array9

Oil is lots of ball bearings?

I was wondering what a correct analogy for lubricating oil was?

Clearly ball bearings between two parallel plates acts as a lubricant, provided there is a 'not full' single layer, and they are all the same size.  Everything rolls around happily and does not crash into each other.  Cylinders are fine if the movement is basically in one direction ( as per pyramid building.)  Fundamentally no two surfaces rub in different directions.

But I go a bit hazy if there are many layers of balls between the surfaces.    There must be rubbing of surfaces travelling in different directions.  I would guess this is not so good, although each ball might not have to travel round very much.

I guess the ultimate result is like a ship travelling through water.

Maybe what one wants is a mixture of platelets and ball bearings, so that you have multiple layers of flat surfaces each lubricated with a single layer of balls.  Any one of these layers could provide the full motion.

I guess the balls have to be sufficiently large to avoid electrical forces between the plates dominating, but could this actually work in a nanotechnological sense.  Graphene and buckyballs?

Anyway, I am not sure how real lubricating oil fits into this analogy.  Maybe it is only trying to neutralise the electrical forces between plates and not much else.  Maybe filling in the rough surface a little?

Perhaps we will see people putting more and more funny nanoparticles into the traditional oil.

martinW

Why was big bang not a black hole?

The one thing about the big bang that has always confused me is why was it not originally a black hole?

Is this because a black hole has to exist inside an existing space?

Is it just true?  And we are still in it?

Or do we fudge the issue with inflation?  to get outside the barrier?

Or is a Universe by definition a black hole, there being no outside?

So the secondary questions are going to be something like

- can you have a black hole inside a black hole?

where do I find some thinking on this?

MartinW

Best way to send a message is by molecule



Sending a message electronically or transmitting it over the air waves has to be an inefficient process, subject to noise and coherence problems.  You have to send it effectively multiple times.

What might be the most efficient way of sending it?  I am reminded of the 'netflix founders' story about a university question about which had more bandwidth,  a cable or a lorryload of dvds?

I would suggest that a carefully crafted molecule would do nicely.  It could be stable, compact, error checked, encrypted, etc, and could be sent surprisingly quickly over space.

Now the building and reading are not currently fast.  Replication would be fine ( if based on say dna).

Somehow I think that it might be a little impractical, even though the natural extension of the written letter.  Except perhaps for alien contact, where firing molecules out into space seems rather a neat way of doing it.

And if these molecules could self replicate, so much the better.

Perhaps Fred Hoyles idea of seeding the earth from space is actually the right idea.  Indeed if mankind wants to leave the planet, then this is what we should be doing again in the opposite direction.

MartinW.

Swinging your arm reduces foot impact


Some random thoughts.

Swinging the arms as you walk reduces the vertical movement of your centre of gravity.  So there is less impact on the feet as your feet hit the ground.  Just assuming that they swing freely.

But if you apply some force at the top of the swing, then you can add to this effect.

Using a trekking pole allows you to spread any impact, provided your timing and position is right.

As you walk, you have your arms outstretched for a slow beat, but running you bend them up and then out to increase frequency of the pendulum effect ( and resonance).

The arm forced swinging also controls torque and angular momentum, and explains why it is so difficult to have left arm and left leg, which would work just as well for vertical movements.

Though this depends on whether the left foot lands to the left of the right foot. You would expect a running gait to reduce this spread between where the feet land.

Bruce Tullow ( British athlete in the 1960s ?) used to minimise how high his returning foot was, which always seemed strange. But when you walk you don't lift your leg much at all.  Again a frequency effect.  To speed up the natural swing and reduce the angular inertia, lifting the leg must have benefits.

This all seems difficult to optimise, but evolution seems to have done a good job.  The only aids used  by man, until recently, are Lycra (potential energy store), soles (ditto), and zimmers/walking sticks (band aids).  The newer improvements are wheels, ski sticks and leg breaks [ used for powering batteries, but can be seen as passive breaking, rather than active breaking.  I suppose this is just a more active form of a potential energy store].  Four legged animals have known about ski sticks for years.  Kangaroos must use potential energy systems surely.

But where are the equivalents of flying fish, gliding squirrels, spider lines, monkey arm swings?

MartinW