How Fast Are You Moving When You Are Standing Still?
A fundamental symmetry of nature.
Right now, you may be sitting in a chair, relaxed on the sofa or lying in the bed and claim to be still (according to signals coming from your vestibular system). However, unless you are lying exactly in one of the two earth poles, you would definitely be moving around the Earth center, with a maximum of 1670 km per hour if you are near the equator. For example, someone living in Italy like me, rotates at a speed of about 1300 km per hour: much faster than the cruise speed of common airliners (about 900 km per hour).
Moreover, together with the Earth, we are moving at a speed of 108,000 km per hour around the Sun, and together with the entire solar system, we are moving around the Milky Way, at the remarkable speed of 828,000 km per hour. But there is much more to it.
Together with our galaxy, the Milky Way, we move with respect to the (observable) primordial Universe at the incredible speed of 2 million km per hour!
This is the reference frame of the so-called Cosmic Microwave Background (CMB), the oldest picture of the Universe, dating back 13.5 billion years. At that time, the entire Universe was an incredibly uniform body (hydrogen plasma), at a temperature of 2726 degrees Celsius, with (quantum) perturbations in the order of only one part in 100,000.
The image of this article was made using the European Space Agency's Planck telescope and is an aitoff map of the radiation across the entire sky, highlighting these very small fluctuations with different colours.
It is amazing to know that, in a certain sense, we were among those infinitesimal perturbations... and that today, together with our galaxy, we move with respect to the primordial Universe at such a high speed (about 0.2% of light speed).
Yet it is impossible to realize this speed. So much so that to obtain these numbers we had to work really hard, collecting information from space, mainly in the form of light, that is, Photons. As an exception, the detection of the Earth's rotation can be also achieved through the Foucault Pendulum.
Well, the laws of nature do not appear to depend in any way on this motion.
Whatever reference system (coordinates) we use to define space and time (What is time? What is space?), the laws of nature are the same, no frame of reference is privileged. The invariance (of the laws of nature) under coordinate transformations is one of the key symmetries of Albert Einstein's theory of Relativity and it is known as General Covariance.
So, next time you say you are standing still, ask yourself, standing still with respect to what?
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