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Thread: Is faster-than-light travel possible?

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    Quote Originally Posted by dgold44 View Post
    No, only a photon of (zero mass) can reach it
    "Zero mass" is a relative term? It is considered so in order to "fit" our mathematical calculations for now. Otherwise, there would be chaos LOL ... There seem to be no "absolutes." I think, we are still in diapers when it comes to physics, still, fascinating and the investigation and experimentation continues.

    What is the mass of a photon?

    This question falls into two parts:
    Does the photon have mass? After all, it has energy and energy is equivalent to mass.

    Photons are traditionally said to be massless. This is a figure of speech that physicists use to describe something about how a photon's particle-like properties are described by the language of special relativity.
    The logic can be constructed in many ways, and the following is one such. Take an isolated system (called a "particle") and accelerate it to some velocity v (a vector). Newton defined the "momentum" p of this particle (also a vector), such that p behaves in a simple way when the particle is accelerated, or when it's involved in a collision. For this simple behaviour to hold, it turns out that p must be proportional to v. The proportionality constant is called the particle's "mass" m, so that p = mv.
    In special relativity, it turns out that we are still able to define a particle's momentum p such that it behaves in well-defined ways that are an extension of the newtonian case. Although p and v still point in the same direction, it turns out that they are no longer proportional; the best we can do is relate them via the particle's "relativistic mass" mrel. Thus
    p = mrelv .When the particle is at rest, its relativistic mass has a minimum value called the "rest mass" mrest. The rest mass is always the same for the same type of particle. For example, all protons have identical rest masses, and so do all electrons, and so do all neutrons; these masses can be looked up in a table. As the particle is accelerated to ever higher speeds, its relativistic mass increases without limit.
    It also turns out that in special relativity, we are able to define the concept of "energy" E, such that E has simple and well-defined properties just like those it has in newtonian mechanics. When a particle has been accelerated so that it has some momentum p (the length of the vector p) and relativistic mass mrel, then its energy E turns out to be given by
    E = mrelc2 , and also E2 = p2c2 + m2restc4 . (1)There are two interesting cases of this last equation:
    1. If the particle is at rest, then p = 0, and E = mrestc2.
    2. If we set the rest mass equal to zero (regardless of whether or not that's a reasonable thing to do), then E = pc.
    In classical electromagnetic theory, light turns out to have energy E and momentum p, and these happen to be related by E = pc. Quantum mechanics introduces the idea that light can be viewed as a collection of "particles": photons. Even though these photons cannot be brought to rest, and so the idea of rest mass doesn't really apply to them, we can certainly bring these "particles" of light into the fold of equation (1) by just considering them to have no rest mass. That way, equation (1) gives the correct expression for light, E = pc, and no harm has been done. Equation (1) is now able to be applied to particles of matter and "particles" of light. It can now be used as a fully general equation, and that makes it very useful.
    Is there any experimental evidence that the photon has zero rest mass?

    Alternative theories of the photon include a term that behaves like a mass, and this gives rise to the very advanced idea of a "massive photon". If the rest mass of the photon were non-zero, the theory of quantum electrodynamics would be "in trouble" primarily through loss of gauge invariance, which would make it non-renormalisable; also, charge conservation would no longer be absolutely guaranteed, as it is if photons have zero rest mass. But regardless of what any theory might predict, it is still necessary to check this prediction by doing an experiment.
    It is almost certainly impossible to do any experiment that would establish the photon rest mass to be exactly zero. The best we can hope to do is place limits on it. A non-zero rest mass would introduce a small damping factor in the inverse square Coulomb law of electrostatic forces. That means the electrostatic force would be weaker over very large distances.
    Likewise, the behavior of static magnetic fields would be modified. An upper limit to the photon mass can be inferred through satellite measurements of planetary magnetic fields. The Charge Composition Explorer spacecraft was used to derive an upper limit of 6 × 10−16 eV with high certainty. This was slightly improved in 1998 by Roderic Lakes in a laboratory experiment that looked for anomalous forces on a Cavendish balance. The new limit is 7 × 10−17 eV. Studies of galactic magnetic fields suggest a much better limit of less than 3 × 10−27 eV, but there is some doubt about the validity of this method.

    If photons are massless, so are gluons and gravitons.


    http://math.ucr.edu/home/baez/physic...oton_mass.html

    Last edited by Padme; 05-27-2020 at 01:48 PM.

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    Quote Originally Posted by Peter1469 View Post
    Is faster-than-light travel possible?

    This is a cool article that says it is theoretically possible. You can read the article or watch / listen to the video.
    Only through worm holes and that could be impossible and the energy requirements world be a big star and it appears ..they are not stable and the radiation would kill you in seconds

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    Quote Originally Posted by dgold44 View Post
    Only through worm holes and that could be impossible and the energy requirements world be a big star and it appears ..they are not stable and the radiation would kill you in seconds
    How do you know that?
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    Quote Originally Posted by Peter1469 View Post
    How do you know that?
    I agree with the radiation part! A HUGE reason for not sending more humans requiring to get back to Earth after space exploration

    "Astronauts are exposed to ionizing radiation with effective doses in the range from 50 to 2,000 mSv. 1 mSv of ionizing radiation is equivalent to about three chest x-rays. So that's like if you were to have 150 to 6,000 chest x-rays.Oct 8, 2019"


    How much Space Radiation are Astronauts Exposed to?

    Beyond Low Earth Orbit, space radiation may place astronauts at significant risk for radiation sickness, and increased lifetime risk for cancer, central nervous system effects, and degenerative diseases. Research studies of exposure in various doses and strengths of radiation provide strong evidence that cancer and degenerative diseases are to be expected from exposures to galactic cosmic rays (GCR) or solar particle events (SPE).
    Milli-Sievert (mSv) is a form of measurement used for radiation. Astronauts are exposed to ionizing radiation with effective doses in the range from 50 to 2,000 mSv. 1 mSv of ionizing radiation is equivalent to about three chest x-rays. So that’s like if you were to have 150 to 6,000 chest x-rays.

    What Is Galactic Cosmic Radiation?

    Galactic Cosmic Radiation (GCR) is a dominant source of radiation that must be dealt with aboard current spacecraft and future space missions within our solar system. GCR comes from outside the solar system but primarily from within our Milky Way galaxy. GCR is composed of the nuclei of atoms that have had their surrounding electrons stripped away and are traveling at nearly the speed of light. Another way to think of GCR would be to imagine the nucleus of any element in the periodic table from hydrogen to uranium. Now imagine that same nucleus moving at an incredibly high speed. The high-speed nucleus you are imagining is GCR. These particles were probably accelerated within the last few million years by magnetic fields of supernova remnants.
    In summary, GCR are heavy, high-energy ions of elements that have had all their electrons stripped away as they journeyed through the galaxy at nearly the speed of light. They can cause atoms they pass through to ionize. They can pass practically unimpeded through a typical spacecraft or the skin of an astronaut.
    https://www.nasa.gov/analogs/nsrl/why-space-radiation-matters

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    I was referring to your claim that radiation in a worm hole would kill you fast.

    I know there are radiation issues in space. Shielding is the answer. To get enough shielding we need to build spaceships in orbit or in space.

    Quote Originally Posted by Padme View Post
    I agree with the radiation part! A HUGE reason for not sending more humans requiring to get back to Earth after space exploration

    "Astronauts are exposed to ionizing radiation with effective doses in the range from 50 to 2,000 mSv. 1 mSv of ionizing radiation is equivalent to about three chest x-rays. So that's like if you were to have 150 to 6,000 chest x-rays.Oct 8, 2019"


    How much Space Radiation are Astronauts Exposed to?

    Beyond Low Earth Orbit, space radiation may place astronauts at significant risk for radiation sickness, and increased lifetime risk for cancer, central nervous system effects, and degenerative diseases. Research studies of exposure in various doses and strengths of radiation provide strong evidence that cancer and degenerative diseases are to be expected from exposures to galactic cosmic rays (GCR) or solar particle events (SPE).
    Milli-Sievert (mSv) is a form of measurement used for radiation. Astronauts are exposed to ionizing radiation with effective doses in the range from 50 to 2,000 mSv. 1 mSv of ionizing radiation is equivalent to about three chest x-rays. So that’s like if you were to have 150 to 6,000 chest x-rays.

    What Is Galactic Cosmic Radiation?

    Galactic Cosmic Radiation (GCR) is a dominant source of radiation that must be dealt with aboard current spacecraft and future space missions within our solar system. GCR comes from outside the solar system but primarily from within our Milky Way galaxy. GCR is composed of the nuclei of atoms that have had their surrounding electrons stripped away and are traveling at nearly the speed of light. Another way to think of GCR would be to imagine the nucleus of any element in the periodic table from hydrogen to uranium. Now imagine that same nucleus moving at an incredibly high speed. The high-speed nucleus you are imagining is GCR. These particles were probably accelerated within the last few million years by magnetic fields of supernova remnants.
    In summary, GCR are heavy, high-energy ions of elements that have had all their electrons stripped away as they journeyed through the galaxy at nearly the speed of light. They can cause atoms they pass through to ionize. They can pass practically unimpeded through a typical spacecraft or the skin of an astronaut.
    https://www.nasa.gov/analogs/nsrl/why-space-radiation-matters
    ΜOΛΩΝ ΛΑΒΕ


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    Quote Originally Posted by Peter1469 View Post
    I was referring to your claim that radiation in a worm hole would kill you fast.
    I know there are radiation issues in space. Shielding is the answer. To get enough shielding we need to build spaceships in orbit or in space.

    Pete, I did not write the worm thingy! It was dgold44, I think is their TPF's identifier.

    Now, writing about your post: I think, there has to be a material able to shield the tremendous amount of galactic radiation. I also think, we have not found said material yet and that's why, so far, astronauts cannot stay, or are at extremely high risks to develop radiation disease when exposed to it. Also, why should we build spaceships in orbit or in space in order to get enough shielding?

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    Quote Originally Posted by Padme View Post
    Pete, I did not write the worm thingy! It was dgold44, I think is their TPF's identifier.

    Now, writing about your post: I think, there has to be a material able to shield the tremendous amount of galactic radiation. I also think, we have not found said material yet and that's why, so far, astronauts cannot stay, or are at extremely high risks to develop radiation disease when exposed to it. Also, why should we build spaceships in orbit or in space in order to get enough shielding?
    Because the weight of it would make it impractical to launch out of earth's gravity well with current rockets.
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    Quote Originally Posted by Peter1469 View Post
    Because the weight of it would make it impractical to launch out of earth's gravity well with current rockets.
    It makes sense... However, the Earth's gravitational field is kind of huge. In order to build a spaceship that did not have a significant weight, the building distance would be at least at moon distance if not farther and if at the moon, then it would be exposed to the moon's gravitational force... An advantage, but would the builders then be exposed to galactic radiation?

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    Quote Originally Posted by Peter1469 View Post
    How do you know that?
    That is what all the experts say. !!

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    If I talk about physics I am always repeating what I hear from Kaku or Tyson

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