What is OSETI?

OSETI is an acronym for Optical Search for Extraterrestrial Intelligence, which is a relatively new adaptation of the Radio SETI projects currently in progress. The primary difference between Optical SETI and Radio SETI is that Optical SETI searches for pulses of laser light in or near the visible portion of the light sprectrum, while Radio SETI searches for signals within the radio and microwave portions of the light spectrum.

For a more detailed look at OSETI, and for answers to such questions as "Is discovering extraterrestrial life likely to happen?", please read on or jump to any one of these sections:

Origins of SETI and OSETI

The original idea to search the skies for signals from intelligent life elsewhere in the universe came from Giuseppe Cocconi and Philip Morrison. Cocconi and Morrison published a paper in the journal Nature in 1959. The paper outlined the possibility of interstellar communication with MASERs operating in the 21 cm range based in the frequency of hydrogen oscillations, the only known astronomical microwave wavelength at the time.

Even though the invention of the LASER came only a year later, the first LASERs were low-powered devices compared to the much more highly evolved radio wave devices. This is the most likely reason that earlier searches for extraterrestrial intelligence were conducted in the radio portion of the light spectrum instead of the visible portion of the light spectrum.

Since then, LASER technology has improved dramatically, and there is now substantial evidence that interstellar communication may perhaps better be performed in the optical portion of the light spectrum. Consequently, several research institutions are initiating optical versions of the original SETI project.

Optical SETI versus Radio SETI

Several arguments exist for the choice to search for signals in the optical region of the electromagnetic spectrum over the radio portion. These reasons stem primarily from the benefits for another civilization to send a beacon or signal in the visible rather than in the microwave. Briefly, some of the reasons include:

  1. Visible light-emitting devices are smaller and lighter than microwave or radio-emitting devices.
  2. Visible light-emitting devices produce higher bandwidths and can consequently send information much faster.
  3. Interference from natural sources of microwaves is more common than from visible sources. (See the technical paper on OSETI for additional details.)
  4. Naturally occurring nanosecond pulses of light are mostly likely nonexistent.

Now in more detail: Most of the benefits of operating in the visible spectrum are the result of light having a smaller wavelength and higher frequency than microwave radiation. For instance, compared to the large antennae needed for radio wave emission, lasers are extremely small and light. In addition, due to the higher frequency of light waves (1.4 gigahertz versus 430 terahertz for hydrogen microwaves and red light), carrier signals with lasers can be much higher frequencies allowing extremely fast data transfer.

The second reason to prefer an optical signal to a radio one may be even more important. Unlike microwaves, where sudden signal spikes can come from things such as spark plugs, brief spikes or pulses of visible light are rare in the universe as we know it. Therefore if a laser pulse is detected, the probability is higher that it is actually from intelligent life and not from a natural astronomical event. In fact, nanosecond spikes of light are thought to be nonexistent in the universe.

Frequently Asked Questions

Technical Papers on OSETI

Links to Other OSETI Web Pages

Princeton OSETI · Latest News · Project History · Technical Terms · Fitz-Randolph Observatory

Please direct comments about these Web pages to oseti@Princeton.EDU