Ask a physicist anything. (3)

[TerranceL]

Does one model a neutrino as a Dirac spinor or a Weyl spinor?

Yes.

 

[Wiccan_Child]

Does one model a neutrino as a Dirac spinor or a Weyl spinor?

One model's it as a Wiccan_Child spinor, superior to both Dirac and Weyl.

We can harness strong nuclear force through the nuclear reactions.
We can harness electromagnetism, in a billion ways.
We can harness gravity indirectly ( Hydroelectric dams)

Can we somehow harness the weak nuclear force?

The weak nuclear force holds quarks together, and is involved in flavour change. We could, in theory, extract energy from the radiation emitted from such changes (e.g., beta decay), but the energy would be minuscule. If could, however, be used to power nanotechnology, perhaps.

 

[Naraoia]

One model's it as a Wiccan_Child spinor, superior to both Dirac and Weyl.


The weak nuclear force holds quarks together, and is involved in flavour change. We could, in theory, extract energy from the radiation emitted from such changes (e.g., beta decay), but the energy would be minuscule. If could, however, be used to power nanotechnology, perhaps.

How much radioactive stuff do you need to get a reasonably steady supply of such energy for a nano-gadget? Would it be practical?

 

[Wiccan_Child]

How much radioactive stuff do you need to get a reasonably steady supply of such energy for a nano-gadget? Would it be practical?

How long is a piece of string? It depends on what kind of radiation is being emitted, what the power requirements are, etc. Though, perhaps, a hunk of gamma-ray emitting material that recharges a small ion battery...

 

[Naraoia]

How long is a piece of string? It depends on what kind of radiation is being emitted, what the power requirements are, etc. Though, perhaps, a hunk of gamma-ray emitting material that recharges a small ion battery...

I guess I was thinking of the unpredictability of decay, and whether a nano-size vehicle would have to lug around a disproportionately huge chunk of fuel to get a reliable input of whatever form of radiation. It's not so much the quantity that bothers me, but the reliability.

Then again, maybe I'm thinking on entirely the wrong scale...

 

[Wiccan_Child]

I guess I was thinking of the unpredictability of decay, and whether a nano-size vehicle would have to lug around a disproportionately huge chunk of fuel to get a reliable input of whatever form of radiation. It's not so much the quantity that bothers me, but the reliability.

Then again, maybe I'm thinking on entirely the wrong scale...

Well, there's only so many times a hunk of material can decay, so there'd be some lifespan involved. On the other hand, nanotechnology wouldn't require much power at all. And even if the power source was disproportionately huge, it'd still be tiny to our scales. Something 1nm long carrying a 100nm long power source would still be only 101nm long, after all.

 

[Maxwell511]

"Can you get electricity directly from a fusion reaction without having to heat to steam first?"

I am pretty sure that is what solar panels do.

Anyhoo, the short answer is: ...maybe. If you could get a fantastically conductive metal that became electrically charged when hot, that might do the trick.

Technically what you would want is some doped semiconductor (not a conductor).

This is a basic description of how you do it: HowStuffWorks "How Solar Cells Work"

But water cooling is such an efficient method there's not really much reason to change.

Agreed. But with the case of solar panels we are not building the reactor so we do not need to care that much about efficiency.

 

[TerranceL]

Ok, Mr Physicist I have a question: Is this awesome... or .... is this awesome?

YouTube - Kseniya Simonova's Amazing Sand Drawing

 

[Tinker Grey]

I'll butt in and answer -- It's awesome.

 

[catzrfluffy]

How many squirrels would it take to cover the world?

 

[pgp_protector]

How many squirrels would it take to cover the world?

1*


*But it would have to be spread real thinly

 

[TerranceL]

LOL

So wrong.

 

[Naraoia]

How many squirrels would it take to cover the world?

Can you dismember them? There's a lot of surface area packed up inside a squirrel

 

[catzrfluffy]

1*


*But it would have to be spread real thinly

What sort of butter knife would be needed?

LOL

So wrong.

Agreed.

Can you dismember them? There's a lot of surface area packed up inside a squirrel

Arghh! lol
For the purpose of the question I'll say no, they have to be whole squirrels.

 

[MorkandMindy]

How many squirrels would it take to cover the world?

With what?

 

[shinbits]

a fallacy of Kent Hovind is that light moves faster if comes from a moving object, like a the headlights of a car moving at sixty miles an hour, vs. the headlights of a stationary car.

but can anyone explain why this wrong? wouldn't it make sense that light would move faster in that instance?

also: why isn't gravity a factor in speeding up or slowing down the speed of light? shouldn't the light from the sun reach earth slightly faster than than light that leaves the earth and makes earth visible from space?

thanx for any help.

 

[catzrfluffy]

With what?

Heehee! Squirreliness.

also: why isn't gravity a factor in speeding up or slowing down the speed of light? shouldn't the light from the sun reach earth slightly faster than than light that leaves the earth and makes earth visible from space?

Bouncing off shinbits' thoughts... If gravity bends light, doesn't that make it reach somewhere slower? Or does something happen to compensate for the extra distance?
If absolute gravity bends light absolutely, what does that light become? Is there such a thing as absolute gravity?

 

[Doveaman]

God-Energy Theory

The God-Energy Theory was first proposed by the Prophet Isaiah in the 8th Century B.C. At that time the expansion/stretching of the universe was predicted by Isaiah based on the God-Energy Theory:

“I am the LORD, who has made all things, who alone stretched out the heavens...My own hands stretched out the heavens; I marshaled their starry hosts.” - Isaiah 44:24,45:12, 8th Century B.C.

This predicted expansion/stretching of the universe/heavens was confirmed over two thousand years later, in the 20th Century A.D, by Hubble’s Law and General Relativity.

In God-Energy Theory the kinetic energy in the expanding universe was predicted as being created from the (electromagnetic) force exerted by the Hand of God: “My own hands stretched out the heavens; I marshaled their starry hosts.” - Isaiah 45:12, 8th Century B.C.

Since God-Energy Theory has made a successful scientific prediction regarding the expansion/stretching of the universe, and Dark-Energy Theory is only an ad-hoc, gap-filler, place-holder theory signifying scientific ignorance regarding 74% of the universe, does this mean that God-Energy Theory offers a better scientific explanation for the expansion/stretching of the universe than Dark-Energy Theory does?

 

[Chesterton]

Bouncing off shinbits' thoughts... If gravity bends light, doesn't that make it reach somewhere slower? Or does something happen to compensate for the extra distance?

I asked a similar question once. If light is bent, it will reach somewhere later, but not slower. Just like two cars traveling from point A to point B; both cars can travel the exact same speed, but if one travels in a straight line, and the other a curved line, the one traveling in a straight line will get to point B sooner.

 

[Wiccan_Child]

a fallacy of Kent Hovind is that light moves faster if comes from a moving object, like a the headlights of a car moving at sixty miles an hour, vs. the headlights of a stationary car.

but can anyone explain why this wrong? wouldn't it make sense that light would move faster in that instance?

It would indeed make sense, but sadly the universe isn't prone to being sensible. Instead, light travels at a constant speed as measured in any inertial frame. You could be flying towards the Sun, or keeping a constant distance, and you'll measure the speed of light to be c in both instances. That in itself is a powerful test of relativity.

also: why isn't gravity a factor in speeding up or slowing down the speed of light? shouldn't the light from the sun reach earth slightly faster than than light that leaves the earth and makes earth visible from space?

thanx for any help.

Bouncing off shinbits' thoughts... If gravity bends light, doesn't that make it reach somewhere slower? Or does something happen to compensate for the extra distance?

I asked a similar question once. If light is bent, it will reach somewhere later, but not slower. Just like two cars traveling from point A to point B; both cars can travel the exact same speed, but if one travels in a straight line, and the other a curved line, the one traveling in a straight line will get to point B sooner.

That is indeed what happens, and it's called gravitational lensing. It's also the same effect that created this image:

Known as Einstein's Cross, it is a quasar that sits directly behind a the Huchra's Lens galaxy, such that gravity bends the quasar's light around it in four different directions: the central object is the galaxy, and the four objects around it are all the same quasar.

The following are also examples of this phenomenon, though in this case the light from a distant galaxy is warped into a ring around a relatively close star (or quasar, or what have you):

Gravity bends space such that light travels in a curved path. So, though it always travels at a constant speed c, it takes longer to reach us because it has further to travel.

Shinbits: gravity doesn't speed light up because the speed of light isn't dictated by gravity, any more than placing a magnet next to running water will make it run faster.

If absolute gravity bends light absolutely, what does that light become? Is there such a thing as absolute gravity?

Gravity is just the warping of spacetime by objects with mass, like a rotund child sitting on a trampoline. I'm not sure what you mean by 'absolute' gravity.