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I must have misread what you were saying in your prior post, though I would have trouble reading it differently. I do however think “science fantasy” is a valuable scientific endeavor, since it allows us to explore the boundary conditions and unexpected results of the models that have been developed. Thanks for the cool video on how light “slows down” in a medium. If you watch it again there’s a bit of a catch, this page explains it in other words ( https://www.physlink.com/educa... ). As for your explaination of time dilation, I’ve never heard any physicists explain it that way. Here’s a great video on time dilation: ( https://m.youtube.com/watch?v=... )

What optical material has a refraction index of 1.003? According to this table, the closest one is liquid helium. Surely that is not the case.

Also keep in mind a portion of the berg is above water when it's solid. Even if the volume stayed the same, melting would still raise the sea level.

That is not correct. Here are a couple of explanations: http://www.physlink.com/educat...

OK - so how about http://www.genchem.net/thermo/... or http://www.physlink.com/Educat... or https://www.grc.nasa.gov/www/k...

None of them are talking only about heat engines - they carefully point out that historically, thermodynamics was all about steam engines. But nowadays, it's realized that the laws are far more universal than that.

Not one of them talks about "the triple of volume, pressure and temperature" - that stuff is a tiny, tiny subset of what modern thermodynamics covers. You're still back in the Victorian era of steam engines.

Anyway - I'm done arguing with you. I guess that 99% of other people here agree with me.

Airplanes and Television invented by Americans.

Okay, as long as I've got you on the line... :)

What's supposed to happen when negative and positive mass collide?

If I throw a tennis ball at a wall, it bounces off (and the wall recoils imperceptibly). If I throw a negative tennis ball at a wall -- or throw it away, causing it to move toward the wall, whatever -- what happens when it hits? It seems like it would try to "recoil" in the same direction it was traveling, maybe even giving the wall a "tug" instead of a "push" when it hit. \

Well, I already said negative matter is weird.

Robert Forward proposed that when positive matter and negative matter touch, they cancel each other out, and vanish:
  (+) + (-) --> 0 (vacuum)
The mass cancels, and you're left with nothing there.

Unfortunately, we know that this can't happen, because if it did, then the opposite reaction could occur:
  0 --> (+) + (-)
--vacuum spontaneously generating pairs of positive and negative mass. If this could happen, it would happen, everywhere, all the time. But it doesn't. So there are rules (presumably conservation laws) forbidding this from occurring.

But it can't move forward, because presumably negative and positive matter can't simply interpenetrate -- or can they?

Of course they can interpenetrate. The reason that you can't walk through a brick wall is because of Pauli exclusion: the electrons in your body can't occupy the same place (the same quantum state) as the electrons in the wall. But, whatever negative matter is, it's not electrons (nor any of the other particles that make up "solid" matter). So, yes, it would pass right through ordinary matter.

Space-time is bent by mass.
If light is truly massless and it can be concentrated to form matter and later destroyed by antimatter, there's your wave generator.
Good luck realizing that though.

References:
light creates mass
matter-antimatter annihilation destroys mass and creates energy

You can watch the sunrise on the Moon from right here with a telescope. Did you even ever just do that or do you prefer posting your teenage angsty space Goth crap instead?

http://www.physlink.com/education/askexperts/ae616.cfm

Fucking moron.

The conditions have to be JUST right. Lighting a cigarette around gasoline vapors will ignite, but a lit cigarette needs very specific circumstances.

http://www.physlink.com/education/askexperts/ae1.cfm

Why are things so heavy in the future? Has the Earth's gravity increased or something?

Actually, the Earth's mass increases slightly every time it captures a meteor. Plus, its rotation is slowing, reducing its Centrifugal force, so even if its and your mass stayed the same, a precise enough scale would show a constant increase in weight.

As another comparison an average grain of salt contains around 1.2x10^18 atoms verses this simulation's 5.5x10^11 particles. (source)

> Mach one is determined by air pressure primarily

No, no and no again. It is a function of air temperature.

Debunk that myth

Another famous example is the invention of television... those guys fought over the credit for a lifetime, and I quote: "Zworykin had a patent, but Farnsworth had a picture."

A plasma (or, more properly, an electromagnetic plasma) is a phase of matter that has enough energy for the electrons to [be] separated from the nucleus. It consists of independently moving electrons and nuclei...

Wouldn't it be impossible to have a plasma made from a molecule, especially a polar molecule like H2O? It's been a long time since high school and college chemistry, so please correct me if I'm wrong, but if a plasma, by definition, has enough energy to strip electrons from the nucleus of an atom, then wouldn't it also have enough energy to break molecules into their elemental constituents? Or are some molecular binding forces stronger than the electrical forces that bind electrons to nuclei?

which one is farnsworth and which one is rca so i know who to root for?

http://www.physlink.com/education/askexperts/ae408.cfm

ip law doesn't reward inventors. ip law rewards assholes with big pockets. as this case shows, ip law is a farce, its a way for big companies to waste a lot of money on lawyer whores

if you are the little guy who thinks that copyright is for authors, and patents are for inventors, you're a fool

ip law is for distributors and large corporations. real creators are screwed. stop being naive

in the name of the highest ideals of western democracy, fuck ip law, it should be actively undermined and destroyed by anyone with morality and principles. we can't work through our governments and legislators, they're all whores to the patronage system. its up to the common man to destroy the entire rotten edifice

i'm not talking about revolution or any such nonsense. i'm talking about piracy. i'm talking about hitting them in their wallets. with any luck, we can bankrupt the organizations that profit from the idea of "intellectual property", and thereby destroy the validity of the idea itself in anyone's eyes

aarrrrrrrrrrrrrrrrrr!!!

If you're willing to classify radioisotope decay as a form of "fission," then not only is it likely, it's highly probable.

http://www.physlink.com/News/121103PotassiumCore.cfm
http://en.wikipedia.org/wiki/Radioactive_decay

Ahh, math time excuse!

The Earth's rotation already slows by 0.022 milliseconds every year from tidal friction. A simple way to get a handle on the energies involved is estimating from the increase in the radius of the moon's orbit, about 3.84cm/year, which comprises the majority of tidal effects on Earth.

Throw that into the gravitational potential energy of the Earth/Moon system, and you end up with a net energy loss in the neighborhood of 7.59x10^18 joules/year-- about 241GW. (Wikipedia says 2.4TW, but I think the paper they cited slipped a digit.

So, a direct energy drain at around either twice or twenty times the installed wind capacity is making the earth's rotation slow by... less than 2.2 seconds per 100,000 years.

Planets are big. Arguing that a chunk of rock 12500km in diameter is going to be noticeably moved by our technology in the foreseeable future isn't very plausible.

In related news, most of the energy input for wind is solar, not tidal, and net solar energy input into the system is still net solar energy input into the system, regardless of where it goes.

There are plenty of actual obstacles to worry about in implementing alternative energy, there's no need to make up imaginary ones.

I would imagine the point of this is to have a reliable power source when the sun's not shining? According to Physlink the Lunar day/night cycle is 28.5 earth-days long. So, you would have about 14 days of darkness between 14 days of light. Not, perhaps, the best place for a solar power solution? That's not to say that Solar couldn't play an important role in providing a lot of additional power, but it's always good to have some kind of backup, no?

Nuclear seems more practical, for this particular application than, say, diesel, since a single fueling could provide power for years.

I've heard that if you stick wires in an apple you can run a clock on it.

So I guess this will be near some orchard :-)

"The observation is that if an hour were shorter, by a small amount, we would be more focused, and accomplish the same amount of work, but in less real time, thereby increasing productivity."

According to http://www.physlink.com/Education/askexperts/ae283.cfm:

if your ship goes at 98% of the speed of light and you take a one year journey, when you return to Earth five years have gone by

An 'hour' can only be shortened if you move everyone but IBM employees closer to the speed of light. 1 Earth hour for an IBM employee will be 12 Earth minutes for everyone else travelling at 98% light speed.

At the end of the Earth day, when the Earth clock shows 5pm, everyone else will go home jet lagged, having worked only 1 hour and 36 minutes - *reducing* their productivity by a factor of 5. However, everyone else will also live 5 times longer than an IBM employee, which is why IBM replaces retired workers using the H1B and L1 programs.

There are about 41253 square degrees in a sphere so one could subdivide a simple solid until it has around this number of faces to get an even distribution of directions. That wouldn't include roll though - 360 degrees of roll makes it about 14 million angles.

http://www.physlink.com/Education/AskExperts/ae445.cfm

The speed of electromagnetic waves is certainly known and is defined to be exactly 299,792,458 m/s in vacuum (same as the speed of light).

Don't mess about with neon or helium. The only reasonable contenders are nitrogen and argon, because they're both dirt-cheap. Little-known fact is that argon is the third most common gas in the atmosphere, even more prevalent than CO2, while neon is 1000 times as rare and helium lower yet (although that's not how we get helium.) Argon's perfect: completely inert (unless you have fluorine or chlorine gas and open sparks in your container, in which case you have bigger problems) and really inexpensive. Filling your entire bathroom with argon would cost like $5.

"One of the oldest proofs of the Earth's shape, however, can be seen from the ground and occurs during every lunar eclipse. The geometry of a lunar eclipse has been known since ancient Greece. When a full Moon occurs in the plane of Earth's orbit, the Moon slowly moves through Earth's shadow. Every time that shadow is seen, its edge is round. Once again, the only solid that always projects a round shadow is a sphere."

http://www.physlink.com/Education/askExperts/ae535.cfm

The Earth gains mass each day as a result of incoming debris from space. You may have even seen evidence of this activity in the form of a 'falling star', or meteor, on a dark night.

While the actual amount of added material depends on which study you look at, an estimated 10 to the 8th power kilograms of in-falling matter accumulates every day. That seemingly large amount, however, IS insignificant compared to the Earth's total mass of almost 10 to the 25th power kilograms.

In other words, Earth adds an estimated one quadrillionth of one percent to its weight each day.

This is similar to an experiment where people were made to wear lenses that turned everything upside down. After a while, they started seeing everything the right way again. Different I/O port but same phenomenon.

http://www.physlink.com/Education/AskExperts/ae353.cfm

Most steels are magnetic to various degrees. However, when designing some stuff that would be used in an MRI suite, I did some research and found that some grades of stainless steel - specifically, 300-series stainless steels (302, 304, 316, etc.) - are more or less nonmagnetic. They can't be used inside the bore of the scanner, but that's mostly because it screws up the uniformity or the magnetic and RF fields necessary for imaging. This was a handy discovery for me, because sometimes aluminum and plastics aren't strong enough, and titanium is a lot harder to work with.

I was going to just what you wrote was a complete piece of crap, but I did search before I rashly typed that:

http://www.physlink.com/Education/AskExperts/ae158.cfm

*Snipet*
The value evaluates to be approximately:

11100 m/s
40200 km/h
25000 mi/h

So, an object which has this velocity at the surface of the earth, will totally escape the earth's gravitational field (ignoring the losses due to the atmosphere.) It is all there is to it.
*/Snipet*(Bold is mine)

So while I guess you are theoretically correct, I'm guessing it's only really an issue if you are trying to launch a barn or other non aerodynamic object into space.

Hatta said: But since p=mv anything with momentum does have mass.
No. Logical fallacy. If p then q does not mean q then p. Ex: Boys have eyes. So, if a person has eyes is that personal necessarily a boy?

p = mv is true if there is mass that is moving. Without mass, given only that formula, there would be no momentum. But it is also true p = E/c. If an entity has energy it has momentum. The momentum can come from a mass with velocity or from energy. To say that an entity with momentum has mass because p = mv is not logical because the momentum may not have come from the entity having mass it may have come from the entity having energy. Photons have no mass but they do have energy.

Wikipedia - momentum - http://en.wikipedia.org/wiki/Momentum (scroll down to "Momentum of massless objects")

Wikipedia - photon: http://en.wikipedia.org/wiki/Photon
Planck's Constant and Energy of Photon - http://www.colorado.edu/physics/2000/quantumzone/p hotoelectric2.html
Relation of Photon Energy and Frequency - http://www.physlink.com/education/AskExperts/ae99. cfm

It is NOT a fallacy. Bowling balls DO fall faster than pillows, and EVERYONE knows it ;)

And for all intents and purposes, this is good enough for nearly everyone.

After all, noone except scientists need to know or calculate the fact that individual particals (or even items of similar size (mass) and weight (like two identical bowling balls) will fall equally.

http://www.physlink.com/Education/AskExperts/ae6.c fm?CFID=18326416&CFTOKEN=61672591

-- Sorry, but I am still a proud member of /. =:]

Umm... no... the Earth's core will cool when the residual heat from it's formation bleeds away, and the various radioactive elements that are responsible for heating it finish breaking down into lighter elements. Period.

I don't know much about physics in general, let alone quantum physics but I seem to recall hearing or reading that neutrons and protons "pop in and out of existence". Maybe I misunderstood what I heard.
However, if that's the case what makes it such an outlandish suggestion that the universe came about in the same manner (aside from the "nothing can come from nothing" argument)? Perhaps it's easier to imagine that the microscopic particles can pop in and out of existence because they seem so small to us. Is it naive of me to think that scale has such a role in our perception of possibility?
I just read this here:

Apart from the quarks that constitute the nucleons (i.e. neutrons and protons) (these are called "valence quarks") there also exists a "sea of quarks", which continually pop into and out of existence due to quantum fluctuations.

Can someone with a background in physics explain how this is possible?

The value c/10 makes sense. It can't be near C or 90% of C - because of this. If anything, either we will totally breach C by a factor of 2 , or will max out at c/10 or thereabouts.

I think the writer is assuming that we won't be able to breach C physically (as per current phyical laws) - which is understandable. Because if you're not talking physics, you're basically saying anything is possible - and even god could exist.

Liquids are compressible:
http://www.physlink.com/Education/AskExperts/ae15. cfm

Liquids are about as compressible as steel or silicone dioxide, and as anyone with a watch knows, the steel in a spring and quarts in a crystal is compressible.

With regular explosives, solid and liquids can be compressed by a factor of 2 to 4.

The term used is "modulus of elasticity", and the unit is "Pa".
For air at the surface of the earth it is something like 100kPa.
For liquids it is something like 1000GPa

"Depleted Uranium is 40% less radioactive than natural uranium"....

Depleted != non-radioactive.

Depleted != safe. Particularly when in .1 micron particles that are blowing around in a dry desert, and inhaled by everyone. "clothing is typically sufficient to protect an individual from beta rays", but that isn't going to help when many, many particles are inside you, trapped in your lungs.

Alternately, you can just spread your fingers and wiggle your hand in front of your face.

...it will remain upright at all times and you can balance your cellphone on a string. :) http://www.physlink.com/estore/cart/Gyroscope.cfm? SID=37

How true. The past is an artificial construct of the electrochemical reaction that is consciousness. Much like infinity...the sum total of the energy in the universe is N /= n+1.

In each Planck segment of time the universe moves forward and the past is gone.

Citations:

http://www.physlink.com/education/askexperts/ae281 .cfm

http://en.wikipedia.org/wiki/Planck_length

I've been needing some good moderation to compensate for the unusually large number of Overrated ones I've been receiving.

i am not sure if you all read Physlink.com but it is a great site. ANy ways they have been selling a Fule Cell Toy Car Build it your self kit. from their site: A Science Kit for the 21st Century! Endless hours of fun and learning as you assemble and experiment with a unique reversible fuel cell. This new Thames & Kosmos Fuel Cell Kit provides a playful introduction to one of the most significant technologies of the 21st Century. With this kit you can build a model car that actually runs on water! Now that we have your attention, roll up your sleeves and find out more through experiments and demonstrations you can do on your own, in a classroom or with friends. Fuel cells are one of the most promising means of producing energy in the future. Because they do not consume fossil fuels they are considered environmentally friendly. Automobile manufacturers are already experimenting successfully with this technology and it is widely believed that fuel cells will become the energy source for automobiles in the near future. With this unique kit, you can build your own experimental reversible fuel cell car to learn more about this energy source. With more than 30 experiments and demonstrations, provided either in the kit or on our web site, users will learn how a reversible fuel cell works to perform electrolysis as well as to create energy. The electricity required to activate electrolysis is created with a large solar cell included with the kit. During electrolysis, water is separated into hydrogen and oxygen and the resulting energy is stored as a gas. When needed, the gas is fed into the fuel cell, which then serves as the power source. The Thames & Kosmos Fuel Cell kit also includes a digital MultiMate which measures currents and voltage, allowing you to learn exactly what a fuel cell is and how it functions. The experiments and demonstrations explain the physics upon which this future technology is based. Experiments 30 Experiments include: How to build a solar-powered car; Effects of direct and indirect radiation; Characteristics of a solar module; Electrolysis and its effect on water; Oxy-hydrogen test; How to construct and load a reversible fuel cell; Decomposition of water in the fuel cell; Qualitative and quantitative analysis of gas in a fuel cell; How efficient is electrolysis?; How light influences electrolysis; Solar electrolysis; Fuel cell-powered car. Add your own experiments! Kit contains: Complete reversible fuel cell (hydrocycle system) Wire Motor Chassis Axle Gas collector 4 Wheels Solar panel with support Syringe Tube Digital multimeter Test tube Protective goggles Labels Bag of small parts for fuel cell Bag of small electronic parts Comprehensive lab manual with 30 experiments and demonstrations (Additionally required: 1 quart of distilled water) The kit comes with a 96-page, full color manual and experiment guide. Recommended for ages 12 and older. Price: $129.95 with free shipping! here check out the link: Fuel Cell Car Experiment Kit http://www.physlink.com/estore/cart/FuelCellCarExp erimentKit.cfm

Wow, that was the stupidest thing I've ever read...how did you make it through school?

Read this, grasshopper: http://www.physlink.com/education/askexperts/ae552 .cfm

If you ask me, we ought to just start leaving these pin art things everywhere.

Whenever I see one, I can't help but make a quick facial imprint!

Oh for goodness sake!
"The photons hitting the black side of the vanes will be absorbed transferring their momentum to the vane. Those hitting the white surface will be reflected transferring up to TWICE their momentum to the vanes.

1) In a vacuum: The above concept dominates and the white vanes trail the black vanes.

2) In a poor vacuum: the air on the black side of the vane gets heated and the air molecules give an extra "kick" to the black vane side overriding the photon momentum transfer causing the black vanes to trail. I.e. the air molecules transfer more momentum to the vane than the photons do."

Answered by: Pete Karpius, Physics Grad Student, UNH, Durham
from: http://www.physlink.com/Education/AskExperts/ae677 .cfm

Now if the vacumm version was in space with zero gravity and NOT fixed (like a giant paddlewheel in space), then the vanes would spin indefinitely and be propelled in a straight Newtonian line away from light sources. If there are a few light sources, (eg The Sun, reflection of the Moon etc), then you can use force vectors to plot its course and modify them with shades
Now, if you apply that to a lightsail ship, it would be possible to spin the craft as well. If it were large enough, then the spinning would create artificial gravity for its occupants.
There are other ways that rotary motion can be employed within the ship itself.

I'm wondering how 'any number of points' are sent to the software, and what it does with them.

Did anyone else get an idea for a DoS attack on one of these? :>

Funny you should ask this. Sagan said it in Cosmos, I just read that portion last night. From a quick Google search:
http://math.ucr.edu/home/baez/physics/ParticleAndN uclear/photon_mass.html
http://imagine.gsfc.nasa.gov/docs/ask_astro/answer s/960731.html
http://www.physlink.com/Education/AskExperts/ae180 .cfm
http://www.usatoday.com/weather/resources/basics/w onderquest/photonmass.htm
http://www.ibiblio.org/lunar/school/library/massph ot.html

Most texts I've read state simply that photons have no mass. Those that disucss the topic in depth usually indicate that most phycisists believe that photons do not have mass. Just because someone didn't have the same schooling/texts as you does NOT make them ignorant.

Oh, and for what it's worth, GWB was educated by Yale and Harvard. Too bad he didn't have the benefit of a quality education like one might receive in Texas.

Light moves, generally, at c.

The problem is though, that light can be slowed down. According to several sources, light can be slowed down, although they all seem to agree that a photon travels at the speed of light no matter what, just the absorption/release/re-absorption process can slow down how quickly it crosses a given distance.

There was a related article in November-- with evidence pointing towards a massive black hole at the center of the LMC. (The Milky Way's closest neighbor)

What is keeping the speed around 3.5 GHz? Is it the processor itself, or the electronics around it that can't be made faster? Or is there no demand for faster processors? (I can hardly imagine that!)

b) The whole reason why AMD outpaced Intel, was because they didn't go for raw Ghz, but instead used the existing power more efficiently, with consequently less wasted energy (ie heat)

c) Clock speed is related to the speed of light, or how far an electron travels in a given time. The higher the clock speed, the quicker an electron moves, and the closer each transistor has to be to be to each other in order not to waste the advantage of the faster clock speed. There are limitations as to how "close" you can get the transistors before quantum tunneling occurs and you get leakage between channels. More here.

Did you steal that UID, or have you been under a rock for the last 10 years ?

I'm not convinced. Satellite dishes and the lining in your microwave have a bunch of little holes in them as a matter of convenience. Having the holes allows:

1. To see through the material (to see inside a microwave).
2. Reduce costs (less material is used, the punched-out metal holes can be melted down and used again).
3. To let air or water pass through easily (so that water doesn't accumulate inside a satellite dish).

However, as far as I know, the holes in a faraday cage are not put there to boost performance. (Notice that newer, very small dishes don't have those holes.) Again it is a convenience. The rule of thumb (diffraction limit in optics/E&M) is that the holes must be smaller than the wavelength of EM radiation you are trying to affect. If the holes are that small, then the EM wave "sees" a continuous sheet of conducting material, and can't penetrate. But actually having a continuous sheet of metal would be equivalent, or even better. A sheet with holes in it will have a cut-off frequency where it no longer rejects/reflects EM radiation (when the wavelength reaches the size of the holes). A solid sheet won't have this cutoff. For instance, a solid sheet of metal even prevents visible light from penetrating (you can't see through it), whereas a sheet with holes... well you can (partially) see through it.

The site you quote is literally entitled " How to Block Microwave Mind-Programming Signals," and I seriously doubt it's credibility. A more lucid page explaining these effects is this one. The Wikipedia article also correctly states:

Practical Faraday cages can be made of a conducting mesh instead of a solid conductor. However, this reduces the cage's effectiveness as an RF shield.

For more information, pick up an Electricity & Magnetism textbook. AFAIK, as long as you create a uniform conducting shell, it will reflect all sorts of EM interference, and protect the interior.

You thought correctly!
http://www.physlink.com/Education/AskExperts/ae53. cfm
A common misconception is that the sonic boom is only produced at the moment when the plane actually 'breaks the sound barrier' (i.e. moves from subsonic to supersonic speed). Actually the sonic boom delineates the edge of the mach cone which is behind any object that travels at supersonic speed. So a plane actually produces a continuous sonic boom that travels behind it in a cone-shaped form.