# which is faster, php or javascript? - Page 6

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## Re: which is faster, php or javascript?

On Fri, 29 Jan 2010 09:14:45 +0000, Geoff Berrow wrote:

If you look closely at the original bit in the quoted part, you'll see
that that's the *goal*.

You don't want the dishes tangent to the Earth, you want them tangent to
the source you're observing.

Never can tell when that phase difference will tell you something....

--
People who are willing to rely on the government to keep them safe are
pretty much standing on Darwin's mat, pounding on the door, screaming,
'Take me, take me!'
-- Carl Jacobs in the Monastery

## Re: which is faster, php or javascript?

On 28/01/2010 12:30, matt wrote:

OK - I see what you're getting at. For the examples we have all been
looking at, say a kg of iron vs. a kg of feathers, the altitude issue,
while valid, is much smaller. Certainly, if your iron rod was 400ft long
or better still a mile long :-) then at whatever orientation it
displaces the same volume, but a different weight of air. However, you
then have to take into account that parts of the iron rod are further
from the centre of the earth as you point out below.

And, it gets worse :-) as there is also the fact that the top of the
vertical mile-long rod will be spinning round the centre of the earth
faster than the bottom - and so there will be an outward force due to
the centripetal force (you weigh less at the equator than the poles for
that reason - not because you're a mile high but that you are spinning
faster).

I think the best way to grasp the principles is to keep the example
simple and just take small amounts of different materials at the same
altitude. The same mass of iron and feathers displace different amounts
of air, quite simply. The fact that the feathers may contain air won't
affect that if the air is at the same pressure as the outside.

(I'm not convinced, anyway, that the tubes in feathers are airtight
(need a biologist here), because that might cause problems for
high-flying birds - there are some birds whose migration path takes them
over the Himalayas.)

Feathers only seem "light" because they form a low-density mass with a
large surface area. A feather falls slowly because of its large surface
area which gives it a low terminal velocity. If you compress all the air
out, including that inside the feather shafts, then you have a solid
mass of keratin which is just another lowish-density substance. But that
compressed mass will displace just as much air as the original feathers.

If you get into a full bath, the water will overflow to allow you to,
however gently you do it. In a less full bath, the resulting water level
will be higher - you've moved some water "uphill". Gravity is trying to
pull it downhill again - which is the origin of the upwards force on you.

Yes, I'm sorry about that. Funnily enough, my first reaction was ruder
but then I decided that was inappropriate, but it still came out hasher
than I intended.

--
Tim

"That excessive bail ought not to be required, nor excessive fines
imposed, nor cruel and unusual punishments inflicted"

Bill of Rights 1689

## Re: which is faster, php or javascript?

That answer might be true for some other reasons like gravity distances
and centrifugal forces.

However the fact that there is less air 400ft up only affects the air
pressure. The air pressure is a linear function of height, or rather
depth. The difference in air pressure between the upper side and the lower
side of the rod only depends upon the difference in height of the upper
side and the lower side. This difference becomes a constant if you are
moving the rod up and down within the atmosphere.

Now if the rod is standing the difference is big but the areas affected by
the pressure is small. If the rod is laying the difference is small but
the area is big. If you multiply the difference in pressure with the area
affected you will find that it becomes a constant. Simple multiplication
might not be possible for a horizontal round rod, you might have to
integrate the function of pressure over the horizontal area, but still it
will be a constant.

You could also think of it this way: What would happen if you cut the rod
into two halfes and moved the rods to different heights? As long as we are
only concerned about air pressure their weights will be the same and the
sum of the halves weights will equal the weight of the entire rod. This is
also true if one rod is placed in a horisontal position.

However if we start thinking about gravity distances and centrifugal
forces the weight will be affected by the height and the position on earth.

regards Henrik
--
hc3(at)poolhem.se Examples of addresses which go to spammers:
root@localhost postmaster@localhost

## Re: which is faster, php or javascript?

On 28/01/2010 22:56, Henrik Carlqvist wrote:

Air pressure is not a linear function of height, it's probably
exponential. And this whole business is not to do with the pressure
difference between the upper and lower sides.

--
Tim

"That excessive bail ought not to be required, nor excessive fines
imposed, nor cruel and unusual punishments inflicted"

Bill of Rights 1689

## Re: which is faster, php or javascript?

Whoops, you are right, the barometric formula is not a linear function. My
linear approach only applies to liquids.

pressure forces and pressure integration in air.

The difference in pressure is part of the explanation why two different
materials with equal mass has different weights because of different
density and volume.

regards Henrik
--
hc3(at)poolhem.se Examples of addresses which go to spammers:
root@localhost postmaster@localhost

## Re: which is faster, php or javascript?

It's an incomplete question, I'll grant that, but nonsense?  If you
assume you have the same amount of oil and water *by weight* the
answer is different then if you assume you have the same amount of oil
and water *by volume*.  And personally, it seems to me that volume is
implied, since the question's kinda pointless if you know the weights

I mean, you can fill in the blanks any way you like.  eg.

"Which is heavier, [100L] oil or [100L] water?"

...or...

"Which is heavier, [100 newtons] oil or [100 newtons] water?"

## Re: which is faster, php or javascript?

Perhaps neither? ... try http://rubyonrails.org server-side.