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wiggy
2013-Oct-12, 11:00 PM
This has been going through my head for a while now. Not really a question, just a train of thought to spark a discussion.

In water, there is maximum speed things can go through it with out causing cavitation.
In air there is a maximum speed things can go through it without causing a sonic boom.

The way we can make vessels exceed this speed is by making them aqua dynamic and aerodynamic. This reduces the force needed to accelerate through the "sound barrier." It tears the medium up, but the vessel can do it.

So here's a hypothetical. To accelerate an object to the speed of light would take all the energy of the universe. What if we made it optodynamically? i.e., transparent to as many frequencies as possible. Yes an invisible space ship. Hmm, I seem to be describing dark matter.

If dark matter is not getting affected by light, would a space ship made of dark matter be governed by the speed of light?

I look at this issue in the same way as I look at cavitation. If a piece of steel breaks the speed of water, cavitation occurs. We can't break the speed of light because we are made of the same medium that the the light is travelling in. It would be like water breaking the speed of water. It can't happen.

But dark matter to us is like steel to water. It shares some properties that cause an observable affect on our mass. This does not necessarily mean it possesses mass, just that it has an effect on us equivalent to something that possesses mass.

A guess at this stage, the answer would be "nobody knows."

Noclevername
2013-Oct-12, 11:32 PM
Cavitation in a fluid medium just doesn't work even as an analogy, let alone an actual physically useful comparison. Space is not a fluid medium, nor does the speed of light have anything to do with resistance.

Photons are massless, yet they can't exceed the speed of light. Neutrinos are invisible, yet they can't exceed the speed of light.

Paul Wally
2013-Oct-12, 11:38 PM
This has been going through my head for a while now. Not really a question, just a train of thought to spark a discussion.

In water, there is maximum speed things can go through it with out causing cavitation.
In air there is a maximum speed things can go through it without causing a sonic boom.

The way we can make vessels exceed this speed is by making them aqua dynamic and aerodynamic. This reduces the force needed to accelerate through the "sound barrier." It tears the medium up, but the vessel can do it.

So here's a hypothetical. To accelerate an object to the speed of light would take all the energy of the universe. What if we made it optodynamically? i.e., transparent to as many frequencies as possible. Yes an invisible space ship. Hmm, I seem to be describing dark matter.

If dark matter is not getting affected by light, would a space ship made of dark matter be governed by the speed of light?

I look at this issue in the same way as I look at cavitation. If a piece of steel breaks the speed of water, cavitation occurs. We can't break the speed of light because we are made of the same medium that the the light is travelling in. It would be like water breaking the speed of water. It can't happen.

But dark matter to us is like steel to water. It shares some properties that cause an observable affect on our mass. This does not necessarily mean it possesses mass, just that it has an effect on us equivalent to something that possesses mass.

A guess at this stage, the answer would be "nobody knows."

By your logic, the space ship will have to be made "spatio-dynamic" and not "opto-dynamic".

"In water, there is maximum speed things can go through it with out causing cavitation.
In air there is a maximum speed things can go through it without causing a sonic boom."

Therefore by the same logic:
"In space there is a maximum speed things can go through it without causing whatever"

Jens
2013-Oct-12, 11:49 PM
Just coincidentally, a study was recently published on the speed of dark matter. Apparently they found that it doesn't exceed about 54 meters per second. So apparently it has mass and doesn't go all that fast, list like other massive particles.

Shaula
2013-Oct-13, 06:47 AM
The speed of light is a generic limit for massless particles, not just photons. It is called the speed of light just because light was the best understood and most studied example of a massless particle. So yes, your ship would be governed by it whatever it was made out of.

wiggy
2013-Oct-14, 09:41 PM
I need a forum that isn't "Against The Mainstream"
How about "beyond what we know" a forum for pure speculation.

We reach points in a field where we seem to know everything. I'm at a point where we know nothing again. My job is building robots. I use Newtonian physics for that. Its 100% accurate for my profession, but its wrong. Relativity and quantum mechanics are good enough for the greater world that we occupy today. But they're wrong too. They don't account for so much of the matter.

I suspect that in the next few decades we will have the maths to describe more of the dark universe. I purely speculate that there is the dark matter with mass has an average observable effect on light matter which we are seeing as mass travelling at 54m/s. I speculate that we will find it isn't one type of matter. I speculate that as we get better at observing the dark universe we will discover there are massless particle affecting the other particles. Similar to how we detect planets observing their stars. We see dark matter with mass being affected by something that doesn't have mass.

I'd really love to know what people like Shaula imagine. Beyond the current science, what do you speculate? What is your science fiction?

ShinAce
2013-Oct-15, 03:27 AM
Have you ever checked out the list of unresolved problems in physics?
http://en.wikipedia.org/wiki/List_of_unsolved_problems_in_physics

I'm personally more interested in Majorana for neutrinos, but there was a thread talking about Majorana particles as a dark matter candidate.
http://cosmoquest.org/forum/showthread.php?144707-Majorana-Particle-dark-matter

Shaula
2013-Oct-15, 06:23 AM
I'd really love to know what people like Shaula imagine. Beyond the current science, what do you speculate? What is your science fiction?
I believe that whatever comes next in science must approximate the results for current models at low energies/everyday situations. Just like Relativity approximates Newtonian mechanics, QM approximates Classical physics. That is why I say that unless there is good evidence or a valid model to challenge curernt understanding we have to stick to current understanding. It would take some hefty tinkering with what we understand about causal sets to be able to discard the speed of lght as a limit, and with this a rather fundamental rewrite of GR. It may come, it may not.

That actually touches on an area I find the most fascinating in highly speculative physics. I am not so interested in Strings (apart from the beautiful symmetries), Multiverses and all the popular science staples. I'm more interested in the very fundamental stuff - what is spacetime, can we work out how it formed, what is the underlying causal structure it is built on, how does this relate to the universe it is part of, how does information theory relate to this etc.

wiggy
2013-Oct-15, 09:02 PM
That actually touches on an area I find the most fascinating in highly speculative physics. I am not so interested in Strings (apart from the beautiful symmetries), Multiverses and all the popular science staples. I'm more interested in the very fundamental stuff - what is spacetime, can we work out how it formed, what is the underlying causal structure it is built on, how does this relate to the universe it is part of, how does information theory relate to this etc.

I can not challenge current models.

I see a cycle in all fields, not just physics. Someone has an idea (lots of someones and lots of ideas). Someone else makes a crude tool that can measure something that has never been able to be measured before, whether its physics or economics. This new ability to measure a new thing confirms one of a billion ideas. That field grows and gets filled out to the limitations of the ability to measure it. Sometimes new tools with higher resolution are made, sometime not.

The field of physics is not limited by imagination or brainpower, it is limited by material science.

As newtonian physics increased the resolution of newtonian tools, we realised it broke down when the resolution got too high.
Now our tools have enabled us to observe new things like the dark part of the universe. It is highly probable to the point of obvious that physics is going to be re-written again. Relativity will be wrong the same way newton was wrong. Newton wasn't wrong, his models were as accurate as his observations allowed. Einstein was amazing because the models came before the observations to prove them.

I agree with you Shaula. Space time is where we need to look next. You've answered many of my speculative questions about light travelling. I think we need to find a new time, not linked to atomic oscillations. How? No idea. But I think that will be our new tape measure.

Shaula
2013-Oct-16, 06:41 AM
I agree with you Shaula. Space time is where we need to look next. You've answered many of my speculative questions about light travelling. I think we need to find a new time, not linked to atomic oscillations. How? No idea. But I think that will be our new tape measure.
Time is not linked to atomic oscillations. We just define a useful measurement unit by using them, and that is a fairly recent thing. We could use the time of flight of a photon, decay of a particle, it doesn't matter. Just like changing our units of measurement from those based on a King's body parts to the number a bunch of crazy guys with a ruler came up with didn't change the nature of distance.

wiggy
2013-Oct-17, 09:12 PM
Ahhh, again Shaula is sexiest brain in the universe.

Time is not linked to atomic oscillations? Hwah?
My understanding is atomic oscillations are our indication of time speeding up and slowing down. This is how relativity is verified.

If time is not oscillation rate of particles in a particle based visible universe... then what is it.

It sends my mind straight back to my ATM discussion of the mechanism of relativity being that as the energy density of a system increases oscillation decreases.

Noclevername
2013-Oct-17, 10:13 PM
Time is not linked to atomic oscillations? Hwah?
My understanding is atomic oscillations are our indication of time speeding up and slowing down. This is how relativity is verified.

They're just a more accurate clock. If you forget to wind your watch, time does not stop.


If time is not oscillation rate of particles in a particle based visible universe... then what is it.
A property of spacetime. The oscillation is a result of time passing, not a cause.

Shaula
2013-Oct-18, 06:03 AM
Time is not linked to atomic oscillations? Hwah?
My understanding is atomic oscillations are our indication of time speeding up and slowing down. This is how relativity is verified.
That would be redshift. However we also see time dilation for things like overall supernovae light curves (they stretch out) and for decays of relativistic particles (we see muons where we should not, things last longer in particle accelerators than at rest), You could argue that we usually observe them via light but the phenomena we are seeing, the actual things being time dilated, are not based on atomic vibrations. Plus arguing that would lead to the logical problem of this sort of time dilation being a property of stuff here that we use to observe with.

We also verify GR via other methods, unrelated to atomic vibrations. Perihelion precession of Mercury, the deflection of starlight near a massive object.

Time as you are using it is actually duration, which is the component of a path in one particular dimension of spacetime. It is simply the analogue of distance in the 1 dimension of a 3+1 spacetime. We can use all sorts of clocks to measure it, atomic clocks beign the current favourite thanks to their accuracy. But here you are rather confusing the way we measure something with the something. Time is not oscillations of particles, just like space is not linear motion of particles.

DrChinese
2013-Oct-18, 07:45 PM
I'm at a point where we know nothing again. My job is building robots. I use Newtonian physics for that. Its 100% accurate for my profession, but its wrong. Relativity and quantum mechanics are good enough for the greater world that we occupy today. But they're wrong too. They don't account for so much of the matter.


This is a poor way to evaluate theories (right or wrong). Theories have utility, not correctness. Newtonian theory IS useful, as General relativity is USEFUL. You can't even say one is better than the other unless you specify the scope of the issue at hand. Usually, accuracy in a theory is connected to the variables present in the theory. Knowing more variables (and how they inter-relate) allows for a more dynamic model, which can be helpful. Such models often break down when there is missing information.

So it is not like "one size fits all".