Rainer Weiss

Designing the laser detector that caught gravitational waves

• In August 2017, LIGO and Virgo detected two colliding neutron stars. Some 70 observatories joined the observation, and telescopes saw newly made gold and platinum, helping explain where about half of all elements heavier than iron come from.^[12]
• By September 2025 the LIGO-Virgo-KAGRA network had recorded about 300 black hole mergers, some still awaiting confirmation, and LIGO was observing roughly one every three days.^[11]
• Before LIGO, his balloon-borne instruments showed in 1973 that the Big Bang's leftover microwave glow has the peak expected of heat radiation. He later chaired the science team of NASA's COBE satellite.^[3],[9]
• With his Nobel Prize money he set up the Barish-Weiss Fellowship to support student research in MIT's physics department.^[7]

Weiss's contribution is knowledge and a new kind of instrument, not a product, so we record no quantified claims. His 1972 design study became the blueprint for LIGO, which opened gravitational-wave astronomy: a way to study black holes and neutron stars through the shaking of space itself rather than through light. The field has since tested predictions of Einstein and Hawking, helped reveal where heavy elements such as gold are made, and catalogued hundreds of black hole mergers. Earlier, his balloon measurements and leadership of COBE's science team helped turn the Big Bang's afterglow into precise evidence about the early universe. LIGO's drive for precision also advanced lasers, mirror coatings and quantum measurement, but no credible figure links a dollar value or a count of lives to Weiss's own work, and inventing one would be dishonest. Much of his impact also lives on in people: the students he trained now lead both fields he helped found.

Fundamental scienceSpaceTechnologyEducation

No number is given here on purpose. Some contributions cannot be counted honestly, and we would rather describe them than invent a figure.

• Minor

  A costly gamble on uncertain science

  Science called LIGO the most costly project in the National Science Foundation's history. Physicists first asked for nearly $300 million, and the cost estimate later rose about 40 percent. Some astronomers considered it premature and a possible waste of money. Construction began in 1992, and no gravitational waves were seen until 2015.^{[4],[10],[13]}

• Minor

  Three prizewinners for the work of a thousand

  The Nobel Prize honored three founders and leaders, but LIGO's discoveries rested on about 1,000 people. Co-founder Ronald Drever died in March 2017, before the prize was announced. Weiss said he saw the award as a symbol of the many others who worked on LIGO.^{[5],[6],[7],[17]}

• 1932

  Persecution

  While his mother was pregnant, his Jewish, Communist father reported a Nazi doctor at the Berlin workers' hospital where he worked. A Nazi gang seized him and held him in a cellar. His mother's father, a judge, got him released, and he was pushed over the border to Czechoslovakia.^[2],[3],[9]

• 1933

  Persecution

  Months after his birth, the Nazi regime began more than 400 anti-Jewish decrees and regulations, including 1933 laws that curtailed Jewish doctors and lawyers. Berlin, where about 160,000 Jews lived in the mid-1920s, had the country's largest Jewish community.^[14],[15]

• 1938

  Exile

  After the September 1938 Munich agreement left Czechoslovakia open to Hitler, the family joined crowds seeking visas to any country that would accept Jews. Backed by the Stix family of St. Louis, they reached New York in January 1939, two months before Germany occupied Prague.^{[2],[3],[9],[16]}

• 1939

  Other

  As refugees in New York, his father struggled for years to requalify as a doctor (about four years in Weiss's Nobel autobiography, about eight in a 2000 interview), while his mother took store-counter and odd jobs. Weiss attended private school on a refugee-relief scholarship.^[2],[3],[9]

• 1974

  Other

  Vietnam-era limits on military research money cut off funding for his gravitational-wave prototype at MIT. Reviewers doubted the idea, and he spent years seeking new support.^[4],[8]

Weiss's father, the neurologist and later psychoanalyst Frederick Weiss, came from a well-off German Jewish family in Berlin with ties to the Rathenau family that founded the electrical company AEG. He was also a committed Communist. His mother, the actress Gertrude Loesner, came from a Protestant family of civil servants and lawyers on the Rhine near Koblenz. In a 2000 interview Weiss said simply that his father was Jewish and his mother was not. NobelPrize.org describes his father as of Jewish descent. Weiss wrote that in 1938 the family sought visas to any country that would take Jews. In the sources we found, he did not discuss Jewish religious practice or his own Jewish identity.^{[1],[2],[3],[9]}

1. September 29, 1932

   Born in Berlin to a Jewish neurologist father and an actress mother. That year his father is seized by a Nazi gang, then released and pushed over the border to Czechoslovakia; mother and baby follow.^{[1],[2],[3],[9]}

2. September 1938

   After the Munich agreement opens Czechoslovakia to Hitler, the family seeks visas to leave Europe.^[2],[3],[9]

3. January 1939

   Arrives in New York as a refugee, two months before German troops occupy Prague.^[2],[3],[9]

4. 1953

   Having failed his courses and left MIT as a student, becomes a technician in Jerrold Zacharias's atomic beam laboratory at MIT.^[3],[9]

5. 1962

   Earns his PhD from MIT, after completing his bachelor's degree in 1955.^[1],[7]

6. 1964

   Joins the MIT physics faculty and starts a research group in cosmology and gravitation.^[7]

7. 1966

   Asked to teach MIT's graduate course in general relativity; preparing a lecture, he devises a thought experiment to detect gravitational waves by timing light between free-floating masses.^[3],[4],[8]

8. 1972

   Sets out his design for a laser interferometer gravitational-wave detector in an MIT laboratory progress report, identifying its main noise sources and how to overcome them.^[4],[10]

9. 1973

   Balloon measurements with his student Dirk Muehlner reveal the thermal peak of the cosmic microwave background.^[9]

10. 1976

    Elected chair of the science working group for NASA's COBE satellite.^[3],[9]

11. 1984

    Caltech and MIT agree to design and build LIGO jointly, led by Weiss, Kip Thorne and Ronald Drever.^[10]

12. September 14, 2015

    LIGO's two detectors make the first direct detection of gravitational waves, from two merging black holes.^[5],[11]

13. October 3, 2017

    Awarded half of the Nobel Prize in Physics; the other half is shared by Barry Barish and Kip Thorne.^[1],[5]

14. August 25, 2025

    Dies in Cambridge, Massachusetts, at 92.^[1],[7]

1. 1.Rainer Weiss - Facts · NobelPrize.org (Nobel Prize Outreach)
2. 2.Interview with Rainer Weiss (oral history conducted by Shirley K. Cohen, 10 May 2000) · Caltech Archives, 2000
3. 3.Rainer Weiss - Biographical · NobelPrize.org (Nobel Prize Outreach), 2017
4. 4.LIGO and the Discovery of Gravitational Waves, I (Nobel Lecture, 8 December 2017) · NobelPrize.org (Nobel Prize Outreach), 2017
5. 5.Popular information: Cosmic chirps (The Nobel Prize in Physics 2017) · NobelPrize.org (Royal Swedish Academy of Sciences), 2017
6. 6.Rainer Weiss - Banquet speech · NobelPrize.org (Nobel Prize Outreach), 2017
7. 7.Professor Emeritus Rainer Weiss, influential physicist who forged new paths to understanding the universe, dies at 92 · MIT News, 2025
8. 8.Q&A: Rainer Weiss on LIGO's origins · MIT News, 2016
9. 9.Meet the college dropout who invented the gravitational wave detector (Adrian Cho; archived copy) · Science (AAAS), 2016
10. 10.A Brief History of LIGO (by Kip Thorne and Rai Weiss) · Caltech, 2016
11. 11.Ten Years Later, LIGO is a Black-Hole Hunting Machine · Caltech, 2025
12. 12.LIGO and Virgo make first detection of gravitational waves produced by colliding neutron stars · LIGO Laboratory (Caltech), 2017
13. 13.Got gravitational waves? Thank NSF's approach to building big facilities (Jeffrey Mervis; archived copy) · Science (AAAS), 2016
14. 14.Anti-Jewish Legislation in Prewar Germany · United States Holocaust Memorial Museum, Holocaust Encyclopedia
15. 15.Germany: Jewish Population in 1933 · United States Holocaust Memorial Museum, Holocaust Encyclopedia
16. 16.Czechoslovakia · United States Holocaust Memorial Museum, Holocaust Encyclopedia
17. 17.Caltech Mourns the Passing of LIGO Co-founder Ronald W. P. Drever · Caltech, 2017