Black hole/time dilation question

[Gene Vincent]

Derek Smith said:

scorp said:

Why are some posters differentiating 'black hole' with 'black hole star' given that a black hole is gravity well that could only be naturally produced by the mass of something very large, like a star ?

Does it change name when there's more than on star 'in it'. These super massive black holes have cannabilised hundreds, perhaps thousands of stars so the name black hole start seems to lack gravitas.

Because this is the Science! section and it matters.

It matters because if we don't differentiate between a phenomena and the actual cause of that phenomena outlandish ideas take hold and can't be removed.

A Black Hole is a phenomena, it is an attribute of a Black Hole Star, it is not a 'thing' in and of itself.

The Star at the centre of a Black Hole is also not a singularity, this is self-evident... If it were a singularity, it would remain the same size no matter what was captured by it, but we know that they grow in size.

The term singularity is much misused, a singularity is something that can only 'exist' in retrospective time, there can be no singularity that exists in the direction of times arrow, time as the Cosmos experiences it.

In the entire history of time there has only been one singularity and that was at T=0, the beginning of time.

[Gene Vincent]

Bedazzled said:

Gene Vincent said:

The Star at the centre of a Black Hole is also not a singularity, this is self-evident... If it were a singularity, it would remain the same size no matter what was captured by it, but we know that they grow in size.

That's not correct, the event horizon increases in size as the black hole's mass increases, as predicted by GR, but we don't know what physically happens to the matter (or energy) inside the event horizon.

We know what happens mathematically, getting evidence is impossible though due to the event horizon being the limit of information. So the term 'know' is one of standard of proof, for example we 'knew' that a Higgs must exist 40 years ago, the maths were refined enough to be certain, but the extent of it was not, but even now despite Theoreticians like myself knowing this, empirical evidence is the standard to judge 'knowledge' by, so in an area that cannot ever provide empirical evidence we get a little stumped as to what is and what isn't 'evidence' sufficient to claim to know.

At present Theoreticians are not allowed to claim to 'know' anything, that Kudos is given to Empiricists who conduct the experiment that gives substance to the discovery...

For me, the Higgs was found sometime in the 60s, but I'm a theoretician, the Maths worked and it had to be there.

Now, returning to Black Holes and their Stars...

The maths tells us what is most likely to be going on in them, it is all that we will ever have to go on. So what does the maths tell us?

We know that such compressed matter usually ignites into a star, but we also know that as pressure rises the temperature for this to happen also rises and there is no limit to pressure or temperature and a Black Hole star is in a never ending race to ignite but each step up in temperature is accompanied by a rise in the pressure bearing down on it.

Despite pressure having no limit, compression of matter does.

So as the Black Hole Star consumes all it can grab, it grows both in mass and the maths tells us in size too, if the size of the star remained constant, then the maths tells us that there would be a breakdown in the Physics of the Cosmos a singularity would occur and the Black Hole Star would no longer be a Black Hole phenomena, but a 'Big Bang'.

A Big Bang is not the conventional physics of our present Cosmos and as such it would dissolve anything it its path, including any Black Hole and its Star.

The proof of their being no Singularity within a Black Hole Star is the fact that they are and remain what they are.

Empiricists have real problems with that, Theoreticians have no such qualms, we do the maths and it works.

The Science World is dominated by empiricists, but as yesterday proved, they can be a rather tardy companion.

So we can both be right, you on the Empiricist revetment and myself and a few friends who roam about on the landscape below, picking up things and lobbing them over the wall for you to either accept or refute.

An empiricist can rightly claim, 'no proof!' because there is no way (at present or in the foreseeable future) of getting information out of something that keeps itself so much to itself.

[Gene Vincent]

Derek Smith said:

Or 'twin' clocks. Put one in Concord and another in a 747 on a regular transatlantic route and the Concord one will, as one would expect, go faster.

Concorde may cross the Atlantic quicker, but it's atomic clock will go slower or record less time than one on the Jumbo.

The faster you travel, more of your existence is used up in the 3 dimensions of space and as a result less is available for travelling forward along times arrow.

[Mattygooner]

I like how science use really obvious names for things despite the science and "stuff" behind them being slightly mind blowing.

We have a Black hole, it really big, Super Massive infact = Super Massive Black hole

We have a Telescope, a large one at that, infact, its very Large = Verly Large Telescope

[ewenm]

Bedazzled said:

They should have called it the FLT.

That's the name of the next one...

[Mattygooner]

ewenm said:

That's the name of the next one...

Indeed, i do hope that their wives do not ask them if their bum looks big in this....

[Derek Smith]

Gene Vincent said:

Derek Smith said:

Or 'twin' clocks. Put one in Concord and another in a 747 on a regular transatlantic route and the Concord one will, as one would expect, go faster.

Concorde may cross the Atlantic quicker, but it's atomic clock will go slower or record less time than one on the Jumbo.

The faster you travel, more of your existence is used up in the 3 dimensions of space and as a result less is available for travelling forward along times arrow.

Sorry, it was a little joke of mine. Concord doesn't fly any more.

[Hooli]

Mattygooner said:

I like how science use really obvious names for things despite the science and "stuff" behind them being slightly mind blowing.

We have a Black hole, it really big, Super Massive infact = Super Massive Black hole

We have a Telescope, a large one at that, infact, its very Large = Verly Large Telescope

[Efbe]

Derek Smith said:

Bedazzled said:

Efbe said:

maybe it's just the way I have heard it explained, but to me, time dilation and length contraction of an observed object are relative only as they are seen. The object would see the same occurence, as relatively neither are moving; to each one the other is. so if both perform exactly the same movement inversely, then both will have moved the same amount meaning there will be no time difference. erge the time dilation never actually happened, and was just observed, not real.

Look up the twins' paradox, or I can walk you through it if you're interested.

Remember it's not just time and distance that are relative but also simultaneity, the twins have to meet up again in order to re-synchronise their clocks. Therefore one of them has to slow to a stop, turn around and return to the other, and this breaks the symmetry; the twin who experiences the deceleration and acceleration will have aged less than the other.

Or 'twin' clocks. Put one in Concord and another in a 747 on a regular transatlantic route and the Concord one will, as one would expect, go faster.

There's the effect of gravity. Put one down a well and put the other on top of Everest.

The clocks in satelites in 24-hour orbit for GPS have to take into account the difference in time between them and the ground.

umm, would it be really awkward to say that neither the concorde or the 747 are moving.
not to themselves anyhow. The concorde is still, everything else is moving for the concorde. The same for the 747. Thus I cannot see why either one would have any dilation placed upon it.
I also disagree with the theory that the S.O.L. is the fastest possible, it only aids observation, I don't think it defines location. without it defining location, the examples such as: http://galileoandeinstein.physics.virginia.edu/lec... don't seem to work for me.

However you mention simultaneity as being relative, I haven't read up on this before, can you explain? I have had a gander at the wiki explanation, which talks about the frame of reference. But I still feel that defining the frame of reference by the S.O.L. might be missing a trick?!?

edit: I think I do know about this, just didn't know the name of it! We are talking about the train carriage experiment with a light shining at a mirror on the roof and bouncing back down, but making a triangle.

unconvinced, but then again, I certainly don't work at CERN!

[Efbe]

Bedazzled said:

Einstein's inspiration was to take Maxwell's equations here at face value, in other words assuming the speed of light is constant was an input to the theory. There's experimental evidence to back it up, the most famous being the Michelson–Morley experiment here and Willem de Sitter's binary star measurement here.

Here's an example of why time dilation occurs on a rocket moving at relativistic speeds:



Imagine a beam of light moving between two mirrors in a rocket ship. To an astronaut in the rocket, the beam of light will just move up and down, whereas to an observer on Earth the light will follow a diagonal path because the rocket is also moving forwards. Therefore the light will have to travel further, and if the speed of the light is constant then the interval between each mirror will be longer; the clock runs slower.

Einstein also defined a second postulate, which basically says if two objects are moving in uniform motion relative to each other, it's impossible to tell which is moving.

Therefore if the astronaut was wearing a watch, it must also tick in synch with the light beam, otherwise he could use the two different measures to deduce that he was moving. So he would see his watch running normally while an observer on Earth would see it ticking slowly; and everything else in the rocket, including his own heart-beat, must do the same.

If the astronaut looked back at Earth he would see exactly the same effect on clocks here, due to symmetry, but if that symmetry breaks (such as the rocket accelerating), then you get all sorts of interesting effects.

thanks for that. I will look into the experiments later when I have more time.

The example you provide would work just the same if you fired a ball from the floow to the roof and it bounced back, not just for light.
Are there any examples/explanations to define time dilation without the use of light as the main focus? It would seem to me that if the speed of light is not the fastest anything can go at, then the explanations of time-dilation I have seen so far would not hold up.

[Gene Vincent]

Efbe said:

...It would seem to me that if the speed of light is not the fastest anything can go at, then the explanations of time-dilation I have seen so far would not hold up.

The corollary of that is...

If that is your stance then the inversion is that if the explanations of Relative Time do hold up, and they hold up perfectly, this means that the SoL is the fastest thing around.