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Thanks! So, I guess my question is more generally, what are the implications of there being such a reference frame that is tied to the origin of the universe? It seems like that would be very important and meaningful, but I'm struggling to figure out exactly what the important implications are.

Thanks, Ibix! When you say that frame is hugely important because of all the matter that is at rest in that frame, what matter are you referring to? It's not clear to me that any particular galaxy, star, or planetary system need necessarily move exactly in sync with that reference frame. Are...

Studies of the Cosmic Microwave Background shows that the Earth is moving roughly 380 km/s with respect to it towards the constellation Leo I think. Yet (I think) the Cosmological Principle and the Michelson-Morely experiments suggest there is no preferred reference frame in the universe --...

My astronomy textbook includes this graph of the temperature of the Sun's Corona versus the distance above the photosphere. It appears to go up from 4,500 K to over 1 million K at 20,000 km above the photosphere. But at what point does it come back down? Or does it not? Does that mean the...

Thanks! That makes perfect sense.

Are the granules that we see on the Sun actually in the photosphere? Or are they actually just the top of the convection zone, with the photosphere beginning just above them? Or is the photosphere simply defined as the top edge of the convection zone where the granules are present, having...

If I understand correctly, orbital resonances of some of Saturn's moons are responsible for clearing out gaps in Saturn's ring structure (like the Cassini division). But I've also read that Neptune and Pluto are in a roughly 2:3 orbital resonance. So, do orbital resonances pull matter out of a...

About 20 years ago, in my mid-30s (and with a BA in economics and a master's in business), I started taking night classes in physics hoping to eventually earn the science degree I'd always wanted but never pursued. I found physics forums and used it to ask questions I was unable to get answered...

I think the answer for planets around the Sun and electrons around a nucleus are different. The answer above works for planets. Using the same classical mechanical answer, an electron should spiral into the center of an atomic nucleus in a tiny fraction of a second, unlike a planet around...

What do you find to be the most UN-intuitive (non-intuitive?) of classical physics (pre-QM and Relativity)? Most people find quantum mechanics and relativity very UNinuitive, because they involve phenomenon at subatomic scales or very high speeds, both of which are well outside a human...

I think Raza's question is more complicated (and fascinating) than the simple fact that objects that are close to you appear bigger than when they are far away. That's easily explained. Consider instead watching an airplane just before landing at an airport. I'm guessing it is probably...

Hmmm. . . I don't think this is quite right. The "shadow" you see on the moon that causes it to be a crescent is not the shadow of the Earth. It is simply the side of the Moon facing away from the Sun. It is the night-time side of the Moon. The only time a shadow of the Earth causes any...

Excellent. All good answers. Thank you.

I know the following statement to be true, being proven both mathematically, and verified by astronomical observations. What I need help understanding is HOW. . . "The law of Conservation of Angular Momentum requires that the slowing down of the rotation of the Earth around its axis caused...

Thanks! Good answers Rade and Colion. Thank you.

Hello all - While discussing Darwin's Origin of Species with a friend, I was asked, "Do you really consider that 'science' "? My response was, "Yes." But upon reflection, the conversation made me realize I do not have a good definition of what science is and is not. Even after...

Wow! Thanks to everyone for some very complete and thorough answers. This was very enlightening (no pun intended). :-)

Oh yeah. . . . in that case, you clearly win ! :-)

Clj4. . . I think you may have misinterpreted the intent behind my question. :-) I have no quarrels with Eotvos, and certainly am not trying to deny that inertial and gravitational mass are equal. Of course they are equal. I just thought it was in interesting question to contemplate what...

OK, I've thought about this a little more. . . let's see if this is correct: Prior to SPECIAL relativity, photons were considered massless, always. So everyone before Einstein would have believed that light does NOT bend near a massive object, like the Sun. Nowdays, photons are thought...

pym_phy and actionintegral - very insightful responses ! So, if A) gravitational mass was greater than inertial mass, then Aristotle would have been right all along. . . heavier objects would fall faster than lighter ones. But if B) inertial mass was greater than gravitational mass...

Farsight - I think Neutrino is right. Unless they were in mutual orbit, the gravitational acceleration between two Earth-sized planets positioned only 10 miles apart should be approx. 9.8 m/s^2 in total. Both would move towards the center of mass of the two (halfway in between) at about 4.9...

Zeit - In the Newtonian formula for Gravitational force you gave, F = Gmm'/r² So, for my question about if light bends when close to the Sun under Newtonian gravity theory, I think m = mass of Sun (or photon of light) and m' = mass of photon of light (or Sun). If either one of...

Looking for help interpreting a proof of G.R. please. . . One of the earliest proofs of G.R. was the deflection of light by a gravitational field, first shown in 1919 during a solar eclipse. I think Einstein predicted approximately 1.7 seconds of arc deflection during that eclipse. But...

What if inertial mass did NOT equal gravitational mass? How would our normal daily existence be different? Most interesting and creative answer wins ! [Edit: This is intended to be a fun question to answer, but I'm hoping to learn something quite serious from it. The force of...

Wow. . . so Johnson's concern was a valid one. At least for anyone who was within a few meters of the transmitting equipment. Thanks. :-)

Thanks T.Roc. I'll try searching under Fourier analysis. The reason I'm interested in non-standard frequencies is that the "standard note" frequencies of the equal tempered scale in wide use today were not always what was used in the past, nor in other parts of the world. I want to be...

In Ian Johnson's 1989 book, Measured Tones: the Interplay of Physics and Music, he says that in 1906 Reginald Aubrey Fessenden used an oscillating electric current to create a (first ever?) communication system for ships in the North Atlantic. p. 283-4 says: "He chose a frequency which...

PC sound synthesizer and oscilloscope ? I'm studying a bit about acoustics and music by reading books on these topics. But without being able to hear the sounds, and see how they combine on an oscilloscope, it's hard to really learn the material. I would like to find a computer program that...

Thanks again Marcus (and others). I've learned a lot. Incidentally, I originally asked this question because I recently purchased a new telescope with a Hydrogen-alpha filter (Coronado PST), and it got me to thinking about what I was actually looking at on the Sun and why this filtering...

Thanks ! Let's review. Thanks Marcus, that's very enlightening. That demonstration makes it easy to see how an accelerating charge could produce almost any wavelength of light. Let's see if I'm learning this correctly. Visible Light waves are caused by the motion of electrons in...

YES, YES, YES ! Russ, Hurkyl, Marcus, Astronuc, you've just nailed my problem. I was assuming that the only way to produce a photon was for an excited electron to drop a level or two. And that is all I was taught in my freshman physics class. We did study blackbody radiation, but only in...

Thanks Astronuc! I'm asking about color photographs I see in textbooks, magazines, and on the internet. So, I'm not sure on any of them how the picture was taken, or developed. I'm guessing any and all of the things you mention could be the culprit depending on what picture I'm...

Hey Russ. I appreciate your quick responses. And I know you're a smart guy, I've seen your posts here before. But please read these questions a little slower. My question is : How can a star that is almost completely made up of TWO elements, radiate at ALL frequencies? I'm not asking...

Russ. . . read the question more carefully. I'm asking why it is possible to see WHITE in pictures taken through a RED (H-alpha) filter. You should only see RED. I see such pictures all the time. Usually the white area is a solar flare or plague, whereas filaments appear darker red. I...

I recently bought a Hydrogen-alpha filtered telescope (Coronado PST). Looking through it, the Sun looks mostly red as expected since the H-alpha filter only let's through visible light at a wavelength of exactly 656.3nm which is in the red part of the spectrum. And I can see both lighter and...

If the Sun is 98.4 % Hydrogen and Helium by mass, and 99.8% by number of atoms, why does it radiate a continuous spectrum of light? Why doesn't it radiate a bright emission line spectrum only at the Hydrogen alpha, beta, gamma, etc. lines plus the Helium lines, and little or no lines at...

Thanks Marcus. Your initial conditions sound reasonable. Let's say it's made of a less exotic metal, like iron. And ignore any malicious intent of our would-be cosmic neighbors :-) do we stay cubic, or become a big cue ball?

A 43-year-old colleague of mine asked a childlike, yet intriguing question today. Perhaps someone could help answer it: If (somehow) a giant metal cube the size of the Earth appeared out of nowhere, what would happen? Would it: a) stay basically that way b) immediately get crushed under...

Are magnetic lines of force "real" ? You know the standard demonstration showing iron filings line up on a piece of paper over a bar magnet to illustrate the magnetic "lines of force?" I'm curious if the line of iron filings really represent places on that plane that are "special" (more...

Bubonic - Great questions! And you've gotten some thorough replies. Looks like the only two questions not answered yet (or not correctly) are these two: 1) What's the difference between the "Sun" and stars? Correct answer: "Sun" is the the proper name of one and only one star in the...