Forgot your password?

Comment: Re:The $50,000 question... more energy out than in (Score 1) 315

by stevelinton (#48096977) Attached to: Fusion Reactor Concept Could Be Cheaper Than Coal

In fact we do. If you look at the corona of the sun, little bits of plasma get trapped in magnetic fields and heated to hot that fusion happens. Since the magnetic fields are shifting, they are not contained for long, but they are. By controlling the fields, we can get longer containment.

Comment: Re:The $50,000 question... more energy out than in (Score 1) 315

by stevelinton (#48096941) Attached to: Fusion Reactor Concept Could Be Cheaper Than Coal

You're confusing magnetic and inertial confinement fusion. The tiny gold capsules are inertial confinement -- you zap the capsule with a short and very intense burst of energy, compressing it and getting fusion until it flies apart. Essentially a very very tiny H-bomb.

In magnetic confinement you hold the a much less compressed but very very hot gas in place with magnetic fields while it fuses relatively slowly. Current experimental designs tend to run in pulses of a few seconds or minutes, but engineering refinements should lead to ones that burn continuously, with more fuel being added and "ash" (helium) removed.

As you make tokamaks bigger they get more efficient, because there is less surface for the energy to leak out of, compared to the volume of plasma. ITER is designed to achieve scientific break-even -- more power out of the reaction than is used to run the magnets etc. The next stage will be a reactor that achieves actual power generation -- more electricity out the whole plant than goes in. This is harder because or turbine inefficiency etc. Because of the scaling up thing, if these do produce useful power it will be gigawatts.

What UW have is a variation of the magnetic confinement setup, generating the magnetic fields in a different way. Their calculations suggest that it will scale up cheaper and efficient than the current favourite design (a tokamak), but this remains to be demonstrated.

Comment: Re:When can we stop selling party balloons (Score 1) 296

by stevelinton (#47870109) Attached to: WD Announces 8TB, 10TB Helium Hard Drives

Interesting. The last sentence on the Wikipedia page for helium:

"Helium is a finite resource and is one of the few elements with escape velocity, meaning that once released into the atmosphere, it escapes into space."

So how does that work?

At a given temperature the typical velocity of a gas molecule depends on its mass. The lighter, the faster.
Helium is the only gas molecule that is stable in the atmosphere and has a typical velocity near the top of the atmosphere that is faster than Earth's escape velocity, so it slowly diffuses up to the top and then is gradually lost to space.

Comment: Re:Why can't hydrogen cool? (Score 2) 55

by stevelinton (#47727565) Attached to: The Star That Exploded At the Dawn of Time

Basically the conditions (temperature, density, amount of ionizing radiation around) thought to apply, the gas would be made up of atoms that tend to simply bounce off one another when they collide. This doesn't change the total energy in random motion of the cloud, ie the temperature.

More complex atoms or molecules can interact in more complicated ways when they collide, so that part of the energy ends up as vibration in a molecule, or extra energy of an electron in an excited state. These vibrating molecules or excited atoms then relax back to their ground state releasing a photon and so actually cooling the cloud.

Comment: Re:Ummm, (Score 2) 105

by stevelinton (#42018303) Attached to: NASA Discovers Most Distant Galaxy In Known Universe

Assuming the astronomers are right, the way it happened is this:

About 420 million years after the Big Bang, this clump of gas formed into a small galaxy and emited a lot of light. At that time, about 1 billion light years away, and moving away at close to the speed of light was another clump of gas.

13 billion years later according to clocks on that other clump of gas, the light "overhauls" the other clump of gas, and is seen by Hubble.

There are other points of view that assign different numbers to some bits of this, but they all agree on the actual facts.

Comment: Re:How do they measure this? (Score 1) 76

by stevelinton (#41254455) Attached to: Florida Researchers Create Shortest Light Pulse Ever Recorded

It is EASY to create the world's shortest laser pulse: emit a single photon. It is monochromatic, coherent (so it meets the laser defninition), and has the shortest possible pulse. .

No, by cleverly combining multiple photons of different frequencies you can produce a pulse that concentrates its energy in a shorter timespan. Calling it a laser pulse is actually stretching a point a bit, it is triggered by laser light, but the pulse itself is not monochromatic.

Comment: True, but obvious (Score 4, Insightful) 201

by stevelinton (#41047743) Attached to: How Technology Might Avert an Apocalypse

It's true, of course, that there are many more apparent imminent catastrophes (AICs) than actual catastrophes, especially as we are still here to argue about it.
Some AICs arise from incomplete understanding, some from politically motivated woolly thinking and will go away if ignored. Some are real risks and we just get lucky. Others are partially mitigated by actions taken in response to the apparent threat (Y2K for instance). Some may be fully genuine threats averted by prompt action. Nuclear war between NATO and Warsaw pact in the 60s or 70s might be argued to fall into this category. CND and others successfully undermined the notion of "winnable nuclear war" and made sure that no Western politicians would risk nuclear war.

However, NONE OF THIS MEANS THAT THE NEXT ONE WILL NOT BE REAL. Probably it won't, but we can't just assume it isn't a real threat because the last one wasn't. We have to study each plausible threat, do our best to estimate the risk and where the risk appears significant, do what we can to mitigate it. The universe does not owe us continued existence, let alone continued civilization.

In order to dial out, it is necessary to broaden one's dimension.