why does light travel so fast

[Money]

photons have no mass and that is what makes

them move so fast rite well are there no other

particles that contain no mass ??

 

and is a particle an atom or made up of atoms

if so if light is pure energy wouldnt the atoms

be made of pure enery ???

[lakmilis]

well, we used to think that an atom was an particle yes, but now we would say an atom is made up of particles. a photon however we still say is an elementary particle. I think photons are meant to have a rest mass *if* they were stopped , however this is a boundary it is believed which can not be achieved. (might be wrong on the assumptions of the rest mass) .

 

And yes, everything we know is made of pure energy as such. Mass is another form of it (E= mc^2)

 

why light has its speed is hardcoded into our reality, this universe. I don't think it is correct to say it is because they are massless that they are so fast...I mean sure, but by that inference one would equally wonder why is the speed not infinite rather than a finite value.

 

[geoguy]

an aside: lakmilis touches upon an important concept in 'science'. Science is about the 'what' and not the 'why'. The 'why' is ok to pursue at a finite level of what's happening, etc. to explain a result and so on but the 'evidence' is the physical 'what'. When the word 'why' can be replaced in some phrasing with 'what' it is subject to scientific methodology....when the word 'why' is more of open ended speculation then it's left the realm of science (not that it isn't worthy of fascinating discussion).

 

When I first doing research in geology I kept asking 'why' . Children never stop asking 'why'. Over the years one realizes the the 'whys' get fewer and one accepts that reality is what reality is regardless of any human curiosity or need to place it in some larger meaning. 'Why' begins a treadmill to more 'whys' and implies purpose rather than scientific conclusion.

[lakmilis]

Hehe, I completely agree (I mean with your noted observations). If one works in science , one never really can explain as such...merely describe. Or rather one can answer a bunch of sub-sets of whys which translate I guess to the whats as you say.

 

The only thing I disagree somewhat with though, is that, science is still a subset of philosophy, not the other way round? what do you think?

[Money]

besides the why and what factor wich i understand

wat u mean now but

i thought that Atoms were made of quarks

and does light travel through objects??

[lakmilis]

Well, I guess the standard today is to refer to particles as elementary particles...such as you say quarks. Although yes, often in such topics one sometimes talks about particles at a certain level, even if they are made of sub particles...generally however, this is not the case, so particles would not be made up of atoms but like you say , atoms of particles, namley quarks.

 

light can travel through objects yes. by shining on a paper in dark, you can see it illuminate the other side somewhat damped....photons have either passed through or been absorbed and reemitted right? and not being sure how you are visualising objects...but if a medium is an object, light travels through water lets say, right? it can do so because photons are so minute they evade structure of a higher magnitude than the molecules lets say.

 

But if you define an object as (these elementary)particles , then no photon can pass through them. No photon can pass through a neutrino, although hehe might bulldoze it over

[YT2095]

photons Collide and interact with particles quite regularly (you wouldn`t be able to See otherwise, or feel the heat of the sun on your skin).

 

Light like a bullet fired in a forest will travel X distance before it hits something or gets deflected, does it hit things, Yes, can it pass through things NO, can it pass through the gaps between things (a thin forest) sure.

[geoguy]

Hehe, I completely agree (I mean with your noted observations). If one works in science , one never really can explain as such...merely describe. Or rather one can answer a bunch of sub-sets of whys which translate I guess to the whats as you say.

 

The only thing I disagree somewhat with though, is that, science is still a subset of philosophy, not the other way round? what do you think?

 

That's a question that could start food fights.

 

If philosophy is defined as some pursuit of wisdom or rational thought then, yes, science is a subset of philosophy. If philosophy is defined as having some connection to ethics, morality or seeking 'the Truth' then maybe not. Science in an ironic way is the antithesis of seeking 'Truth'. It's almost an acknowledgement that there is no end game such as 'the Truth' and that the process must constantly evaluate itself and be open to accept evidence that dethroans theories.

 

Science can be a subset of Philosophy or a tool of philosophy...as can mathematics. To further cloud the water, it's been debated whether mathematics is a science. Does mathematics present any evidence of anything that is not self-fulfilling by the logic of mathematics? Yikes...my brain won't turn off.

 

I suppose I lean towards science being a subset of philosophy. My reluctance to view it that way is that in the real world of day to day debate, the door opens to convaluted arguments justifying pursuit of concepts such as 'intelligent design', anthropic principle in physics and so on.

[Severian]

photons have no mass and that is what makes

them move so fast rite well are there no other

particles that contain no mass ??

 

Gluons and (presumably) gravitons also have no mass.

 

and is a particle an atom or made up of atoms

if so if light is pure energy wouldnt the atoms

be made of pure enery ???

 

 

Photons are not just 'pure energy'. They have other characteristics too. They carry energy, but they are not 'just' energy.

[Money]

but i read that photons have no charge so how kan they carry energy

[Severian]

What does having no charge have to do with it?

 

That is like saying, the bus is not red so how can it carry passengers?

[Money]

idk i thought charge was related to energy lol

i dont kno alot about this stuff

[lakmilis]

That's a question that could start food fights.

 

If philosophy is defined as some pursuit of wisdom or rational thought then, yes, science is a subset of philosophy. If philosophy is defined as having some connection to ethics, morality or seeking 'the Truth' then maybe not. Science in an ironic way is the antithesis of seeking 'Truth'. It's almost an acknowledgement that there is no end game such as 'the Truth' and that the process must constantly evaluate itself and be open to accept evidence that dethroans theories.

 

 

 

Science can be a subset of Philosophy or a tool of philosophy...as can mathematics. To further cloud the water, it's been debated whether mathematics is a science. Does mathematics present any evidence of anything that is not self-fulfilling by the logic of mathematics? Yikes...my brain won't turn off.

 

I suppose I lean towards science being a subset of philosophy. My reluctance to view it that way is that in the real world of day to day debate, the door opens to convaluted arguments justifying pursuit of concepts such as 'intelligent design', anthropic principle in physics and so on.

 

Hi Geoguy, thanks for a nice reply, very nice to read...haha, how can we be discussing physics on a forum if we did not enjoy the odd food fight

but joking aside, I had a lot to write earlier today but just got home and am tired. A thing which struck me is when you say you don't think philosophy working with truth is relevant with science (as you say it is opposite more or less). Remember, by saying we continously redefine theories through *facts*, you imply as we all do, a fact is part of that which is true. I think maybe you mean that the set of knowledge (recognising facts) is indeed truth, but is this set finite or infinite. If infinite, then we can never create absolute theories of truth ya? then again, as you see, this is why as scientists, it is important to understand which paradigmes we must yearn for...aka philosophy

 

about the mathematics, yes immensely lovely topic; I am simply too tired now to write on it, but these are the areas where the symbiosis of science and philosophy is so bounded in love (speaking non-formally if I may )

 

anyway, I like your posts

 

lak

[YT2095]

but i read that photons have no charge so how kan they carry energy

 

energy of velocity/momentum.

 

lets go with my Bullet idea again, it has no electrical charge, but makes a hell of BANG when it hits a metal sheet (energy).

now I know you`re going to say "but a bullet has Mass YT" and yes it does, BUT its Velocity (in 100`s feet per second) cannot be compared with 100`s of Thousands of KiloMetres per second!

that More Than makes up for any missing Mass

[Realitycheck]

When a photon hits an atom, why would two photons come out the other end? Do other particles (gluon? electron?) get recruited to be used as a photon (perhaps weakening the structure of the atom), or does the photon get split into 2 weaker photons?

[the tree]

I'm fairly sure two photons aren't the result of an entire atom and a photon. But anyways, an atom is made of (on a quantum level, kind of) pretty much the same stuff as a photon.

 

Throwing a huge chunk of china at a china teapot will result in many chunks of china as a result of that collision. That was probably the worst analogy ever, but either way my point was that they're both made of the same stuff.

[swansont]

When a photon hits an atom, why would two photons come out the other end? Do other particles (gluon? electron?) get recruited to be used as a photon (perhaps weakening the structure of the atom), or does the photon get split into 2 weaker photons?

 

It depends on the reaction. Sometimes the most likely relaxation channel gives you more than one photon; you have to look at all of the properties that need to be conserved. The photon is created, but is not the result of other particles getting used up.

[grifter]

simply think of it as conservation of energy, if the atom is to remain unchanged when it accepts a photon it must release one, however if an atom is to release two photons when one is input, the atom must already be in an excited state, (this happens to be the principal lasers work on) this can be seen as electrons "moving up" "energy levels" when they are excited, this excitement can occur when a photon of a specific frequency interacts with the atom; when the excited electron "drops down" to its ground state it must emit energy, this is in the form of a photon, Okay?

[foodchain]

Well, I guess the standard today is to refer to particles as elementary particles...such as you say quarks. Although yes, often in such topics one sometimes talks about particles at a certain level, even if they are made of sub particles...generally however, this is not the case, so particles would not be made up of atoms but like you say , atoms of particles, namley quarks.

 

light can travel through objects yes. by shining on a paper in dark, you can see it illuminate the other side somewhat damped....photons have either passed through or been absorbed and reemitted right? and not being sure how you are visualising objects...but if a medium is an object, light travels through water lets say, right? it can do so because photons are so minute they evade structure of a higher magnitude than the molecules lets say.

 

But if you define an object as (these elementary)particles , then no photon can pass through them. No photon can pass through a neutrino, although hehe might bulldoze it over

 

Yes, but if you turn a lightbulb on in a box, how would a person outside of the box ever know this?

[insane_alien]

the box would absorb the photons emitted by the lightbulb, heat up and radiate outside. using a thermographic camera you would see that it would be hotter than the surroundings.

[lakmilis]

insane aliens answer is one answer. Additionally, I said photons may travel through without hitting molecules etc... In the box you mention (if it was of paper, photons would get through , you would see the box illuminated with some inner source right ) but lets say it was wooden....then obviously due to the thickness from experience light wouldn't be seen, so it manages to absorb the photons.

[swansont]

simply think of it as conservation of energy, if the atom is to remain unchanged when it accepts a photon it must release one, however if an atom is to release two photons when one is input, the atom must already be in an excited state, (this happens to be the principal lasers work on) this can be seen as electrons "moving up" "energy levels" when they are excited, this excitement can occur when a photon of a specific frequency interacts with the atom; when the excited electron "drops down" to its ground state it must emit energy, this is in the form of a photon, Okay?

 

The system doesn't have to be in an excited state. There are nonlinear crystals that do parametric down-conversion. There are also examples of a weak transition that absorbs a photon, but a much stronger decay path to a different level that then requires more than one photon to get back to the ground state.