The Official Cricketweb Science Thread!

[vcs]

Yeah, the journalist probably doesn't understand the technicalities and is a bit too eager to write that a 12-year old has solved all the mysteries of the universe in a snap of a finger.

[Flem274*]

And that people, is why you do a BSc with journalism paper electives if you want to be a good science journalist.

[silentstriker]

Even then, its pretty shoddy.

[Flem274*]

Speak for yourself.

Though I would think postgrad certainly improves your understanding.

[silentstriker]

In what though? It's such a broad subject that you actually need to be interested in science and be proactive in learning stuff. BSc in biology does not make you qualified to write about the big bang theory. I know about a wide variety of subjects purely due to personal interests - there is no BSc or MSc or whatever that could give you that wide base. I mean right now I think parts of biology are my best subject, followed by physics, chemistry, and so on, but there're still holes as there'd always be, but you kind of need baseline knowledge of all fields to write intelligently about it, which is lacking. Not that I think there's an easy fix for that.

[Flem274*]

Originally Posted by silentstriker

In what though? It's such a broad subject that you actually need to be interested in science and be proactive in learning stuff. BSc in biology does not make you qualified to write about the big bang theory. I know about a wide variety of subjects purely due to personal interests - there is no BSc or MSc or whatever that could give you that wide base. I mean right now I think parts of biology are my best subject, followed by physics, chemistry, and so on, but there're still holes as there'd always be, but you kind of need baseline knowledge of all fields to write intelligently about it, which is lacking. Not that I think there's an easy fix for that.

The number one advice for any writer of any description; read, read, read.

You're right, BSc in biology doesn't qualify you to write about the Big Bang theory, but it does give you one area of expertise. You learn the rest by reading and learning. Read, read, read. I'm doing a double major in the geosciences, but that doesn't mean I'm not interested in various topics from physics to psychology, and I'm considering going into science journalism later on in life.

[PhoenixFire]

Reckon an MSc in NatSci (that's what I want to do!) could certainly potentially give you a very wide base across all the sciences if you chose the right modules.

[vcs]

I have a question.. when a system wants to reduce its entropy or keep it constant, it must give out energy. Right? For example, the human body has an internal temperature of 37 deg C and the natural room temperature at which the body feels comfortable is around 30 deg C. The explanation for the temperature differential is the fact that the cell reactions that keep our body's entropy constant are exothermic, and we constantly have to radiate some heat.

Now, anti-evolutionists are constantly objecting that the idea of evolution is contradictory to the IInd Law of Thermodynamics (entropy of a closed system must always increase). So how did complex life emerge out of a bunch of hydrocarbon building blocks? The explanation I've read is that when energy is pumped into such a system (from the sun), it can cause a reversal in the direction of the entropy arrow within the system, resulting in complexity arising from disorder. But there will be an overall increase in entropy, presumably at the source of said energy. So the total entropy of the system is still rising. Hence, we have the process of photosynthesis, which results in energy being trapped inside living chemical structures. So here, we have something absorbing energy to decrease its entropy? Isn't that supposed to be the opposite way to how things work? For example, when water turns to ice, it emits energy, and goes to a state of lower entropy.

What exactly is happening to the sun? Is its entropy increasing or decreasing as it gives out light energy? I think I'm missing out on something basic here. Would like someone to clear it up.

[Top_Cat]

There's actually quite a bit to answer there, tbh. In bullet-point form, hopefully I answer most of what you're asking but off the top of my head (feel free to jump in biochemists);

- the idea that a system always tends towards disorder really applies to closed systems and the universe as a whole
- in an endothermic reaction, it doesn't necessecarily follow that entropy of the system decreases and vice versa for exothermic reactions
- there is a general equation for photosynthesis but it's actually just an overall equation for a series of them, not all of which are light-dependent nor do they all result in an increase in entropy individually
- Even in a system of overall increasing entropy, there can be many reactions where the products are less disordered. Similarly, a system which becomes more ordered could have a heap of reactions where the result is more disorder.
- in my experience, enthalpy and associated concepts are far more relevant to talk about when understanding chemical systems. Entropy is a neat little concept which you learn about then, generally, forget.
- water melting into ice is actually an example of the entropy of a system increasing (the entropy of the outside world does decrease, though).

[vcs]

OK, found a very nice explanation that covers everything very nicely indeed. Even includes a nice back of the envelope calculation that clears up any objections an anti-evolutionist could make.

Robert N. Oerter, WAG. Thank you, whoever you are.

EDIT : Top_Cat, thanks for your post as well. Found out where I was going wrong. So the sun is losing some entropy for every bit of energy it radiates, while the universe is gaining it back steadily.

[PhoenixFire]

Sun is losing entropy because it is losing mass? Mass (in the same physical state and form) is proportional to entropy.

[blahblahblah]

Originally Posted by PhoenixFire

Sun is losing entropy because it is losing mass? Mass (in the same physical state and form) is proportional to entropy.

The Sun sends out about 4 x 10^33 ergs/sec of energy. Einstien's relation is E = m c^2. Thus the equivalent mass loss of all this energy loss is 4 x 10^12 grams/sec or about 4 million metric tons per second.

by a profeessor:

Gosh, that sounds like a lot. Well, it is and it isn't. On an
absolute scale it seems like a lot. It would impress us if we were
talking about something human-scale, like the yearly production of
steel in China or the rate at which marijuana is imported into San
Diego from Tijuana. But on an astronomical scale this is piddling.
Remember the Sun is, well, awfully awfully big. In fact it weighs
about 2 x 10^33 grams today. So if the Sun lost mass by radiation at
this rate it would lose 1% of its mass in (0.01)(2 x 10^33 grams)/(4 x
10^12 grams/sec) = 5 x 10^18 seconds, or about 160 billion years. The
best estimate for the age of the Sun is presently about 5 billion
years at most, so pretty clearly mass loss through radiation emission
ain't going to compromise that limit in the slightest. In fact, you'd
look pretty ridiculous even suggesting it, given the simple
calculation above which rules it out utterly.
Now, the Sun *does* lose mass at a much higher rate through another
mechanism, the Solar wind. This is the result of light pressure on
the Sun's atmosphere blowing off particles at a high speed, so fast
they escape the Sun's gravity field and fly off into space.
Astrophysicists actually believe the Sun may have lost quite a big
chunk of its mass (like 20%? I am unsure of the numbers) in its youth
during the so-called ``T-Tauri'' phase, when the Solar wind was
immense. Probably the Solar wind puts a more stringent limit on the
Sun's age than radiation emission. But it is still not going to mean
the Sun was more than a couple of percent bigger in its youth than it
is now.
And now let's tackle the other problem here: how big must the Sun
get until it becomes too close to the Earth? Well, the Sun is 93
million miles away. It's present radius is about a quarter of a
million miles, I think (within a factor of two or so). So the Sun
would need to increase its radius by a factor of 200 or so to become
close to the Earth. That would correspond to increasing its volume
and hence mass by a factor of 200^3 = 10,000,000. I can't think of
any obvious mechanism whereby the Sun would have lost 99.99999% of its
mass since it's birth, so that when it was young it was the size of
Earth's orbit.
You should probably be aware that there is no evidence whatsoever
that argues for a young Earth. All the evidence argues quite the
other way. In fact, the thesis that the Earth had an origin at all --
that it has not always been here -- is what needs justification to the
skeptical mind. I don't know about you, but when I look around me the
Earth is the one thing that does not seem to change one iota over
time. The mountains I climbed in my youth don't look one particle
different today, 30 years later, which I wish I could say about the
face in the mirror. The contours of the coast of England look
precisely the same to me in photographs from orbit in A.D. 2000 as
they do on the maps of William the Conqueror drawn in A.D. 1066. Why
on Earth (so to speak) would I even conceive of the idea that the
Earth has changed drastically over time, that in fact it was once not
even here? The idea seems silly, on the face of it.
From this point of view, it would seem someone who argues that the
Earth came into being relatively recently has A LOT to explain, and
the person who thinks it has pretty much always been here has the
luxury of relying on the fact that this tentative conclusion is
supported by every fact our senses report to us.

[vcs]

Originally Posted by PhoenixFire

Sun is losing entropy because it is losing mass? Mass (in the same physical state and form) is proportional to entropy.

I think as long as the sun has enough fuel in its core, it is not gaining or losing entropy either.

If we go right back to the Big Bang, apparently at time zero everything was in a state of extremely low entropy when it was compressed together in such a small volume. Then when expansion was undertaken, the tiny irregularities in the surface of space led to matter being distributed in clumps as the universe cooled rapidly. Then these clumps started being pulled together by gravity, and formed stars. Stars keep themselves in a state of equilibrium by producing just enough energy in their core through nuclear fusion to counteract the contracting effects of gravity.

From wiki :

The fusion rate in the core is in a self-correcting equilibrium: a slightly higher rate of fusion would cause the core to heat up more and expand slightly against the weight of the outer layers, reducing the fusion rate and correcting the perturbation; and a slightly lower rate would cause the core to cool and shrink slightly, increasing the fusion rate and again reverting it to its present level.

As they gradually run out of fuel and become white dwarfs, presumably their entropy will go down.

The other interesting thing there is :

The power production by fusion in the core varies with distance from the solar center. At the center of the Sun, theoretical models estimate it to be approximately 276.5 watts/m3, a power production density that more nearly approximates reptile metabolism than a thermonuclear bomb. Peak power production in the Sun has been compared to the volumetric heats generated in an active compost heap. The tremendous power output of the Sun is not due to its high power per volume, but instead due to its large size.

So we're effectively being sustained by a huge compost heap.

[vcs]

While googling some of the above stuff, every now and then, you come across some absolute nutjob theories as well. This is comedy gold.

[Teja.]

Originally Posted by vcs

While googling some of the above stuff, every now and then, you come across some absolute nutjob theories as well. This is comedy gold.

I don't know what entropy is yet, I still lol'd at 'Biological Theory of the Sun'