Which is faster, the universe or light?  Science leaves no room for doubt

This kind of information flows from time to time in the scientific world, which looks very good in headlines, subtitles or teasers in articles published in popular scientific journals and websites. It has to do with The continuous expansion of the universeThus constantly changing position and moving away from each other galaxies, planetary systems, asteroids and dust in space.

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In theory, galaxies can be considered to move at a certain speed – What exactly? Edwin Hubble, an American astronomer, noticed that galaxies are moving away from us (observers on Earth), and The farther away the group of stars and systems is, the greater its apparent speed. The scientist supported his discovery with calculations, the most important part of which was The so-called Hubble constant is about 70 (km/s)/Mpc [kilometry na sekundę na megaparsek].

A diagram showing Hubble's lawPhoto: Misroland/CCTV/Wikipedia

A diagram showing Hubble’s law

A megaparsec is one million parsecs, or a distance of about 3.26 million light-yearsIt is an unimaginably long distance. For example, the diameter of the Milky Way, the galaxy in which Earth is located, is 105.7 thousand light years. So how should we understand the 70 (km/s)/Mpc mentioned earlier? If we look at a galaxy a million parsecs away from us, the apparent speed at which it will be moving away from us will be Yes 70 km per second. Considering a galaxy two million parsecs away from us, this speed would actually increase to Yes 140 km per second.

So we can assume so If we look at a very distant galaxy, the speed at which it will be moving away from Earth will be greater than the speed of light. Size wouldn’t be an issue because the universe is huge — recent estimates put it at 92-93 billion light-years in diameter — and Taking Hubble’s calculations, the final distance can be easily calculated.

Just split The speed of light (300 thousand kilometers per second) using the Hubble constant to discover that the point at which the galaxy moves away from Earth reaches the limit calculated by Einstein, which is approximately 4.285 thousand. MPc, or 4.2 GPC (Gigaparsec). This is the so-called Hubble horizon – This means that all distant galaxies will move faster than the speed of light.

Edwin HubbleFoto: Smithsonian Institution / Smithsonian Institution / Science Photo Library / Orient News

Edwin Hubble

This all sounds very reasonable, and the calculations clearly show it Some galaxies that are very far from Earth will be moving faster than the speed at which light moves through a vacuum. Does this mean that the current laws of physics are wrong and that Einstein was wrong? If we look closely at the expansion of the universe, we will find that It’s more complicatedThe honor of the greatest scientists in history was not compromised.

Speed ​​has many names

This is a very apt analogy for how the universe expands Inflate a balloon covered with dots. The more air we inject, the more the dots on the rubber surface begin to “move away from each other.” If we look at two adjacent sites, we will see this As the balloon fills, the distance between the dots increases faster than it was initially. However, it is worth keeping in mind that the points themselves do not actually move – The space between them becomes larger.

And in the case of the expansion of the universe, it works in the same way – what we measure on Earth and know as the “speed of a moving galaxy” is not actually the movement of a group of systems and star systems, but the expansion of the space between them. Galaxies move with space, but they do not cross itAs do rockets and self-propelled spacecraft that penetrate a vacuum, or smaller objects attracted by the gravitational field of a large star or planet.

Spiral galaxy NGC 7496 captured by the Hubble Space TelescopeImage: ESA/Hubble and NASA/J. Lee/PHANGS-HST Team/Judy Schmidt

Spiral galaxy NGC 7496 captured by the Hubble Space Telescope

This means that Einstein’s theory about photons (particles of light) being the fastest things moving in a vacuum is still true No body with mass moving through space can exceed a speed of approximately 300 million meters per second. (299,792,458 meters per second to be exact).

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The speed of light and the speed of expansion of the universe

Speed ​​in the context of the expansion of the universe is not a very precise term, because – as mentioned earlier – The galaxies themselves don’t actually move. To be able to talk about measuring speed in the context of what we do on Earth, we divide the distance traveled by the time it took us to cover it. This is what we got Units associated with speedlike Ms [metr na sekundę], how many hours [kilometr na godzinę] whether km/sec [kilometr na sekundę].

Formula for velocity in uniform motion in a straight line.  V = speed;  s = road;  t = timeImage: Shafiat Computer

Formula for velocity in uniform motion in a straight line. V = speed; s = road; t = time

In the case of the expansion of the universe, the calculation of unity is as follows: We divide the distance traveled by the galaxy by the time it took, and divide the result obtained by the distance between the Earth and the object of interest, expressed in megaparsecs..

In this way, the unit that describes the expansion of the universe is the one mentioned earlier Kilometers per second per megaparsec, or (km/s)/megaparsec. As you might imagine, this has nothing to do with speed, but rather an indication of how the size of the universe is changing.

H = Hubble constantImage: Shafiat Computer

H = Hubble constant

The speed of light and the expansion rate of the universe are two separate issues

according to Betteridge’s law of addresses “You can answer ‘no’ to every title that ends with a question mark.” This principle was already known, but it began to be associated with it Iyanm petredjima British journalist, after publishing one of his columns since 2009 on the site technovia.co.uk he wrote:

Although the answer to the question posed in the title of our article is indeed “no,” The expansion of the universe is still not well understoodSo at first glance it may seem that it is increasing in size at a speed faster than the speed of light. Actually though Both issues are too different to be directly compared. Therefore, it is worth remembering that the motion of the galaxies that we measure is not their true speed, although the distance between them and the Earth is increasing.

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