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I'm reminded of the simplified version of the laws of thermodynamics: you can't win, you can't break even, and you can't quit the game. However, in the case of gambling, law #3 doesn't apply, since you can quit the game.

Most gamblers are in denial about the first two laws, which basically say that the casino comes out ahead but everybody else loses (on average). But some gamblers apparently get mod points, and don't want to hear that they're stoopid to blow money on this stuff.

How many examples are there of the opposite happening. Taking just energy, with no starting mass, and making mass?

Here's the link you need to CD Anderson's 1932 experiment using gamma rays

You might consider anything from the universe as a whole, to a small pond of water to be "isolated". Whether or not the universe of the small pond of water was disturbed by an outside force is pure speculation.

Nonsense. It's very easy to show that small ponds are affected by outside forces. As for the universe, the entire universe is believed to be a closed system and it will therefore, according to the second law of thermodynamics (which is of course a theory not an actual law) eventually rundown. This is called the Heat Death of the Universe. It has nothing to do with the fact that the Earth gets energy from the sun and that decreased entropy on earth is (over)matched by increasing entropy in the sun. Entropy increases in the overall system (the universe) but parts of it can show a decrease. Nothing at all would work if this was not true.

Oh, even one contradicted law should disproove a fact, even if the earth is NOT a closed system, what about the other laws? If I'm an alleged gangster with 4 alibi, and you disproove one, cant I get off on the other 3? Is a fact, a fact if it is contradicted by another?

You mean your claims about the so-called law of biogenesis and the so-called law of kinds? Creationist drivel is not an argument against science.

They bring up an interesting problem in the article about the difficulty of cleaning surfaces after a storm- the triboelectric charges wouldn't necessarily have anywhere to bleed off to. Since Earth's ground is relatively wet, simply sticking a copper rod into the ground provides a good path for stray charges to go. Unfortunately, in a dry soil like that of Mars, grounding rods may not provide the level of protection they might on Earth. On the other hand, the reduced atmospheric pressure and lowered breakdown potential might actually help simpler methods like the charge dissipators (so called "static wicks") on plane wings. Basically, as long as there is a sharp point to help field emission and concentrate the E field in a small volume of space, the excess charge is dissipated into the atmosphere.

One cu ft of air weighs .0807 lb according to http://www.physlink.com/Education/AskExperts/ae650 .cfm

So the aperture of the 17 ft windmill is 227 ft^2 and a 10 mph wind is moving at 14.7 ft/sec so 3337 ft^3 of air is moving over the windmill every sec. That's 270 lb of air evey sec.

Since E=1/2 m v^2, E = 29172 ft-lb/sec. I'm not sure if I got my mass conversion factors right but that's about 40 kW kinetic energy.

So until turbines get way more efficient this is probably something we won't have to worry about.

Basically, air is *heavy*.

You are so wrong.
http://www.physlink.com/Education/AskExperts/ae534 .cfm

Err. This probably won't help much, but I've seen this exact question asked, and answered on Physlink which is an "ask the experts" type physics board
.
Unfortunately I can't seem to find it again, or remember what the answer was, so you'll just have to take my word for it - though if I can track it down I'll paste a link in here later.

But I remember the answer basically stated that no, that scenario doesn't work. I think possibly it was because if the light is reflected perfectly, no energy is imparted into the mirror to push it, as photons have no mass, or something.. but I could just be pulling that outta my ass. It's ages since I read it, and I'm no physics expert.

...to refer people to more information on Bose-Einstein condensates (BEC):

BEC wikipedia page
BEC home page at Colorado
BEC at NIST
What is a BEC?

Ruby, Saphire, or maybe Quartz was the slowest material that was listed in my physics text (if I remember correctly). I guess I had to do one too many index of refaction problems in school.

I remember reading about Cerenkov Radiation back in school. Facinating stuff, but again, only possible when NOT in a vacuum. Google to the rescue, look at this readable description of Cerenkov Radiation if you are so inclined.

Actually, planes are pretty well protected from most lighting as you can see here: http://www.physlink.com/Education/AskExperts/ae568 .cfm.

It's actually reverse lightning that causes problems, though I can't find a link talking about that right now. Basically, the reverse, or positive, lightning is much more powerful (it feeds sprites and jets in the upper atmosphere) and thus can overcome conventional protection of planes.

Maybe its possible to travel faster then light then

the laws of thermodynamics say otherwise. The first law is the conservation of energy and hence mass in most cases (i.e you can't win). If two people exchange objects nothing is magically created, there is no possiblity of a win-win situation. Existing objects have just been redistributed. The second law is the entropy law and states that on average an process will result in disorder increasing (i.e. you can't break even). Even in a perfectly equal exchange both sides will lose the time and energy necessary to make the exchange and so both sides breaking even is not possible.

However in the real world exchange only takes place where someone is going to profit and so the exchange must always be unequal with one side losing so that other can gain. The mechanism through which this is accomplished is pricing. This is possible because the real world does not consist of a number of equal players exchanging goods as modeled by economists. Instead you have most people who have only one thing to sell, their labour. By forcing the price of labour to be well below the prices of the goods that can be produced using it, systematic unequal (and therefore profitable for one party) exchange can be maintained.

In a similar way exchange between the first and third world is based on pricing raw materials, fossil fuels etc. at well below the price of goods that can be produced from them. In both cases this results in net flow of wealth from the poor to the rich which you might be forgiven for mistaking for the creation of wealth, if you are a well off person in a rich country, and you don't look too hard. You might want to check out The Power of the Machine by Alf Hornborg if you are interested in learning more.

"Earth's atmosphere allows for the triple-point of water which we all should know is vital to our functionality as living beings."

Not particularly, unless you consider 0 degrees centrigrade @ 611.2 Pa (0.006 atm) "allowable" in earth's atmospheric conditions. Hint: people like to breathe, and having one's blood boil does not make for a nice afternoon picnic. Consequently, it seems that you were just wrong.

Perhaps you should review your "introductory chemistry course."

..And hey, I'm a moron for submitting that without including this link:

http://www.physlink.com/Education/AskExperts/ae391 .cfm

In following my last post, I came across this. Granted it is from a BA in Physics, but it backs up my point. http://www.physlink.com/Education/AskExperts/ae201 .cfm I will surely like to get your references before I make a personal judgement. On a side, this is an example of good use of this forum. Not just ripping on people (even though I started that way in my infite wisdom), but explaining and provided information for one to come to their own conclusions. Thanks!

Remember folks, turn your fine-structure constant ahead tonight before going to bed.

I surprised at the posters getting all upset about this type of device. Yes it would be rude to mess with people in a crowded place like a bar or whatever if its obvious they're watching it. But how is an open IR receiver any different from say an open WAP? It's their fault if they didn't think about the possibility of someone using it in a way they didn't envision.

There is a conceptual difference between gravitational and inertial mass. It is a curious coincidence that we don't seem to be able to detect a physical difference. More information on this is just a Google away. Also look for the Principle of Equivalence.

Plants' ability to generate energy has been optimized by evolution, so a spinach plant is extremely efficient, churning out a lot of energy relative to its size and weight.

From http://physlink.com/: As a side note, you may be interested to know many foods have naturally occuring radioactive isotopes present in them already. For example bananas and spinach have potassium 40.

Wow! Now we can have all those nuclear-powered gadgets the people in the 1950's thought we'd have!
Just one question: How long before someone figures out how to make it explode?

Statistics show that there are more feline fatalities between floors 3-10 then[sic] there are after 10.

I bet statistics also show that there are more buildings with top floors between 3-10 than there are buildings > 10. But what do I know?

That research was already done. Complete with pictures of dropped cats. These guys are just taking advantage of the previous research.

What Schrodinger equation are you looking at? The one I'm looking at is definitely NOT simple, and even less so to actually solve the equation.

Other way around.

Windows to the Universe

or

PhysLink

Well, the original experiment was done with sensitive equipment firing a single photon at the slits. Diffraction of the single photon was observed on the other side. Here's a link

So, while this is normal with light going through slits, it was assumed to be different photons going through each slit and diffracting.

With a single photon, the conclusion was that, somehow, the photon was going through *both* slits simultaneously and interacting with itself on the other side... there was behavior of 2 photons.

The "conclusion" was that it was the different quantum possibilities interacting with each other that was being observed. Of course with a laser pointer, you have more than a single photon, so it doesn't drive home the perceived effect.

You might not buy it, but with that original experiment, the explanation seemed more plausible/better defended than in this guy's experiment. But, I think he was trying to do it to bring that concept into people's homes... not just "prove" the existence of parallel universes.

No TV, was just one of those invention that was ripe, and therefor "invented" several different places and with several different people holding different patents different places.

Philo Farnsworth have come to fame because he was among the first, but without a patent, therefore "the little beaten inventor".
Here is story about at least two of the inventors even if it skips the american patent holders:

"Escape velocity is defined to be the minimum velocity an object must have in order to escape the gravitational field of the earth, that is, escape the earth without ever falling back." -Yasar Safkan, B.S. Phsyics Ph.D. Candidate, M.I.T.

If an object is in orbit it will not "fall back". It has escaped the earths gravitational field in the sense that the remaining effect of the field is no longer strong enough to reduce the altitude of the object.

where's my mod points?

"Escape velocity is defined to be the minimum velocity an object must have in order to escape the gravitational field of the earth, that is, escape the earth without ever falling back. [...] 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.)"

For the small of brain, the 11 km/s value applies only to unpowered shots (e.g. a cannon) launched from the surface of the earth. Rockets and other powered vehicles don't need to obtain escape velocity to obtain orbit.

And to put that in perspective, Earth escape velocity is:

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

So Mach 10 is almost a third of the velocity required to escape the earth's gravity.

See:What is escape velocity? for more info. for more.

As anyone who has taken high school physics should know, to get into orbit does not just require "going up." It requires reaching orbital velocity about 25,000 mph.
physlink.com

A scram jet could be used for part of an orbital flight from about 7 to 10 times the speed of sound. A rocket would probably be used before and after the scram jet, but there would be considerable fuel savings. Of coure once you are outside the atmosphere, a jet is useless and a rocket engine would have to be use.

Well this is "news for nurds."

As found in this basic article here,

Stars and planets form as a result of the gravitational collapse of accreting material. Any net translational motion of that initial material is accelerated as its radius of rotation decreases....

I'm no physicist... but i can assume that if this radius increases, yes, the days will be longer...
Another more detailed explanation of the planet's rotation can be found here... This second article more fully explains the earth's slowing rotation.

however, measuring this would not necessarily prove or disprove the claim, as the data needed would be immensly larger than the data available...
as an example, this text can be found in the second article... It should be very clear from Appendix A that the rate of Earth's rotation both increases and decreases across rather lengthy stretches of time. For example, observations are tabled for some 374 years (from 1623 CE to 1997 CE). Throughout the many years covered in this table, it is apparent that the length of the solar-day was a fraction of a second faster than 86,400 seconds about 41 percent of the time. It is equally apparent that the length of the solar-day was a fraction of a second slower than 86,400 seconds about 59 percent of the time.

as you can see... this type of fluctutation would happen, but it would be nearly immeasurable with any accuracy for quite a while...

They could have easily changed the orientation of the shuttle if the suspected a problem. Land based telescopes would likely be no good because
of the atmosphere tho. Spy scopes, if they bothered to ask, might have been a different story.

Would the atmosphere have been a problem? Seems there are several large telescopes that I've heard of which are built high up on mountains so even a cloudy evening doesn't hamper its use as it's above the cloud-line.

Plus there are amateur astronomy photos (can't find any links to some at the moment) online that I've seen taken by ground-based telescopes that get pretty detailed, down to making out the individual cabin windows.

So I don't think the atmosphere would play a big role in keeping NASA from getting ground-based photos of the shuttle.

The problem was with what would happen if they turned the shuttle over.

Flipping the shuttle over so Earth-based scopes could image it seems obvious. But there are important reasons why the shuttle flies upside down. Basically to protect the shuttle from space junk and micrometeriods and to also protect the crew and the shuttle from the radiation of the sun.

The maneuver would also take a some time during which the shuttle would make several revolutions around the Earth, definately exposing the craft and crew to the radiation and heat of the sun. Such a maneuver might even kill anything in the cargo-bay and thus end a majority of the experiments taking place on the shuttle.

Reading over the e-mails that NASA engineers sent around, they certainly thought there may be a problem, but I don't think it was ever considered to be a life-threatening emergency. Given that's the case, I doubt NASA would risk flipping the shuttle over and expose it to both space junk/micrometeriods and the sun and perhaps destroy its experiments. Not for what they probably didn't see as a major problem at that time.

It would seem that a particular radio station or advertizer could hack the system and bias the billboard by leaving a box of cheap battery powered FM radios by the side of the road (or a weak FM transmitter). With all those radios tuned to the same station it would fool the billboard into thinking that the cars where tuned to that station. Thus the billboard would leave the same ad up and log high ratings for the station.

Earth's escape velocity is about 11km/sec, while the velocity required to go from the surface of the moon to the earth is only about 2.3km/sec. Energy is proportional to velocity squared, so it works out to take only about 1/21 of the energy. (leaving the Earth/moon system entirely from the surface of the moon is somewhat more expensive, but still only about 1/16 of the energy cost as that needed from the Earth's surface.)

Even though you've found an answer, you may still want to read about "Planck time", which is the smallest measurement of time that has any meaning (under our current understanding of Physics, that is).

Wow, I've learnt how to answer my own questions..

Question

Is time quantized?

Asked by: Chris Ingram

Answer

I guess that the simplest answer to this would be: 'Yes, everything is quantized.' However, unfortunately this is one of the biggest problems in modern physics. No-one is really sure how it should be quantized but the idea of quantized time as well as quantized space and quantized gravity is part of the elusive theory of quantum gravity.

Some of the best minds in the world have been tackling the problem for years now. Einstein failed to united quantum theory with his own relativity, Richard Feynman couldn't do it (although QED was a definite step forwards) and even today some of our most famous physicists such as Kip Thorne, Stephen Hawking and Roger Penrose are still unable to unite quantum theory and relativity.

In answer to your question then. Yes, time is theoretically quantized and in an ultimate field theory it would be a quantized field much the same as the particle fields that we can already see in unified field theories. However, no-one has yet been able to come up with a consistent theory of space, time, fields and matter which shows exactly how time is quantized.

Answered by: Edward Rayne, Physics Undergraduate Student, Cambridge UK

Your understanding of Archimedes' principle is flawed. Perhaps *you* should try your little experiment. If that sounds like too much work, try researching your claim a little.

No you would end up measuring the planck time instead.

I would not necessarily call Philo Taylor Farnsworth the inventor of TV. Electronic TV, yes, along with transmission of TV signals (demonstrated in 1927), but Baird was the first to demonstrate a working "television" - a mechanical device, demonstrated in 1925. Farnsworth's used a scanning technique, much different in design to Baird's.

I think Baird was the first to get colour working (in WW2). There were many others too, such as Zworykin (invented similar things, parallel to Farnsworth), Du Mont (invented the CRT), and Nipkow (invented the scanning disk in 1884, the basis for mechanical TVs).

More info here and here.

-- Steve

Philo T. Farnsworth (the inventor of the television... )

The inventor of television is not necessarily Farnsworth -- there are several scientists with good claims on the title (including John Logie Baird, after whom the Logie television awards are named).

From this page:

"Any reaction that takes place will either result in the products becoming less ordered, or heat being given off. This means at some time far in the future, when all the possible reactions have taken place, all that will be left is heat (i.e electromagnetic radiation) and fundamental particles."

Sounds a lot like how I learned the early universe was like...

"No reactions will be possible, because the universe will have reached its maximum entropy. The only reactions that can take place will result in a decrease of entropy, which is not possible, so in effect the universe will have died."

So it will be completely stagnant? Not even gravity exists anymore?

John Logie Baird was merely one of a handful of people who claimed to invent the television.

Swann was hardly the first to work on the electric light bulb

mumble something mumble research mumble

In the end, does it really matter? Your native country hardly determines your ability to invent something.

Thanks for pointing out what should have been obvious to me. In my defense, I was probably reading an old textbook. You'd think the concept of extraneous solutions would occur to me, but I guess not encountering this stuff on a daily basis as I did in college is making me dim.

The planck length (taken by combining planck's constant, the gravitational constant, and the speed of light so that the units cancel out nicely) is the smallest length possible in this universe. There is no smaller unit of distance (or, at lengths such as this, space is discontinuous). Likewise, the time it takes a photon to cross a distance equal to one planck length is the planck time, and it is the smallest unit of time possible (i.e. - time is discontinuous). This is not news. See this blurb for a little more info.

I leave my machines running 24x7 - so I don't see how extra CPU cycles will make a huge difference to my power bill

Let's just look at the CPU. CPUs have millions of transistors (a Pentium 4 has ~42 million), and each transistor is an electronic switch. The transistor technology they use is Field Effect or "FET". The most common would be "MOSFET". To maintain the state of the switch as ON or OFF, the device holds a small charge (positive or negative depending on the device) and the charge acts to "pinch off" the channel for current to flow, or to open the channel, as the case may be.

While a transistor is just sitting there in a particular ON or OFF state, it uses very little electricity. However, to change the state, you have to either charge or discharge the gate. When you charge or discharge it, this results in a small but finite amount of current flow, and there being resistance in metal and silicon, this results in power being consumed (at a rate of the current squared, times the resistance). So a transistor that is constantly switching will consume power, but a transistor not switching will consume very, very little.

So, if you home computer is just sitting there doing nothing, then it isn't using most of the chip, and the transistors just sit there waiting for the next instruction to execute. However, when you're running SETI @ Home, the CPU is constantly crunching numbers, and the transistors are constantly switching.

If you want to see this yourself, run a temperature monitor on the CPU while it's not doing anything, and then when you run SETI@Home or DOOM. You'll notice that the temperature spikes when it's doing something, and this is just used up energy. If you have electric heat in your house, and live in a cold climate all year long, you may not see the difference on your power bill, but I don't think that applies to most of us.

False. You can compress a liquid, just not much. Think physics... there is space between the molecules (how else would they move).

link

Good idea, but not possible due to the fact that different aircraft have different avionics. As a direct result, any given RF emitter will interfere differently with different aircraft.

Another idea would be to turn the entire passenger cabin into a Faraday cage. A quick calculation for the mesh size:

Assume you want to block 900MHz wireless devices. The wavelength emitted is

lambda = c / f = 3e8(m/s) / 9e8(/s) = 0.33(m)

Ask a Star Wars fan about how Han Solo made a voyage in however many parsecs and prepare to boggle at the convoluted thought process behind the explanation.

I am not a Star Wars fan at all (though I used to be a casual enjoyer of the movies, before episodes I and II), but this point isn't as convulated or silly as you may think.

Remember Einstein's equation: e=m (more commonly known as e=mc^2)? You can drop the c^2 if you chose your units to be such that c=1, meaning that the speed of light is little more than a constant that converts between two sets of units that essentially measure the same thing. Indeed, physcicists have proposed that we adopt more natural units that clarify this relationship.

Distance and time are likewise the same thing (as becomes apparent when dealing with general relativity).

You could measure time in units that describe how far light travels in a given period of time. While saying "just give me 300,000 kilometers, I'll be right with you" is a little more verbose the "just give me a second," the two are, in terms of physics, identical. Alternatively, you could say something is about a nanosecond distant, i.e. that object is one light-nanosecond away from your current position.

The fact that we didn't understand the relationships between space and time, nor that between energy and mass, is why we've ended up with two essentially incompatible units for each (meters vs. seconds, grams vs. Joules) which make the e=m relationship, and the distance vs. time relationship, appear more complex than they actually are.

So, saying one made a trip in x parsecs (which is silly sounding and undoubtably resulted from George Lucas not knowing a thing about physics or the units he was tossing about) isn't really as silly as one would think.

What is silly is that we still have different units for distance vs. time, and mass vs. energy, when in each case they are one and the same.

There, now you've read a 'convuluted' explaination by someone who hates what Star Wars has become and was never a very ardent fan ... an explaination that happens to be true.

...for very small values of lightspeed

Huh? In a matter-antimatter reaction, 100% of the matter is converted to energy. Not 10%.

See more here

-T

IANAP[hysicist], and so I have some questions about this process.

What I know:

• Photons have energy
• Light waves have the property of frequency which we percieve as hue
• The energy and frequency of a photon are related by E = hf
• Energy cannot be created or destroyed

So, when light is converted to a higher frequency (shorter wavelength) where does the necessary energy come from? The shockwave? What about when it is converted to a lower frequency (longer wavelength)? Where does the excess energy go? If the conversion really is 100% efficient (I'm a bit skeptical of that claim), then just imagine the solar panels we could have; sucking up all the UV raining down on us and emitting a soft red glow.

Fascinating stuff. I've got to study more optics and electromagnetic physics.