When I was in school, it seems a million years ago, I had a science teacher who insisted on the existence of the ‘ether’ affording structure to space. This in spite of Albert Einstein’s 1905 and 1915 proofs that it does not exist. Obviously that science teacher was completely out of date. Or was he?
The great J.J. Thompson, the British physicist, discoverer of the electron and Nobel Laureate, was a fabulous teacher who produced at least seven additional Nobel Laureates, including his own son. He believed that the ether existed to his dying day, which came in 1940. And now we have another problem: the universe appears to be expanding but as it expands its bits and pieces should be affected by the billions of other bits and pieces, each of which exerts gravity. The effect of all this gravity should be slowing down the movement of all this material including the at least 200,000 or more galaxies we have in our universe. In fact, the opposite appears to be happening: the bits and pieces in our universe are observed to be speeding up its expansion, in effect, flying apart. Oh, oh! There has to be an explanation. And that had our intrepid physicists scratching their heads.
There just had to be some sort of energy out there that we don’t know about causing all these galaxies to speed up their movement away from each other. Their best explanation for this expansion phenomenon was Dark Energy. Although Dark Energy is strictly hypothetical, many physicists are working to discover it and to characterize it. They hypothesize that Dark Energy is very thinly spread. For example, within the orbit of Pluto these scientists believe that in our solar system, there is only the equivalent of nine tons of Dark Energy (remember Einstein’s equation of 1905, e=mc2, where e stands for energy, m stands for mass, and c refers to the speed of light, which happens to be 186,000 miles per second and in this equation it is SQUARED, making a very very big number!) which means that it only takes a tiny bit of mass to make a lot of energy. Still that is not much energy spread around that enormous volume of space in our solar system. Though it is still very hypothetical, there are a very large number of physicists seriously scratching their heads in an effort to find direct evidence that it really exists. Dark Energy is still an enigma as is Dark Matter.
It makes you wonder how these physicists come up with ideas like Dark Energy or Dark Matter, for goodness sake. They do go to a lot of trouble to be sure that Dark Energy and Dark Matter do exist. For example, physicists, collaborating with astronomers, have examined 200,000 galaxies. That is a lot of galaxies when you think that our earth is a miniscule part of one of them – the Milky Way Galaxy. They got an enormous amount of data when they looked at all those galaxies. It was a lot of work getting information out of each and every one of those galaxies. When it came down to the bottom line, the conclusion was that about 5 percent was our kind of matter –ordinary matter, including everything in those galaxies, which we know contain multi- millions of stars, the vast majority of which are a lot bigger than our sun. Their calculations, once again, showed that there was about 25 percent Dark Matter (hypothetically, so far, mostly WIMPS) and 70 percent Dark Energy, spread thinly and evenly through all those 200,000 galaxies. Wow, what a lot of work to calculate the way the universe is endowed with the different kinds of energy and stuff. Well, hypothetically at least.
Way back in the early nineteen thirties, it was suggested that because of unexplained rather massive gravitational effects, there must be stuff out there in space besides the stuff that makes up us, the planets and all the stars and their (well over 200 thousand) galaxies (and there are galaxies with millions of stars!) This something else they called Dark Matter. We have never seen it but all sorts of theoretical physicists think they know what makes it matter: it is made up of particles that are all but impossible to detect and they are not negligible.
The main particle proposed to make up Dark Matter is called (believe it) a WIMP. That is a Weakly Interacting Massive Particle (‘massive’ simply meaning that it has mass – it doesn’t mean that it is particularly heavy) and there are supposed to be kagillions of them and it is proposed that millions of them pass unrestricted through the earth (and at least some through you) every day. Remember that atoms are almost entirely empty space, including the atoms making up you. So, even though these particles are characterized as ‘massive’, there is little there to stop them, so they just pass through you and the earth. Certainly, occasionally they have to hit an atomic nucleus, bouncing off or breaking up themselves and, or the nuclei they hit. This is exactly how our brilliant physicists plan to find them and study them. There is too much interference on the surface of the earth, so WIMP traps (or Dark Matter Detectors) are set up as deep below the surface of the earth as they can get, usually in deep abandoned mines. These WIMP traps are set up deep in quite a number of countries, including Italy, the US and Canada. They have found some breakdown particles but so far it is difficult to say exactly what the breakdown particles were before they broke down. So far the Italians have detected about 20 somethings, ricocheting into smaller particles and by measuring the energy released in the form of light flashes. Hopefully they will eventually find that they really are WIMPs and they will finally be able to say ‘they exist!
A very hard working and creative physicist has made a pretty good estimate of the mass of all the hypothetical Dark Matter in the Universe. And then he went on to estimate the number of hypothetical WIMPs in the universe and from that he estimated their accumulated mass. To his surprise and to the surprise of physicists generally the masses of these two, all the Dark Matter and all the WIMPS was almost exactly the same. That is now known to physicists as the WIMP MIRACLE! At present, it appears that the Dark Matter is made entirely of WIMPs (that is, if they really exist). And that is still a question in some physicists minds.
In Greece there are many prestigious universities, the very most prestigious of all those is Aristotle University in Thesallonica. In the physics department there is a prestigious physicist, who happens to be a woman, who does not accept the idea, either that our Universe is expanding or that there is any need to postulate such ideas as Dark Energy or Dark Matter. She considers all these observations to be illusions and therefore why bother to calculate all that stuff, which after all are hypothetical entities and the observations that these hypotheses are based on are pretty well all illusory. Even physicists have imaginations and she feels they probably used theirs to come to these hypothetical conclusions. Please remember the wonderful canals on Mars, they have proven to be illusions. Yet their existence was believed by the best of us for a very long time. Surely, Dark Energy, and Dark Matter (and all those wonderful WIMPs, millions of which are hypothesized to pass through the earth every day) are based on illusions. Say it is not so, lady physicist.
If the vast majority of physicists are right, we - ourselves, our planet, the solar system, our galaxy and all the other galaxies of the universe, only make up, at most, say 5 percent of the mass-energy density (just call it the total content) of our universe. And the rest? Well, estimates say that about 25 percent is Dark Matter and then about 70 percent is Dark Energy. Those figures do vary a little according to how they were calculated so there is a little leeway when it comes to the division between these three entities. I suppose that research is furiously continuing to discover the nature of Dark Matter and Dark Energy. But perhaps the observer is more correct who suggested that, like the maps of the 15th century, Dark Matter and Dark Energy should still be labeled ‘Terra Incognito’. If you are very daring and willing to risk the ire of thousands of physicists, you might say that J.J. and my teacher were right and we can just put them together and call them the ‘ether’.
