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Theory of relativity
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.Roy
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RE: Theory of relativity
Its also possible to slow the speed of light. Light travels slower according to what it has to go through. For example light going through air is faster then light going through water. So if someone can find a really THICK material, then they can slow the speed of light. For example you can be in a room and walk out of it, then go outside and look through the material and you can see yourself still in it.
11-21-2005 04:17 PM
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RE: Theory of relativity
Another dodgy example: Let's say im standing here, while cookierevised is traveling at *almost* the speed of light (:P). Now let's say that Tasha and Calvin are standing still in my point of view and then they both jump at the same time. I, of course, see that they jumped at the same time (because we are in the same reference), while cookie, who's traveling almost at the speed of light, sees that they jumped at different times :p.
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11-21-2005 04:22 PM
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RE: Theory of relativity
Also i think its possible to see in the past.

If you look at a certain position and go faster then the speed of light, you will see things that happened before ( but in reverse).
11-21-2005 06:03 PM
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John Anderton
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RE: Theory of relativity
quote:
Originally posted by Madman
It is impossible to go beond the speed of light because it would require an infinate amount of energy (or somthing like that).
Well ..... its basicallay proved by einsteins rest mass to velovcity mass equation

m = (m0) / (1-v^2/c^2)^1/2

Where m is you mass at velocity v
m0 is your mass at rest (that zero is a subscript ;))
c is the velocity of light

Thus as you velocity approaches the speed of light ... your mass becomes higher. You cant exceed the velocity of light cause well .... root of negative numbers are imaginary;)

So for any given case
v^2/c^2 <= 1

v <= c ;)

quote:
Originally posted by Madman
and it also covers "The faster you go the slower time goes".
Remember this example. If there are 2 identical twins. You tell one to stand on a planet and you tell the other to go at the speed of light till a star and comeback. If he comes back after one year by his his time ... his brother may have aged about 50 years ...
I dont have the mathematical proof for this, but this is what happens.

quote:
Originally posted by SikStyles
wasnt the theory of relativity that when you sit in a room with a hot chick an hour seems like a second and when you sit on a hot stove a second seems like an hour
:dodgy:
FFS. Dont spam in a serious thread.

quote:
Originally posted by ShawnZ
You don't transform into light if you go the speed of light. (You'll turn yourself into a black hole though)
Well ... NO YOU DONT
As i have already explained in Einsteins equation, as you velocity increases, your mass does too but this is only possiple as long as,
v < c
Once you reach the velocity of light, all your mass (the one that you had and the one that you had gained due to your velocity) gets converted into pure energy. No mass can exist at the velocity of light well except for protons is light (according to De Broglies Hypothesis / Dual Nature Of Light) [quanta (packets of energy; they dont have mass^o)) are a different story. They are energy]

And btw, speed of light isnt the fastest thing. Its been broken .... about 10 years back |-)

Well a few british scientists took a dark tube, made a small hole, let light enter and reflected it in one direction. Then from behind it the let a laser loose. They wanted to find the velocity of the laser under different laser. Note that this is a special type of laser. They noticed that under certain conditions the particles of the laser reached before that of light.

quote:
Originally posted by Underlord
The only thing that can travel faster than light is space. In a black hole space is being sucked in faster than light travels, so light itself cannot escape. Very simple explination.
Underlord, thats not true. I could explain if anyone wants to know ...

When a star burns normally there are two forces acting upon it, its high gravitational force acting inward (high because ..... it holds the whole planetary system together dont they) and the force due to contunious nuclear fusion (which acts outward)

It is the magnitude at of these forces that determines the size of the star at any instant. It remains like this for say a few kazillon years :P

Then eventually its low on fuel (hydrogen), it swells up for a few millenia (short time for starts pfft :P) cause the outward force due to nuclear fusion decreases due to a lower combustion rate. Then it runs out of hydrogen and its screwed cause it still has the same gravitational force but the outward force is zero. Thus it shrinks but as it does, its mass it still constant but its volume tends to zero
Density = Mass / Volume

Thus it has infinite density and thus infinite gravitational force. Thus not even light can excape it ;)

quote:
Originally posted by CookieRevised
They are objects. Only objects with an extremely great mass (and because of that extremely small... they think). Black holes aren't all the same either, some have a greater mass than others.
O.o
Their mass is the mass of the helium remaining from nuclear combustion !!! The gravitational force comes from their negligible volume and high mass.

They think ??? Who think ?? Do you mean i think :P

quote:
Originally posted by CookieRevised
Black holes not only absorb matter, they also emit stuff.
Wasnt that a huge controversy !!! Stephen Hawking was wrong and no one figured it out for what ... 40 odd years ??

There was this one guy in the atomic research center here (where i live) and he was saying all along that what stephen hawking said was wrong. Black holes need to emit stuff as well, but people asked him how dare he question stephen hawking and stuff .... for about 30-35 years he was tormented ..... finally when stephen hawking accepted his mistake this guy was vindicated :P
quote:
Originally posted by CookieRevised

Also, if the force of gravity in an object is too great for a beam of light to escape we (thus the observers) would see only blackness and call that object a black hole.
The perfect definition of a black hole :cheesy:

This post was edited on 11-21-2005 at 07:19 PM by John Anderton.
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11-21-2005 06:58 PM
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RE: RE: Theory of relativity
quote:
Originally posted by John Anderton
quote:
Originally posted by CookieRevised
They are objects. Only objects with an extremely great mass (and because of that extremely small... they think). Black holes aren't all the same either, some have a greater mass than others.
O.o
Their mass is the mass of the helium remaining from nuclear combustion !!! The gravitational force comes from their negligible volume and high mass.

They think ??? Who think ?? Do you mean i think :P
No, "they" (points finger to wierd scientists)... :p

Studies suggest black holes can have different masses. aka: it doesn't have  infinite mass at all, and it can be different from the other black hole. Black holes are not so "black", and perhaps not "holes" either. The volume and masses of black holes can't be measured per-se, it is done in theory and calculation, but even that theory (eg: when you reverse the formula of calculating escape velocity near the event horizon) suggests black holes have different masses. Heck, if you say it has infinite mass, many famous important theories wouldn't even work.

As for the size, that's also pure theory and done with calculation based upon current physicis as we know it. Thing is, these current physics don't apply 100% when dealing with such stuff. Also, a black hole is more than simply "the extremely small thing" which sucks everything in; as that is called the singularity in the middle of a black hole. One black hole can have a larger inner and/or outer event horizon than the other, meaning the gravity is different than the other, meaning the mass is smaller/greater. eg: a solar mass black hole has a radius of +-3 kilometers, a 10 solar mass black hole has a radius of +-30 kilometers, etc. And since this mass is close to infinite, but not infinite, the singluarity is also not infinite small, but can even also vary in volume. Hence you also have something called supermassive black holes with a life span of millions of times the lifespan of the universe and mini black holes with a life span smaller than the lifespan of the universe and as small as the sun.

quote:
Originally posted by John Anderton
quote:
Originally posted by CookieRevised
Black holes not only absorb matter, they also emit stuff.
Wasnt that a huge controversy !!! Stephen Hawking was wrong and no one figured it out for what ... 40 odd years ??
yeah but even Stephen Hawking said they emitted stuff. The emittion I talk about is the single radiation beam comming from the polar axis from black hole as it absorbs energy/matter, almost like a pulsar. Not about the radiation discs and other stuff which is emitted from the material itself sucked in.

EDIT: turns out the stuff which is emitted and which I meant is called Hawking-radiation :P

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Ps: [self-split] Theory of relativity
Edited: added url to image

This post was edited on 11-22-2005 at 08:47 PM by CookieRevised.
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11-22-2005 01:11 AM
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RE: RE: Theory of relativity
quote:
Originally posted by John Anderton
quote:
Originally posted by Underlord
The only thing that can travel faster than light is space. In a black hole space is being sucked in faster than light travels, so light itself cannot escape. Very simple explination.
Underlord, thats not true. I could explain if anyone wants to know ...

When a star burns normally there are two forces acting upon it, its high gravitational force acting inward (high because ..... it holds the whole planetary system together dont they) and the force due to contunious nuclear fusion (which acts outward)

It is the magnitude at of these forces that determines the size of the star at any instant. It remains like this for say a few kazillon years :P

Then eventually its low on fuel (hydrogen), it swells up for a few millenia (short time for starts pfft :P) cause the outward force due to nuclear fusion decreases due to a lower combustion rate. Then it runs out of hydrogen and its screwed cause it still has the same gravitational force but the outward force is zero. Thus it shrinks but as it does, its mass it still constant but its volume tends to zero
Density = Mass / Volume

Thus it has infinite density and thus infinite gravitational force. Thus not even light can excape it ;)

I know how a black hole is formed. My explination wasn't meant to be inconceivably complex. Also it isn't possible for something to have "infinite" density. This would break the laws of quantum mechanics. The volume of the object is almost negligible, but it is there.

quote:
Since light has no mass how can it be trapped by the gravitational pull of a black hole?

Newton thought that only objects with mass could produce a gravitational force on each other. Applying Newton's theory of gravity, one would conclude that since light has no mass, the force of gravity couldn't affect it. Einstein discovered that the situation is a bit more complicated than that. First he discovered that gravity is produced by a curved space-time. Then Einstein theorized that the mass and radius of an object (its compactness) actually curves space-time. Mass is linked to space in a way that physicists today still do not completely understand. However, we know that the stronger the gravitational field of an object, the more the space around the object is curved. In other words, straight lines are no longer straight if exposed to a strong gravitational field; instead, they are curved. Since light ordinarily travels on a straight-line path, light follows a curved path if it passes through a strong gravitational field. This is what is meant by "curved space," and this is why light becomes trapped in a black hole.

From this one could conclude that space is falling into the black hole.

There is more than one way to see things. Everything isn't black and white.
11-22-2005 05:49 AM
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RE: Theory of relativity
The biggest problem with defining things like black holes is that there is no true way to measure it and test to see where everything that is taken into a black hole ends up. For all we know, everything that goes into a black hole ends up in another dimension. Until we are able to travel into a black hole and come back out without being destroyed or lost forever, we will never truly know what happens when something enters a black hole.

The reason that a black hole is "black" is because of the lack of light allowed to be maintained in the area. It has no true color, but we (humans) visualize black as the absence of light and color.

As for the speed of light, there are many theories that may or may not apply. Again, the biggest problem is the lack of a proper ability to test those theories. For all we know, there could be a way to circumvent the speed of light by "stepping" out of this dimension/reality/whatever at one point and "stepping" back in at another. Though I read about the theory in a sci-fi novel (Orson Scott Card's Children of the Mind) I think it's something that is entirely possible given the nature of the cosmos as we know it (if you want a more detailed explaination, let me know or check out the book for yourself).

I'll stop there for now because my head hurts and I could ramble on about this subject for hours. :lipsrsealed:
11-22-2005 06:32 AM
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RE: Theory of relativity
quote:
Originally posted by Underlord
Everything isn't black and white.
Thats the best way to put it imo :P
We need a lot more research into such stuff. I would have loved to take up such subjects at university :P

Where did you get that quote from ?? I wanna read more :D

You know whats coincidence. Last night i was thinking of the same thing whilst comming home .... even before i saw this thread :|
freaky !!!

Anways, i think its kinda related to this topic cause i am gonna ask something about the 4th dimension.

Well we can only percieve life in 3 dimensions. We can sense the 4th dimension but we cant actually see it or travel through it.
Consider an ant or well .... a common house gecko (lizard) which can see everything in 2 dimensions .... it knows only 2 dimesions viz length (forward - backward axis) and bredth (left - right axis) it doesnt know anything about the height (up - down) axis.

Now assume it is walking on a ceiling and it falls down and lands on a baloon floating at the center of the room. Now where ever it goes, it cant escape since it has no idea that this is a baloon and he is above the ground (or below the ceiling) since he doesnt have a sence of height.
If there was a second gecko on the ceiling, how much ever he may try, he cant find the 1st gecko. See my point. We as humans can clearly see whats happening but the geckos wouldnt understand whats going on.

Consider our case, what if we managed to come in a similar condition. If one man goes into such a "positon" then we would nto be able to find him simply cause "time" isnt a dimension we can travel in.
So we as humans cant understand whats going on but there may be a higher species (imagine there are :P) that can see whats going on cause they percieve the world in 4 dimensions.

So how can we imagine what time looks like ?? I mean, you can see 3d stuff. what if you could see stuff in 2d then you could know what you are missing, the sence of depth that your eyes provide in everything (photos arent exactly 2d are they ?? you can still make out which friend of yours is standing in front and whos at the back. Im saying you should see both your friends in a picture standing side by side even though one is closer to the camera)

Then could you imagine what the time axis looks like ??

PS: Does anyone know that east asian (Japaneese or korean i think) kinda scientist who has done a Phd in Theoretical Physics and keeps comming on the discovery channel from time to time. He is simply amazing :| I think he got his Phd from MIT ^o)
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11-22-2005 06:57 AM
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RE: Theory of relativity
One thing to dispute here: black holes are NOT objects.
In the loosest possible terms a black hole is a region of space that has so much mass concentrated in it that there is no way for a nearby object to escape its gravitational pull. Basically this mass concentration has an escape velocity greater than c, so not even light can escape. The idea of such a mass concentration that even light could not escape from originates with Laplace in the 18th century, then straight after Einstein's theory of special relativity Karl Schwarzschild managed some hypothetical solutions to the equations that described such an object. It wasn't until the 1930s that people thought "wow, these things might actually exist" - Oppenheimer, Volkoff, Snyder were the main researchers. They showed that when a sufficiently massive star runs out of fuel, it is unable to support itself against its own gravitational pull, and it should collapse into a black hole. That's as far as you can take it with special relativity, to advance you have to consider general relativity (the harder version).
In general relativity, gravity is a manifestation of the curvature of spacetime. Massive objects distort space and time, so that the usual rules of geometry don't apply anymore. Near a black hole, this distortion of space is extremely severe and causes black holes to have some very strange properties. In particular, a black hole has something called an 'event horizon.' This is a spherical surface that marks the boundary of the black hole. You can pass in through the horizon, but you can't get back out. In fact, once you've crossed the horizon, you're doomed to move inexorably closer and closer to the 'singularity' at the center of the black hole.
It is this singularity that is, in essence, the black hole. At the singularity our laws of physics no longer apply, the singularity cannot be considered an object at all. In conclusion a black hole consists of this singularity and the event horizon... a region of space. Not an object. Even the event horizon is not as well defined as you would think, due to Hawking's solution of the Black Hole Information paradox.
A note on what is emitted from a black hole: only one thing is emitted, Hawking radiation. The laws of quantum physics state (simplified :p) that the information emitted, when a black hole evaporates, about the matter inside the black hole can never be completely wiped out. Hawking's 1976 black hole model (whereby a black hole starts losing mass as soon as it has formed via radiating energy) showed that the data was totally destroyed, thus creating the paradox. Hawking's argument was that the intense gravitational fields of black holes somehow unravel the laws of quantum physics. In essence, Hawking's new black holes now never quite become the kind that gobble up everything. Instead, they keep emitting radiation for a long time, and eventually open up to reveal the information within. They also, unlike classic black holes, do not have a well-defined event horizon that hides everything within them from the outside world. Hence the nont-well-defined event horizon. This is the only emission from a black hole.
There are two indirect ways to detect black holes: x-ray binary systems and mass measurements on the centres of galaxies.

Edit: There is a further solution to black holes via string theory but it's hella complicated and I don't have the patience to explain it. :p

This post was edited on 11-22-2005 at 02:39 PM by emit.
11-22-2005 02:35 PM
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RE: RE: Theory of relativity
Ok, going into a bit more detail now :p

quote:
Originally posted by Time
One thing to dispute here: black holes are NOT objects.
In the loosest possible terms a black hole is a region of space that has so much mass concentrated in it that there is no way for a nearby object to escape its gravitational pull.
(...)
At the singularity our laws of physics no longer apply, the singularity cannot be considered an object at all.
Since the singularity has a mass it can be considered an object; a quantum mechanical object.

quote:
Originally posted by Time
They showed that when a sufficiently massive star runs out of fuel, it is unable to support itself against its own gravitational pull, and it should collapse into a black hole.
Yes and no.

Certainly not all stars collaps in black holes at all. It is very rarly that it does.

You can devide stars in roughly 2 categories:

1) Stars with masses equal or smaller than +-10 times the mass of the Sun.
2) Stars with masses greater than +-10 times the mass of the Sun.



When a star with a mass equal or smaller than +-10 times the mass of the Sun cools down, and thus is ending its "life cycle" it gets bigger and bigger up to a red giant.

When growing it also looses layer after layer of material. When the last layer of material is emitted only the core remains. This emitted (last) layer in space is called a Nebula.

After that the core implodes into itself and is crushed down to a white dwarf (+-size of the earth).

When the density of the white dwarf is large enough, this core will on his turn implode and will cause such a shockwave that all material surrounding it and including the core is destroyed, this is called a nova or super nova type 1. Nothing will remain.

When the density of the white dwarf isn't large enough, the white dwarf will turn into a stable white dwarf and nothing will happen anymore.



When a star with a mass bigger than +-10 times the mass of the Sun cools down, and thus is ending its "life cycle" it gets bigger and bigger up to a red or blue supergiant.

Again this supergiant will eventually cause a super nova. But this time a super nova type 2. The core of the star will not be destroyed, instead it will be crushed down to a neutron star (+-10km).

When the neutron star spins fast enough, it will become a pulsar. Again nothing further will happen, although the gravity is extremely large, the rotation prevents it from further imploding.

But when it doesn't rotate fast enough and has a big enough mass, the gravity wins and only then will it turn into a black hole as there is no or not strong enough anti-gravity force to prevent it.



quote:
Originally posted by Time
In particular, a black hole has something called an 'event horizon.' This is a spherical surface that marks the boundary of the black hole. You can pass in through the horizon, but you can't get back out. In fact, once you've crossed the horizon, you're doomed to move inexorably closer and closer to the 'singularity' at the center of the black hole.
Yes and no.

A black hole has an outer event horizon and an inner event horizon. The outer event horizon is the space where you will begin to feel the gravitational pull of the black hole. The inner event horizon is the region you can not escape anymore as the velocity needed to escape that must be greater than the speed of light.

It is this inner event horizon which is called the Schwarzschild region.



One black hole isn't the same as the other black hole and they can have different masses. The mass can vary from a few solar masses up to the combined mass of millions of galaxies put together.

And because of the mass difference, also the sizes can vary from extremely small as with mini blackholes to massivly large as with super black holes.

Black holes can be divided into two main types, or rather their type of singularities:

1) A point singularity. This type of black hole is what most people think of as a black hole. The point singularity is formed from stationary, non-rotating matter; The black hole doesn't rotate. This is the blackhole associated with Schwarzschild.

2) A ring singularity. The rotating neutron star isn't crushed into a single point singularity but into a ring because of the rotation. Thus this type of black hole is formed from rotating matter. Space and time surrounding this singularity will be dragged around like a vortex.

And this last type is the interesting one, and the one which is predicted and prooven by Einstein's general relativity theory.

The general relativitly theory says and proofs that you could go into this ring singularity and when you will return you will return before the time you started going into the black hole.

Note that Einstein didn't liked this and was greatly disturb by this as this allowed for possible time travel!

Thus Einstein, together with Rosen, also calculated/prooved that this region within this ring singularity, can be interpreted as some kind of bridge to another spacetime and thus somehow connect different parts of spacetime. Subsequently, these are called Einsten-Rosen bridges or we know these better as wormholes.

Up until now, this theory is still not proven 100% wrong. Although the theory of Schwarzschild is one way to proof it wrong. Or rather only to proof that you can't actually travel thru the wormhole to the other universe, you would be stuck in the middle, but you could see the other universe though (The Schwarzschild Bubble and stuff). On the other hand, that same theory of Schwarzschild also allows for the use of negative mass matter which actually could keep the wormhole open to pass thru and thus create a stable Schwarzschild wormhole.

While this negative mass matter is strange and doesn't fit in our current physics (for 100%), we also know there are very exotic things going on when dealing with black holes and we know that there must be something to compensate matter as we know it (black matter, black energy, etc...) in other words: who knows... at least it isn't totally impossible.



quote:
Originally posted by cardshark
Though I read about the theory in a sci-fi novel (Orson Scott Card's Children of the Mind)
That theory is exactly Einstein's General Relativity Theory (well, that is: part of)

quote:
Originally posted by groessl35
But anyways... I don't think it really bends... and sucked into the hole... if the force of gravity in a black hole is too great for a beam of light to escape... would it stand still?
The light emitted from the black hole can't escape gravity and thus it is bend back to the black hole (think of a magnetic field, or solar flames which bend back to the sun), hence we can't see it.

Only when a person is sucked into a black hole and passes the inner event horizon, the observer who is watching will see the sucked in person as if he/she is standing still (forever).

quote:
Originally posted by .Roy
Also i think its possible to see in the past.

If you look at a certain position and go faster then the speed of light, you will see things that happened before ( but in reverse).

no, you wont. You would go so fast that the light emitting from those events will never reach you, aka you would see blackness.

quote:
Originally posted by John Anderton
quote:
Originally posted by Madman
It is impossible to go beond the speed of light because it would require an infinate amount of energy (or somthing like that).
Well ..... its basicallay proved by einsteins rest mass to velovcity mass equation

m = (m0) / (1-v^2/c^2)^1/2

Where m is you mass at velocity v
m0 is your mass at rest (that zero is a subscript ;))
c is the velocity of light

Thus as you velocity approaches the speed of light ... your mass becomes higher. You cant exceed the velocity of light cause well .... root of negative numbers are imaginary;)
yes, they are imaginary but that doesn't mean it can't exist or be used to develop further theories (heck the imaginary number system and imaginary algebra is teached in every school). And this is actually were the theory of Schwarzschild comes into play; together with white holes, his "bubbles" and wormholes.

This post was edited on 11-22-2005 at 08:39 PM by CookieRevised.
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11-22-2005 06:37 PM
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