J.C.MacSwell

surfaces? right i'm confused now. On the website linked aboe it said that the event horizon was where the escape velocity was c. it then said that the photon sphere was outsie this and since orbital velocity is slower than escape velocity this should be the other way around[/b']. I think this is what i'm meaning i don't know i've confused myself.

I think it is for mass...but not for light!

yes but how can light orbit the blackhole if the escape velocity at that distance is less than c? is there some weird relativistic effect here? if something is going faster than escape velocity then it WILL escape(or should do at least) the area where the orbital velocity is c should be within the event horizon if the event horizon is the distance from the singularity where the escape velocity is c.

The event horizon is the point (surface) from which nothing (quantum effects aside) can escape. It is not near the point (surface) at which the escape velocity of any mass would approach c. This point (surface) is outside both the event horizon and photon sphere.

When you first posted your argument made sense to me, but it was because I was confusing the two points (surfaces again), so I had to think about it.

Does this other surface have a name?

Outside of the Event Horizon there is a Photon Sphere where light is able to maintain orbit.

 

Below the Photon Sphere You would need to go faster than light to even maintain an orbit. http://www.gothosenterprises.com/black_holes/static_black_holes.html

Is there another horizon outside the event horizon and photon sphere that corresponds to the escape velocity of massive particles that approach light speed? I think that may be the one you can (in theory) "climb" or accelerate out of as Insane Alien describes.

[

Oh, and I apologize for the "gravuty" error. "U" is pretty close to "I" on the keyboard, in my defense.

No bug deal

Just had an idea about this and i can't find any threads about it either.

Orbital velocities are slower than escape velocities' date=' so you could theoretically orbit a blackhole inside the event horizon(assume its so massive that there isn't a whole lot of sheer) without breaking any laws of physics(i think). To escape you could change your apoapsis till it is above the event horizon and still be going below c. when you get out side the event horizon you just bring your periapsis out of the event horizon by accelerating again and you could then accelerate to the escape velocity at that altitude. any flaws here?[/quote']

 

If this is the correct definition of "event horizon" then I think this should work (theoretically of course, don't try it at home )

Space only varies with motion.

Speed up and space-time shrinks.

And expands

the circumference shrinks and the radius stays the same.

This requires a material that has infinite tensile strength/stiffness and results in an infinite force.

Personally, I prefer Big Bang Model to Big Bang Theory. The evidence is limited not unlimited of course, but more significantly is largely untestable and based on a huge extrapolation. All of which is commendable under the circumstances and it seems it is a "best guess" at this time but the jury should still be out IMHO.

I'll guess 2!

53 for me!

I'll go 14!

All those string theorist jumping like rats off a sinking ship have to go somewhere!

Is there a relationship between inertial mass, rest mass and temperature? If a body's inertial mass and rest mass are the same then presumably its temperature is exactly zero degrees Kelvin (hypothetically of course). Might it then be possible to deduce the temperature of a body if you already knew the values both for rest and inertial mass ?

I could be wrong, but I always assumed the rest mass of an object to include it's temperature (or energy associated with temperature).

So the rest mass of an object would be greater than that of the sum of it's parts (constituent particles) assuming the above is correct.

For how long did The Universe exist before the Big Bang? A rough value will do.

3.1415926 billion years.

If it was forever, we would not have gotten to the big bang stage yet.

There are so many of you willing to answer a layman's question that I hope you don't mind a few more.

 

With my bicycle upside down(changing tire) I spin a wheel. The spokes appear to curve. I assume this is because the outer end of the spoke is travelling at a higher rate of speed than the inner portion. If I were to accelerate the rim to .999999c would the spoke curvatures be so great that the distance between the rim and the wheels hub appear to my eyes as to be close to zero? Could I asume that the apparent curvature of the spokes are now extremely exaggerated to the point where they appear to be flattening out? In other words the rim is closer to the hub.

 

Even when I spin the wheel by hand' date=' if I was to measure the distance between the rim and hub it would be less than when the wheel is stationary? Would the spokes because of their apparent curvature appear longer or do they retain same length even when the rim appears closer to the hub?

 

These questions are harder to write than answer. I hope that wasn't too confusing.[/quote']

 

The faster you spin it the further it gets from the hub.

400 is mine!

Not an educated guess. Just a GUT feel.

IMM has 222 posts.

 

dude' date=' PhysicsForums has 5 pages already on this game.[/quote']

 

Yourdads in Indiana

It's the love child of Johnny5 and geistkiesel.

Keep it up and you'll be the next on the list!

The most confusion, is, why the ICE-BOAT can travel even faster than wind??

It basically comes down to it's thrust to drag efficiency. It reaches a speed where the drag equals the thrust. Since the apparent wind is shifting further and further forward it is harder and harder to gain thrust to match the increasing drag (mostly aerodynamic drag on an iceboat) inspite of the increase in available energy.

Due to the efficiency of the iceboat this can still come at over twice the wind speed.

Blike was privately educated.

 

A ridicliously big goal means that you can count who's further rather than who got there first.

 

edit: yourdad' got his post in before me.

The tree was beaten by Yourdad by 2 minutes

edit: only 9,993 to go!

There should be an almost negligible time dilation/increased lifespan caused by the increased velocities and accelerations, if no other effects overwhelm it.

So' date=' why the final boat velocity isn't wind velocity + initial boat velocity??

 

Isn't that more logical??[/quote']

 

Why would it be?

 

Nothing in the above is an attempt to analyse the forces, accelerations final velocity etc. The relative wind speed can change, of course, with any change in the true wind or boat velocity. (speed and direction)

I suspect that the "anomaly" (in the OP) may simply be that while the gravitational field might be expected to fall away as you climb down a giant crater, it is seen to actually increase...and perhaps this increase is, in fact, due to a large, high-density meteorite embedded beneath it.

Or oppositely (albeit lacking gravity not antigravity) the crater itself would create an anomaly at the projected "surface" (average radius) compared to what it would be if the crater didn't exist or was filled with moon dust.

Hmm.... so, at what speed is the boat moving then??

deduct the apparent wind vector from the true wind vector and you get the boat speed (velocity) vector.

[url']http://en.wikipedia.org/wiki/Capacitor[/url]

So a capacitor is a pair (or more) of oppositely charged conductors. I had it pictured as a single charged (positive or negative) conductor.

So either pole won't discharge to ground due to the proximity and opposite charge on the other?

If only touching one of the poles of the capacitor' date=' thus not creating a complete cicuit ?

.[/quote']

 

Do capacitors have poles?

 

Capacitor contact to any ground would create current flow. (??)