Slashdot Mirror

Well, in Penteli mountain, there are verified gravitational anomalies (there are also a hell lot more noted in the Hellenic space by physicists).


Who mods this crap up? "NATO was interested" and "gravitational anomalies"?!? WTF!? I thought we were nerds here...

"Gravity hills" are nothing more than optical illusions, Penteli mountain included. Check out this link for more information. (shakes head at the state of "science" here on Slashdot... double shakes at the tin foil hat wearing mods...)

Sorry, no - Casimir effect has nothing to do with C.
The Casimir effect is a measurable attractive force (really a repellant force from the opposite sides) between two parallel plates that are very close together.
According to QED, there is no absolute zero-energy vacuum - all space, no matter how empty, has energy that spontaneously forms particle/antiparticle pairs that pretty quickly annihilate (see Hawking Radiation, Quantum Foam, etc., Fenyman Diagrams, etc.). These pairs, frequently being wavelike, come in a whole bunch of frequencies.

So, place two plates parallel to each other and real close, and the only frequencies of waves that can fit in there are those with wavelengths that are whole-number fractions of the distance between the plates. On the outside of the plates, however, an infinite number of frequencies can occur, so there is a greater force/pressure outside the plates than inside, so they are forced together.

Interestingly, unlike gravity and magnetism, which follow an inverse-square law, the Casimir effect follows an inverse-hypercube (4th) law, so it gets much stronger than gravity or magnetism when you get really close, but falls off much faster. Source

-T

HERE

This site seems to say that "However, the total lifetime of a black hole of M solar masses works out to be 10^71 M^3 seconds".So it would depend on the size of the initial black hole - A black hole of mass of about 3*10^6kg (or a little more than 10^-24 the sun - say, the space shuttle) would last about a second. One a hundred times that size would last for a week - more than enough time to swallow the whole moon. The moon, at about 10^-9 of the mass of the sun, would take about 10^44 seconds to radiate away.

According to Steven Hawking, they don't actually exist -- the singularity never forms in a quantum mechanical universe.

This may be true, but it doesn't really affect the long-term behavior of anything less than a small distance away from the body.

Bear in mind that a black hole with lunar mass would have a tiny event horizon.

It would be a couple millimeters in radius - quite sufficient to fit atoms and such.

Given the amount of thermal noise in the solar center, it would be very hard for anything to "fall in" without being bumped out first.

That doesn't make any sense. Ultra-dense objects are less susceptible to thermal noise than light things like solar sails. Furthermore, the energy in any sort of "bumping" radiation would get eaten, and added to the mass.

In time, the hole might consume the sun, but my back of the envelope calculations suggest that it's far more likely that the pseudo-singularity would decay in a burst of Hawking radiation long before it consumed anything.

That's interesting. My envelope says this burst is more likely to happen roughly 5*10^48 seconds from the time the moon gets swallowed, and this is somewhat longer than your average power lunch. This page might help your envelope a bit. Remember, the exponent in that 10^71 has no minus sign.

To follow up on what you wrote above, the entire administration of the journal is nearly free. The only place money goes is the salary of one secretary for the journal's managing editor and mailing costs for those journals that actually still mail out hardcopies to reviewers. The journal editor rarely gets any money from the journal, and the referees never do as far as I can tell. In principle, the only legitimate reason for high subscription prices is small circulation.

Looking at actual subscription prices, journals published by research societies (like the American Mathematical Society, Documenta Mathematica), university consortia (Pacific Journal of Mathematics, Annals of Math), etc. (Mathematical Research Letters), are much cheaper than those published by commercial publishers like Elsevier and Springer (Inventiones Mathematicae). The journals seem to be run the same way, so traditional publishers must be skimming profits.

You can find data and the prices of math journal subscriptions at Rob Kirby at UC Berkeley and Ulf Rehmann at Bielefeld and John Baez at UC Riverside

You mean to say that no other mammal as caught on to this bipedal thing as yet? From the fastest cheetahs to the slowest sloths?

I don't know what he ment to say, but from a anatomical/physiologicl perspective there is noting strange with the fact that evolution/whatever places you somewhere on the scale from really fast to really endurant. Does this have an effect on how efficiently you utilize your energy sources? Oh, definitely! Unfortunately I can not seem to find a ref on this right now, but you can have a look at the difference in energy consumption between running and walking. I don't think I am extrapolating to much when think that different animals differ in energy efficiency.

The factors that determine the predisposition are numerous but some of them could be:

Anatomical construction
Well, just by looking at the cheeta and the sloth you would have a pretty good guess who is the fastest, wouldn't you? :)

Muscle fiber type composition
You might expect the cheeta to have extremely high concentration of Type II B in the skeletal muscles, but apparently they don't.
"All else being equal, one would predict that fast species should have a high percentage of fast-twitch glycolytic (FG) fibers in their locomotor muscles. Whether this prediction holds true is unclear. For example, the cheetah has 61% fast-twitch fibers in its gastrocnemius and 83% in the vastus lateralis muscle (Williams et al., 1997), but these values are no greater than found in some of the five species studied by Ariano et al. (1973; guinea pig, rat, cat, lesser bushbaby, slow loris). In human athletes, the vastus lateralis is known to vary from up to 70% fast twitch to as low as 15%, and sprint speed is positively correlated with the amount of fast-twitch fibers (Schele and Kaiser, 1982; references in Wilmore and Costill, 1994)."

Neurological innervation
To be honset I have no idéa what the difference is between the sloth and the cheeta when comparing muscle innervation. Nor is CNS differences in these species within my area. Off the top of my head I would say that you can expect to see some major differences in fiber recruitement pattern if you would study them.

On the other hand speed and endurance don't always contradict each other. Isn't biology fun? :)

I get a positive Crackpot Index just from this three line posting of his. And that's without even taking a shot at that "God gave us the secret to AI" website. I think my calculator might run out of digits...

From my perspective, the collapse proceeds ever more slowly. Although it never stops collapsing, I don't believe I would observe it actually turn into a black hole in a finite amount of time.

From the point of view of someone standing on the surface of the object, the reverse happens -- time in the universe outside seems to accelerate, to the point where the universe ends before the black hole is created.

Tom van Flandern is a well-known crank. He has done some good science in other areas, but his conclusions regarding the speed of gravity are just plain wrong. For corrections of van Flandern's mistakes, see this paper, and also this discussion.

The speed of gravity has been indirectly measured to be equal to the speed of light within about 1% accuracy, by observing a binary pulsar system (whose rate of inspiral due to loss of energy from gravitational radiation depends on the speed of that radiation); the 1993 Nobel Prize in physics was awarded to Taylor and Hulse for this work. Direct measurements will become possible once LIGO or one of its peer or successor experiments detect gravitational waves.

Tom van Flandern is a well-known crank. He has done some good science in other areas, but his conclusions regarding the speed of gravity are just plain wrong. For corrections of van Flandern's mistakes, see this paper, and also this discussion.

The speed of gravity has been indirectly measured to be equal to the speed of light within about 1% accuracy, by observing a binary pulsar system (whose rate of inspiral due to loss of energy from gravitational radiation depends on the speed of that radiation); the 1993 Nobel Prize in physics was awarded to Taylor and Hulse for this work. Direct measurements will become possible once LIGO or one of its peer or successor experiments detect gravitational waves.

It is more probable that gravity propogates at the speed of light. See here.

Wrong.

None of the green energy sources can provide the reliable energy that modern society demands. While this one will at least be very predictable, it will only be able to generate power when the tides are right, and that has no relation to peak power usage times. Sometimes the timing will be right, but the rest is wasted.


This is something that needs to be underscored; what is even worse is the magnitude to which green energy sources fall short. It's a myth; it's outright LIES at worst. Hydrogen is not an energy source, as many people - even professionals who should know better. Oil is effectively free energy, millions of years of solar power stored up and scooped off the ground - and it is going to take a HUGE investment in nuclear infrastructure to catch up.

Solar is an excellent possibility; however, research into efficient solar cells is lagging, and the energy efficiency of those cells is questionable. It doesn't do much good if you're producing cells using oil, and the cells take more energy to make than they will return over their lifetime.

That's also the problem with oil in the first place - there is more oil than will every be extracted from the earth. The problem is that the amount of energy to extract the oil is increasing, and once oil becomes an energy storage mechanism, and not an energy source, we are in big big trouble.

The unfortunately alarmist sites Die Off and the link in my signature are excellent sources for data backing up these claims - many of those studies are in fact funded for by congress.

"Green" energy sources are an interesting experiment but they WILL NOT solve the upcoming crisis from a shortening oil supply. The solution is to apply taxes to petroleum now and get that money into base research into solar cells, nuclear power, space based solar colletion, and other possibilities that offer energy densities that are a reasonable replacement for what we have now.

If you have energy, you have everything. Without energy, you have nothing.

Exactly, explained here .

Terror is not about killing people, it's about scaring the public and causing them to act a certain way.

The train bombing in Madrid, for example, though didn't kill a whole lot of people, was completely effective because the Spanish public immediately voted in a leader with a soft spot for terrorists,

Bullshit. Aznar was voted out because he had done everything wrong, and the bombings showed conclusively that all the things that had been done to make everybody feel so much safer was a complete failure. Furthermore, he was lying through his teeth about the events as they happened.

Fact is, Spain has dealt with terrorism for many years, and they know very well that you can't fight terrorism with military counterattacks. It simply does not work.

Compare with the US, which has had their tail behind the collective legs since 911, and running scared to abandon every freedom, which is pretty much the only thing the rest of the world has had reason to look up to US for. Great.

Have a look at a piece a friend of mine wrote. He's a native of Madrid, now studying in the US, and one of the most brilliantly intelligent people that I've met. Read it carefully.

And, oh, BTW, I've got karma to burn.... :-)

the distance that light emitted by a cesium 133 atom transitioning between the two hyperfine levels of its ground state will travel as it vibrates exactly 9,192,631,770 / 299,792,458 times

http://math.ucr.edu/home/baez/inches.html

Or rather, Art of Assembly. Possibly the best information on assembly language programming I've ever seen!

<a href="http://www.cs.ucr.edu/~beyert/articles/esccl ock.htm">key switch</a>

I wonder if my page is going to survive a slashdotting...

nah, it aint clickable. that is, until now

don't mean to gloat tim...but its a first post too!
oh yea!
clickable url
-Grump

Actually, HLA ain't nothing new, and if you've been doing any hanging out on comp.lang.asm then you've seen his name popping up on posts about every single day, several times per day, promoting HLA and helping newbies for years now.

I downloaded his book, "Art of Assembly Language" (avail. at No Starch, http://www.nostarch.com/) a couple of years ago before it had been published by No Starch and it's well written, still available for free either HTML , or PDF.

If you're using Windoze then it's definitely worth checking out the excellent RadASM assembly language IDE for Windows, which is itself written in assembly, and also supports HLA. Randall Hyde devotes a chapter somewhere, either in his book or on his site, I can't remember, to configuring and using RadASM.

One of the posts has questioned the value of teaching assembly to newbies, but I think there's a huge value for serious students. It's hard to appreciate garbage collection, for one, until you've had to pick up your own memory trash. But more importantly, most compilers out there output to some intermediary assembly language, and understanding the inner workings of your processor, your compiler and your own programs is one essential difference between being, well, a hack and being really, really good. There are other differences, to be sure, but that's one.

I haven't been a huge fan of HLA myself for various, and admittedly completely arbitrary reasons. But Randall Hyde has put megatons of work into his stuff, doing some extremely impressive things, and he's always ready and willing to be helpful on the newsgroups, so if you have an interest then I would probably go to his site and to comp.lang.asm before I went anywhere else. Anyone stands to learn a ton.

Actually, HLA ain't nothing new, and if you've been doing any hanging out on comp.lang.asm then you've seen his name popping up on posts about every single day, several times per day, promoting HLA and helping newbies for years now.

I downloaded his book, "Art of Assembly Language" (avail. at No Starch, http://www.nostarch.com/) a couple of years ago before it had been published by No Starch and it's well written, still available for free either HTML , or PDF.

If you're using Windoze then it's definitely worth checking out the excellent RadASM assembly language IDE for Windows, which is itself written in assembly, and also supports HLA. Randall Hyde devotes a chapter somewhere, either in his book or on his site, I can't remember, to configuring and using RadASM.

One of the posts has questioned the value of teaching assembly to newbies, but I think there's a huge value for serious students. It's hard to appreciate garbage collection, for one, until you've had to pick up your own memory trash. But more importantly, most compilers out there output to some intermediary assembly language, and understanding the inner workings of your processor, your compiler and your own programs is one essential difference between being, well, a hack and being really, really good. There are other differences, to be sure, but that's one.

I haven't been a huge fan of HLA myself for various, and admittedly completely arbitrary reasons. But Randall Hyde has put megatons of work into his stuff, doing some extremely impressive things, and he's always ready and willing to be helpful on the newsgroups, so if you have an interest then I would probably go to his site and to comp.lang.asm before I went anywhere else. Anyone stands to learn a ton.

Take a look at the sample programs.

...is something you should probably read. Link here.

Interesting project, but quite useless for us that prefer portability.

Expansion is severely reduced near massive objects - thus massive bodies do not expand with the rest of the universe, but at a tiny (or perhaps zero) fraction of the Hubble rate.

My source? I asked this in the context of the distance from the Sun to Pluto increasing over time of John C. Baez, who works on gravity and has written books on it, so I would say he is a good authority.

His response was that space does not expand (much) near massive objects - meaning even between the Sun and Pluto the expansion will not occur at anywhere near the rate it occurs in free space.

Yes, you have to learn general relativity to understand why. It is not simply that local (Newtonian) gravity overcomes it - I asked that specifically. No, I have not taken GR so I cannot give any further insight into this issue.

If the uniform expansion did occur uniformly between the Sun and Pluto, we could measure the Hubble constant by watching Pluto slowly receede from the Sun. It would be measurable using current values of the Hubble constant over years or decades. The effect is tiny beyond measure, apparently.

Note: I cannot recall if there is truely *no* expansion between the Sun and Pluto, or if it is just really small. I have thus opted for the really small in this post as it is the more conservative option.
_________________________________________ ________

Where did I fail to demonstrate a basic knowledge of GR?

The first poster has the right tack - list experiments verifying GR - all correct, all informative.

What google search should I have done?
this one

This lists, like the above post, gravitational lensing, gravitational timeshift, shapiro time delay, and precession.

I probably shouldn't have said 'little', perhaps I meant less, that is, less than the experimental evidence for quantum tunnelling, wave-particle duality, the second law of thermodynamics, but as the parent said quite correctly, that is entirely a matter of opinion, and I appreciate that comment. After all, what is the relevance of a 'lot' of proof, or a 'little' proof, if something is proven.

I 'invoke' string theory, because I think it holds too high a place in TOE study, and within mathematical physics in general. People have to spend many years gaining competence in all the areas which string theory covers, and are unable to specialise in any one of these areas. I probably shouldn't have mentioned it, as it was irrelevant - what I was trying to say was that there are certainly some branches of physics, or more precisely mathematics, that are very hard to find observable evidence for.

What factory should I go back to? Are you a gifted and talented chest-beating theoretical physicist? are you trying to be the creator of GUT? In my experience cosmology and GR attract a lot of arrogant physics undergraduates, who think their problem of universe origin is the most important problem of all.

Then again, physics students in general could be said to be arrogant, and it helps to study something that you think is genuinely important, so what's the loss?

take home message: first poster - left me informed, humbled, you - left me thinking you are a physics major worth little salt.

> Speed of time? Excuse me, but can I get some of what you're smoking? How would you define a concept like that?

You're right; "speed of time" is nonsense.

Maybe he's trying to say is that object's world line would become space-like rather than time-like. (Which is true.) Mathematical definition here. Some information about the consequences here. (Not much, though. But I'm too tired to find a better link and much too tired to think independently.)

Don't you mean imaginary mass?

The grandparent poster seems to be confusing things a bit. Let's try to clarify...

Except for the Lorentz transformation, the most important equation in Special Relativity theory is the Energy-Momentum relation:

E^2 - p^2 c^2 = m^2 c^4

(This is true for all inertial reference frames, and embodies the fact that the contraction of the energy-momentum 4-vector for a particle is an lorentz invariant. The Dirac equation, the Klein-Goron equation, and much of modern quantum field theory is rooted in this equation.)

Another important equation of SR involves the velocity:

pc/E = v/c

From these, we can see that

(i) if v < c (sub-luminal), then pc/E < 1, so E^2-(pc)^2 > 0, which means m^2 > 0. This case is true for normal, boring matter. Note that the converse is also true: m^2 > 0 implies v < c .

(ii) if v = c (luminal), then E = pc, and m^2 = 0. This holds for (massless) photons and gluons, and used to be assumed true for neutrinos. The converse ( m^2 = 0 implies v = c ) is also true.

(iii) if v > c (super-luminal), then m^2 < 0. Conversely, m^2 < 0 implies v > c . There is no known type of matter that is described by this case, but physicists have given such hypothetical particles the name "tachyons". One could say that mass is imaginary in this case, as m^2 < 0, but physicists rarely actually speak like this.

Anyway, the parent poster is right in correcting the grandparent poster that it is negative mass *squared*, not negative mass, that makes something a tachyon (v > c). But this

I think negative mass just makes you accellerate in the 'opposite' direction in a gravitational field. Feel free to correct me, though. It's been a while.

is not quite correct. From F=ma, we can see that it is true a negative mass would cause a particle experiencing a force in one direction to actually accelerate in the *opposite* direction! (Imagine that. You push something away with your finger, but it comes closer, increasing the force you're exherting on it, which increases the acceleration, ad infinitum. Physicists really hate thinking about the instabilities involving negative inertia, so we don't like to talk about negative mass at all.)

The problem with the parent post's suggestion is that althought this strange behavior would happen with an electrical force (such as your finger), it need not hold for gravity! In boring old Newtonian Gravity, a particle a distance r away from another mass M feels the force F = GmM/r^2 . But the acceleration would be a = GM/r^2, whether the mass is negative or not, because m completely cancels out of the equation. A similar thing happens in General Relativity, Einstein's theory of gravity -- the particle still follows the local geodesic of the spacetime metric generated by M.

I think that's what most people mean: you can't transfer information faster than c such that you can view it sooner than information travelling at c. Or are tachyons different?

To get back on the topic of information transfer, it's pretty clear that without nontrivial spacetime topologies (eg, wormholes) superluminal information transfer shouldn't happen except in the tachyon case. But does it really happen in this case?

The problem is that real life is quantum mechanical, wherein "particles" are described by evolving wavefunctions in a Hilbert space. A particle is a sort of propagating localized disturbance. The equation that should describe the propagation of a (scalar) tachyon is the Klein-Gordon equation. I quote the last paragraph from this discussion of the KG equation in the tachyon case:

The bottom line is that you can't use tachyons to

Some of your questions may be answered in this FAQ or this one.

This chap isn't exactly a physicist - but some of the "Crackpot Index" is applicable here. Nice set of criteria for determining plausibility:
Physicist John Baez's Crackpot Index
--- RK

QM gives a value for the cosmological constant which is 120 *orders* of magnitudes too big, see this link. I seem to recall that a prominent scientist named that fact the most glaring embarassing result of modern science, but I can't find a source for the quote, sorry.

To what extent does the "warping" of space near an object as massive as the sun affect this little spacecraft's orbital calculations? I know (but don't fully understand) that there are relativistic effects on Mercury's orbit that aren't described by pure Newtonian physics.

To what extent do the mission planners have to account for this effect? Can they even know for sure until they see what happens as they pass by Mercury those three times before orbital insertion? Or will the effect be negligible compared to the solar wind and other "normal" forces? The link above notes that Newton is only off by 43 arcseconds out of 5600, but it seems like even 0.77% could add up pretty quick.

Related site about physics
Jhon Baez site
especially interesting
Open Questions in Physics
Alternative approach - quantum gravity without strings Building Spacetime from Spin - this theory have some troubles - they arn't able to get a flat space-time as a classical limit of their theory, but now they are tryng apply the same approch to strings - a lot of math which I don't understand, but little part which I understand fascinating...

Related site about physics
Jhon Baez site
especially interesting
Open Questions in Physics
Alternative approach - quantum gravity without strings Building Spacetime from Spin - this theory have some troubles - they arn't able to get a flat space-time as a classical limit of their theory, but now they are tryng apply the same approch to strings - a lot of math which I don't understand, but little part which I understand fascinating...

Related site about physics
Jhon Baez site
especially interesting
Open Questions in Physics
Alternative approach - quantum gravity without strings Building Spacetime from Spin - this theory have some troubles - they arn't able to get a flat space-time as a classical limit of their theory, but now they are tryng apply the same approch to strings - a lot of math which I don't understand, but little part which I understand fascinating...

• Complete Planet
• The Invisible Web Directory
• Librarian's Index to the Internet
• INFOMINE

Actually, the Casimir effect means that you can have a free lunch thanks to quantum vacuum fluctuation. It's just an incredibly miserly, unfulfilling free lunch. I once did the math for this and found that to get 1 Newton of force, you had to put two uncharged, 1 meter square plates only 190 nanometers apart. So, even if ZPE exists, I can't see any practical way of extracting it, though some scientists have argued that ZPE is the basis of sonoluminescence.

Tunneling effect - a particle has a certain chance of overcoming a potential barrier even if it doesn't have enough energy to do so. Why can't a particle from within a black hole escape it similarly?

Accumulation of mass/energy. What exactly prevents a black hole from exploding, after accumulating enough mass - what makes them so stable?

Is it possible that the Big-Bang was an explosion of a huge black hole ?

If a half of a quantum-entagled (EPR) pair enters the event horizon, can it somehow be used as a "probe" ?

Tunneling effect - a particle has a certain chance of overcoming a potential barrier even if it doesn't have enough energy to do so. Why can't a particle from within a black hole escape it similarly?

Accumulation of mass/energy. What exactly prevents a black hole from exploding, after accumulating enough mass - what makes them so stable?

Is it possible that the Big-Bang was an explosion of a huge black hole ?

If a half of a quantum-entagled (EPR) pair enters the event horizon, can it somehow be used as a "probe" ?

Tunneling effect - a particle has a certain chance of overcoming a potential barrier even if it doesn't have enough energy to do so. Why can't a particle from within a black hole escape it similarly?

Accumulation of mass/energy. What exactly prevents a black hole from exploding, after accumulating enough mass - what makes them so stable?

Is it possible that the Big-Bang was an explosion of a huge black hole ?

If a half of a quantum-entagled (EPR) pair enters the event horizon, can it somehow be used as a "probe" ?

You are mistaken, take a look at this

Interesting, I thought that ever since the i80x87 line of chips you had 80-bit floating point. It even has support for many rounding modes. This is superior precision to the IEEE 64-bit spec.

Please also understand that the 6.2 GFlops you cite is a theoretical peak, while you state that your dual P3 does not even get 1 GFlop this was surely with some lame test you ran. The P3 using SSE can do much better than what you claim.

Are you a Sony fanboy by any chance :)

Ok. Biological evolution is a theory, and a pretty darn good one too. Talk Origins is a great place to start if one want to learn more about this part of real science. Evolution is a theory and fact. It is supported by the fossile traces as well as real life and lab observations. It's real science. Deal with it.

Creationism, on the other hand, is NOT a theory in any scientific way, shape or form. It explains nothing, it violates Ockham's razor by adding even more unexplained stuff, and it predicts nearly nothing. It is based on an old mythology, written thousands of years ago when not even the most wise men knew even a fraction of what we know today. When it DOES predict something, it's thoroughly debunked.

Introduction to the scientific method

I guess not only nerds come to slashdot.

Gravitational effects travel at the speed of light. Here is a decent explanation

Something that works like a very long tube filled with ping pong balls for example. Push one into one end and one pops out the other instantly, no matter how long the tube

why that won't work

I agree that one should be open to new ideas, but you might admit that coming forward with thousand of pages mixing well-known and original stuff and proposing this as the New Kind of Science is also meant to provoke the "old scientists".
Moreover, most people who out of the blue come up with the New Big Theory are wrong (or not even wrong). Typically, that has been practiced by entrenched organizations like churches for thousands of years is the first-line defense against critique (see Crackpot Index, item 32).

I haven't read the whole book since what read in it and about it gave me the impression that it is not worth the time (for me). I found this review interesting, since it pointed out (among other things) a (possibly fundamental) flaw in Wolfram's reasoning (his model of computation is classical, and seems to be in contradiction with the experimentally verified violation of Bell's inequality).

You're forgetting about HLA. I hear it's great for beginning ASM programmers (never tried it myself, so I can't give a review).

by Randy Hyde at Univ California - Riverside. To learn about assembly on 80x86 processors, check out the printed book, or download the text with a Linux or Windows point-of-view. It's written in a style that's not overwhelming to the novice.

by Randy Hyde at Univ California - Riverside. To learn about assembly on 80x86 processors, check out the printed book, or download the text with a Linux or Windows point-of-view. It's written in a style that's not overwhelming to the novice.