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Is Faster-Than-Light Travel or Communication Possible? (1997)

math.ucr.edu

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Re: Is Faster-Than-Light Travel or Communication Possible? (1997)

#71

Post by mjevans »

jandrese wrote: post #68
mariodiana wrote: post #47

Earlier quoted context omitted.

Can you or someone else "explain to me like I'm five" why faster-than-light travel violates causality?

Effectively, the speed of light is the rate at which Cause and Effect propagate through the universe. The speed of light isn't an intrinsic property of light, it just so happens that light travels that fast and it was the first thing we were able to measure that was traveling at the limit. If you were traveling at FTL velocities, you would effectively get there before you left.

What if you arrived at some point after you actually left? (Not the other data of you leaving arriving at that point)

Granted I believe that doing so would probably involve bending space/time so that your actual position was in the new frame.

Re: Is Faster-Than-Light Travel or Communication Possible? (1997)

#72

Post by mariodiana »

euyyn wrote: post #61
mariodiana wrote: post #47

Earlier quoted context omitted.

Can you or someone else "explain to me like I'm five" why faster-than-light travel violates causality?

It's one of a bunch of mathematical conclusions of Special Relativity (the most famous one being that objects at rest have a "kinetic" energy of mc^2). I'll try to explain it simply, without the math: Imagine a friend and you, moving very fast with respect to each other. You measure your friend's clock as advancing slowly (due to time dilation), on account of the fact that he's moving with respect to you. But your fr…

I want to make sure I understand "time dilation," as you describe it. I have no formal background in science or math. So, please bear with me. For the sake of making the math easy, I'm going to talk about traveling faster than the speed of light, but only for the sake of argument. You'll see why.

I understand it this way. Assume I were traveling away from my friend at twice the speed of light. My time of departure is 12:00:00. After 1 second (my clock) I have traveled 2 light-seconds. Light reflected off the face of my clock now travels towards my friend, reading 12:00:01. We'll call this view of my clock a "snapshot."

From my friend's point of view, that snapshot reaches him at 12:00:03. Yes?

Now, we allow for 1 additional second, my time. I have traveled in total 4 light-seconds. My 12:00:02 snapshot now travels towards my friend. It reaches him at 12:00:06, his time. Yes?

So, from my friend's point of view, my time has seemed to slow down. Is that what you mean by time dilation?

Re: Is Faster-Than-Light Travel or Communication Possible? (1997)

#73

Post by krapp »

mjevans wrote: post #71
jandrese wrote: post #68

Earlier quoted context omitted.

Effectively, the speed of light is the rate at which Cause and Effect propagate through the universe. The speed of light isn't an intrinsic property of light, it just so happens that light travels that fast and it was the first thing we were able to measure that was traveling at the limit. If you were traveling at FTL velocities, you would effectively get there before you left.

What if you arrived at some point after you actually left? (Not the other data of you leaving arriving at that point) Granted I believe that doing so would probably involve bending space/time so that your actual position was in the new frame.

You're still getting there at a point in time earlier than the universe permits. This is essentially the same as traveling backwards in time, and violating causality by allowing effect to precede cause.

Re: Is Faster-Than-Light Travel or Communication Possible? (1997)

#74

Post by mariodiana »

jandrese wrote: post #68
mariodiana wrote: post #47

Earlier quoted context omitted.

Can you or someone else "explain to me like I'm five" why faster-than-light travel violates causality?

Effectively, the speed of light is the rate at which Cause and Effect propagate through the universe. The speed of light isn't an intrinsic property of light, it just so happens that light travels that fast and it was the first thing we were able to measure that was traveling at the limit. If you were traveling at FTL velocities, you would effectively get there before you left.

> If you were traveling at FTL velocities, you would effectively get there before you left.

To be more exact, aren't you saying that you would seem to get there before you left, from the point of view of someone not traveling with you who is observing you from some particular vantage point?

Re: Is Faster-Than-Light Travel or Communication Possible? (1997)

#75

Post by kirykl »

mariodiana wrote: post #74
jandrese wrote: post #68

Earlier quoted context omitted.

Effectively, the speed of light is the rate at which Cause and Effect propagate through the universe. The speed of light isn't an intrinsic property of light, it just so happens that light travels that fast and it was the first thing we were able to measure that was traveling at the limit. If you were traveling at FTL velocities, you would effectively get there before you left.

> If you were traveling at FTL velocities, you would effectively get there before you left. To be more exact, aren't you saying that you would seem to get there before you left, from the point of view of someone not traveling with you who is observing you from some particular vantage point?

would the observer's time slow down enough to run negative (backwards) from the POV of those traveling FTL ?

Re: Is Faster-Than-Light Travel or Communication Possible? (1997)

#76

Post by Zenst »

clock_tower wrote: post #67
Zenst wrote: post #2

Nice list and currently no. But many theory's that say it is possible, no experiments shown it to happen and indeed faster than light gets for many down to causality. Not saying it is impossible, but in theory anything is possible until proven or disproven. Another article that raises the same question is http://www.bbc.com/future/story/20150318-will-we-ever-speak-... Now one aspect I'll add is that it may be possibl…

When exactly were people burned alive, or killed in general, for saying the earth isn't flat? The first article of the _Summa Theologica_ discusses how to prove that the world is round; no Christian took Genesis' cosmography particularly seriously until biblical literalism and the Reformation. You might be thinking of the heliocentricism mess; but Bruno was burned for beliefs that had nothing to do with heliocentrici…

http://www.biographybase.com/biography/Bruno_Giordano.html

Yip your right, my mistake, good to learn. Least none can name and was indeed thinking of Bruno at the time, my bad.

Thank you for the correction and sorry for the misconception correction by me.

Re: Is Faster-Than-Light Travel or Communication Possible? (1997)

#77

Post by zo1 »

mariodiana wrote: post #72
euyyn wrote: post #61

Earlier quoted context omitted.

It's one of a bunch of mathematical conclusions of Special Relativity (the most famous one being that objects at rest have a "kinetic" energy of mc^2). I'll try to explain it simply, without the math: Imagine a friend and you, moving very fast with respect to each other. You measure your friend's clock as advancing slowly (due to time dilation), on account of the fact that he's moving with respect to you. But your fr…

I want to make sure I understand "time dilation," as you describe it. I have no formal background in science or math. So, please bear with me. For the sake of making the math easy, I'm going to talk about traveling faster than the speed of light, but only for the sake of argument. You'll see why. I understand it this way. Assume I were traveling away from my friend at twice the speed of light. My time of departure is…

Try not to think of time-dilation in relation to "light travelling". Time dilation just means that time passes more slowly for you due to your speed relative to an observer. So imagine you have an identical twin, and you leave on a Journey to a nearby solar system at say 0.9x the speed of light. Your twin stays on earth and for arguments sake you can say he is "stationary" in comparison to you.

When you come back, he'll be much more "aged" than you. You had a clock on-board your craft, and it measured your trip as say "2 years". Likewise, your twin also had a clock and it measured your trip as having lasted "20 years". The clocks are not wrong. And trust me, this isn't some science-fiction type thing we're discussing. GPS satellites orbiting the Earth carry very accurate atomic-clocks, and they need to take time-dilation into account in order to compensate for the drift in values, simply due to the accuracy necessary for GPS. Just had a look on the wiki page, and the drift is approximately 38 microseconds per day.

When I first encountered this concept in high-school randomly, I was quite shocked at how "non-complicated" the equation for it is.

https://en.wikipedia.org/wiki/Time_dilation#Simple_inference...

https://en.wikipedia.org/wiki/Global_Positioning_System

Re: Is Faster-Than-Light Travel or Communication Possible? (1997)

#78

Post by kamaal »

grymoire1 wrote: post #62
dcherman wrote: post #44

Earlier quoted context omitted.

What I've always found interesting (not sure if there's a name for this) is kind of the idea that if you made such a trip, you might find by the time you arrive there in 3.2 seconds, the rest of humanity has figured out true FTL travel with the technology that was developed during those 32,000 years. As a result, you arrive in what might be the equivalent of a horse and buggy at the center of the galaxy versus what e…

Lots of science fiction stories have this concept, but usually they talk about Slower-than-light, multi-generational space ships that takes centuries to reach the next star, only to find that during the last 100+ years, the destination planet has already been settled by humanity.

The wealthiest leave early thinking they might be getting the best and the first.

Poorer people leaving later get better and faster transit.

The only advantage of leaving early is the guarantee of getting a transit, instead of waiting for a better one to arrive later and find you got nothing at all.

Re: Is Faster-Than-Light Travel or Communication Possible? (1997)

#79

Post by kamaal »

3pt14159 wrote: post #70
sevenless wrote: post #42

Earlier quoted context omitted.

> This is one of my theories about why there isn't any alien life around. Do we need a theory on this yet? I mean... out of all the planets we've explored reasonably thoroughly so far, 100% have had life at some point.

Uh, yeah? Von Neumann machines should be everywhere by now; yet there is no evidence of them.

Life yes. Intelligent life, no.

Intelligence might not even bet he end goal of evolution even life is very common, intelligence might not be.

Re: Is Faster-Than-Light Travel or Communication Possible? (1997)

#80

Post by kamaal »

jandrese wrote: post #17
aaron695 wrote: post #16

Thinking you can go faster than light for communication is the same as believing perpetual motion or even being a flat earther. You can't do it, there are no hacks to do it. It's a law of the universe. No matter how many SciFi movies tell you other wise. I just don't get the acceptance of this anti-scientific concept.

This is exactly right given our current understanding of the universe. FTL travel violates causality, which is a fundamental principle of the universe. I wouldn't go quite so far as to say it's totally impossible though. There is a whole lot about the universe we don't understand and I can't rule out the possibility that there are entire branches of mathematics and physics that we don't know about.

>>fundamental principle of the universe.

Fundamental principles of the universe also say heavier than air machines should be impossible.

FTL issue is the same thing. Its possible, it just won't happen in the way we might expect.

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