LIGO Hanford is one of two Laser Interferometer Gravitational-Wave Observatories that detected the first direct gravitational-wave signal — a pair of merging black holes — in September 2015. The site sits on the Hanford Reach in eastern Washington and runs a free public Exploratorium-style visitor center on the second Saturday of most months.
The podcast episode below is our detour: how a four-kilometer L-shaped interferometer turns a passing wave from a billion light-years away into a measurement smaller than the diameter of a proton — and what the kids made of standing at the corner of the L.
I
About the observatory
- Area
- Observatory site only, inside the federal Hanford reservation. The instrument footprint is two perpendicular 4-kilometer arms in an L.
- Elevation
- 120–150 m
- Designation
- LIGO Hanford Observatory (NSF-funded, Caltech/MIT operated)
- Designation
- Inside the federal Hanford reservation (Department of Energy)
II
Visiting
Seasons
Spring
- Public tours run second Saturdays from March through June. LExC visitor center open Tuesday through Friday, 9:30 a.m. to 4:00 p.m.
- Eastern Washington spring runs cool to warm and dry. April and May are the best weeks to combine LIGO with Hanford Reach wildflowers.
- Register on Eventbrite for the second-Saturday observatory tour. The walking distance is under one mile on a fully ADA route.
Summer
- LExC drop-in is open Tuesday through Friday. Public tours are paused June through August because daytime heat regularly clears 100 degrees on the Hanford plateau.
- 100 degrees and dry is the rule, not the exception. Bring water; there is no on-site food or coffee.
- Plan an LExC visit before noon, then drive 15 minutes south to Richland for lunch.
Fall
- Public tours resume on second Saturdays from September through November. The LExC stays open Tuesday through Friday.
- Crisp, dry, and the most comfortable months on the Hanford Reach.
- Pair LIGO with a Hanford Reach Columbia River drive and a B Reactor tour if NPS slots are open.
Winter
- LExC drop-in continues Tuesday through Friday. No public observatory tours in December, January, or February.
- Dry cold, occasional snow on the plateau. The road in stays clear most days.
- LExC alone is worth the stop in winter. The Weber bar, the wave-machine demo, and the gravity-floor demo are all indoors.
With kids
No Junior Ranger booklet here. LIGO Hanford is not an NPS unit. The LExC exhibit floor is hands-on; the second-Saturday tour talks are pitched at ages 12 and up, and younger kids are welcome to walk the route with the family.
- LExC opens Tuesday through Friday at 9:30 a.m. The first hour is the quietest with elementary-age kids.
- Hands-on exhibits include a wave-machine, a gravity-floor demo, a Joseph Weber bar from the 1960s on display, and a replica of Rainer Weiss's 2017 Nobel medal.
- The second-Saturday public tour is free but requires Eventbrite registration. Arrive 15 minutes early.
- Tour talks are aimed at 12 and up but the route is family-paced. Big can follow the physics; Little can follow the exhibits.
- Kids cannot enter the actual vacuum tubes or the vertex building. The tour walks the perimeter and the public-facing rooms.
- No on-site food. Pack water and snacks; the closest restaurants are in Richland, 15 minutes south.
Accessibility
Paved parking at LExC. The second-Saturday tour route is fully ADA accessible. The walking distance is under one mile and can be skipped in favor of an LExC drop-in if mobility is a constraint.
- Paved lot at LExC; accessible entry to the visitor center.
- Tour route is wheelchair accessible end to end.
- An LExC drop-in alone (Tuesday to Friday) is a complete visit for anyone who wants to skip the perimeter walk.
Things you can't miss
Natural places
LIGO Exploration Center (LExC) and the second-Saturday observatory tour↗
The visitor center is open Tuesday through Friday, 9:30 a.m. to 4:00 p.m., free, drop-in. The hands-on floor has a wave-machine demo, a gravity-floor demo, a replica of Rainer Weiss's 2017 Nobel medal, and the historic 1960s Joseph Weber bar on display. The free second-Saturday tour runs September through November and March through June; registration on Eventbrite, arrive 15 minutes early, walking distance under one mile on a fully ADA route. The talks are pitched at ages 12 and up; Little can follow the exhibits and Big can follow the physics.
Hanford Reach National Monument (the landscape around LIGO)↗
The observatory sits on the southern edge of the Wahluke Slope shrub-steppe, inside the Hanford Reach National Monument the US Fish and Wildlife Service manages. The monument protects the last non-tidal, free-flowing stretch of the Columbia River in the United States. Designated June 9, 2000, by Presidential Proclamation 7319. Roughly 195,000 acres total; about 57,000 acres are publicly accessible. The reach is part of the ancestral fishing and gathering landscape of the Wanapum and the four Columbia Plateau treaty tribes, with use dating back at least 10,000 years per the USFWS Comprehensive Conservation Plan.
Common questions
- What is a gravitational wave?
- A ripple in spacetime produced by accelerating masses, predicted by Einstein in 1916. Two black holes spiraling into each other stretch and squeeze the space between LIGO's mirrors by a fraction of a proton's width as the wave passes through.
- Why does the detector have to be 4 km long?
- The wave's distortion is proportional to length. A 4-kilometer arm gives enough absolute stretch to measure, even though the relative stretch is one part in 10 to the 21. LIGO can detect a change in the arm length equal to one ten-thousandth the width of a proton.
- What did the first detection sound like?
- When LIGO converts the September 14, 2015 signal into audio, the last 0.2 seconds before the black holes merge slide up in pitch from about 35 Hz to 250 Hz: a rising whoop the team calls the chirp. It is the sound of two 30-solar-mass black holes ending 1.3 billion years of orbit.
- Who funded LIGO?
- The US National Science Foundation. By 1994 LIGO was the largest single project NSF had ever funded. Total NSF investment across construction, the Advanced LIGO upgrade, and operations has run to roughly 1.1 to 1.4 billion dollars.
- Can you actually see anything when you visit?
- From the public-tour route: the outsides of both 4-kilometer arms (low concrete buildings stretching to the horizon), the control room with operators on shift, and the LExC exhibit floor including the historic 1960s Weber bar. The vacuum tubes and the vertex building are not open to visitors.
- Is LIGO Livingston different?
- Same instrument design, 3,002 kilometers away in Livingston, Louisiana. The two sites work together: a real gravitational wave shows up at both within roughly 10 milliseconds (light-travel time across the Earth). A signal that only one site sees is rejected.
- What did the 2017 Nobel Prize recognize?
- Decisive contributions to the LIGO detector and the observation of gravitational waves. The prize was awarded one half to Rainer Weiss (MIT), one quarter to Barry C. Barish (Caltech), and one quarter to Kip S. Thorne (Caltech). Ronald Drever, the fourth core LIGO scientist, had died in March 2017; the Nobel cannot be awarded posthumously.
- What can kids do at the visitor center?
- Hands-on exhibits in LExC: a wave-machine demo, a gravity-floor demo, a replica Nobel medal, and the actual 1960s Weber bar on display. On the second-Saturday tour, kids can ask questions in the control room while operators are on shift. Talks are pitched at ages 12 and up; the exhibits work for younger visitors too.
III
A century from Einstein to the chirp
Who shaped this place
Indigenous nations
- Wanapum People — River People. The Wanapum were displaced from this specific land to Priest Rapids on March 6, 1943, when the federal government issued 30-day vacate notices for the Manhattan Project, with no compensation. The LIGO Hanford detector now sits on that same federal reservation.
- Confederated Tribes and Bands of the Yakama Nation — Signatories to the 1855 Treaty with the United States. Treaty-recognized homeland of the Hanford reservation.
- Confederated Tribes of the Umatilla Indian Reservation — Treaty-recognized homeland of the Hanford reservation; current consultation partner with DOE.
- Confederated Tribes of the Colville Reservation — Treaty-recognized homeland of the Hanford reservation; current consultation partner with DOE.
- Nez Perce Tribe — Used the Hanford Reach for fishing and gathering. Ancestral use of the reach dates back at least 10,000 years per the US Fish and Wildlife Service Comprehensive Conservation Plan.
Timeline
Einstein predicts gravitational waves
In a follow-up paper to general relativity, Einstein predicts that accelerating masses radiate ripples in spacetime. He doubts they can ever be detected directly.
Federal vacate order displaces the Wanapum
On March 6, the federal government issues 30-day vacate notices for the land that will become the Manhattan Project's Hanford reservation. The Wanapum, ancestral River People, are moved from this stretch of the Columbia to Priest Rapids with no compensation. The same federal reservation will host LIGO Hanford 50 years later.
Joseph Weber publishes the bar-detector design
Weber, at the University of Maryland, publishes the design for a resonant-bar gravitational-wave detector. His operational aluminum bar goes live in 1965 and is the field's first dedicated instrument.
Weber announces detection, later disputed
Weber announces detection of gravitational waves at a general-relativity conference. Subsequent attempts to reproduce the result fail; methodology problems are identified in the 1970s.
Rai Weiss proposes a kilometer-scale interferometer
At MIT, Rainer Weiss writes an unpublished but widely-circulated report describing how a kilometer-scale laser interferometer could detect gravitational waves. The document becomes the technical seed for LIGO.
NSF awards first research funding
The National Science Foundation funds initial gravitational-wave research at Caltech and MIT. Ronald Drever joins the Caltech effort the same year; Kip Thorne is already there building the theoretical case.
LIGO is established as a Caltech and MIT collaboration
Caltech and MIT formally establish the LIGO Project. Weiss, Thorne, and Drever are the three principal scientists. Governance is shared between the two institutions.
NSF approves construction; sites selected
NSF approves LIGO construction at a budget that makes it the largest project the agency has ever funded. The sites: Hanford, Washington and Livingston, Louisiana, 3,002 kilometers apart.
Ground broken at Hanford
Construction begins at Hanford in late 1994 and Livingston in 1995. Barry Barish becomes principal investigator in 1994, then director in 1997, taking the project from prototype to operational observatory across two sites.
Inauguration
The LIGO inauguration ceremony is held with both detectors built. Initial commissioning runs follow.
Initial LIGO is decommissioned for the upgrade
Eight years of first-generation runs reach design sensitivity but record no confirmed gravitational-wave events. Initial LIGO is decommissioned in 2010 to make room for Advanced LIGO.
Advanced LIGO comes online
A five-year, roughly 200-million-dollar upgrade installs new mirrors, lasers, and seismic isolation. Sensitivity improves by a factor of ten, bringing the detectable volume of space to about 1,000 times the initial design.
GW150914, the chirp
On September 14, 2015 at 09:50:45 UTC, Advanced LIGO records gravitational waves from two black holes of about 30 solar masses each, merging 1.3 billion light-years away. Livingston sees the signal 7 milliseconds before Hanford. Detection happens four days before the official observing run starts.
Public announcement of GW150914
On February 11, the LIGO Scientific Collaboration and Virgo Collaboration announce the detection in a press conference and a paper in Physical Review Letters. The 7-millisecond delay confirms the wave's direction on the sky.
Nobel Prize in Physics
On October 3, the Royal Swedish Academy awards the Nobel Prize in Physics to Rainer Weiss (one half), Barry C. Barish (one quarter), and Kip S. Thorne (one quarter) for decisive contributions to the LIGO detector and the observation of gravitational waves.