Space is the place

Out of context: Reply #207

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  • _niko0

    Ok this little problem has been stirring in my tiny brain for a while.

    sometime in the future, we build a telescope powerful enough to see distant planets in detail, so powerful in fact that we are able to see things like dates on a quarter in detail.

    we find a planet exactly a light-year away. We observe the planet and see that it is a thoroughly advanced civilization, more so than ours.

    what we see through the telescope happened exactly 1 year ago even though it looks like we're seeing it live.

    We observe that they have built a space ship and intend to travel to earth. The space ship is so advanced that it travels at the speed of light.

    We watch it blast off and escape the planet and head towards earth at light speed.

    Then instantly the spaceship arrives on earth, because the events we observe through the telescope happened a year ago, and it took the ship 1 year to get here.

    Is this correct? what about the journey of the ship? if we watch the blast off does the 1-year journey get condensed to an instant occurrence from our observable viewpoint? Are we viewing a speed-up of time? is that what time-dilation is?

    Thanks.

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    • so if the ship was slower than the speed of light and the journey took 10 years, and we fixed the telsescope on the ship, we would see the whole 10 year journey_niko
    • same with a 5 year journey or a 2 year journey, we would see it zooming out of its own solar system going through interstellar space, then zooming past our_niko
    • planets before finally reaching earth. We would see the journey. But in this case we wouldnt see the year long journey because it's going at the speed of light_niko
    • Yes, I think that's mostly correct. The part in question would be whether it's possible to observe matter moving at light speeds. It would be moving as...MondoMorphic
    • ...quickly as the observable light reflecting off it, meaning I don't think we would see the ship until a year later, at the moment it arrived on Earth.MondoMorphic
    • Which is basically what you were saying. And yes, for the sub-light example we'd see the (very rapid) trip. Time dilation refers to the ages of the people...MondoMorphic
    • ...on the ship and on earth; the rate at which both age. The person on the ship would not have aged while the person on Earth is 1 yr older.MondoMorphic
    • Pretty sure FTL is possible, we just didn't solved the Math involved yet.grafician
    • It’s similar to what is detailed in the arrow of time articles - a mindfuck for sure and hard to conceptualizeStatic_Line
    • Thanks guys, yeah interesting observations, more food for thought especially the question of are we able to observe things moving at the speed of light._niko
    • so now say there is a third planet, also advanced and also has a kick-ass space telescope. Both the earth's solar system and the rocket ship solar system_niko
    • ...are in their night sky. They zoom in on the rocket ship blasting off from planet x at the speed of light heading towards earth. The earth is a light year awa_niko
    • they should be able to track that ship for a year as it travels towards earth at the speed of light no? or does something weird happen while they're observing?_niko
    • That would depend largely on if the trajectory of the ship heading to Earth was also 1ly away. If any part of the trajectory is closer to or further away fromContinuity
    • ... the observer, that would have an effect on the length of time it takes for the light from the ship to reach the observer.Continuity
    • 'Rocket ship', though? This isn't the 1950s, mister!Continuity
    • And I might be out of my depth here, but even if the trajectory was perfectly perpendicular to the observer's line of sight, I don't think it would beContinuity
    • ... possible to visually track an object travelling at 1c.Continuity
    • You are correct Continuity. There is no way of observing. Btw light from our Sol reaches Earth in about 8 minutes! So if Sol would disappear in an instant, itgrafician
    • it would still take us about 8 minutes to notice it's missing from the sky lol then everything would go dark - forevergrafician
    • oh and btw it's only "c" in notations, not 1c or anything elsegrafician
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