modern%20Physics/Musings/Musings%20-%20The%20Twins%20Paradox.doc
  9. Imagine a beam of light on the left going through a slit, then hitting a screen on the right. Say you make the slit narrower and narrower. Now the narrower the slit, the more accurately you know the location of the light at the slit. But as you narrow the slit, the diffraction pattern on the screen gets wider and wider. This means that where the light from the slit is going becomes less and less certain. In other words, the better we know the location of the light (at the slit), the less we know its direction. This is Heisenberg's Uncertainty Principle in action.
  10. I also found it hard to believe that time slows down with motion when I first read about it. I suspect most everyone does. But we know from experiments with atomic clocks on airplanes, on rockets and in satellites that time does really slow down with relative motion. We also know this from the measured lifetimes of subatomic particles in our atmosphere and in particle accelerators. Yes, this so-called time dilation is crazy. Yes, it violates our common sense; but it's true! I like what the famous physicist Richard Feynman said (he said it about quantum theory, but I think it also applies to relativity): "Mother Nature doesn't care whether we believe it or not, this is how She works." And yes, this relative slowing of time due to motion implies time travel. In fact, we do it all the time! It's just such a tiny effect at every day speeds that we don't notice it. See link: (IF LINKS DO NOT WORK DIRECTLY, COPY THEM AND PASTE THEM DIRECTLY. ON YOUR BROWSER. THEN THEY WILL WORK) http://www.marksmodernphysics.com/Mark's%20Modern%20Physics/Musings/It's%20Relative.html All experiments show that it is the object which accelerates which undergoes the relative slowing of time. See link below for detailed explanation: www.marksmodernphysics.com/Mark's%20Modern%20Physics/Musings/Musings%20-%20The%20Twins%20Paradox.doc Hiope this helps.
  11. If the universe where really like a room; there would be a center and an edge. But per general relativity, space has no center, no edge. As a commonly used analogy, think of the surface of an expanding balloon. The universe is represented by the surface (and the surface only). There is no center to the surface of the balloon. There is no beginning or end to the surface of the balloon. Everywhere on the surface is like everywhere else. That's the way we are told to think of our very strange universe. I hope it helps. Also, observations of Type IA supernovae tell us the expansion of the universe is accelelerating. And this speed-up started some five to seven billion years ago.This is usually attributed to an unknown repulsive force labeled "dark energy". Assuming that dark energy continues to exist in the same amount in the future (a big assumption since we don't know what it is), the universe will not eventually collapse. It will expand forever. REF: "Dark Energy", Physicsworld.com, May 30, 2004. http://physicsworld....cle/print/19419.
  12. I agree that locking down the various frames of reference is key. May I suggest you consider the Earth and the other planet as stationary with respect to each other for simplicity. That way thay are in the same reference frame. So there are now two frames: 1) The Earth/other planet reference frame. and 2) The light (photon) reference frame. Say the Earth and the other planet are one lightyear apart (in the Earth/other planet frame). (And think of only sending a single photon, again for simplicity.) From the Earth/other planet reference frame, the photon (message) is emitted by us on Earth at time zero. One Earth year later, this photon is received by the other planet. Aliens on this other planet then send their return message (another photon) to Earth. One more Earth year later (year 2), the photon is received back on the Earth. Because the Earth and other planet are in the same reference frame, there is no time dilation or length contraction. (No relative motion so no shrinking of time or space). From the initial photon's reference frame, it is standing still and the Earth and other planet are moving at the speed of light. So the photon sees the ultimate time dilation and length contraction. From the photon's point of view, the distance between the Earth and the other planet has contracted to zero. From the photon's point of view, it travels from the Earth to the other planet instantaneously! Any photon going from place to place (in a vacuum) goes at the speed of light. Thus for it, time is frozen (it never ages) and all distances are contracted to zero.
  13. In the the nuclear furnace in the core of the Sun, through a multi-step process, 4 hydrogen nuclei (4 protons) are converted into one helium nucleus (2 protons and 2 neutrons) plus photons (and neutrinos.) The mass of the four initial hydrogen nuclei is 6.693x10-27 kg. The mass of the resultant single helium nucleus is 6.645x10-27 kg. So there is a mass loss of 0.048x10-27 kg in the process (roughly 1 percent). This lost mass is converted to energy via E = mc2, resulting in 6 high energy gamma ray photons. (REF: R. A. Freedman and W. J. Kaufmann II, Universe, p. 392)
  14. This ladder paradox is a tricky thing. I find pictures of what's going on really help me. Take a look at: http://en.wikipedia.org/wiki/Ladder_paradox From the barn's point of view (reference frame), the ladder is moving. So the ladder is contracted or shorter in length. So the ladder fits inside the barn. So both barn doors can be shut at the moment the ladder is inside the barn. And then they both open to let the ladder out. But from the ladder's point of view, the barn is moving. So the barn is contracted or shorter in length. So how does the ladder fit inside this shorter barn? It doesn't in this reference frame! And in this reference frame, the shutting of the doors is not simultaneous. Einstein's relativity of simultaneity says that two events which occur at the same time for one observer do not happen at the same time for another observer in relative motion. So in the ladder reference frame, the front of the ladder goes to the back of the barn and the back door is closed. Then the back door is opened and the ladder goes through the barn. When the back of the ladder is just inside the barn, the front door is closed. Then it is opened. Both doors close at the same time and then open at the same time from the barn's poiint of view. But from the ladder's point of view, the rear door closes and opens, then at a later time the front door closes and opens. So no contradiction. Einstein escapes again. Relativity of simultaneity is invoked to explain length contraction. This stuff is beautiful!
  15. See the following link for an explanation of how light (photons) heat an object. http://www.scientificamerican.com/article.cfm?id=how-exactly-does-light-tr
  16. Yes, the core of the Sun produces gamma ray photons. But, as a result, the surface of the Sun gives off photons in lots of lower frequencies. That's why we see ultraviolet, visible, infrared, and other frequencies of photons radiated by the Sun. The nuclear furnace in the core of the Sun fuses hydrogen nucleii into helium nucleii, and gives off gamma ray photons in the process. Where do all these gamma ray photons go? Initially they are absorbed in only a few millimeters of solar plasma surrounding the Sun’s core. They are then re-emitted in random directions (and at slightly lower energies). This continued absorption and re-emission continues throughout the Sun until lower energy photons finally reach the Sun’s surface and are emitted into space as solar radiation. A photon from the Sun’s core scatters a stupendous number of times on the way out; on the order of 1020 times. Scientists estimate that it takes 10,000 to 170,000 years for the radiation from the core of the Sun to reach the surface. This means that the sunlight we see in the sky today began in its core somewhere between the appearance of the human species some 170,000 years ago and the end of the last Ice Age in 8000 BC! <BR clear=all> B. Schutz, p. 128
  17. Think about it this way. An object very far away emits some light. Because the object is so very far away, it takes a considerable amount of time for that light to reach us here on Earth. During that time, the universe has expanded. So the frequency of that light has been stretched by the expansion! (And lower frequency is movement towards the red end of the spectrum or red-shift). The object (galaxy) very far away is hardly moving with respect to us (on a cosmic scale). So its red-shift is not due to its motion, but due to the expansion of space itself. In other words, when we see the red-shift of the light from that distant object today; it is not because it is moving away from us, but because the space between the object and us has expanded during the time it took for its light to reach us.
  18. Unfortunately, physicists use the same word "theory" for something that has loads of supporting empirical evidence, as well as for something that has virtually none (like quantum theory and string theory, respectively). But I take umbrage with your referring to the Big Bang as just a hypothesis or idea. It is a theory substantiated by an impressive set of independent observations. To quote from a book I am writing on relativity for the lay person: "Today the big bang theory is widely accepted by physicists as the best current explanation for the geometry, composition, and history of the universe. Why? Because a number of measurements from vastly different observations agree with modern big bang theory predictions (to a precision of 10% or better). This is a most remarkable agreement, considering the measurement challenges and the fact that we are talking about something that began some 13.66 billion years ago. Current evidence for the big bang includes: 1) the homogeneity of the universe 2) the expansion of the universe 3) the amount and abundance of helium and other light elements in our universe 4) the Cosmic Microwave Background and the fluctuations in the CMB 5) the large scale structure of the universe 6) the age of stars 7) the evolution of galaxies, and 8) a number of other more esoteric measurements. (<BR clear=all> B. Feuerbacher and R. Scranton, "Evidence for the Big Bang", The TalkOrigins Archive, Jan. 2006. http://www.talkorigi...#smallstructure
  19. Here is the simple but strange quantum rule. In the double-slit experiment (and others like it): If you can, in principle, detect which path the photon takes, then there is no interference If you cannot, in principle, detect which path the photon takes, them there is interference. This rule applies not only to photons, but to all particles. And every experiment conducted to date has confirmed this law of nature. I found the following simulation a real help in visualizing what happens: http://phet.colorado.edu/en/simulation/quantum-wave-interference
  20. May I suggest you read QED, the Strange Theory of Light and Matter by Richard Feynman. It is a clear explanation of his Quantum Electrodynamics theory for the layperson. Step-by-step, Feynam's lectures explain the heart of quantum theory with a few basic rules, arrow drawings, and no math. It will blow your mind!
  21. Calculations show that measuring the radius on which an electron travels provide a direct measurement of it momentum (as long as the magnitude of the magnetic field and the charge of the particle are known). So there is no need to measure the intial position of the electron. The details are given in Jonathan Allday, Quarks, Leptons, and the Big Bang, p. 23: The calculation is: "To move an object of mass, m on a circular path of radius r at a speed v, a force must be provided of size: F = (mv**2 ) / r where m = mass of particle , v = speed of particle, and r = radius of its path In this case, the force, F is the magnetic force exerted on the charged partiicle F = B q v where B = size of magnetic field and q = charge of particle therefore B q v = (mv**2) / r making r the subject: r = mv / B q or r = p / B q where p is the momentum of the particle. Equally: p = B q r
  22. I think Hawking is basing his "no God required" hypothesis on M-theory (formerly known as string theory). What most of the public do not realize is that despite its great potential, there is no single piece of clear empirical evidence to support or deny M-theory's numerous predictions. So as of this writing, it is pure speculation. As Brian Greene put it, " . . . these (new quantum gravity) theories may or may not have relevance in the real world." So I would say that Hawking's declaration is premature, to say the least. And whether it really has anything to do with the existence of "God" is another question. But it does sell books!
  23. I agree. As I understand it, Enstein's 1905 interpretation of the photo-electric effect just said that photons are absorbed as discrete particles (later called photons) whose energy is proportional to frequency per Planck's E = hv. It really says nothing about how light is propagated through space. (The idea of a wave function and its collapse wouldn't come, I think, until the 1920's.)
  24. To understand what is going on in the Twins Paradox, I find it helpful to look at a picture. Also experiments in particlel accelerators verify that time indeed does slow for the "twin" who has undergone acceleration. See for example http://marksmodernphysics.com/Mark's%20Modern%20Physics/Musings/Musings%20-%20The%20Twins%20Paradox.doc Sorry. Link has to be on separate line http://marksmodernphysics.com/Mark's%20Modern%20Physics/Musings/Musings%20-%20The%20Twins%20Paradox.doc
  25. And energy is proportional to frequency (E = hV). So then a photon's frequency also has a spread. Is this true?
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