Thermometers
Temperatures and Ghost Hunting



Ghost Hunting Equipment: Thermometers
Temperatures and Ghost Hunting

Thermometers are an instrument that many ghost hunters use during an investigation. There are many types of thermometers out on the market to choose from.

They can be a great device to help check for cold spots which in theory is believed
to be caused from a ghost or spirit trying to manifest itself basically sucking in energy (heat) which in turns creates a cold spot.

Temperatures and Ghost Hunting

An infrared thermometer that measures surface temperatures is believed by ghost hunters to also measure air temperature, and thus to locate cold spots. A cold spot describes an area of localized coldness or a sudden decrease in ambient temperature that is allegedly connected to paranormal activity.

A thermometer (from the Greek (thermo) meaning "warm" and meter, "to measure") is a device that measures temperature or temperature gradient using a variety of different principles.

Various authors have credited the invention of the thermometer to Cornelius Drebbel, Robert Fludd, Galileo Galilei or Santorio Santorio. The thermometer was not a single invention, however, but a development. Philo of Byzantium and Hero of Alexandria knew of the principle that certain substances, notably air, expand and contract and described a demonstration in which a closed tube partially filled with air had its end in a container of water.

The expansion and contraction of the air caused the position of the water/air interface to move along the tube. Such a mechanism was later used to show the hotness and coldness of the air with a tube in which the water level is controlled by the expansion and contraction of the air.

These devices were developed by several European scientists in the 16th and 17th centuries, notably Galileo Galilei. As a result, devices were shown to produce this effect reliably, and the term thermoscope was adopted because it reflected the changes in sensible heat (the concept of temperature was yet to arise).

The difference between a thermoscope and a thermometer is that the latter has a scale. Though Galileo is often said to be the inventor of the thermometer, what he produced were thermoscopes. Galileo also discovered that objects (glass spheres filled with aqueous alcohol) of slightly different densities would rise and fall, which is nowadays the principle of the Galileo thermometer.

Today such thermometers are calibrated to a temperature scale. The first clear diagram of a thermoscope was published in 1617 by Giuseppe Biancani: the first showing a scale and thus constituting a thermometer was by Robert Fludd in 1638. This was a vertical tube, with a bulb at the top and the end immersed in water.

The water level in the tube is controlled by the expansion and contraction of the air, so it is what we would now call an air thermometer. The first person to put a scale on a thermoscope is variously said to be Francesco Sagredo or Santorio Santorio in about 1611 to 1613.

The word thermometer (in its French form) first appeared in 1624 in La Récréation Mathématique by J. Leurechon, who describes one with a scale of 8 degrees. The above instruments suffered from the disadvantage that they were also barometers, i.e. sensitive to air pressure.

In about 1654 Ferdinando II de' Medici, Grand Duke of Tuscany, made sealed tubes part filled with alcohol, with a bulb and stem, the first modern-style thermometer, depending on the expansion of a liquid, and independent of air pressure. Many other scientists experimented with various liquids and designs of thermometer.

However, each inventor and each thermometer was unique—there was no standard scale. In 1665 Christiaan Huygens suggested using the melting and boiling points of water as standards, and in 1694 Carlo Renaldini proposed using them as fixed points on a universal scale.

In 1701 Isaac Newton proposed a scale of 12 degrees between the melting point of ice and body temperature. Finally in 1724 Daniel Gabriel Fahrenheit produced a temperature scale which now (slightly adjusted) bears his name. He could do this because he manufactured thermometers, using mercury (which has a high coefficient of expansion) for the first time and the quality of his production could provide a finer scale and greater reproducibility, leading to its general adoption.

In 1742 Anders Celsius proposed a scale with zero at the boiling point and 100 degrees at the melting point of water, though the scale which now bears his name has them the other way around. In 1866 Sir Thomas Clifford Allbutt invented a clinical thermometer that produced a body temperature reading in five minutes as opposed to twenty.

A thermometer has two important elements:

  • The temperature sensor (e.g. the bulb on a mercury thermometer) in which some physical change occurs with temperature,
  • plus some means of converting this physical change into a value (e.g. the scale on a mercury thermometer).

Thermometers increasingly use electronic means to provide a digital display or input to a computer.


Cold Spots


In the terminology of ghost hunting, cold spot describes an area of localized coldness or a sudden decrease in ambient temperature that is allegedly connected to paranormal activity.


Ghost hunters may carry thermographic cameras and infrared thermometers (which can only detect surface temperatures, rather than ambient air temperatures) to detect and document the presence of possible cold spots in the ambient air of locations that are reported to be haunted.

However, more expensive infrared thermometers have ports for "K-Type" probes that do measure ambient air temperatures.

Ghost hunting organizations advise that the spots be checked from several different angles in order to confirm their existence and features.

Some ghost hunters warn against using cold spots as a paranormal indicator because cold spots can often be explained by natural temperature variances.

Skeptics also commonly dismiss them, saying that it is normal for buildings to experience temperature variations.



Mini Handheld Infrared Thermometer


Thermometers can be divided into two separate
groups according to the level of knowledge about the physical basis of the underlying thermodynamic laws and quantities.

For primary thermometers the measured property of matter is known so well that temperature can be calculated without any unknown quantities.

Examples of these are thermometers based on the equation of state of a gas, on the velocity of sound in a gas, on the thermal noise voltage or current of an electrical resistor, and on the angular anisotropy of gamma ray emission of certain radioactive nuclei in a magnetic field.

Primary thermometers are relatively complex.

Secondary thermometers are most widely used because of their convenience. Also, they are often much more sensitive than primary ones.

For secondary thermometers knowledge of the measured property is not sufficient to allow direct calculation of temperature.

They have to be calibrated against a primary thermometer at least at one temperature or at a number of fixed temperatures. Such fixed points, for example, triple points and superconducting transitions, occur reproducibly at the same temperature.

While an individual thermometer can measure degrees of hotness, the readings on two thermometers cannot be compared unless they conform to an agreed scale. There is today an absolute thermodynamic temperature scale. Internationally agreed temperature scales are designed to approximate this closely, based on fixed points and interpolating thermometers.