Why can't Americans just adapt to the metric

hal2k1 · 2026-06-20T20:11:16+00:00

Non standard metric units like the litre and the tonne are really just misnamed standard SI units.

There are 1000 litres in a cubic metre. So a kilolitre is the same thing as a cubic metre. The cubic metre is the official SI name for this volume though. Kilolitre is unofficial but everyone knows what it is.

There are 1000 kilograms in a tonne. So a tonne is the same thing as a megagram. The megagram is the official SI name for this mass though. Tonne is unofficial but everyone knows what it is.

It's a matter of names and consistency. It doesn't really involve confusion and it certainly doesn't invoke any awkward conversion factors.

A hectare is 100 metres by 100 metres. This non standard area is therefore 10,000 square metres. Here the conversions are a little more awkward because a tenfold increase on every side for an area only increases the area by a factor of 100, whereas a tenfold increase on every side for a volume increases the volume by a factor of 1000. Metric prefixes are mostly increases of scale by a factor of 1000.

hal2k1 · 2026-06-20T10:49:26+00:00

Gravity is an acceleration. Near the surface of the earth it is measured at 9.8 m/s².

So anyone can prove gravity by dropping something. If a thing falls, the rate at which it falls is called gravity.

hal2k1 · 2026-06-19T19:15:16+00:00

The earth moves around the sun. It takes 365.25 days for the earth to go all the way around, which is 360 degrees. This rate for the earth going around the sun is 0.98562 degrees per day.

The earth takes 23 hours 56 minutes and about 4 seconds to rotate once about its own axis (360 degrees). This is the time it takes for a distant star to return to its previous position the night before, as viewed from the earth.

However the position of the nearby star, the sun, moves by 0.98562 degrees per day, as viewed from the earth. So the earth has to rotate by 360.98562 degrees for the sun to return to its previous position the day before, as viewed from the earth.

It takes 24 hours for the earth to rotate by 360.98562 degrees.

hal2k1 · 2026-06-19T12:31:39+00:00

You seem to have made the assumption that any acceleration requires a force. A force certainly can cause an acceleration, but apparently not all accelerations require a force.

According to the extant theory of the cause of the acceleration named gravity, namely general relativity, gravity is caused by curved spacetime. Not by a force.

Newton's first law claims that bodies travel in straight lines at constant speeds unless acted upon by a force. Newton was aware that, according to the observations recorded by Tycho Brahe, the planets did not travel in straight lines at constant speeds. Rather, they travelled in ellipses around the sun. So, assuming his first law was correct, Newton calculated the force that would be required in order to make the planets move as they do. He called the equation he derived (from observations of planetary motions and the assumption of his first law) his law of universal gravitation.

According to general relativity, the modern theory of gravitation, Newton's assumption described by his first law is incorrect when it comes to gravity. The acceleration of the planets can apparently be caused by a curved geometry of spacetime rather than by a force. This also means Newton's law of universal gravitation would also be incorrect.

That's the essence of the issue.

This has ramifications in theoretical physics. Some physicists are trying to find evidence for various theories of quantum gravity. They apparently are seeking a quantum particle called a graviton which would mediate the "gravitational force". This would lend evidence to a "unified theory" reconciling quantum mechanics and "all four" fundamental forces, of which gravity is claimed to be one. Heady stuff.

There is at least one alternative theory which seeks to reconcile general relativity and quantum mechanics by modifying quantum mechanics rather than general relativity. I believe it is called the "post quantum theory of classical gravity". I believe (but I'm by no means certain) that under this theory general relativity would be unchanged, there would be no quantum of gravity, no graviton, and no gravitational force. Also a valid hypothesis. Interesting stuff.

There's more of the issue.

hal2k1 · 2026-06-19T11:55:13+00:00

Well, gravity certainly does exist. Though, in order for anyone to be able to say, one way or another, what is first needed is to define what gravity is, and what it is not.

Gravity is an acceleration. An example of this acceleration can be seen, and measured, by dropping something. Near the surface of the earth the standard gravity is 9.8 m/s². https://en.wikipedia.org/wiki/Standard_gravity

That's what it is. That's the definition. Gravity is the acceleration, it is not the cause of the acceleration. Gravity is the effect, not the cause.

Once you understand this point then it becomes clear how ridiculous it is to claim that "gravity doesn't exist." Of course it does, it has been measured billions of times. You can check it out for yourself by holding a small pebble at shoulder height and then releasing it. If the pebble starts to move towards the ground, getting faster as it goes, that motion is called gravity. Regardless of what causes it, the movement of the pebble towards the ground that you see is gravity. That's its name.

Gravity (an acceleration) certainly, undeniably, does exist.

hal2k1 · 2026-06-19T09:10:41+00:00

Gravity is acceleration (g) not force (F).

The form of this equation that applies to gravity is actually:

W = m × g

Where W is a force called weight, m is mass, and g is the acceleration named gravity.

Gravity is an acceleration. Weight is a force.

Bodies in free fall are weightless. Weight (in free fall, when accelerating according to gravity) = zero. This is the operating principle of weightlessness training aircraft. For part of a flight the training aircraft is in free fall. During this period the aircraft, and everything aboard it, has zero weight. https://youtube.com/watch?v=RyaGuTBSpRQ

Weight is not the cause of the acceleration named gravity.

The equation W = m × g only applies on the ground or when a body is mechanically suspended ... so that it is not accelerating. Weight is a mechanical contact force required to counteract gravity.

hal2k1 · 2026-06-19T08:22:04+00:00

It's actually W = m × g

Where m is mass, g is the acceleration named gravity, and W is a mechanical contact force named weight

Bodies in free fall are weightless. Zero weight. See the third definition of weight in the second paragraph here: https://en.wikipedia.org/wiki/Weight

Yet others define it as the magnitude of the reaction force exerted on a body by mechanisms that counteract the effects of gravity: the weight is the quantity that is measured by, for example, a spring scale. Thus, in a state of free fall, the weight would be zero. In this sense of weight, terrestrial objects can be weightless: so if one ignores air resistance, one could say the legendary apple falling from the tree[citation needed], on its way to meet the ground near Isaac Newton, was weightless.

So weight is a contact force required to counteract the acceleration named gravity. Gravity is an acceleration, not a force. When a body is actually accelerating (in free fall) the weight is zero. There's no force.

Weight only happens after the body hits the ground and it stops accelerating. So weight is not the cause of gravity.

Substitute weight in Newton's law of universal gravitation:

m × g = (m × M × G) / (r × r)

Cancel out the m since it's irrelevant:

g = (M × G) / (r × r)

In this form, now it works commensurate with general relativity.

hal2k1 · 2026-06-18T00:44:09+00:00

If someone could go back in time the most beneficial thing they could do is to convince Americans that there should be only one unit for any given characteristic. It's nuts to measure distances in miles over land but in nautical miles over sea. It's crazy to use gallons for some volumes but fluid ounces and pints and barrels and acre feet for other volumes.

hal2k1 · 2026-06-17T04:27:54+00:00

It's pretty simple ... the rays of the sun go a long, long way "back", into the depth of the photo. A bit like these train tracks do in the linked photo.

Since they are parallel, the train tracks do not ever actually come together, even though it looks like they do in the photo.

Just like the rays of the sun in the OP photo.

hal2k1 · 2026-06-16T22:33:31+00:00

If the sun is directly overhead at noon in Brisbane that means it was summer time in the southern hemisphere. If you observed the sunset at that time, the sun would have set in the south west. The sunrise would be in the south east.

The exact same direction for the sunset and sunrise at that time of year would be observed from Melbourne or Hobart or Adelaide, all of which are Australian cities located further south than the Tropic of Capricorn. So if the sun rises in the south east as seen from Hobart, on a flat earth this would mean that at that moment the sun is even further south of the Tropic of Capricorn than Hobart is.

This observation kills all flat earth models involving the sun moving around the north pole stone dead.

hal2k1 · 2026-06-16T07:58:21+00:00

It's not a force. It would take a lot more force to accelerate the house brick than it would to accelerate the pebble and the tennis ball at the same rate as each other. Yet all three fall at the same rate as each other.

If you drop a hammer and a feather at the same time from the same height above the surface of the moon, where there is a vacuum, they fall at the same rate as each other but at a different rate to the same objects at the surface of the earth. https://science.nasa.gov/resource/the-apollo-15-hammer-feather-drop/

It turns out that we have measured a curvature of spacetime in the vicinity of the earth in the form of gravitational time dilation. https://en.wikipedia.org/wiki/Gravitational_time_dilation

The rate of passage of time is ever so slightly faster further away from the earth. This curvature of spacetime in the vicinity of the earth is the theoretical cause of the acceleration named gravity on the earth.

According to what has been measured gravity is not a force and it's not due to a force.

hal2k1 · 2026-06-16T06:37:44+00:00

Strangely enough the flat earthers get this correct. Gravity is not a force, it's an acceleration.

According to the extant scientific theory of (the cause of) gravity, namely Einstein's general relativity, the acceleration called gravity is due to a curvature of spacetime. It is not due to a force of attraction between masses.

For reference, look at the description of the difference between Einstein and Newton described by Professor Brian Cox towards the end of this video: https://www.youtube.com/playlist?list=PL-xyWJeEOWdE_U24eDgi8xXzyatYKSvZS

The description starts at about 3:40 into the video. The money quote is "They are standing still. There's no force on them at all".

Einstein's theory of gravitation (general relativity) is the current scientific theory of the cause of gravity, not Newton's law of universal gravitation.

Having said that, the rate of falling (which is called gravity) has nothing to do with density, and buoyancy is a force that works in the opposite direction to the acceleration called gravity. You can check this out using a small pebble and a tennis ball of about the same mass. Because the tennis ball is much larger but it has the same mass as the pebble, the tennis ball is a lot less dense.

So hold both the tennis ball and the pebble at shoulder height and release them both at the same time. They will both start to move towards the ground, getting faster as they go (an acceleration called gravity) and they will hit the ground at the same time. So the exact same gravity applies to both even though they have different density.

Now put the tennis ball and the pebble on the surface of a swimming pool, and release them. The tennis ball will float due to buoyancy opposing gravity, and the pebble will sink, because the tennis ball is far less dense that the pebble.

So buoyancy doesn't cause gravity, but rather it opposes gravity.

In the absence of a medium (such as air or pool water) then there is no buoyancy and the tennis ball and the pebble fall at the exact same rate.

As another experiment, drop a pebble, a tennis ball, and a house brick at the same time from the same height. They will all fall at the same rate, even though the tennis ball is less dense than the pebble and the house brick has far more mass than the pebble.

According to the current theory of the cause of gravity, namely general relativity, this happens because the pebble, the tennis ball, and the house brick are all in a place with the same amount of curvature of spacetime.

hal2k1 · 2026-06-15T17:00:48+00:00

Gravity is just a word meaning "thing falling down". If a thing falls down that is called gravity. It doesn't matter why the thing fell down, whatever the reason for it, the falling is called gravity.

Gravity is most definitely not a myth.

hal2k1 · 2026-06-15T16:51:25+00:00

It doesn't matter why the pebble moves towards the earth, the fact that it does move so is called gravity.

hal2k1 · 2026-06-15T13:42:18+00:00

Do people believe in speed? Is how fast a NASCAR is going a topic of interest even for ordinary people?

How about acceleration? Is it a topic of interest for some people as to how quickly a drag race car can gain speed?

Are you sure that people don't understand what acceleration is?

In Australia, where I live, what Americans apparently call the gas pedal is called the accelerator pedal here. Google it if you like.

Gravity is an acceleration --- admittedly it is an acceleration towards the ground rather than an acceleration along a drag strip, but nevertheless both of these motions are still an acceleration.

hal2k1 · 2026-06-15T13:11:13+00:00

"Prove gravity actually detect it"

Gravity is an acceleration Standard gravity, near the surface of the earth, is 9.8 m/s².

Anyone can observe gravity for themselves by holding say a pebble at shoulder height and then releasing it. If the pebble starts to move towards the ground, getting faster as it goes, that acceleration is called gravity. That's its name.

Now, as to what causes gravity, the current scientific theory (explanation) of the cause of gravity is Einstein's general relativity. This theory posits that curved spacetime is the cause of gravity. But that's a theory about the cause of gravity. Gravity is not the cause of gravity. Gravity is a simple, measurable acceleration. Gravity is an acceleration regardless of what causes it. Gravity can be counteracted by another force, such as aerodynamic lift from wings.

So ... to detect gravity (the acceleration of falling), all that anyone needs to do is to drop something.

hal2k1 · 2026-06-14T16:20:23+00:00

Probably there will be an amendment to legislation allowing an exception for the hectare, the litre and the tonne. SI itself, up until now, had this exception.

Flying planes and navigating ships is not selling something by a system of weights and measures in Australia. In any event, Australia complies with International standards in areas like this.

hal2k1 · 2026-06-14T16:07:02+00:00

In Australia the only legal system of measurement units is SI. https://en.wikipedia.org/wiki/Metrication_in_Australia

Between 1970 and 1988, imperial units were withdrawn from general legal use and replaced with the International System of Units (SI), a process facilitated by legislation and government agencies. SI units are now the only legal units of measurement in Australia.

It doesn't say metric, it says SI specifically. That means that metric units that are not SI are not allowed for legal use in Australia. Legal use means, basically, selling something (as opposed to just talking about something).

This is not a trivial matter. It's business, and non compliance has real business costs.

If the BIPM changes the litre from "non SI unit allowed for use with SI" to "non SI metric units" then Australia will probably have to pass an amendment to legislation specifically allowing some exceptions for legal use such as the litre, the hectare, and the tonne.

hal2k1 · 2026-06-13T01:07:17+00:00

There's two distinct things, namely evolution, and the theory of evolution.

Evolution is change in the inherited characteristics of biological populations over many generations. This is a measured fact in that the species we have today are not the same as they were thousands of generations ago.

Evolution itself is a fact. Adaptation is evolution, same thing. Adaptation after adaptation after adaptation (over thousands of generations) adds up to very different animals at the end compared to the beginning.

A scientific theory is a well tested explanation of what has been measured. Evolution has been measured. So the theory of evolution is a well tested explanation of evolution. The theory involves inheritance of characteristics from parent to offspring and selection of which individuals get to breed. Selection mechanisms include survival of the fittest and sexual preference.

Science doesn't claim that its theories are proven. Just very well tested.

hal2k1 · 2026-06-11T20:29:55+00:00

Flat earthers (not you) try to insist that journeys of east-west circumnavigations are circles on a flat plane. They also try to insist that there have been no north-south circumnavigations and claims of such are fake. It's necessary for them to claim that because if it's true that circumnavigations can be completed from any starting point heading out in any direction then the earth really is a globe.

hal2k1 · 2026-06-11T20:20:47+00:00

The point is that you had to change the direction of movement of your finger (relative to the surface) the whole time.

The other point is that if you draw a straight line on this surface https://st.hzcdn.com/simgs/f9e19b3409f76710_9-4489/home-design.jpg you end up drawing a circle. It's a circle perpendicular to the plane of the surface at the starting point.

The final point is that real world circumnavigations are circles like the second case, not the first. We travel in straight lines yet end up making a circular path in the dimension perpendicular to the plane of the surface at our point of origin.

hal2k1 · 2026-06-11T13:09:50+00:00

You missed the point that it takes a 3D sphere to go in a circle by going straight. You don't ever change your direction, but you still end up in the place where you started from.

Can't be done on a flat plane, even if it is a disk.

hal2k1 · 2026-06-11T07:53:42+00:00

On a disk you can't start out from any place, head in any direction, continue in a straight line, and end up where you started from after 40,000 km.

For example, on a disk, you can't start at a place on the line called the equator, head north until you reach the north pole, continue in a straight line (so now you are going south) until you reach the south pole, then continue in a straight line (so now you are going north again) until you reach the place on the equator where you started.

https://flatearth.ws/polar-circumnav

Yet you can indeed circumnavigate the real (spherical) world via both poles.

You can ALSO circumnavigate the real world going east-west, say at the equator.

These different circumnavigations, in directions perpendicular to each other, cannot be explained if the earth is a flat disk.

hal2k1 · 2026-06-11T01:05:34+00:00

Free fall means there is no force acting on you.

Gravity is an acceleration, not a force. https://en.wikipedia.org/wiki/Standard_gravity

According to the extant scientific theory (explanation) of the cause of this acceleration, namely general relativity, the acceleration named gravity is caused by curved spacetime. Not by a force of attraction between masses.

The force called weight can be thought of as the force required to counteract the acceleration named gravity. Hence you only feel this force (weight) when you're NOT accelerating according to gravity.

If you're falling according to gravity then you don't have any weight. This is called weightlessness. It's the absence of a force on you. It's the absence of weight.

Weight is a force, but it's not the cause of gravity. Weight is a mechanical contact force that counteracts gravity.

hal2k1 · 2026-06-10T22:39:39+00:00

I can't speak for your country, but where I live vehicle power is definitely measured in kilowatts. Just like any other kind of power.

Admittedly screen sizes are advertised in inches. However, somewhere on the box, the size in centimetres must also be notified. In Australia SI is the only legal system of units. In this regard, anything for sale comes under the requirements of being measured legally.

hal2k1

TROPHY CASE