Ideas Lab: Measuring "Big G" Challenge | Apply Online

Frequently Asked Questions (FAQs)

What is the "Ideas Lab: Measuring 'Big G' Challenge"?

It is a National Science Foundation (NSF) funding opportunity organized as an "Ideas Lab" and led by the Physics Division within the Mathematical and Physical Sciences (MPS) Directorate. The effort is centered on a specific grand challenge in fundamental physics: developing experiments that can measure Newton's gravitational constant, G, more reliably and consistently than current approaches.

Which NSF unit is leading this opportunity?

The opportunity is led by the Physics Division in NSF's Mathematical and Physical Sciences Directorate.

What scientific problem is this opportunity trying to solve?

The program targets a long-standing problem in physics: establishing a truly reliable value for Newton's gravitational constant (G). Despite centuries of work and many experiments, modern measurements of G still disagree with each other in a persistent way, pointing to unresolved issues such as systematic errors, incomplete modeling, or limitations in existing measurement techniques.

What is Newton's gravitational constant (G), and why does it matter?

G sets the strength of gravity. Gravity is the weakest of the four fundamental interactions, but G is still central because it connects mass to gravitational force and appears broadly across gravitational theory and measurement. A dependable value for G matters both for foundational physics and for the broader ability to measure extremely small forces accurately.

How big is the disagreement in current measurements of G?

Recent measurements do not line up, with some results differing by about 0.05. This spread is described as roughly 40 times larger than the quoted uncertainty of the most precise experiment, which suggests the problem is not just incremental improvement but persistent discrepancies likely driven by unaccounted systematics or modeling limitations.

Why has G been so difficult to measure consistently?

Based on the solicitation description, the disagreement likely reflects issues such as unaccounted systematic errors, incomplete modeling of subtle experimental effects, or limitations in the existing measurement methods. The challenge is not only achieving high precision, but achieving reproducibility and convergence across independent experiments.

What are the main motivations NSF highlights for resolving the G discrepancy?

The solicitation describes two core motivations:

• Foundational motivation: Work toward theories that unify gravitation with quantum physics (including efforts framed around unifying gravity with quantum electrodynamics or more broadly quantum field theory). If a successful theory can predict G, then a high-confidence experimental value becomes an essential benchmark for testing or falsifying those theories.
• Practical and cross-cutting motivation: Measuring G requires extremely precise absolute measurement of very small forces. Improving these capabilities has downstream value across measurement science in other domains where tiny forces and subtle systematics matter.

What kinds of broader applications are connected to better small-force measurements?

The opportunity notes that the same experimental challenges and systematic effects involved in measuring G also appear in other areas, including precision metrology, studies of the Casimir effect, calibration of spring constants in atomic force microscopy (AFM) cantilevers, and certain measurements relevant to intermolecular forces and biological systems such as DNA.

What is an NSF "Ideas Lab," and how is it different from a standard proposal call?

An Ideas Lab is described as an intensive, workshop-like research development process focused on a specific grand challenge. It is not a conventional proposal call where investigators submit a full research plan upfront. Instead, the Ideas Lab is designed to bring together researchers from different disciplines and backgrounds to push beyond familiar approaches and generate unconventional concepts, new error-mitigation strategies, and alternative measurement architectures.

What is the ultimate scientific aim of this Ideas Lab?

The explicit goal is to catalyze the development of new experiments capable of measuring G with relative uncertainties approaching, or even surpassing, one part in 100,000 (on the order of 10^-5). The emphasis is not only on precision, but on controlling systematic effects so that independent measurements converge on the same value.

What does the target uncertainty "one part in 100,000" mean in this context?

It refers to a relative uncertainty goal on the order of 10^-5 for measuring G. The solicitation frames this as a demanding benchmark intended to drive next-generation experimental designs and stronger mitigation of systematic errors.

What types of approaches or outcomes is the Ideas Lab trying to encourage?

The solicitation emphasizes cross-disciplinary "cross-pollination" aimed at producing unconventional experimental concepts, improved strategies for addressing systematic errors, and alternative measurement architectures that can deliver more consistent and reproducible measurements of G.

What is the first step for applicants?

The opportunity begins with a preliminary proposal stage. The preliminary proposal is focused on participating in the Ideas Lab itself, rather than immediately requesting full research funding.

How do U.S. researchers apply to participate?

U.S. researchers are instructed to submit preliminary proposals for participation through NSF FastLane.

Does this opportunity require multidisciplinary participation?

Yes. The Ideas Lab model is explicitly designed to mix researchers from different disciplines and backgrounds. The expectation is that the resulting projects and teams developed through the process will be genuinely multidisciplinary and aligned with the central measurement challenge.

When does full research proposal development happen?

Full proposals are expected to be developed after the Ideas Lab. The Ideas Lab process is intended to help shape teams and refine the most promising concepts into stronger, more integrated research plans that can then be submitted as full proposals.

What kinds of projects does NSF expect to come out of the Ideas Lab?

The solicitation anticipates projects that are multidisciplinary and directly aligned with creating next-generation measurements of the gravitational constant. These projects should be positioned to reduce or resolve the persistent disagreement among measurements by improving both precision and control of systematic effects, ultimately supporting validation, challenge, or extension of current understanding and calculations.

Is the goal only to make measurements more precise?

No. While the relative uncertainty target is a key driver, the solicitation also stresses the need for better control of systematic effects and improved reproducibility so that independent experiments converge on the same value rather than continuing to disagree.