Space travel

Discussion in 'Science' started by Nonnie, May 2, 2018.

  1. AARguy

    AARguy Well-Known Member

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    I am reminded of my days working at NASA-Houston. There was a sign over the employee entrance that rread:
    "The meek shall inherit the earth"... the rest of us... ARE GOING TO THE STARS!
     
  2. Kode

    Kode Well-Known Member

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    Surely you know that as you travel faster and faster eventually approaching the speed of light, time slows down so that at 99% of the speed of light a year on earth would seem to be a little less than a month to someone traveling at that speed, and at 99.9% of the speed of light a year would seem to be a week. And at 99.99999% of the speed of light 6 years would seem like a week. https://www.dummies.com/article/aca...-time-to-a-standstill-with-relativity-193289/

    TIME DILATION CALCULATOR

    So theoretically if we had a “starship” that could travel close to the speed of light, we could travel fast enough in a round-trip from earth and back to earth to arrive at our destination 100 years in the future and it might seem like 2 weeks had passed. But we have no knowledge at this time of how to get back to today.
     
  3. WillReadmore

    WillReadmore Well-Known Member

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    It is true that if we could travel at relativistic speed (significant percent of light speed) the time experienced on earth would not be the same as that experienced by those on the trip.

    But, those on the trip would still have to travel to their destination and back at the trip distance divided by their travel speed. That is, if you could travel at light speed, it would take 4 years to get to our nearest planet that is outside our solar system, because it is 4 light years distant. If you can travel at 1/10th light speed (faster than the fastest spacecraft we have today) it would take the astronauts 40 years to get there, then 40 years to come back. The astronauts wouldn't live that long, so such a trip would need to be robotic.

    When the spaceship returns, those left on earth would not have seen the same amount of time having passed. But, imho, the real issue is how long the trip would take for the trip. That is what would determine factors like amount of fuel, energy for control of the ship, etc. - all of which would need to be accelerated to relativistic speed, then stopped to turn around and accelerate back toward Earth.

    There are new methods of propulsion being considered for space travel, but I know of NO idea that would make a trip to the closest habitable planet outside the solar system a remote possibility for humans.
     
  4. Kode

    Kode Well-Known Member

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    Yes, but that 4 years is time as it is perceived and measured by observers on earth. WE say it took 4 years for the light to get to us. But for someone traveling at relativistic speeds it would be much less. If you were traveling at 99.99999783% of the speed of light, that 4 years would be one month to you.

    True.

    But progress is being made. We know that physics says if a particle or any object loses mass entirely, upon reaching zero mass the particle or object would instantly accelerate to the speed of light. And studies are being done on the nature of mass and gravity with attention to quarks and string theory. If a means of eliminating the mass of a “tic-tac” vehicle can be found, we may have a way to achieve light speed.
     
  5. WillReadmore

    WillReadmore Well-Known Member

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    No, this is not true. The trip length is 4 light years. That is how far the planet is. That does not change, no matter how fast you go. For example, the very measurement of that distance is based on how fast light travels. If you travel slower than light, the target will take longer to reach.

    Creating a spaceship out of particles that have no mass is not an idea contemplated by physics, including theoretical physics.
     
  6. Kode

    Kode Well-Known Member

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    You know what? I’m sorry but you’re wrong. Science has been saying for the 60 years I’ve been following it that if an observer on earth watched a person in a space ship traveling at nearly the speed of light, the traveler would seem to be living in slow motion and when he returned to earth he would find that his family and friends had either all grown ole or died, and the year was way beyond what his watch says.

    It has been illustrated by proposing a timer made of two opposing mirrors, facing each other, onboard the spaceship, with a beam of light bouncing between the two mirrors arranged perpendicular to the direction of travel. It was said that the light beam would travel between the mirrors at a speed that looked normal to the traveler, but to observers on earth it would seem to move very, very slowly. Why? Because the light beam would actually be traveling in a zig-zag path as the ship advanced, so it would have much farther to travel to get to the other mirror.

    Are you at all familiar with this? Here; no need to believe me…..

    https://en.wikipedia.org/wiki/Time_dilation

    https://www.technologyreview.com/20...-affect-aging-during-high-speed-space-travel/
     
  7. Kode

    Kode Well-Known Member

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    How about finding a way to eliminate mass at will? Maybe. Studies are being done on the graviton. It is thought that by understanding the graviton, it may be possible to eliminate gravity at will from a place, thing, or area. Then an object could be floated in the air or rise without gravitational effect. And they’re thinking this may open the way to discovery a means of altering or eliminating mass.

    Have you been keeping up on the reports that have now been made on UFOs by top Air Force officials, police, scientists, etc.? Have you seen the “tic-tac” UFO and how it instantly accelerates and turns sharply at very high speed?
     
  8. politicalcenter

    politicalcenter Well-Known Member

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    If we could use gravity to warp space and therefore decrease the distance between two points substantialy, we could travel in real time. But a lot of questions here.
     
    Last edited: Mar 4, 2023
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  9. WillReadmore

    WillReadmore Well-Known Member

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    Yes, when the spaceship returns, people on Earth will have experienced more time.

    For the person in the spaceship, it is still a requirement that they travel the 4 light years of distance at the speed of their spaceship.

    We see this with the ISS, where astronauts have stayed for considerable time where time dealation effects are at play because of speed and the difference in gravity.

    When astronauts return, they are younger than their Earth bound twin would be.

    But, that doesn't mean the travel speed to the 4 light years distant planet was changed - it just means that time passed at a different rate compare to how it passed on Earth.
     
  10. Kode

    Kode Well-Known Member

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    Ah! I see.

    I didn’t say the actual time for traveling changed. I said the passage of time seemed to be far, far less for the traveler and that s/he aged less quickly consistent with how much time SEEMED to pass for him. What did I say about the observers on earth? I said that as they watched the progress of the starship years and years passed. Family members died and societies changed. But it seemed just weeks for the traveler.
     
    Last edited: Mar 4, 2023
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  11. WillReadmore

    WillReadmore Well-Known Member

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    Yes - it still took the required time for the traveler, but the clocks on the ground were entirely different, and would be especially different for those watching a trip as far as an exoplanet!

    For those traveling to Proxima B at half the speed of light, it would still take them 8 years out and 8 years back in their own time frame.
     
  12. Kode

    Kode Well-Known Member

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    What would be “the required time for the traveler”? Clocks on the ground would be “entirely different”? You’re not being specific. Could you be?

    Yea and “their own time frame” would clock it at 7 years there and 7 years back for them. So they would come back 2 years younger than they would be if they didn’t go because 18 years would have passed on earth.
     
    Last edited: Mar 4, 2023
  13. WillReadmore

    WillReadmore Well-Known Member

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    Yes - the clocks carried by the satellite headed for Proxima b run at one second per second, as do the clocks on Earth. Yet, the clocks do not compare as equal after the trip. The reason is that the two clocks did not take the same path through space-time.

    This has been fully tested. It's what Einstein stated in his theory of general relativity. That gets tested every day. More directly, precision clocks have been put on the ISS and compared with the same precision clocks running on Earth. The ISS astronaut's clocks run at precisely one second per second, and that is the rate that astronauts age. The Earth clocks run at one second per second and that is the rate at which Earthlings age. Yet, they do not compare as equal at the end of the trip.

    Earth and the astronauts just didn't take the same path through space-time.

    The astronauts would have aged the same number of years as they would have if they had been anywhere else. It's just that their trip through space-time didn't take the same path as Earth took.
     
  14. Kode

    Kode Well-Known Member

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    But if the clock on earth could be watched side-by-side with the clock on the ISS (maybe with a remote video?), the one on the ISS would be seen to run a teeny bit slower than the one on earth. They would not match.
     
    Last edited: Mar 4, 2023
  15. WillReadmore

    WillReadmore Well-Known Member

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    Yes, the general theory of relativity shows that result. The issue has to do with the differences of the two frames of reference. They are traveling through space-time on different paths.

    Adding communications techniques is a complexity, as communications is limited by light speed, too. Trying to synchronize time between two different frames of reference is a hard problem, at least until the two clocks are brought to being adjacent - one frame of reference.

    You could also flip around and decide that the space craft is the frame of reference you want to use. Earth is just one choice. Earth is traveling through space-time, too - just not on the same path as the spacecraft.
     
  16. Kode

    Kode Well-Known Member

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    Right. Communications creates a complexity. As you said you could just have one clock on earth and one in the craft and then compare then upon return to earth.
     
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  17. WillReadmore

    WillReadmore Well-Known Member

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    https://en.wikipedia.org/wiki/Alcubierre_drive

    One idea.

    Engineering is hard enough. But, when one depends on defying physics, I get off the train.
     
    Last edited: Mar 12, 2023
  18. politicalcenter

    politicalcenter Well-Known Member

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    I don't want to become so educated that I lose the fantasy of interstellar travel in real time... A Galactic Empire composed of different worlds involved in universal trade and tourism.
     
  19. WillReadmore

    WillReadmore Well-Known Member

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    I know what you mean.

    Scifi and CGI have so outstripped physics and engineering that the real world we live in gets seen as a buzz kill.
     
    Last edited: Mar 12, 2023
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  20. Mushroom

    Mushroom Well-Known Member

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    Hell, the time dilation has been proven over half a century ago, and has been repeated countless times since then simply by using commercial aircraft.



    And they already know the clocks on the ISS run slower. By 0.014 seconds per year.
     
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  21. Nwolfe35

    Nwolfe35 Well-Known Member

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    One of the best SF novels EVER has this idea as one of it's central themes.

    The Forever War by Joe Haldeman follows the career of one soldier in a war against an alien species. Every time he goes out on a mission and returns years have passed on earth. His family ages. His "younger" brother becomes older than him. Eventually the entire society of earth becomes alien to him.
     
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  22. WillReadmore

    WillReadmore Well-Known Member

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    The point I was making is that even if you traveled to the nearest exoplanet 4 light years away at the speed of light, the astronauts on the round trip would age the full 8 years. Photons from that planet take 4 years to get to Earth, and physics won't let us go faster than that. Of course, we can't come anywhere near that speed.

    With current technology, it would take a tiny object more than 6,000 years reach the nearest planet outside our solar system. And, 6,000 more to come back! So, you can experiment with that number. For example, if we could go 10X faster, it would mean only 600 years. Plus, one better not hit any dust particles along the way.

    Expanding the payload to include humans and supplies would add to the energy requirement, as that is a lot of mass to accelerate.

    I agree that upon return the spaceship clock would be substantially different than the Earth clock. But, the spaceship would have aged as per the above. So, the astronauts arriving back on Earth would be the great great great grandkids of the astronauts who left on the trip.
     
  23. politicalcenter

    politicalcenter Well-Known Member

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    How ya gonna get several tons of mass .....at earth gravity....to 99% of light speed?
     
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  24. WillReadmore

    WillReadmore Well-Known Member

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    Yes. And, if the trip is going to take more than 50 years and have humans aboard, it starts becoming necessary to solve multigenerational space flight.

    Plus, what are the chances that a baby born in low gravity could survive - or ever be able to live on Earth?

    We talk about having a Mars colony. But, what are the chances that a baby born on Mars could visit Earth?
     
  25. politicalcenter

    politicalcenter Well-Known Member

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    Maybe a genetically modified human With Tartigrade DNA mixed in. I wonder how food would be supplied for a long journey.
     

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