The speed of an object on the equator of the earth

robinson · Post by **robinson** » Tue Oct 13, 2020 8:35 am

This is an old one. It never goes well, because it makes you have to think, and that is fucking anethama, especially if you already dislike the person posing the conundrum.

It relates to the relativity shit that has raised its ugly head elsewhere, but hey, if you are always here posting and reading this shit, you already know that.

Quick summary: An object on the equator is said to be "moving" at around 1037 mph because the earth rotates once a day and the circumference is about 24,901 miles, and yes the reason the math works out so well is because the 24 hours is based on the complete revolution of the planet, herp derp, but let's make it simple and say 1000 mph

Here's a source so you don't try and impeach what I just wrote

Thus, the surface of the earth at the equator moves at a speed of 460 meters per second--or roughly 1,000 miles per hour.

https://www.scientificamerican.com/arti ... per%20hour

No, that is not true, in fact it is

Complete rubbish

In other words, it is garbage, worthless, and it s complete in it's worthlessness

I realized this quite simply by trying to place a camera in a location to show this. I use astronomy software, which is really fucking cool as shit, and to make a movie (animation really) of anything, you simply have to pick a location for the camera. You can't avoid this, the software has to know where your virtual location is in order to render anything.

And before the pedant shows up, Speed is the rate of motion, or equivalently the rate of change of distance.

Speed is a scalar quantity with dimensions length/time; the equivalent vector quantity to speed is velocity. Speed is measured in the same physical units of measurement as velocity, but does not contain the element of direction that velocity has. Speed is thus the magnitude component of velocity.

To say you are "moving east at 1000 mph" is a velocity measurement, but to have such a measurement, you have to choose a reference point. There is no point that you can choose to get a velocity of 1000 mph eastward, this is due to the laws of physics, as well as the acceleration of a spinning point.

The only possible point to choose would be a rocket or airplane flying 1000 mph west from your location, from which one could say you are moving eastward at that velocity, except it is a curving motion, so the velocity changes rapidly. (acceleration)

Which is why the speed of an object on the equator wouldn't be 1000 mph, but a rapidly changing velocity, until the rocket or airplane reached the opposite side if the earth, at which point it would reverse.

There is quite literally no other place to put a camera, especially to measure a 1000 mph speed.

So no, an object on the equator is not moving at 1000 mph. In fact, it isn't moving at all. Unless your point you measure it from is moving, but even then, you never get a 1000 mph measurement of speed. It's not physically possible.

More to come ...

Anaxagoras · Post by **Anaxagoras** » Tue Oct 13, 2020 9:17 am

And your point is?

The earth spins relative to the rest of the universe.

We also know this indirectly due to the Coriolis effect.

Anaxagoras · Post by **Anaxagoras** » Tue Oct 13, 2020 9:22 am

robinson · Post by **robinson** » Tue Oct 13, 2020 11:27 am

My point, which is sharp and unmistakable, is that the speed of an object on the equator is not 1000 mph, much less "to the east", both of which are official claims/explaining from the experts and smarty pants scientists.

It's just like with the tides, or the heating of re-entry from orbit, where experts and official sources have all these explainings and reasons, which are complete rubbish.

Trying to wrench their minds right is like talking to a brick wall.

robinson · Post by **robinson** » Tue Oct 13, 2020 11:31 am

Now of course an ivory tower super intellectual at-the-top-of-the-food-chain scientist is one thing, but even ordinary skeptics and physics oriented peoples have a real problem with understanding relatively simple things, and why the consensus is wrong. And of course global warming, the real and most important danger facing all mankind.

sparks · Post by **sparks** » Tue Oct 13, 2020 6:18 pm

What a fucking idiot.

robinson · Post by **robinson** » Tue Oct 13, 2020 6:59 pm

Since motion is relative, we measure speed and velocity from a reference point. Usually we use the solid ground we are on as the point. But with radar and lasers and cameras we can also measure speed from a moving object, and I am thinking of Trooper Mathews who has a very effective camera/radar system in his Highway Patrol vehicle. Damn you Trooper Mathews, damn you to hell!

But be it speed, or velocity, a point on the equator is never moving at 1000 mph, there is not even a reference point possible to get that figure.

Obviously there is movement, and rotation, only a complete moron would think this is an argument against that.

To realize the practical implications, the original question was about ""if I am at latitude 40 degrees north what would be my speed?" (the answer is to multiply the cosine of the degree latitude times the speed of 1,037.5646.) ... so 40 degrees: 794.80665 mph

But is the earth really moving at that speed? NASA and all the smart people say it is.
https://image.gsfc.nasa.gov/poetry/ask/a10840.html

Now speed is the rate at which an object covers distance. The average speed is the distance (a scalar quantity) per time ratio. Speed is ignorant of direction.

And velocity is a vector quantity; it is direction-aware. Velocity is the rate at which the position changes. The average velocity is the displacement or position change (a vector quantity) per time ratio.

OK but displacement from where? What is the point you can measure this amazing speed/velocity of the earth?

There isn't one. Saying there is would be complete rubbish.

If you think there is, what is it?

robinson · Post by **robinson** » Tue Oct 13, 2020 7:01 pm

You get no points for being an insulting pussbag, or refusing to answer because the question is too dumb for words.

Moe · Post by **Moe** » Tue Oct 13, 2020 10:55 pm

We ain't gettin' noplace fast!

robinson · Post by **robinson** » Tue Oct 13, 2020 11:43 pm

Evasion noted

robinson · Post by **robinson** » Tue Oct 13, 2020 11:56 pm

I'm quite willing to change my POV on this. Just tell me where to put the camera, that shows a 1000 mph speed, or velocity.

Anaxagoras · Post by **Anaxagoras** » Tue Oct 13, 2020 11:58 pm

robinson wrote: ↑Tue Oct 13, 2020 11:56 pm I'm quite willing to change my POV on this. Just tell me where to put the camera, that shows a 1000 mph speed, or velocity.

How about the north pole or the south pole?

robinson · Post by **robinson** » Wed Oct 14, 2020 12:06 am

Shows no movement at all.

Hotarubi · Post by **Hotarubi** » Wed Oct 14, 2020 12:36 am

robinson wrote: ↑Wed Oct 14, 2020 12:06 am Shows no movement at all.

Wrong.

Polar motion.

You lose.

Anaxagoras · Post by **Anaxagoras** » Wed Oct 14, 2020 1:13 am

robinson wrote: ↑Wed Oct 14, 2020 12:06 am Shows no movement at all.

An experiment:

If you stand up straight, and stretch both arms out straight and horizontal, and spin around, are the tips of your fingers moving at a different velocity than your head?

robinson · Post by **robinson** » Wed Oct 14, 2020 3:53 am

Here's the software that allows you (or anyone else) to simply make an animation illustrating the problem.

https://celestia.space/download.html

Anaxagoras · Post by **Anaxagoras** » Wed Oct 14, 2020 4:39 am

Are you suggesting that the earth doesn't spin on its axis?

robinson · Post by **robinson** » Wed Oct 14, 2020 4:44 am

Using the example of your own body, what direction is your hand moving? Let’s say it is moving at 5 miles an hour, based on the time and distance, could you say it is moving at 5 mph to the East? West?

Remember that is the claim about an object on the equator, that it is moving East at 1000 mph

Which is simply not true

robinson · Post by **robinson** » Wed Oct 14, 2020 4:46 am

The problem with the hand also explains why from your point of view, it’s not moving at all

The distance from you eye to the hand stays exactly the same

Yet obviously there is movement

robinson · Post by **robinson** » Wed Oct 14, 2020 4:49 am

Let’s make it even easier

Instead of you spinning, just hold out you hand over you head, and stand on the equator

Now you can say your hand is moving at 1000 mph

robinson · Post by **robinson** » Wed Oct 14, 2020 4:50 am

Climb a tall mountain and now your hand is moving even faster!

Looking down at another person, several miles below, you can say your hand is moving faster than their hand

Hell, even at sea level your hand is moving faster than the speed of sound! It’s actually supersonic!

Anaxagoras · Post by **Anaxagoras** » Wed Oct 14, 2020 5:12 am

It's not moving to the east, because east is only a direction relative to the surface of the earth, which is a curved surface, but it is moving in a circle around the axis of the earth.

ceptimus · Post by **ceptimus** » Wed Oct 14, 2020 5:32 am

Put the camera on the moon, looking at Earth so that north is up. The camera sees the Earth's equator moving right at 1000 mph at the centre, coming towards the camera on the left hand limb and going away from the camera on the right.

If you're concerned about the velocity due to spin, try working out how fast the whole Earth has to go to get around the sun each year. From memory it's about 85,000 mph.

...and then the whole solar system is orbiting around the Milky Way even faster than that, and our whole galaxy is moving yet faster than that relative to other nearby galaxies...

Rob Lister · Post by **Rob Lister** » Wed Oct 14, 2020 7:15 pm

You guys are wasting your time.

Hotarubi · Post by **Hotarubi** » Wed Oct 14, 2020 7:31 pm

Rob Lister wrote: ↑Wed Oct 14, 2020 7:15 pm You guys are wasting your time.

Correct. Thread needs graphs.

robinson · Post by **robinson** » Thu Oct 15, 2020 3:26 am

ceptimus wrote: ↑Wed Oct 14, 2020 5:32 am Put the camera on the moon, looking at Earth so that north is up. The camera sees the Earth's equator moving

That was my first placement of the camera, which showed that an object on the equator, from the moons POV, isn’t moving East at 1000 mph

But because the moon is moving, it alters the total 24 hour distance as well

Also the moon is not usually over the equator, so that also changes things

But in any case, you don’t get a 1000 mph speed using the moon as the POV

ceptimus · Post by **ceptimus** » Thu Oct 15, 2020 4:02 am

The moon takes about 28 days to orbit so reduces the apparent equator speed by less than 4%. This actually makes the speed closer to 1,000mph, because it's 1,037 mph from more 'stationary' positions such as the sun-earth Lagrange points.

ceptimus · Post by **ceptimus** » Thu Oct 15, 2020 1:00 pm

Just multiply the equator speed by the cosine of the latitude: cos(45) = sqrt(2)/2, so the speed at that latitude = 1,037 * sqrt(2)/2 = 733 mph.

robinson · Post by **robinson** » Thu Oct 15, 2020 4:52 pm

Anaxagoras wrote: ↑Wed Oct 14, 2020 5:12 am It's not moving to the east, because east is only a direction relative to the surface of the earth, which is a curved surface, but it is moving in a circle around the axis of the earth.

I see you are on board with the first thing NASA has wrong

Now about that 1000 mph thing

robinson · Post by **robinson** » Thu Oct 15, 2020 4:54 pm

To save time, there is only one POV that allows a 1000 mph measurement, but it is a moving camera position that has incredibly complicated motion, not actually possible in the real world

It also only works for a very limited time frame

Pyrrho · Post by **Pyrrho** » Thu Oct 15, 2020 7:09 pm

https://media.giphy.com/media/3YHzWhog1 ... /giphy.gif

robinson · Post by **robinson** » Thu Oct 15, 2020 9:31 pm

What speed is the camera?

robinson · Post by **robinson** » Thu Oct 15, 2020 9:37 pm

The real obstacle is, of course, we are used to measuring speed or velocity in reference to the unmoving ground.

If a supersonic aircraft was doing 1000 mph, staying directly over the equator, heading East, nobody would say it was doing 2000 mph heading East

Or if going west, not moving at all. But if we accept that an object on the equator is going 1000 mph heading East, that is exactly the facts of the matter. So our unmoving aircraft headed west at 1000 mph is not moving, in relation to the planet. But of course that isn’t true

robinson · Post by **robinson** » Thu Oct 15, 2020 9:40 pm

A satellite in a much higher altitude, at just the right speed, over the equator, would be like the camera in the animation above. But the last thing anybody would say, is that it is standing still in relation to the planet. It would be going very very fast, in regards to it’s movement in a very large orbit.

The software I linked to shows just how fast

Anaxagoras · Post by **Anaxagoras** » Thu Oct 15, 2020 11:11 pm

Do you think the earth spins or not? Usually we measure the speed at which it spins in relation to the sun, which gives the result of one full rotation every 24 hours. Divide the circumference of the earth at the equator in miles by 24 and that's the speed at the equator in mph. Relative to the sun, of course.

There's also something called a sidereal day if you want to measure the speed of rotation relative to more distant stars to account for the fact that the earth is orbiting the sun once every 365.25 days. A sidereal day is slightly less than 24 hours.

robinson · Post by **robinson** » Fri Oct 16, 2020 4:02 am

Of course the earth is spinning

ceptimus · Post by **ceptimus** » Fri Oct 16, 2020 9:32 am

I remember an interminable discussion on a forum or newsgroup concerning whether the moon rotates around its polar axis *, with respect to Earth.

One group maintained that because the moon always shows its same face to the earth, then it doesn't rotate. The other group argued that the moon rotates exactly once per lunar month - and that it has to do this so that it can always point its same hemisphere at Earth as it goes around its orbit.

The stupid thing was that everyone agreed exactly about the moon's motion - they just enjoyed arguing about the correct form of words to use to describe that motion.

This thread is now occupying the same territory of stupid.

* I assume that the group that said the moon doesn't rotate would argue about the very existence of a moon polar axis - but you know what I mean.

Anaxagoras · Post by **Anaxagoras** » Fri Oct 16, 2020 10:39 am

robinson wrote: ↑Fri Oct 16, 2020 4:02 am Of course the earth is spinning

Then I guess we agree and I don't really understand what point you were trying to make.

robinson · Post by **robinson** » Fri Oct 16, 2020 1:08 pm

If you take an orange and jam a stick through it, then hold it out and and you rotate your body 360 degrees, the orange always is in the same relation to you, and you made a complete revolution. Did the orange rotate on it’s axis 360 degrees?

robinson · Post by **robinson** » Fri Oct 16, 2020 1:11 pm

Answering that question gives the answer to the moon question

It doesn’t have to be an orange

Also, an object on a tower on the actual earth is the same question. Does an object on the equator that is unmoving, rotate on it’s axis every 24 hours?

( one could argue it does)

Or one could realize it does not, because yes, it’s arguing about a mental construct, not reality