The room moves

Spacetime Faster than the speed of light? Is there!

Cause: space-time

This brings the crucial term into the discussion: space-time. It offers an explanation of how it can be that two objects can move away from each other at the speed of light or faster than light, even though they hardly move themselves. "There is a comparison with a yeast dough with raisins: the raisins themselves rest within the dough, but the dough rises and this causes the raisins to move apart."

And this dough, which symbolizes space, does not count speed for it. It has no limit like any other particle, explains astrophysicist Bruno Leibundgut: "The bizarre thing about it is that space does not have to adhere to physical laws. This means that you can expand space, for example, faster than light."

Superluminal speed does not just mean a bit faster than the speed of light, but very, very much faster. In the past of the universe, this has also resulted in galaxies or areas in the universe moving thousands or billions of light-years apart within seconds without moving much themselves. Professor Martin Ammon from Jena describes what space is capable of using the theory of the first seconds of the universe, the so-called inflationary phase. "That was really a fraction of a second after the Big Bang. In this context, the universe has expanded from say 10-30 centimeters to today's size or even larger."

Nothing is faster than light

And despite this expansion of space, which also apparently moves the galaxy mentioned above at faster than light speed, all those who still claim that the speed of light is the fastest there is, says Hendrik Hildebrandt, are right.

But this is not a violation of this law of the theory of relativity that nothing can move faster than the speed of light. That means that this galaxy does not overtake us at the speed of light, it does not fly past us at the speed of light, but it is very far away from us and is in a different coordinate system. And we now define a quantity that we call the escape speed and then arrive at a result that is greater than the speed of light.

Hendrik Hildebrandt, Ruhr University Bochum

If we were to reverse our perspective and observe our Milky Way from this distant galaxy, then one would have the impression that we, too, were moving away at the speed of light. But if our galaxy, our solar system or our earth had a speedometer, it would never show the speed of light even remotely. What we register as the speed of escape is the expansion of space, not the speed of the celestial bodies.

Winner: Gravity

That means here with us, where gravity has the say, where it is greater than the enigmatic power of dark energy, which inflates or pushes the space apart, here the universe functions as we experience and experience it every day. But much further out, where there is only empty space for millions of light years, there is dark energy. We don't understand why yet, but it makes space expand, faster than any earthly imagination allows. And that's why there are celestial bodies that move away from us faster than the speed of light and that doesn't even contradict what we learned in physics class.