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Posts posted by NowThatWeKnow

  1. So one rock that was in space for 16 million years is a deal breaker for you? ...

    It could be 100 years or millions of years. Space is a harsh and life surviving would surprise me. It seems some share your view so you are not alone but I am a little more pessimistic. I am not sure why life would be in the center of a rock anyway. I would like to see NASA prepare a big rock with life in it and see what's left after reentry. They could put in a low Earth orbit so it could endure space for awhile and controlled retro rockets could bring it home in a safe location. A positive test would make many open their eyes.

  2. Thanks moth, That's the kind of equation I can work with.l I did find

    "an accelerating dragster or space shuttle. Spinning objects such as merry-go-rounds and ferris wheels are subjected to gravitational time dilation as an effect of their angular spin."


    I feel much better about gravitational time dilation. My last question is how much will each additional artificial G force on earth (if location matters) slow a clock?

  3. Did we read the same link? It's very likely to happen, rocks stay cold inside through the entire ordeal both being launched and reentry, and being inside a rock protects the bacteria or spore or maybe even tardigrades. Most of the objections to life trveling from the Earth to say Mars or vice versa was due to UV radiation but inside a rock UV is no problem.


    Quotes from the article:

    "remained cool enough during its violent ejection from the red planet and its fiery trip through our atmosphere 16 million years later to sustain life â€" were there any aboard."


    "Now we know that species from three very different organism groups â€" bacteria, lichens and invertebrate animals â€" are able to survive at least short periods under space vacuum and also under some restricted conditions of solar radiation," said K. Ingemar Jonsson


    "Equally important, the creature needs a hospitable environment upon arrival."


    A few thought are:

    This space rock would endure temperatures from hotter then boiling water to very very cold. I do not see how life could remain frozen and dormant or unfrozen and dormant under those conditions. If it wasn't dormant it would have to eat, reproduce, get old and die. 16 million years is a long time.


    Second and third paragraphs are not convincing me that it is likely either.


    Interesting, possible but I am far from convinced that it is likely.

  4. When people talk about 0G they do not mean there is no gravity (well they might but they're wrong), they mean they are in freefall, normally with what they're in as well.. It is true that gravity is lower, which is what your quote says, but there is still gravity from the earth.


    So a satellite has a balance of centrifugal force and centripetal force and is actually in a free fall. (1) Does true 0G exist anywhere in the universe (between galaxies)? So if our solar system was located closer to the black hole in the center of the Milky Way the clocks would be slower but our gravity would feel the same. (2) Artificial gravity from spinning would slow a clock, right?

  5. To me that seems a big jump. Life in the Solar system other than on Earth may "suggest" that there could be life outside the Solar system, but I would not say that by itself it is evidence.


    If it happened twice in our solar system with out Panspermiam, it would have happened under two very different and possibly extreme conditions. That tells me it could easily happen often if the conditions were even close to right. The current #'s used in the Drake equation suggest there are at least 1,200,000,000 solar systems in the Milky Way alone with potential for life.


    I posted my second post in this thread without reading the material first. It will not let me edit it for some reason. Will I ever learn. :)

  6. ...

    Try putting this in the google window and press return

    sqrt( 1 - 2G*mass of earth/(radius of earth*c^2))


    ugh! it says our earth clocks are slower by a factor of


    only slightly slower and probably too small for the precision of the calculators. ugh bah and fiddlesticks (Phi objects to profanity).


    I will try just the important number


    G*mass of earth/(radius of earth*c^2)


    Google says

    (G * mass of Earth) / (radius of Earth * (c^2)) = 6.95453588 × 10^-10


    In other words the redshift is approximately 0.7 parts per billion.


    Our earth clocks are slower by about 0.7 parts per billion.


    But Martin, Is the 0-G from being in orbit even being considered? Or does it need to be considered? It doesn't look like 0-G is being considered when calculating time delays for the GPS system.


    "Further, the satellites are in orbits high above the Earth, where the curvature of spacetime due to the Earth's mass is less than it is at the Earth's surface. A prediction of General Relativity is that clocks closer to a massive object will seem to tick more slowly than those located further away (see the Black Holes lecture). As such, when viewed from the surface of the Earth, the clocks on the satellites appear to be ticking faster than identical clocks on the ground. A calculation using General Relativity predicts that the clocks in each GPS satellite should get ahead of ground-based clocks by 45 microseconds per day."


    I would have thought that the 0-G from being in orbit would be more significant then a floor and ceiling type calculation. I am a little confused now. :confused:

  7. From my understanding, it seems that stopping time would be like reaching light speed with matter (like .75c + .75c = .96c). Relative to Earth clocks we can almost stop time as we increase relativistic speeds close to C. We can also almost stop time relative to Earth if we could put a clock on a black hole. So I think that a black hole traveling at relativistic speed would just have a very very slow clock.


    Is this in the ball park?


    I have been looking for a gravity time calculator but so far have not found exactly what I want. The "space math" site has everything but what I want. I would like to compare earth clocks to different g forces. Would Gravitational potential vs G-force complicate things?

  8. One of your problems with visualization, IMO, is that propellers only move at a small fraction of the speed of light, making dilation effects pretty negligible. Other forces (cohesion?) overwhelm this effect.


    I believe this is a large rocket powered propeller in space with tips reaching

    .99+C to study time dilation.

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    it seems like the propeller blades would bend back like boomerangs as the tips slower time passage would begin to affect how much distance they could cover without exceeding lightspeed.


    Maybe rather then bending the propeller, the energy needed to increase speed would stop the acceleration of the propeller. Like not having infinite energy for matter to reach the speed of light.

  9. ...With material being shared between the planets due to impacts it is possible that life in the solar system has a common origin...

    Are you suggesting that life may have been transported to another planet or moon from impacts? I can not see any life surviving the impact or trip. As far as material, the planets and moons share common materials from when it was formed. It also seems other solar systems would likely share common elements. I think that finding life elsewhere in the solar system would tell us it is common in the universe.

  10. ...in the Ehrenfest setup the people on the platform see the train cars as contracted, and the people on the train see the platform as being contracted. it just seems natural to think of this as an arc in the time direction with the endpoints of the arc getting closer as the radius of the arc decreases(velocity increases)...


    But inside their own frame everything looks normal. I think we would have to look at the propeller as a variable frame when spinning (I don't think Martin likes "variable frame" :embarass: ). From outside the propeller frame(s) it may appear to be warped but all it is doing is aging very slowly. I am trying to apply what I learned recently but still make mistakes often. Anyone want to straighten me/us out? :P

  11. ...is it just unconventional to think of this length contraction as the train cars being bent in time or is there a contradiction somehow?

    Contraction is only seen by an observer outside the inertial frame. I guess you would have to consider time dilation from speed and gravity. So how slow can time go?

  12. what is the difference between observable and visible(in astronomy or in physics)


    my native language is not english..that's why, I don't get it


    Visible is what you can see with you eyes.


    Observable (physics) (as defined by Bookshelf)

    A physical property, such as weight or temperature, that can be observed or measured directly, as distinguished from a quantity, such as work or entropy, that must be derived from observed quantities.


    Edit - You can observe the automobile with your eyes or your hands but it is visible only with your eyes.

  13. Does the after image of an object linger after it has been accelerated past the event horizon? If yes, then can u please explain. Does time bend? Does Newton's laws affect any thing and how does the black hole enventually explode. Then where does the matter that has been sucked in go?:confused:


    Wikipedia has a detailed explanation of what happens when you fall into a black hole.


    Have we observed a black hole explode? We do observe plasma jets coming out of them.

  14. Earth logic is quite consistent with the relativistic velocity addition rules.


    [math]v = \frac {v_1+v_2}{1+v_1v_2/c^2}[/math]


    You make a good point. If Earth logic was on a scale that we could observe it, we would be much better prepared to understand relativistic velocity.

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    I'm not sure if this will help you, NowThatWeKnow, but it helped me. A short flash tutorial:




    I have seen similar demonstrations but the power point presentation let me go at my own speed for better understanding. Thank you. I like your signature line and it is so true. Since you are an expert now could you confirm all four examples below are correct?


    The twin paradox revisited (Dick and Jane)


    1. Dick takes a space trip at relativistic speeds and when he comes back to Earth he is younger the Jane.


    2. Jane doesn't want to be old so she takes a similar space trip and comes back the same age as Dick.


    3. Jane wants to be younger then Dick so she starts off an a space trip. Some time later Dick decides he doesn't want to be older so rather then wait for Jane to turn around and come back, he jumps in his space ship and goes to her. They are the same age?


    4. They both want to be younger and take off an similar space trips but in the opposite direction. When they get back they will be the same age even though they were in different inertial frames the entire trip. Is that right? The separation and closure during the trip was equal.


    My head hurts now. :P

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    Yes indeed. Relativity (and quantum mechanics) are not logical by the standard of everyday experience. That's one of the hurdles to understanding it. It's not intuitive when you start learning about it, and it can be a long row to hoe before any of it even starts to become intuitive.


    Physics is also not just math or accounting. In accounting you have rules, but you can make up new ones. In physics, we are bound by how nature behaves, and have to deduce the rules empirically.

    Working and understanding the math (concepts) is hard enough but having the logic and aptitude to come up with the math and concepts is amazing.

  15. that sounds hopeful, and as if the best thing for me is not to say anything and let this natural process continue of fitting pieces and getting used to.

    Sometimes it's better not to interrupt because yet another explanation at the wrong time can throw one off track...


    So there is kind of a division of jurisdiction: For the universe's changing largescale distances you use Ned Wright's calculator (google "wright calculator") and watch Wright's balloon (google "wright balloon model") ....


    I have the feeling that you already got over any problems with this, but since you pointed out the apparent disagreement of the SR and cosmo calculators I thought I'd say something.



    Your post are always welcome and helpful but when good information is flowing you can recharge your batteries for when it is needed.


    You pointed me to the Wright calculator and I am very comfortable with it. The #'s it gives are very believable. I am not in disagreement with any of the calculators but Earth logic has to be ignored when you use some of them. An accountant saying .75 + .75 = .96 could end up in jail.


    SR and time dilation are still awkward at times as you can tell from my post. I feel better about it every day and with an effort on my part and a little help from you guys I will get there. My goal is to answer more questions then I ask.

  16. ...If I see an object going at at 0.75c to my right, and at 0.75c going to my left, they are separating at 1.5c. To each other, though, they are separating at 0.96c, and none of our clocks are running at the same rate.


    This is definitely not an easy topic to grasp.


    The two calculators from you and one from Martin will let me come up with paradoxical #'s that I will just have to accept. I am glad you said it is not easy to grasp. However, the pieces of the puzzle are slowly coming together. Thanks

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    BTW, in case it's not clear, I'm basically a layman, too, so don't take anything I say as authoritative...


    What is clear is that you are a lot closer to working in a rubber room with raw meat for lunch then I am. :D Thanks




    Didn't mean to hijack your thread but it is all about light speed. :)

  17. i don't think its currently possible. photons have no mass that's why they can reach such immense speeds. however matter has mass which i think rules out the possibility.


    Yes, in my first post in this thread I ended with "Do not confuse a proton with photon." I should have said: A photon (light) has no mass and a proton has mass and can not reach light speed.

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    No. From the perspective of both ships, there would be a large velocity between them. From the perspective of Earth, the velocity difference between the two ships would be small.

    Could we say the Earth and Joe in the scout ship would have a similar view of the three objects (total separation <C)? But from the center mother ship there would be an illusion of a seperation speed between Joe and Earth >C?



    Yes, you would get to your destination sooner. You just wouldn't get any closer to C. The speed of light is always always always the same in all directions, no matter what reference frame you are in. You can never say "I'm moving almost as fast as that light beam," because from your perspective, the beam is still moving away from you at C. Only otherobjects can appear to be moving at some fraction of C. And from the perspective of that other object, you are moving at some fraction of C.


    I understand part of what you are saying but lets say we send two ships to our neighbor star 4 light years away. Ship one accelerates to .99c and then lets inertia maintain its speed (we only allow power to maintain .99c if gravity or space dust slows it down).


    Ship two leaves at the same time but maintains full power for the entire trip. However, it never exceeds light speed.


    Approximately how much time do both trips take as observed from each frame?


    If there is a link that describes this concept for the layman, I would be happy with that.


    No one answered my question: Would one of you physics experts please tell me this is not easy to grasp so I do not feel stupid?

    Maybe I don't want you to, depending on the answer. :D


    I do thank you and everyone else that helps the layman in this forum.

  18. I'm assuming that the 500 seconds you stated above is an approximation to the actual travel time...


    Space can be curved by gravity. the presence of time dilation does not gaurentee spatial curvature.


    Yes, the 500 seconds was an approximation and just a # to work from. The impact of gravity on light speed observed from different frames was important.


    I still have a little trouble accepting gravity bending a metric without an ether but time will tell the real story.


    Thanks for your reply.

  19. Well, that depends on how you define "complicated"


    ...The nonlinearity of velocity addition is much reduced at low speeds, so at speeds we're used to experiencing we don't notice it...


    The equations are at



    and there are calculators, too. The case that applies most directly is the third box, with the rocket sending out a projectile


    I can relate to those equations but the calculator is nice. So this applies to two cars on I-40 also? Can you imagine how much time Isaac Newton wasted doing math long hand? Thanks for the link.


    This thread tells me that what appears to be a separation speed > C (between Earth and Joe) as observed by the mother ship is really an illusion. That makes me wonder about the apparent separation speed of distant galaxies and "The Universe" program scientist saying "the only thing faster then light is the expansion of space".


    Would one of you physics experts please tell me this is not easy to grasp so I do not feel stupid.

  20. Even though, from either ship, they would be separating at 0.99C, from Earth the separation speed of the farther ship would still be less than C, and two ships would have a separation speed of less than 0.01C. The mothership would still be at 0.99c, and the secondary ship would be 0.9999C (or something). This is possible because the relative velocities of objects is dependent on the reference frame from which they are observed.


    From a reference point on the mother ship, the secondary ship would get to their destination well ahead of them. The mother ship would arrive on time by their own schedule as calculated on Earth. Maybe not a fair comparison but we can sit here on earth and watch the distance between two distant galaxies increase faster then the speed of light. Are you saying because of time dilation the mother ship would arrive at the destination VERY shortly after the secondary ship (from the perspective of space man Joe in the secondary ship)?


    ...you can keep accelerating indefinitely at the same rate, and you never get any closer to C...


    Are you saying you would not get to your destination any sooner?

    If so, it would be wise to conserve power and shut down the engines and let inertia do it's thing.

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