Timeless clock

[Paul's Here 0]

A clock that will last forever: Researchers propose a way to build the first space-time crystal.

Imagine a clock that will keep perfect time forever, even after the heat-death of the universe. This is the "wow" factor behind a device known as a "space-time crystal," a four-dimensional crystal that has periodic structure in time as well as space.

[ruveyn ben yosef 0]

If the laws of thermodynamics are true, the cosmos won't last forever. If the cosmos is taken as a closed system then according to 2LOT its entropy will tend toward a maximum value at which point no more free energy to do mechanical work exists. So how can the clock keep on going forever?

ruveyn

[PhilO 0]

Someone will just have to last longer than the clock to find out.

[Carlos 0]

If the laws of thermodynamics are true, the cosmos won't last forever. If the cosmos is taken as a closed system then according to 2LOT its entropy will tend toward a maximum value at which point no more free energy to do mechanical work exists. So how can the clock keep on going forever?

ruveyn

Applying thermodynamic principles to the universe as a whole is fishy. I remember being at a conference recently and seeing a lecturer demonstrate that you can't show that galaxies or the universe is size-extensive in the same way that you can prove some isolated systems are.

[Carlos 0]

This is the speaker's fascinating paper:

http://www.annualreviews.org/doi/abs/10.1146/annurev-physchem-032511-143718

[Carlos 0]

This is the speaker's fascinating paper:

http://www.annualrev...m-032511-143718

Basically in the paper he analytically shows that the energy density of a an infinite lattice of particles is only finite when the interaction energy decays monotonically as 1/r^n, where n>3. The gravitational potential decays as 1/r, and therefore the energy isn't size-extensive for galaxies or the universe as a whole, and thermodynamics is no longer validly applicable.

The Hartree-Fock energy of a quantum-mechanical system though is size-extensive.

[ewv 0]

If the laws of thermodynamics are true, the cosmos won't last forever. If the cosmos is taken as a closed system then according to 2LOT its entropy will tend toward a maximum value at which point no more free energy to do mechanical work exists. So how can the clock keep on going forever?

The article claims that it does not require or produce external energy because it is a frozen pattern of rotating charges in a static magnetic field that remains in the quantum mechanical ground energy state, analogous to a superconductor but with the special feature of a spacial symmetry that traps the charges.

[ruveyn ben yosef 0]

This is the speaker's fascinating paper:

http://www.annualrev...m-032511-143718

Basically in the paper he analytically shows that the energy density of a an infinite lattice of particles is only finite when the interaction energy decays monotonically as 1/r^n, where n>3. The gravitational potential decays as 1/r, and therefore the energy isn't size-extensive for galaxies or the universe as a whole, and thermodynamics is no longer validly applicable.

The Hartree-Fock energy of a quantum-mechanical system though is size-extensive.

Do you know where I can get at the technicalities without paying $20.00?

ruveyn

[PhilO 0]

One of the authors of the paper, So Hirata, gives his email address: sohirata@illinois.edu. He might email you a PDF of the paper if you ask him.

[A=A 0]

Not quite as epic in scope but.... another major clock / time measuring project.

Clock of the Long Now

http://longnow.org/clock/

[A=A 0]

Another crude time measuring device that was recently erected along the River's Edge Trail in a Great Falls Montana City Park.