energy in an atom

[Pommie]

Maybe, but it'll be hard to tell because one rotation is a VERY long time. We can look at older Galaxies and guess that one of the disc type ones was like ours once, but there is no way to prove it.

If what you say is correct then spiral galaxies would only appear fleetingly and be very rare. They do however seem to be relatively abundant.

Mike.

 

[dknguyen]

As you guys appear to understands gravity, can you please explain the following.

It is a well known fact that planets orbit around suns. The nearer the planet to the sun the faster it must orbit. The same is true for stars orbiting around galaxies. With this in mind, how can a spiral galaxy be stable? Surely, after a few rotations the spiral will turn into a disc.

Mike.

You have to remember that spiral galaxies don't really have "trailing spiral arms" so they can't wind up into elliptical galaxies. The "arms" are due to those parts of the galaxy emitting more light than the "dark empty space between the arms". So they're both elliptical really...just one has dark areas to make it look like empty space. There is still "galactic mass stuff" between in the dark spots between the so called "arms".

 

[Pommie]

You have to remember that spiral galaxies don't really have "trailing spiral arms" so they can't wind up into elliptical galaxies. The "arms" are due to those parts of the galaxy emitting more light than the "dark empty space between the arms". So they're both elliptical really...just one has dark areas to make it look like empty space. There is still "galactic mass stuff" between in the dark spots between the so called "arms".

But, even if "dark" areas exist, why don't the light areas get spread around due to the speed differential between matter at different radii?

Mike.

 

[dknguyen]

But, even if "dark" areas exist, why don't the light areas get spread around due to the speed differential between matter at different radii?

Mike.

Now that is a different question

The reason is still uknown and unproven. But here is a promising theory: Google "Density-Wave Theory of Galactic Spiral Structure". It's a doozy.

Here is are some simple links presearched for your amusement:
http://www.daviddarling.info/encyclopedia/D/densitywave.html
http://www.astronomynotes.com/ismnotes/s8.htm
http://curious.astro.cornell.edu/question.php?number=199

The last link also mentions the Stochastic Self-Propagative Star Formation

 

[Hero999]

This may sound mind-blowing, but we actually understand very little about gravity. There is even a big argument over how fast gravity travels- for example, if the sun were suddenly yanked away from the center of the solar system by an inconceivably huge rope, how long would it take for the Earth's orbit to change? There have been some various evidence, the best evidence shows much faster than the speed of light but apparently still not instantaneous.

If that's the case it'd be cool if we could create a time varying gravitational feild and use it for communication. I suppose it would act like a wave traveling through space. There again I know I'm talking about the kind of thing you see in science fiction films.

Just another thing, am I right in that mass and energy are the same thing? Gravity bends light and when an atom is split all the resulting particals have a lower mass than when they were bound together in the origional atom despite the fact than none of them have disappeared.

 

[phalanx]

I think this is the energy from surrounding temperature that keep things (including electrons) in activity. That's the reason cfo contraction and expansion. AT absolute zero all activities will seize electrons will fall into the nucleus.

What do others think?

Aily

There is still quantum energy in the atom which would prevent that situation.

 

[Optikon]

Uhhh, electrons are matter aren't they? I don't think you can define some matter as a tendency and other matter as things.

How much does 10^10 electrons weigh? I think electrons have rest mass only.

 

[Gaston]

so quantum energy is always there? without takeing from the environment and lasting forever?

 

[Sceadwian]

That's not so clear Gaston. Even empty space has a certain amount of energy associated with it, but aside from the theories and whatever has been experimentally proven so far, there's no known way to harness it. (I could be wrong) There's also no way of knowing what manipulation of raw space would actually do. You're talking about actually draining energy from the fabric of spacetime itself. Creepy stuff.

 

[akg]

How much does 10^10 electrons weigh? I think electrons have rest mass only.

9.1E-21 Kg

 

[dknguyen]

You're talking about actually draining energy from the fabric of spacetime itself. Creepy stuff.

Great, so then humanity won't be destroying the environment, we'll just be depleting spacetime.

 

[Pommie]

Jeees, you young guys worry about depleteing space time. I just wonder where the next sensible space time theory will come from!!!

If "insert relevant imaginary freind" wanted us to wory about such things, she would have kept her knickers on.!!!!

Mike.

 

[Analog]

In some senses, you can look at like a planet orbiting a sun, but in reality that metaphor will fall through. It may not be moving at all in the conventional sense.

Gravity is seen as one of the basic 4 forces. Electromagnetism (electricity and magnets are seen as 2 sides of the same coin), gravity, Strong, and Weak.

This may sound mind-blowing, but we actually understand very little about gravity. There is even a big argument over how fast gravity travels- for example, if the sun were suddenly yanked away from the center of the solar system by an inconceivably huge rope, how long would it take for the Earth's orbit to change? There have been some various evidence, the best evidence shows much faster than the speed of light but apparently still not instantaneous.

The irony is that while gravity is the most obvious force you sense every day, it's also one of the weakest. It's hard to get a readable force from a lab experiment because the gravity from even a 10-ton sphere of iron is still phenomenally small. With magnetism we can make a concentrated field with an electromagnet, not so with gravity.

Actually, there is strong speculation that there is a 5th force, tied to dark matter, that is actually a repulsive force! It is speculated that this force (based on Einstein's cosmological constant) is what is accelerating the expansion of the universe.

 

[guen_max]

In relation to energy in atoms...what about atomic fusion?Is it closely possible these days? Doesn't it produce nuclear energy of some sort? Remember Doc Ock from Spiderman? Or I'm just believing hollywood too much?

 

[Phasor]

If "insert relevant imaginary friend" wanted us to wory about such things, she would have kept her knickers on.!!!!

When you say "your 'imaginary friend'", do you mean Alice and Bob?

 

[kchriste]

what about atomic fusion?Is it closely possible these days

It's been done already. The problem is that it takes more energy to start a controlled fusion reaction than you get out of it. Hydrogen bombs are the only efficient method so far. Go figure!