Physics Question: Are Eyeglasses Mechanical?

[jbarter]

Science confuses me. I think I'll have a nice lie down in a darkened political thread.

[Jeff Stallard]

http://www.britannica.com/ebc/article?t ... achine&ct=

which I submit is a more appropriate definition of 'machine' than the one found on the likes of hyperdictionary.com

That link says, "Device that amplifies or replaces human or animal effort to accomplish a physical task." A lens amplifies human effort to accomplish the physical act of seeing. Bada-boom bada-bing!!

[GaryKelly]

However, the difference between a machine and a tool is that a machine must operate fairly independently.

Where does the "fairly independently" come from? A lever is a machine, so is a pulley; there's nothing independent about them, they need something (usually *someone*) to operate them in order to fulfil the requirement of work.

And not to get nitpicky, you'll note that light doesn't appear in the Encyclopaedia Britannica definition. Probably because the necessary components of "force and motion" don't apply to light. Your argument in respect of 'vector' is specious, since light has no mass.

[GaryKelly]

Science confuses me. I think I'll have a nice lie down in a darkened political thread.

At least we quoted our sources, you liberal pinko! Oh wait, sorry JB, it's Amar who's the pinko 'round here

[jbarter]

Science confuses me. I think I'll have a nice lie down in a darkened political thread.

At least we quoted our sources, you liberal pinko! Oh wait, sorry JB, it's Amar who's the pinko 'round here

You woke me up to tell me that?

[Jeff Stallard]

Where does the "fairly independently" come from? A lever is a machine, so is a pulley; there's nothing independent about them, they need something (usually *someone*) to operate them in order to fulfil the requirement of work.

I was going by another definition I found on the Web that was differentiating between machines and tools. I suppose it's moot in this case, so I'll just drop the "fairly independent" idea altogether.

And not to get nitpicky, you'll note that light doesn't appear in the Encyclopaedia Britannica definition.

Yes, and that disturbs me.

Your argument in respect of 'vector' is specious, since light has no mass.

A vector quantity defines velocity and direction, not mass. True, mass (or inertia rather) factors when calculating vector changes, but that's not the point. The point is that vector forces are very Neutonian, and vectors are highly relevent when discussing light.

[jbarter]

A vector quantity defines velocity and direction, not mass. True, mass (or inertia rather) factors when calculating vector changes, but that's not the point. The point is that vector forces are very Neutonian, and vectors are highly relevent when discussing light.

I think I'll take up the pipes. It'll be easier to understand.

[GaryKelly]

A vector quantity defines velocity and direction, not mass. True, mass (or inertia rather) factors when calculating vector changes, but that's not the point. The point is that vector forces are very Neutonian, and vectors are highly relevent when discussing light.

But light is not Newtonian, it's relativistic. If you're going to insist that changes in vector count in the definition of 'machine', then you're saying a mirror is a machine, or any polished surface, or indeed a puddle of water, all of which modify a beam of light's vector.

Heh. I woke up JB!!

[Tyler]

Good night, of all the topics argued over here, this has got to be the silliest!
oh, by the way...a lever only becomes a machine when it is or has a pivot point or axis to accomplish work. But this opens up the argument of "which came first, the lever or the crowbar?"

[amar]

A lens DOES do something. It alters the vector of light energy. It doesn't have to have cogs, chains, and bearings to be a machine. Anything that modifies energy to assist in the performance of tasks is a machine.

yeah, but a lense just sits there and lets things happen. not actively doing anything at all. i mean, is the newspaper on my table add: a machine because it reflects the light from the sun to my eyes?

[amar]

I refer you to my previous answer, and expand upon it by suggestion that a lens doesn't modify energy. Even if the lens were completely lossless, then energy in=energy out, and therefore no modification has occured at all.

Amar, a crowbar has no moving parts, but since it operates on the principle of a lever, it can be classified as a machine (since it performs work).

but only if the crowbar is made to work, by a person, the person is the machine, the crowbar is just a piece of metal.

[Tyler]

A lens DOES do something. It alters the vector of light energy. It doesn't have to have cogs, chains, and bearings to be a machine. Anything that modifies energy to assist in the performance of tasks is a machine.

yeah, but a lense just sits there and lets things happen. not actively doing anything at all. i mean, is the newspaper on my table because it reflects the light from the sun to my eyes?

interesting thought!
So, a stinky guy walks into a bar and by his very presence modifies the air in the room.....

[jbarter]

"which came first, the lever or the crowbar?"

and why did the lever cross the road?

[amar]

http://www.britannica.com/ebc/article?t ... achine&ct=

which I submit is a more appropriate definition of 'machine' than the one found on the likes of hyperdictionary.com

That link says, "Device that amplifies or replaces human or animal effort to accomplish a physical task." A lens amplifies human effort to accomplish the physical act of seeing. Bada-boom bada-bing!!

but it also says: A machine may be further defined as a device consisting of two or more parts that transmit or modify force and motion in order to do work.

[jbarter]

Dale, I demand you start a separate science forum so the rest of us can get some sleep. These scientific wallahs are trying to make us think.