The Official Cricketweb Science Thread!

[Top_Cat]

Well here's your chance, bys and girls. All science questions which you always wanted to know but were too afraid to ask. We've got a few white-coat heroes here so I'm sure we'll be able to come up with some decent between us. Ever wanted to know why the sky is blue or what the hell genetic modification REALLY is?

COME ONE COME ALL!

 

[scorpio]

fine you asked for it...

You are humans not able to lick their elbows...

 

[Top_Cat]

Because if we were able to tickle our funny bone with our tongue, we'd have people walking around laughing all day. God said, "Nope, can't have that!" and made it impossible.

 

[anthonysw]

If nothing ever sticks to TEFLON, how do they make TEFLON stick to the frying pan?

 

[Top_Cat]

They stick teflon on frying pans with the same stuff that sticks the 'smart arse' sign to your head.

Next stupid question..............

[Edited on 8/6/02 by Top_Cat]

[Edited on 8/6/02 by Top_Cat]

 

[anthonysw]

I have always been interested in the big bang. What actually can cause the explosion from nothing?? And at the point of singularity why do the laws of physics break down?



[Edited on 8/6/02 by anthonysw]

 

[Paid The Umpire]

Well, they are very good questions but the most important one is...

What is the meaning of life?

 

[The Argonaut]

42

 

[royGilchrist]

Singularity means zero volume but finite density (alomst infinite I guess), which doesnt reconcile with scientific laws.

Another question would be guys who dont believe in big bang, are they the ones who also dont believe in God? And if you believe in Big Bang does that mean u also believe in God?

 

[anthonysw]

Very interesting Roy.

 

[yaju]

Do blind see in dreams?

Why is the morning sun red?

Why is the sky blue?

 

[Kimbo]

how do scientists know that protein synthesis happens by the unzipping of dna, followed by the mRNA transcribing the information and the tRNA translating it and it being turned into amino acids in ribosomes in our cells.
my theory is that we have little protein fairies in our bodies, and when we eat food with protein in it they grab they process it so we can use it. much more beleivable :P

 

[luckyeddie]

OK. Let's try to answer some of the sensible ones.

How does TEFLON stick to the pan?
It's a patented trade secret, and if I let you lot know, DuPont would have my a** in a sling. Seriously, it's a question which has been asked many times on the internet, and one which has generated some interesting answers. Check out the following link :

http://www.psrc.usm.edu/macrog/ptfeidea.htm

What can cause an explosion from nothing?
You can't generate an explosion from nothing. You have to appreciate that a vacuum is not empty, and that before the Big Bang, the primordial state was not in fact 'nothing' but 'something' (possibly a lattice of dimensions or fields, undergoing 'quantum fluctuations'). We don't know, because we have not been able to produce a mathematical model which 'fits' closely enough.

and the linked question :

...why do the laws of physics break down?
They don't. It is our APPRECIATION of the laws of physics as we currently understand them which no longer fit. Again, we don't know enough. Our understanding of the physical laws of the universe are constantly being revised. Now when we understand more, you (on CricketWeb) will be the first to be told.

Why is the sky blue?
Easypeasy. It's all down to the scattering of light. Photons normally travel in straight lines, but when one hits a nitrogen molecule or another particle in the Earth's atmosphere, it undergoes a 'scattering' process, i.e. some of it's energy bounces off in a different direction. The actual direction is determined by the actual wavelength of the light, the size of the particle it hits and so on. For the makeup of our atmosphere, this effect is greatest in the shorter (blue end of the spectrum) wavelengths, and that's why the sky appears to be blue.

...and the sun red at sunrise and sunset?
Now in the early morning and late evening, the sun appears closer to the horizon. This means that in order for light to reach you from the sun, it has to pass through far more atmosphere. This gives plenty of opportunity for blue light and the other shorter wavelengths to be refracted away, leaving just the longer (redder) wavelengths to impact on your retina.

Incidentally, it is possible to get a partial 'green sunset'.

 

[luckyeddie]

Just copied this from the 'who is responsible for Global Warming?' thread.

Questions posed by Roy.

LE,

Im no physicist so I warn you, some of my querries would be a bit unfiriariting for you

Anyways...

-The explanation of the formation of Nova you gave, kind of got me confused a bit. I thought the formation of Black hole was like that i.e. hydrogen fusion resulting in explosions and this pressure keeping the massive gravity of a star in check, but eventually it all turns into helium and there is no pressure to offset the gravity and the star collapses onto itself. If the star is big enough the gravity close to the surface is so great that even light cannot escape, hence a black hole. Now Im confused between a black hole and a nova.

-Whats the difference between a nova and a super nova?

-You seem to explain things for a layperson like myself, so how would you explain the uncertainity principle, and if you could also explain the 'probability of the cat in a box' experiemnt (Schrodinger's I think)?

-Some really basic explanation of the suprestring theory would be great

I'll get back to them.

 

[luckyeddie]

What is the difference between a Nova and a Supernova?
A Nova is a star (usually a white dwarf) which suddenly increases in brightness by hundreds or thousands of times for a short while, before returning to its original brightness. Novas are found in binary star systems, and it is thought that the 'flaring' is caused by the white dwarf ripping material out of its 'normal' neighbour. This material (hydrogen) undergoes nuclear fusion within the intense gravitational field on the surface of the white dwarf, and it is the resultant radiation which we see.

A Supernova, on the other hand, is thought to be death throes of a massive dying star as it undergoes gravitational collapse. The theory is as follows : hydrogen fuses to form helium. When the hydrogen runs out, the helium fuses to form carbon. This in turn fuses to form oxygen, this fuses etc etc etc.
Each time the fusion process takes place, immense quantities of energy are released which tends to hold the star's substance in balance against gravity until, that is, iron is formed. Now in order to form iron in a nuclear fusion process, energy has to be supplied to the system. This energy is the heat of the core of the star.
Without the heat energy, there is nothing to stop the star collapsing in on itself. When this happens, a flood of neutrinos are released in a great explosion which blows the surface of the star into space. It is this blinding flash of material from the surface which we refer to as a supernova.

Black holes?
The material blown from the surface of a dying giant star remains visible for thousands or even millions of years. In many cases, nebulae are the remnants of supernovae.
The superdense material which remains after a supernova explosion is a 'Neutron star'. If it is dense enough to undergo still further gravitational collapse, then even light will not be able to escape from it. If it reaches this stage, it is then known as a Black Hole.

Hope this answers your first question, Roy. I'm goind for a bit of a lie down before I wrap my three remaining brain cells around the wonders which are Heisenberg's Uncertainty Principle.

 

[luckyeddie]

Another answer for Roy. Please note that Quantum Mechanics is not one of my strong suits. If anyone can add to the explanation, please feel free to do so.

... explain the uncertainty principle

Heisenberg's Uncertainty Principle states that "The more precisely the POSITION is determined, the less precisely the MOMENTUM is known in this instant, and vice versa".

What he is referring to here is subatomic particles, in particular electrons.

My first thought is that he could have actually reduced that principle still further, since momentum is mass times velocity. The mass of an electron is known and does not vary, therefore the momentum is directly proportional to its velocity. Consequently, Heisenberg's principle OUGHT to read "The more precisely the POSITION is determined, the less precisely the VELOCITY is known in this instant, and vice versa".

That's not an answer, is it? OK, I'll try again.

In order to determine anything (position, velocity, momentum) to do with a particle, I have to MEASURE it. Now, each measurement has some error built into it (you can never measure anything precisely). Fine so far? OK. Now, let's assume that our accuracy of measuring things is improving. Eventually, we become so good at measuring that we can say, to all intents and purposes, we are 'spot on'.
Now, we take our super-duper ultra-accurate Vernier calipers or atomic clock or whatever, and we introduce it to the system where we have our electron which is whizzing around. We get closer to the flipping electron until, eventually, we bump into it (disturb it really, and move it, so it's no longer where we thought it was). Not only that, we have also disturbed our measuring device too, but that's another story.
Maybe Heisenberg can help me find my car keys.

Only two brain cells left, now. Heisenberg v Erwin Schrodinger will have to wait.

Can't we have questions about biomechanics, so one of our other eggheads can have a go? Why is it always the physics and the momentum and the black holes and the quantum mechanics (Burhey!)?

I'm not touching self-replicating DNA with yours.

 

[Gotchya]

Okee here goes nothing......

When a physicist refers to a singularity he or she is generally referring to a quantity which is infinite. Specifically, a quantity which approaches infinity as another parameter goes to zero, such as

lim 1/X = there's nothing on my keyboard
X ->0 forinfinity!

It isn't true to say that all laws of physics break down at a singularity. You can imagine the problems though -- how do we interpret an infinite mass or infinite energy or infinite force? Usually we assume that there is some new set of laws or some new way of looking at the problem that makes the apparent singularity go away.(That is we have to change our perception of the problem)

Here's an example. You may be familiar with Hooke's law for the force exerted by a spring: F=kx where k is the tension of the spring and x is the distance it is stretched. Now write the equation as k=F/x. Written this way it would seem that if you compare the tension between any two points on the spring, it grows and grows the closer together the two points are. In fact, two points spaced infinitesimally apart seem to have an infinite tension! It's just a manifestation of the 1/x limit above.

But of course that's not true. If you really want to know what's happening at small distance scales you can't use the Classical physics behind Hooke's law. At some point x drops below the spacing between molecules in the spring's metal. Now Hooke's law no longer applies and you have to use atomic physics to explain the spring's properties. So in the large-scale theory (Hooke's law) there was no fundamental distance scale: x could be as small as you want. But at some point this law breaks down. In the small-scale theory (quantum mechanics and atomic physics) there is a fundamental distance scale: the atomic spacing. We would say that the singularity has been "resolved."

Most people worry about singularities involving general relativity: two examples being a black hole and the singularity that classical general relativity predicts was our universe at the moment it began. If you try to apply the laws of general relativity in these situations you will inevitably find the same 1/x singularities I've been talking about. How are we going to resolve these singularities? We expect quantum mechanics to do the job, since it is the theory that correctly describes physics at small distance scales. Unfortunately, while we have good theories of atomic physics, we don't real have a good theory of quantum gravity. Many of us think string theory will ultimately provide the resolution to these problems.

In short then, a singularity represents an infinity and we generally don't think nature is infinite. The problem arises from not having some kind of "floor" built into a theory that keeps you from taking the limit of 1/x as x goes to zero. The way out is to apply a new theory that has such a floor, such as quantum mechanics or string theory (quantum gravity).
Hope that answered some of ur questionz, as far as the matters of God and the big bang go, i could refer you to read Stephen Hawkings A brief history of time (although personally, i think he is out to prove that God does not exist, or even if he did he didn't have much choice in creating the heavens the way they are !!!)
apologies for any mistakes i may have made.

 

[luckyeddie]

I'm impressed.

And pointing people in the direction of "Lisa's robot buddy" (Stephen Hawking) is definitely the way to them interested in physics.

I think that your definition of a singularity could have been slightly better illustrated by using 'infinite mass, zero diameter' as an example, but what the heck.

Now, how's about tackling 'Fermat'? Then I can retire gracefully to third man.

 

[luckyeddie]

It is fitting that 'string theory' should be mentioned at this moment in time.

Paul Dirac, arguably the 'father' of string theory, was born on August 8, 1902.

 

[anthonysw]

What a great thread.

Very interesting stuff!!