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flowersonthewall72 t1_j1gikrk wrote

Reply to comment by hhhhqqqqq1209 in Did you know it will still take 46 billion years to cross the universe at the speed of light? 65 mph = 4.8 * 10^17 years! by NotAndroid545

Umm no sorry that isn't right... light speed is not instantaneous. On a small scale (earth sizes) it could reasonably be considered instantaneous, but anything bigger, not a chance. Light takes 8 minutes to get from the sun to earth and that distance is absolutely minuscule on the galactic and cosmic scale.

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EchinusRosso t1_j1gj4zr wrote

Light takes 8 minutes to get to earth for an outside observer. For the object moving at light speed, a photon in that case, it's instantaneous. This is basic relativity.

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Suekru t1_j1hmfen wrote

Light takes 8 minutes from the sun to earth. That implies if you were to travel the speed of light, it would take 8 relative earth minutes for you to make it the distance of the sun is from earth.

But your perspective of time would be almost instantaneously.

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EchinusRosso t1_j1itnmg wrote

Not almost instantaneous. It would be actually instantaneous. It would take you 0 seconds to go from the sun to the earth, or from the sun to Andromeda.

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hhhhqqqqq1209 t1_j1gixi3 wrote

Not to the photon. It’s instantaneous. If you are traveling at the speed of light (which is impossible unless you have no mass) the time to you would be 0, regardless how far you travel.

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sdfree0172 t1_j1gjjti wrote

I think hhhqqqqq1209 gets that. It’s that the 46 billion light years it takes for you to cross the universe is only from the perspective of an observer from earth. However, time is compressed for the traveler as you travel near the speed of light and it is compressed infinitely at the speed of light. So, as the one traveling, you would not experience any time passing and arrive instantaneously (assuming infinite acceleration and deceleration, of course!).

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flowersonthewall72 t1_j1i28iu wrote

Your relative travel time might have been instantaneous, yes, but the universe around you experienced the relative normal flow of time. So while your trip may have been instantaneous, you've "traveled forward in time" as the universe aged while you were moving at light speed. So sure, your perspective was instant, but your resulting destination was not instant.

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[deleted] t1_j1grd7f wrote

[deleted]

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splittingheirs t1_j1h1mlc wrote

  • T^(trav)= t*(1-v^(2)/c^(2))^(1/2) where:
    t = time observed in the other reference frame
    T^(trav) = time in travelers own frame of reference
    v = the speed of the moving object
    c = the speed of light in a vacuum

observer (t) sees 1 000 000 years go past. Traveler's velocity (v) = c. So:
T^(trav) = 1000000*(1-c^(2)/c^(2))^(1/2)
T^(trav)=1000000*(1-1)^(1/2)
T^(trav)=1000000*(0)^(1/2)
T^(trav)=0
Time experienced by traveler traveling at c = 0 years.

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