So far we humans can measure many things, but certainly not all or even most things that we will one day be able to measure. Could a Quantum Gravimeter Detect a Primordial Black Hole Inside the Earth? Probably not, and this may be why the mystery of dark matter exists.
Primordial black holes (PBHs) are hypothetical objects that may have formed in the early universe, shortly after the Big Bang[9][10]. Unlike stellar black holes that form from collapsing stars, primordial black holes could be much smaller, potentially as small as a dime or even smaller than a proton[9]. These miniature black holes have been proposed as potential candidates for dark matter and could provide insights into the early universe and quantum gravity[10][11]. The detection of primordial black holes has been a challenging endeavor, with scientists exploring various methods including gravitational lensing, gravitational waves, and potential particle emissions[9][12]. The question of whether current quantum gravimeters could detect a primordial black hole inside the Earth is intriguing, as it combines the cutting-edge technology of quantum sensors with the search for these elusive cosmic objects.
Challenges in Detecting Earth-Based PBHs
Size and mass: PBHs that could exist within the Earth would likely be extremely small and low-mass. Current detection capabilities are limited to objects with masses around 100 megatons and only if they pass very close to detectors[3]. Sensitivity: Quantum gravimeters would need to be extraordinarily sensitive to detect the gravitational effects of such small objects within the Earth’s much larger gravitational field. Distinguishing signals: Differentiating the gravitational signal of a PBH from other gravitational anomalies within the Earth would be extremely challenging.
Quantum Gravimeters: The Most Sensitive Human Gravity Measuring Instruments
Quantum gravimeters represent the cutting edge of gravity measurement technology. These instruments are the most sensitive human-made devices for measuring gravity.
Key Features of Quantum Gravimeters
- Use freely falling atoms as test masses
- Employ quantum mechanical techniques
- Can measure gravity changes with accuracies in the range of a few tens of nm/s2
- Combine portability, absolute measurement capability, and continuous operation
How Quantum Gravimeters Work
- Atoms are trapped in a vacuum chamber and cooled to microkelvin temperatures
- The atoms are released or launched upwards in free fall
- Their acceleration is measured using atom interferometry
- Atoms are exposed to a sequence of laser pulses during their fall
- The final state of the atoms depends directly on the local acceleration of gravity
Advantages of Quantum Gravimeters
- Provide absolute measurements tied to metrological standards
- Have very little recoil due to tiny test masses
- Can operate continuously at a high rate with no moving parts
- Demonstrate excellent short-term stability
Other Highly Sensitive Gravimeters
- Superconducting gravimeters: Can detect gravity changes as small as 10-12 g
- FG5 absolute gravimeter: Achieves repeatability better than ±1 μGal (10 nm/s2)
Applications
- Geodetic measurements
- Monitoring geodynamic and geophysical processes
- Detecting changes in groundwater, glacier melting, and volcanic activity
- Mineral and oil exploration
- Fundamental physics research
The Hunt for Dark Matter
The mystery of dark matter continues to challenge astronomers and physicists. We know it exists due to observations of galactic rotation rates, which reveal that galaxies contain more mass than visible matter can account for. One possibility is that this additional mass consists of primordial black holes—small, dense objects formed in the early universe—that are too faint to detect individually with our current instruments. To meet this challenge, scientists are developing increasingly sensitive gravimeters that enhance our ability to measure gravitational fields and their variations. These advancements may not only deepen our understanding of Earth’s gravity but may finally explain dark matter and the universe’s structure.
So what? Energy and Resource Exploitation
Primordial black holes (PBHs) present intriguing possibilities for future energy production and space travel, though these concepts remain largely theoretical. Smaller PBHs could potentially be harnessed for energy through Hawking radiation, a phenomenon where black holes emit thermal radiation as they evaporate. Theoretically, smaller PBHs would emit Hawking radiation more rapidly and energetically. However, the challenges in detecting and capturing suitable PBHs are significant, as they are hypothesized to be incredibly small and fast-moving. Additionally, the energy output from Hawking radiation would likely be minimal for all but the tiniest PBHs, which would evaporate almost instantaneously.
On the other hand, the strong gravitational fields of larger PBHs could be utilized for advanced space travel concepts or energy generation in the distant future. For instance, spacecraft could theoretically employ gravitational slingshot maneuvers around these black holes to gain acceleration. Moreover, larger PBHs could power speculative concepts like Alcubierre warp drives or tap into the rotational energy of spinning black holes through processes such as the Penrose process. However, safely approaching and utilizing such extreme gravitational environments would require technology far beyond our current capabilities, and the nearest suitable PBH may be incredibly far from our solar system, making practical use unlikely in the foreseeable future.
Future Anti-Gravity Uses of PBHs
Understanding dark matter may have very practical uses, even allowing future technolgoies that enable survival of our species. The concept of using a primordial black hole (PBH) to generate an apparent anti-gravity effect is highly speculative and far beyond our current technological capabilities. In theory, however, a sufficiently massive PBH could create an extremely strong gravitational field that might be manipulated to counteract Earth’s gravity or provide propulsion for advanced spacecraft. The challenges of detecting, capturing, and controlling a PBH are immense, given their hypothesized small size and the extreme nature of their gravitational fields[17]. Additionally, the intense gravitational forces and potential Hawking radiation from a PBH would likely make it incredibly dangerous to work with, even if we could somehow harness one. While the idea is fascinating to consider, it remains firmly in the realm of science fiction for the foreseeable future, as our current understanding of PBHs is primarily focused on their potential role in dark matter and early universe formation rather than practical applications[16][17].
Read More
[1] https://www.si.edu/object/nmah_865075
[2] https://www.sciencenews.org/article/gravimeter-measures-shifts-earth-gravitational-fields
[3] https://flightopportunities.ndc.nasa.gov/technologies/158/
[4] https://ggos.org/item/quantum-gravimetry/
[5] https://www.ngs.noaa.gov/GRD/GRAVITY/GRAV_APPL.html
[6] https://www.nist.gov/how-do-you-measure-it/how-do-you-measure-strength-gravity
[7] https://www.usgs.gov/observatories/hvo/news/volcano-watch-new-instrument-new-potential-absolute-quantum-gravimeter
[8] https://www.proquest.com/docview/2535415953?fromopenview=true&pq-origsite=gscholar
[9] https://www.space.com/black-holes-missing-big-bang-primordial
[10] https://arxiv.org/html/2405.08624v1
[11] https://en.wikipedia.org/wiki/Micro_black_hole
[12] https://www.advancedsciencenews.com/astronomers-might-have-a-shot-at-imaging-primordial-black-holes/
[13] https://link.aps.org/doi/10.1103/PhysRevD.110.063029
[14] https://arxiv.org/abs/2301.11439
[15] https://inspirehep.net/literature/1485664
[16] http://arxiv.org/pdf/2401.16069.pdf
[17] https://en.wikipedia.org/wiki/Primordial_black_hole
[18] https://www.physicsforums.com/threads/accretion-in-extreme-conditions-pbhs-more.779232/
[19] https://science.nasa.gov/mission/hubble/observatory/design/electrical-power/
[20] https://www.sciencedirect.com/science/article/pii/S0550321324000944
[21] https://link.aps.org/pdf/10.1103/PhysRevD.108.023531
[22] https://arxiv.org/pdf/2207.11041.pdf
[23] https://www.sciencedirect.com/science/article/pii/S0370269321006626
