blike

I can dream up fairy tails about what our space probes have been really doing for the past 40 years of space exploration, but that doesn't make them true.

I saw this on fark today, it cracked me up.

I meant centripetal force. The mach principle, which einstein tried to incorporate into GR, holds that inertial forces are due to the quantity and distribution of all matter in the universe. If there is a universe containing only one object, that object would have 0 inertia. The bucket of water is the original thought experiment Newton worked with. You can apply the same principle to an astronaut spinning inside a giant bucket in space. He will experience a force towards the walls perpendicular to the axis of rotation.

SUPPOSEDLY its visible to the naked eye under VERY dark conditions.

Andromeda can be viewed (from non-light-polluted areas) with a pair of binoculars. I can see it from smack in the middle of the city with my 6" reflector scope. It just looks like a cotton ball though, because of the wretched light pollution. I've been out of town to some astronomy clubs, and its magnificant, even through a small scope.

I was pointing out that relative acceleration does not cause the beveling effect.

What about when the water and the bucket are in equillibrius, uniform motion? No acceleration acting on the bucket or the water? It seems obvious that "objects in motion tend to stay in motion", and this is why we experience centripetal acceleration. Yet, objects in motion relative to what? If you're in space spinning uniformly with the bucket of water, neither the water or the bucket will appear to have any motion. When you're travelling in a car, and it makes a sudden turn, you are pressed against the seat because of a change in velocity which results in acceleration. In this situation, the reference point is clear: the car around you. Yet in a dark area of space devoid of any surrounding matter, would you feel the change in velocity? Would you feel acceleration? Mach argues that your only reference frame in this situation is the sum of all the mass in the universe. He says that inertial effects are not innate in a body with mass, but are dictated by its relationship with all of the other mass in the universe. From what I gather, Einstein agrees with Mach in that he says since all of the mass in the universe dictates the geometry of spacetime at any given point, inertial effects are related to the mass of the entire universe. Einstein named Mach's idea "Mach's Principle". From encyclopedia.com: "According to Mach's principle, a body experiences no inertial forces when it is at rest or in uniform motion with respect to the center of mass of the entire universe. "

It's called The Fabric of the Cosmos : Space, Time, and the Texture of Reality

For those of you who enjoyed "The Elegant Universe", Brian Greene has a new book out. From the short moments I spent with it tonight, it seems to be more philosophical. Anyhow, as I was scanning through the first few chapters, I noticed an interesting question posed by newton that I have never considered. I'm going to relay it to you on memory, so someone correct me if I make little errors here and there. Imagine you have a bucket which is nearly full of water suspended from the ceiling by a rope that has been twisted so as soon as you let go (of the rope) the bucket will begin spinning. Neither the water or the bucket are in motion until you let go of the rope. After you let go, the bucket begins to spin as the string unwinds. At first, the bucket begins spinning around the water, and the water does not move. Shortly after, the water will begin to spin along with the bucket. However, as the water spins, it starts to bevel downward in the center as the water crawls up the sides. Newton asked himself: "Why does the water bevel?" To most of us, this is easily answered by experience: Because it's spinning! But Newton was asking something else. What does it mean to be spinning? Spinning relative to what? At first, we may answer that it is the bucket which spinning relative to the water which causes the bevel. But this is obviously not the case, as the water does not immediately bevel when the bucket first begins to spin. It is also not the relative acceleration of the water. Imagine a ring of people standing around the bucket. The water will still bevel when it is spinning relative to the people. Yet if the people were to start moving in a uniform, circular manner about the bucket, the water does not experience any bevelling. To what is the absolute reference point? Newton claimed that it was space itself which is a fixed reference point. Yet, if space were a fixed reference point, would we not be able to recognize motion (assuming no acceleration) even if we were in a pitch black absolute vacuum? I read up until Greene introduced a man named Mach who argued that without other matter as a fixed reference point, spinning would not be felt. He argued (from what I remember) that if the universe was just a giant void, that spinning would not produce any detectable effects. I believe Greene intended to further address the issue and ultimately answer the question, as he sets this up very early on and then abandons the topic abruptly.

Thanks sayo! I'll impliment that later this evening.

It had some gas. (not really sure). http server crashed, along with mysql server.

I've been tossing around the idea of starting a small organization or website to promote an early interest in science for kids ages 6-14. I just don't see as many kids interested in core sciences these days. When I was younger, I had a chemistry set, telescope, model rockets, gyroscopes, and all kinds of fascinating "science-type" toys. Most kids now days would rather play nintendo and browse the internet (ironic of course, being that the internet would be the main delivery format). Anyhow, I'm looking for ideas. Obviously it would be a non-profit site. I'm thinking about an interactive site with tons of fun (safe) things to do and make, and simple experiments to do. Also with competitions and resource links for parents etc. It's still just an idea right now, but it's something I'm interested in persuing. What do you all think?

black

I concur.

I'm here. Back on topic or santa will bring you coal this year.

I'm reading "Surely You're Joking, Mr. Feynman"

...put notting hill in the dvd player.

rofl. I don't know. He's just a crazy british guy (have you seen the movie?) and I was watching it with my girlfriend. Wasn't THAT bad of a movie though.

wow. 450 :/ one of those 450 sites has an admin who can't use MySQL for the life of him. Our database really shouldn't hamper the server performance, at all

That guy spike made me think of sayo for some reason. Kinda reminded me of thom yorke too. What's "daft" mean? "Daft prick"..

I like the british way even though they're wrong

me

Pectin, too.

Somewhat offtopic, but the speed with which they're slammed doesn't increase their mass. Its the fact that their summed masses bring them to a critical mass. I'd imagine they're "slammed" together in order to provide some extra energy and get the party started at a devastating rate.

Weight is a measure of force and acceleration, but it is not the same thing as mass. What you're describing is a difference in kinetic energy, due to velocity and mass. However, the mass is not the variable factor in your situation, only the velocity. For example, lets say we could hypothetically detect the bullets mass (not weight or force) while its falling by calculation its gravitational affects on nearby objects. According to Newton, the actual MASS of the object is independant of its speed. Even fired from a gun, according to newton's equations, the mass of the object would remain unchanged. Yes, the force, acceleration, and kinetic energy of the bullet would change, but the mass would not. Einstein says the MASS changes with velocity. Let's calculate the inertial mass of the space shuttle orbiting the earth. An orbiting space shuttle (right before re-entry) typically weighs 104326.2451kg and orbits at a speed of 27875 km/h. Thus, the velocity is 464583.33 m/s Using the equation: m(v) = 104326.2451kg / sqrt(1- (464583.33^2 / 299792458^2)) m(v) = 104326.4956kg Thus, the mass of the space shuttle is increased by its velocity by 250.5g or .0002401%. As you can see, it takes a lot of speed to increase the mass by any significant factor.