*I suppose so, just like when an ice skater is spinning and extends her arms, she slows down. If she pulls her arms back in, she would speed back up. I'm no physicist, but I would think if a spinning ball started expanding, and even if the core remained spinning at the same rate, the greater surface area would take longer to complete one rotation. The rotation would take even longer if the core lost any speed.
The above statement must be taken with absolute cynicism and disbelief. =)
What podcast is this from? I've been listening to them in order, and I listened to 65 - 70 yesterday, and also the latest one, so I'm not sure.
Not adding mass. Just shifting it around. Its also weird to say that its expanding. To say that about a "circle" like the earth implies that all "points" on the circle are expanding. The equater is expanding. Or rather the earth is flattining out. A good test for this is to weigh yourself near the tropic of capricorn or tropic of cancer. Then weigh yourself at the equator. You'll weigh more at the equator. Ill source all this when I get home. At work on phone makes this tougher.
I did enjoy gavins theory on how all the continents drifted apart. "One day, for no reason, they drifted apart". I just imagined Europe drifting away from everything because it would "make a good story".
It's the moon that causes the slowing of the Earth's rotation. It is actually the same reason that we only see one side of the moon. The gravitational pull of the Earth slowed the moon's rotation until it stopped spinning.
This same process is caused by the moon and is happening concurrently as I type this, although on a much smaller level, to the Earth. Eventually the Earth will stop spinning.
Actually, the earth does increase in mass, but only a few pounds at a time (through meteors and celestial dust agglomeration.) Nowhere near enough to cause slowing of rotation, but the earth does indeed gain some mass. (Though likely loses it at approximately the same rate via fission reactions.)
What? The moon has not stopped spinning. That's the craziest thing I've ever heard. =D The moon is in a Geosynchronous orbit, meaning that it rotates at the same rate that it revolves around the earth. If the moon did not spin, then we would actually see every side of the moon, not to mention other things that would happen if a celestial body did not rotate.
It's not a geo-sync orbit. It's called a tidally locked orbit. You can have one at any orbital distance, and all it means is that one revolution of a body around it's axis is equal to one revolution around another body. Most two body systems tend towards tidal locked orbits. If the moon were in geo-sync, it would always appear to be in the same part of the sky.
The Earth will never stop spinning. It's current rotational kinetic energy is 2.138 x 10^29 J. That's equal to about 51 EXOtons of TNT. At the rate we lose energy to tidal effects, the sun should go nova before the Earth's rotation slows more than an hour or so.
In reply to Radius55, #9: I like science stuff, so thanks for having this great conversation! I thought perhaps I was mistaken about the moon's orbit, but according to several science geek websites, the moon is in a geosynchronous orbit. What you refer to as always in the same spot over the earth is called a geostationary orbit, like what many satellites are in.
I never mentioned any time restraints on when the earth would stop, just that eventually it would. Also, you shouldn't say "never" in the same paragraph that you give an example which shows change. Although, you do deserve thanks as well for further clarification.
But, yeah, I ruined my attempt at an explanation and flat-out included false information convoluted by not recalling something correctly.
The moon definitely is not in a geosynchronous orbit. Technically, a geostationary orbit is a specific type of geo-sync orbit with the satellite orbiting around the equator. A geo-sync orbit will always pass over the same areas every day, while geostationary will stay over the same spot. However, the objects must be in a stable orbit around 40,000 km above the earth But the moon takes about 28 days to travel around the earth, and orbits at 400,000 km.
That site also says nothing about the moon having a Geosynchronous orbit.
Upon further research, I have found that the rotation of the Earth will never stop due to natural effects. The Earth is transferring its rotational energy to the moon, but there's a limit to how much can be exchanged. Given several billion years, Earth will rotate at a rate of 47 revolutions per year. The moon will orbit the Earth at the same rate. This is due to the tidal locking effect I mentioned earlier where a two body system of greatly differing mass tends to end up with both objects having the same orbital and rotational periods.
You are right, of course, the earth gains some small amount of mass from things simply falling onto it. That's not what Gavin was speaking of on the podcast though, he was referring to the "Expanding earth" theory, which I only recognized because I like to find crackpot theories for fun.
I trolled that video so damn hard a few months ago. I hate it when people learn science terms, but don't know how they really work. So, here I was arguing with the guy on the subject of pair production, and he didn't even know what a boson or fermion was. It was funny, because he kept ignoring everything I pointed out that was wrong (mainly that the amount of energy necessary to create the amount of mass he's talking about would have exceeded the gravitational binding energy of the Earth in seconds), and just stating his "theory" over and over. Oh, and he kept telling me to read more and learn the truth.
I didn't know the "truth" only had a middle school science education.
I very much enjoy the discussion in the thread. The students in my Earth Science class would be confused as hell. There's a great mix of basic and very very advanced info here.
The shape of the Earth isn't expanding. It is slightly bulged at the equator and slightly squished at the poles due to rotation. What they call an "oblate spheroid". But it's very close to perfectly spherical (off by around 70km in diameter). As for the moon's orbit, it's called synchronous orbit in that it rotates at the same speed that it revolves, and it shouldn't be surprising since the moon was once part of the Earth a long time ago. Or at least that's what the theories say.
Honestly, the tidal effect of the moon's orbit around the Earth (remember, gravity works both ways, so both Moon and Earth feel it) is way deeper than I get in my class. But in the long run, I'd imagine gravitational drag forces will probably do something to that effect. Kind of like how Mars' moons are slowly spiralling in to its surface as a tidal effect. RIP Phobos and Deimos in the next 100 million years or so?
Surprisingly, in the Moon's case, gravity is causing it to accelerate. The math is weird, so don't ask me to get into it, but the Earth is basically dragging it along. The easiest way to explain it is that mountains exert more force than areas with lowlands. If the rotation of the Earth and Moon system was such that one day on Earth were equal to one lunar revolution about its axis, were equal to one lunar revolution about Earth, it would be at perfect equilibrium. Since the Moon's angular velocity about the Earth is lower than that of the Earth about itself, the Earth will slow down and the Moon will speed up. It works out that sometime around the time the sun goes nova, a day will be 47 times longer, the moon will be at 2.5 times its current distance, and equilibrium will have been reached.
I don't know much about "pair production," as I never got into particle physics. I do quantum, but on the atomic scale. Given my training is in chemistry, I always find it rather entertaining when people try to argue things with me, especially when it comes to things like nuclear energy (my current field), or general chemistry issues, like the health effects of NutraSweet (aspartame.) I don't get angry, I just kind of laugh and then pwn them.
While I didn't sleep through science, I have to admit that most of what I retain from science knowledge is from Bill Bryson's 'A short history of nearly everything.' The one thing that stuck is that the rules of the Macro world don't always apply to the micro world. We live in such a weird and cool reality.
Oh, and Star Trek. From Star Trek I know that reversing the polarity solves EVERYTHING.
Actually, the creation of quantum mechanics came from the knowledge that at the micro-scale, all classical mechanics fail, e.g. the ultraviolet catastrophe and other such issues. I never really took much interest in particle physics, as it's a little too abstract for my liking. I do theoretical work, but it applies to direct physical problems, so I like the balance.
This thread is making my inner science nerd do backflips :P
At first the idea of an expanding earth appealed to me (months ago) because I've never liked the Pangaea theory. What are the fucking chances that a planet would naturally develop as a giant ocean with a single, ridiculously huge continent on it? Wouldn't an imbalance of mass to that degree be freakin impossible due to centrifugal force? I understand that there is plenty of empirical data supporting continental drift, and that fossil and geological trends suggest the same. It just seems fucking stupid to me.
But yeah, the "expanding earth theory" isn't real science at all. Its a cool idea but so is hiring a giant cowboy to lasso the moon.
It is slightly important to point out that the earth wasn't FORMED with Pangaea. Continents have been merging and fragmenting for billions of years, even older then life itself existed on the planet. Pangaea isn't the first Supercontinent, nor are ours the only time there have been several separate ones.