KeithHarwood

All the galaxies are rushing away from each other, with the speed depending on how far apart they are. If we follow their motion backwards they all started out at the one spot 15,000,000,000 years ago.

The latest measurements show that there is enough kinetic energy that the galaxies will continue to get further apart forever. So it looks like the Big Crunch won't happen. This is where Hovind is behind the times.

As I said, it's speculation. There are some serious theoretical difficulties. I read recently that someone has resurrected the oscillating universe (that's what it's called) so perhaps they have found a way around those problems. But, in any case, the best measurements suggest that the Big Crunch will never happen.

When we follow the paths of the galaxies backwards all the potential energy they have now was once kinetic energy. That, plus the kinetic energy they have now amounts to an enormous lot of energy in a very small space, that is, an enormous energy density. We can make very small amounts of that energy density in the laboratory, tiny little quantities of the Big Bang material, and observe what happens. There is light so energetic and intense that it can create and destroy matter.

Simple subtraction. We know the solar system was formed about 5,000,000,000 years ago from lots of evidence. We can see stars in all stages of their lives, collapsing gas clouds, young stars with disks of dust around them, middle aged stars with planets, elderly stars bloated, cooler, swallowing their planets, dying stars with no fuel left gradually cooling. We plot a graph of what the stars look like at each stage of their lives and identify where our sun is on that graph. It's about 5,000,000,000 years old and with about as far to go.

We can measure the ages of the oldest rock on earth. They are aobut 4,500,000,000 years old. We can measure the ages of meteorites, the last remnants of the disk of dust that formed the planets; they are about 4,500,000,000 years old.

We see it happening all the time out there.

Add up all the motions of all the particles. There's a bit left over corresponding to a rotation about some axis.

A good question. The solar system started out as a cloud of dust and gas, mostly hydrogen. As it collapsed the potential energy of the gas was converted to kinetic energy. As the gas approached the centre it compressed and was slowed down and the kinetic energy converted into heat. As the collapse went on the pressure and temperature at the centre increased until the hydrogen was broken apart into electrons and protons and they were all being bashed together very violently.

Now if you bash two protons together sufficiently violently they stick together and one of the protons turns into a neutron with a bit left over. And if you bash another proton into that lot the new proton also turns into a neutron. And if you bahs that with another proton that proton sticks as well and you end up with the nucleus of a helium atom. So, you have four protons making one helium. But four protons weight more than one helium, the extra mass has been converted into energy which heats up the centre of the collapsing gas cloud even more. When the temperature and pressure of the centre of the gas cloud is enough for this to happen a lot the cloud turns into a star and shines by its own light.

This is happening inside our own sun right now. 537 million tons of hydrogen is being converted into 533 million tons of helium every second and the four million tons of energy left over comes to us as sunlight.

Because the earth isn't exactly a solid object. At quite modest depths rocks can flow and the gravity will make the earth round again. Now the moon is a different matter. It is much smaller and its gravity isn't enough to make rocks flow that way. Consequently it is lumpy inside. We can identify the major chunks that came together from their gravitational fields.

(Besides, it was at one time thought that there is a big dent in the earth, called the Pacific Ocean. I don't think this is currently accepted, though.)

Ah, you are getting near the limits of my knowledge here. I am told that the evidence suggests that after the earth was formed things settled down for a while and then there was a flurry of collisions about that time. Most of the craters on the moon were formed then. Patrick can probably give you more information and point you at the evidence.

For a long time we didn't know the rotation of Venus at all because it is covered in clouds. Observations of the clouds suggested that it rotated in roughly 24 hours, just like earth and Mars, but no one could get any better estimates and nobody really believed the estimates they did have. Then in the 1960's scientists used radar to observe its surface and found that it rotated very slowly. Over the years the observations got better and better so that now we know it rotates backwards once every 243 days.

Uranus was much easier. It is a gas giant planet and we can see (with difficulty) markings in its atmosphere. By tracking the markings from hour to hour we can see the planet rotate. Then it's just simple geometry.

It was the best I was aware of. The other, that tides in the atmosphere slowed it down, is newer.

But what evidence would I need to chose between them?

Suppose it was a head-on hit, what would we expect to see. Suppose that two more or less equal pieces came together, what would happen. They could come together slowly, but that would mean they were gravitationally bound before they hit; which means they would have been in orbit around each other, which means that Venus would have to spin quickly. So that is out. OK, so they weren't gravitationaly bound. That means they would have come together at roughly Venus's present escape velocity, which is 10 km/sec. Nope, that would vapourise most of the material and we would have to start building the planet from square one. So that's out too.

Right, so we have to have a smaller object hitting a larger one off-centre to stop whatever rotation it has. The smaller one would be vapourised but the larger wouold survive with a massive crater which would be filled by magma. So, if we could find such a crater we would have evidence for this theory. Not an easy task. The observations from the Magellan space-craft suggest that Venus's surface was molten about 800,000,000 years ago so the easy evidence won't be there. We'll have to go to Venus and do some deep geology. (I don't know how they came to the conclusion about the surface being molten at that time. I would guess that it was from counting craters.)

Now let's look at the other theory, that it was once fast but has now slowed down. What evidence would we look for here. On earth it's easy. I understand that the fossil record shows that the earth's rotation period was once about 18 hours and the month was a lot shorter as well, No doubt Patrick can give you the details that I don't know. However, a lot of people will be very surprised if it turns out there is life on Venus, so we can't expect that. What other indications would slowing down leave behind. I can't think of any . . . except . . .

Tidal locking. If Venus was tidally locked I would presume that it's rotation rate was once different and had now been pulled into its present rate.

What is tidal locking. You probably know that the moon keeps one face always pointed, more or less, at earth. What's happened is that the earth and the moon cause tides on each other. The stretch each slightly into an oval with its long axis pointing at the other. On earth this causes the tides in the oceans, but it also applies to the solid rocks as well, just not as much. When the bodies are rotating the bulges get dragged around by the rotation so one body is always trying to slow the other one down (or speed it up if the rotation around the axis is less than the revolution around each other). This means that the planets are flexing which converts the rotational energy into heat, which in turn radiates into space. So, with the rotational energy being removed the planets slow down until the rotational rate matches the revolution rate and the tidal bulges remain in the one place. Then there is no more flexing, no more energy loss and the planet is tidally locked.

It's actually a bit more complicated than that. Mercury is tidally locked to the sun. When I was young it was thought that t had one face to the sun all the time, but radar observations in the 1960's (not long after the first ones of Venus) showed that it is actually rotating in about 59 days, two thirds of its orbital revolution. This comes about because its orbit is quite elliptical and the tides when it is far from the sun are very different from the tides when it is close.

So how does this apply to Venus. Venus's orbit is once in 224 days, its revolution rate is 243. Not tidally locked as one-to-one. Could it be something like Mercury's case. Nope, Venus's orbit is almost exactly circular. But there is one funny thing. When Venus and earth are closest together it is always the same face of Venus that faces earth. Is Venus tidally locked to earth, then? Perhaps.

So there you have it. Why is Venus's rotation slow and retrograde? The honest answer is, we don't know for sure. But we do have two good hypotheses, one of which has some observational support but the other is going to have to wait for some seriously advanced technology to investigate.

Either way, there is no big deal, nothing important depends on the answer. We can wait until we know more.

Why should she?

Daggah

Are we being paid to teach you? No. So go get yourself a basic astronomy textbook. Finding the answers yourself will do you more good anyway.

Coragyps

For any of you who might care, I found where I heard of the tidal hypothesis for Venus's retrograde rotation. I read a brief piece in the Oct. 2001 issue of Sky and Telescope; they refer to an article in the June 14, 2001 number of Nature by C M Correia and J Laskar. I don't have access to Nature - they're online, but probably as a pay-per-view.
Tricia, why not find an astronomy book and ask questions both?

RufusAtticus

Also, Tricia, your school or county probably has a library where you can find some good books that can also answer your questions. The greatest skill you can learn in high school is how to answer your own questions by reading the scientific literature.

I would recommend you stay away from creationist sources because they don't have a good track record introducing people to science. If you do want to read creationist literature also read the literature it criticizes.

-RvFvS

Synaesthesia

RufusAtticus,

Good advice. Creationist literature is far too inbred and has been for decades.

In fact, sometimes mutations can be decidedly bad for the animal's survival. For example meitic drive or segregation disorder as described in Richard Dawkin's "The extended phenotype."

A mutation in fruitflies called the SD gene may actually damage sperm that don't contain it. This disorder can cause serious health problems in animals with it, but it tends to spread through the population becase it is good at spreading, not because it is necessary.

Tricia

The library in my town, to say the least, is not adequate.

But when I go to a Barnes and Nobles or something like that I'll get another book on evolution.

~Tricia

KeithHarwood

It's nice to know you have tried.

Skeptictank

Tricia
Just to chime in a lil' bit and put to use some of my astronomy/earth science knowledge....
There WAS a big "dent" (or crater) in the Earth, the think is, the Earth's serface is constantly changing over billions of years. Plate tectonics, volcanoes, erosion all reshape the surface of our planet. In fact, there are a few more recent "dents" in the earth (go see the giant crater in AZ!).
If you look at all the other planets and moons in the solar system, they DO have giant craters all over them from planetary bombardment of millions of years! It wasn't just the earth that was getting whacked!
Now, there is two exceptions, we can see Jupiter's moons Io and Europa. Both of these have little or almost no cratering. Why? Well we have observed that Europa is covered in ice, a giant frozen ocean that when hit, just fills in, covering the crater.
Io is even more exciting. It is the most active volcanic body in the solar system due to its gravitational interaction with Jupiter. The Voyager spacecrafts (and later Galileo) saw HUGE volcanoes all over it spewing out LOTS of stuff, constantly changing the surface and covering/eroding craters. Hope this answers your question.

BTW. I'm glad you are searching for scientific truth and not just digesting without question the (IMO) appalling lies being fed to you at school. Keep searching here and on your own! Science loves the deep questions!
And to my fellow athiests, you are doing a great public service. <ahem> "Props to my peeps"

RufusAtticus

Well then, I would like to recommend that you get Jonathan Weiner's Prizewinning book, The Beak of the Finch. It's a good book to introduce people to the science of evolutionary biology. We used it in college, and I think you can get a lot out of it.

-RvFvS

Oolon Colluphid

Hi Tricia! Here's the second part as promised!

Wrong. It’s not suction; nor is it stickiness in any conventional sense. The answer is even more extraordinary:
<a href="http://www.nature.com/nsu/000608/000608-11.html" target="_blank">http://www.nature.com/nsu/000608/000608-11.html</a>

Well the simple answer would be that the ones with flat feet did die. Only those that didn’t, survived and reproduced... passing on the non-flatfootedness to their offspring. But the principal mistake here is assuming it evolved as a sudden innovation -- one mutation, and they’re stuck.

As to how it evolved... don’t know -- how it works has only recently been discovered. But the way to think about it is this: it would not have evolved in a big single jump, but by step-by step improvements on what already works. So there needs to be relevant aspects of the ‘design’ and the environment that can vary in a continuum. In this case, there are several, including numbers of hairs and ridges on the feet, and angles and surfaces that it could, and could not, attach to. Geckoes started by walking on ground. Note that they’re adept climbers, so foot grip is already important. Feet can become ridged by any wrinkle in the soles giving a grip advantage. Number of ridges is a thing that can increase incrementally. Hairs, similarly, can help grip, and are skin outgrowths. Number of hairs can increase incrementally. Some slopes these feet could grip, others they could not. More grip means steeper and steeper angles that can be walked on, and so food can be chased onto more and more obtuse surface angles. Eventually there’s enough grip to hang from undersides of, say, branches... and branches that may be hang-onto-able can be more and more horizontal. Eventually, after many generations of only the best foot-grippers getting most food, you’ve got creatures that can walk on anything at any angle, even polished glass ceilings.

The formula for an evolutionary answer is: could it have evolved in one big jump? The answer is no, and this is where creationists stop. But evolution does not propose things happening in huge jumps.

Instead, evolution says, could it have evolved from something very like itself, but a little less efficient? The answer has to be yes, provided the ‘something’ is close enough to what we’ve got now.

Then repeat: could the something -- call it X -- have come about by a small change from something slightly less efficient, call it X2? Again, the answer must logically be yes, provided the difference is small enough and the X2 still worked, under some conditions, even though, obviously, not quite as well as the ‘now’ version.

And again: Could X2 have come about by a tiny change from X3? And X3 from X4? And so on.

Each X has to be functional under some conditions, but may be not as good as the modern form... or it might even have originally have been very useful -- for something else entirely. Thus part of the jaw of ancestral mammal-like reptiles (the synapsids) gradually became used instead as part of our mammalian hearing apparatus, the bones of our middle ear. (Note: snakes, for ex, ‘hear’ with their jaws ie pick up vibrations; our ear bones start embryonically as part of the jaw, and this transition is thoroughly documented in the fossil record.)

Well it’s got to get excess salt out somehow (suggest you look up ‘homeostasis’). Excess stuff can be excreted in all manner of ways. We mammals for instance excrete urea in our urine. Sauromalus species simply have nasal glands that excrete salt, though I doubt it comes out as pure table-salt! It’ll be in some sort of mucus. Why nose? Why not? Nostrils are simply openings to the outside world. We pee our waste, and our tears also have excretory uses. How did it evolve? Any bit of the body that excretes something can be co-opted. Noses are kept moist; cells in them produce mucus. What’s in the mucus would come from the blood. A mutation that meant the nasal mucus contained a little salt would be advantageous in a creature on the edge of a niche where there was excess salt. Being able to lose a little salt would let it exploit the niche better than those without this. Salt excretion is something that could incrementally increase, as descendants moved further and further into salt-rich areas. Rather than generalised throughout whole of the nasal passage, the process would be more efficient if concentrated in one place near the nostrils. Hence some cells would become specialised into salt glands.

Sure I’m making this up, but that is the sort of answer we would look for. First step in verifying this would be to look at related species to see what sort of noses they have. Any herpetologists out there know about iguanid noses? Thus evolution makes a prediction about things in related species. If they come off, evolution is confirmed yet again. That sort of testing, over and over and over, is why we’re so sure evolution’s right.

Don’t know. Why not look it up and tell us? There’s so much on the web, er, so to speak, about spiders that it would be good if you could find out which species is being referred to, at least. What does “7 different kinds of web” mean? Different shapes? Might this not depend on the circumstances of each web, its exact purpose, location etc? A different one for catching daytime insects and night time ones? It might be worth checking that it’s even true, given the source of the claim!

As to why is it the only spider to make so many... (a) is it true? (b) do no other spiders make more than one sort? and (c) how is this different from any other unique feature of any organism? Why does only the Chinese grass carp have pharyngeal teeth? Why are we the only bipedal ape? Why does only the vampire bat specialise in lapping mammalian blood? I don’t see how this spider’s range of webs is evidence for creation; it just looks like a distinctive feature of the species.

She doesn’t need to realise it. You have the answer right there: “so that they don’t stick together”. Dusting the eggs so they don’t stick is an advantage, something that can be selected for. Or rather, those spiders that didn’t do it are disadvantaged compared to those that do. Maybe it started by accident, I’d have to look up what this ‘dust’ is... or maybe you could. Try the flip side: why would a creator create eggs that would stick together in the first place, and so have to create an additional anti-sticking mechanism? This is no more inexplicable than how the spider comes to lay eggs or spin webs at all.

How about, those that didn’t do it didn’t leave as many descendants?!

Those are the sorts of answers we might expect. Note that even if the answer were ‘we’ve no idea’, this would not automatically mean that evolution cannot explain it, nor that creation would then automatically be the answer. There’s nothing irreducibly complex about any of these things. None of them refute evolution; there being bits we don’t yet know is what keeps biologists employed!

Cheers, Oolon