# What exactly is a particle?

1. Jul 31, 2003

### kleinma

what exactly is a particle?

I know (well correct me if Im wrong) that an atom is a element.. like an atom of hydrogen etc...

and molecules are made up of atoms.. like a water molecule is made of 2 hydrogen and an oxygen atom..

so where does particle fit in?

and what does a particle accelerator do exactly (I know it accelerates particles... but I am looking for a more indepth answer )

Dictionary.com had these definitions under particle

Last edited by a moderator: Feb 5, 2013
2. Jul 31, 2003

### neutroncount

A particle can be many things. A particle of dust, of sand. But I believe you're talking about subatomic particles. Subatomic particles make up matter (atoms). Leptons and Hadrons make up the elementary particles. Hadrons come in two flavors: Baryons and Mesons. Leptons also do: electrons and neutrinos. And example of baryons are protons and neutrons. Quarks are a sub-subatomic particle responsible for the creation of hadrons.

A particle accelerator accelerates these particles with both magnetic and electric fields. A magnetic field can keep charged particles in focus while electic fields can provide energy for acceleration. An accelerator's job is mostly to smash together isotopes or particle bunches into each other or fixed targets so that new variation of isotopes or particles are made. It's a very basic answer but it at least gives you an idea.

3. Jul 31, 2003

### kleinma

so when your in high school and they tell you that atoms are the basic building blocks of matter... is that just to not confuse you with the lower levels of matter such as the ones you just mentioned?

4. Jul 31, 2003

### Integral

Staff Emeritus
Let us assume that you mean sub atomic particles, as surly you can seperate this use of particle from the everyday use as in "particle of dust".

There are differnt types of subatomic particles, those that have mass and combine to form atoms and those that transfer energy between other particles.

The atom is composed of electons, protons and neutrons, the first of these are the ones frequently used in particle accelerators, which essentially use magnetic fields to accelerate charged particles, generally these force the particles to move in large circles, the magnetic field pushes them to higher and higher speeds through special channels which are maintaining a high vacumn. These devices have sufficient amounts of energy to accelerate sub atomic particles to speeds which, were it not for the effects of relativity, could exceed the speed of light. It is these tools that have experimentally verifed the predicition of Einstein, that we cannot go faster then c.

Particle accelerators create extememly energetic collisons of elementary particles by creating counter rotating streams of particles which at special points in the beam path are diverted to collied head on, sensors then detect the debrie from these colliding particles. In this manner the beasts of the particle zoo are released for study.

5. Jul 31, 2003

### neutroncount

Well they are only telling you part of the story. Atoms are the building blocks of matter. Subatomic particles are the building blocks of atoms. Quarks are the building blocks of hadrons. But for totality you could say that leptons and quarks are the lowest part of the building blocks of matter.

6. Jul 31, 2003

### kleinma

havent experiments been conducted where they did produce speeds greater than c.. i can't remember the details.. just that someone had claimed to do it..

7. Jul 31, 2003

### neutroncount

No. Nothing travels faster than c. Group velocities are always below c. But phase velocities CAN exceed c. A good example is wave peaks in a wave packet that move relative to the wave packet.

8. Jul 31, 2003

### kleinma

why is it that light is the fastest thing in the universe?

9. Jul 31, 2003

### Integral

Staff Emeritus
One could claim that light (or any electo magnetic wave) is a ripple in the fabric of space time thus it travels at a speed that is determined by the nature of space time. So far we have not discovered a theory or experiment which allows us to exceed this speed. Why?... 'Cus thats the way it is.

10. Jul 31, 2003

### chroot

Staff Emeritus
Something has to be.

- Warren

11. Jul 31, 2003

### kleinma

I assume you are joking... but being that I am not a person of advanced scientific knowledge.. I tend to try to take everything said in here seriously..

If that were truly the case.. then it would be very very easy to believe that something unseen travels faster like dark matter in some form or something like that..

also: does all light travel infinitly?

12. Jul 31, 2003

### zoobyshoe

Kleinma,

Regarding faster than light sig-
nals: I, too, saw a show on TLC
or Disc or PBS a few years ago
to have run into a situation where
this was happening. He was also
able to reproduce it at will.

I haven't heard anything about it
since. The usual explanations
probably apply: it was a hoax, a
complicated mistake, or was never
explained to anyone's satisfaction
and people lost interest.

Zooby

13. Jul 31, 2003

### LURCH

It would seem that the speed of light is the speed at wich waves propogate through spacetime itself (the whole "fabric of space" concept). And it's not just light but gravity waves are also supposed to travel at c. Although they have not yet been directly observed, that should come soon. LIGO should find solid confirmation of gravity waves in the very near future. If other forces are discovered to exist as fluctuations of spacetime, these forces will (it can be assumed) also propogate at light speed.

14. Jul 31, 2003

### zoobyshoe

Refering to "C" George Gamow says:

Though usually known as the
velocity of light' it can better
be described as the propagation
velocity of physical interactions'
since any kind of forces that act between material bodies, whether
the forces of electric attraction
or the forces of gravity, spread through empty space with the same
speed."

-One, two, three ... Infinity
-George Gamow

_Zoob