If Energy cannot be created or destroyed, how can there be a beginning to the Universe ?

Sure thing, if I ever run across one I will.

They eye of a hurricane can easily be 50 miles wide, lol

 

it would help to know what your asteroid hit. could have been mud or water, and I just realized you said extinction where did that physics come from?
Arjay51 is on ignore

 

I was referring to the mass of the object that slammed into our planet. It hit both land and water and created an enormous crater....where did its mass go?

 

I dont know which asteroid you are talking about but if it could not be found after impact it most likely disintegrated into sand/dust.
Arjay51 is on ignore

 

So...its mass was converted into the explosion and created the massive impact crater and made dinosaurs extinct. Did the debris it created have mass?....after it landed?

What about the one in Arizona....does the debris all around it have mass?

 

Well everything came apart as I said and made dust, dust is mass.
Arjay51 is on ignore

 

I see....so what of the bigger chunks that do not get pulverized? And is "Dust massless?

 

what are you driving at, your challenge is so vague there are several different answers. dust has mass, unpulverized has mass.

 

Yet they do not move...have no velocity.

 

upon impact which is what I presumed you were talking about they moved a lot. However try extracting energy from any of it today, tomorrow or anytime in the future, not going to happen, it released its energy upon impact and the resulting fallout.

 

here I thought were were talking about physics, my mistake.

 

Again, potential doesn't mean potential in the sense that it might come to be, but that it is associated with a potential (which broadly means that it is fully defined by its position, and does not depend on how it came to hold its position). The potential energy of a rock is the same, no matter how firmly locked in place it is. The definition of an energy does not rely on being accessible, it relies on being the quantity which would give rise to motion if it was accessible.

Firstly, I could remove the restraints, empty out the valley around the rock, but that's not really the solution to your problem. The real solution is that energy is defined as _the_ property which can give rise to motion, it does not require that the particular instance of energy you're referring to can be made into motion.

I agree that more motion is more energy, all else being equal, but where do you get the idea that no motion means no energy? As best we know, energy follows the relation E^2 = (mc^2)+(pc)^2, which certainly agrees with the idea that more motion is more energy, but it does not say that there is no energy when there is no motion. While standing still, the energy becomes E=mc^2, as expected.

No, a force does not require that the object moves. If you push a large boulder, you will exert a force, even if you fail to move the boulder. If you fasten a rock, it may not fall or otherwise move, but the potential energy (and in particular the gradient thereof) will still give rise to a force (even if the force is not big enough to set the rock free). Again, the definition of energy does not require that the energy is released, it is only required to be the property which, if it were released, would give rise to energy (even if that release doesn't actually take place).

Yes, a force is applied, but the force in question stores potential energy in the rock. "If the work done by a force on a body that moves from A to B does not depend on the path between these points, then the work of this force measured from A assigns a scalar value to every other point in space and defines a scalar potential field." (source) and that is the potential which the word "potential energy" refers to.

You haven't shown that the rock doesn't have energy, you've merely shown that if the rock has energy, it will stay in the rock, until it is released, which indeed is the case.

That's no stranger than the fact that you could use the potential energy in the counter weight of a trebuchet to send an object into the air, far above the trebuchet.

Sure. You could use potential energy too, you could use a falling object to generate heat through friction (not super efficient or anything, but certainly possible) or the other classic example to use the potential energy of water to drive a mill or a generator.

I don't particularly have a problem with that. Potential energy is also given to objects, for instance by putting a rock on a shelf.

I have no doubt, anyone with smidgeon of physics knowledge could see the errors of your arguments.

 

no that is not what I said. I never said or implied that an object must move just because a force was applied.

you claim energy is put into the rock, if that were true the rock would release all the energy that willie stored in it in addition to the energy from the force of gravity pulling it back down. but it does not, therefore it goes without saying that no energy was stored in the rock.

If 100 joules was stored in it going up then coming back down would be mv^2 or 200 joules, if no energy was stored in it then it would be 100 joules (presuming no losses)

btw I think you meant E^2 = (m^2c^4)+(pc)^2,

 

Too funny!!!

 

Well, the force is the gradient of the potential energy (or at least, conservative forces, such as gravity, are). As you can see here
https://en.wikipedia.org/wiki/Conservative_force#Mathematical_description
a force "can be written as the negative gradient of a potential, ". Just like a force can fail to move a rock, but still be a force, an object can have energy which fails to be extracted, but still be an energy.

What makes you think the rock would release all its energy? It would only release the potential energy from its falling, any other energy is likely to remain where it was.

I like to liken it to a piece of coal. You could lift and release a lump of coal, yet in doing so, you would not release the energy which you could release by setting the coal on fire.

Not sure I understand your sentence structure. You could have a rock which you throw into the air. Starting out, it would have mv^2/2 of kinetic energy, mgh of potential energy and mc^2 of rest energy (m is the mass, v is the velocity, g is the gravitational constant, h is the height from which the rock is thrown, H is the height it reaches at the top and c is the speed of light). When it reaches the top, it has 0 kinetic energy, mgH potential energy and mc^2 rest energy. When you catch it again, it had mv^2/2 kinetic energy again, mgh potential energy and mc^2 rest energy. The mc^2 was not released, not all of the potential energy was released (more energy would have been available if the rock somehow kept falling through the hand/floor).

True, I missed out a ^2.

 

Sure but not the rock in the conditions I posted.

We are not talking about coal, we are talking about a rock in a specific model.

No you could not have a rock which you throw in the air because that is not the problem I gave you. Its pretty obvious why you continue to change the model to your own instead of using the one I provided.

 

Why not?

My point is that your statement that all energy in a rock is released when it falls is incorrect. If your statement had been incorrect, then you could get energy out of coal by simply dropping it. This is demonstrably not true, so the principle you were relying upon is incorrect.

Why couldn't I throw a rock in the air? I have done it many times.

The problem you gave me is perfectly compatible with my understanding. If it stands still, as it would if attached somewhere, it will have some potential energy, some rest energy and a kinetic energy of 0. If you wait a little while, it will still have the same potential energy, the same rest energy and the same kinetic energy of 0. No energy has been extracted, but that doesn't mean there's no energy there. You just haven't converted it to anything interesting.

 

wrong, I even gave you numbers, neither am I splitting hairs down to a quark like you are attempting to do which is not part of the problem.
please try to keep it in the same context I put it in.

Because that is not the problem I gave you.

No its not because you removed the filled in valley and emptied it, so you could reconstruct the problem I gave you to 'fit' your understanding.

Do you deny that a force slightly greater than gravity is required to elevate the rock and the force of gravity pulls the rock back down when its released?

 

The numbers just seem incorrect to me. You have give a rock 100J, yet when it came down, it had 200J, violating energy conservation. This context not an example of something that happens in reality (unless there is something else going on which you have omitted, such as someone hitting the rock towards the ground with a baseball bat).

Let's say you have a rock with a mass m=1kg. At a time called t1, you throw it into the air with, let's say a speed of 1m/s. The total energy of the rock is:

E = Ek+Ev+Er = mv^2/2 + mgh + mc^2 = 1*1^2/2 + 1*10*0 + 1*300000000^2 = 1/2+0+9e16 = 900000000.5 J

E is the total energy, Ek is the kinetic energy, Ev is the potential energy, Er is the rest energy, m is the mass, v is the speed, g is the gravitational constant, h is vertical distance from your hand to the rock (we could use a more complicated version of the potential energy, but this is close enough for now), c is the speed of light.

The rock flies through the air. At some point, let's call it t2, the rock reaches it's highest point, h = 0.05m. Its energy is

E = Ek+Ev+Er = mv^2/2 + mgh + mc^2 = 1*0^2/2 + 1*10*0.05 + 1*300000000^2 = 0+1/2+9e16 = 900000000.5 J

When the rock reaches your hand on the way down, at a time t3, the energy is

E = Ek+Ev+Er = mv^2/2 + mgh + mc^2 = 1*1^2/2 + 1*10*0 + 1*300000000^2 = 1/2+0+9e16 = 900000000.5 J

In particular, note that

• The total energy stays the same
• Energy is transferred from kinetic to potential to kinetic in the steps
• The 9e16J of rest mass is inside the rock at all times, dropping the rock does not release it

You can effectively vary some of the numbers, but if you give it 100J of kinetic energy when you throw it, it will have 100J of kinetic energy when it is back where it started.

So? Physics remains true even in examples other than those you might choose to consider. I have given some examples that make the point I'm trying to make. Your example seems to me merely unphysical.

And is there a problem with that? If you're allowed to fill it, I see no reason why I couldn't reempty it.

Either way, it doesn't matter, because potential energy is not necessarily measured with respect to the bottom of whatever valley or floor happens to be beneath it. It can be measured with respect to any constant position, and filling up the valley doesn't change that.

 

you just wasted a lot of font ink.
of course it violates the conservation of energy, thats the whole point LOL
it is real, works the same way if you pick up the rock spend 100j then at the exact instant you release it we also remove all 'FORCES' of gravity. the rock goes no where because you stored no energy in it.

compare that to a capacitor, where you do store energy in it, again assuming 100% efficiency you out what you put in 100j in give you 100j out. Not the rock.

Apparently you deny that gravity is a force.

in fact in the rock case potential energy is not 'measured' at all. it is nothing more than a calculation based upon the FORCE in the opposite direction that gravity will apply when sucking it back down.

You are right, the fact that you have to empty to make your problem work proves my point thank you very much! Likewise I filled it in to make my problem work

 

What do you mean "the whole point"? Energy conservation is not violated in nature/reality (except possibly in some unconfirmed processes which are very short-lived). The whole point of energy conservation is that there is no violation of it.

Sure, the force is the negative gradient of the potential energy, if you remove the force, then you remove the energy. However, given that you can't in practice remove the force, you can't in practice get away from the fact that there is potential energy there.

Why not the rock? In throwing a rock, you put 100J of energy in, and if it is allowed to fall back to the same height as it was thrown from, you will get 100J back. You won't get any 200J out of it, since there is no violation of conservation of energy.

Nope

Not really, filling it in doesn't make your problem work. If you put a rock on a shelf, you give it energy, and that energy will remain with the rock until it comes down. If it doesn't come down for whatever reason, then the energy remains with the rock. Filling in the valley does not change that fact.

 

I agree that the 'calculation' works, not a problem, so you admit then that you apply work (give it energy) on the way up and gravity applies work (gives it energy) on the way back down.
no energy is 'physically' stored in the rock as it is in a capacitor. cant get more simple than that.

 

Instead of throwing the rock up in the air, lets roll it down a steep hill. Gravity sends the rock down but at the bottom of the hill the ground levels out and the rock keeps moving. Did the rock not 'store' some energy that allowed it to keep moving?

 

that falls under conservation of momentum.
you have to exceed or apply more force than the force of gravity to get it elevated, and the most you can ever get back is gravity. If it was truly stored we would get it all back. you never get back out of it what you put in. straight down the energy is absorbed quickly by a thud. this storage notion while it works for calculations to calculate how much force is needed to elevation side against gravity then again when the force of gravity is applied to going back down. In each case gravity is the driving force in the rock example. Hence the illusion of how we think about things to make our math work and reality. Its simply easier to splain it to kids when you dont have to get into all the special relativities of it.
Case in point if it in fact stored energy truly exists we should be able to push it off the cliff after removing all gravity and it should fall because of all that energy that was stored and we know it wont, it will merely levitate.

Now try that with a capacitor, charge it up, put your finger across it and if its a hv cap it will clean the flesh off your bones, no other force required.



the left side shows force of air v gravity, like a parachute, the right side shows the the same, little resistance to the force of gravity