Deep space — galaxies “run away” faster than the theory provides for. Despite all the achievements of science, it still has quite a few blank spots. The magazine New Scientist has published a list of mysterious phenomena that scientists are unable to explain.
1. The placebo effect
Do not try this at home! For several days you cause someone pain several times a day. You reduce the pain with morphine, right up to the last day of the experiment, and then you replace the morphine with saline. And guess what happens? The saline relieves the pain.
This is the placebo effect: somehow a preparation made of nothing can have a very powerful effect. Doctors have known about the placebo effect for a long time. But apart from the fact that it apparently has a biochemical nature, we know nothing. One thing is clear: the mind can influence the body's biochemistry.
2. The horizon problem
Our Universe turns out to be inexplicably uniform. Look across space from one edge of the visible Universe to the other, and you will see that the cosmic microwave background has the same temperature throughout. This does not seem surprising until you remember that these two edges are 28 billion light years apart, while our Universe is only 14 billion years old.
Nothing can move at a speed exceeding the speed of light, so it is impossible for thermal radiation to have travelled between the two horizons and evened out the hot and cold zones formed during the Big Bang, establishing the thermal equilibrium that we see now.
From a scientific point of view, the uniform temperature of the background radiation is an anomaly. It could be explained by accepting that the speed of light is not constant. But even then we are still powerless before the question: why?
3. Ultra-high-energy cosmic rays
For more than ten years now, physicists in Japan have been observing cosmic rays that should not exist. Cosmic rays are particles that travel through the Universe at a speed close to the speed of light. Some cosmic rays arrive on Earth as a result of violent events, such as the explosion of a supernova. But we know nothing about the origin of the high-energy particles observed in nature. And even that is not the real mystery.
When cosmic-ray particles move through space, they lose energy in collisions with low-energy photons, for example from the cosmic microwave background radiation. However, researchers at the University of Tokyo detected cosmic rays of very high energy. In theory they could have come only from our own galaxy, but astronomers cannot find the source of these cosmic rays in our galaxy.
4. The phenomenon of homeopathy
Madeleine Ennis, a pharmacologist at Queen's University Belfast, is a real scourge of homeopathy. She opposed the claims of homeopaths that a chemical remedy can be diluted to the point where the sample contains practically nothing but water, and at the same time have healing power. Ennis resolved to prove once and for all that homeopathy is simply nonsense.
In her latest work she describes how her group, in four different laboratories, studied the effect of ultra-dilute solutions of histamine on the white blood cells involved in inflammation. To the scientists' surprise, it turned out that the homeopathic solutions (diluted to the point where they apparently did not contain even a single molecule of histamine) worked in the same way as histamine.
Before these experiments no homeopathic remedy had ever worked in clinical trials. But the Belfast study indicates that something is going on after all. “We,” says Ennis, “cannot explain our findings, and we report them to encourage others to investigate this phenomenon”.
If the results turn out to be real, she believes, the consequences could be very significant: we may have to rewrite physics and chemistry.
5. Dark matter
Take our best knowledge of gravity, apply it to the rotation of galaxies, and you will at once find a problem: according to our knowledge, galaxies should fall apart. Galactic matter revolves around a central point because its gravitational attraction creates centripetal forces. But there is not enough mass in galaxies to produce the rotation that is observed.
Vera Rubin, an astronomer at the Department of Terrestrial Magnetism of the Carnegie Institution in Washington, noticed this anomaly in the late seventies of the last century. The best answer that physicists could give was to suppose that there is more matter in the Universe than we can observe. The problem was that no one could explain what this “dark matter” is.
Scientists still cannot explain it, and this is an unpleasant gap in our understanding. Astronomical observations indicate that dark matter must make up about 90% of the mass of the Universe, and yet we are astonishingly ignorant of what these 90% are.
6. Life on Mars
20 July 1976. Gilbert Levin is sitting on the very edge of his chair. Millions of kilometres away from him, on Mars, the Viking lander has taken soil samples. Levin's apparatus has mixed them with a substance containing carbon-14. The scientists taking part in the experiment believe that if emissions of methane containing carbon-14 are detected in the soil, then there must be life on Mars.
The Viking analysers give a positive result. Something absorbs the nutrients, converts them, and then releases a gas containing carbon-14. But why is there no celebration?
Because another analyser, designed to detect organic molecules, which are a necessary sign of life, found nothing. The scientists played safe and declared the Viking findings false positives. But is that so?
Results transmitted from NASA's most recent spacecraft show that in the past the surface of Mars almost certainly contained water and was therefore favourable to life. There is other evidence as well. “Every flight to Mars,” says Gilbert Levin, “provides data that support my conclusion. Not one of them contradicts it”.
Levin no longer defends his views alone. Joe Miller, a microbiologist at the University of Southern California in Los Angeles, has analysed the data afresh and believes that the emissions show signs of a circadian cycle. And that suggests, with a high degree of probability, the presence of life. Whether these scientists are right is not yet known.
7. Tetraneutrons
Four years ago six particles were detected that should not have existed. They were called tetraneutrons — four neutrons held together in a bond that ignores the laws of physics.
A group of scientists from Caen led by Francisco Miguel Marquès fired beryllium nuclei at a small carbon target and analysed their trajectories with detectors. The scientists expected to see four different neutrons strike different detectors. Instead they found only one flash of light in one detector.
The energy of this flash showed that all four neutrons had struck the same detector. Perhaps it is just a coincidence, and four neutrons happened to hit the same place at the same time. But that is ridiculously unlikely.
At the same time, such behaviour is not unlikely for tetraneutrons. True, some may object that according to the standard model of particle physics tetraneutrons simply cannot exist. After all, by the Pauli principle, a single system cannot contain even two protons or two neutrons that would have identical quantum properties. The nuclear force holding them together is such that it cannot hold even two single neutrons, let alone four.
Marquès and his group were so stunned by the results that they “buried” the data in a scientific paper that spoke of some probability of the discovery of tetraneutrons in the future. After all, if one starts to change the laws of physics in order to account for a bond between four neutrons, chaos will ensue.
To recognise the existence of tetraneutrons would mean that the mix of elements formed after the Big Bang does not agree with what we now observe. And, what is worse, the elements formed become too heavy for the cosmos. “The Universe would probably have collapsed before it began to expand,” says Natalia Timofeyuk, a theorist at the University of Surrey in Guildford, Great Britain.
At the same time, there is other evidence in favour of matter being able to consist of many neutrons. These are neutron stars. They contain an enormous number of bound neutrons, and this means that when neutrons gather into masses, forces that are still unexplained to us come into play.
8. The Pioneer anomaly
In 1972 the Americans launched the spacecraft Pioneer-10. On board was a message to extraterrestrial civilisations — a plaque with images of a man, a woman and a diagram of the position of the Earth in space. A year later Pioneer-11 followed it. By now both craft should have been in deep space. However, in an unusual way their trajectories deviated greatly from the calculated ones.
Something began to pull (or push) them, as a result of which they began to move with an acceleration. It was tiny — less than a nanometre per second, which is equivalent to one ten-billionth of gravity at the surface of the Earth. But it proved enough to displace Pioneer-10 from its trajectory by 400 000 km.
NASA lost contact with Pioneer-11 in 1995, but until then it had deviated from its trajectory in exactly the same way as its predecessor. What caused this? Nobody knows.
Some of the possible explanations have already been rejected, including software errors, the solar wind and fuel leaks. If the cause was some gravitational effect, then we know nothing about it. Physicists are simply at a loss.
9. Dark energy
This is one of the best-known and most intractable problems in physics. In 1998 astronomers discovered that the Universe is expanding at an ever-increasing rate. Until then it was believed that after the Big Bang the expansion of the Universe was slowing down.
Scientists have still not found a reasonable explanation for this discovery. One suggestion is that some property of empty space is responsible for this phenomenon. Cosmologists called it dark energy. But all attempts to identify it have failed.
10. The tenth planet
If you set out on a journey to the very edge of the Solar System, into the cold zone of space beyond Pluto, you will see something strange. After passing the Kuiper belt — a region of space abounding in icy rocks, — you will suddenly see empty space.
Astronomers call this boundary the Kuiper cliff, because beyond it the density of the cosmic rocky belt falls sharply. What is the cause? The only answer can be the presence of a tenth planet in our Solar System. Moreover, to clear the space of debris in this way, it would have to be as massive as the Earth or Mars.
But although calculations show that such a body could have caused the existence of the Kuiper belt, nobody has ever seen this legendary tenth planet.
11. The WOW cosmic signal
It lasted 37 seconds and came from space. On 15 August 1977 on a printout of a radio telescope in the state of Delaware the pen recorders drew: WOW. And twenty-eight years later nobody knows what caused this signal.
The pulses came from the constellation of Sagittarius at a frequency of about 1420 MHz. Transmissions in this band are forbidden by international agreement. Natural sources of radiation, such as thermal emissions of planets, cover a much wider range of frequencies. What, then, was the cause of the radiation of these pulses? There is still no answer.
The nearest star to us in this direction is at a distance of 220 light years. If the signal came from there, then it must be either a huge astronomical event or an advanced extraterrestrial civilisation with a surprisingly powerful transmitter.
All subsequent observations of the same patch of sky led nowhere. No signal like WOW has been recorded since.
12. Such inconstant constants
In 1997 the astronomer John Webb and his group at the University of New South Wales in Sydney analysed light arriving on Earth from distant quasars. On its journey of 12 billion years the light passes through interstellar clouds consisting of metals such as iron, nickel and chromium. The researchers found that these atoms absorb photons of the quasar's light, but not at all those that were expected.
The only more or less reasonable explanation of this phenomenon is that the physical constant called the fine-structure constant, or alpha, has a different value when the light passes through the clouds.
But this is heresy! Alpha is an extremely important constant, determining how light interacts with matter, and it must not change! Its value depends, among other things, on the charge of the electron, the speed of light and Planck's constant. Is it possible that some of these parameters have really changed?!
None of the physicists wanted to believe that the measurements were correct. Webb and his group tried for many years to find errors in their results. But so far they have not succeeded.
Webb's results are not the only ones confirming that something is wrong in our understanding of alpha. A recent analysis of the only known natural nuclear reactor, which operated almost 2 billion years ago where Oklo in Gabon now stands, also suggests that something has changed in the interaction of light with matter.
The proportion of certain radioactive isotopes produced in such a reactor depends on alpha, and so an analysis of the fission products preserved in the soil of Oklo makes it possible to determine the value of the constant at the time they were formed.
Using this method, Steve Lamoreaux and his colleagues at the Los Alamos National Laboratory in New Mexico concluded that since the time of the Oklo reactor alpha has decreased by more than 4%. And this means that our ideas about the constants may turn out to be wrong.
13. Cold fusion
After an absence of sixteen years it has returned. Although, in fact, cold fusion never went away. Since 1989 US Navy laboratories have carried out more than 200 experiments intended to find out whether nuclear reactions at room temperature can generate more energy than they consume (this is thought to be possible only inside stars).
Controlled nuclear fusion would solve many of the world's energy problems. It is no surprise that the US Department of Energy is so interested in it. In December last year, after a lengthy review of all the evidence, it announced that it was open to proposals for new cold fusion experiments.
This is quite a sharp turn. Fifteen years ago the same department concluded that the initial cold fusion results, obtained by Martin Fleischmann and Stanley Pons of the University of Utah and solemnly presented at a press conference in 1989, could not be confirmed, and so were probably false.
The basic principle of cold fusion is that immersing palladium electrodes in heavy water (in which oxygen is combined with an isotope of heavy hydrogen) can release a large amount of energy. The catch is that all generally accepted scientific theories hold that nuclear fusion at room temperature is impossible.
Based on material from the magazine New Scientist