Wednesday, December 16, 2015

And Now For Something Completely Different: Brian Cox Gravity

You learned the theory in school, but you never really believed it, well I didn't anyway.

Until that was, Brian Cox came along with this demonstration of the Isaac Newtons.

And it still takes some believing, even as you witness it. 5mins


Martin Roberts said...

O.K. Let's get physical!

According to Einstein (I watched a TV programme about him only last night) the feathers and the ball should fall toward the ground on account of their following a deflection in the path of space/time, caused by the mass of the earth (I think that's how it goes).

I've always had a problem with that idea. Whenever I've seen it illustrated in a book, the curvature of space/time is pictured as a depression in the midst of a two-dimensional plane (associated with a sphere at the centre). But 'Space' is obviously not two-dimensional!

In addition, there is nothing by way of any atmosphere in outer space, hence no 'medium', as such, to carry sound etc. (Hollywood conveniently overlooks that little drawback for dramatic effect). So, I ask myself, what is there to bend? And why should a body of large mass bend it anyway?

Just by way of illustration, here on planet earth both air and water envelop solid objects completely. There is no gradual displacement leading to the surface of the object. If we proceed to imagine a much less fluid medium, ice or jelly say, with an aniseed ball in the middle, what might we see if the ball were removed, but without tampering with its surroundings? I would hazard a guess at a purely spherical void at the centre, where the ball used to be, but no other discontinuity of any kind, i.e. straight lines all the way round.

So then, if the space between two celestial objects is absolutely empty, then what is it that 'bends' if it isn't simply light itself? (being influenced directly by the solid bodies in its path and not sliding along some transparent super highway with a gradual fold in it)
Or, if some sort of mystical medium (called space for the sake of argument) exists, then why should it be prone to curvature around solid bodies when other flexible media we know of are not?

O.K. so I don't get Einstein, but can anyone straighten me out here, or is my thinking warped also?

Cheers all


Anonymous said...

Hi Martin,

I think it is one of those headf#*k questions! As I understand it (a big caveat btw!) the medium of curvature is "Spacetime" itself, as distinct from the "space and time" of the Euclidean model.

I'm trying to think of analogy! Perhaps Spacetime can be visualised as our immersive environment, as water is to the fish. The Euclidean model of events occurring "within" the passive dimensions of space and time is an approximation that works well at certain scales (those of everyday life) but not on the scales of the cosmos (nor atoms). At those scales we get to "see" the true continuum of our world; which we have come to know by those measurable effects that conform to consistent mathematical models.

The "stuff" of this continuum is what we know of it, and what our measurements/perceptions allow us to "see" of it. What else is water? That, to me, is the headfuck!

I'm probably way off the mark!

Kind regards,


Martin Roberts said...

Agnos @08:39

Hello there Agnos

Thank you for giving thought to my personal 'head scratching'.

"I'm probably way off the mark!" you say. Well you are seldom if ever that if I may say so.

"Perhaps Spacetime can be visualised as our immersive environment, as water is to the fish."

That's what I tried to do (it gets a bit weird when one thinks of air as an amorphous solid, atomically speaking, which it has to be in order to conduct electromagnetic radiation, including sound).

But that's where I come unstuck, since, all other things being equal, water (air) flows around solid objects in its path, but not until it reaches them. It doesn't 'make a left' (or right) in advance to avoid the obstruction.

To be honest, I have my doubts about 'time' per se. I suspect it to be an epiphenomenon. I'm losing confidence in the concept of matter also, and likewise sceptical about the multi-million dollar search for the Higgs boson, even though they claim to have found evidence for it (dirt on the lens? - lol).

Still e=mc2 alright, I'll give the old man that much.

Me I'm off to apply for admission to Ward 'H' (for headfucked).

Very best wishes

Martin R.

Martin Roberts said...


for 'an amorphous solid' (above) please read 'amorphous matter'


Anonymous said...

Martin @10.38,

It really is uncanny that you should say: I'm losing confidence in the concept of matter also.

I recently read this from Bruno Latour (contentious, but always interesting):

the reader must be prepared to stop considering this "matter" as a province of reality, but rather as an extremely bizarre institution, one that has had the unfortunate consequence, moreover, of creating, by contrast, a "knowing subject" and even a "mind" capable of extracting itself from "matter" by projecting an "external world""outside" itself.

Ward H it is!


Himself said...

You can't do physics by common sense. If you could, we wouldn't need physicists. - Dawkins

Just to lower the level of intellectual debate.

The basic question is I suppose, do the accepted laws of universal physics alter in the vacuum of space?

Not too convinced about Higgs-Boson myself Martin, but no matter what we may think about the experiment, it can't be denied, the apparatus is in itself a work of art.

Stunning photo-galleries.

Construction: What could possibly go wrong?

Repairs and more.

Anonymous said...

I am thrilled to bits with your lively discussion and would love to chip in with my tuppence as soon as I get a bit (space)time if you wouldn’t mind.


Himself said...

Well fancy that! And a new program to boot.

Inside Einstein's Mind: The Enigma of Space and Time

The story of the most elegant and powerful theory in science - Albert Einstein's general relativity.

When Einstein presented his formidable theory in November 1915, it turned our understanding of gravity, space and time completely on its head. Over the last 100 years, general relativity has enabled us to trace the origins of the universe to the Big Bang and to appreciate the enormous power of black holes.

To mark the 100th anniversary of general relativity, this film takes us inside the head of Einstein to witness how his idea evolved, giving new insights into the birth of a masterpiece that has become a cornerstone of modern science. This is not as daunting as it sounds - because Einstein liked to think in pictures. The film is a magical visual journey that begins in Einstein's young mind, follows the thought experiments that gave him stunning insights about the physical world, and ultimately reaches the extremes of modern physics.

Martin Roberts said...

Seen in a dentist's waiting room today - BBC Magazine featuring an article on Einstein and Relativity.

It contains the usual 2-D cartoon of space-time curvature plus a discussion of the question of 'ripples' that ought to be caused by celestial bodies in motion but are nigh on impossible to detect because space-time is so unbelievably hard!

Oh, purrleese.

"You can't do physics by common sense" - Dawkins

You can say that again, Richard.

Anonymous said...

It is remarkable how many of those great fin de si├Ęcle physicists were gripped by the analogy (if nothing more) with a certain type of mysticism/episteme.

Niels Bohr was given an award for which he was granted a coat of arms. He chose this design!

And Pauli cited his own greatest influences as: Schopenhauer (minus the determinism), Lao Tse and Bohr.

(Thinking rtgr here!)


Martin Roberts said...

Hi Agnos

I find it intriguing that solutions in Mathematics are most likely arrived at when the 'correct' form of representation is adopted. Likewise the understanding of (nuclear) Physics seems to me governed, at least in part, by an issue's being expressed within an appropriate (as opposed to misleading) metaphor; something Niels Bohr achieved.

I am neither Mathematician nor Physicist, but one of the finest books I have ever read is 'The Physicists' by C.P. Snow. I read it several times without tiring of either the subject or the prose.

Despite Richard Dawkins' amusing comment, Snow succeeds in communicating an understanding of profound issues at a level anyone with 'common sense' can understand.

Looking ahead I just hope the first manned mission to Mars doesn't get skittled by those ultra-hard deflections in space-time and before it arrives at the planet's surface!


Martin R.

Himself said...

C.P. Snow is it? I could do with a basin full of C.P. Snow, because I watched The Enigma of Space and Time last night and I can honestly say from the profundis of my heart, I'm not a bit wiser, not one iota.

Oh and Martin, the other fellow, my arse indeed.

I would have thought, given the accuracy of his recent predictions, that he would leave the soothsaying to others.

"If you think you understand quantum mechanics, you don't understand quantum mechanics." - Feynman

To say nothing of space-time.

Anonymous said...


Thanks so much for the recommendation, I've just grabbed myself a copy of Snow!

There is almost an air of pathos about some of these scientists, as though they struggle to come to terms with a landscape of their own making. Something known only too well in the arts!

Turing once said that his machines would endlessly "surprise" him.

Mechanism and writing are from our point of view almost synonymous. (A.T.)

Best wishes to all,