speed is a bad way to think about travel
Lets for a moment forget about speed and realize It takes energy to bring two bodies within proximity.
As an aside lets observe this
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Lets for a moment forget about speed and realize It takes energy to bring two bodies within proximity.
As an aside lets observe this
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If there's a repulsive force between them, yes.
If there's an attractive force (such as gravity) between them, then no. The bodies will tend to approach each other on their own (like a falling rock near the earth), and rather than needing energy to bring them together, the reverse is true: you can actually extract energy from them as they approach each other (the rock has gained kinetic energy which you can use to do something.)
What does Maxwell's Demon have to do with the total energy of a pair of interacting masses?
-Gnobuddy
Boston dynamics is releasing some products next year, they might allow one to pre order your customized version depending on chores to be performed from the company website.
The building and construction industry might be the first to import these units. A contractor can substantially reduce his expenses by having four or more of these units together with caterpillar autonomous or other building a site to specification without waste round the clock with a solar power plant.
Soon people will pay for house construction the way they pay for cloud services. A drone surveys the site, you choose a design depending on pocket with the help of VR. Get billed*. Materials automatically scheduled using just in time. Equipment drives itself to site and voila in a few days you move into your new dream house.
The units could also be useful in an automated farm, where atlas can shovel manure and pick fruits while the spot can shepherd the flock.
Fully autonomous banks without human personnel will cut costs but then again to feed the humans the race of men might need to make things free like the air and the water
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Cat | The Future is Now - Driverless | Caterpillar
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*while money is still relevant
The building and construction industry might be the first to import these units. A contractor can substantially reduce his expenses by having four or more of these units together with caterpillar autonomous or other building a site to specification without waste round the clock with a solar power plant.
Soon people will pay for house construction the way they pay for cloud services. A drone surveys the site, you choose a design depending on pocket with the help of VR. Get billed*. Materials automatically scheduled using just in time. Equipment drives itself to site and voila in a few days you move into your new dream house.
The units could also be useful in an automated farm, where atlas can shovel manure and pick fruits while the spot can shepherd the flock.
Fully autonomous banks without human personnel will cut costs but then again to feed the humans the race of men might need to make things free like the air and the water
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Cat | The Future is Now - Driverless | Caterpillar
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*while money is still relevant
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money basics
Although the lifetime of money might be nearing an end lets talk a bit about its qualities
Money is a stream, spend as much as you make, hoarding money kills businesses, kills progress etc
If you take peoples money through real estate, taxation, medical care, goods industry etc give back that money by visiting the posh saloons, massage palours, five star hotels where these people work: buying commodities from the high end manufacturers where these people work: so that they may be able to pay you.
If a poor third world country is pumping its money towards you, open plants in it or employ its people or give them scholarships and handouts , that they may prosper and continue doing business with you
Smart countries do not let the money you have given them sit in the bank, no.They give it back as loans.
Although the lifetime of money might be nearing an end lets talk a bit about its qualities
Money is a stream, spend as much as you make, hoarding money kills businesses, kills progress etc
If you take peoples money through real estate, taxation, medical care, goods industry etc give back that money by visiting the posh saloons, massage palours, five star hotels where these people work: buying commodities from the high end manufacturers where these people work: so that they may be able to pay you.
If a poor third world country is pumping its money towards you, open plants in it or employ its people or give them scholarships and handouts , that they may prosper and continue doing business with you
Smart countries do not let the money you have given them sit in the bank, no.They give it back as loans.
No. In Newton's view, it is a force, not energy. In Einstein's more sophisticated view, gravitation is a manifestation of spacetime deformation caused by mass, which appears as a force. Once again, not energy.
-Gnobuddy
You are kinda sorta close, but force and energy are two different things.
I will get back to your ocean wave example in a minute. But first lets talk about force and energy: energy is force multiplied by the distance that the object feeling the force moved in the direction of the force.
If you lift a rock weighing 1 Newton (about the weight of an apple) vertically through a distance of 1 metre, you have now stored 1 newton-metre worth of potential energy in the rock. That potential energy came from your muscles, though, not from gravity. Your muscles in turn got chemical energy from your blood that they converted to kinetic energy to lift the rock. The chemical energy in your blood came from the food you ate. And ultimately, that food got its energy from the sun, which either grew the plants you ate, or grew the plants that fed the animals that you ate.
If you now let that rock fall, you can recover the energy you put into it when you lifted it - you might let the falling rock drive a nail into a piece of wood, for instance. The energy that drove that nail didn't originally come from gravity, though, but from your muscles, and the food you ate, and the sun that powered the growth of the food you ate.
Back to your example of ocean waves - the water is certainly moving up and down. Each time it moves up, it stores some potential energy. Each time it comes back down, that energy is delivered to all the water around it.
Where did that energy come from? The wind that created the waves. Where did the wind get its energy? Ultimately, from the sun, which drives the weather on our planet by warming some areas more than others.
Perhaps a very simplified analogy is a checking account. You can only get out the money you put in. Same thing with gravity - you can only get out the energy you put in in the first place. You can store some energy in a weight you lifted, or in moving waves, and you can get (at least some) of that energy back later. But you only get back the energy you put in (usually a little less, never more) - there was no free money in the checking account to start with.
-Gnobuddy
According to my old high school physics book:
A gravitational field can be described either in terms of force or in terms of energy.
Gravitational Field Strength (g) is the force per unit mass on a small object placed at a point in the field while Gravitational Potential (V) is the work done per unit mass to move a small object from infinity to that point.
The former is a vector representation of the field (since force is a vector quantity) and the latter is a scalar representation (since energy is a scalar quantity).
Both representations are equally valid in Newtonian mechanics.
A gravitational field can be described either in terms of force or in terms of energy.
Gravitational Field Strength (g) is the force per unit mass on a small object placed at a point in the field while Gravitational Potential (V) is the work done per unit mass to move a small object from infinity to that point.
The former is a vector representation of the field (since force is a vector quantity) and the latter is a scalar representation (since energy is a scalar quantity).
Both representations are equally valid in Newtonian mechanics.
I remember that definition too, and my textbook was careful to point out that gravitational potential itself, like electrical potential (voltage), is not energy. They way you find the gravitational potential at a point is defined in terms of the energy required to move a mass to that point from infinity - but the potential itself is not energy.
Electric potential (voltage) is defined in almost identical terms. The electric potential (voltage) at a point equals the energy required to move a unit electrical charge from infinity to that point. But voltage itself is not energy.
IMO, the key point for the purposes of this thread is that there is no energy in gravity itself, waiting to be magically freed by the appropriate magic device, as many people want to believe. However, as I said in my previous post, you certainly can store energy in a mass by moving it appropriately in a gravitational field, or get it back after you've stored it, by letting the mass fall. No different than compressing a spring - you can get back out what you put in, no more.
And about that word, "infinity" - astrophysicists, cosmologists, and people who work with interplanetary rockets set the zero point of gravitational potential at infinity (a mass would have zero potential energy if it's out in deep space infinitely far from all other masses.) This choice of zero potential makes elegant mathematical sense, but it means a rock sitting in your back yard has a vast amount of negative potential energy (and you would have to supply a vast amount of positive energy to lift it back to outer space, where it will once again have zero potential energy.)
In my experience, most people find that choice of zero rather confusing, and find it easier to think of zero energy as the rock sitting on the ground. With that choice, lifting it up from the ground gives it positive potential energy (rather than a wee bit less negative potential energy.)
We are allowed to set the zero point of potential wherever it is convenient - it is an arbitrary additive constant in mathematical terms, and what matters is the change in potential between one point and another. So the cosmologist who sets her choice of zero potential at infinity, and the plumber who sets his choice of zero potential at the soles of his shoes, will both agree on the amount of energy required to lift, say, a kilogram off the floor to a height of two metres.
-Gnobuddy
I find faster than light topics interesting, but with no answers, unfulfilling.
Look at this idea. If I missed the royal wedding, I could take off away from this planet above light speed, overtaking the events TV broadcast at light-speed . Then stop the car, and watch it when it catches up. This seems fine to me, but the more you know, the more you think of this as time travel. Which it simply isn't.
As someone said, having strong memory maps often stops you seeing new things. An amazing memory could make you as useful as google, so great at covering old ground. Perfect for getting the job. But still useless at breaking new ground. Probably retarding your ability in truth.
Someone that believes it's possible will crack it. Teams are certainly trying. It won't be a surprise when we manage to measure something with so little interaction with us that we have missed it until now.
Look at this idea. If I missed the royal wedding, I could take off away from this planet above light speed, overtaking the events TV broadcast at light-speed . Then stop the car, and watch it when it catches up. This seems fine to me, but the more you know, the more you think of this as time travel. Which it simply isn't.
As someone said, having strong memory maps often stops you seeing new things. An amazing memory could make you as useful as google, so great at covering old ground. Perfect for getting the job. But still useless at breaking new ground. Probably retarding your ability in truth.
Someone that believes it's possible will crack it. Teams are certainly trying. It won't be a surprise when we manage to measure something with so little interaction with us that we have missed it until now.
Hi Gnobuddy!
Obviously gravitational potential is not energy as my definition made perfectly clear. However it does define the gravitational field in terms of energy and that was my salient point.
When discussing gravitational potential, it is worth stressing that we are considering the work done by an external force per unit mass.
Moving an object towards the Earth at steady speed requires an external force to balance the internal field force i.e. the attractive force of gravity. In this situation, the external force is said to do negative work. This is why all points in the Earth's gravitational field have a negative gravitational potential.
When moving an object away from the Earth at steady speed the external force again has to balance the internal field force, but is then said to do positive work.
The choice of infinity as the zero of gravitational potential need not be confusing. Just like temperatures below zero on the celcius scale, gravitational potentials below infinity in the Earth's field are negative. The further below zero, the more negative the numbers become.
However, the work done by an external force to raise an object in the Earth's field is always positive. Compare this to raising a temperature from -30 to -20 degrees. This will require a temperature change of +10 degrees.
The simplicity of the scalar representation of gravity manifests itself via the idea of planet Earth sitting in a 'potential well'. For an object to escape from the Earth to infinity, sufficient positive work must be done in order for it to climb out of the well.
Obviously gravitational potential is not energy as my definition made perfectly clear. However it does define the gravitational field in terms of energy and that was my salient point.
When discussing gravitational potential, it is worth stressing that we are considering the work done by an external force per unit mass.
Moving an object towards the Earth at steady speed requires an external force to balance the internal field force i.e. the attractive force of gravity. In this situation, the external force is said to do negative work. This is why all points in the Earth's gravitational field have a negative gravitational potential.
When moving an object away from the Earth at steady speed the external force again has to balance the internal field force, but is then said to do positive work.
The choice of infinity as the zero of gravitational potential need not be confusing. Just like temperatures below zero on the celcius scale, gravitational potentials below infinity in the Earth's field are negative. The further below zero, the more negative the numbers become.
However, the work done by an external force to raise an object in the Earth's field is always positive. Compare this to raising a temperature from -30 to -20 degrees. This will require a temperature change of +10 degrees.
The simplicity of the scalar representation of gravity manifests itself via the idea of planet Earth sitting in a 'potential well'. For an object to escape from the Earth to infinity, sufficient positive work must be done in order for it to climb out of the well.
Hi friendly1uk!
If you haven't already done so, I recommend you read Poul Anderson's hard sci-fi classic Tau Zero, published in 1970.
Fated to accelerate ever closer and closer to the speed of light because of their star ship's damaged Bussard ram scoops, the crew members ultimately witness the collapse of the universe and its rebirth in a new big bang!
Maybe not entirely in accord with modern thinking on the evolution of the universe, but darned good reading nonetheless!
If you haven't already done so, I recommend you read Poul Anderson's hard sci-fi classic Tau Zero, published in 1970.
Fated to accelerate ever closer and closer to the speed of light because of their star ship's damaged Bussard ram scoops, the crew members ultimately witness the collapse of the universe and its rebirth in a new big bang!
Maybe not entirely in accord with modern thinking on the evolution of the universe, but darned good reading nonetheless!
Unfortunately, that wasn't clear to me from your post. My apologies for failing to understand you.
The sizable group of people who are always hunting for perpetual motion machines, "over unity" engines, and free energy, tend to believe that gravity equals energy, hence my attempt to make it clear that this is not the case.
I agree that negative numbers should not be confusing. After all, we were taught about them in elementary school.
Here's the thing: times have changed. Over the years, I have taught math to approximately 4,000 college students in the USA and Canada. And so I can state with confidence that at least 3,500 of them would have been quite confused if you asked them to subtract (-15) from (-14).
(The other 500 were engineering students, who had been pre-selected by their performance in entrance exams, and were of a much higher standard in math than the general student body.)
Perhaps things are better in the UK - I can only hope so, for the sake of the human race.
-Gnobuddy
Yesterday nobody knew you could light up a city with electricity, today electricity is almost a basic need, tomorrow who knows
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