Light speed and relativity question

[Aanker]

So, this is a relatively simple question I have regarding relativity and the speed of light, based on a somewhat unrealistic scenario mind you, but I just haven't been able to figure it out:

You are the Captain of the USS Impossible, zipping through interstellar space at 0.999999999999... c (basically, not c, but very close to it). While observing the interesting view from the ship's bridge, one of the lieutenants calls you over to look at a funny meme image he found in his social media feed. The lieutenant sits at his hyper futuristic computer screen, approximately ten steps in front of you. This also happens to be the very exact direction of the ship's movement.

Now, the question is, how easy is it for you to just walk over there? It seems natural to me to assume that because the crew - by being on the ship - is already coasting through space near the speed of light... even a small increase in velocity (such as taking a small step) would require near infinite amounts of energy/effort. Even when accounting for momentum (you move forward, the ships moves backward) it seems strange.

The second alternative I can imagine is that relativity somehow makes it seem to the captain as if he is strolling around effortlessly at very sub-light speed on a stationary ship in essentially a flat universe because (if I recall correctly) light in vacuum always travels at c regardless of the velocity of the observer.

Either way, I am confus, pls halp

[XIRA]

You should be able to walk just fine. Time runs faster, but that's about it.

[benzman]

Everything in the ship would be quite normal to the crew. The ship would be traveling close to c RELATIVE TO some hypothetical observer. However, to the crew the ship appears to be stationary and the observer would appear to be travelling at close to c. Einstein's theory states that the speed of light is constant relative to the observer's frame of reference. For the observer, his frame of reference is wherever he happens to be. For the crew, their frame of reference is the ship they are in. Anyhow, that is how this only moderately well informed layman understands it. If I am wrong then I am sure that one of our more educated contributors will correct me.

[Darnok]

Relativity is just concept with few assumptions nothing more, it is just hypothesis written on paper without proof and I doubt it universe work that way.

Just imagine you are on that ship and you fire bullet to some stationary target, bullet moves faster than light from target perspective

There can't be speed limit in universe because speed is our (human) construct it doesn't exist for real.

[Lukaszenko]

There's plenty of evidence for relativity, and crucially, none against it. No offense Darnok but you clearly don't understand it enough to dismiss it.

Anyway, as everyone has said, the speed of light is CONSTANT for everyone, and there is no fixed frame of reference. You can only say that something goes this or that fast relative to something else.

What this means is that you don't need to use the USS Impossible as a though experiment, because WE are already in such an experiment. There the already objects in the universe relative to which WE are moving at 0.9999999999c, and yet we don't need infinite energy to get up and go to the bathroom. The point is that when you do get up and go to the bathroom, or even send a spaceship to Pluto, you or the spaceship will not exceed the speed of light. The best you can do is add more digits to the 0.9999999999c, and warp time and space as needed to ensure that c is never reached.

Sounds crazy, but there are actual engineering examples where they had to take this effect into account.

Edited June 3, 2015 by Lukaszenko

[SargeRho]

You could walk there just fine, since you don't notice the effect on yourself, only on your surroundings. Relative to your point of origin you may be moving close to C, but relative to the ship you're not.

-----------

Relativity is just concept with few assumptions nothing more, it is just hypothesis written on paper without proof and I doubt it universe work that way.

Relativity is probably the single most well established thing in science after Thermodynamics. The effects of it are measurable on Earth, GPS satellites' internal clocks need to be adjusted because time passes at a different rate up there than down here, due to gravity, ergo, relativity. It's been repeatedly demonstrated through all sorts of experiments. Speed is not just a human construct, it's a real thing, with real effects, unless you're arguing that the velocity at which a bullet splatters someone's brains across the road is imaginary?

Then there's these:

http://upload.wikimedia.org/wikipedia/commons/1/11/A_Horseshoe_Einstein_Ring_from_Hubble.JPG

That's an "Einstein ring", an instance of gravitational lensing - as predicted by relativity - so extreme, it bends the light of an object in the background into a ring.

Edited June 3, 2015 by Red Iron Crown

[K^2]

Relativity is probably the single most well established thing in science after Thermodynamics.

Nah. It surpassed that by miles near the end of 50s, when people realized that General Relativity and Quantum Field Theory are two sides of the same coin. And since both QFT and GR have been tested to more than 12 decimal places, there is not a single theory that can boast being even remotely as close to being certainty.

[Unheld]

Well, there is a speed limit, the speed of light in a vacuum and its not a human construct, it directly results from the very nature of electromagnetic waves.

It is NOT a theory, the Michelson-Morley-Experiment about 15 years prior to Einsteins descriptions revealed that the speed of light is the same if measured prograde or retrograde towards earths own movement around the sun. (this maybe be written a bit confusing, what I mean is, that they expected the velocity of earth to add or subtract to/from the speed of light when measured in the according direction. Just like the velocity of a man walking in a moving train is added to the speed of the train. However, this was not the case)

Through Maxwells equations for electric and magnetic fields Einstein realized that lightspeed must be independent from the movement of an observer. This results in a lot of hard to imagine concepts, like the relativity of time.

One of those results concerning the problem stated above is that velocities don't add up like we expect. For the man in the train example, we say that the total velocity of this man for an outside observer is his velocity added to the trains velocity:

v(total) = v(man) + v(train)

But in reality, as a result of the absolutism of the speed of light, the equation actually reads:

v(total) = ( v(man) + v(train) )/( 1+ v(man)*v(train)/c^2 )

For velocities used in every day life, this equation becomes the normal adding up of velocities because the involved speeds are very slow compared to c, which means we can neglect the denominator.

But lets say, that the train moves with 0.9c and the man moves relative to the train with 0.5c, that means the man perceives (measures) his movement inside the train with 0.5c.

Now what do we measure as for the velocity of that man?

Using the equation above:

v(total) = ( 0.5c +0.9c ) / (1 + 0.5c*0.9c / c^2 ) = 1.4c / ( 1+ 0.45c^2/c^2 ) = 1.4c / 1.45 = 0.9655 c

So, we measure 0.9655 c as his velocity. (For a clearer understanding, remember that the time inside the train flows slower for us outside observers. So while the man thinks he moves about 150 000 km per second, we perceive "his" second (what he calls a second) to be much slower, which means in our frame of reference when he thinks one second has passed, our stopwatches state that much more than one second has passed ( indeed our stopwatches should say 2.3 seconds have passed))

I hope this helps.

[Darnok]

You could walk there just fine, since you don't notice the effect on yourself, only on your surroundings. Relative to your point of origin you may be moving close to C, but relative to the ship you're not.

So if you very close to speed of light and you breathe out CO2 does that gas is going faster than light or not? It is no longer moving with speed of ship

Relativity is probably the single most well established thing in science after Thermodynamics. The effects of it are measurable on Earth, GPS satellites' internal clocks need to be adjusted because time passes at a different rate up there than down here, due to gravity, ergo, relativity. It's been repeatedly demonstrated through all sorts of experiments. Speed is not just a human construct, it's a real thing, with real effects, unless you're arguing that the velocity at which a bullet splatters someone's brains across the road is imaginary?

Then there's these:

http://upload.wikimedia.org/wikipedia/commons/1/11/A_Horseshoe_Einstein_Ring_from_Hubble.JPG

That's an "Einstein ring", an instance of gravitational lensing - as predicted by relativity - so extreme, it bends the light of an object in the background into a ring.

What? Relativity is fundamentally broken, because it assumes limits and it is based on time and gravity, while we didn't found sources of any of them.

Show me source of time or source of gravity

As for satellites if you are using fundamentally broken equations to calculate satellites movement and orbits no wonder you have to make adjustments

Bullet can hurt your body because you used large portion of energy to move it.

While you can always use more energy to move some object a bit further why would there be speed limit?

Speed is handy in some calculations like how fast you can go from home to work, but it is not real it is all about energy you put into object to move it.

EDIT:

Well, there is a speed limit, the speed of light in a vacuum and its not a human construct, it directly results from the very nature of electromagnetic waves.

I hope this helps.

Speed of light isn't even constant http://www.hw.ac.uk/news/scientists-slow-down-speed-light-travelling-20509.htm

if you can slow it down, you can also put more energy on it and make it faster.

How do you know we are not measuring slowed down photons? Maybe our galaxy is surrounded by some kind of field that slows down light.

Edited June 3, 2015 by Red Iron Crown

[Rune]

Well, there is a speed limit, the speed of light in a vacuum and its not a human construct, it directly results from the very nature of electromagnetic waves.

It is NOT a theory, the Michelson-Morley-Experiment about 15 years prior to Einsteins descriptions revealed that the speed of light is the same if measured prograde or retrograde towards earths own movement around the sun. (this maybe be written a bit confusing, what I mean is, that they expected the velocity of earth to add or subtract to/from the speed of light when measured in the according direction. Just like the velocity of a man walking in a moving train is added to the speed of the train. However, this was not the case)

Through Maxwells equations for electric and magnetic fields Einstein realized that lightspeed must be independent from the movement of an observer. This results in a lot of hard to imagine concepts, like the relativity of time.

One of those results concerning the problem stated above is that velocities don't add up like we expect. For the man in the train example, we say that the total velocity of this man for an outside observer is his velocity added to the trains velocity:

v(total) = v(man) + v(train)

But in reality, as a result of the absolutism of the speed of light, the equation actually reads:

v(total) = ( v(man) + v(train) )/( 1+ v(man)*v(train)/c^2 )

For velocities used in every day life, this equation becomes the normal adding up of velocities because the involved speeds are very slow compared to c, which means we can neglect the denominator.

But lets say, that the train moves with 0.9c and the man moves relative to the train with 0.5c, that means the man perceives (measures) his movement inside the train with 0.5c.

Now what do we measure as for the velocity of that man?

Using the equation above:

v(total) = ( 0.5c +0.9c ) / (1 + 0.5c*0.9c / c^2 ) = 1.4c / ( 1+ 0.45c^2/c^2 ) = 1.4c / 1.45 = 0.9655 c

So, we measure 0.9655 c as his velocity. (For a clearer understanding, remember that the time inside the train flows slower for us outside observers. So while the man thinks he moves about 150 000 km per second, we perceive "his" second (what he calls a second) to be much slower, which means in our frame of reference when he thinks one second has passed, our stopwatches state that much more than one second has passed ( indeed our stopwatches should say 2.3 seconds have passed))

I hope this helps.

That explanation is, albeit a bit daunting to jump into (you write equations and people jump away from those), a very clear one of the paradox that usually gets most people, that "shooting a bullet forward when I'm at 0.99c".

Just like you say, it's the time dilation making that bullet seem MUCH slower, when seen from the outside. Velocity is distance divided by time, and even though inside the ship the bullet's second seem to tick by as normal, form the outside each of those "seconds" where the bullet goes across several hundred meters, are perceived as more time, depending on the dilation factor, with no upwards limit. If "the ship it's fired form" was going very, very close to the speed of light when it fires, the bullet would need external years to cover the distance it makes in one of "its" (or the ship's) seconds.

Rune. I must remember it for late-night drunken relativity discussions with non-physics people.

[Unheld]

Show me source of time or source of gravity

I don't even understand what you mean by "source of time" or "source of gravity"?

Does the Higgs Boson as a source of mass suffice?

Anyway can you show me a source for magnetic fields? Or are they also human constructs?

How about a source of length or width?

Speed of light isn't even constant http://www.hw.ac.uk/news/scientists-...ling-20509.htm

if you can slow it down, you can also put more energy on it and make it faster.

How do you know we are not measuring slowed down photons? Maybe our galaxy is surrounded by some kind of field that slows down light.

The Speed of light IN A VACUUM is constant and it is the limit!

And you should at least READ the articles you quote first:

Professor Faccio said, “The speed of light is a universal constant and plays a central role in our understanding of the Universe and Einstein's theory of relativity. The exciting discovery here is that this speed is the true speed of light only for plane waves, that is waves that are perfectly flat. In everyday situations however, we interact with light that is not a plane wave but has some kind of structure on it.

To recap: the speed of light in a vacuum is constant and it is the limit!

But in a medium such as air, water, or glass it is slower. And in fact it is possible for things to be faster than light in a medium.

For example the blueish glow in a freshly opened nuclear reactor ( known as Cherenkov-radiation ) is the result of electrons moving faster in the water than light in the water.

How do you know we are not measuring slowed down photons? Maybe our galaxy is surrounded by some kind of field that slows down light.

Because I read Terry Pratchetts Discworld books as phantasy novels and not as the annals of science...

Edit:

@Rune: thank you

Edited June 3, 2015 by Unheld

[SargeRho]

So if you very close to speed of light and you breathe out CO2 does that gas is going faster than light or not? It is no longer moving with speed of ship

The CO2 moves slower than light, obviously. The effect is not noticeable by the observer himself, only in relation to the environment. If you move near the speed of light, and shine a flashlight forward, that light moves at the speed of light. It would not be harder to move, although relativistic effects might be noticeable by those around you, I'm not fully sure myself, I'm not a physicist.

What? Relativity is fundamentally broken, because it assumes limits and it is based on time and gravity, while we didn't found sources of any of them.

Show me source of time or source of gravity

Mass is the source of gravity. Mass bends spacetime, and that bend is gravity.

As for satellites if you are using fundamentally broken equations to calculate satellites movement and orbits no wonder you have to make adjustments

It has nothing to do with the satellites movement, the relativistic effect of two dozen times the speed of sound is negligible. It's produced by the Sat's distance from Earth, and thus less gravity.

Bullet can hurt your body because you used large portion of energy to move it.

While you can always use more energy to move some object a bit further why would there be speed limit?

The bullet can hurt because of it's velocity relative to you. If you are moving at the same speed as a bullet, it can't hurt you - the wind would strip your flesh off your bones at that speed, but that's beside the point. If you're stationary and something hits you at mach 2, it's going to hurt you, because of the difference in velocity, and resulting release of kinetic energy on impact.

Speed is handy in some calculations like how fast you can go from home to work, but it is not real it is all about energy you put into object to move it.

Of course it's real. Yes, it's about the energy you put into an object to move it, or more accurately, to alter its momentum. You're arguing against well established physics.

Speed of light isn't even constant http://www.hw.ac.uk/news/scientists-slow-down-speed-light-travelling-20509.htm

if you can slow it down, you can also put more energy on it and make it faster.

How do you know we are not measuring slowed down photons? Maybe our galaxy is surrounded by some kind of field that slows down light.

The speed of light in a vacuum is constant. It's different within various different environments, which is why light is deflected when it crosses from air into water for example.

As for slowed down photons: That's not how photons work, and it doesn't consistently account for the observations.

[K^2]

Mass is the source of gravity. Mass bends spacetime, and that bend is gravity.

Streess-energy, actually. Light bends space-time just fine despite having no mass.

[Unheld]

Over the centuries, there have been numerous attempts to overturn conservation laws, but they failed to gain momentum.

Very funny! And somewhat fitting here...

[Darnok]

I don't even understand what you mean by "source of time" or "source of gravity"?

Does the Higgs Boson as a source of mass suffice?

Anyway can you show me a source for magnetic fields? Or are they also human constructs?

How about a source of length or width?

Mass is human construct, we can measure force between two objects, but we can't say are they pulling each other or are they pushed towards each other.

Electron generate magnetic fields on movement, but to move them you need energy, so in some way magnetic field is derivative of movement and energy.

So what is source of time? You need it to calculate speed

Just look at atoms or any other particles, they have size, that is very real. They have energy that is also real.

Particles or larger bodies like planets also were moved by some energy (doesn't matter if it was impact energy from other particles/bodies or influence of magnetic field) after that they are changing their location inside of universe and that's it.

But speed is construct because it calculates travel distance and time, while universe doesn't really needs to hold such values and particles and planets may move inside it.

The Speed of light IN A VACUUM is constant and it is the limit!

And you should at least READ the articles you quote first:

To recap: the speed of light in a vacuum is constant and it is the limit!

You should read what I said "IN OUR GALAXY", we have no idea how "fast" light may travel in intergalactic space.

You people have mind set of medieval person that still thinks Sun is orbiting Earth :/ just because they measure Suns movement on the sky each day it is true!!!

But in a medium such as air, water, or glass it is slower. And in fact it is possible for things to be faster than light in a medium.

For example the blueish glow in a freshly opened nuclear reactor ( known as Cherenkov-radiation ) is the result of electrons moving faster in the water than light in the water.

You didn't read that article

"The work demonstrates that, after passing the light beam through a mask, photons move more slowly through space. Crucially, this is very different to the slowing effect of passing light through a medium such as glass or water, where the light is only slowed during the time it is passing through the material – it returns to the speed of light after it comes out the other side. The effect of passing the light through the mask is to limit the top speed at which the photons can travel."

Light speed is not longer constant! And speed itself is not part of universe it is just simplification for our calculations.

It has nothing to do with the satellites movement, the relativistic effect of two dozen times the speed of sound is negligible. It's produced by the Sat's distance from Earth, and thus less gravity.

Wrong, it has everything to do with satellites movement, you just using wrong equations, so they needs to be corrected to move at same "time" seen from Earth.

The bullet can hurt because of it's velocity relative to you. If you are moving at the same speed as a bullet, it can't hurt you - the wind would strip your flesh off your bones at that speed, but that's beside the point. If you're stationary and something hits you at mach 2, it's going to hurt you, because of the difference in velocity, and resulting release of kinetic energy on impact.

Bullet or even small particles can hurt you because of energy released from impact with your body.

If you would build robot arm that would push bullet through your body, very slowly, it would do it and this robot arm would use same amount of energy you needed to move bullet plus energy released from impact.

Of course type of damage of your body would be different (impact and energy release vs slow pushing).

Edited June 3, 2015 by Darnok

[Guest Brody_Peffley]

The reason why we have the speed of light is because everything that has no mass goes at or near the speed of light in a vacuum. Of course the speed of light will hit spots of particles and decelerate but they will accelerate again to its normal speed. To see if the speed of light is true you can look at the particle accelerators which reaches a point where the particle can not go any faster. You can never surpass the speed of light or the speed barrier because by then the amount of energy to push something with no mass(No mass that is, zero!) is infinite. Photons can be halted by having objects in the way, like the suns light takes hundreds to a couple thousand years just to come out because the light is slowed down from the dense plamsa. Lets just put it this way, the speed of light is the barrier, but you can have light slower then the speed of light. That still doesn't mean that the speed of light is false, it just simply means that the speed of light is how fast light can go when not blocked by something.

[Unheld]

I'm not sure anymore if you are for real or just trying to troll us. I'm sorry if that sounds offensive, but I feel a little like being made fun of...

May I ask how old you are, or what your scientific background / education is?

I really don't mean offence but sentences like quoted below really let me doubt if a response is worth the time.

Just look at atoms or any other particles, they have size, that is very real. They have energy that is also real.

You people have mind set of medieval person that still thinks Sun is orbiting Earth :/ just because they measure Suns movement on the sky each day it is true!!!

You know that energy is the construct in all of that? You are absolutely free to set your energy values like you want to. Everybody who had physics 101 on an university level knows that.

Also, with "atoms or any other particles" having size, you enter into a lot of trouble and wibbly-wobbly problems because of unexact definitions and descriptions.

On atomic levels there is no clear distinction between particles and waves. That becomes even more profound when you consider that electrons have mass but no volume. They don't have size!

It is only possible to "measure" the radius of atoms and/or their nucleus because of the forces present. There is no clear boundary or edge between an atoms nucleus and well... not nucleus.

were moved by some energy --- they are changing their location inside of universe

Right, that's velocity, or speed. A change in position during a certain amount of time.

That's were I feel like being trolled...

travel distance and time, while universe doesn't really needs to hold such values and particles and planets may move inside it.

may move inside it?? So they are travelling? travelling maybe a distance? in a certain amount of time?

And which values are not "needed to be hold" then?

Edited June 3, 2015 by Unheld

[Dodgey]

Ok can we please not have this thread turn into a flame that this subfourm is practically known for?

In anycase I too am curious (although it has no effect on the strength or lack thereof of your argument) as to what your educational background is. Have you gone to university to study science or as I am mainly googlcated (how's that for a term we all need).

The reason why going faster than the speed of light is considered impossible is due to time dilation. Time dilation is the affect of time slowing down due to either being in a gravetational field, such as the earth, or by traveling at a velocity relative to something else. So as you travel faster or deeper into a gravity well time appears to slow down for you, or another way of putting it is that the rest of the universe appears to speed up. So lets say that you are traveling along at 100m/s below the speed of light to an outside observer. Due to this immense speed time dilation makes it so that every second that passes for you a year passes for the outside observer (made up numbers, I think the discrepency would be larger but I'm no expert). Let's say that when you startred your journey your acceleration was 1m/s/s, now if you started thrusting with the same acceleration while traveling at 100m/s below the speed of light to you it would only take one second of thrusting to achieve 99m/s below the speed of light, however to the outside observer you have been thrusting for one year not one second. And as you travel faster the effects of time dilation become pronounced, so one second for you becomes two years for the observer. And we know that time dilation is a thing due to experiments done with identical clocks, one on the ground with another in an aircraft, the experiment showed that the one in the aircraft did run slower due to time dilation.

[YNM]

Mass is human construct, we can measure force between two objects, but we can't say are they pulling each other or are they pushed towards each other.

Mass is a quantity that represent how hard an object affect another object. Not a human construct, we just put some numbers on the scale...

Electron generate magnetic fields on movement, but to move them you need energy, so in some way magnetic field is derivative of movement and energy.

You must read somewhere first, that electrons are non-baryonic. Their intenal energy already causes them to move by itself, and their location are non-specific.

So what is source of time? You need it to calculate speed

Time is the difference between two instances at the same spatial location. Look up spacetime. Much the same as mass, we just put some numbers on the scale. (and why CIPM froze light velocity as a certain arbitrary number that's close to the latest measurements, only setting a standard for time)

Just look at atoms or any other particles, they have size, that is very real. They have energy that is also real.

Particles or larger bodies like planets also were moved by some energy (doesn't matter if it was impact energy from other particles/bodies or influence of magnetic field) after that they are changing their location inside of universe and that's it.

But speed is construct because it calculates travel distance and time, while universe doesn't really needs to hold such values and particles and planets may move inside it.

The problem is... that's how we got them doing. They're observed to be constant, no matter who give the signal.

You should read what I said "IN OUR GALAXY", we have no idea how "fast" light may travel in intergalactic space.

You people have mind set of medieval person that still thinks Sun is orbiting Earth :/ just because they measure Suns movement on the sky each day it is true!!!

I bet you don't know as well... And when you don't know anything, thinking will stop, and knowledges go stagnant. The reason why there exist heliocentrism (in historical terms - note that now heliocentrism is wrong as well) because people assumed that planets go round the Sun much like moon go round Jupiter. And it's convenient. And it's proved to be very true far later.

You didn't read that article

"The work demonstrates that, after passing the light beam through a mask, photons move more slowly through space. Crucially, this is very different to the slowing effect of passing light through a medium such as glass or water, where the light is only slowed during the time it is passing through the material – it returns to the speed of light after it comes out the other side. The effect of passing the light through the mask is to limit the top speed at which the photons can travel."

Light speed is not longer constant! And speed itself is not part of universe it is just simplification for our calculations.

I'm thinking that there must be something in that "space". Air does reduce speed of light, and I wish we're not talking about group velocity, which have been discussed to death previously.

--------

For the (special) relativistic part, here are some views that helps you understand why it goes that way :

1. Speed of light in vacuum is constant, whichever universe you live, whichever galaxy you live. Whatever speed you want to be.

2. Informations are converyed only and only by light. Nothing else, all particles are slower.

3. When you're moving wrt somebody, you measure it's position by the light it sends you... voila ! Now, you need corrections...

For general relativity, it adds the fact that measured distance might differ from positional distance (or coordinate distance). Nevertheless, anything that have speed less than infinite needs time to travel any distance... and you get the problem.

Edited June 3, 2015 by YNM

[Darnok]

I'm not sure anymore if you are for real or just trying to troll us. I'm sorry if that sounds offensive, but I feel a little like being made fun of...

May I ask how old you are, or what your scientific background / education is?

I really don't mean offence but sentences like quoted below really let me doubt if a response is worth the time.

You know that energy is the construct in all of that? You are absolutely free to set your energy values like you want to. Everybody who had physics 101 on an university level knows that.

Also, with "atoms or any other particles" having size, you enter into a lot of trouble and wibbly-wobbly problems because of unexact definitions and descriptions.

On atomic levels there is no clear distinction between particles and waves. That becomes even more profound when you consider that electrons have mass but no volume. They don't have size!

It is only possible to "measure" the radius of atoms and/or their nucleus because of the forces present. There is no clear boundary or edge between an atoms nucleus and well... not nucleus.

What tools we have to measure particle sizes?

Imagine your only tool to measure size of objects and particles is ping-pong ball, if you measure size of car or human it can give you more or less accurate results.

But if you would want to measure size of ping-pong ball using ping-pong balls you would see wave

Not to mention what results you would get trying to measure size of ball 5 or 10 times smaller than ping-pong ball using bouncing ping-pong balls.

Electrons and other super small particles does have size and volume, we just don't have tools to measure them.

Space itself can be filled with some neutral particles call it as you like dark matter, dark energy or Aether (I prefer last one ) but space is not void.

Those particles can interact with other larger particles like photons and create waves behind it. Aether can even have pressure and push atoms towards each other, basically this is how EM drive works it uses Aether (the space pressure) to push itself away from "nothing".

There is no need for mass (and gravity) all we need is space pressure that can push objects to each other, it can even push electrons towards protons.

Right, that's velocity, or speed. A change in position during a certain amount of time.

That's were I feel like being trolled...

Change in position is vector - magnitude (energy used to make a push) and direction.

Certain amount of time, what time? Seconds, days? Those units are not real, they were created by us humans to make some calculations simpler.

Universe doesn't need time to work, objects doesn't need time to move, you need time to calculate speed because you learned thinking that way in school.

may move inside it?? So they are travelling? travelling maybe a distance? in a certain amount of time?

And which values are not "needed to be hold" then?

Travelling, movement is real, but distance not, distance is your construct created to measure something.

EDIT:

I bet you don't know as well... And when you don't know anything, thinking will stop, and knowledges go stagnant.

You are right I don't know and I am not assuming it is same, but you are

And that is mistake, because you are creating hypothesis and using this hypothesis as FACT and you forgot it was created using assumption.

Mass is a quantity that represent how hard an object affect another object. Not a human construct, we just put some numbers on the scale...

What you call mass is just force between two objects, but you can't say does those objects are pulling each other or they are pushed, by pressure of space (dark matter/dark energy etc etc call it as you like)

Matter can be massless, so "speed" faster than light may be possible.

Edited June 3, 2015 by Darnok

[LN400]

First a word on aether. The idea of something called "aether" vanished as a scientific concept as soon as they discovered there was no need for it. It's an idea that has been buried for more than 100 years. Space pressure, as it's called in this thread, is not mentioned in physics as far as I'm aware.

Second, sub atomic particles do not necessarily need to have a volume in a classical sense. Some branches of modern physics regard these particles as waves, wave functions, oscillations, not as tiny, tiny ping pong balls.

[Unheld]

@YNM:

I wish we're not talking about group velocity, which have been discussed to death previously.

Yes, yes we are....

@Darnok

Electrons and other super small particles does have size and volume

No they don't! It doesn't have anything to do with our methods of measurements. It has something to do with quantum mechanics, mostly them being Fermions...

all we need is space pressure

Well, as it turns out there are three types of "space pressures", called the fundamental forces ( gravity being one of them ).

And yes, maybe these are just different sides of the same coin, that's why people are working on unifying them to ONE "space pressure".

Change in position is vector - magnitude (energy used to make a push) and direction.

right, a vector between the different locations relative to a coordinate or reference system. Energy, again, is actually a human construct and not something inherent to the universe.

what time? Seconds, days? Those units are not real

Why aren't they real?

Lets step back from movement, what about change in entropic systems? what about oscillations of atomic energies? What about the time the nitrogen atom needs to tunnel through the energy wall created by the hydrogen atoms in an ammoniac molecule?

Travelling, movement is real, but distance not, distance is your construct created to measure something.

If distance is not real, and time is not real, then please explain to me what movement is!

If nothing else, please explain to me: what is movement, or travelling?

[Darnok]

First a word on aether. The idea of something called "aether" vanished as a scientific concept as soon as they discovered there was no need for it. It's an idea that has been buried for more than 100 years. Space pressure, as it's called in this thread, is not mentioned in physics as far as I'm aware.

Second, sub atomic particles do not necessarily need to have a volume in a classical sense. Some branches of modern physics regard these particles as waves, wave functions, oscillations, not as tiny, tiny ping pong balls.

But there is need for dark matter and dark energy?

Concept of Aether was closer to reality than Einstein relativity concept with some artificial limits and lots of assumptions.

Aether was rejected using Ockham's razor not because it was wrong concept.

[YNM]

You are right I don't know and I am not assuming it is same, but you are

And that is mistake, because you are creating hypothesis and using this hypothesis as FACT and you forgot it was created using assumption.

Read my saying on heliocentrism. Almost everything complicated and unobscure starts from hypothesis, and proved by experiments. And as far as this, the conclusion of almost all experiment is that light speed are constant. (bar this, though they're very small to make a difference on how you feel the day; even so, everything are hypotheses as you stated.)

What you call mass is just force between two objects, but you can't say does those objects are pulling each other or they are pushed, by pressure of space (dark matter/dark energy etc etc call it as you like)

Pressure means surface area - that should make "equal mass" of paper falls faster than lead at any scenario in a small space. It'd also cause Earth to comes to you, not you comes to Earth (and what about if everyone jumps ? Would we fall slower, or least are some is going to fall slower ?). I'm intrigued to ask you to draw a scenario where this happens - you don't imagine something you can't make image of.

Matter can be massless, so "speed" faster than light may be possible.

We don't observe them. Unless you're referencing to bosons, which are force carrier and not matter at all.

Edited June 3, 2015 by YNM

[BlueCosmology]

But there is need for dark matter and dark energy?

Concept of Aether was closer to reality than Einstein relativity concept with some artificial limits and lots of assumptions.

Aether was rejected using Ockham's razor not because it was wrong concept.

Seriously? Lol. The aether is much more of a simple explanation as to why the theory of electromagnetism predicts one particular speed for electromagnetic waves. If it was just Ockham's razor Einsteinian relativity would be rejected and the aether accepted, in fact this is one of the reasons Einsteinian relativity took a while to become accepted.

You think the fact that light travels the same speed relative to everyone because space and time are not absolute but change depending on motion as well as gravitation being a geometrical property of spacetime rather than a force which is described by a non linear coupled tensor partial differential equation with 256 components (that luckily can be reduced down to 10 independent components) is simpler than "Electromagnetism predicts one speed for light because it travels at one speed through a medium."

Really?

Aether was rejected because an incredible amount of evidence was found against it, and an incredibly amount of evidence was found for relativity. General relativity is famed for being incredibly non-simple, not the other way around. Hell the kepler problem hasn't even be proved in closed form in general relativity yet.

Edited June 3, 2015 by BlueCosmology