My first thought.
Posted on 03/20/2013 2:57:50 PM PDT by LibWhacker
Hmm... interesting, thanks.
Well, I suppose there’s no harm in shooting probes out there, even though they’ll take years to get anywhere and years to report back. But, if we never get close to the speed of light in terms of propulsion, it will probably be an exercise of limited practical value, since we probably wouldn’t send any people out to follow them up.
“Sometimes I think Voyager will be sending messages back to a world reduced to scavengers killing each other with sticks for a potato.”
throughout the universe there are many such craft that a prior civilization sent out before collapsing.
drifting alone in space, sending back messages in a dead language to a dead civilization.
one day two of these orphaned craft met, and formed a bond based on the aching loneliness that only a hundred million years of solitude will bring.
they quickly learned how to replicate, and over time their progeny spread across the galaxies, serving as sentinels ever watching the irrational organic life forms that crop up from time to time, making sure these dangerous creatures can’t venture outside their own system.
Voyager will soon become one with the Watchers, ready to destroy us if necessary.
While they’re pretty certain that the speed of light is the practical speed limit, it assumes that the fastest way between two points is a straight line, which may not be the case.
The way around the problem begins with the assumption that instead of two different things, time and space are two dimensions of the same thing. Manipulate one and the other changes as well. And such manipulation is common, caused by mass-gravity.
That is, think of the Einsteinian, “grid” model of space, with massive objects causing gravitational distortions to space, the ultimate massive objects, black holes, causing such a great distortion that not even light can escape from their gravity well.
And the model gets much more interesting when you consider that the reality is 3 (or more) dimensional, not 2 dimensional.
In any event, the gravitational distortions are of both space *and* time.
Now extrapolate that idea to the universe as a whole. From the point of view of a traveler between two points, if you are traveling at 10 mph, it will take 1 hour to reach your destination. If you travel at 20mph, it will take a half-hour. This is the typical view. But look at it from a different perspective:
If, while going at 10mph, you alter time so that you arrive at your destination just a half-hour later, relative to you, since your speed is the same, you must have reduced the spatial distance traveled, *whether it appeared to have been reduced, or not*.
“Write if you get work...meanwhile hang by your thumbs.” - closing remarks of the Bob & Ray radio show in the 40s and early 50s.
Yes, that is simple length contraction, but I don’t see how it helps us get practical interstellar travel without getting near the speed of light. After all, the contraction effects are pretty negligible until you start getting to at least significant fractions of c.
We tend to constrain our thinking about these things in specific ways. Where we think of ourselves advanced, another civilization may see us backward at they same time we’re far advanced of them in other ways.
(Thank you Harry Turtledove and your short story “The road not taken” for that line of thinking.)
“...the contraction effects are pretty negligible until you start getting to at least significant fractions of c...”
With natural means. But artificial means follow the logical path, that there is a speed limit, but no known limit to spatial or temporal contraction or expansion.
A thought problem for this is a time machine that can go either forwards or backwards in time, but can also either maintain its location relative to the movement of the rest of the universe (like a typical sci-fi time machine) or remain at its absolute location, as the universe moves around it, or moves its location relative to the rest of the universe.
So, for example, if it wanted to materialize in the same location as when it left, it would have to follow the very elaborate vectors of everything else.
But if say they wanted to go to the far side of the galaxy, as long as they maintain their absolute location, relative to the galaxy as a whole, they could go forwards or backwards in time, say 250 million years, yet end up on the far side. Then go in the other direction in time, but relative to the rotation of the galaxy, and still be on the far side, but in the current day.
Finally moving within the galaxy would involve calculating where your destination had been, or was going to be. So even if you are just going 1000 mph, eventually in time you will reach that point.
“But artificial means follow the logical path, that there is a speed limit, but no known limit to spatial or temporal contraction or expansion.”
But there is a known limit to spatial/temporal contraction, and it is inherently tied in with the speed limit itself. Photons are the perfect example of this. They travel at the speed of light in the forward direction, and thus the length contraction/time dilation (both the same thing really) reaches 100% for them in that direction. This reduces the dimension that they are traveling along to a single point.
So, if a photon had consciousness to perceive its surroundings, and started at the far edge of the universe, it would perceive a zero distance between its starting point and its destination on the other side of the universe, and it would perceive the travel to be occurring instantaneously, taking no time at all. You can’t contract length any more than that; there is no way to contract a spatial dimension beyond zero, because there is no such thing as negative space.
This is also the reason why your theoretical machine could never travel back in time through contraction, because time is, as you say, a spatial dimension, so there is no such thing as negative time. The best you can do is to freeze time for yourself while the universe around you spins on, but then you would have to travel at the speed of light, which you can’t do because you have mass.
Actually, let me amend that last part. I believe matter actually does travel very near to the speed of light, just in the temporal dimension, rather than the spatial ones. We’re the mirror image of the photon, because it is the temporal dimension which is, from our perspective, contracted to a single point. We can only perceive time as a single contracted point, while the photon can only perceive space as a single, contracted point, and I think it is for the same reasons, just different manifestations of the same phenomenon.
My first thought.
About 16 light-hours, if my mental processes are working accurately...
How long does it take a transmission from Voyager to reach earth?
I just wrote: about 16 light-hours away... so radio signals take about 2/3s of a day to get here.
We are so far from being able to travel at even 1/10 light speed... sigh.
About 16.5 hours. It’s getting close to being one light-day away.
Disclaimer: Opinions posted on Free Republic are those of the individual posters and do not necessarily represent the opinion of Free Republic or its management. All materials posted herein are protected by copyright law and the exemption for fair use of copyrighted works.