A decade has passed since scientists first detected gravitational waves, marking a pivotal moment in astrophysics that transformed our understanding of the universe.
The initial detection occurred on 14 September 2015, when the twin observatories of the Laser Interferometer Gravitational-wave Observatory (LIGO), located in Hanford, Washington, and Livingston, Louisiana, detected ripples in space-time resulting from a black hole merger over a billion years ago, far beyond our galaxy.
This achievement was the culmination of more than 40 years of technological advancements and research in the field.
Since that historic day, the LIGO detectors, along with their counterparts Virgo in Italy and KAGRA in Japan, have significantly improved their abilities, doubling sensitivity and expanding the regions of the universe they can monitor.
As a result, physicists now observe binary black hole mergers approximately every three days, highlighting the progress made in gravitational wave detection.
David Reitze, a physicist at the California Institute of Technology and director of the LIGO observatories, reflects on how gratifying it is to witness such rapid developments, remarking, “It’s only going to get better.”
Looking ahead, researchers in the United States and Europe are eager to build more advanced gravitational wave observatories capable of detecting signals from across the entire observable universe.
One ambitious project is the Cosmic Explorer (CE), a proposed interferometer designed to be ten times longer than LIGO’s current arms, stretching an impressive 40 kilometers.
If constructed, CE could potentially detect about 100,000 black hole mergers annually, including events that occurred over ten billion years ago when star formation and black hole mergers reached their peak.
Reitze emphasizes the importance of delving deeper into the history of the universe, stating, “You really do want to be able to probe farther back.”
Additionally, the Cosmic Explorer is expected to record more than one million neutron star mergers each year, translating to a detection rate of one merge every few seconds, as outlined by Stefan Ballmer, a physicist at Syracuse University.
Despite the promise of this groundbreaking technology, funding poses a significant challenge.
The CE’s extensive design necessitates careful site selection to accommodate its lengthy arms, especially since its endpoints will need to account for the Earth’s curvature.
Physicists are actively exploring several remote locations in the United States that are naturally bowl-shaped, which may lessen the excavation needs for the CE construction.
Currently, LIGO is planning a series of upgrades designated as LIGO A# (A-sharp), which aim to enhance the sensitivity of existing observatories before the end of the decade.
These improvements will focus on increasing laser power and introducing more stable, perfectly reflective mirrors that will be instrumental in detecting minute variations in laser light travel time.
The upgrades could be crucial for testing the new technology envisioned for the CE.
However, the future of these upgrades and the funding for LIGO itself is uncertain, particularly under President Donald Trump’s proposed budget cuts to the U.S. National Science Foundation.
This agency has been pivotal in providing the financial support for LIGO’s development and operation over the years.
Yet, there remains hope among researchers that Congress may opt for less drastic funding reductions, with many eager to see what the future holds for gravitational wave research.
As David Reitze notes, “I think we just have to wait and see.”
In addition to the discussions surrounding LIGO and CE, researchers are also considering the ‘Einstein Telescope’ project, which aims to further enhance gravitational wave detection capabilities, indicating that the field of gravitational wave astronomy is set for an exciting future ahead.
image source from：nature
