Lightspeed

[goku]

instead of saying partical mass increases, why not say, approching the photonic barier ;)

 

how many rounds per second do the particles make in the accelerater?

[Pyrotex]

instead of saying partical mass increases, why not say, approching the photonic barrier ;)

how many rounds per second do the particles make in the accelerater?

The phrase "photonic barrier" comes from Star Trek episodes and a few really second rate Sci-Fi movies.

In physics, there is no such thing as a "photonic barrier".

 

What there IS is the speed of light in a vacuum, represented as c.

 

Assume a circular accellerator with radius of 1 km.

Circumference is therefore 3.14 km.

The exact velocity of c is metres per second is 299,792.458 km/sec

Assume the particle is at 99.999% c.

The particle travels at 299,789.46 km/sec.

Divide by 3.14 km, and we have:

95,474.35 circuits per second.

[CraigD]

how many rounds per second do the particles make in the accelerater?

:D You should try working this out yourself, goku. It’s a very simple calculation – look up the circumference of some particle accelerator, and divide the speed of light by it.

 

It’s hard to think about science if you can’t quickly do simple calculations like these. With experience, you’ll find you can do them nearly or completely in your head. Without basic skills like this, not only is it hard to read and learn science, it’s nearly impossible to tell good science writing from bad.

[goku]

The phrase "photonic barrier" comes from Star Trek episodes and a few really second rate Sci-Fi movies.

In physics, there is no such thing as a "photonic barrier".

 

What there IS is the speed of light in a vacuum, represented as c.

 

Assume a circular accellerator with radius of 1 km.

Circumference is therefore 3.14 km.

The exact velocity of c is metres per second is 299,792.458 km/sec

Assume the particle is at 99.999% c.

The particle travels at 299,789.46 km/sec.

Divide by 3.14 km, and we have:

95,474.35 circuits per second.

 

crap, i thought i was original on the P B.

i've heard of kiev light, i think is how you spell it.

 

dang that's fast, the amount of G-forces must be enormous.

just imagine being in a race car making that many rounds per second :D

what about the G's on the particles?

[goku]

:D You should try working this out yourself, goku. It’s a very simple calculation – look up the circumference of some particle accelerator, and divide the speed of light by it.

 

It’s hard to think about science if you can’t quickly do simple calculations like these. With experience, you’ll find you can do them nearly or completely in your head. Without basic skills like this, not only is it hard to read and learn science, it’s nearly impossible to tell good science writing from bad.

 

back-off buddy, i didn't know the speed of light, besides i like talking to people.

 

in my head? please, i'm a farmer

[CraigD]

back-off buddy, i didn't know the speed of light, besides i like talking to people.

 

in my head? please, i'm a farmer

And I’m a medical applications computer programmer, a profession that’s about as likely to require that you know the speed of light as farming. I still contend that every educated person – which should be every adult on Earth – should know how to divide speed by length to find time, and know from memory a few important approximate physical constants like the speed of light. Besides the general virtue of being educated, you never can tell when knowing a few science and engineering basics will come in handy.

 

The speed of light © is approximately [math]3\times10^8\,\mbox{m/s}[/math]. It’s exactly 299792458 m/s, but unless you’re a professional scientists or engineer who uses the precise value as part of your everyday work, or one of those people who likes to or can’t help memorizing strings of digits, I wouldn’t expect you to know its exact value without looking it up. I do expect anyone who can access a website to be able to look up the exact value of the speed of light in less time than it takes him to type and submit a post at hypography. Without the ability to look stuff up, hardly anybody would be able to write even vaguely accurate science.

i've heard of kiev light, i think is how you spell it.

I think you’re thinking of Čerenkov radiation. It happens when a charged particle, typically an electron, travels though a medium, such as water, faster than photons can travel though it, and is commonly and not too inaccurately described as a “photonic shock wave” analogous to a sonic boom. You see it a lot in water-cooled nuclear reactors, as they emit a lot of high-speed electrons into pools of water.

 

A confusing bits of science terminology is the speed of light in a medium, which suggests that photons actually travel slower in media like glass and water than they do in vacuum, and that, because matter can move faster than the speed of light in a non-vacuum medium, it might be able “break the Cerenkov barrier” in vacuum, too, and like a supersonic aircraft or projectile, travel a little or many times greater than c. This isn’t the case. Photons traveling through other than vacuum never travel at a speed other than c, they just spend time interacting with stuff – mostly electrons in the atoms of the medium.

 

A rough analogy is a letter carrier driving from mailbox to mailbox along a straight road. Even though it takes her an hour to travel a mile-long route, giving a “speed of mail carrier on route” or 1 mile/hour, when she’s driving, she’s always going her ratty jeep’s top speed of about 45 miles/hour.

dang that's fast, the amount of G-forces must be enormous.

just imagine being in a race car making that many rounds per second :eek:

what about the G's on the particles?

The formula for centripetal acceleration is [math]a = \frac{v^2}{r}[/math], so if we use Pyro’s example of a 500 m radius (if its circumference is 3.14 km , its diameter is 1 km, its radius half that), [math]a \dot= \frac{9\times10^{16}}{500} \dot= 2\times10^{14}\,\mbox{m/s/s}[/math]. Since 1 g is about 10 m/s/s, this is about [math]2\times10^{13}[/math], or twenty trillion gees.

 

If we use an accelerator like the LHC, which has a radius of about 4300 m, this is reduced to “only” about 2 trillion gees.

 

Enormous as this acceleration is, an electron can’t “feel” it, because an electron is a fundamental particle, with no “parts” inside it capable of detecting or experiencing acceleration.

 

Particle accelerators can accelerate particles other than electrons. The LHC, for example accelerates either protons or nuclei as heavy as lead. As these particles are composite, and some of their sub-particles don’t interact magnetically, they do “feel” both linear and centripetal acceleration due to the magnetic fields these accelerators use. In principle, a tremendously strong accelerator might be able to “break” the neutrons out of a heavy nucleus, or even break the quarks and gluons out of a proton. However, we can calculate that the strong interaction, which binds quarks into protons and neutrons and protons and neutrons into nuclei, can withstand about [math]10^{31}[/math] gees acceleration, about a quadrillion times more than what we calculated for the a circular particle accelerators centripetal force.

 

Protons and Nucleii are very strong!

 

Now, if someone were to try to accelerate something like, say, Styrofoam insulation beads (you know there’s lots of excess charge in those things, if you’ve ever had them sticking all over you ;)) in a big particle accelerator, they’d come apart very easily. I don’t thik it would be very spectacular, though, as all that would happen is that the small excess number of protons in nuclei or electrons would be accelerated, leaving the large majority of neutral atoms behind. Essentially, it would be using a particle accelerator as a very expensive degausser.

[Mercedes Benzene]

back-off buddy, i didn't know the speed of light, besides i like talking to people.

 

in my head? please, i'm a farmer

 

Please don't tell one of our staff members to "back off."

One of the things that we stress here (and something that has been stressed by various members in this thread already) is how important it is to be able to do research. If you didn't know the speed of light, it wouldn't take more than a quick Google search to figure it out.

Instead of people feeding you information, you would find it to be much more beneficial to derive this information yourself.

 

MB

[goku]

Please don't tell one of our staff members to "back off."

 

:hihi: nah i was just yankin his chain :)

[Pyrotex]

If your intention here is just to yank people's chains, perhaps you should go find another website where that is considered good clean fun.

Here, it is considered a rude waste of our time.

 

Pyrotex

another Moderator

[goku]

If your intention here is just to yank people's chains, perhaps you should go find another website where that is considered good clean fun.

Here, it is considered a rude waste of our time.

 

Pyrotex

another Moderator

 

it's either the way i word phrases or most people here are anti-social

 

waste of our time?

perhaps i fail to see the urgency and importance of time at this forum

[Pyrotex]

it's either the way i word phrases or most people here are anti-social...perhaps i fail to see the urgency and importance of time at this forum

Goku, we have read enough of your posts to know the problem.

 

You take pleasure in "yanking people's chains" as you say it.

We call that "being rude".

 

You fail to see the importance of time here because you do not expect to benefit from your time here--you have no intention of learning anything.

We call that "being a slacker".

 

You fail to take any measures to either say what you mean or mean what you say--and you don't care either way.

We call that "being a simpleton".

[Moontanman]

it's either the way i word phrases or most people here are anti-social

 

waste of our time?

perhaps i fail to see the urgency and importance of time at this forum

 

Goku, everyones time is important, I've sent significant hours searching for information and answers to your questions only to have to shrug them off like I was an idiot child. That behavior is antisocial, it's rude, and there is no reason for it.

[goku]

You take pleasure in "yanking people's chains" as you say it.

We call that "being rude".

 

i will try to refrain from "being rude" as you say it

[HydrogenBond]

Here is an interesting observation about the speed of light. If we take a mass and increase its velocity toward C, SR says the mass (relativistic mass) will increase toward infinity. But on the other hand, if we have a photon moving at C, forming a matter-antimatter pair, the system will go from C to less than C, while skipping over the infinite mass barrier. It is like a check valve that goes one way much easier.

[watcher]

If we take a mass and increase its velocity toward C, SR says the mass (relativistic mass) will increase toward infinity. But on the other hand, if we have a photon moving at C, forming a matter-antimatter pair, the system will go from C to less than C, while skipping over the infinite mass barrier. It is like a check valve that goes one way much easier.

 

HB,

interesting. what specifically is this reverse flow that the check valve was supposed to stop ?

 

here is an interesting observation about the speed of light.

 

btw, the only observation i know about lightspeed is the emission of photon from one point and the absorption of the same photon from another point. no one i think have ever actually observed a cruising photon much the same way we observed an arrow cruising in space over a period of time. the so called c is just an extrapolation from the time the photon is emitted and absorbed between two points. i'm not sure if this is still the case today but im sure we already knew that photons jump.

 

i am thinking about if c is an absolute speed in its truest sense of the word or its constancy is just a postulate exclusively within the SR/GR theory. but since SG/GR are far from being the theory of everything, i am not sure if a constant c can hold out on its own. for instance there is no postulate i know of in QM that forbids faster than lightspeed neither C is an absolute exact value. maybe its constancy is a valuable tool in math to do relativity but my understanding is that everything in nature is infinitely divisible and therefore all values we can derived cannot be exact but will always be an approximation plus or minus to nth degree of accuracy.

 

so a photonic jump from an approximated position is space to another probable position in space cannot always have the same exact value for c. maybe it varies but the variation is so small it is not noticeable by our current capability to detect or so small that the theory of relativity can ignore it without much affects to the theory in general.

[CraigD]

Here is an interesting observation about the speed of light. If we take a mass and increase its velocity toward C, SR says the mass (relativistic mass) will increase toward infinity. But on the other hand, if we have a photon moving at C, forming a matter-antimatter pair, the system will go from C to less than C, while skipping over the infinite mass barrier. It is like a check valve that goes one way much easier.

The second phenomenon you describe – pair production – is an interesting example of energy and momentum conserving conversion of mater to energy, but I’d describe the “check valve” as being easier to pass in the matter-to-energy direction, rather than the energy-to-matter direction you suggest.

 

A photon above the energy equivalent of twice the rest mass of a particle can become the particle and its antiparticle (eg: 250 EHz photon into an electron and positron). For these particles to ever be observed – in other words, for them to be real, rather than virtual – they must interact with other particles in a fairly extraordinary way, such as a close pass with an atomic nucleus or a black hole, or they will collide and annihilate with one another and convert back into a photon with the same momentum and energy as the original.

 

On the other hand, a particle and its antiparticle, having opposite charges, will, unless measures are taken to prevent it, promptly ”pair annihilate” into two or more photon (or, less commonly, other particles).