Science in Society Archive

Water Remembers? Homeopathy Explained?

New research suggests water remembers what has been dissolved in it, even after dilution beyond the point where no molecule of the original substances could remain. Dr. Mae-Wan Ho reports.

For more than a century, practitioners of homeopathy have used highly diluted solutions of medicinal substances to treat diseases. Some substances are diluted way beyond the point at which no trace of the original substances could remain. It is as though the water has retained memory of the departed molecules. This has aroused a great deal of scepticism within the conventional medical and scientific community. To this day, 'homeopathic' is used as a term of derision, to indicate something imagined that has no reality.

But a series of recent discoveries in the conventional scientific community is making people think again.

First, there were the South Korean chemists who discovered two years ago that molecules dissolved in water clump together as they get more diluted (see Molecules Clump on Dilution, SiS 15), which was totally unexpected; and further more, the size of the clumps depends on the history of dilution, making a mockery of the 'laws of chemistry'.

Now, physicist Louis Rey in Lausanne, Switzerland, has published a paper in the mainstream journal, Physica A, describing experiments that suggest water does have a memory of molecules that have been diluted away, as can be demonstrated by a relatively new physical technique that measures thermoluminescence.

In this technique, the material is 'activated' by irradiation at low temperature, with UV, X-rays, electron beams, or other high-energy sub-atomic particles. This causes electrons to come loose from the atoms and molecules, creating 'electron-hole pairs' that become separated and trapped at different energy levels.

Then, when the irradiated material is warmed up, it releases the absorbed energy and the trapped electrons and holes come together and recombine. This causes the release of a characteristic glow of light, peaking at different temperatures depending on the magnitude of the separation between electron and hole.

As a general rule, the phenomenon is observed in crystals with an ordered arrangement of atoms and molecules, but it is also seen in disordered materials such as glasses. In this mechanism, imperfections in the atomic/molecular lattice are considered to be the sites at which luminescence appears.

Rey decided to use the technique to investigate water, starting with heavy water or deuterium oxide that's been frozen into ice at a temperature of 77K. The absolute temperature scale (degree K, after Lord Kelvin) is used in science. (The zero degree K is equivalent to -273 C, and deuterium is an isotope of hydrogen which is twice as heavy as hydrogen).

As the ice warms up, a first peak of luminescence appears near 120K, and a second peak near 166 K. Heavy water gives a much stronger signal than water. In both cases, samples that were not irradiated gave no signals at all.

For both water and heavy water, the relative intensity of the thermoluminescence depends on the irradiation dose. There has been a suggestion that peak 2 comes from the hydrogen-bonded network within ice, whereas peak 1 comes from the individual molecules. This was confirmed by looking at a totally different material that is known to present strong hydrogen bonds, which showed a similar glow in the peak 2 region, but nothing in peak 1.

Rey then investigated what would happen when he dissolved some chemicals in the water and diluted it in steps of one hundred fold with vigorous stirring (as in the preparation of homeopathic remedies), until he reached a concentration of 10 to the power -30 g per centilitre, and compare that to the control that has not had any chemical dissolved in it and diluted in the same way.

The samples were frozen and activated with irradiation as usual.

Much to his surprise, when lithium chloride, LiCl, a chemical that would be expected to break hydrogen bonds between water molecules was added, and then diluted away, the thermoluminescent glow became reduced, but the reduction of peak 2 was greater relative to peak 1. Sodium chloride, NaCl, had the same effect albeit to a lesser degree.

It appears, therefore, that substances like LiCl and NaCl can modify the hydrogen-bonded network of water, and that this modification remains even when the molecules have been diluted away.

The fact that this 'memory' remains, in spite of, or because of vigorous stirring or shaking at successive dilutions, indicates that the 'memory' is by no means static, but depends on a dynamic process, perhaps a collective quantum excitation of water molecules that has a high degree of stability (see The strangeness of water and homeopathic memory, SiS 15).

Article first published 25/08/03


  1. Rey L. Thermoluminescence of ultra-high dilutions of lithium chloride and sodium chloride. Physica A 2003, 323, 67-74.

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