Do you think any aliens exist in the universe?

[Spacetime Inhabitant]

Your Earth-Moon distances need an adjustment. Metres not kilometres.

Sorry. I do that all the time.

Maybe the problem is the peculiar units. Try meters and kilometers.

A meter is what one uses to measure the use of electricity, water or gas. The units are of French origin, and are basically proper names. Spelling them the American way is like spelling Ampere as Ampeer or Andre as Ander.

We may need to agree to disagree on who is misspelling or cheating whom.
For honest Americans, an inch is 1/39.37 of a meter/metre. That's 2.54000508 centimeters no matter how you spell centimeter. But buy something by the inch in Europe and you'll get only 2.54000000 centimetres. Even such a small swindle can add up after a while.

On the topic of who's shortchanging whom I was saddened to learn recently that the "Baker's dozen" (13, if you Anglophobes didn't know) was introduced in the 13th century and did NOT arise as a token of bakers' generosity. Just the opposite: They were selling underweight loaves, so threw in a 13th item to avoid lawsuits.

Britain (that includes England, land of the Angles) uses metric; the Anglophobes use American common measurements (except for scientists and some other professionals). I knew about the baker's dozen, but then I am not an Anglophobe (unlike many Americans seem to be).
BTW, which of these is correct:
1 mile = 1.6 kilometres (approx), OR
1 miel = 1.6 kilometers (approx).

 

[Swammerdami]

BTW, which of these is correct:
1 mile = 1.6 kilometres (approx), OR
1 miel = 1.6 kilometers (approx).

Speaking of Anglophones, where I live ALL distances are presented in km. (I assume King Charles' subjects at least allow us the usual "km" abbreviation if we're don't dare to write it out in full.) Nevertheless at least two Anglophones, upon seeing a road sign like "Nakhon Sawan 25" will say "It's 25 miles to the city." They are aware (I think) that kms and miles/miels are different, but can't be bothered. In their dialect "mile" translates as "whatever the local longish unit of distance is."

Similarly an Aussie once told me his house lot was "five acres." He had a largish lot -- big enough for a stinky pig enterprise -- but it was no five acres. In his dialect, again, "acre" translated as "whatever the local unit of land area measurement is." The local unit here is the rai (400 square wah) which is about 0.395 acres. (Haven't Aussies converted to hectares? A rai is 0.1600000 hectares.)

When you buy a plank of wood in the USA, I think the three dimensions are given in inches, inches, and feet -- all ancient English measures. In Europe it's cm, cm, met{er}s -- all meteric. But Thailand is ecumenical! The thickness is described with inches, the width with centimeters, and the length with sok. (The [sok] -- fingertip-to-elbow -- is ¼ of the wah -- fingertip-to-outstretched-fingertip.)

 

[unapologetic]

If objects with strength couldn't exist inside the Roche limit we would have no satellites.

But how stable are their orbits? Will they stay in orbit as long as the moon? Don't they sometimes fall back to earth? (As if a piece of a larger object.)

In their dialect "mile" translates as "whatever the local longish unit of distance is."

Not usualy a problem, unless signage about speed. Speed Limit X per hour.

I think the three dimensions are given in inches, inches, and feet -- all ancient English measures. In Europe it's cm, cm, met{er}s -- all meteric.

This becomes a problem when buying stuff on Feebay, unknowingly from China.

 

[steve_bank]

When a 2x4 piece of wood not 2x4?

A "2x4" is a nominal size, referring to the rough-cut size of lumber before it's processed. Lumber is dried to reduce moisture and then planed (smoothed). These processes remove a significant amount of wood, resulting in the smaller, standardized actual size of 1.5 inches by 3.5 inches. This standard was adopted to make lumber lighter for shipping, more consistent for construction, and to use less wood from each log.

 

[Loren Pechtel]

If objects with strength couldn't exist inside the Roche limit we would have no satellites.

But how stable are their orbits? Will they stay in orbit as long as the moon? Don't they sometimes fall back to earth? (As if a piece of a larger object.)

Satellites in low orbits fall because of atmospheric drag. And eventually tidal forces will bring down anything with an orbital period of less than one day, but that's a very slow process, satellites will have long since come apart before it brings them down.

 

[unapologetic]

If objects with strength couldn't exist inside the Roche limit we would have no satellites.

But how stable are their orbits? Will they stay in orbit as long as the moon? Don't they sometimes fall back to earth? (As if a piece of a larger object.)

Satellites in low orbits fall because of atmospheric drag. And eventually tidal forces will bring down anything with an orbital period of less than one day, but that's a very slow process, satellites will have long since come apart before it brings them down.

Isn't that how the Roche limit works?

 

[Swammerdami]

Just a mild complaint.

I received an ALERT that M. unapologetic responded to one of my posts!
What could it be? Most of my posts are largely ignored.
Did I espouse a mistaken belief in angels and/or demons? Did I inadvetantly confess to seeking thills with the angels on Floating Fotune oad? Did I fail to denounce creeping fascism focefully enough?
Or, worst of all, did I fail to edit a post carefully to insert all the missing R's? (I need to break down and buy an external keyboard. There must be a chocolate crumb or such wedged under the R key and, without a new keyboard I find myself avoiding words with r's. (For some eason it is capital r's that are hardest -- does that make sense?))

;

;

;

;
If objects with strength couldn't exist inside the Roche limit we would have no satellites.

But how stable are their orbits? Will they stay in orbit as long as the moon? Don't they sometimes fall back to earth? (As if a piece of a larger object.)

[what did I say, anyway?]

[and note that nobody in the quote maze even references whateve I said.]

Satellites in low orbits fall because of atmospheric drag. And eventually tidal forces will bring down anything with an orbital period of less than one day, but that's a very slow process, satellites will have long since come apart before it brings them down.

Isn't that how the Roche limit works?

I dunno. What do I have to do with the oche limit?

 

[Swammerdami]

When a 2x4 piece of wood not 2x4?

 

[bilby]

I dunno. What do I have to do with the oche limit?

Yeah, nested quotes on this board can be a bit of a pain in the ase.

 

[lpetrich]

Satellites in low orbits fall because of atmospheric drag. And eventually tidal forces will bring down anything with an orbital period of less than one day, but that's a very slow process, satellites will have long since come apart before it brings them down.

Tidal forces??? How would that work?

 

[steve_bank]

Draw a free body diagram of all the vector forces acting on an object. Add the forces vectorially to get magnitude and direction of the force of the object.

Drawing Free-Body Diagrams

The motion of objects is determined by the relative size and the direction of the forces that act upon it. Free-body diagrams showing these forces, their direction, and their relative magnitude are often used to depict such information. In this Lesson, The Physics Classroom discusses the details...

www.physicsclassroom.com

Post in thread 'Do you think any aliens exist in the universe?'

Wednesday at 9:32 AM

Satellites in low orbits fall because of atmospheric drag. And eventually tidal forces will bring down anything with an orbital period of less than one day, but that's a very slow process, satellites will have long since come apart before it brings them down.

Tidal forces??? How would that work?

• lpetrich

 

[Loren Pechtel]

Satellites in low orbits fall because of atmospheric drag. And eventually tidal forces will bring down anything with an orbital period of less than one day, but that's a very slow process, satellites will have long since come apart before it brings them down.

Tidal forces??? How would that work?

Very, very slowly. Mass generates tides. Anything that goes around slower than the planet will be accelerated by this at the expense of the planet's rotation. Anything that goes around faster (note that this includes anything retrograde) will be slowed, the energy going to the planet's rotation. It's not going to bring a satellite down on a human time scale, but the Martian moons are going to eventually go splat.

 

[lpetrich]

Size of tidal effect ~ satellite mass

That means that the tidal-drag rate ~ satellite mass

For artificial satellites, that is teeny teeny teeny tiny.

 

[Loren Pechtel]

Size of tidal effect ~ satellite mass

That means that the tidal-drag rate ~ satellite mass

For artificial satellites, that is teeny teeny teeny tiny.

But the satellite likewise has little inertia. I believe the drag is linear on mass and thus the size of the object is irrelevant to how fast the orbit is altered.

 

[lpetrich]

Size of tidal effect ~ satellite mass

That means that the tidal-drag rate ~ satellite mass

For artificial satellites, that is teeny teeny teeny tiny.

But the satellite likewise has little inertia. I believe the drag is linear on mass and thus the size of the object is irrelevant to how fast the orbit is altered.

Be careful not to mix up atmospheric drag and tidal drag. The latter is caused by the satellite making tides on the Earth, tides which get dragged by the Earth's rotation. Outside of synchronous orbit, the tides are dragged forward, pulling the satellite forward and thus outward. Inside of synchronous orbit, the tides are dragged backward, pulling the satellite backward and thus inward.

 

[Loren Pechtel]

Size of tidal effect ~ satellite mass

That means that the tidal-drag rate ~ satellite mass

For artificial satellites, that is teeny teeny teeny tiny.

But the satellite likewise has little inertia. I believe the drag is linear on mass and thus the size of the object is irrelevant to how fast the orbit is altered.

Be careful not to mix up atmospheric drag and tidal drag. The latter is caused by the satellite making tides on the Earth, tides which get dragged by the Earth's rotation. Outside of synchronous orbit, the tides are dragged forward, pulling the satellite forward and thus outward. Inside of synchronous orbit, the tides are dragged backward, pulling the satellite backward and thus inward.

Which is exactly what I'm describing!