Which Theory Is For You

[nickbrookes1991]

Hiya all, just wanted to know all your thoughts on these two theories, any extra information that is relevant and how you see the earth.

The Theory of Relativity

Isaac Newton

Newton discovered his law of gravity more than 300 years ago this was called the universal law of gravitation. Newton then came up with his theory of general relativity, he believed that all the planets in the solar system where connected by the sun by a force of gravity, the suns gravity, he believed that the reason why earth was orbiting the sun was because that the suns gravity was pulling it in and that the earth was on a gravitational orbit around the sun. He then believed that if the sun died out then we would lose the orbit if the sun and slowly drift away.

We would keep on drift through space until we came in contact with another sun. He thought that gravity was a force that gets instantly across any distance so we would immediately feel the effects of the sun going out.

Then came Einstein

In 1905 when Albert Einstein was 26 years old he discovered that velocity of light is a cosmic speed limit. Speed that nothing in the universe could see.

Albert Einstein believed the meaning of gravity is warps and curves in the fabric of space and time cause by the presents of heavy objects.

Albert Einstein called this new picture of gravity General Relativity.

I just wanted to know any thought on these two theories and which one you think is the right one.

[brianb]

Neither. But General Relativity works fine for objects heavier than a gram and at distance scales greater than a millimetre. It's not a complete theory because it has no extension to the quantum world.

[Capricorn]

Both operate fine under their different conditions.

Why do we have to choose just one?

We drive cars mainly accepting the Newtonian side, but the GPS so many use in their cars has to have time corrections because of relativistic conditions. Gravity and velocity affect time.

So there is both operating side by side and in a very everyday application.

Accept both.

[brianb]

We drive cars mainly accepting the Newtonian side

For fairly light objects (heavier than a feather but lighter than a mountain) moving slowly (and even Thrust SSC at full chat is "slow" in this respect) Newtonian dynamics maps onto General Relativity within very tight limits. It's not that Newton was "right", it's just that the simplified mathematics is convenient.

[vhbelvadi]

Newton's affects us more directly in daily life, while the effects of Einstein's are not that easily apparent. And I don't mean useful, just 'apparent'. So I'd prefer something that connects them both, better--perhaps as a first step to quantum gravity or something?

But if you connect them like Capricorn did, it's a different story altogether.

[lulu57]

I go with Douglas Adams' general theory of relativity:

"the whole fabric of the space-time continuum is not merely curved, it is in fact totally bent."

Ergo, trying to get your head round it could prove deletorious to your mental health.

So don't try.

QED.

:)

[brianb]

Ergo, trying to get your head round it could prove deletorious to your mental health.

So don't try.

Unless you're a mathematician - in which case you understand multidimensional space-time perfectly well. Your mental health is already wrecked, so why worry.

[FraserClarke]

in which case you understand multidimensional space-time perfectly well.

String theorists are the worst;

String theorist: If you visualise this is in 15-dimensional space it is obvious.

Normal person: How do you 'visualise 15-dimensional space'!?!

String theorist: Well I just visualise an N-dimensional space and let N tend to 15...

(true story apparently)

[brianb]

My favourite mathematical joke:

Let ε < 0

(The joke here is that ε is invariably an infinitesimal but positive quantity ...)

[hunterknox]

I just wanted to know any thought on these two theories and which one you think is the right one.

Pretty sure that science doesn't work like that. You're thinking of talksport.

[ollypenrice]

Newton did not like the idea (implicit in his own theory) that an invisble force operating instantaneously at a distance connected the Earth to the Sun and said as much to Halley. It may be that he would have been pleased to see the issue resolved in the way Einstein did it; gravity in relativity does not need to be thought of as a force at all and the curvature of spacetime is already in place around the sun before the earth even gets there, so to speak.

Olly

[Capricorn]

Let ε < 0

From GCSE or O'Level any negative number satisfies that requirement.

Last time I looked an infinite number of them.

You've missed out the rest of the theorem.

[brianb]

Last time I looked an infinite number of them.

Uncountably infinite, in fact. I know, I counted 'em.

You've missed out the rest of the theorem.

Sorry, I never read it. I was too busy rolling about on the floor, laughing.

[Astorix]

I think that you can choose what ever one you want to believe and let that be it! although i have to say Lulu and her opinion is right! don't try and understand something that will boggle your mind that much! just enjoy what we know and can see!

[ollypenrice]

I think that you can choose what ever one you want to believe and let that be it! although i have to say Lulu and her opinion is right! don't try and understand something that will boggle your mind that much! just enjoy what we know and can see!

Oh no, no! Strain, struggle, speculate, read, observe, think and above all drink! That's the difference between us and stones or the dust that we will become...

Olly

[PeterW]

In this case Gen Rel is as good as it gets with pulsar and neutron star experiments testing it to stupid levels of precision. I just love the complexity in nature... there may be 'mechanical rules' to how things work, but put enough things together and beauty appears.... things you'd never expect from the maths....... you never need to look far to find things new to science.

Cheers

PEterW

PS The were Aleph null bottle of beer sitting on the wall and if bottle should accidentally fall.... there'd be Aleph null bottle of beer sitting on the wall!

[FraserClarke]

Don't 'believe' in GR?? Have a look at this plot;

File:PSR B1913+16 period shift graph.svg - Wikipedia, the free encyclopedia

These are measurements of the spin down rate of a binary pulsar. The red points are the measurements (the error bars are smaller than the plotted points). The blue line is the PREDICTION from general relativity, with no free parameters. It is NOT a fit to the data. The theory is consistent with the observations down to the 0.2% level, which is well within the errors you get from not knowing the precise dynamics of the whole galaxy.

The spin down is a result of energy radiated away from the Pulsar by gravitational waves. You cannot explain these results from Newtonian gravitation (gravitational waves simply don't exist in Newtonian mechanics)

[pvaz]

If you believe in Einstein you also believe in Newton, as Newton laws are part of Einstein theory when applied to velocities much smaller then light speed. Einstein perfected Newton's theory, which works well in our every day situations.

So both theories are right from my point of view, although they don't describe every case/situation in our universe.

General Relativity doesn't account for everything either, so there may come a Theory capable of unifying it all. It may not prove Einstein wrong, in fact he was trying to find it 'till he died, so he knew it was incomplete. It will probably only prove GR is a simplification that applies to just some cases, as GR did to Newton's Laws.

[FraserClarke]

Absolutely, I couldn't agree more. They both have regimes over which they are very very good models of the physical world. Newtonian properties come out of GR as you say, but the Newtonian theory of gravity is fundamentally different from GR in that it implies instantaneous action at a distance; which is wrong.

[pvaz]

I think now they seam fundamentally different, but they are very connected.

Einstein only reached General Relativity by applying Relativity to Newton's laws, while questioning how could the concept of instantaneous time be true if his Relativity theory proved time wasn't equal to all observers, only timespace is.

[ollypenrice]

In practical terms there is often nothing much to choose between Sir I and GR, as we know. Only if you are extremely dense or extremely fast does it make much difference!

And yes, Einstein owed Newton a vast debt, which he acknowledged.

However, I think that philosophically they are very, very different theories. Gravity stops being a force, time is found to be non-constant, as is space. The universe, or our view of it, underwent a radical change under GR and it seems a very mechanical approach, to me, to see the two theories as resembling each other. They may give very similar results, which is fine, but I once heard GR described as 'the intellectual frisson of the century' and I'd have to agree (though Quantum Theory makes you tingle as well...)

Olly

[FraserClarke]

In practical terms there is often nothing much to choose between Sir I and GR, as we know. Only if you are extremely dense or extremely fast does it make much difference!

Or if you want to use GPS. GR does have a few surprisingly useful practical aspects to it, and most people don't realise they rely on it most days. As you say though, in 99% of cases, there is no practical difference.

[ollypenrice]

Or if you want to use GPS. GR does have a few surprisingly useful practical aspects to it, and most people don't realise they rely on it most days. As you say though, in 99% of cases, there is no practical difference.

Yes, GPS is the classic example of an everyday application of GR though what I love about it is that it allows for such astonishing ideas as time not only varying but beginning, something no other theory of which I'm aware can do.

Olly

[George Jones]

Or if you want to use GPS. GR does have a few surprisingly useful practical aspects to it, and most people don't realise they rely on it most days. As you say though, in 99% of cases, there is no practical difference.

Yes, if general relativity is not taken into, systematic GPS errors accumulate at rates of something like twelve kilometres per day.

[totalamateur]

As an uninformed scientific nerd, I have a question.

The speed of light I understand is approximately 186,000 miles per second, which has apparently been scientifically tested and proven.

Is it a known fact that this speed is universal under any conditions?

ie; In annother gallaxy which has a far greater mass at it's core than our own milky way.