Ask the scientist thread...

[KSoDBartman]

I'm a bit of an amateur scientist, as some of you may have figured out from a few of my posts. I love answering science-type crap, and I know that many people out there are curious about the very things I love to study. Given that, I figured I'd fire up a thread where y'all can ask questions and I'll try to answer them. (If anyone else wants to jump in and answer some stuff, I won't mind that at all; after all, I'm not totally omniscient!)

My specialties:
High-energy physics (the sub-atomic type)
Astronomy and cosmology
Kinematics (the physics of motion)
Low-level chemistry
A little structural & aerospace engineering

So, fire away!

[Fredfredson]

Cool :wave

I've been trying to find the rate at which the Earth's orbit is shrinking I wanted to use it to calculate what the Sun would look like 1,000,000 years from now. It occurred to me that since the orbit is shrinking that the apparent size of the Sun (Solar conditions being assumed to be the same as now) would be larger than now.

Would the decrease in lunar orbit over time compensate for the apparent size during an eclipse at that time?

F
:pooter

[KSoDBartman]

I've never heard that Earth's orbit is changing significantly, but the Moon's orbit is. However, it's slowly getting farther away from us, at the rate of a few centimeters per year, not closer.

I'll poke around and see if I can dig up anything on changes in the Earth's orbit, but off the top of my head I doubt there's anything conclusive on it, since the Sun is so big and the Earth's orbit is also, any minute changes would seem hard to detect.

[KSoDBartman]

Also, if anyone else wants to claim the label of "scientist," just list up your specialties and invite the pain! I don't want to be the only one getting the punishment!! :p

[Dave]

Francois might. Although strictly speaking I shouldn't vouch for him.

[KSoDBartman]

Y'know, he was first in my consideration of people who might join the Dark Side of Science in this foray into education.

[Anonymous Idiot Savant]

What's the maximum distance a human fart can travel, assuming it's bare assed?

Also why does the smell from some farts linger in the area while others do not?

Along that same note, why do some farts seem to follow you around?

[KSoDBartman]

Are there any real questions?

[Anonymous Idiot Savant]

Actualy, those were real questions but, I'll try and think of something a little more "standard" for you.

[Anonymous Idiot Savant]

OK, I've got something. Since you love science stuff I'm sure you've heard about the governments recent crackdown on scientist who study dangerous pathogens.

They have to go through so much paperwork now that some have abandoned their studies. This is of course being done as a counter-terrorism measure.

But as one scientist pointed out, you can find many of the organisms on the list in nature.

Speaking as a scientist, what's your opinion?

[Ms Digabit]

anonymous should try this site for windy answers.....
http://www.studentfreestuff.com/facts_on_farts/offers.html

anyway..some questions for the resident scientist.....
As the Hubble telescope reaches the end of its tour in 2005, and as the technology is 15 years or so old, are there any plans to make another 'scope? if so, what improvements can they make on the Hubble, and how much further afield would they hope to be gaining?, is the technology any more advanced to make the new 'scope quicker to reach a point where the Hubble retired? or would they just be covering the same old path?

I dont claim the label of scientist, but am trauma specialised,i dont mind answering these types of issues...
kinematics of trauma (mechanisms of injury)physiological,treatment,effects,ethics,tran sporting and major incidents.
I hope that this is relevent to the thread.... :/ ?

[KSoDBartman]

Speaking as a scientist, what's your opinion?I don't really know anything about this, as I'm more of a factual science guy and not a politics of science guy.

[KSoDBartman]

As the Hubble telescope reaches the end of its tour in 2005, and as the technology is 15 years or so old, are there any plans to make another 'scope?
Yes; that's the whole idea behind abandoning Hubby. The drawback is that the scope's not ready yet and won't be for a few years. Moreover, the orbit in which it will be inserted is farther out than any human has ever been. As such, it will be unserviceable. One can't help but question the wisdom of this move.

I hope that this is relevent to the thread....
Medicine's a science, is it not? Join the fun! :)

[donquixote99]

Dear Scientist:

While people sometimes talk about the following questions in a glib and annoying way, I ask them in all seriousness. I don't necessairily expect definitive answers, but I'm nonetheless interested in your approach and comments:

1. What was going on before the Big Bang?

2. What is the Universe expanding into?

[Fredfredson]

Hi Don

I don't have a good answer to the first question but I have some thoughts on the second. Hopefully Bart has a better response but here goes.

The problem with the whole expanding Universe thing is that it is actually a misleading metaphor. I prefer to describe this phenomenon as "stretching".

Consider a very large rubber sheet in the middle of which are a bunch of dots. The dots are all separated by a finite space that can be measured.

Now stretch the sheet in all directions and observe what happens to the dots. The space between the dots appears to grow (as do the dots themselves). One curious aspect of this effect is that any one dot looks like it is the "center" of the expansion with every other dot moving away from it.

But, isn't the entire rubber sheet getting bigger, ie taking up more of the space "outside" as the sheet is stretched?

Yes and no. If the sheet is very large (infinite) then it isn't any bigger after the expansion it is still infinite. We can only see that part of the Universe which is within the distance that light can travel since t=0 so essentially all we can see is a VERY small bunch of dots in the middle of a VERY VERY large sheet.

In fact the only reason we can detect this stretching is because light (which is the Universal Tape Measure if you like) travels at a finite speed.
Since it takes a finite time to pass between galaxies, we see light that has been stretched during the intervening time of expansion (the red shift).

We would never detect an expansion, without a finite light speed, because the tape measure (light) would stretch at the same time and everything would appear static.

How's that?

F
:pooter

[Fredfredson]

Here is a facinating article:
http://www.21stcenturysciencetech.com/articles/fall01/navigators/navigators.html

Does anyone have more info on this "voyage"?

Here is more on the device they used to measure Longitude. Not bad for 232 BC!

http://www.21stcenturysciencetech.com/articles/fall01/Tanawa/tanawa.html

F
:pooter

P.S. For what it's worth, my "specialties" are:

Physics (garden variety mostly, some nuke and chemistry)
Geology
Navigation (hence the above)
Ships and the Sea (history)
Magick ;)

F

[Francois Cellier]

Let me answer some of your questions in a succinctly scientific manner.

A human FART (http://www.encyclopedia4u.com/f/fart-1.html) can travel all up and down along the Ticino valley of Southern Switzerland.

... but this is not, where we live. The public transportation system close to our Swiss home uses a different accronym: SOB (http://mercurio.iet.unipi.it/list/switzerland/switzerland_sob.html) (Südostbahn = "Southeastern Railway," denoting the Southeastern part of the Canton of Zurich).

http://www.trainlgb.com/album/europe/sob/gsob9.jpg

;)

[Francois Cellier]

Fred:

I am afraid you got it wrong. Celestial mechanics is tricky business.

Years ago, I visited TRW in Huntington Beach, CA. I was allowed to fly a docking maneuver on their space flight simulator. It was hopeless. If you speed up, your spacecraft rises. If you slow down, its orbit lowers. This means, that there is only one stable orbit at each altitude. The farther out you are, the faster you fly, but also, the longer it will take for an orbit to complete. Mars, being farther removed from the Sun than Earth, travels considerably faster than Earth around the Sun, and yet, a Martian year equals almost two Earth years.

Here is an article that describes the phenomenon that you were referring to:

http://www.cnn.com/2004/TECH/science/01/01/leap.second.ap/

-----------

Earth orbit slows no more, baffling scientists
Friday, January 2, 2004 Posted: 3:02 PM EST (2002 GMT)


BOULDER, Colorado (AP) -- In a phenomenon that has scientists puzzled, the Earth is right on schedule for a fifth straight year.

Experts agree that the rate at which the Earth travels through space has slowed ever so slightly for millennia. To make the world's official time agree with where the Earth actually is in space, scientists in 1972 started adding an extra "leap second" on the last day of the year.

<Remainder of article cropped>

-----------------

You are in good company though, Fred, as CNN also got it wrong. If the year becomes longer, Earth actually speeds up, rather than slowing down, and the orbit becomes bigger, rather than smaller.

[Fredfredson]

Thanks Francois
Makes sense.

What do you think was causing the lengthening?

On a related topic: What keeps the Earth from spiralling in towards the Sun? Wouldn't that require the addition of energy to overcome the gravity drag?

F
:pooter

[Francois Cellier]

What do you think was causing the lengthening?

I don't know. It shouldn't be anything related to Earth itself. I can think of numerous Earth mechanisms that would consume energy, thereby slowing Earth down. I cannot think of one that would add kinetic energy to it.

There are, however, many mechanism outside Earth that could explain it.

One might be the constellation of the outer planets. They exert a pulling force on the Earth orbit. Yet, this should not explain a force that is sustained over a long period of time, as the relative positions between the planets change.

A second mechanism might be solar winds that constantly reach the part of the Earth that is pointing to the Sun, thereby pushing Earth out ever so slightly.

Another more exotic mechanism might be that the entire Solar system is contracting under its own weight. This certainly happens constantly. Gas clouds in the outer regions of the solar system come closer to the central star under gravity forces. When this happens, the inner regions of the solar system speed up their rotation, like an ice skater in a pirouette, pulling in her arms, and thereby, the inner regions of the solar system expand.

Yet, these are only speculations. I don't believe, anybody truly knows the answer to that question.

What keeps the Earth from spiralling in towards the Sun? Wouldn't that require the addition of energy to overcome the gravity drag?

No, it wouldn't. It would require that Earth would shed all of its kinetic energy. A stable orbit is produced by balancing the gravity force that pulls Earth toward the Sun against the centrifugal force caused by the rotation of Earth around the Sun.

The centrifugal force is proportional to the square of the angular velocity, and inverse proportional to the distance from the Sun. The gravity force is inverse proportional to the square of the distance from the Sun.

If you accelerate Earth in the direction of its motion around the Sun, you increase its angular velocity. Thereby, the centrifugal force gets bigger. It wins out against the gravity force, and Earth moves away from the Sun.

As Earth moves away from the Sun, its tangential velocity remains the same, but its angular velocity decreases, as the orbit becomes bigger. Hence the centrifugal force decreases also. Since the angular velocity decreases proportional with the increase of the distance, the centrifugal force decreases with the third power of the distance, whereas the gravity force only decreases with the second power. Thus, eventually, the gravity force will catch up with the centrifugal force, and a new stable orbit farther away from the Sun is reached.

[KSoDBartman]

1. What was going on before the Big Bang?This is a mystery. Maybe lots of stuff, maybe nothing. It's also somewhat a moot point because we can't know about anything that happened before the Big Bang anyway, assuming there even was somwthing to know about.

[quote]2. What is the Universe expanding into?This is often a response to the common analogy of using a balloon blowing up to show how space itself expands. It's a decent analogy, but the downside is that it leads to misconceptions like this. The Universe is not expanding into anything. The Universe is everything. As such, there can be nothing, by definition, outside of it. On the other hand, even if there were something outside of it, we'd have no way to measure the properties of whatever higher dimension (a fourth spatial?) into which we were expanding.

[donquixote99]

To paraphrase your replies:

1. Don't bother asking, it's impossible to know.

2. Your question is nonsense, by definition. And if it wasn't, it would be impossible to know.

I must say I feel my inquiries have been dismissed in a most dissatisfying way. I think you might acknowledge more clearly that science faces 'open edges' at this and other spots, where only faith that reality 'must' make sense, as science defines 'sense,' is available to paper over an utter inability to conceptualize an even theoretical 'scientific' description.

[Francois Cellier]

Don:

We really don't know yet.

Is it impossible to know? Absolutely not. The first question that will need to be answered though is whether our universe is open, closed, or stationary.

Depending on the total mass in the universe, the expansion that was caused by the big bang will go on forever (an "open" universe, where the gravity forces are insufficient to pull back the universe, i.e., the energy provided by the big bang suffices to grant the universe "escape velocity"), will eventually contract again into a singularity (a "closed" universe that may possibly lead to a new big bang thereafter, i.e., a "cyclic" solution), or a borderline case, in which the gravity forces are sufficient to prevent continuous expansion, but insufficient to pull the universe back together again (a "stationary" universe).

The visible matter of the universe is clearly insufficient to pull the universe back together again, by roughly a factor of 10. Otherwise, the night sky would by full of light, rather than dark. Yet, there is the issue of the so-called dark matter that may make up for the missing 90% or even overcompensate.

We know that dark matter exists, because we can measure its effects on the universe, e.g. by measuring the gravitational forces of the galaxies on each other. There are several indirect techniques to assess the effects of dark matter, thereby estimating the amount of it. All of these measurements lead to numbers close to 90%, i.e., we don't know yet for a fact whether the universe is open, closed, or stationary. The newest indications are that the universe is most likely closed, but by a small margin.

The second problem is that we don't yet fully understand the high-energy physics of the early universe, i.e., the universe before there were atoms, when the four forces were still unified. Yet, already the next generation of particle accelerators ought to provide us with good models of what the universe in this early stage looked like.

Once we understand the physics of the early universe, we'll be able to come up with good models of the speed of expansion during this early stage. So far, there are speculations that the early universe expanded faster than gravity alone would predict, because of the interaction of the other forces, but we don't have good data yet to quantify that model.

We furthermore don't fully understand the relationship between space and time. Our current relativity theory models break down under high-energy physics conditions. Thus, we don't know "when" time started and how it started after the big bang.

In my view, all of these questions are answerable, and will be answered probably within the next 50-100 years.

[Fredfredson]

Your question is nonsense, by definition. And if it wasn't, it would be impossible to know.

So you didn't like MY answer? :(

Why?

F
:pooter

[Dave]

Wasn't Don responding to Bartman? :dunno

[Fredfredson]

Ummmm

:dunno

If so, sorry Don.

F
:pooter

[Francois Cellier]

Let me provide you with my own favorite big bang theory (as good as any other out there!).

You know how nuclear bombs work: You take two junks of enriched plutonium. Each of them radiates, but other than that, is harmless. Yet, when you throw them together, a new physical phenomenon takes place that makes the entire combined clump explode in a violent reaction.

Physics is highly nonlinear, and "catastrophic events" can therefore happen. There ain't no "catastrophies" in linear systems, i.e., in linear systems, small causes have always small effects. Yet, in nonlinear systems, small changes can have huge effects. This has been known since the 60s, when René Thom (http://www.exploratorium.edu/complexity/CompLexicon/catastrophe.html) introduced a new branch of mathematics, called catastrophe theory.

We already know that the same is true in cosmic events, such as supernova explosions. Depending on the size (total mass) of a star, its eventual contraction (after it burnt all of its hydrogen fuel) can lead to either a neutron star or a black hole.

We also know that most galaxies feature at their center a supermassive black hole.

The dark matter in the universe most likely consists of black holes. Yet, even the supermassive black holes don't account for the entire dark matter that is present in the universe.

Yet larger black holes may exist that either swallowed entire galaxies, or that never made it out of the big bang in the first place, i.e., constitute remnants of the big bang.

My favorite big bang theory hypothesizes that, as the size of supermassive black holes increases, a new physical phenomenon takes place, one that we have only observed once: the big bang, i.e., once the entire universe contracts back together into a supersupermassive black hole containing all of the mass of the universe, another catastrophe takes place that makes that supersupermassive black hole explode ... and it probably takes just about the entire mass of this universe to make this happen, i.e., I am personally leaning toward a cyclic universe with a bit more of a speculation as to how the cycles may come about.

I recognize, of course, that my model invokes a deus ex machina, i.e., is no better or worse than any other theory postulated to date. Yet, better models of the early universe ought to be able to either refute or strengthen this (as well as any other) hypothesis.

[donquixote99]

Yep, my reply was to Bartman. Sorry that wasn't clear.

Fred, your explanation is clear enough, and my only 'complaint' would be that it doesn't sooth this ache i get in my brain when I try to think about existence vs. non-existence. Which the universe, expanding or not, touches upon, as everyting that exists.

[donquixote99]

Francois, I don't have too much trouble until I'm told there's uncertainty as to when time starts. That little item has a 'turtles all the way down' ring to it.... :)

Thanks much for your summaries; they put me in a little better touch with the progress of thinking and research on these things.

[Francois Cellier]

I was off-line this afternoon, thus had no chance to elaborate further on my "big bang theory" to get rid of the "deus ex machina" in it.

Any big bang theory that requires a "new catastrophic physical event" to explain the big bang without offering any explanation as to where this new event comes from, in fact doesn't provide any new answers, it only rephrases the question. That is what I meant by the "deus ex machina" in my theory.

Let me try to provide further details, but for that, I need to offer a little more knowledge first as to the nature of our universe.

You all know that Earth rotates around its own axis, an axis that goes through the two poles.

You also know that the moon rotates around the Earth. It does so by following pretty much the Earth equator, and it rotates in the same direction as the Earth itself, i.e., the axis of the moon's rotation coincides with the axis of the Earth rotation.

This is no axident. Also the Sun rotates around its own axis, which is pretty much parallel to the Earth axis of rotation. Also the Earth, and all other planets of the Solar system rotate pretty much along the equator of the Sun, and all of these rotations, with very few exceptions, are going in the same direction.

The entire Solar system doesn't form a sphere, but rather a disk, in which all of its bodies can be found all of the time. The plane of the disk is called the ecliptic plane.

Whereas all of the bigger bodies move within the ecliptic plane plus or minus a few degrees, a few smaller bodies seem to be stray bodies, and they are. They were torn away at some point in the past from their original path by a near collision with another bigger body, and were thrown out into another path that no longer follows the general pattern.

Where does this pattern come from? The Solar system evolved from a contraction of a gas cloud. Just like the ice skater, the gas cloud rotated faster and faster as it contracted inward to the center of gravity of the cloud. The gasses at the center heated up due to their increased density, which eventually led to the fusion of hydrogen into helium. The Sun was born.

Why the rotation? The ice skater only rotates faster when pulling her arms in, if she rotated to start with. The same is true with the Solar system. The initial rotation was dictated by the fact that the entire Solar system rotates around the center of our galaxy, the Milky Way.

Also the galaxy is not spherical, but rather disk-shaped. The plane of its disk, the galactic plane, is essentially the same as the ecliptic, plus minus a few degrees.

Why did the Solar systems start rotating around the center of the galaxy? The answer is simple: They do so, because the entire galaxy rotates around the center of gravity of a cluster of nearby galaxies, which as a whole rotate around the center of gravity of a supercluster of clusters of galaxies, which in turn rotate (this now is speculation, as it hasn't been measured yet) around the center of the universe.

Hence even the universe is essentially disk-shaped rather than spherical.

Why do the galaxies rotate around the center of the universe? We don't know, but this is, where my big bang theory starts.

As stars rotate, black holes formed from imploding stars rotate as well. They do so even faster than the stars themselves did before, because of the ice skater effect. Supermassive black holes at the center of galaxies must also rotate around their own axes, and do so for the same reasons.

It should therefore be expected that also the giant black hole, from which the universe evolved in the big bang, rotated around its axis. When it exploded, the masses of the universe preserved their kinetic energy, which is the reason for the rotation of everything in this universe to this day and age.

Let us now assume that the total mass of the universe is large enough to lead to a closed universe, i.e., that eventually, the galaxies will contract back into the center.

It is reasonable to assume that the stars and galaxies don't arrive at the center all at the same time. Let me explain.

Assume you have a pool table with six balls at the center in a triangle, and you are shooting a seventh ball at the cluster of six. Theoretically, once you kicked off the seventh ball, everything is completely determined. Yet, we cannot predict where the seven balls will come to rest after the collision. This is due to chaos theory. In nonlinear complex systems, small causes can have large effects over time.

This is different from catastrophe theory. In catastrophe theory, small causes may have immediate large effects. In chaos theory, the effects only accumulate, so that a small cause now may have a large effect as time evolves. Chaos theory only requires nonlinearity and complexity.

Since our universe is highly nonlinear and very complex, it is utterly chaotic, just like the pool table, only more so. Thus, it is not reasonable to assume that, after the big bang, the rate of expansion of the universe is everywhere exactly the same. Rather, it will follow a Gaussian distribution, whereby some regions of the universe are more highly energized, i.e., expand faster, than others.

When the universe comes to its end in the big contraction, the less energized regions of the universe will arrive back at the center earlier and either form a black hole, or join remnants of the original giant black hole that is still there (more likely!).

The reason is simple. Assume that you throw a ball of 1 kg straight up into the air. The ball will fly upward for a while, then turn back, and finally hit you on your head. The stronger you throw, the faster the ball will fly, but also the farther up it will travel. It turns out that the time difference between the throwing of the ball and when the ball hits you is proportional to the initial velocity of the ball.

Thus, the less energized regions of the universe will contract earlier, whereas the more energized regions will take more time. There may even exist some very highly energized regions that reach escape velocity and never make it back.

Because of the maelstrom of the universe, the incoming galaxies all arrive essentially from the same direction. What happens to their kinetic energies? They need to be preserved. They do so by adding a little to the angular velocity of the rotation of the giant black hole around its own axis.

Thus, as more and more parts of the universe find their way back to the center, the giant black hole rotates faster and faster.

The masses inside the giant black hole experience a tremendous gravitational pull toward the center. Yet, because of the rotation of the black hole, they also experience a centrifugal force away from the center.

Initially, the gravitational force is much stronger. Yet, the gravitational force grows linearly with the mass of the black hole. In contrast, the centrifugal force grows quadratic with the angular velocity, which in turn grows linear with the masses of the arriving galaxies. Thus, the centifugal force grows quadratically with the mass of the giant black hole.

At first, the gravitational force is much bigger than the centrifugal force. Yet, as more and more mass arrives, the centrifugal force becomes bigger, and eventually wins out against the gravitational force, at which time the giant black hole explodes, and another universe is born. As the masses are thrown out, the central remnant of the giant black hole slows down its rotation. It will have to wait until another universe has reached the end of its tether.

[KSoDBartman]

To paraphrase your replies:

1. Don't bother asking, it's impossible to know.

2. Your question is nonsense, by definition. And if it wasn't, it would be impossible to know.

I must say I feel my inquiries have been dismissed in a most dissatisfying way.
Then I don't know what you want. They are the answers as science knows them at this point. If you find then unsatisfactory, perhaps you should get an advanced degree in physics and peer into the mysteries of the Universe yourself. :dunno

[KSoDBartman]

Mars, being farther removed from the Sun than Earth, travels considerably faster than Earth around the Sun, and yet, a Martian year equals almost two Earth years.
Ehh, nope. Earth's orbital velocity is 29.8 km/s. Mars has a velocity of 24.1 km/s.

Here is an article that describes the phenomenon that you were referring to:

http://www.cnn.com/2004/TECH/science/01/01/leap.second.ap/

-----------

Earth orbit slows no more, baffling scientists
Friday, January 2, 2004 Posted: 3:02 PM EST (2002 GMT)


BOULDER, Colorado (AP) -- In a phenomenon that has scientists puzzled, the Earth is right on schedule for a fifth straight year.

Experts agree that the rate at which the Earth travels through space has slowed ever so slightly for millennia. To make the world's official time agree with where the Earth actually is in space, scientists in 1972 started adding an extra "leap second" on the last day of the year.

<Remainder of article cropped>

-----------------

You are in good company though, Fred, as CNN also got it wrong. If the year becomes longer, Earth actually speeds up, rather than slowing down, and the orbit becomes bigger, rather than smaller.
Yes, CNN got it wrong, but for different reasons than the one you cite. One thing I've learned over time is to place very little value in the details of scientific reporting by non-scientists. Solution? Go straight to the source!! (http://www.boulder.nist.gov/timefreq/general/leaps.htm#Anchor-52904)

Astronomical time is based on the rate of rotation of the earth. Since atomic clocks are more stable than the rate at which the earth rotates, leap seconds are needed to keep the two time scales in agreement.
So, leap seconds are added in response to variations in Earth's period of rotation on its axis, NOT its period of revolution around the Sun.

These variations come from a few sources. Resistance between the atmosphere and land masses (especially tall ones like the Himalayas), and the motion of magma churning underneath the crust are two.

[KSoDBartman]

The first question that will need to be answered though is whether our universe is open, closed, or stationary.
This has been more or less definitively answered. The discovery that the Universe is accelerating in its expansion has provided near-conclusive proof that the Universe is open, and its ultimate demise will be either a Big Freeze or a Big Rip. The Big Freeze will occur when all the stars burn out and the Universe becomes dark and cold. The Big Rip will happen if the expansion of space itself eventually overcomes all other forces (electromagnetic, weak nuclear, strong nuclear, and gravity) and tear protons and neutrons into their individual constituent quarks. Personally, I'd tend to the Big Freeze because it appears the expansion of space is only a factor on the largest of scales, which is why M31 (Andromeda galaxy) is on a collision course with the Milky Way. Combine that with the fact that the other three forces are even stronger than gravity, and I'd say that provides some pretty solid evidence against them being overpowered by the expansion of space.

The visible matter of the universe is clearly insufficient to pull the universe back together again, by roughly a factor of 10. Otherwise, the night sky would by full of light, rather than dark. Yet, there is the issue of the so-called dark matter that may make up for the missing 90% or even overcompensate.
There's also the "dark energy" which is supposedly driving the Universe apart, explaining the acceleration of the expansion.

[KSoDBartman]

The dark matter in the universe most likely consists of black holes.
This is not even close to being "most likely." The recent discovery that neutrinos spontaneously change their state strongly implies that they have mass, albeit very, very, VERY little. Thus, it is quite feasible that the "dark matter" is comprised of neutrinos, or weakly interacting massive particles (WIMPs), as opposed to black holes, or massive compact halo objects (MACHOs).

once the entire universe contracts back together into a supersupermassive black hole containing all of the mass of the universe, another catastrophe takes place that makes that supersupermassive black hole explode ... and it probably takes just about the entire mass of this universe to make this happen,
It is inaccurate to think of the beginning of the Universe as coming from a black hole. The Big Bang was an "explosion" of sorts that created space itself. As such, there cannot be such a deformation of spacetime before the Big Bang characterized by a black hole. Also, the explosion of the Big Bang contained all the energy of the Universe, but only as energy and not matter. Thus, it would be impossible to compact matter to densities sufficient to create a black hole when no matter existed in the first place.

[Francois Cellier]

Thanks, Bart, for your replies.

Your last remark is based on the assumption that the universe is open. As far as I know, this is not proven yet, and various models exist that offer explanations of the acceleration in the expansion of the universe.

Your conclusion assumes that there was nothing before the big bang, i.e., the big bang truly was the act of creation rather than recreation of the universe.

A cyclic solution is beautiful, because it can offer explanations of:

1. why the big bang happened, when it happened, and
2. where it got its energy from.

Of course, this does not defy the true creation, it only removes it by another mechanism, because now, we can ask ourselves, who created the universe of universes, how, "when," and "why."

Stephen Hawkings embraces a cyclic universe, although his big bang theory is distinctly different from the one that I offered. His theory assumes that all the stars and galaxies come together at one point in time in a reversal of the big bang. For reasons that I explained, this is not plausible to me.

[KSoDBartman]

On the other hand, he's probably smarter than you and me put together...

:D

[Francois Cellier]

You were right about the orbital velocities (http://nssdc.gsfc.nasa.gov/planetary/factsheet/marsfact.html) of Mars and Earth. I should have checked!

It is still correct though that I need to accelerate my spacecraft if I want to lift it to a higher orbit. Yet, my model was too simple. In order for the spacecraft to reach a higher orbit, it needs to be lifted out of the gravity well. For this, it requires energy. That energy has to come from the kinetic energy of the spacecraft. Thus, the orbital velocity decreases in the process, rather than remaining the same, as postulated earlier.

To be even more precise: Until now, we only talked about circular orbits. Orbits don't have to be circular. They can also be ellyptic. If your spacecraft is currently occupying a circular orbit, and you fire the rockets in a tangential direction, accelerating the spacecraft, the spacecraft will assume an ellyptic orbit, i.e., rise to a higher altitude, then turn around, and come back to the original altitude on the other side.

Although there are many different ways to change the orbit of your spacecraft, most maneuvers would actually be flown in this way, in order to minimize the amount of time the booster rockets are engaged, thereby minimizing the fuel consumption.

Thus, in order to lift the spacecraft from one circular orbit to another circular orbit farther out, the boosters would be fired once to change the orbit to an ellyptic orbit, where the fartest point of the trajectory (the apogee) coincides with the new desired circular orbit. Once the spacecraft has arrived at the apogee, the booster rockets are fired once more in tangential direction to keep the spacecraft on that new orbit.

When I simulate a spacecraft operating under its own propulsion system in a gravity well, I don't make mistakes. I simply formulate the equations of motion (6 second order differential equations, plus a differential equation accounting for the change in mass of the spacecraft due to consumption of its own combustibles), and then press the simulate button.

However, when posting on this board, I try to stay away from equations and use mental models instead that are intuitive, yet produce qualitatively correct answers ... and this is, where it is easy to make mistakes. :/

[Francois Cellier]

http://www.ece.arizona.edu/~cellier/temporary/lec35_12.gif

Cosmic Triangle plots based on: N. A. Bahcall et. al, "The Cosmic Triangle: Assessing the State of the Universe", 1999, Science, 284, 1481.

----

Found at: http://instruct1.cit.cornell.edu/courses/astro101/lec31.htm

The green area denotes a closed universe, whereas the brown area denotes an open universe.

[Francois Cellier]

I checked around a number of "lecture" pages from different universities, such as: http://www.uccs.edu/~mgrabows/pes106/LecNotes/lecture29.htm . If we were to take a poll from these pages, the verdict would be that the universe is open albeit almost flat.

Yet, the poll would be solely based on measurements that are inconclusive. The margin of error is bigger than a conclusive answer would allow.

Furthermore, there are other difficulties with an open universe, which is why theoretical physicists (like Hawkings) shun away from this model.

For one, if you assume that general relativity describes the macrocosmos correctly, then the universe has to be closed. The theoretical underpinnings of general relativity theory fall apart in an open universe.

For these reasons, among others, I am not willing to give up on the concept of a closed and possibly cyclic universe.

My own theory of it, as espoused in my short outline above, is no better or worse than any other such theory, but I like it, because it is simple, illustrative, and covers a lot of ground in explaining observable facts, such as the rotation of the universe.

[Prophet0]

If I may join in to share my love of science. Being my first post of this nature I'm not sure if anyone would want me to go more indepth, so if anyone feels I should explain myself more, just ask.


The recent discovery that neutrinos spontaneously change their state strongly implies that they have mass, albeit very, very, VERY little. Thus, it is quite feasible that the "dark matter" is comprised of neutrinos, or weakly interacting massive particles (WIMPs), as opposed to black holes, or massive compact halo objects (MACHOs).


I actually am very unhappy with the idea that dark matter is composed of neutrinos. Neutrinos are way to fluctuating for me. The main problem is that due to the heisenburg uncertainty principal they exist and have mass relative to themselves, but to anything else they have the relative worth of a virtual particle. Plus even if they had enough mass to account for the massive amounts of dark matter, there would have to be so many of them coming in and out of existance that they would just drain the energy from the universe.

I don't know what to say about wimps and machos. Wimps do not have enough proof that I am aware of to even consider (If you have a link please show me). Even the search for them has come up with nothing. Machos, on the other hand, seem like the most convenient solution that is within that list. I feel that my knowledge, however, on Wimps and machos is relatively limited and I would be happy to learn more.

I personally think that hologram theory is the best solution to both the dark energy and dark matter problem. It solves so many problems, and gives a great model for the multiverse.

As for whether the universe is open or closed, I would have to go with open. I think that it would be very convenient for it to be closed or cyclic, but, unfortunately, The discovery of dark energy seems to make that an impossibility.

[Neko]

These are going to sound like really stupid questions, but I've always wondered about them:

1. Electricity always takes the path of least resistance, right? So how does it know before it's taken it which path is the best one? Is it like magnetism?

2. I once had friend who had a fish tank with an electric heater in it (to keep the fish warm, that is, not as a suicide attempt or a piece of conceptual art). One day this heater went wrong and he got a shock when he stuck his hand in there, but the fish were OK. I preume that this was because he was grounded and they weren't, is this right? If so, how do electric eels and so forth work?

The really sad thing is that I was good and physics and electronics once upon a time.

[Prophet0]

1. Electricity always takes the path of least resistance, right? So how does it know before it's taken it which path is the best one? Is it like magnetism?

This is an interesting problem.

And the answer is that Electrons take every possible path. If you take the average of every possible path then you get the path that the electron takes, which is the path of least resistance. So in reality the electron does every possible thing that can be done, but we only observe the average.

This theory is called "the sum of all historys" and was discovered by Richard Feynman, who is quite possibly the coolest person in all of history.

as for:

2. I once had friend who had a fish tank with an electric heater in it (to keep the fish warm, that is, not as a suicide attempt or a piece of conceptual art). One day this heater went wrong and he got a shock when he stuck his hand in there, but the fish were OK. I preume that this was because he was grounded and they weren't, is this right? If so, how do electric eels and so forth work?

I would assume that you are right as to why he was shocked but the fish were fine. Another possibility is that maybe the fish where shocked too, they just weren't damaged by it.

I would be interested to see what others have to say about this.

[Fredfredson]

I would assume that you are right as to why he was shocked but the fish were fine. Another possibility is that maybe the fish where shocked too, they just weren't damaged by it.


What causes the problem of being shocked is current flow not voltage.

The fish don't experience any significant current flow because they are pretty much the same resistance as the water around them. The current flow is spread throughout the body of the water so no particular fish get's "shocked". When the person touches the water they get the whole works. :eek

So how does an electric eel kill fish then?

The eel generates a very high voltage that pulses. These pulses cause intermittent current flows, proportional to the voltage pulse, which then stuns or kills the fish.

F
:pooter

[Geezer38]

My question is about global warming and the eventual effects on Western North America. We have all heard the scenario of melting polar ice releasing huge quantities of fresh water, pushing the atlantic gulf stream southward and turning Europe and Eastern North America into an ice box.

It is my understanding that the waters off our Pacific coast is cooling down. I'm wondering what kind of weather changes we might see?

[Francois Cellier]

The scenario that you mentioned is a possible scenario. It has received attention in recent weeks due to the latest Hollywood spoof, but it is only one among several possible scenarios. The truth is: we really don't know.

What we do know is that cataclysmic events have taken place on this planet before, leading to a number of ice ages, and there is no reason to believe that the causes of these events have been removed, i.e., it is not only plausible, but rather likely indeed that the future will hold more ice ages. Yet, we cannot say when.

Looking at the frequencies of past occurrences, we can say that ice ages don't occur in geological times, but rather in historical ones, i.e., this is not something that will likely happen in millions of years, but rather in thousands.

Is human influence strong enough to trigger such a cataclysmic event? We don't know that for sure, but the possibility exists, and that alone is reason enough to be worried and try to do what we can to prevent this from happening, if we can.

With respect to your specific question: the Western part of North America would not fare much better either. The reason is the rotation of planet Earth around its polar axis. This leads to Westerly winds in the polar and moderate regions, and to Easterly winds in the tropics. Due to friction with the ground, the air rotates together with the planet, but friction within the air accelerates the air in the polar regions (as it has a shorter path around the globe), whereas it decelerates the air in the tropics (as it has a longer path).

Thus, air masses eventually move around the globe at essentially the same latitude, and ice masses on one side of the globe would therefore spread to other regions of equal latitude with time. Thus, if the polar region in the North would grow (as it did in earlier ice ages), this would happen symmetrically everywhere.

Right now, the South pole region is considerably bigger than the North pole region. In another ice age, the North pole region would grow at the expense of the South pole region. The average temperature of the Earth cannot change by much. It is dictated by the energy balance of the planet, i.e., how much solar energy is received, versus how much is being radiated out.

The average temperature can only change with a change in the composition of the air (greenhouse effect). We don't know whether human influence suffices to change the composition sufficiently, but it may. By burning the fossil fuels, we increase the CO2 content of the air. This leads to global warming.

Initially, this effect may be compensated by an increased vegetation in Syberia. Increased vegetation would consume (bind) more CO2 from the atmosphere.

Unfortunately, an ice age, once it begins, has the opposite effect. It would reduce the amount of vegetation that the planet has, because there are more and bigger land masses in the North than in the South, i.e., if the Northern regions freeze over, the vegetation belt is pushed further South, but cannot expand, because there are not enough land masses there.

Thus, in an ice age, the CO2 content of the air increases further, as there is no longer enough vegetation to reduce it. This increases the global warming, leads to a melting of the polar regions, the vegetation expands again further North, and eventually, the original equilibrium is restored. The ice age is over.

The imbalance between the polar regions is part of the equilibrium. It is caused by the asymmetric distribution of land masses. The North pole region is "usually" smaller than the South pole region, because there are more land masses in the North than in the South.

[Francois Cellier]

http://www.upi.com/view.cfm?StoryID=20040709-092944-4352r

Analysis: Satellite will help eye warming
By Hil Anderson
United Press International
Published 7/9/2004 9:39 PM


PASADENA, Calif., July 9 (UPI) -- All systems were go Friday for the weekend launch of a Delta II rocket set to carry into a new satellite into orbit that scientists expect will provide a wealth of new information on the increasingly controversial subject of global warming.

The Aura satellite is scheduled to blast off during the wee hours of Sunday morning from Vandenberg Air Force Base in California. It is equipped with cutting-edge scanning instruments that will monitor the various layers of the atmosphere and how they interact with pollutants that include the greenhouse gases that may or may not be causing Earth's climate to heat up.

Climate scientists can always use new and improved data, but the Aura mission's greatest value may be in the political arena where policy makers remain in the middle of a battle between environmentalists who insist global warming is a genuine threat and skeptics led by some in the business community who dismiss the entire concept as junk science."

"Nothing really is in the works that addresses global air quality," Project Scientist Phil DeCola told reporters from Vandenberg in a televised news conference Friday. "One can imagine the value of this information in developing future policies."

Described as being about the size of a small school bus, Aura holds four different types of scanning instruments that will take in-depth measurements of the atmosphere, in particular the ozone layer in the upper stratosphere that protects humans from the sun's harmful radiation.

Industrial chemicals and toxins have been blamed for a deterioration of the ozone layer, which has led to international treaties curbing the use of chlorofluorocarbons, also known as CFCs, in refrigeration units and other devices.

The recovery of the ozone layer appears to be hindered by the same greenhouse gases being blamed for global warming. Aura scientists noted, however, there still were gaps in the knowledge of the ozone layer the satellite could help fill in.

"We expect there are complicating factors (in ozone recovery)," said Mark Schoelboro of the Goddard Space Flight Center. "We still don't have a complete understanding of the ozone layer and the stratosphere."

Aura will be able to give scientists an accurate inventory of the levels of CFCs in the atmosphere on a global scale as well as the by-products bromine and chlorine that are said to cause ozone deterioration.

Ozone is a gas with a double meaning: In the stratosphere, far above Earth, ozone protects living things from the sun's harmful ultraviolet radiation. At the lowest level of the atmosphere, the troposphere, ozone is considered a pollutant that is present when high levels of the precursors carbon monoxide and hydrocarbons are also in the air.

One of Aura's four instruments, the Tropospheric Emission Spectrometer, or TES, will provide detailed inventories of pollutants in the troposphere, and can accomplish the task on a regional basis so that scientists and politicians will be able to pinpoint just where the harmful emissions are coming from and take steps to remedy the situation.

The argument over how much pollution comes from what sources has been a major bone of contention in the entire global warming controversy.

"We live in one atmosphere and that atmosphere contains pollutants that are pushed into the air from many sources," Schoelboro explained. "We're all breathing someone else's exhaust gases."

The issue of where the pollutants actually come from played a major role in the United States' continuing refusal to formally adopt the 1992 Kyoto treaty on reducing greenhouse gas emissions.

Industry and its supporters in Washington said the United States was unfairly being singled out for massive cutbacks in such emissions, to the point where it would cripple the U.S. economy while allowing emerging industrial powers, such as China and India, to continue running their less-efficient factories with little or no interference from the treaty.

Global warming also stoked the war of words between environmentalists and various industry organizations and think tanks that vilified predictions of major warming of the climate as being a baseless scam perpetuated by the greens.

The argument might seem to be nothing more than ideological sniping, but it plays a significant role in the complex effort to keep both the nation's air and its economy healthy.

As soon as data from Aura begins streaming back to Earth, in about 90 days, it should help present a truer picture of the globe's air quality and set the stage for meaningful regulation that is more tightly focused on the scope and source of the problem.

"This kind of information will be a national and international treasure for those who are making important decisions about policy as it pertains to natural resources," DeCola said.

"NASA really isn't in the business of making regulations," he added. "We are in the business of providing the solid scientific information needed by those who do. It will be very interesting to see how new international treaties might be formed."

The difficult work will be up to U.S. political leaders and those in the rest of the world as they attempt to forge a new consensus on curbing global warming and air pollution in general. Thanks to Aura, they will at least possess a clearer picture of what needs to be done and less so-called junk science and opinions to clutter their judgment.

[Jayne B]

Very good news! (I'm surprised the project wasn't cut in favour of funding Bush's pan-flash Mars-shot.)

[KSoDBartman]

This is an interesting problem.

And the answer is that Electrons take every possible path. If you take the average of every possible path then you get the path that the electron takes, which is the path of least resistance. So in reality the electron does every possible thing that can be done, but we only observe the average.While this may be accurate in the grand cosmological scheme of things, it doesn't really help in the explanation of WHY the electrons choose the path of least resistance (which isn't really an accurate euphamism because if you have a path that splits and rejoins and one branch has a 500 Ohm resistor and the other has a 5 Ohm resistor, you'll measure current across both branches).

The electrons "know" which way to take the same way we would "know" if we were travelling down a narrow corridor begin pushed from behind. We get to a junction and some of us go down one and some the other. The ratio of people who go down one path versus the other has to do with the ease with which people flow through each particular branch. A wide branch and a small branch (corresponding to a small and larger resistance wire, respectively) will both have people flowing through it, but the larger branch will have a bigger load because it can accept a greater flow.

This theory is called "the sum of all historys" and was discovered by Richard Feynman, who is quite possibly the coolest person in all of history.Bah. Hawking and Wheeler are way more bitchin'.

[KSoDBartman]

I actually am very unhappy with the idea that dark matter is composed of neutrinos.It's not proven as yet, but it is a distinct possibility. Saying you don't like it if it's the case is like saying you don't like that Earth is round. You'll just have to deal. ;)

Plus even if they had enough mass to account for the massive amounts of dark matter, there would have to be so many of them coming in and out of existance that they would just drain the energy from the universe.First of all, the Uncertainty Principle allows for local deviation from the principle of conservation of energy, as long as the violation is short-lived. In other words, energy deficits caused by virtual particle creation are not cumulative since the virtual particles are annihilated within about 10E-35 seconds, restoring the balance.

Second, neutrinos do not exist because of the Uncertainty Principle. They are byproducts of stellar processes. They are real, not virtual, just like the photons hitting your retina from the Sun.

I don't know what to say about wimps and machos. Wimps do not have enough proof that I am aware of to even consider (If you have a link please show me). Even the search for them has come up with nothing. Machos, on the other hand, seem like the most convenient solution that is within that list. I feel that my knowledge, however, on Wimps and machos is relatively limited and I would be happy to learn more.WIMPs and MaCHOs are fashionable names for what we've already been discussing. Weakly Interacting Massive Particles are (or could be, among possible other things) stellar neutrinos. Massive Compact Halo Objects are black holes. Sorry for the confusion.

I personally think that hologram theory is the best solution to both the dark energy and dark matter problem. It solves so many problems, and gives a great model for the multiverse.I've not heard of this theory. Is it possibly known by another name?

[Neko]

I've read about a load of this stuff in my pop physics books (not remotely connecting it to Real Life, of course), but since everyone else has proper education and stuff, I'm going to keep my mouth shut except to ask another two questions:

1. We've got it established that electricity (electrons) takes the shortest path. So how come that trick where you shock someone by holding an electric fence and their hand at the same time (er... not that I've ever been childish enough to do this or anything) works? I.e., the current passes through you and they get the shock. Or has this got nothing to do with shortest path?

2. How is it possible to jump on a skateboard? I'd have thought that if you were rolling along and then jumped you'd be in the air and the skateboard would be on the ground, it not being attached to your feet. (I'm talking about on a flat surface here, rather than when you come off a ramp)

[cwinton]

-- for every force, there is an equal and opposite force;
so, what is the opposite of gravity and how can that be manipulated?

[cwinton]

-- and another thing: :wink

*is gravity 'magnatism?'

[Neko]

I thought that gravity was the bending of space-time by a massive object and hence not strictly speaking a force. (Please correct if this is wrong)

[Jayne B]

Gravity: noun; the force that caused John Kerry's jowls to slide further from his cheekbones as the campaign progressed.

Gravitas: noun; the expression on John Kerry's face when he mentioned the problems of the poor and homeless during the campaign.

Bending not time/space but media-mediated reality....(Not a scientific answer... sorry).

[sir digalot]

for every action there is an equal and opposite reaction...

gravity is the attraction between objects everything is subject to gravity from the smallest electron to the most massive of objects.... gravity is not a force... it is mutual attraction, things that have more mass have greater gravity... and so does some beer too...
to conteract gravity you need to apply a force greater then the attraction, an accelaration in excess of 9.80665 (rounded)meters per second per second... i beleive it is about 32 feet per second for the none meric among us, obviously the larger the mass of an object the more energy and force needs to be spent in overcoming the attraction ( remember weight is reliant on gravity... mass is the physical-ness of an object.. in space you are weightless but still have mass)

why certai objects have a massive gravity well whilst being relativly small is an answer possibly only more intelligent people then i can answer.. :lol somehting to do with all those greek symbols and algebra, and i am sure they are all wrong aswell... thee are the same people tha tsay time travel and faster then light travel is impossible, and they are wrong about that.... they don;t know it yet but they are... :lol

[Neko]

#ed_op#DIV#ed_cl##ed_op#FONT size=2#ed_cl# #ed_op#/DIV#ed_cl##ed_op#DIV#ed_cl##ed_op#FONT size=2#ed_cl#thee are the same people tha tsay time travel and faster then light travel is impossible, and they are wrong about that....#ed_op#/FONT#ed_cl##ed_op#/DIV#ed_cl##ed_op#DIV#ed_cl##ed_op#/DIV#ed_cl##ed_op#DIV#ed_cl##ed_op#/DIV#ed_cl##ed_op#DIV#ed_cl#They clearly haven't seen me when there's furniture to be moved. You'd swear that I entered the pub before I'd actually left the house... #ed_op#/DIV#ed_cl##ed_op#DIV#ed_cl##ed_op#/DIV#ed_cl##ed_op#DIV#ed_cl#But seriously... I thought that gravity depended on mass, so if you've got a small, super-dense object (for eg a neutron star, not GW, he works to his own rules) it'll have a whole load of gravity.#ed_op#/FONT#ed_cl##ed_op#/DIV#ed_cl#

[Jayne B]

As opposed to GW, who has a whole load of something else, but is equally dense? :lol