Can light not escape from a black hole because
the gravitational force is equal in every direction
Does the force exerted vary depending on type of hole

Water is the only liquid that expands when frozen
Given that the molecules would contract when going
from liquid to solid why is this ? Why not for other liquids

Different planets have different atmospheres
This is because of their chemical composition so
does that mean gravity is faster where the elements
are lighter and slower where they are heavier { in the same
way that air is thinner at an altitude and thicker on the ground ]

1) the greater gravity is, the greater the escape velocity needed for any particle, even light to escape. In order to escape a black hole, you need an escape velocity that is greater than the speed of light. Hence, nothing can escape a black hole's gravitational pull.

2) I cannot answer as to water, I think it has something to do with the ice crystals and the way arrange themselves when water turns to ice.

3) Gravity depends greatly on mass. Whether something is made of heavy or light elements does not play a role. Density plays a role, mass and distance from the centre plays a role. And what do you mean by "faster gravity"? Gravity cannot be faster or slower, it is a force, not velocity/speed. Gravity can be stronger or weaker depending on factors such as mass and density.

Darkchilde wrote:
3) Gravity depends greatly on mass. Whether something is made of heavy or light elements does not play a role. Density plays a role, mass and distance from the centre plays a role. And what do you mean by "faster gravity"? Gravity cannot be faster or slower, it is a force, not velocity/speed. Gravity can be stronger or weaker depending on factors such as mass and density.

Gravity does travel at C, though. (Newton, btw, realized that if gravity had infinite speed, it would require a flat universe.)

Zwaarddijk wrote:

Darkchilde wrote:
3) Gravity depends greatly on mass. Whether something is made of heavy or light elements does not play a role. Density plays a role, mass and distance from the centre plays a role. And what do you mean by "faster gravity"? Gravity cannot be faster or slower, it is a force, not velocity/speed. Gravity can be stronger or weaker depending on factors such as mass and density.

Gravity does travel at C, though. (Newton, btw, realized that if gravity had infinite speed, it would require a flat universe.)

At what speed does it travel?

Sityl wrote:

Zwaarddijk wrote:

Darkchilde wrote:
3) Gravity depends greatly on mass. Whether something is made of heavy or light elements does not play a role. Density plays a role, mass and distance from the centre plays a role. And what do you mean by "faster gravity"? Gravity cannot be faster or slower, it is a force, not velocity/speed. Gravity can be stronger or weaker depending on factors such as mass and density.

Gravity does travel at C, though. (Newton, btw, realized that if gravity had infinite speed, it would require a flat universe.)

At what speed does it travel?

c, sorry, accidental caps. gravity travels at c.

surreptitious57 wrote:Water is the only liquid that expands when frozen

From here:

If, as observed in most cases, a substance is more dense in the solid than in the liquid state, the melting point will increase with increases in pressure. Otherwise the reverse behavior occurs. Notably, this is the case of water, as illustrated graphically to the right, but also of Si, Ge, Ga, Bi.

Zwaarddijk wrote:

Sityl wrote:

Zwaarddijk wrote:

Darkchilde wrote:
3) Gravity depends greatly on mass. Whether something is made of heavy or light elements does not play a role. Density plays a role, mass and distance from the centre plays a role. And what do you mean by "faster gravity"? Gravity cannot be faster or slower, it is a force, not velocity/speed. Gravity can be stronger or weaker depending on factors such as mass and density.

Gravity does travel at C, though. (Newton, btw, realized that if gravity had infinite speed, it would require a flat universe.)

At what speed does it travel?

c, sorry, accidental caps. gravity travels at c.

The gravitational field expands at c. The hypothetical graviton particle may travel at c, if it is massless.

surreptitious57 wrote:

Water is the only liquid that expands when frozen
Given that the molecules would contract when going
from liquid to solid why is this ? Why not for other liquids

Water is not the only liquid.
Wikipedia is your friend;

'The solid form of most substances is denser than the liquid phase; thus, a block of most solids will sink in the liquid. However, a block of ice floats in liquid water because ice is less dense. Upon freezing, the density of water decreases by about 9%.[20] The reason for this is the 'cooling' of intermolecular vibrations allowing the molecules to form steady hydrogen bonds with their neighbors and thereby gradually locking into positions reminiscent of the hexagonal packing achieved upon freezing to ice Ih. Whereas the hydrogen bonds are shorter in the crystal than in the liquid, this locking effect reduces the average coordination number of molecules as the liquid approaches nucleation. Other substances that expand on freezing are silicon, gallium, germanium, antimony, bismuth, plutonium and other compounds that form spacious crystal lattices with tetrahedral coordination.'
http://en.wikipedia.org/wiki/Properties_of_water

Can the absolute centre of the Universe be
located or least calculated [ and if not why ]

Given that the seven dimensions can not be
referenced [ due to them being impervious to
light ] how can M Theory if true ever be proved

Why is gravity referred to as universal [ implying
that it is a cosmological constant ] when even with
in the Solar System it is not the same for every body

Is the rate that all the galaxies retreat from each other an
exponential one { as pertains to degree of acceleration and
not the actual distance ] and when shall this reach a state of
equilibrium [ since perpetual motion is physically impossible ]

Will the theory of quantum gravity be discovered within our life
time : and will relativity and quantum mechanics become invalid
when it does : and will Einstein s reputation be subject to revision

surreptitious57 wrote:Can the absolute centre of the Universe be
located or least calculated [ and if not why ]

No, in most standard theories our cosmos is either spatially infinite or something like a 3 dimensional version of a sphere. If it's spatially infinite it doesn't have a centre - think of an infinite line - the centre is at zero right ? because there are as many points to the right as to the left ? Actually that doesn't work - I can take the point "1" and for every point to the right I can find an analogous point to the left, so "1" is also the centre. In fact they're all the centre, so I might as well say there isn't a centre. Same for the infinite case.

Also if the universe is like a 3 sphere surface there obviously isn't a centre either.

This is implied by what is sometimes called the cosmological principle - that on the large scale the universe is the same everywhere. There arnen't any special points. "large scale" is important because there are some local irregularities like stars and galaxies...

surreptitious57 wrote:
Given that the seven dimensions can not be
referenced [ due to them being impervious to
light ] how can M Theory if true ever be proved

You mean the 7 extra dimensions ? There are some predictions that interactions can occur in which energy is transferred to these extra dimensions, in which case we would see missing energy in our experiments.

surreptitious57 wrote:
Why is gravity referred to as universal [ implying
that it is a cosmological constant ] when even with
in the Solar System it is not the same for every body

Universal just means that all matter acts as a source of gravity and all matter reacts to gravity. It doesn't imply that all matter reacts identically, but the laws which govern by how much it reacts are universal.

surreptitious57 wrote:
Is the rate that all the galaxies retreat from each other an
exponential one { as pertains to degree of acceleration and
not the actual distance ] and when shall this reach a state of
equilibrium [ since perpetual motion is physically impossible ]

It isn't really a "motion", it's an expansion of space. There is no reason for it to reach an equilbrium. The exponential phase is called inflation, this happened and stopped a long time ago.

surreptitious57 wrote:
Will the theory of quantum gravity be discovered within our life
time : and will relativity and quantum mechanics become invalid
when it does : and will Einstein s reputation be subject to revision

Don't know when it will be discovered. They will still continue to hold in the limits in which they apply today. They had better do, since otherwise the quantum theory of gravity is wrong! QG will just extend the arena over which physics is able to make predictions. Einstein's reputation is untouchable - his theories have made superb predictions which have been verified. This cannot change unless you go back in time and change history!

surreptitious57 wrote:Can the absolute centre of the Universe be
located or least calculated [ and if not why ]

The centre is the point of observation. You are therefore the centre of the Universe.

rainbow wrote:

surreptitious57 wrote:Can the absolute centre of the Universe be
located or least calculated [ and if not why ]

The centre is the point of observation. You are therefore the centre of the Universe.

He's not the centre, and you're not the centre, I'm the centre

twistor59 wrote:

rainbow wrote:

surreptitious57 wrote:Can the absolute centre of the Universe be
located or least calculated [ and if not why ]

The centre is the point of observation. You are therefore the centre of the Universe.

He's not the centre, and you're not the centre, I'm the centre

Of course you are.

surreptitious57 wrote:Can the absolute centre of the Universe be
located or least calculated [ and if not why ]

The is no center of the universe. There was a thread about this very topic here. Check out my explanation here.

According to Brian Cox electrons have
a natural eternal life as far as physicists
know : now if this is true does it not violate
The Second Law Of Thermodynamics how ever

Is it true that Paul Dirac successfully managed to
unite quantum mechanics and relativity : why then
today are these two disciplines mutually incompatible

Is there any truth to the rumour that when Einstein was
a boy his teacher said he would never amount to anything
and made him face the wall as his fellow pupils mocked him

1) Nope. The second law of thermodynamics in its entropy formulation is derived from the notion that there are fundamental particles which behave in a stochastic fashion. It then makes a statement about their spacial relationship in statistical form. That also means that the 2nd law of thermodynamics is a macroscopic law - individual particles don´t neccessarily follow it, the lower the number of particles there are in a closed system, the more often entropy will actually decrease in it.

2) It´s not true. Dirac managed to treat a special case with a mix of both, but did not unify the theories. The main issue is the following: QM is a stochastic theory, i.e. it´s governed by probability theory. In probability theory you work with particular systems of sets - sigma-algebras - and in these only some set operations are allowed. If you allow others you can generate sets for which there is no consistent measure (i.e. the probabilities take all values in R, rather than one specific value in [0,1]). Relativity has curved space-time and it turns out that when you have a set of points in space time and then curve it you perform precisely the type of operation that is not allowed in probability theory. If you perform a double slit experiment, QM tells you the probability with which a photon hits your screen in a particular area. You distort space-time and thus the screen and for any area on the screen you find a probability of infinity, 0, 412, 0.7 all at once. GR isn´t only not reconcilable with QM, it has these issue with any stochastic theory, including population genetics and statistical mechanics.

3) Probably. That probably happened to everybody who was a student at that time at what Einstein described as an institution of learning focussed on rote learning and punishment - he spend 6 years at that school in Munich before moving to Swizerland where he entered the oldest secular school and in retrospect noted the contrast - here he found teachers whose authority derived from their knowledge, not from what they could do to you. That Einstein had bad grades is a myth however, stemming from the difference between the grading systems in Germany and Swizerland. In germany grades run from 1 (very good) to 6 (failed) whereas in Swizerland they run from 6 (very good) to 1 (failed). Einstein had a lot of 5s and 6s and an early biographer didn´t note that he hadn´t merely switched schools, but countries and thus grading systems.

susu.exp wrote:
2) It´s not true. Dirac managed to treat a special case with a mix of both, but did not unify the theories.

To be fair to Dirac though, he did unify special relativity with quantum mechanics, which was an enormous leap forward.

susu.exp wrote:
The main issue is the following: QM is a stochastic theory, i.e. it´s governed by probability theory. In probability theory you work with particular systems of sets - sigma-algebras - and in these only some set operations are allowed. If you allow others you can generate sets for which there is no consistent measure (i.e. the probabilities take all values in R, rather than one specific value in [0,1]). Relativity has curved space-time and it turns out that when you have a set of points in space time and then curve it you perform precisely the type of operation that is not allowed in probability theory. If you perform a double slit experiment, QM tells you the probability with which a photon hits your screen in a particular area. You distort space-time and thus the screen and for any area on the screen you find a probability of infinity, 0, 412, 0.7 all at once. GR isn´t only not reconcilable with QM, it has these issue with any stochastic theory, including population genetics and statistical mechanics.

Just to clarify: this irreconcilability of these stochastic theories with GR only happens if you consider the back-reaction of the stochastic processes on the spacetime geometry doesn't it? There's absolutely no reason why you can't do, say, statistical mechanics on a fixed curved spacetime background.

twistor59 wrote:To be fair to Dirac though, he did unify special relativity with quantum mechanics, which was an enormous leap forward.

Indeed. It´s just gravity that becomes the issue.

twistor59 wrote:Just to clarify: this irreconcilability of these stochastic theories with GR only happens if you consider the back-reaction of the stochastic processes on the spacetime geometry doesn't it? There's absolutely no reason why you can't do, say, statistical mechanics on a fixed curved spacetime background.

I´m not 100% sure, but I think that´s correct.

twistor59 wrote:There's absolutely no reason why you can't do, say, statistical mechanics on a fixed curved spacetime background.

Indeed, that's the Klein–Gordon equation.

There any real evidence that infinity exists such as
a mathematical proof for example : and if there is not
then is it not therefore presumptuous and unscientific for a
mathematician or physicist to automatically assume that it does

According to Einsteins Special Theory Of Relativity nothing
can travel faster than light : galaxies however are accelerating
from each other beyond that speed : this does not violate Relativity
but since we are part of one such galaxy it follows that any movement
within it must also be beyond light speed [ if moving in the same direction ]
So as I sit here typing this out I must be moving at beyond light speed too : in the
same way that I am also moving at 67 000 mph as I sit here as that is the rotational
axis speed of Earth : if this reasoning however is not logical then where exactly is the flaw

Has time always been linear and if not why
And why cannot it have existed before the Big Bang
What is the difference between a Theory a Law and a Principle
Why is it that infinity minus infinity should equal infinity instead of zero
If time can exist in a Universe that is devoid of matter how can it be measured
Why cannot the Theory Of Gravity be referenced in the equation of the Standard Model
If only four elementary particles are needed to create a Universe what purpose do the rest serve

How can one infinity which is quantitatively less than another infinity still be infinite :
such as for example the infinity of positive numbers compared to the infinity of all numbers

This letter appeared in Psychology Now : Is it true as it infers Einstein is wrong :
I think Professor Tallis is right to be suspicious in Issue 87 of the mathematicians habit of
treating their tools as though they were real : A good example is Special Relativity, accounts of
which give the impression that time slows or speeds up according to your relative velocity : it doesn t
What we experience is due to atoms exchanging messenger particles, the most familiar of which are photons :
That particles of light travel at the speed of light is a tautology but if the recipient is travelling at the speed of light
a message will never arrive : With out an exchange of particles, nothing happens : atomic clocks for instance, don t tick