speed of light limit

Kelter

hey there phisics heads. I started reading the stickys to see if my question was already answered and could hardly under stand a word. Now I know I'm in the right place.

Hope this hasn't come up to often in the past.

Well you know the way the speed of light is meant to be the limit for how fast things can go... well what would have happened if the human race were blind? If we had developed by evolution without the ability to see... then would we be unable to have found out about this limit... yeah

As a follow on from this... lets say we used sound to "see" for want of a better word, as our main sense. Then would we have decided that it was the limit?


Finally what if we are blind... like what if there is anouther sense that we don't have? (for example as humans we generally can't sense magnetic fields etc)


Please don't jump to rubbishing my final point until you've answered the first... thats the real question

Thanks

Anti

If we were all blind from the start, i think the dinosaurs would probably have picked us off before we stopped dragging our knuckles on the ground...

So your point is herein made irrelivent.

And just because we cant see, dosent mean it dosent exist, does it !

And a extra sense you say eh ! What like beaing driven mad by high picted noises like dogs ?

JC 2K3

The term "speed of light" is pedantically incorrect. "Speed of electromagnetic waves in a vacuum" would be more correct. Hence your whole blindness theory not making much sense, since I'm presuming if we were blind we could find some way of measuring, say, the speed of infra-red radiation(a method of heat transfer, we'd be able to feel heat right?) which would be the same as the "speed of light".

Your post is probably more suited to the Philosophy board, but even then it is rather incoherent.....

Son Goku

Kelter wrote:

Well you know the way the speed of light is meant to be the limit for how fast things can go... well what would have happened if the human race were blind? If we had developed by evolution without the ability to see... then would we be unable to have found out about this limit... yeah

As a follow on from this... lets say we used sound to "see" for want of a better word, as our main sense. Then would we have decided that it was the limit?

No, the speed of light could have been found by several means. There are several things in physics which don't involve things we can sense and yet we can figure out their properties.
For instance colour charge in the strong force, we didn't even know it existed until the 1950s, but we know how it behaves now.

The speed of light is a limit built into the structure of spacetime.

Kelter wrote:

Finally what if we are blind... like what if there is anouther sense that we don't have? (for example as humans we generally can't sense magnetic fields etc)

Then we would have another sense, along with whatever effects that would have on our sociology.

Professor_Fink

Hi Kelter,

To answer your questions:

1) The human race discovered the speed of light limit essentially due to Maxwell's equations, which describes electromagnetic interaction. All the atoms that make up each of us, and the matter all around us are held together largely do to the electromagnetic interaction. Small perturbations in this field are called light (although this really includes radiowave, infrared, UV, Xrays and gamma rays, as well as visible light). Whether or not we can see light, we can definitely detect electromagnetic fields (otherwise our bodies wouldn't stick together). Soeone would have come up with special relativity whether they could see or not.

2) Sound has very different properties, and is basically a vibration traveling through a material, rather than a field. There is no way anyone could ever have been convinced that the speed of sound is a fundamental limit, since we detect particles which go many times the speed of sound in air (cosmic rays go at close to the speed of light).

3) We do indeed detect vibrations in the electric and magnetic field as light. Sensing static fields wouldn't tell us anything about fundamental limits on speed. Sure, someone may have come up with Maxwell's equations earlier, but that doesn't change the result.

You seem to be sugesting that the laws of physics depend on human evolution. Physical laws aim to cover all phenomena in the universe, and are completely independant of human evolution. The only impact that our senses have is on how quickly we discover these laws, and at this stage our knowledge of physics far out strips anything our senses could tell us, so we have passed the point where different senses may have had an impact on the orer we discover physical laws in.

bonkey

Kelter wrote:

Finally what if we are blind... like what if there is anouther sense that we don't have? (for example as humans we generally can't sense magnetic fields etc)

Indeed. What if we are?

Consider - there's a lot we've discovered that we cannot directly observe. We've discovered these things by inferring their existence, and then inferring how they could be indirectly detected.

So if there's something we're "blind" to. one has to ask whether you mean blind in the sense of "cannot perceive directly" or "cannot perceive at all".

In the former case ,we can perceive indirectly, so its no big deal.
In the latter case, we cannot interact with whatever it is, directly or indirectly (or else we wouldn't be blind to it), so its no big deal.

So the conclusion should be that its no big deal if there's something out there that we're blind to.

Kelter

Guys, Thanks a lot for the answers. They are really good. Well the latter ones anyway.

I guess my point is that it seems wrong to me that a physical constant, such as the maximum speed possible, should be something so convenient as to be something so easily relate to. It really does suggest an intelligence in the organization of it all.

Pi however is a bit scientific. I mean it is a pretty meaningless number. Wouldn't it be a bit more natural phenomenon if the maximum speed possible was 3.14 times the speed of light?

Civilian_Target

No - our maths system is based on straight lines. Light travels in a straight line.

Does the moon still orbit the earth if there's no-one there to observe it?

Son Goku

Kelter wrote:

Guys, Thanks a lot for the answers. They are really good. Well the latter ones anyway.

I guess my point is that it seems wrong to me that a physical constant, such as the maximum speed possible, should be something so convenient as to be something so easily relate to. It really does suggest an intelligence in the organization of it all.

Pi however is a bit scientific. I mean it is a pretty meaningless number. Wouldn't it be a bit more natural phenomenon if the maximum speed possible was 3.14 times the speed of light?

The speed of light is just a constant of the universe, coming from the way spacetime is built. Light however, due to the way it interacts with things, carries a lot of information about the objects it reflects off. Obviously being able to detect light would be a huge advantage to many species because of this. There is nothing convenient about it.

Literally, the fastest thing in the universe carries a lot of information, so we evolved to be able to interact with it.

Professor_Fink

Kelter wrote:

Guys, Thanks a lot for the answers. They are really good. Well the latter ones anyway.

I guess my point is that it seems wrong to me that a physical constant, such as the maximum speed possible, should be something so convenient as to be something so easily relate to. It really does suggest an intelligence in the organization of it all.

Pi however is a bit scientific. I mean it is a pretty meaningless number. Wouldn't it be a bit more natural phenomenon if the maximum speed possible was 3.14 times the speed of light?

Hi again Kelter,

The speed of light doesn't need to be regarded as a fundamental constant, since it can be derived from the permittivity of free space. Largely we arrange equations in ways such that they contain quantities we find meaningful. The equations don't change, just the way we like to write them.

ecksor

Civilian_Target wrote:

No - our maths system is based on straight lines.

Hm?

Kevster

Kelter wrote:

Well you know the way the speed of light is meant to be the limit for how fast things can go... well what would have happened if the human race were blind? If we had developed by evolution without the ability to see... then would we be unable to have found out about this limit... yeah

As a follow on from this... lets say we used sound to "see" for want of a better word, as our main sense. Then would we have decided that it was the limit?


Finally what if we are blind... like what if there is anouther sense that we don't have? (for example as humans we generally can't sense magnetic fields etc)

I love your views because they show inventiveness and a creative mind - Things that have advanced the human race and continually do-so. I am also a firm believer that we are 'blind' to more senses. It would be very arrogant of us to think otherwise.

Professor_Fink

Kevster wrote:

I am also a firm believer that we are 'blind' to more senses. It would be very arrogant of us to think otherwise.

Actually, if there were forces, other than the 4 we percieve (we only experience two of these directly), we would expect to see a difference in the branching fraction of decays of mesons etc. As it is, we see no such discrepancies.

Frankly I think that people who claim we are missing something because of a lack of some sense are completely ignorant of modern physics. #we haven't relied directly on our senses in a long long time.

Kevster

You are entitled to think that but you are wrong because I am not ignorant of modern physics and I'm sure there are others like me who are the same.

It is important to not believe everything you are told. However, we do also need people who DO believe everything they are told (everything that is science-related). That is the wonder of humanity - Diversity.

JC 2K3

Kevster wrote:

I love your views because they show inventiveness and a creative mind - Things that have advanced the human race and continually do-so. I am also a firm believer that we are 'blind' to more senses. It would be very arrogant of us to think otherwise.

If we can't perceive something how can it "exist"?

We are "blind" to many things, yet we have found ways around that.

If there is no way to measure/sense something then it doesn't exist.

Professor_Fink

Kevster wrote:

You are entitled to think that but you are wrong because I am not ignorant of modern physics and I'm sure there are others like me who are the same.

Well then you will know that the standard model + general relativity accurately describe not just the world we observe through our senses, or the world we interact with directly, but also virtually every physical system we have ever encountered.

So there are essentially four forces. All of our senses work through the electro-magnetic interaction. The weak and strong interactions are to short range to be the basis for a useful sense, and gravity is far too weak.

If there was some other force that lead to a useful sense, then we would expect matter to interact via that force. It doesn't, since otherwise branching fractions for particle decays would be different. If there is another force it would have to be incredibly weak, and we could not possibly use it as a sense.

It is important to not believe everything you are told. However, we do also need people who DO believe everything they are told (everything that is science-related). That is the wonder of humanity - Diversity.

I'm not entirely sure where you're going with this, but if the aim is to suggest that I blindly believe what I'm told about science, you would be wrong. I am a physicist, as it turns out.

Kevster

Kevster wrote:

It is important to not believe everything you are told.

That's why we study the derivations of equations/proofs etc

If there is no way to measure/sense something then it doesn't exist.

Well either that or we're inadequate at measuring, however I'm not sure what context this was in so I won't nitpick...

Son Goku

Kevster wrote:

I love your views because they show inventiveness and a creative mind - Things that have advanced the human race and continually do-so. I am also a firm believer that we are 'blind' to more senses. It would be very arrogant of us to think otherwise.

Of course we could be blind to other senses. There is a huge collection of possible senses, one could literal just start listing them off. All a "sense" is, is a method by which an organism gathers some information about the world through interactions. It doesn't affect how we can model the world though.

Kevster

Well, I think I'll leave this thread because my (secret) predictions have been satisfied. Oh and thank you Son Goku - You are once again the voice of reason amongst such narrow-minded posts.


PS - I say 'once again' because I recall that you replied to a post of mine a few months ago and your reply was the only decent and fair one.

Professor_Fink

Hmm... I can only assume that is a reference to my post.

Well, as you can probably tell by the time stamp, I posted after getting in from the pub, which, in retrospect, was probably a bad idea.

I didn't mean to insult you, and I am quite open to there being physics we don't know about. Basically what I meant to say was that we know enough about nature, now, to put limits on the deviation of current physical theories from how nature truly behaves.

These limits essentially rule out the existance of another force of sufficient strength to be a useful basis for a sense.

Of course other senses are possible, such as seeing different parts of the electromagnetic spectrum, but there isn't really that long a list, because any sense will need to be mediated by the electromagnetic interaction.

This being the case, any other senses would only give us a more intuitive understanding of electromagnetism. The reason I don't think this is particularly useful at this point in the development of physics, is that it is the one force we really understand. We can relativily easily predict what any extra sense could sense, and usually we can build artificial sensors to detect the same phenomena, extending our senses by proxy.

I'm sorry if my original post offended you, I should have been a little more careful with the wording.

JoeB-

Professor_Fink wrote:

Hi Kelter,
2) Sound has very different properties, and is basically a vibration traveling through a material, rather than a field. There is no way anyone could ever have been convinced that the speed of sound is a fundamental limit, since we detect particles which go many times the speed of sound in air (cosmic rays go at close to the speed of light).

Nobody has mentioned yet that the speed of light (or the speed of electromagnetic radiation) is the same when measured in any reference frame... i.e if you are travelling at half the speed of light and you shine a torch forwards you will see it travel away from you at the speed of light and a stationary observer (relative to you) will also measure it travelling at the speed of light... hence the theory of relativity...

This is fundamentally different to how sound waves travel... so we have the doppler effect for sound but not for light... I know there's a red / blue shift etc but that is something different I think (but I'm not sure)...

I used to think it was some major explosion in the mind that allowed Einstein to come up with this idea (of lights constant speed in all reference frames) because it goes against everything we know about the way the world works...
but in writing this reply I realised that without a constant speed of light the Earth would be getting bombarded with light waves of all different speeds as the light sources would be moving relative to us... this could have been tested handily enough...

John G. Cramer
I have posted this link before because the content is so good, it's sure to interest anyone interested in hard science and 'off the wall' ideas.

Cheers
Joe

Kevster

Professor_Fink wrote:

I'm sorry if my original post offended you, I should have been a little more careful with the wording.

Yo, I never thought I'd be coming back to this thread after all this time but here I am. You didn't offend me at all - I was just looking for an argument with someone and it just so happened to be you. The golden rule is to never make a public comment on a BBS/forum or otherwise when in an angry mood because you will oftentimes regret your actions in retrospect.

I made my posts after stressful days at college and in truth I don't think I'm anywhere near your level of knowledge of physics.

aequinoctium

the speed of light is not dependent upon our ability to see light...the visible spectrum of light is only a small portion of the electro-magnetic spectrum!

it is a universal constant!

Fallen Seraph

Kelter wrote:

Guys, Thanks a lot for the answers. They are really good. Well the latter ones anyway.

I guess my point is that it seems wrong to me that a physical constant, such as the maximum speed possible, should be something so convenient as to be something so easily relate to. It really does suggest an intelligence in the organization of it all.

Pi however is a bit scientific. I mean it is a pretty meaningless number. Wouldn't it be a bit more natural phenomenon if the maximum speed possible was 3.14 times the speed of light?

Perhaps a helpful way to think of it is that there is a speed at which massless particles travel in a vacuum, and this is speed is a fastest speed at which anything can travel. We just call it the speed of light because the massless particle we're the most aware of is light. There are other particles which travel at the same speed.

Capt'n Midnight

Kelter wrote:

Well you know the way the speed of light is meant to be the limit for how fast things can go... well what would have happened if the human race were blind? If we had developed by evolution without the ability to see... then would we be unable to have found out about this limit... yeah

The eye has evolved at least 20 times, so it's extemely unlikely we or any ET would be blind. Even if we were we'd most likely use sound to navigate like other mammals (and a few birds) and so be very aware of the speed of sound. Anyway on a sunny day you can feel infra red on your skin so we would not have been unaware of light. Whats the name of the organ that was descended from the "third eye" ?

As a follow on from this... lets say we used sound to "see" for want of a better word, as our main sense. Then would we have decided that it was the limit?

No. Practical proof would have come with the crack of a whip, the tip exceeds the speed of sound. The sound barrier concept for aeroplanes only became popular after bullets had passed the speed of sound. The "thermal thicket" isn't quite so commonly known but it's one of the main reasons most military planes don't go any faster now than the faste ones of 50 years ago.

Finally what if we are blind... like what if there is anouther sense that we don't have? (for example as humans we generally can't sense magnetic fields etc)

somewhere on the interweb there is a link to describe the magneticly sensitive region near the top of your nose.

Aboroginies in Oz claim to be able to smell water. Insects can smell CO2 Fish have a lateral line so can feel the pressure waves in their environment ( like pasive sonar compared to the dolphins one) cat fish have taste buds all over their body so can taste by touch. Moths have antenna that are 1/4 wave tuned to infra red of the heat of the female. Snakes can sense infra red to hunt mice. Bees can see in the ultra violet, and they and ants can detect the polarisation of light, so can tell where the sun is by looking at any part of the sky , (even if cloudy?) Birds can hear sub-sonic sounds, like the sound of waves crashing on the beach, 20 miles away. We have very poor chemo-receptors compared to many animals, dogs can survive being blind in a way we could not because of all the extra clues and an extra pair of leg to stop them falling over when they bump into stuff.

in SciFi there is one story about aliens that could not hear, and so to them we'd be telepathic. Perhaps ET wouldn't be able to see in colour either or wouldn't be able to smell Hydrogen Sulphide or Cyanide. Then again maybe they could smell Carbon Monoxide.

amen

The eye has evolved at least 20 times

really ? from my understanding they now think althought the eye has been implemented 20 eyes the basic building blocks are there in everything and all that has really happened is a greater degree of differentiation

Capt'n Midnight

Well chlorella has an eyespot if you want to find a common un-differentiated ancestor. Just ask any evolutionist how useful a partially developed eye might be

Many biological chemicals are light sensitive especially those in respiration or photosynthesis and so could be considered basic building blocks. Most plants show light dependent movement or growth. Lots of the weirdos from the pre-cambian explosion had eyes but even then they were of many different forms. Our eyes and those of Octupuses are very similar, but we have nerves in front of the rods and cones, they have them behind, an extremely difficult one to explain by evolution but very easy to show by convergent evolution.

But in evolution you can't simply roll back the clock, aquatic reptiles, birds and mammals are still air breathing. Did I see something about turtles having a type of lung in their posterior ?

and I still think scallops have some of the cutest blue eyes.

Professor_Fink

Fallen Seraph,

Actually massless particles always travel at c, vacuum or not. The fact that we observe light to move slower through opticcal media is an effect of the interaction of photons with fields present. Photons don't actually slow down.

Kevster

amen wrote:

really ? from my understanding they now think althought the eye has been implemented 20 eyes the basic building blocks are there in everything and all that has really happened is a greater degree of differentiation

Yes, you're right Amen - I read about this recently too. I think they did an article on it in BBC's Focus magazine. Scientists found that the genes involved in the formation of the eye are actually identical across all/most(?) animals but that it is expressed in different ways... ...or something like that

Kevster.

Kelter

Fallen Seraph wrote:

Perhaps a helpful way to think of it is that there is a speed at which massless particles travel in a vacuum, and this is speed is a fastest speed at which anything can travel. We just call it the speed of light because the massless particle we're the most aware of is light. There are other particles which travel at the same speed.

Good explanation. Very good in fact

JoeB-

JoeBallantine wrote:

so we have the doppler effect for sound but not for light... I know there's a red / blue shift etc but that is something different I think (but I'm not sure)...

Hmmmm, have I got a red face. . It turns out that the red / blue shift is indeed caused by the Doppler effect, I thought it might have been caused by the expansion of the universe or something... (even though that would only have explained a shift in one direction)... sorry

JoeBallantine wrote:

I used to think it was some major explosion in the mind that allowed Einstein to come up with this idea (of lights constant speed in all reference frames) because it goes against everything we know about the way the world works...
but in writing this reply I realised that without a constant speed of light the Earth would be getting bombarded with light waves of all different speeds as the light sources would be moving relative to us... this could have been tested handily enough...

Again I was a bit off. I read 'A Brief History of Time' for the first time the other day after seeing it in a second hand shop... it turns out that Michelson and Morley did that very experiment to measure the speed of light hitting the Earth from different directions in 1887... were they surprised when they got the exact same speed regardless of direction.
It turns out that Einstein was responding to this experiment when he came up with his relativity theory (in 1905)...

Incidentally Hawkings book is very good, I'll have to get his other ones.

Cheers
Joe