TOO MUCH EDUCATION

[cjameshuff]

I think making a first principles simulation of the three body problem will be incredibly trivial in today's terms. You could do time steps by the millisecond and it won't take too long to run.

It is quite trivial, vastly simpler than getting a useful patched conic solution, and you can get stable, reasonably realistic orbits without much trouble given only an initial state. Taking tidal effects and such into account increases the complexity significantly, but isn't needed for basic spacecraft trajectories.

However, you can get into trouble with rounding using extremely small timesteps, and the simplest methods require small timesteps to get a good approximation. You'll really want to use something higher order than Euler's method. There's a variety of methods with varying properties with respect to energy conservation, rate of convergence, the forces and derivatives needed, and complexity...RK4 is commonly used but seems more complex than it's worth. I've personally used Velocity Verlet, Beeman's algorithm, and Chin's Algorithm C. And backward Euler can be useful for a very simple approach.

[Trebor]

I think making a first principles simulation of the three body problem will be incredibly trivial in today's terms. You could do time steps by the millisecond and it won't take too long to run.

It is quite trivial, vastly simpler than getting a useful patched conic solution, and you can get stable, reasonably realistic orbits without much trouble given only an initial state. Taking tidal effects and such into account increases the complexity significantly, but isn't needed for basic spacecraft trajectories.

However, you can get into trouble with rounding using extremely small timesteps, and the simplest methods require small timesteps to get a good approximation. You'll really want to use something higher order than Euler's method. There's a variety of methods with varying properties with respect to energy conservation, rate of convergence, the forces and derivatives needed, and complexity...RK4 is commonly used but seems more complex than it's worth. I've personally used Velocity Verlet, Beeman's algorithm, and Chin's Algorithm C. And backward Euler can be useful for a very simple approach.

At the risk of getting educated do you know of a good resource which goes into this in detail?

[cjameshuff]

At the risk of getting educated do you know of a good resource which goes into this in detail?

Wikipedia has overviews of most of the methods I mentioned. Don't recall where I found Chin's Algorithm, but Google brings up the original paper.

[Not Myself]

I'll race you!

Well I'm out of the starting gate!  I'll take it to another thread though.

[raven]

DAKDAK may not be saying much, but they're still around; their profile says their last activity was earlier today.

[Kiwi]

DAKDAK may not be saying much, but they're still around; their profile says their last activity was earlier today.

Perhaps he's soaking up all the tremendous education in this thread and chewing it over.

[DataCable]

Does anyone else hear a Duran Duran song in their head every time they see the thread title?

[Echnaton]

Does anyone else hear a Duran Duran song in their head every time they see the thread title?

Thankfully no.

[ka9q]

3.   YOU DON’T KNOW WHAT THE TEMPATURE OF THE MOON IS,OR IF THE MOON REFLECTS OR EMMITS LIGHT

As others have mentioned, you can estimate the surface temperature of the moon based on how rocks on Earth absorb and radiate heat. It's not magic.

Actually, we can directly measure the moon's surface temperature all the way from earth just by looking at the electromagnetic radiation it emits. Yes, in addition to reflecting sunlight the moon emits its own radiation; you just can't see it because it's in the far infrared, not the visible spectrum like the sun.

Every object above absolute zero emits electromagnetic energy over a range of wavelengths, with the peak wavelength inversely proportional to its temperature. The hotter the object, the more total power it radiates and the shorter the peak wavelength of that radiation. By looking for that peak, you can directly determine the object's temperature.

The sun' "surface" ** temperature is about 5900K so its radiation peaks in the visible spectrum, with substantial amounts in the near infrared and near ultraviolet. The moon is much colder, so its radiation peak is in the far infrared (as is the earth's). In fact, it emits detectable amounts of radio noise in the microwave spectrum. This is useful because our atmosphere is mostly transparent to microwave radiation while carbon dioxide, water and other trace gases have strong absorption lines in the far IR that are best known for contributing to the greenhouse effect.

** Of course the sun doesn't have a solid "surface" or even a well-defined boundary since it is entirely composed of plasma. Like every atmosphere, its density just drops off exponentially with altitude. What we see as its "surface" is the level at which the sun's atmosphere is dense enough to become opaque to visible light.

[Stout Cortez]

Somewhere I saw a re-creation of Laurel and Hardy in which they are portraying rocket scientists. Laurel proposes that since men have been to the moon, they should land a man on the sun. Hardy says that it's far too hot. Laurel thinks for a moment and then says, "Let's land him there at night when it's cooler." Hardy says, "Now you're thinking!"

Good old common sense....

[ineluki]

Does anyone else hear a Duran Duran song in their head every time they see the thread title?

Thankfully no.

Pink Floyd seems to apply better anyway.

[BertL]

Come now, people. Leave this kid alone.

[sts60]

If the picture attached to this post is of DAKDAK, I would hardly call him a "kid".  Looks all grown up to me, so I'll treat him like an adult.

[Mr Gorsky]

Does anyone else hear a Duran Duran song in their head every time they see the thread title?

Thankfully no.

Pink Floyd seems to apply better anyway.

The Duran song, I assume, is 'Too Much Information' anyway so, Duran fan that I am ... I'm with Floyd on this one.

And it pains me to yet again see a fellow person of faith taking the religion good, science bad course. I have never yet found the two things to be incompatible ... even creation vs evolution is a crock, as the two things are not mutually exclusive. After all, why would an all-knowing, all-powerful God create a universe that wasn't capable of managing and developing by itself and needed him (or her) to directly intervene when any changes were required?

[JayUtah]

If the picture attached to this post is of DAKDAK, I would hardly call him a "kid".  Looks all grown up to me, so I'll treat him like an adult.

You mean the post where he thanks us for debating with him and states how impressed he is with the credentials of this site's participants?  I guess we all know where that was destined to go.

I simply have little patience with arguments of the form, "My untested, ignorant superstition trumps your degrees and years of experience."