BearOfNH

Of course 10^21 seconds (3.17e+13 years) is greater than the accepted lifetime of the universe. Evil liar, indeed.

So if you set up a square of 45° mirrors and used a http://www.laserpointerpro.com/1000mw-highpower-kaleidoscopic-blueviolet-laser-pointer-p-349.html (blue-violet laser), would you expect to see all the colors of the rainbow as the bouncing light gradually loses energy? Come to think of it, that might be an interesting teaching tool at say the high-school level.

... and of course a certain (tiny) amount of stuff on earth originally came from Mars via a pinball-like meteor strike.

PMJI, but "Cosmological Principle" is the correct spelling. It could even be called "Principal Cosmological Principle" were it the most popular of several competing theories. So, could we please change the spelling in the title?

Moon Express (http://www.npr.org/blogs/thetwo-way/2013/12/07/249503187/is-mining-on-the-moons-horizon, for example) is one company trying to exploit the huge deposits of 3He on the lunar surface. At about $100K/oz it's certainly valuable enough to try to mine on the moon and ship back to earth.

I'm also a fan of the new Cosmos. Neil DeGrasse Tyson (hereafter just "Neil") is a much better presenter than Carl Sagan. I found Sagan's exposition technique a bit pompous, as if he were speaking to a crowd of 6-year-olds. Neil is far more direct, speaking in a manner typical to discussions between equals...despite the fact he knows far more about the topic than 99.99+% of the viewership. Neil's animation also does a great job in those places where words don't well convey the concepts involved.

Good, but I betcha an Indiana Jones riff would have gotten you some +1s.

Rather than "unaffordable" I would say "expensive". OTOH, nuclear is also more available so in a sense you're paying more for guaranteed access to power. Guaranteed that is, unless you're near 3-mile island USA, Chernobyl USSR or Fukushima Japan.

The distance from Merak to Dubhe is one-fifth the distance from Merak to Polaris. Even in Arizona it's not that hard...unless you are in the greater Phoenix or Tucson area, in which case the light pollution is a bitch.

Well, Jupiter is pretty easy. Astrologers have expended great amounts of effort in calculating planetary orbits, so we can tell you how far it is to any planet at any time. For more distant objects one can calculate the location in polar coordinates on July 1, and again on January 1. This gives you a triangle with base 2AU=186,000,000 miles. You then use trigonometry to calculate the length of the other sides and >POOF< there you are.

There have been a large number of studies of galaxies and I have yet to read one where the authors mention difficulties stemming from Oort cloud interference. They say the OC is heavily populated, but apparently the density is low enough not to cause problems.

Not to mention such "stuff" is highly unlikely to crop up in every galaxy under study. One or two, plausible. All of 'em, NFW.

Imagine some time in the past we saw a galaxy that was deep red-shifted, i.e., moving away from us rapidly. At some point the galaxy disappears and we no longer see it. Ergo, we no longer feel its gravity either. Presumably this is going on continuously, for galaxy after galaxy disappearing from view. Hence over time we're feeling less and less gravity. Is there any way to measure this and get an idea of, say, the rate at which galaxies are disappearing?

Nowadays you can see all the interesting stuff right on the internet. But isn't it more fascinating to see stuff thru a telescope instead? Regrettable in a way, since I got so many trees all around my night sky view is quite limited.

That's the current prevailing "heat death" model. Except the photons aren't at absolute zero, since that would imply no movement.

Yes. Better yet, I can focus with the camera button and then use the USB switch to take the photo. A quick snap (all that I can do right now) will then not change focus. Of course, we are talking about shooting stars...pity CHDK doesn't have a "focus to 1620l.y." command. Hell, maybe it does; I'm just getting started here. The right thing to do of course, is practice so I can do a half-click with the USB remote. It can't be that hard...

After some hunting around, here is what I have learned: For Canon digital cameras, there is a set of free software called CHDK, the Canon Hack Development Kit, which allows you to do all kinds of hackery to your Canon but without making any permanent changes. This includes enabling remote control, i.e., using the Ricoh remote USB switch (above) to click the shutter so you don't move or even touch the camera. I have personally followed all the steps to install CHDK on a separate SD card and enable the remote USB switch feature, and taken pictures with a Ricoh USB switch. I can take a picture without touching the camera, and have done so aplenty. Currently I'm having trouble half-clicking the USB switch -- which focuses the lens -- but that's my clumsy fingers. This doesn't solve everybody's problem, but most Canon cameras have CHDK kits ready for download. It helps to have Java on a PC to correctly process the SD card.

... so said explosion would constitute a really big bang, then?

But the hero does travel in space. The earth is spinning as it orbits the sun while our solar system transits the galaxy, etc. Even for minor Δt, all of Δx,Δy and Δz are gonna be pretty big. How the time-travel machine accounts for that is something I've always wondered.

Doesn't this mean that today we'd describe Aristotle as a "theoretical physicist" as opposed to an "experimentalist"? If you give it a modicum of thought, obviously most internet cranks are going to be from the theoretical side. But not all theoretical physicists are crackpots.

This discussion is hard to follow because of the way the replies quote each other. In any event I sure as heck would like to see some melted wood.

Not unless you can demonstrate the very existence of light itself. And distance. Oh, and time. Mighty tricky, these other universes.

Given the h-o-s pseudo-particles are just a way of modeling things, a follow-on question is: can we extend that model to other particles -- elementary or not -- as well? What would a photon be "made of"? Frequency (freqon)? Anything else? (If not, then in some sense a photon is even more fundamental than an electron). Take a holon away from a proton and give it to a nearby neutron and >POOF< you've switched the N and P. I know this sounds crazy and I'm not gonna pursue the notion any further, else I'd have started a new thread. Just an idle thought to kickstart the subconscious before a 4-day weekend.

If there were more planets in the solar system they would crash into each other, reducing the number of planets. Hmmm, does the asteroid belt bear any resemblance to a galaxy (within the confines of the belt, that is).

If your propulsion system is designed to keep a constant earth-like gravity it must accelerate at 1 g for half the voyage and decelerate at 1 g for half the voyage, i.e., turnover at the halfway point. Making a turnover at any other point would mean not having earth-like gravity for most, if not all, of the mission. So one question that pops up is: how important is it to maintain an earth-like gravity? And ... what do you mean by "more advantageous"? Faster trip time? Less fuel consumed? Optimum passenger comfort?