How can space be warped

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Enter e-mail address This e-mail address will be used to create your account. Reset your password. Kornmesser artist concept. Take a moment to observe the effects of gravity. Lift your arm and feel how you are compelled to drop it again. Or is it? But we had no idea how it worked until Einstein stepped in, painting a strange and unintuitive picture. Newton published one of the most celebrated works of science, the Principia , in In it, he described that the force that pulls objects towards the ground is the very same force that underlies the motion of the planets and stars.

To come to this conclusion, Newton imagined taking an object far from the surface of Earth, and throwing it. If you throw it with too little momentum, it will fall towards Earth, captured by gravity like we are ourselves.

If you throw it with too much momentum, it will speed away from the planet, beginning its journey into the reaches of space. But with exactly the right momentum, you can throw it so that it falls continuously around Earth, around and around in an eternal tug-of-war. The object tries to continue in the path you threw it, but gravity keeps on pulling it back in.

With the right balance, the object is now in orbit around Earth—just like the moon, or like Earth around the sun. Newton formulated this insight into a mathematical equation, known today as the law of universal gravitation. We acknowledge Newton not just because of his idea, but because he formulated that idea into an equation that made predictions with greater accuracy than ever before.

Newton was well aware of this when he said,. Enter Albert Einstein—a man who was to change the world in so many ways. In , even before Newton published his now-famous work, Galileo Galilei wrote about the relative motion of objects familiar in his time: ships.

If you are in a closed room on a ship sailing at a constant speed and the ride is perfectly smooth, objects behave as they would on land. Almost years after Galileo, Einstein pondered the consequences of relativity in the context of an important factor: the speed of light. At first, special relativity may not seem to have much to do with gravity, but it was an essential stepping stone for Einstein for understanding gravity.

No matter how fast you try and catch up, light always appears to zip away from you at almost ,, metres per second. Why is this important? Interactive Imagining a light clock in slow motion.

For your friend, the clock seems to be working normally—the particles of light travel up and down, as expected, and time proceeds in its usual fashion. But from your perspective, watching the ship pass by, the light is moving both up and down and to the side, with the ship. The light travels a longer distance with each tick. This time warping due to speed and gravity shows up in our daily lives every time we use GPS on our phones to find our location.

They also run a different speed depending on the motion of the satellite. Of course, massive objects warping time isn't exactly the kind of time travel that science fiction authors love to write about. So, are there other ways of warping time? Well, possibly, but it's not likely. But there are a few options. Unlikely option number one is a wormhole, a theoretical bridge that matter and light could pass through and that's created from the curving of space. While some theories predict these existed at microscopic levels in the early universe, they also found that these wormholes were likely unstable and would have collapsed quickly.

In order for a wormhole to actually work for time travel, there would need to be some kind of exotic matter. Using a technique called the calculus of variations, you can prove the shortest path between two points is a straight line, which may not sound very impressive but bear with me.

In special relativity the equivalent "invariant" quantity also depends on time differences, so we have to think in terms of spacetime instead of space.

However, neither the usual spatial length nor time periods is in general invariant. That's why relative motion can cause length contraction or time dilation. The shortest path or "geodesic" is now motion at fixed velocity, which according to Newton's first law is what happens when no force acts on you.

So in relativity we obtain a geodesic path in the absence of forces. For example, near one big mass we have this approximation. Gravity is not considered a force in general relativity, so gravitational orbits are effectively just a generalisation of moving in a straight line at constant speed.

Is space "something" or "nothing"? It doesn't matter: the matter distribution determines the shape of geodesics. Who said that? Einstein didn't. Einstein said space was neither homogeneous nor isotropic where a gravitational field was. He said this :. He said space isn't nothing. It's a thing, not a nothing, something that is conditioned by energy in the guise of a massive star, this effect diminishing with distance. It isn't warped, it's rendered homogeneous.

And it isn't nothing, it's something. See this Einstein article from where he talks about a field as a state of space:. It can, however, scarcely be imagined that empty space has conditions or states of two essentially different kinds, and it is natural to suspect that this only appears to be so because the structure of the physical continuum is not completely described by the Riemannian metric".

A gravitational field is one state of space, an electromagnetic field is another. Also note the Robert B. Laughlin quote here :.

About the time relativity was becoming accepted, studies of radioactivity began showing that the empty vacuum of space had spectroscopic structure similar to that of ordinary quantum solids and fluids Subsequent studies with large particle accelerators have now led us to understand that space is more like a piece of window glass than ideal Newtonian emptiness Sign up to join this community.