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Physics, Astronomy & Cosmology / Re: Spinning a cassette player with a rope: same sound?

« on: 07/04/2023 15:31:31 »

The speed of the tape only matters relative to the magnetic head that senses the tape as it moves across. So spinning the wheels of the cassette faster to make the tape wind faster will change the pitch of the sound, but hurling the whole tape player around the room won't change anything.

True, makes sense. And the same could be said for a drill used in the ISS, the speed relative to its shaft doesn't change.

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Physics, Astronomy & Cosmology / Spinning a cassette player with a rope: same sound?

« on: 07/04/2023 11:34:55 »

I am asking this because I have never tried, it's hard to find a cassette player now. But I was thinking that when we were playing a cassette inside a fast moving car, the speed of the tape would be considered faster only for those outside the car, but for those inside the car the speed of the casstte would be totally normal and the speed of sound would be totally normal because the air is contained and travelling within the car. The same could be said for any spinning things, examples, a drill, a fan or a turntable inside the ISS for us on Earth would be spinning much faster, because we add the speed of the ISS to it, but for those inside the ISS the drill speed is  normal, and the turntable speed is the same normal speed, with a normal sound. But let's say I am in my room, I have a cassette player (I don't... ) with blue tooth speakers (so the speakers are not moving), and I spin the cassette around me with a rope: in this case, should I add the rope speed to the cassette speed, should I hear a different sound, or will I hear a normal sound without any acceleration?

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Technology / Re: Has anyone exploited the balancing half-sphere for electricity production?

« on: 04/02/2023 13:11:10 »

What is the proposed source of energy causing it to wobble?

It could be people, or it could be wind outside, or a mix of wind+magnets.  What do you think?

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Technology / Has anyone exploited the balancing half-sphere for electricity production?

« on: 04/02/2023 00:08:08 »

Can this idea be useful? A pole wobbling on a huge concrete half-sphere? Can this become some sort of "wave power" at home?

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Technology / Re: Electricity Generation via treadmill. Can one person generate enough?

« on: 03/02/2023 23:58:35 »

And yet human muscles can power a helicopter.

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Physics, Astronomy & Cosmology / Electrons made of photons?

« on: 27/12/2021 13:25:27 »

Curious about it, we can't "see" travelling photons in action when they travel in a straight line, or when they carry electric and magnetic fields that oscillate at a certain frequency, the so called wavelength (how can they travel straight and oscillate at the same time by the way? Are they particles or not?). I have also read that two photons sometimes could combine to produce an electron. So is it possible that electrons are just well packed photons? What do you think? Difficult stuff, speak your mind as freely as you can.

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Technology / Re: soundproofing in a 3d printed house?

« on: 10/05/2021 20:31:07 »

None-the-less, I'm not going to alter my opinion that the OP idea was a good one.  It demonstrates a good understanding of scientific principles and it's not an idea I would have thought of.

Many thanks, don't alter your opinion  , it's extremely rare to see someone praising me in a scientific forum, actually this is the first time, hehe. Not many people post in a science forum, I'd love to see more posters, like for cooking, painting, sport, art forums, but it's difficult. I am a layman here.

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Technology / Re: soundproofing in a 3d printed house?

« on: 02/05/2021 16:21:45 »

A bit of a word jumble in the OP's post. 
Vacuum Pump or Vacuum Cleaner? 

Sound deadening tends to be the use of certain materials such as rubbers, or porous materials such as foam.  A 3-D printer could potentially print a porous material, or augment the printing by using self-expanding foam.

I mean any piston pump used for vacuum containers. If the concrete doesn't crack, it can be an easy task for the 3d printer to leave just a tiny gap.

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Technology / soundproofing in a 3d printed house?

« on: 01/05/2021 20:27:38 »

Soundproofing can be easier maybe in the near future. No more blankets, carpets, thick panels on the walls, ceiling, floor. 3D printed houses don't leave gaps, but if they leave just a few mm of space between the wall, ceiling, floor, it could be vacuum pump easily later, if the tenant needs to.

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Physics, Astronomy & Cosmology / Re: speed of projectiles inside a free falling vacuum chamber

« on: 13/04/2021 14:32:25 »

Why? Point A is yellow, point B is green. How long does it take for the arrow to travel from A to B, and how long does it take for the arrow to travel from B to A.

Travel time from A to B equals the travel time from B to A
If you are in an airplane with no windows there is no experiment you can do to prove whether you are flying at 600 mph or sitting on the ground.  In the free fall example, if you are on a space station there is no experiment that you could do to prove whether you were in free fall of just sitting out in deep, deep space and not under the influence of any gravity source.

You got admit Alvancalvard's color comment was pretty funny.

Then you can't do any measurement. How can you measure the speed of a car, athlete, cheetah, train?  We simply use a clock, and measure how long does it take for the car, plane, boat, to travel from point A to point B, no need to take into account the movement of the Earth, Solar system and galaxy. Arrow or bullet inside the train is no different, it's done in the same way, you don't need to take into account the speed of the train.

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Physics, Astronomy & Cosmology / Re: speed of projectiles inside a free falling vacuum chamber

« on: 13/04/2021 09:52:10 »

If the entire assembly is in free fall there is no way anything inside the chamber can know which way the chamber is moving, therefore AB ≡ BA.   

Why? Point A is yellow, point B is green. How long does it take for the arrow to travel from A to B, and how long does it take for the arrow to travel from B to A.

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Physics, Astronomy & Cosmology / speed of projectiles inside a free falling vacuum chamber

« on: 13/04/2021 09:38:29 »

As a result of the previous thread I tried to google about speed of arrows-bullets inside a free falling vacuum chamber. And I haven't found any, can you help me?? How can this be even possible? I know they did experiments in a static vacuum chamber on the ground, but I haven't found anything about projectiles inside a free falling vacuum chamber. It could be done easily on the ISS. Example, they could assemble a long vacuum chamber/tube/channel. Inside the vacuum tube, at the end of each side (A and B), they put an automatic crossbows or gun. Then calculate if the projectile fired from A to B (travel direction of the ISS) would be slower than the projectile fired from B to A (opposite the travel direction).
Or, they could easily do the same experiment by dropping a long vacuum chamber from the sky.

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Physics, Astronomy & Cosmology / Re: Watching, hearing, playing in a spaceship travelling near speed of light

« on: 13/04/2021 00:57:10 »

ah ok, who cares about a cosmic particle point of view, I am talking about a freaking human inside a Sci-Fi ship at 98% the speed of light

From the point of the freaking human inside the ship, the ship is stationary by definition. Per the 400 year old Galilean principle of relativity, everything works normally inside the box (ship), so he notices nothing.
You seem to be under the delusion that speed is absolute and it is meaningful for a ship to be going at .98c without giving a reference. The cosmic particle can be the reference.  Anything can. There is no speed I can go where there isn't a planet somewhere that is very very close to stationary relative to me. So Earth is very much moving at .98c relative to some planet 13 billion light years away, and yet we don't see the difference between the various televisions in the pub.

What is he/she going to experience considering that images and sounds have to make their journey before reaching your eyes/ears (and skull in the case of the ball).

Relativity theory says that no abnormal experience will be had. The one TV is 10 meters that way and the other is 10 meters the other way. Light moves at c relative to the ship or any other inertial frame, so the two are nicely in sync since it takes light equal time to reach you from each direction.

According to Relativity speed of light can't be exceeded or changed. I am not arguing with that, the images from the two tv travel at the same speed, but what I don't understand is why the direction wouldn't affect the watching experience. For example, on the ISS they shoot two laser beams, one is shot towards the Earth, the other laser is shot towards the opposite direction. The two lasers will travel obviously at the same speed, but which one of them will reach the Earth? Is the direction irrelevant?

If the TVs are not moving relative to you, you will see no difference in images coming from either one.  The only way you would see a difference is if one was moving away from you and one was moving towards you.
Relativity say that the speed of light( in a vacuum) is invariant, and  that anyone in an inertial frame ( in this case non-accelerating) will measure light as traveling at c relative to themselves.
So you, in the spaceship would measure the light coming from the TV's as traveling at c relative to yourself. If the TV's are equal distances from you, you will see the same images at the same time from both of them.
Now, for someone that you are traveling at near c relative to would also measure the light from each TV as traveling at c relative to them, and that you would be rushing towards the light emitted by one TV, and running away from the light emitted by the other.   He will however agree with you that the same images from the TV arrive at your eyes at the same moment.
For this to happen, the image from one TV will have had to be emitted before the same image was emitted by the other TV.

Thus for you, both TVs emit the same images at the same time and they arrive at the same time. The emission of the program from the TV are synchronized to each other.  But for the other observer in order for you to observe simultaneous images, the two TV's cannot be in sync with each other.
This is the Relativity of Simultaneity.  Simultaneity is not absolute ( different frames of reference can disagree as whether given events are simultaneous or not). 
While this seems counter-intuitive, and goes against previous notions of how time behaves, it is the way time works in our universe.

Are lasers beams any exception to this rule? Because I would consider the images from the two tv just like thousands of laser beams shot towards the viewer eyes. And it doesn't need to be a tv, it could be two persons singing and dancing the same tune, one person in front of you and the other person behind you. But let's talk about lasers, maybe easier to discuss and understand, because they are directional. A laser is shot for example from the Earth towards the moon, to measure the distance. If the laser wasn't directed exactly towards the mirror, it will never make its journey back to the Earth. Am I right?
Another example, a ship is travelling at the speed of light (I know it's impossible but just imagine that) and will do a flyby of Earth. This ship will shoot one laser ahead (towards the travel direction), and another laser beam at the back (opposite the travel direction). What would we see from Earth during the flyby? I suppose we would only see one laser trail left from the laser at the back of the ship, but we wouldn't see any beam shot from the front. Isn't this all about direction?

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Physics, Astronomy & Cosmology / Re: Watching, hearing, playing in a spaceship travelling near speed of light

« on: 12/04/2021 23:32:40 »

ah ok, who cares about a cosmic particle point of view, I am talking about a freaking human inside a Sci-Fi ship at 98% the speed of light

From the point of the freaking human inside the ship, the ship is stationary by definition. Per the 400 year old Galilean principle of relativity, everything works normally inside the box (ship), so he notices nothing.
You seem to be under the delusion that speed is absolute and it is meaningful for a ship to be going at .98c without giving a reference. The cosmic particle can be the reference.  Anything can. There is no speed I can go where there isn't a planet somewhere that is very very close to stationary relative to me. So Earth is very much moving at .98c relative to some planet 13 billion light years away, and yet we don't see the difference between the various televisions in the pub.

What is he/she going to experience considering that images and sounds have to make their journey before reaching your eyes/ears (and skull in the case of the ball).

Relativity theory says that no abnormal experience will be had. The one TV is 10 meters that way and the other is 10 meters the other way. Light moves at c relative to the ship or any other inertial frame, so the two are nicely in sync since it takes light equal time to reach you from each direction.

According to Relativity speed of light can't be exceeded or changed. I am not arguing with that, the images from the two tv travel at the same speed, but what I don't understand is why the direction wouldn't affect the watching experience. For example, on the ISS they shoot two laser beams, one is shot towards the Earth, the other laser is shot towards the opposite direction. The two lasers will travel obviously at the same speed, but which one of them will reach the Earth? Is the direction irrelevant?

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Physics, Astronomy & Cosmology / Re: Watching, hearing, playing in a spaceship travelling near speed of light

« on: 12/04/2021 21:31:48 »

Sorry, I don't get you. Doing a quick google search, the speed of the Solar System around Milky Way is approximately 220 km/s (490,000 mph) or 0.073% of the speed of light. And even if you add the Milky Way motion towards Andromeda, the speed is about 368 km/s, which is still nothing compared to light speed.

He is saying from the frame of cosmic particle we are traveling at nearly the speed of light.

ah ok, who cares about a cosmic particle point of view, I am talking about a freaking human inside a Sci-Fi ship at 98% the speed of light , just for fun. What is he/she going to experience considering that images and sounds have to make their journey before reaching your eyes/ears (and skull in the case of the ball).

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Physics, Astronomy & Cosmology / Re: Watching, hearing, playing in a spaceship travelling near speed of light

« on: 12/04/2021 20:21:48 »

Did you see my point about measuring my speed WRT a passing cosmic ray?

We are on a ship travelling at nearly the speed of light; it's just that you didn't notice.

you mean the Earth is travelling near the speed of light?

Yes.
And it is also stationary.
That's what it means when people talk about "relativity".

Sorry, I don't get you. Doing a quick google search, the speed of the Solar System around Milky Way is approximately 220 km/s (490,000 mph) or 0.073% of the speed of light. And even if you add the Milky Way motion towards Andromeda, the speed is about 368 km/s, which is still nothing compared to light speed.

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Physics, Astronomy & Cosmology / Re: Watching, hearing, playing in a spaceship travelling near speed of light

« on: 12/04/2021 19:33:19 »

Did you see my point about measuring my speed WRT a passing cosmic ray?

We are on a ship travelling at nearly the speed of light; it's just that you didn't notice.

you mean the Earth is travelling near the speed of light?

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Physics, Astronomy & Cosmology / Re: Watching, hearing, playing in a spaceship travelling near speed of light

« on: 12/04/2021 19:12:31 »

You've not said if the ship is accelerating or not.

If it is not accelerating, then it is stationary in its own frame and the two movies will be indistinguishable in every way, assuming you're the same distance from each of them and they were started simultaneously relative to the frame of the ship. Nothing is out of sync. Playing tennis will not work in free-fall.

If the ship is accelerating, then you can apply the equivalence principle and say that the experience is the same as watching two screens in a building, one a few floors above you, and one a few floors below you.  If they're started simultaneously in the frame of the building, the one above you will run faster and slowly get out of sync with the one below you. Same thing on the ship. Playing tennis only works if you're horizontal relative to each other, not one above the other, so the tennis thing would be like trying to play tennis in an elevator shaft, which doesn't sound much like tennis.

I am talking about free fall, no acceleration, I thought it was obvious, but thank you for chiming in. And no tennis, just a ball thown to hit you.

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Physics, Astronomy & Cosmology / Watching, hearing, playing in a spaceship travelling near speed of light

« on: 12/04/2021 18:23:01 »

Let’s say there are two tv playing the same movie, one screen is in front of you (direction of spaceship travel), the other screen is behind you (opposite the travel direction). I suppose the movie played by the screen in front of you will appear and reach your eyes as if the movie was played at higher speed than normal. The movie played by the screen behind you will appear and reach your eyes as if the movie was played at slower speed than normal.
The sounds will reach your ears in the same way from both tv speakers, and they will both sound normal, like on Earth. But they will be both out of sync with the images: the sounds coming from the screen in front of you will reach your ears after the images, and the sounds coming from the screen behind will reach your ears before the images.
Playing tennis inside the spaceship. Seeing and feeling will be out of sync. Actually let’s make it easier than tennis. There are two guys throwing a tennis ball to hit your head. Like for the tv case, one guy is in front of you (direction of spaceship travel), the other guy is behind you (opposite the travel direction). When the guy in front of you throws the ball, you will feel as if the ball is hitting your head after it reaches you. When the guy behind you throws the ball, you will feel as if the ball hits your head before the ball reaches you.
What do you think?

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Technology / Re: Can we use convection to move desalinated seawater inland?

« on: 10/04/2021 19:06:47 »

One point that comes up with some of the previous comments is that one often thinks of a closed system employing pipes and canals. 

But, if one had predictable wind circulation, one could also do a completely open system. 

Evaporate the water at sea level, and let it naturally gain elevation and condense out as rain.  One might think of this as bad heating ocean water, but if one concentrates solar energy, it might have a net benefit of transporting energy into the upper atmosphere without a net increase in open sea water temperature.

Essentially just improving on Mother Nature.

The problem is that many deserts have a lack of rainfall for reasons that would be more difficult to overcome.  Thus we have the largest rainforests surrounded by deserts.

Here we talk about rainy Oregon, but that is primarily a single valley.  The Cascade Mountain Range has the effect of trapping and condensing moisture in the air and giving lush green farmland to the West and desert to the East.  The weather is also very seasonal here, and global warming could impact our "dry season".

It may be that there would be some coastal areas where one could build rain evaporators that would be less affected by winds out in the middle of the Pacific and Atlantic.

Nonetheless, to make a dent in rainfall, such a system would have to be HUGE.

The good thing about desert greening, is that you need just a bit of fresh water to kickstart, you are not obviously going to plant thirsty almond trees. And once the forest is made, it will create its own climate keeping moisture and creating even rivers.