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Posts posted by DanMP

  1. 14 minutes ago, Genady said:

    All these factors go under the "tired light" hypotheses

    Not all. An extra scattering and absorption due to higher interstellar gas density would decrease luminosity of the source in any scenario. How was this addressed? 

  2. On 8/14/2023 at 3:57 AM, Photon Guy said:

    people from a planet that has twice the earth's gravity would be able to perform tremendous feats of strength while on Earth

    Long time ago I was thinking about a method to subject athletes to higher gravity in order to increase their performance. I imagined special suits in which I would add half a kilogram (sand or something) each day until they double their weight. The extra weight must be evenly distributed and they should wear the suit all the time, so the idea is not very practical. Maybe a space station with artificial (centrifugal) gravity would be, one day, used to increase athletes performance by increasing gravity. 

  3. On 8/13/2023 at 8:30 PM, Genady said:

    This is already taken in account in the Friedmann equations.

    I didn't check but I agreed that Friedmann equations would account for increased redshift due to higher density back than. Still, there are other possible issues due to that higher density: more matter (mostly hydrogen) between stars/galaxies would absorb and/or scatter more light, decreasing the luminosity and making the source to appear farther ... It is very obvious, so I expect to be accounted for, but how?

    Another thing, nobody commented about the video I posted: the new estimation of the age of the universe and the possibility that part of the redshift may be from "tired light". I wonder if the late would also account for the increased expansion caused(?) by "dark energy". 

  4. 1 minute ago, Genady said:

    How you compare time then with time today?

    I knew that you would say that. We probably can't.

    So, the age of the universe was not "converted" to "today time" on Earth.


    Still, there may be an unaccounted "gravitational" redshift, because the "ancient" light originates from a denser region than we have now, here.

  5. 2 hours ago, exchemist said:

    One thing to bear in mind is that light only started travelling through dark space from the surface of last scattering, 380,000 years after the Big Bang, by which time a great deal of expansion had already occurred.

    Yes, good point. Still, the universe was much denser than today.

    1 hour ago, Genady said:

    This is the time of comoving reference frame.

    Comoving with what? Also, where, on Earth surface, between galaxies or on a neutron star "surface" 😀? Keep in mind that the Earth was not there in the beginning, nor any neutron star, nor the current intergalactic space, which is almost empty now. We shouldn't neglect gravitational time dilation, nor gravitational redshift. Probably they didn't, but I'm not sure. 

    1 hour ago, Genady said:

    Slower than what?

    Slower than our clocks, situated on Earth today.

  6. On 8/10/2023 at 11:13 AM, tmdarkmatter said:

    I came to this conclusion:

    "If asking questions reduces the reputation, then this is the wrong place to ask questions."

    "And if this is not a place to ask questions, then it is not a "scientific" forum at all."

    I understand what you mean (I am also "redshifted" 😛), but still, this forum is much better than physicsforums, where the moderators are very quick to close the topic, or restrict your right to write in it, when you insist asking uncomfortable questions. Just search/see my activity there. They are like a Physics Inquisition. This is not the case here.

    Regarding this thread, I believe that your misconception was to consider the balloon analogy with the Earth in the center ... Consider the Earth as another point on the surface of the inflating balloon and you will understand the responses you get.


    I also have some questions and observations regarding big bang theory:

    When they assessed the time from big bang, what reference frame they used? There is no absolute time.

    Just after big bang, the mass was confined in a small volume, yes? We know from GR that the clocks are slower when they are situated in/near a place with high density. Also light originating from such a place would be redshifted. Was this redshift considered (subtracted) when the speed of expansion was calculated? 

    Last but not least:



  7. On 7/11/2023 at 8:17 PM, joigus said:

    So you claim to understand what isolation in time and interacting time mean?

    Care to explain it to everybody else?

    You have to ask RossJ what exactly he meant.

    I think (but I'm not sure) that by isolation in time he meant that in the nucleus time may be dilated (gravitational time dilation). Such a thing may partially explain:

    On 7/6/2023 at 6:22 PM, RossJ said:

    the stability of a neutron and proton inside of the nucleus of an atom


    To be honest I don't agree with most of what he wrote, but I intended to be positive.

  8. On 7/6/2023 at 6:22 PM, RossJ said:

    the stability of these particles could be due to their isolation in time. This would mean that the strong nuclear force is so powerful that it is capable of isolating the effects of time. My only hypothetical pathway for this to occur would be that the tiny particles manage to pack themselves together so tightly that they create a singularity in space time.

    Interesting idea. I thought about something similar many times. Anyway, you may want to read about the Thorium Nuclear clock project.

  9. On 6/13/2023 at 7:00 AM, wei guo said:

    Today, the scientific community comprehensively accepts adding many extra unverifiable things into reality, e.g. extra mass: dark matter, extra energy: dark energy, extra position: superposition, extra dimensions, or even extra parallel reality. Considering reality is not understood completely, adding something into reality's unknown part is indeed a shortcut for explaining inherent measured discrepancy, but such behaviors are likely to distort the instinct of reality.

    In OP, wei guo wrote about many issues: dark matter, dark energy, "extra position", extra dimensions and "extra parallel reality".

    Most of you cherry picked the "extra position: superposition" error and ignored the issues of introducing: extra dimensions, parallel universes and dark energy. They are distorting the instinct of reality as Wei Guo said. Do we really have evidence for extra dimensions and/or parallel universes? Why such things are accepted in mainstream physics?

    About dark matter I disagree with Wei Guo, but for the rest I'm not. There are real issues.

    About "extra position: superposition" error, yes it was an error, but I guess that he/she was thinking about things like the explanation for interference of individual particles in the double-slit experiment, where we consider the particle taking more paths in the same time, as if the particle can be present in more than one position at a time. I don't agree with such explanations either  (I have another one, more intuitive).


    On 6/14/2023 at 1:02 PM, joigus said:


    So easily confused with extra position [?]= bilocation = "the supposed phenomenon of being in two places simultaneously"


  10. 18 hours ago, swansont said:

    OK, how do they know, and have had time to send more probes? Why are they showing up at basically the same time?

    Well, I'm not really interested in this alien theme/subject and it seems that neither are you, because if you were, you would know about ancient aliens/astronauts theory, also that an alien civilization may be much older/advanced than ours, that a probe may stay hidden long long time, and so on.

    I wrote about this subject mostly because I hoped that someone interested in it, and talented, would be inspired by my ideas and write nice SF novels or movie scenarios.

    I don't know about you, but I decided to let others take over, if they want/need to. For me it's enough.

  11. 1 hour ago, swansont said:

    How would we know, before the first probe sends us the data?

    No, I meant around us ... Another reason to have more alien probes, with different agendas, here.

  12. 18 hours ago, swansont said:

    At 100 LY, a probe moving at 0.1c (i.e. incredibly fast) will take 1000 years to arrive, and need an additional 100 years for the data to get to us.

    0.1c with the technology that we can have or imagine today ... Even so, I wrote "under 100 light years", not 100 or over. If the distance is around 20 LY we can get info from the probe in 2-3 centuries. I also wrote about other ways to get new info + other reasons to send new probes.

    And there may be more than one civilization around ...

  13. On 5/30/2023 at 6:49 PM, swansont said:

    Solar system exploration isn’t the same thing, though. You can investigate new things without much overlap. But if one probe is sent to a distant world to see if there is life there, what benefit is there sending a second one, years later, but before any data is collected?

    Well, if the target is not very far (under 100 light years), new data may be collected in few decades/centuries, both by the first probe and/or by new/enhanced telescopes, or new data may arise due to the developments in the targeted planet (first EM emissions and/or other activities, like atomic explosions, artificial satellites, etc.).

    Other reasons to send new probes may be: 

    • the technology needed becomes less expensive 
    • the new senders are not happy with the others agenda
    • the enhanced technologies offer new, much better, approaches/possibilities (see here how I would do it)



    On 5/18/2023 at 5:45 PM, Moontanman said:

    The next question of course is how could we find or detect such alien technology in our solar system.

    If they are Bracewell probes, we shouldn't care. Just wait for them to contact us, when they consider appropriate.

    If they are, instead, alien probes sent to spy us prior to a future invasion, we need to properly investigate all the sightings and also to prepare a defense, although our nuclear arsenals may deter such plans, because on arrival they may find here a destroyed, uninhabitable planet ...

  14. 19 hours ago, swansont said:

    It seems likely that deep space probes would be a collaborative effort, like the ISS, in order to defray costs

    Maybe, but not necessarily. The Americans, Russians and Chinese are not getting along very well and have different space programs/projects ...  And we are talking about centuries from now ... and maybe more civilizations ... So one planet may have dozens/hundreds different visiting probes.


    19 hours ago, swansont said:

    They would not be Bracewell probes; the OP went out of their way to specify one particular type of probe. These would have to be some other sort of probe.

    A Bracewell probe may delay the contact "until we achieve a certain level" (my option 1) or just be "afraid" of us (my option 2) and abort it.

    If option 3 is the one, then the probe is not a Bracewell probe, yes, but we shouldn't ignore that possibility.

  15. 20 hours ago, HawkII said:

    we can also use Nukes to cool Earth down

    We can use nukes + railguns:

    There may be another way to "save"/cool the Earth: large sheets of reflective materials on orbit around the Earth, both for shading & cooling the hot regions (including storm cells) and for heating the cold regions (by reflecting sun light). Besides tempering the climate, electric energy can be saved (less power used for cooling/heating) and produced (solar panels on Earth using the reflected - and focused - light from orbit). No fusion reactors needed ... Just railguns and/or nukes to launch the materials on orbit and astronauts/robots to deploy the sheets. Not easy but doable.

  16. On 5/22/2023 at 6:09 PM, DanMP said:

    3. caused by aliens, but not as part of some official mission. If an alien civilization has achieved (although it's very improbable!) the technology for fast and not very expensive space travel, fast enough to make a trip to another planet and back in days/weeks, or the technology to jump back/forward in time or to jump to parallel universes and back (I personally don't buy/believe such things), it would be possible for private alien citizens to briefly visit us, just for fun. Official missions won't be so sloppy ... The officials would rather chase away those intruders.

    I realized that "caused by aliens, but not as part of some official mission" + "The officials would rather chase away those intruders" is also true, and more probable, with long/normal travelling times. The probes, equipped with AI, may be sent by many different organizations/nations in many "waves"/years, with quite different technologies and agendas, resulting in apparently chaotic behavior of "the aliens".

    We, from Earth, will probably send, in the next 100-200 years, dozens or even hundreds of such probes to the nearest interesting solar systems, and we already have many different nations and organizations involved in space exploration ...


    And, if there are such alien probes here, they may be reluctant to contact us because:

    1. they don't want to interfere in our development, until we achieve a certain level or
    2. they are afraid that we may attack their home planet if we learn about it/them or
    3. they don't want us to be prepared when their invading fleet would arrive ...
  17. On 5/18/2023 at 5:45 PM, Moontanman said:

    "if" the UAP/UFO phenomena turns out to be not of this earth I think the idea of a Bracewell Probe might be a viable explanation of not only where these objects originate but the concept might even explain some of their behaviors. 

    No, I don't think that an alien civilization capable to reach our planet would be incapable to make contact with us. Not willing maybe, yet.

    So, the UAP/UFO phenomena are:

    1. natural phenomena, not fully/satisfactorily explained
    2. caused by humans on purpose (practical joke, illusionism, etc.) or by accident (secret technology)
    3. caused by aliens, but not as part of some official mission. If an alien civilization has achieved (although it's very improbable!) the technology for fast and not very expensive space travel, fast enough to make a trip to another planet and back in days/weeks, or the technology to jump back/forward in time or to jump to parallel universes and back (I personally don't buy/believe such things), it would be possible for private alien citizens to briefly visit us, just for fun. Official missions won't be so sloppy ... The officials would rather chase away those intruders.
  18. On 4/8/2023 at 6:01 PM, Moontanman said:

    Now I see one of my most respected scientific sources seemingly asserting that all I've been taught was solid as a rock is in fact on shaky ground at best, Sabine Hossenfelder has blown my mind by suggesting all I know might not be as solid as I was led to believe. Is anyone willing to watch this video and assure me that Sabine has slipped a cog so I can let go of the nearest pine tree and return to the idea of solid ground being solid ground? 

    Yes Sabine kind of slipped a cog. I watched her video (I am subscribed) and I see that she became more interested in gaining views than in being logical. With that title, and the ambiguity, she definitely gained a lot of views ...

    What she missed?

    1. She based her arguments on a theory (GR) she considered (in the end of the video) in order to be replaced with a new one, quantum gravity, making her arguments more or less irrelevant.

    2. She missed the fact that the speed of interaction is also c, so if you move faster than c, you would normally brake apart.

  19. 13 hours ago, Alex_Krycek said:

    As established I have a different outlook - I think the odds of visitation by an intelligent extraterrestrial species are incredibly high given the number of habitable planets and the age of our universe.  I don't see alien visitations as abnormal - it was always only a matter of time.

    8 hours ago, Alex_Krycek said:

    We’re estimating the probability that an intelligent life form in the universe has:

    1. achieved interspecies sustainability (i.e. they’ve moved past, or never encountered, the challenge of blowing themselves up
    2. exists at the same time as humanity
    3. has solved the distance problem by harnessing a physical principle that human beings have yet to actualize.  Using this physical principle and the technology built upon it, they are able to traverse the galaxy efficiently.  By efficiently, I mean physical distance is basically irrelevant to them.  They have understood how to manipulate spacetime in such a way as  to go where they want, when they please.
    8 hours ago, Alex_Krycek said:

    The SETI Institute estimates that there are 300,000,000 habitable planets in the Milky Way.  Of these, if we assume that .000001% of these planets has produced the species fulfilling the conditions above, there would be 3 species within the Milky way that are capable of visiting Earth.

    If we move beyond the Milky Way, the odds are even more favorable. Mario Livio, an astrophysicist at the Space Telescope Science Institute estimates there could be between 100 billion and 200 billion galaxies in the universe.  Let’s assume 100 billion galaxies. 100 billion galaxies multiplied by 300 million habitable planets in each galaxy is 3e19.  With a .000001% chance of meeting the 3 conditions stated above (remember this species has solved the distance problem), there would be thousands of species capable of reaching Earth.  With 3,000,000,000,000,000,000 (3e19) planets capable of supporting life in the Universe, it's highly possible at least 1 of those has met the three conditions stated above, if not more.

    Ok, even if they "solved the distance problem by harnessing a physical principle that human beings have yet to actualize" (which is highly improbable), there are plenty of planets to visit, so the probability to be here, now, should be much lower than you think.

    Another problem: if somehow aliens arrived here, what are they doing? Would you do such an effort just to play hide and seek?

    Apart from UFO being misinterpreted natural phenomenons, there may be also other explanations, like secret military research/experiments, including genetic (see the creature in Brazil; it reminds me of Jurassic park).

  20. 21 hours ago, swansont said:
    On 2/19/2023 at 5:37 AM, Moontanman said:

    BTW, I've seen Venus dance around the sky in an early morning temperature inversion, it was an astounding sight. But I was expecting Venus in that area of the sky and i was familiar with the local tendency for temperature inversions so I knew what it was immediately.

    Since not everyone is familiar with that, they might arrive at a different explanation.

    Same with Iridescent Pileus Clouds.

  21. On 1/13/2023 at 11:19 PM, Ghideon said:

    Question @DanMP ...

    As for any anomaly/discrepancy, you must find and eliminate all the (possible) errors and/or redo the experiment, until you are sure that the "anomaly/discrepancy" is real.

    As I wrote before, the test can be done first/also with a clock orbiting the Moon. Even from the Earth we may pre-test it, measuring spectral lines shift, but only if it's done with high accuracy.

    I have also different kind of tests, easier to perform. About them I want to write first im my dedicated thread, but not very soon, because I am busy.

  22. 10 hours ago, Markus Hanke said:

    Calculating the total time dilation when there is a combination of differences in gravitational potential, as well as relative motion, is a standard exercise that’s done in most undergrad courses on GR. It’s not that hard so long as you can use the Schwarzschild metric, which is highly symmetric. Usually it’s done in the context of GPS satellites, because ...

    It may be highly symmetric for our GPS satellites, because they are in the same gravity well as the clock on the Earth's surface. I'm not sure that it would be the same and easy in my Moon-Earth scenario.


    10 hours ago, Markus Hanke said:

    We have had a large number of crafts of different kinds both on the surface of the moon, and in orbit around it. We have also bounced lasers and radar signals off the moon’s surface. All of these things explicitly take into account time dilation - it affects orbital mechanics, it affects light travel times, and it affects frequency shifts. No discrepancies with expected physics have ever been observed in that regard.

    You are sure? Frequency shifts discrepancies due to Moons orbital velocity (relativistic Doppler effect) would be small. Detectable, yes (see Very-long-baseline interferometry), but did anyone bother to actually do it, I mean to search for discrepancies? I'm asking that because discrepancies/anomalies were found when they had 2 different ways of determining the velocity. Watch from 2:40

    I'm not sure that this is the case, but when you make corrections in order to compensate for the relativistic effects (both in frequency shift and in time dilation) of the Earth movement through galaxy (they calculated the galaxy movement/speed), when in reality it should't be any kinematic effect due to gravity well movement, you may get such anomalies/discrepancies ...


    10 hours ago, Markus Hanke said:

    But it won’t ever be abandoned - that’s never going to happen, because it has already proven far too accurate and useful.

    I wrote:

    On 1/12/2023 at 5:31 PM, DanMP said:

    GR would have to be adjusted or abandoned

    The first option was adjusted.


    10 hours ago, Markus Hanke said:

    there is nothing whatsoever to suggest that anything out of the ordinary will happen if we perform that experiment of yours

    Nothing whatsoever? A theory (my theory) published in Speculations is not nothing whatsoever. Not accepted here, yes, but not nothing whatsoever.


    10 hours ago, Markus Hanke said:

    Like I said, if you want to test time dilation on the moon’s surface with respect to an Earth observer, then bounce a laser or a radar echo off it, and compare propagation times and frequency shifts to what our models say they should be. It’s a much easier test that addresses the same issue of time dilation, and it’s been done many times since 1946 - Earth-Moon-Earth communications is in fact an entire sub-discipline of aeronautical engineering.

    I searched the site you offered and found no reference to relativistic Doppler effects. Search for "shift" and see what you get. It is doable, yes, with Very-long-baseline interferometry, but it was really done?


    10 hours ago, Markus Hanke said:

    That’s true. But it’s also dangerous to become obsessed with a single tree, and forgetting the rest of the forest - which is what you seem to be doing here.

    The keyword is here. Here I'm not allowed to speak freely, but, when I'll have the time, I will continue the discussion with you in the proper place (the Speculations sub-forum, in my old topic). The irony is that you (all) are in fact "forgetting the rest of the forest": the dark matter.


    10 hours ago, Markus Hanke said:
    On 1/12/2023 at 5:31 PM, DanMP said:

    Loads of money? Tiny, compared to LHC, JWST, or gravitational-wave detectors.

    It’s not the total amount that’s the problem, but the cost/benefit ratio.

    You don't really know the benefits, just the cost, which is quite low with so many missions to the Moon. The cost of not doing it may be higher, because we are investing a lot in possibly wrong directions.

  23. 8 hours ago, Markus Hanke said:

    I’m still not sure what you are actually suggesting. Do you mean you want to have two clocks, one stationary on the moon and one stationary on the Earth, and then compare them?

    Yes, two clocks, one stationary on the Moon and one stationary on the Earth. How many times I need to repeat this? 😄


    8 hours ago, Markus Hanke said:

    If so, then yes, you’d get a gravitational and a kinematic component to the total time dilation - though the kinematic contribution will be very small.

    Did you make (or read) proper GR calculations, or you are just guessing?

    What reference frame was used and why?


    8 hours ago, Markus Hanke said:

    Why would you expect things to be any different on the moon, as opposed to a satellite? It’s not like either gravity or motion function any differently there than they do here.

    With one clock on the Moon surface and the other on a Moon artificial satellite, yes, things would be exactly as expected. No reason to be different.

    The test with one clock on the Moon surface and the other on the Earth surface was never done, nor any similar, so you don't really know the outcome. It is a dangerous thing, both in physics and in life, to be sure that you know something, when in fact you never really checked it.


    8 hours ago, Markus Hanke said:

    If there was some physical difference between gravity on Earth and elsewhere in the solar system, then we’d have already noticed this in other ways.

    Gravity is not different, that's not the issue, we simply have not enough/accurate information about "kinematic time dilation" caused by the movement of a planet/star/moon. If you do have such information, please share it here.


    8 hours ago, Markus Hanke said:

    There’s nothing wrong in principle with performing such an experiment, but I don’t think anyone will throw loads of money at this, since we have no reason whatsoever to expect that anything special would happen.

    Loads of money? Tiny, compared to LHC, JWST, or gravitational-wave detectors.

    So you don't expect that anything special would happen. I hope you are aware that a theory must pass any kind of test related to it. This kind of test (able to check with accuracy the "kinematic time dilation" caused by the movement of a planet/star/moon in relation with another planet/star/moon) is highly related to GR and never performed. If the test is not passed, GR would have to be adjusted or abandoned. You are denying that?

  24. 3 minutes ago, zapatos said:

    But an artificial satellite DOES have mass. So again, why choose the moon over the satellite?

    By massive object I mean a star, a planet or a moon.

    The reason: because it was not done and it may be interesting.


    1 hour ago, swansont said:

    Yes, it’s just a different scenario, but ...


    Ok, I get it, you don't find it interesting enough. No problem.

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