question about gravity?

Question

if an object was orbiting around a star and the star suddenly dissapered would the planet instantly start moving tangent to its orbit or would it continue to orbit until the light from the star reached the planet. i guess what im asking is does gravity travel in waves at a constant speed like light or does it take instantanious effect? and if it takes an instantanious effect then wouldnt it be possible that gravity is pulling on us from objects that we cant see because they are too far away to see?

Answer 1

Believe it or not, the most currently accepted option is that it would take off at a tangent when light from that star stopped reaching it. Gravity waves have been claimed to have been measured. I've seen that very question in here before. Keep checking back on that one to see how the idea plays out over time with astronomers. Quantum physics demonstrates that information can be transferred at a rate greater than the speed of light (under unusual and so far useless circumstances), but our current understanding is that the deformation of the space-time continuum by gravitational sources is bound by the speed of light.

Answer 2

great questions. Half of all stars in the sky are members of binary systems! A binary star system consists of two stars which orbit around a common point, called the center of mass following Kepler's Laws. First off, a star doesn't tend to suddenly disappear... however, in the case of a star collapsing upon its own mass, and forming what we call a neutron star, the companion star would continue its same orbit around the common center. the reason is, that you cannot destroy matter, so even though a star may burn out, it's gravitational pull doesn't disappear. Binary stars can also trade-off matter from one to another. Crazy! A black hole (which is often formed from a neutron star) does not reflect any light, so we cannot see them, yet they are very much there and very much exerting gravitational influence on object around them. Companion stars stay companions even if one of them "burns out". Ok, now to your question about gravity travelling in waves. There are four basic forces in the universe, and these forces can generate waves. The four basic forces are the Electromagnetic force, the force of Gravity, the Strong Nuclear force , and the Weak Nuclear force. Gravity waves were predicted by Albert Einstein in the early 1900s. However, they are so weak that scientists have not yet been able to detect gravity waves. Gravity is an always-attractive force that acts between particles of matter. (It can also act between quantities of energy!) More technically, it has an infinite range through space, and weakens as the inverse-square of the distance between bodies. All theoretical and observational studies are completely consistent with the idea that it travels no faster than the speed of light - and no slower. Because all indications are that gravity travels at the speed of light, we can only be affected by where a body is at the SAME time we see the light from it. The light travel time from the Sun to the Earth is 8.5 minutes. When we look at the Sun NOW, we are seeing it where it was 8.5 minutes ago. It is also the position of the Sun NOW that determines the strength of the gravitational field that the Earth is feeling NOW. Where the sun actually is NOW has no affect upon us because this information is coded in the gravitational field which Earth will experience 8.5 minutes from now. This is why astronomers do not care where distant objects in the universe are RIGHT NOW. We only care where their light tells us they are NOW because it is this information that controls its affect upon the Earth and Sun.
Hope this helps. :-)

Answer 3

I'm not sure if it's been proven yet, but I believe it is fairly safely assumed that gravity obeys the speed-of-light limitation. So I guess the object orbiting would continue orbiting however many light-minutes or light-hours away it was. Then it would assume a straight-line trajectory, assuming no other massive objects in its vicinity.

I think this is the basis of experiments currently being done that are attempting to catch a nearby supernova in the act of blowing up for the purpose of detecting gravity waves. When a star goes nova, a large amount of its matter is rapidly converted to energy, thus losing a significant portion of its gravity. It is expected that both the flash of light and the change in gravity will arrive on
earth at about the same time.

Answer 4

Three years ago a research group published their results that they said showed the speed of gravity to be the same as light. (..see http://www.newscientist.com/article.ns?id=dn3232) Since then, though, a number of physicists have challenged that result. Bottom line is that the speed of gravity has NOT yet been conclusively determined nor, as someone told you, have gravity waves been detected.

So, if the star you mentioned disappeared how long the planets orbiting it would "notice" can't be answered at this time.

Answer 5

Most likely, the planet would immediately begin moving tangent to it's orbit. Gravity is an instantaneous effect, that's why when you jump off a bridge, you immediately fall.

However, the amount of time it would take for this in universal terms is not known... it may take days or even weeks for the planet to finally drift out of its established orbit. But it would begin the process immediately.

As for gravity pulling on us from objects that we can't see because they are too far away, we don't know for certain. It's theoretically possible, but if we can't see it, we won't know. It is assumed that there is a massive black hole at the center of our galaxy, and that black hole supposedly affects us because the galaxy spins. Technically, we can't see it, so that might fall into your category. But as for something that's too far away to see, it's anyone's best guess.

Hope this helps.

Answer 6

Gravity is still mostly unexplained, but it is believed that is moves in waves, by intermediate exchnage of particles called gravitons. This means that there would be a minimum time of light speed time for the effect to be noticed. But this is obvious, as information cannot travel faster than light, so the absence of the star would not be known before light could transmit the information.

Hope this helps. Merry Christmas

Answer 7

The speed of gravitatinal waves is currently one big ? in physics.
Take a look at the reference for a good overview on the subject, or just google 'gravitational wave'........
Remember that stars (or anything else) don't just 'disappear' without releasing a tremendous energy. That energy would clearly affect the object more than the sudden loss of mass of the star....

Answer 8

What make planets revolute is centripetal force of gravity. If the star vanished the planet probably would start floating in space.