## Speed of Light, and space travel.

Message boards : Science (non-SETI) : Speed of Light, and space travel.
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Jeff

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Message 765528 - Posted: 10 Jun 2008, 2:53:03 UTC

Ok, if I remember my high school and mandatory college physics classes, the speed of light is 186,000 miles per second in a vacuum. (299,792,458 metres per second)

Now, since it has been established that space is NOT a vacuum, there are various gases floating around, and as I understand it, A vacuum is a volume of space that is essentially empty of matter, such that its gaseous pressure is much less than atmospheric pressure.

The key word being essentially.

Now, given the following:

Space is not a perfect vacuum.

Would that not imply that the speed of light through space would be slower than the speed of light in a perfect vacuum?

And by that fact, would it then become possible to exceed the speed of light in an imperfect vacuum such as space?

If, in a vacuum, the speed of light is 26,981,512.2 meters per second, or 90% the speed of light in a vacuum, and a ship accelerates to 99%c, as dictated by the constant 'c', then the craft has essentially exceeded the speed of light.
ID: 765528 ·
Aristoteles Doukas

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Message 765577 - Posted: 10 Jun 2008, 6:30:44 UTC - in response to Message 765528.

the problem was not that you canÃ‚Â´t exceed speed of light but that it would take so much energy which would take so much mass which would lead that you need even more energy which makes the mass even bigger snd so on
"Sometimes I think the surest sign that intelligent life exist elsewhere in the Universe is that none of it has tried to contact us."
Calvin to the Hobbes
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Mr. Majestic
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Message 765579 - Posted: 10 Jun 2008, 6:38:24 UTC - in response to Message 765577.

the problem was not that you canÃ‚Â´t exceed speed of light but that it would take so much energy which would take so much mass which would lead that you need even more energy which makes the mass even bigger snd so on

Next time you may find it easier to just post E=MC^2 :)

The thing with your logic Jeff is this, if space itself is not a complete vacuum, then there is no where that there is a vacuum. This means that what we consider the speed of light in a vacuum would actually be the speed of light in the not quite vacuum, if that makes any sense at all. In other words, when referring to the speed of light in a vacuum we would actually be referring to the speed of light in "empty" space. This means that E=MC^2 would hold true, meaning the faster you travel the more your mass increases and thus the more energy it would take to move the object. Hence, if the object was to move at c it would take an infinate amount of energy to move it.

ID: 765579 ·
William Rothamel

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Message 766019 - Posted: 11 Jun 2008, 2:45:29 UTC

The vacuum is not quite empty. It has an average density of a molecule or two, in Quantum mechanics particles and anti-particles are popping into and out of existence all the time.

The Universe expands right now at a speed faster than light --i.e. the farthest reaches of space are receding from us at a speed exceeding that of light. During inflation of the early universe this was also true.

Regards,

Bill
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Misfit
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Message 766068 - Posted: 11 Jun 2008, 4:56:55 UTC - in response to Message 766019.

What if light were to fall directly into a galactic black hole (from its north pole so to speak), now "quiet" from gobbling up everything within it's influence? Since the black hole would have created a vacuum around it, and it's gravity effects light, could the light be accelerated past 180K/sec before it reached the singularity?
me@rescam.org
ID: 766068 ·
jim little

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Message 766261 - Posted: 11 Jun 2008, 17:27:08 UTC

On earth one can have significant volumes with zero atoms in several liters within the confines of an evacuated chamber immersed in liquid helium. And if desired one may reduce the temperature of the helium to abut 2 K where it becomes a super fluid. At this temperature a sealed container that originally was pumped by really good diffusion pumps to a pressure of about one billionth of or less of an atmosphere will have no gas at all most of the time. So empty space with one particle in several liters is possible on this planet.

I leave it to the astronomers to tell us what the gas density is far from the nearest star. Close by it may be significant, considering that the Northern or Southern lights are interaction of streams of particles from our sun. At the altitude of the space station there is still a modest amount of our atmosphere. At half that altitude it is enough to be visible on interaction with the shuttle. Pictures of this have been published.

BTW the speed of light is the same in any place. However, the frequency observed (or wavelength) will be altered by an observer moving relative to the source. At least outside the event horizon of the black hole.

ID: 766261 ·
Taurus

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Message 766871 - Posted: 12 Jun 2008, 14:04:59 UTC - in response to Message 766261.

BTW the speed of light is the same in any place.

Light travels at different speeds depending on the medium it travels through.

...but anyway, this is a pretty cool site that has some basic, easy to understand information regarding the speed of light;
http://math.ucr.edu/home/baez/physics/Relativity/SpeedOfLight/FTL.html
ID: 766871 ·
Mr. Majestic
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Message 766954 - Posted: 12 Jun 2008, 16:55:07 UTC - in response to Message 766871.

BTW the speed of light is the same in any place.

Light travels at different speeds depending on the medium it travels through.

...but anyway, this is a pretty cool site that has some basic, easy to understand information regarding the speed of light;
http://math.ucr.edu/home/baez/physics/Relativity/SpeedOfLight/FTL.html

That's a very interesting site. Thanks!

ID: 766954 ·
Danny

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Message 786652 - Posted: 25 Jul 2008, 0:40:47 UTC

Well you know how more fuel would mean more mass which would need more fuel and so on and so on but could it be possible for a ship made like a giant jet nozzle reach the speed of light by flying through space and gathering space gasses and debribs and the funnle them all to a small opening like a jet does. Would that produce thrust?

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Message 786794 - Posted: 25 Jul 2008, 5:31:12 UTC

Anything that has any mass in whatever shape could not get up to the speed of light. The energy would be too much to produce.

This is may be a bit off topic, but if you watch things like star trek, stargate etc etc, you will see that they never travel faster than light withing their own medium.

Ie they create a bubble around them and in traveling quite slow compared to the speed of light.

Or another way to look at it is using gravity to compress space. and then you pass through it. A bit like the folding paper thing to get from one point of the paper to the other.

I'm sure that the speed of light in conventional terms wont be reached.
Islandinfo
ID: 786794 ·
Mr. Majestic
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Message 786969 - Posted: 25 Jul 2008, 18:00:30 UTC - in response to Message 786794.

Anything that has any mass in whatever shape could not get up to the speed of light. The energy would be too much to produce.

Not quite true! If you follow only relativity, then yes, you would be correct, but you forgot about quantum mechanics! I believe that there is a theory in quantum mechanic (it may have even been proven in a particle accelerator) that there are some particles that for a few seconds can indeed go faster than the speed of light. I think it is the uncertainty principle that allows this to happen. And also, if I remember correctly, this happens with the virtual particles form the uncertainty principle.

ID: 786969 ·
Taurus

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Message 787152 - Posted: 26 Jul 2008, 1:34:42 UTC - in response to Message 786969.

And also, if I remember correctly, this happens with the virtual particles form the uncertainty principle.

But the key thing to remember with virtual particles is that they're virtual; they don't really exist.

So far, no particles have ever been observed to surpass the speed of light.
ID: 787152 ·
Mr. Majestic
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Message 787219 - Posted: 26 Jul 2008, 3:58:51 UTC - in response to Message 787152.

And also, if I remember correctly, this happens with the virtual particles form the uncertainty principle.

But the key thing to remember with virtual particles is that they're virtual; they don't really exist.

So far, no particles have ever been observed to surpass the speed of light.

Although you are right about this there are, or at least I think there are, some theorists that think that there is instances exist where your normal run of the mill particle will do the same thing. I meant to include this in my last post :) I could be remembering incorrectly about this theory, but I could have sworn that I read something about it. If only I could find some proof to back me up here.......

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Allie in Vancouver
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Message 787896 - Posted: 27 Jul 2008, 7:48:02 UTC - in response to Message 786652.

Well you know how more fuel would mean more mass which would need more fuel and so on and so on but could it be possible for a ship made like a giant jet nozzle reach the speed of light by flying through space and gathering space gasses and debribs and the funnle them all to a small opening like a jet does. Would that produce thrust?

You are describing a Bussard ramjet Unfortunately, the particles that you scoop up have their own momentum which would rob you of speed. (Inertia strikes again.) Then, as you approach c, the mass increase compounds the problem.

Another wrinkle, every bit as problematic as the energy issue, is time. The faster you go, the longer it takes to go a little faster. It would take, literally, an infinite amount of time to accelerate that last little bit in getting from c * 0.99999... to c * 1.

Pure mathematics is, in its way, the poetry of logical ideas.

Albert Einstein
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Jim Hampton

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Message 789199 - Posted: 28 Jul 2008, 23:21:06 UTC - in response to Message 766068.

What if light were to fall directly into a galactic black hole (from its north pole so to speak), now "quiet" from gobbling up everything within it's influence? Since the black hole would have created a vacuum around it, and it's gravity effects light, could the light be accelerated past 180K/sec before it reached the singularity?

You must bear in mind that space itself is being "warped" and pulled into the black hole. At the point where everything disappears (the horizon), space has been accelerated to C. If you fell into a large black hole (without being killed by radiation or other effects) where you had a bit of time before hitting the singularity and measured the speed of light in your spaceship, you would measure it at "C", from any direction. This would be due to your local space time being pulled into the black hole at the same rate you are. Of course, as you approach the singularity, everything starts being strained by tidal effects. One part of your spaceship is starting to be pulled faster than the other end .... and that would include you!

So the long and short of it is this: Space itself is being pulled into the black hole at the speed of light right at the horizon. You can't see anything from inside the black hole as space inside of the black hole is receeding at a rate faster than light; therefore light cannot escape from inside of the event horizon.

In the same context, it is possible that parts of our universe can never be observed if they (and, of course, space) are receeding from us faster than light. In our local space-time, nothing can exceed the speed of light. Nothing forbids space itself from expanding faster than light (which it does as it is stretched "down" into a black hole. One theory is that it may be possible to exceed the speed of light if you simply cause space itself to expand in the direction you want to go .... simply "ride the surf", I suppose. I would think this would require more than a few double-a alkaline batteries :)

I think .... :))

Best regards from Rochester, NY
Jim

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enzed

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Message 789284 - Posted: 29 Jul 2008, 1:40:08 UTC - in response to Message 765528.

I have often wondered on this topic

If you cant carry enough fuel to throw out the rear end of a rocket to get enough speed to even be close to the speed of light, then mankind wont be visiting the stars without using multigenerational space habitats... and personally I would bet the scheme would fall over as the future kids became more interested in where they originated than the star still in front of them and the unknown big ugly rock they are expected to inhabitat..... so they turn around and go home...

.... If you cant carry enough fuel then you have to make it on the way... this rules out any combustion technology with throwaway propellants, so forget all liquids,gasses,solid materials even nuclear or antimatter as it is still just a throw-it-out-the-rear system.

I think effectively warping the environment around you to suit your purpose, which in this case is propulsion/velocity/vectors.... I am picking gravity research will yield the method of getting us to the stars. Creating asymmetrical shaped gravity gradients that allow the vehicle to "fall" in the direction of travel or be "pushed" "slide" by the warping effect, after all gravity is a deformation of space-time, so when we finally learn to create it ourselves we will have a wonderful tool, but also unfortunately a terrible weapon.

??
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Allie in Vancouver
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Message 789339 - Posted: 29 Jul 2008, 5:20:05 UTC - in response to Message 789284.

I have often wondered on this topic

If you cant carry enough fuel to throw out the rear end of a rocket to get enough speed to even be close to the speed of light, then mankind wont be visiting the stars without using multigenerational space habitats... and personally I would bet the scheme would fall over as the future kids became more interested in where they originated than the star still in front of them and the unknown big ugly rock they are expected to inhabitat..... so they turn around and go home...

.... If you cant carry enough fuel then you have to make it on the way... this rules out any combustion technology with throwaway propellants, so forget all liquids,gasses,solid materials even nuclear or antimatter as it is still just a throw-it-out-the-rear system.

I think effectively warping the environment around you to suit your purpose, which in this case is propulsion/velocity/vectors.... I am picking gravity research will yield the method of getting us to the stars. Creating asymmetrical shaped gravity gradients that allow the vehicle to "fall" in the direction of travel or be "pushed" "slide" by the warping effect, after all gravity is a deformation of space-time, so when we finally learn to create it ourselves we will have a wonderful tool, but also unfortunately a terrible weapon.

??

Maybe. . But the real problem is that we really do not have a good idea of what gravity is. I know that sounds like a flippant remark, but it is not.

We have some beautiful and elegant equations that describe what gravity does. We can predict it with fair degrees of accuracy. We assume (but donÃ¢â‚¬â„¢t know for certain) that it is an essential part of space-time, but that is all we know. I am sorry, but the idea of Ã¢â‚¬ËœwarpingÃ¢â‚¬â„¢ space is all mist in the wind. It seems real and workable, but you should try to remember that all of these concepts (warping, space-time curvature, etc) are just metaphoric images to help the equations make sense to the human mind, they do not represent reality.

It is sort of like, back in school, we learned that the atom was like a little solar system with the sun (protons and neutrons) in the middle and the planets (electrons) whizzing around. Well, we know from assorted quantum theories that, whatever the atom may be, it is certainly not much like a mini solar system. Still, it is a convenient mental image that we hold on to.

Meanwhile, despite your pessimism, the old throw-it-out-the-rear method still has potential. There are no theoretical reasons why atomic mass particles could not be accelerated to near light-speed veolcities and tossed out the back end of our space-ship.Which would, in theory at least, allow a ship to accelerate to near-light speed velocities.

At 99.9+ % light speed as the shipÃ¢â‚¬â„¢s velocity, a voyage that would take decades or even generations of Earth-time would be compressed to months or a few years of ship time.

Pure mathematics is, in its way, the poetry of logical ideas.

Albert Einstein
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Message 789469 - Posted: 29 Jul 2008, 11:44:31 UTC

The speed of light as mentioned above is still too slow for what we want to achieve. Our nearest star apart from the sun would take 4 years. This is just too slow to be going around to explore space.

Using gravity and its effects, and I totally agree with it being just theory, is the more realistic way to go about it.

Without that even if we could get to the speed of light, would deter most if not all adventurers. It just takes too long in terms of human life spans to be venturing out.

Again, even though we know its just theory at the moment, using gravity to compress space seems to be our only realistic hope. Even though its far from reality, no other forms have come up to point us in any other direction.

Islandinfo
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Taurus

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Message 789524 - Posted: 29 Jul 2008, 14:08:53 UTC - in response to Message 789284.

I have often wondered on this topic

If you cant carry enough fuel to throw out the rear end of a rocket to get enough speed to even be close to the speed of light

Enough anti-matter would solve that problem since it would produce more energy with *FAR* less fuel mass...

Using gravity and its effects, and I totally agree with it being just theory, is the more realistic way to go about it.

I'd say it's the less realistic for the foreseeable future since we don't know if we will ever posses the technology to create wormholes or if they would even be traversable (since current theory suggests their interiors might be unstable and collapse before they can crossed).
ID: 789524 ·
enzed

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Message 789712 - Posted: 30 Jul 2008, 2:36:07 UTC - in response to Message 789524.

Hello Taurus
I think even antimatter would still be too "slow" as the forward momentum of the vehicle depends on the velocity of the ejected media, and anti-matter may be very explosive but it is still just matter at explosion speeds... much slower than light speed.

I am quite possibly grasping at straws but there has been a lot of research into electric-field-displacement-drive (edd). It started in many forms way back in the 1920's and continued from there. There is the inevitable controversy about it but this to me also says that there is "something" there in the theory... and why does NASA have a patent for a device that is very very similar to some of the following, if it is all a load of useless-stuff.

Heres a portion of archived stuff. Some of it is one-page (portional document) and you need to either read it or copy it to your local machine, as trying to go to the next page just produces an error.

ttbrown1
ttbrown2
ttbrown3
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ttbrown5
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ttbrown10
ttbrown12
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ttbrown-1960-0
ttbrown-1960-1
ttbrown-1960-2
ttbrown-1960-3
ttbrown-1960-4
ttbrown-1960-5
ttbrown-1960-6
ttbrown-1960-7
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ttbrown-experiment-3
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Message boards : Science (non-SETI) : Speed of Light, and space travel.