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GravityLight: Generate light with gravity

gravitylight.org

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Re: GravityLight: Generate light with gravity

#111

Post by userbinator »

achr2 wrote: post #27

Years ago there was a similar 'potential energy to electricity' buzz and I was initially quite excited. Then I did the math on how much energy is actually available (even at 100% efficiency) from such a scheme. Spoiler - it's minuscule. E = mass x 9.81 x height So a 10kg mass at 2 meters can (@ 100% efficiency) provide 196 joules of energy. A modern cell phone battery has about 25000 joules. To charge said phone woul…

Also assuming 100% efficiently, 196 joules is enough to run a 1W LED for 196 seconds (3:16), or a 0.1W LED for 1960 seconds (around 32:40.) Not very bright, but still somewhat useful for illumination.

Re: GravityLight: Generate light with gravity

#112

Post by eggie »

blacksmith_tb wrote: post #10
scribscrob wrote: post #5

Earlier quoted context omitted.

It's amazing the amount of people who immediately cry hoax. Someone raised a good point about taking money from locals and bringing it to Europe/America/China, but clearly this isn't breaking the law of physics.

The original OLPC attempted to ship a pull-cord generator. Trevor Bayliss, of Freeplay radio fame, proposed a generator based on hoisting a weight on a branch of a tree. The principle is sound. As for taking money from locals, I would be surprised if kerosene was produced locally... and even if it was, this is a one-time expense, versus an ongoing outlay.

I worked at OLPC. We didn't ship any kinetic charging systems as the most reliable ones had a mean time to failure on the order of ~three full charges. The scheme was cute and captured the imagination of people in the developed west but is fundamentally unsound due to the cost of high precision, reliable manual chargers and their miniscule power output. In addition to yielding only several full charges before the $50 charging unit failed, each charge would require tens of thousands of revolutions of a hand crank. As wonderful as the laptop was I think it would be a very strange thing for a child to do when they could easily play with something more immediate.

In practice most of the laptops are charged like other laptops--- from national power grids. Those that aren't are charged from diesel generators and solar power.

Re: GravityLight: Generate light with gravity

#114

Post by jheriko »

ajuc wrote: post #45
Confusion wrote: post #39

Earlier quoted context omitted.

The fusion persists because gravity forces hydrogen sufficiently close together.

So gravity is a catalyst, not the energy source.

its a symbiotic relationship. stars exist generally at an equilibrium point where gravity is trying to make it collapse, but the pressure produced from the constituents pushing outwards balances it out.

this is because if something is collapsing from gravity it will stop once some other force is pushing out harder.

this explains a lot of phenomena and is a key piece of understanding the modern theories of stellar phenomena, e.g. via the pauli exclusion principle, why neutron stars can form during a supernova (from the extra inward pressure combining with the gravitational collapse exceeding the degeneracy pressure of electrons in the plasma)... its also why beyond a critical mass the collapse doesn't stop at all and produces a black hole.

in any case energy is always conserved... but the ultimate place it is being extracted from to power a star is the gravitational field. everything else, e.g. the nuclear fusion, the light pressure from temperature etc. is a result of that energy being transferred into the star as it forms and continues to evolve.

Re: GravityLight: Generate light with gravity

#115

Post by jheriko »

ajuc wrote: post #53
brianpan wrote: post #46

Earlier quoted context omitted.

The Big Bang came from....gravity?

Is this the science consensus? I thought it's one of competing unconfirmed theories?

i believe it is very much the consensus.

the FLRW model of cosmology, which has made numerous confirmed predictions teaches us that the big bang is a geometric property of space-time i.e. a consequence gravity, and particularly Einstein's field equation from general relativity.

Re: GravityLight: Generate light with gravity

#116

Post by Gravityloss »

imaginenore wrote: post #88
CyberDildonics wrote: post #80

Earlier quoted context omitted.

You can use it to read and it is free.

It's not free. It's a very inefficient way of converting food to human energy to humans lifting weights that in turn power the lights. If this is targeted at very poor people, food isn't cheap for them.

If you think about the methods of farming worldwide etc, they also use a lot of human labor etc because there's not enough sophisticated industry to run everything on solar charged battery powered robot tractors... So you have to accept a local optimum.

Reading for half an hour per day could have large payoff, compared to reading very little ever, because it's too dark.

Re: GravityLight: Generate light with gravity

#117

Post by Gravityloss »

jameshart wrote: post #89
Gravityloss wrote: post #61

Earlier quoted context omitted.

1 watt of led light would require 1 Newton at 1 meters per second. Assuming 100 kg is the highest practicable mass, so that's 1000 Newtons -> 1/1000 m/s for each watt. Assuming a height of 2 meters, you could operate a very dim 2 watt led light for 17 minutes. I think that's not practical.

Or, using the numbers provided for this actual product which exists, rather than a spherical LED on a frictionless plane, we raise a 12kg mass 1.8m and get a 0.1W LED light for 20 minutes. Do you think THAT's practical?

Ok, I confess to not reading the article, I was just reacting to the comment. That actually starts making a lot of sense.

Re: GravityLight: Generate light with gravity

#118

Post by jodrellblank »

dear wrote: post #47
mdturnerphys wrote: post #33

Earlier quoted context omitted.

If we're playing that game: - Human muscles get energy from food. - Food is or gets its energy from plants. - Plants get energy from the Sun. - The Sun's energy comes from gravity-forced fusion. So gravity :)

So by your logic fossil fuel is solar energy.

Fossil fuel is a solar battery; charged in a couple hundred million years, humans will drain it in ~500.

No wonder we're seeing exponential growth with that injection of stored energy into society. The industrial revolution is a coal-powered nitro.

Re: GravityLight: Generate light with gravity

#119

Post by CyberDildonics »

imaginenore wrote: post #88
CyberDildonics wrote: post #80

Earlier quoted context omitted.

You can use it to read and it is free.

It's not free. It's a very inefficient way of converting food to human energy to humans lifting weights that in turn power the lights. If this is targeted at very poor people, food isn't cheap for them.

Neither is kerosene. Many people reply based on their gut feeling, but that doesn't mean it lines up with reality. A chocolate chip cookie has enough energy for a person to go jogging for 20 minutes. No one is going to starve to death by lifting a weight every 20 minutes for a few hours at night. They might be able to lift themselves out of poverty if they stop paying for kerosene and read (or learn to read) in the time that they aren't working, which is likely at night.
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