J.C.MacSwell

Any sample you have will always be exchanging energy with its surroundings, which spontaneously goes from hot to cold, so even classically you can't get to absolute zero.

Wouldn't you have an infinitesimal chance of a shot at it classically? (Or perhaps Maxwells Demon could create it, by slowing all heat energy to zero, not using a gate but a paddle and expelling the energy outside the system)

I really tried to use the search but frustratingly couldn't find a thread answering my question.

 

On the moon (About 1/3rd of Earth Gravity (Irrelevant to out discussion so I wont mention it again) and no atmosphere) a hammer apparently reaches the ground when dropped from a set height at the same time as a feather.

 

I understand how air resistance effects terminal velocity. And how air makes things of different shapes fall differently, so I would expect the 1KG of feathers in a weightless bag with all the air sucked out to fall at the same rate as the one 1KG hammer.

 

However I am having trouble grasping how the 1 single small light feather can reach the ground at the same time as the much heavier hammer.

 

1. It takes much effort for me to lift the hammer to a high ledge using my muscles to push up against gravity, however it takes far less effort for me to get the feather up there.

 

2. It seems counter intuitive based on how gravitational body's effect each other in space when you think of the hammer, feather and moon as all being body's of mass (Like planets are). You would presumably expect two planets that are put next to each other to come hurtling together quickly however you would expect two footballs to take much longer to reach each other.

 

?

1. Also takes gravity as much effort to drop the hammer from the same ledge

2. The gravitational effect of two feathers on each other is less than two hammers on each other

@1: You need more energy to pick up the hammer. That's reflected in the hammer hurting more when you drop it on your foot, because it has a higher momentum at the same speed.

@2: The attraction that the feather and the hammer extert on the moon is very small, ignored in the calculation claiming they both drop within the same time and in fact small enough that there's no significant (measurable) change if it was considered. Ignoring part of the mutual attraction is not valid in your planet/planet or ball/ball example.

It is the same as what the moon exerts on the feather or hammer respectively.

Obviously this force will not displace the moon very much though, so it is usually ignored. (though I knew you knew alll that)

I think you'd be hard-pressed to have a helium-filled balloon in a vacuum.

It would of course roll around on the floor.

Thanks for the feed back. The book is already written but I keep adding ideas to it. The original world was round like Earth but had a greater diameter. To get around the gravity problem I simply stated that there were great hollow spaces within the Earth. This became a convenient setup when I put, on the East and West pole, two massive geysers at each end. The planets inner core caused the water within the Earth to heat up and spew endlessly from both sides. This force is great enough to send the water out of our atmosphere and create a ring of liquid water around the Earth. The circling would only be temporary due to Earths gravitational pull so the water flows down near the East and West poles, only to again be thrust back up into space by the perpetual geysers. This endless cycle allowed for a thin atmosphere to follow around the ring therefore allowing ships to sail out into space and return on the other side of the world. This was my first idea and I really like the liquid ring idea but I’m experimenting with other ideas.

This makes me think it has some kind of multidimensional quantum spin:D

Since kinetic energy increases with the square of the speed if I double the speed would I quadruple the Kw-hrs?

yes

It can scatter a photon and get some energy and momentum, but it can't just absorb the photon — you couldn't conserve energy and momentum, which is a standard relativity exercise to work out.

 

At some point, though, you might invoke Heisenberg to tell you how long the scattering might be able to delay the photon. Compton scattering always changes the photon direction, but this is not what is being described here. (I'm sure of one were to discuss what happens in a plasma there would have to be interactions with electrons)

Thanks. I assume these two (that I bolded above) are related. Interesting.

Well, photon/atom interaction, technically. Free electrons don't absorb photons, bound systems do.

Can a free electron interact with and absorb some of the energy and momentum of a photon?

a thought occurred to me just, IF we were to employ Tidal power on a Massive scale, obviously we`de be extracting energy out of a System.

 

*(there`s no such thing as a free lunch)*

 

would this have any backlash on the Moon and it`s Orbit?

Yes. Less energy would be extracted from the system than otherwise.

No answer yet....

Just want to bring to your attention that if spacetime is something, then everything in the universe is connected, everything is in contact with everything. Does it make some sense ?

Somewhat. Similarly all events would be connected, regardless of when or where they took place.

However they cannot all be causally connected as per relativity.

I would say that it is something. Without it everything happens at once and in the same place.

So you say 15,000 tons of mass converted to energy per second.

 

Tycho that is a good figure to know if it is right.

Lemme see if it agrees with the 3.8 e26 watts in my handbook.

 

A kilogram converts to 9 e16 joules, so a thousand tons to 9 e22 joules

and a million tons converts to 9 e25 joules

 

So my 3.8 e26 watts which I am pretty sure about would translate into

 

38/9 million tons per second = 4,200,000 tons per second

 

So I would say that the sun must lose 4,200,000 metric tons of mass every second JUST TO PROVIDE FOR THE LIGHT THAT WE SEE coming out.

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so I think your figure of 15 thousand tons per second is way way low.

Maybe I'm missing something. But please check your figure. We should be in closer agreement

 

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tell this newcomer spiker that he should get a different avatar, this one is in use

No wonder it hurts when it hits you straight into the back of the eyeballs!

CPL, the egg is held in the middle of the box by foam struts otherwise it would sit on the bottom and likely crack, the foam keeps it from touching the sides and the water allows it to be slowed don really really fast without breaking.

I like this idea IA. As long as the foam is fully saturated you are only dealing with the shock wave. And if it is not quite fully saturated much of that would be reduced without excessive pressure differential (other than the shock wave). A good time to fine tune this would be around breakfast time with a large family. It might break the yolks but not the shells.

The tension of the seat joined to the Ferris Wheel keeps it from falling off. Also, you don't use "Force applied" when you're defining forces in circular motions. Tension is another kind of force that points toward the centre. You'll learn it soon enough.

Tension can point toward the centre but depends on the structure as well as the external forces.

After thinking about it for a while I am not convinced that for a y-shaped string, the resulting wave would be a superposition of the the two original waves. The reason for this is that there would be a change in the tension in the ropes. If two strings meet and continue as one, then the tension in the one string will be twice that of the individual strings. The amplitude of the oscillation in the rope will depend on both the vibrational energy and the tension in the rope. (you can see this on a guitar string while you tune it)

 

I intend to confirm this by monday.

If the strings all meet at 120 degrees the static tension would be all equal, though I suspect waves on two of them meeting at the apex simultaneously would not completly constructively interfere down the third string but also have two secondary waves rebounding back down the two original strings.

A lot of the physics treatment of friction is an approximation, but it's true the standard equation doesn't involve surface area. If the total area is greater, each unit area exerts less force (i.e. the pressure is smaller), and contributes less friction. In the approximation used, that exactly cancels with the greater surface area, and that's observed to hold in many cases.

And of course the equation still holds, the coefficient may change, but usually not by much for the reasons you mention.

Weigh three balls versus another three balls, then one ball against another ball. The choice of the balls for the first weighing is random. The choice for the second weighing depends on the outcome of the first:

• First weighing shows equal masses:
  Weigh the remaining two balls against each other. The odd ball is the heavier of the two.
  
• First weighing shows unequal masses:
  Weigh two of the three balls from the heavier group against each other. If the second weighing shows equal masses, the odd ball is the unselected ball in the heavier group. If the second weighing shows unequal masses, the odd ball is the heavier one.
  

Or just look at them. If one of the blocks is a ball you have found the odd ball.

I disagree with most of what had been said so far. The difficulty is really the use of the word 'particle' which comes with it too much baggage.

 

The word 'wave' is much better - much more accurate. People have a bad habit of only thinking of a wave as a plane wave, spread out over all space. While this is a wave, waves can also be very localised. A wave can look and behave exactly how we percieve a particle would if it is sufficiently localised.

 

Indeed, since our measurements of position are never 100% accurate, we will never know exactly where a 'particle' is, so it is really a superposition of the position eigenstates, i.e. even after measurements, it is still a wave, albeit a localised one.

 

I think we confuse people when first talking about quantum mechanics with this wave/particle duality business. We should be just calling them waves and leave it at that.

Should we just call an electron a wave also, and leave it at that? I know there is a difference, to a degree, but reduced far enough there is no particle aspect left (I think?), yet both have some particle like properties that emerge from the "wave".

Until, of course, it continues its rotation and a doorframe hits you on the head.

I didn't even see it coming!

If you are in a space station being spun to make artificial gravity and run real fast you would decrease in "weight" going one way, in which case at some point you could jump just right and hover above "ground" unable to reach anything, or increase in weight if you ran in the opposite direction.

Can a second set of wheels be triggered to come into play on picking up the object that are geared to be in reverse? They can already be spinning in reverse but not touching the ground and the initial wheel set can continue spinning forward but be lifted off the ground.

Ok, so I was just reading about Quantum Tunneling. About the energy a particle has can wildly fluctuate in a short enough time scale. This is somewhat difficult to absorb because it doesn't make any intuitive sense to me about "borrowing" energy and reqlinquishing it within a small timeframe.

Where does it borrow this energy from? Other nearby particles?

 

Greene explains that if you were to shoot a plastic pellet at a concrete wall, that the wave functions of the particles making up the pellet all have a tiny piece that spills out through the wall. And so, the pellet has a small chance of going through the wall after repeating the action enough times.

 

I'm not putting this together very well. I dont' see how pieces of a wave function penetrating the wall could equate to all of the particles penetrating the wall at some lucky point.

I picture this as being borrowed from space itself which is a quagmire of energy fluctuation. Anyone see pitfalls in this idea?

Wrong. The well can be much deeper than the surface of its water.

 

That is not even the distance to the water level in the well.

The unknown size of the stone poses a much more complex calculation, as the larger it be in relation to the unknown well pipe diameter, causes more air cushioning its falling velocity.

The unknown gap between the stone and the well pipe wall can change calculations considerably.

 

Miguel

Throw in any friction calculation and the resulting distance is shorter for the given time.

So what is Gravity? If mass gives you gravity and Gravity gives you mass,then mabye there is no mass;just gravity.

 

After a long day at work, I came home to do some dishes. After I was done I let the water down the drain.In a tired daze I watched as the water went down the drain in a tornado like whirlpool.Then all of a sudden I looked at the image of the drain behind the whirlpool,and discovered that gravity was staring right at my face.Gravity was something that spins!

 

My first thought was that there was a spinning partical that acts for gravity,but that was too simple.

 

So first I found these Protons,and then I found these Neutrons.I put them together with gravity.The more I put together,the bigger the gravity feild got.Then I realized that to many of them would cause way to much gravity,so I had to seperate them into smaller fragments.So I called around and found this guy named electron,he said he could shield the small fragments from eachother,but the problem was that he said he was not effected by gravity.So I thought and thought and finally found a solution to the problem.Ill give the proton a positive charge and the electron a negitive charge,this way they will stay together!I called it an Atom!

I put the atoms together so the gravity of the nuculeses would pull on eachother and the electrons would repel them in a perfect balance.It was perfet!But now I needed a energy source to get everything into motion.

I found these things called quarks,there really cool!They suck up a whole lot of heat energy and light,and then they start to spin,creating a gravitational force.So I stuck 3 inside the protons and Neutrons.

And on the seventh day you deserved a good rest!

A creationist friend of mine is claiming that the reason we see distant starlight is because there was a rapid expansion of the universe at creation. The universe expanded for about 2 picoseconds to its present size, and lightwaves along with everything else were stretched. This, he says, explains the redshift of distant galaxies. The farther the galaxy, the more expansion had to have occured, the more redshift (stretched light) we see.

 

Is there a way to test this idea? I'd imagine there's got to be a way to measure the spectral emissions of distant elements, note the redshift, and calculate what kind of expansion could have created this redshift and see if it correlates with the star's known distance. Anyone?

Wouldn't they all be stretched the same amount but, due to the extra distance of anything more than X lightyears away (X being the time since creation), the light from those sources simply would not have arrived yet?

I recently saw the documentary, The Great Year, and toward the end they bring up the idea that our sun is actually part of a binary star system. Our astronomy class never covered such a concept, and the idea boggles my mind. Could this be true?

Isn't the alpha centauri, our nearest neighbour, a 2 or 3 star system. If we aren't part of that how could we be a binary with something else.?