Physics Question

chapeau · 4 Sep 2012

peaps2 said:
Why dont you show us the math..?

He won't be able to do that maths.

1) He wouldn't know where to start. His limit of maths is knowing that when he goes to the bar to order two pints of lager and a packet of crisps he has to pay for three items.

2) The string being in tension is what is keeping the ball from flying off. When the string is cut, the string right next to the ball remains in tension until the 'wave' from the cut end reaches that point. The wave takes time to move down the string and is not instantaneous. So the maths would prove him wrong.

I'm guessing the maths would require some integral calculus and I'm also guessing the ball would not fly off at a tangent, more of a parabola until all external forces on the ball resolved to zero.

mysteryman · 4 Sep 2012

You don't need to guess; it would go off at a tangent.

chapeau · 4 Sep 2012

mysteryman said:
You don't need to guess; it would go off at a tangent.

That would require the force applied by the string to go to zero instantly. I just don't reckon it would work that way, the string would have elastic properties.

Astartes · 4 Sep 2012

Gravity would remain for the same time as the light would. That is the answer. Done.

doitall · 4 Sep 2012

If the Sun disappeared, you'd maybe have a few hours to kiss you ass goodbye, where this lump of rock you're stood on goes is the least of your worries.

Anyway the world ends in a few short months, and Clandown will be league Champions for all eternity

Crickleymal · 4 Sep 2012

chapeau said:
mysteryman said:

You don't need to guess; it would go off at a tangent.

Click to expand...

That would require the force applied by the string to go to zero instantly. I just don't reckon it would work that way, the string would have elastic properties.

Probably, although the difference would be so small as to be practically negligible. That's the engineering solution

EddieM · 4 Sep 2012

there would be no force applied, therefore the ball or earth would go off at a tangent (well according to non quantum applied maths) it would only travel about 9500 miles before the lights went out though.

UriBentMySpoon · 4 Sep 2012

[quote="joe-90";p="2501180
Now let me make this easier for you to comprehend.:

Get a fishing weight/plumb-bob/nut or bolt and fasten it to a piece of string/fishing line.

Spin it around over your head like a helicopter.
Now if you cut that line anywhere along its length the the effect to the weight at the end is instantaneous and it flies off at a tangent. Same with the Earth/Sun.[/quote]

For the sake of the argument. Gravity is pulling the Earth towards the Sun, in you example the weight is trying to get away. Wouldn't that alter your argument?

This is all in the spirit of fun and enquiry so lets keep it light.

sooey · 4 Sep 2012

For the sake of the argument. Gravity is pulling the Earth towards the Sun, in you example the weight is trying to get away. Wouldn't that alter your argument?

The weight is trying to follow a straight line in whatever direction it's heading. So is the Earth.

UriBentMySpoon · 4 Sep 2012

http://scienceblogs.com/startswithabang/2010/08/25/what-is-the-speed-of-gravity/

Something intense, like two neutron stars orbiting each other extremely close together! Occasionally, we get very lucky, and a neutron star emits very regular blips of light, pulsing with incredible precision: this makes it a pulsar! If one of these neutron stars is a pulsar aimed at us, we can test whether gravity moves at the speed of light or not!

Incredibly enough, we’ve discovered multiple independent binary pulsars with this exact configuration!

Not only is the gravitational source (star #1) moving, but the other object (star #2) is changing its velocity, as it changes its direction in orbit around the gravitational source! Remarkably, this effect causes the orbit to ever-so-slowly decay, which leads to time changes in the pulses!

The predictions from Einstein’s theory of gravity are incredibly sensitive to the speed of light, so much so that even from the first binary pulsar system, PSR 1913+16 (or the Hulse-Taylor binary), we have constrained the speed of gravity to be equal to the speed of light with an error of less than 1%!

calorific · 4 Sep 2012

Astartes said:
Gravity would remain for the same time as the light would. That is the answer. Done.

I disagree. Quite apart from anything else, the concept of "time" itself comes into question. If the question assumes that there is zero "time" within the transition of the state of the sun's existence to non existence, then there is no sudden implosion of space which would require a volume to be replaced with "space". On the whole, as time seems closely interlinked with movement then it follows that if there is zero displacement of gravity (in particular that associated with the mass of the sun) then there is zero time in it's non-existence. Hence zero delay.

joe-90 · 4 Sep 2012

chapeau said:
peaps2 said:

Why dont you show us the math..?

Click to expand...

He won't be able to do that maths.

1) He wouldn't know where to start. His limit of maths is knowing that when he goes to the bar to order two pints of lager and a packet of crisps he has to pay for three items.

2) The string being in tension is what is keeping the ball from flying off. When the string is cut, the string right next to the ball remains in tension until the 'wave' from the cut end reaches that point. The wave takes time to move down the string and is not instantaneous. So the maths would prove him wrong.

I'm guessing the maths would require some integral calculus and I'm also guessing the ball would not fly off at a tangent, more of a parabola until all external forces on the ball resolved to zero.

You say I can't do the maths yet you can't either? Worra tossa.

joe-90 · 4 Sep 2012

If the sun were to disappear then the as the largest body, the earth would control the gravity. Just like the letting go of the string in the example I gave you. The earth would go away from the sun which has now gone, and gravity would follow like that piece of string.

If you think I'm wrong - then what would happen to the gravity if both the earth and sun were to disappear at the same instant?

joinerjohn · 4 Sep 2012

What would make the sun disappear in an instant anyway ? Something out of bloody StarTrek or Stargate SG1 ought to do it.

PS Joe, the second largest body in our solar system is Jupiter, not the Earth.

joe-90 · 4 Sep 2012

Not in regard to the sun/earth as per the question.

Physics Question

mysteryman

EddieM

calorific

joinerjohn

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