Why can't matter reach the speed of light?

[filterxg]

http://www.nasa.gov/centers/glenn/research/warp/warp.html

I think that site may give you the answers you are looking for (except the black hole stuff).

 

[imported_DocHolliday]

I remember something about photons being like waves and particles?

 

[silverpig]

Originally posted by: DocHolliday
I remember something about photons being like waves and particles?

The real truth is there are no such things as particles. A baseball may act like a particle and not a wave, but it does have some undetectable wave-like properties. As the energy of the object decreases its particle like characteristics disappear.

Low energy photons travel and behave very much like waves. High energy electrons behave very much like point particles, however if you look at photons and electrons at the same energy scales they start to look fairly similar when talking about waves and/or particles.

 

[Squally Leonharty]

A documentary on Discovery Channel mentioned something about a large device with a huge sail that is used for accelerating the device by means of light. In other words, it uses the sun's light, or rather photons, to accelerate the device. They're planning on letting it go until "the end of the space". Now, if the photons, that travel at the speed of light, accelerate the device, wouldn't the device itself also be able to travel at the speed of light?

See it like this: blow wind on a simple self-built car with a big sail and the car will begin travelling slowly, but as time passes, it'll travel at the same speed as that of the wind itself. Theoretically, that is. Friction is what makes it slow down, but in space there's no friction. So if the device in the space keeps getting accelerated continually by the photons, it would be possible for it to travel at the speed of light, because the photons themselves already travel at the speed of light.

I think the problem lies in the fact that our sources to make something move cannot be used up infinitely fast and infinitely long, like fuel in a car: it'll be empty at one point (you'll need to refuel) and that matter (fuel) cannot burn any faster than it can allow (there's a certain limit in how fast you can burn fuel in a car, which explains why it's impossible to tune up your car with infinitely high RPM and stuff, not to mention friction plays a role in this). However, the sun (and all other stars that'll also contribute to accelerating the device once it gets past them) still live for many billions of years and that should be more than enough to achieve a high speed like that.

Just some crazy stuff from my tired mind. 12:14 AM now and I need to go to bed, so excuse me if I said something stupid. xD I'm also not entirely familiar with Einstein's relativity theory and travelling at the speed of light. I do know that there's a formula like this:

m = m0 / Sqrt[1 - v/c]

m0 = initial mass
m = mass at velocity v
c = speed of light

which implies that if v = c, m becomes infinitely large. But that applies if you move that mass by means of something ordinary, like fuel or electricity. Would this still apply if photons were the only things that accelerate the device in the space? Because, y'see, nothing from our equipment can travel at the speed of light, only photons can. Wouldn't that make a difference? *shrugs*

Enough babbling from me. You can prove me wrong; I'm quite interested in this. xD *dies* I'm off to bed now. =P

 

[Keill]

Originally posted by: Fox5
Just wondering, if something was in a vacuum, why couldn't it accelerate forever until it reached the speed of light? What forces would counter the acceleration?

The main 'force' that would counter the acceleration, would in fact be the the mass of the object being accelerated to begin with.

All objects with mass, need a minimum amount of energy to be transferred to them in order to make them move - (it's one of the ways in we define mass to begin with (along with Relative Atomic Mass)). However - HOW the energy is transferred to an object can make a difference.

A 100% efficient propulsion system would be able to affect the whole of an object, transferring energy to it in a way that would be highly (well, TOTALLY), consistent in both dierection and rate of transfer.

If the direction and rate of transfer isn't that consistent - then you wind up with parts of the object being affected in different ways, and having energy transferred to them too slowly (compared to the rest of the object) to obtain the required speed. the difference in energy content will increase exponentially with velocity, making c impossible to reach.

Since a 100% propulsion system is probably whats required to get round this problem, (or at least 99.9 to quite a lot of decimal places), and we don't have or know of any - the speed of light is currently impossible for us to reach. (The particle accelerators are close - but no cigar....).

The only force I can think of which might, possibly, be able to do this, is gravity - but since we still don't really know enough about gravity yet, it's still up-in-the-air, so to speak.

 

[DrPizza]

I felt this was worth quoting in this thread. Cquark briefly mentioned it above.

Originally posted by: cquark

Originally posted by: CycloWizard

Originally posted by: TuxDave
You forgot to include that if the proton was indeed moving at the speed of light, its mass would have been infinite.

I was going to post this a couple days ago but forgot. Since electrons are almost always moving near or at the speed of light (IIRC), why is their mass finite/infinitesimal?

Mass doesn't increase with velocity.

Mass is the magnitude of the energy-momentum four-vector and as such isn't altered by frame changes. The so-called relativistic mass, which was invented to make popular explanations of special relativity simpler though less accurate, is actually the time component of that four-vector. It is frame dependent, but it cannot be used in place of mass in most equations. Perhaps Einstein said it best:

"It is not good to introduce the concept of the mass M = m/(1-v2/c2)^1/2 of a body for which no clear definition can be given. It is better to introduce no other mass than `the rest mass' m. Instead of introducing M, it is better to mention the expression for the momentum and energy of a body in motion."

We can calculate the energy of a near light-speed proton as follows though

E = m c^2 ( 1/sqrt(1 - v^2/c^2) - 1 )

If v = 0.999999c, then the factor is parentheses is about 100, indicating the proton has a kinetic energy 100X that of its rest mass energy or only 1.6726 x 10^(-24)g worth of energy.

If v = 0.99999999c, then the factor in parentheses is about 1000. For about every two nines, you gain an order of magnitude in energy, so you're going to need about 54 9's after the decimal point to have about a gram's worth of kinetic energy in a proton.

 

[YHPats]

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In that case, could it be that things can exceed the speed of light, but we just can't observe them because they're traveling faster than light?
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Why would this be so ?
After all, we can hear things that travel faster than sound.

 

[cquark]

Originally posted by: Fox5
Hmm, can I propose one more thing...
The speed of light is a constant from any frame of reference, right?
In that case, could it be that things can exceed the speed of light, but we just can't observe them because they're traveling faster than light?

Tachyons are hypothetical particles that travel faster than light. They have some odd properties, such as not being able to travel any slower than the speed of light and the fact that increasing their energy causes them to decrease in velocity. They also could be used to define a preferred reference frame, allowing you to absolutely synchronize clocks in different frames and thus create absolute simultaneity, violating the central concept of special relativity.

However, there's no fundamental reason why we couldn't observe tachyons as we do any other particle and we haven't seen any. Tachyons would also have some distinguishing properties, such as generating Cerenkov radiation in a vacuum, which we've also never seen.

 

[mdchesne]

matter cannot reach the speed of light because at the speed of light, matter become energy...

actually, it gradually dissociates into energy until it reaches C where all matter has been converted.

 

[biostud]

What about this scenario:

In space you launch two objects in opposite directions, and you continue to accelerate these until reaching above 50% of the speed of light, wouldn't these objects travel faster than light relatively to each other?

 

[mdchesne]

no. all speed is relative to space ether, not individual objects

 

[Skyclad1uhm1]

Originally posted by: mdchesne
no. all speed is relative to space ether, not individual objects

And as electrons move around the atom core accelerating the atom to light speed would mean that either all electrons have to come to a complete stop in their position to the atom, have to move all to one side (away from the direction the atom moves in), has to 'escape' from the atom core, or has to move faster than light speed.

 

[cquark]

Originally posted by: mdchesne
no. all speed is relative to space ether, not individual objects

There is no ether. All velocities are relative to other objects. That's essentially the point of special relativity.

 

[cquark]

Originally posted by: biostud
What about this scenario:

In space you launch two objects in opposite directions, and you continue to accelerate these until reaching above 50% of the speed of light, wouldn't these objects travel faster than light relatively to each other?

No, you have to combine velocities u (of object 1) and v (of object 2) relativistically using the formula

(u+v)/(1 + uv/c^2)

which cannot exceed c.

 

[alienal99]

i have a very fundamental problem with the idea that nothing can accelerate to the speed of light. that is that light accelerates to the speed of light, and for light to travel, it must be made of something. You can use the photon theory of light to claim that it is massless, but how does a particle of nothing (paradox) move? It simply cannot. the idea that light is always everywhere it just needs to be "turned on" is one that would make more sense. We could think of "light" as a photon being turned on. These photons could be stationary, and similar to a wave of water energy or as we call it "light" could simply move through this sea of photons. This way there would not need to be a mass to the photons as they would not need to move, rather they become energized. I just thought this all up and it may have thousands of holes, so pick it apart and tell me what you think.

alex phillips