The Slowness of Time Means the Starship Enterprise Will Never Be Built

NCC-1701

NCC-1701 (Photo credit: Wikipedia)

The slowness of time. The speed of light, while fast, is not infinite. Light takes time to travel from one place to another. Einstein proved that nothing can travel faster than the speed of light. It is the speed limit built into the nature of space and time.

The Universe has a speed limit. This creates some weird effects. We cannot witness these weird effects in the everyday human world, because the speed of light is so much faster than anything in our daily experience. But the effects are very real: clocks in satellites measure time a little differently than clocks on the surface of the Earth, as Einstein’s theory predicts.

What are “simultaneous” events? Suppose there are a number of space colonies in different star systems that are more or less in a line. Call them A, B, C, D, and E. Each is about 10 light years apart.

Let’s make this an exciting story.

Stars A and E unexpectedly go supernova, and the humans have to evacuate into hyperspace. Colony B sees the light from star A’s explosion before colony C sees it. Colony C sees the explosion before colony D sees it. Colony D sees the light before colony E sees it.

The reverse is true of the light from the explosion of star E, which travels first to D, then C, B and finally A.

Light from star A’s explosion reaches colony C in their year 72, which is 72 years after their founding. That same year, the light from star E’s explosion also reaches them. They write in their history books, “Stars A and E both were observed to go supernova this year!”

The history books of colony B would read differently. The light from star A reached them 10 years before it reached colony C. Then again, the light from star E reached them 10 years *after* it reached colony C. Therefore, their history records would say, “Star A was observed to go supernova, and 20 years later star E was observed to go supernova.”

Neither history is incorrect. The colonies really did observe the events happen at those times.

When the citizens of colony E come out of hyperspace, they will consider the damage to their colony world and begin to file lawsuits against the insurance companies, which will probably need a bail-out. These lawsuits could still be in progress 40 years later, when the light from the explosion of star A reaches them.

Therefore, star E’s history books say, “40 years after our star went supernova, colony A’s star was observed to go supernova, too.”

Of course, star A’s history books would record the fact that their own star went supernova, and 40 years afterward star E was observed to also go supernova.

We have not yet mentioned colony F, which is 10 light years further away than colony E. Colony F’s history books would agree with colony E’s, observing star E going supernova 40 years earlier than star A.

On the other hand, colony Zero is 10 light years further away than colony A. It is 20 years from colony B, 30 from colony C, and so forth. Colony Zero’s history would agree with colony A’s, observing star A going supernova 40 years earlier than star E.

Which supernova happened first? Einstein said that this was a meaningless question. The sequence of events is relative to the observer’s frame of reference. It is relative to their location and their speed.

Sorry, Kirk!

Bad news for Captain Kirk! To build Captain Kirk’s warp drive, Starfleet would have to figure out when the Enterprise, traveling from colony A to colony E, would pass through colony C. The idea that there is an absolute frame of reference — called “hyperspace” — that the Enterprise can zip around in, popping out into “normal space” at colony C to pick up more dilithium crystals, is impossible.

There is no absolute frame of reference that ties together the universe into a single NOW. There is only the current frame of reference, from which different events in the past can be said to be observed simultaneously — and any frame of reference is equally valid.

………….

(Then again, consider the “slingshot manuver,” in which the Enterprise zooms very close to the Sun in order to travel into the past. When they want to return, they do it again. Why don’t they travel into the past again? Apparently the idea here is that it matters in which direction you travel while slingshotting!)

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2 Comments (+add yours?)

  1. Robert
    Jun 04, 2012 @ 04:51:10

    This theory seems wrong in that the events do happen at the same time, but are merely observed differently, with FTL travel allowing for a constant frame of reference. The refuges would arrive at their destination with proof of the destruction, which could be confirmed with a jump back to the supernova. It is how we know that, even if we were to magically jump to another galaxy, it would look different than it does from our point of view. That would not change its state though. The difference in time measuring is due to relative velocities and gravitational differentials, not distance. If FTL travel exists, theoretically FTL communication would as well, allowing for a constant frame of reference.

    Reply

    • Conrad Cook
      Jun 04, 2012 @ 11:14:29

      Dear Robert,

      To better understand the problem, suppose the speed of light were slow enough that you could walk *as fast* as it. But nothing can move faster.

      Now let’s say you and I agree to both turn on our flashlights “at the same time.” We agree to go by the clock in the wall in the room — when it reads 3:00.

      How do we get it right?

      To settle the problem of simultaneity, a pair of twins agrees to go to the clock, set their watches by it, and then walk as fast as they can to us — at the speed of light.

      They set their watches, and agree they read the same time. Now they walk to us as fast as they can.

      Because they’re walking at the speed of light, the watches on their wrists slow down and stop. We could say they begin walking at 3:00 precisely, and their watches still read 3:00 when they arrive.

      When your twin reaches you, you turn on your flashlight. Later, you see me turn on mine.

      From my point of view, I see that I turn on my flashlight first, and then you do.

      Different observers in the room will disagree with which of us switched on before the other.

      In fact, we can imagine we have as many of these twins as we need, all running around the room and comparing watches. The problem is that their watches stop as soon as they start walking.

      So, two twins who leave at the same time and run around the room, bouncing between “mirror” observers, will never **run into each other** and disagree on what their watches say — but any one might arrive at an observer, linger to chat (the watch starts running), and later greet their newly-arrived twin who has the 3:00 reading on their watch.

      No time passes for photons.

      Reply

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