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Author Topic:   Is Faster Than Light travel the wrong question?
Michamus
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 Message 1 of 81 (533202) 10-29-2009 10:43 AM

I've been thinking (and discussing with a few friends) SR (Special Relativity) and it's predictions on FTL (Faster Than Light) or LS (Light Speed) Travel being impossible for anything with rest mass 0<.

From what I understand, this has a lot to do with the exponential increase in energy required for the work of propelling whatever it is you want to propel up to that speed. (This may be incorrect as I am FAR from an expert on this subject).

I also understand that no matter the velocity of your FoR (Frame of Reference), LS is constant, hence it's representation as "C". (For those not quite sure what I mean: If you are traveling in a super fast car at .999C and turn on your headlights, the beams will still be traveling at C away from you.)

So my question is this, is FTL or LS travel really what we are after? What prevents us from traveling at 600,000km/sec, seeing as from our FoR light is still traveling at light-speed?

Edited by Michamus, : Fixed: no matter the velocity your FoR

Edited by Admin, : Minor edits for clarity.

Edited by Admin, : Define SR.

Edited by Adminnemooseus, : "FTL" to "Faster Than Light" in topic title.

 Replies to this message: Message 3 by Perdition, posted 10-29-2009 12:19 PM Michamus has not yet responded Message 4 by Meldinoor, posted 10-29-2009 5:46 PM Michamus has not yet responded Message 5 by kbertsche, posted 10-29-2009 7:34 PM Michamus has responded Message 10 by onifre, posted 10-30-2009 12:12 PM Michamus has not yet responded Message 12 by Aware Wolf, posted 10-30-2009 12:25 PM Michamus has responded

Director
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 Message 2 of 81 (533207) 10-29-2009 11:06 AM

Thread Copied from Proposed New Topics Forum
Thread copied here from the Is FTL travel the wrong question? thread in the Proposed New Topics forum.
Perdition
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Posts: 1593
From: Wisconsin
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 Message 3 of 81 (533229) 10-29-2009 12:19 PM Reply to: Message 1 by Michamus10-29-2009 10:43 AM

I think the problem comes from time dilation, meaning we'll see your headlights travelling at c as well, you'll just appear to be moving about your car very slowly.

But before I step to deeply over my head, I'll defer to Son Goku or cavediver if they happen to swing by on their less than FTL speed trip through the forum.

 This message is a reply to: Message 1 by Michamus, posted 10-29-2009 10:43 AM Michamus has not yet responded

Meldinoor
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 Message 4 of 81 (533277) 10-29-2009 5:46 PM Reply to: Message 1 by Michamus10-29-2009 10:43 AM

Hi Michamus,

I don't know much on the topic myself, and I expect cavediver will be around to explain it much better for you. But here's how I understand it:

Velocity is always relative. That is, for instance, there's no such thing as traveling at an absolute speed of 0.999c. It is always relative to some other object.
So while light will always be leaving you at the speed of light, the relative velocity, or change in position over time, will always be sub-light speed for any given reference frame.

However, because of length contraction, if you were able to approach some coordinate, say a distant star, at a speed close to the speed of light, the distance would appear much shorter, and you'd be able to get there quickly. From an observer on earth it is not the distance that is getting shorter, but your spaceship. The observer would see time dilate on your ship, but would experience it as if your ship took many years.

So if you really wanted to get to a distant object within your lifetime, you would never have to exceed the speed of light. Just don't expect your friends to still be waiting for you when you get back.

Respectfully,

-Meldinoor

 This message is a reply to: Message 1 by Michamus, posted 10-29-2009 10:43 AM Michamus has not yet responded

kbertsche
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 Message 5 of 81 (533286) 10-29-2009 7:34 PM Reply to: Message 1 by Michamus10-29-2009 10:43 AM

quote:
So my question is this, is FTL or LS travel really what we are after? What prevents us from traveling at 600,000km/sec, seeing as from our FoR light is still traveling at light-speed?

What is your goal? What are you trying to achieve?

Meldinoor explained things pretty well, I think. At near the speed of light you could travel a large distance without aging very much. You would want to accelerate as fast as tolerable for as long as possible, perhaps even for half the travel time, then decelerate the same way. An acceleration of 1G for 1 year would give a relative velocity of about 0.7 c, and you would age at about 70% the normal rate. You'd need multi-G's of acceleration for multi-years to get large factors of time dilation.

The energy expenditure for this would be enormous, of course. That's why sci-fi scenarios of sending people to colonize distant planets are complete fantasy. It would require an energy source which is nearly infinite and essentially free.

Edited by kbertsche, : Bad back-of-envelope calculation.

Edited by kbertsche, : Added correct values for 1G and 1 year.

 This message is a reply to: Message 1 by Michamus, posted 10-29-2009 10:43 AM Michamus has responded

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Taz
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 Message 6 of 81 (533311) 10-30-2009 12:20 AM Reply to: Message 5 by kbertsche10-29-2009 7:34 PM

 kbertsche writes:The energy expenditure for this would be enormous, of course. That's why sci-fi scenarios of sending people to colonize distant planets are complete fantasy. It would require an energy source which is nearly infinite and essentially free.

Rrhain and I had a similar argument about this very thing. Here is my perspective on the matter of interstellar travel. But first, I need to reiterate what you said in terms that people from the age of sails could understand.

The wind speed to carry a ship from Europe to North America in a few days would be enormous, of course. That's why sci-fi scenarios of sending people to distant lands are complete fantasy. It would require wind speed that is nearly impossible to imagine.

If it's not obvious yet, I'm trying to point out that you are approaching this problem with a very 20th-21st century way of thinking, just like how a person from the 16th century would think about intercontinental travel. Flight never occurred to them. Bullet train never occurred to them. Underwater tunnels never occurred to them. To them, getting from Europe to the Americas or Asia in less than several months time would be nothing more than fantasy.

In very much the same way, you're superimposing our limited understanding of physics onto all the great inventions and discoveries waiting for us in the future. Sure, it may be fantasy now, but who knows what the future holds?

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CosmicChimp
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 Message 7 of 81 (533355) 10-30-2009 10:06 AM Reply to: Message 6 by Taz10-30-2009 12:20 AM

I like your hope (and it is my hopeful wish as well); but I have heard, even just recently in a podcast, that the speed of light barrier is a limit and then a limit forever.

Here's the info page on that podcast, it's the interview with Michael Vasser of the Singularity Institute.

I know there are better sources for this kind of material but the interview is immensely interesting, even if it is about AI and hardly about FTL travel.

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Perdition
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 Message 8 of 81 (533362) 10-30-2009 10:58 AM Reply to: Message 7 by CosmicChimp10-30-2009 10:06 AM

 the speed of light barrier is a limit and then a limit forever.

But, what if we could bypass the limit. If we shorten the distance between point A and point B, we can make the trip very quickly, yet still travel significantly less than c.

This could either be done by wormholes, or by some sort of space warp technology. You expand space behind you, contract space in front of you, and voila.

Of course, we have no idea how to do this yet, but crazy ideas that inspire imagination are the keys to advancement.

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kbertsche
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 Message 9 of 81 (533365) 10-30-2009 11:45 AM Reply to: Message 6 by Taz10-30-2009 12:20 AM

fantasy
quote:
Rrhain and I had a similar argument about this very thing. Here is my perspective on the matter of interstellar travel. But first, I need to reiterate what you said in terms that people from the age of sails could understand.

The wind speed to carry a ship from Europe to North America in a few days would be enormous, of course. That's why sci-fi scenarios of sending people to distant lands are complete fantasy. It would require wind speed that is nearly impossible to imagine.

You lock your mindset into a particular technology (wind power). I specifically did NOT do this.

In addition, your analogy is poor. The wind speed wouldn't need to be unimaginably high, just high and steady.

quote:
If it's not obvious yet, I'm trying to point out that you are approaching this problem with a very 20th-21st century way of thinking, just like how a person from the 16th century would think about intercontinental travel. Flight never occurred to them. Bullet train never occurred to them. Underwater tunnels never occurred to them. To them, getting from Europe to the Americas or Asia in less than several months time would be nothing more than fantasy.

No. My comments are not locked into "20th-21st century way of thinking." They are locked into physical reality. But they allow for new energy sources.

quote:
In very much the same way, you're superimposing our limited understanding of physics onto all the great inventions and discoveries waiting for us in the future. Sure, it may be fantasy now, but who knows what the future holds?

No. My comments do not depend on "our limited understanding of physics." I have explicitly left room for new energy sources and new physics by saying that this "would require an energy source which is nearly infinite and essentially free."

For a society which is worried about energy costs and limited energy availability, sending large groups of people to colonize distant planets is pure fantasy. Doing so would require a new energy source, and we would no longer be a society which is worried about energy costs and limited energy availability.

 This message is a reply to: Message 6 by Taz, posted 10-30-2009 12:20 AM Taz has responded

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onifre
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 Message 10 of 81 (533367) 10-30-2009 12:12 PM Reply to: Message 1 by Michamus10-29-2009 10:43 AM

 So my question is this, is FTL or LS travel really what we are after?

Faster than light speed, as I understand it, is a nonsensical question.

As I understand it, or as Cavediver explained it and i think I undestood it, lol:

Everything (with mass) travels at the speed of light (300,000 m/s) we just do so in the temporal direction, which is to say, we experience time at 300,000 m/s.

When you speed up, you are doing so in the spacial direction.

By doing so, you are taking that speed of light (experienced time) from the temporal direction and rotating it to the spacial direction, so "speed" thru space is basically "time experienced". So when you speed up you are basically just shortening experienced time.

Light doesn't experience time (0 rest mass), and it travels at a *speed* of 300,000 m/s; so as you start to speed up spacially, and equally start to experience time slower, the closer you get to not experiencing time at all, the closer you get to 300,000 m/s.

So, if I understood cavediver correctly, you can't experience time any less than not experiencing time at all (as with light) so you can't exceed 300,000 m/s - IOW, you can't experience time any *slower* than 300,000 m/s.

I hope this made sense. lol

- Oni

Edited by onifre, : No reason given.

Edited by onifre, : No reason given.

 This message is a reply to: Message 1 by Michamus, posted 10-29-2009 10:43 AM Michamus has not yet responded

Taz
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 Message 11 of 81 (533368) 10-30-2009 12:20 PM Reply to: Message 9 by kbertsche10-30-2009 11:45 AM

Re: fantasy
 kbertsche writes:No. My comments do not depend on "our limited understanding of physics." I have explicitly left room for new energy sources and new physics by saying that this "would require an energy source which is nearly infinite and essentially free."For a society which is worried about energy costs and limited energy availability, sending large groups of people to colonize distant planets is pure fantasy. Doing so would require a new energy source, and we would no longer be a society which is worried about energy costs and limited energy availability.

There you go again, superimposing our limited understanding of physics to future inventions and discoveries.

Just like the people in the 16th century who couldn't imagine any other way to travel from continent to continent other than by sail boats, you are locked into this mindset that interstellar travel can't be anything other than projectile motion through space, which of course would indeed require an enormous amount of energy.

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Aware Wolf
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 Message 12 of 81 (533369) 10-30-2009 12:25 PM Reply to: Message 1 by Michamus10-29-2009 10:43 AM

I'm about as qualified to discuss SR as I am to play power forward in the NBA, however:

I have seen Cavediver (I think) describe travel through space-time like a vector: we are all "moving" at a constant rate through space-time; but the ratio of our rate of travel through space to our rate of travel through time can change.

Picture a meter stick pointing straight up. This represents an object "standing still" in space in a particular FOR. Because it is not moving in space, it is moving as fast as possible through time. Now tip the meter stick over 5 degrees. The overall rate of travel through space-time (the lenght of the meter stick) has not changed, but now the object is moving slowly through space, and is moving somewhat slower through time than it was before. As the object speeds up through space, the meter stick tips more and more.

If I understand it correctly, when the meter stick reaches the horizontal, that represents an object moving at LS. You can't go faster than this because you can't get the meter stick to deflect horizontally any more than this.

Don't ask me what it means to continue tipping the stick so it starts to point down, or if this is even possible.

Edited by Aware Wolf, : Clarity, I hope.

 This message is a reply to: Message 1 by Michamus, posted 10-29-2009 10:43 AM Michamus has responded

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Perdition
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 Message 13 of 81 (533379) 10-30-2009 1:20 PM Reply to: Message 12 by Aware Wolf10-30-2009 12:25 PM

 Don't ask me what it means to continue tipping the stick so it starts to point down, or if this is even possible.

IF it were possible, that would indicate moving backwards through time...or so I would imagine.

Edited by Perdition, : No reason given.

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kbertsche
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 Message 14 of 81 (533385) 10-30-2009 2:03 PM Reply to: Message 11 by Taz10-30-2009 12:20 PM

Re: fantasy
quote:
There you go again, superimposing our limited understanding of physics to future inventions and discoveries.

No. I am superposing reality and what we know of physics.

quote:
Just like the people in the 16th century who couldn't imagine any other way to travel from continent to continent other than by sail boats, you are locked into this mindset that interstellar travel can't be anything other than projectile motion through space, which of course would indeed require an enormous amount of energy.

Transporting matter at relativistic velocities requires energy. Transporting matter is the topic of the OP and the thread. If you want to consider some sort of non-material travel (astral projection or whatever), that's fine, but it is not the topic of the OP. If you want to imagine a universe where all of the laws of physics are completely different than ours, that's fine, too. But it is completely disconnected from reality. It is pure fantasy.
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Perdition
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 Message 15 of 81 (533387) 10-30-2009 2:09 PM Reply to: Message 14 by kbertsche10-30-2009 2:03 PM

Re: fantasy
 Transporting matter at relativistic velocities requires energy. Transporting matter is the topic of the OP and the thread.

The science at one time said breaking the sound barrier was impossible, so it's also possible (though I would admit unlikely) that the light speed limit is not quite as absolute as we think it is.

There's also the fact that we can get the same results as FTL travel without the actuality of it. As I said earlier in the thread, wormholes, space warping, etc may get us great distances in short times by altering the fabric of space itself to make the trip shorter. While this may seem "far-out" and "fantasy" there are physicists working on this sort of thing. So, what you're stuck in, is the mentality that to get from point A to point B, you necessarily have to travel through all the points in between...that's a 20/21 Century way of seeing it.

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