Dark energy explained by physicist | Don Lincoln and Lex Fridman
Physicist Don Lincoln discusses dark energy with Lex Fridman, explaining its properties as a constant-density phenomenon tied to the nature of space itself. He speculates that dark energy may be a property of quantized space, with new quanta of space appearing as the universe expands. He also describes near-future experiments using quantum-entangled particles to determine whether gravity is quantized.
Summary
Don Lincoln opens by explaining that dark energy is significant not just as an observed phenomenon but as a mechanism for understanding the deep future of the universe. He notes that if dark energy remains constant, it will increasingly dominate the universe's energy balance and drive accelerated expansion indefinitely. However, he mentions a recent but unconfirmed measurement suggesting dark energy may be decreasing over time, which would challenge the prevailing assumption that it is constant.
Lincoln clarifies a common misconception: when scientists say dark energy is 'constant,' they mean it has a constant *density*, not a constant total energy. Because the volume of the universe is expanding, constant density actually implies that the total amount of dark energy is increasing. By contrast, ordinary matter's density decreases as the universe expands because the same amount of matter is spread over a larger volume.
He then ventures into speculative territory, proposing that dark energy may be a fundamental property of space rather than a field within space. He suggests that if space is quantized — made up of discrete 'quanta' or 'bubbles' — then as the universe expands, new quanta of space are appearing, each carrying a fixed amount of energy. This would naturally explain the constant energy density of dark energy. Lincoln is careful to emphasize this is highly speculative and not accepted science.
Finally, Lincoln describes a potentially near-term experimental approach to test whether gravity is quantized. By using quantum-entangled particles — each existing in two places simultaneously — scientists could measure the gravitational effects in various configurations to determine if gravity behaves as a quantum or continuous phenomenon. While this experiment would not reveal the full nature of quantum gravity, confirming that gravity is quantized would redirect theoretical research and lend support to the idea that space itself may also be quantized.
Key Insights
- Lincoln clarifies that when physicists say dark energy is 'constant,' they mean constant in *density*, not total energy — because as space expands, the total amount of dark energy actually increases while ordinary matter's density dilutes.
- Lincoln speculates that dark energy may be a property of space itself rather than a field within space, and that space may be quantized — with new discrete 'bubbles' of space appearing as the universe expands, each carrying a fixed amount of energy, which would explain the constant density.
- Lincoln mentions a recent but unconfirmed measurement suggesting dark energy may be decreasing over time, which would challenge the long-held assumption that it is constant and could significantly alter predictions about the universe's future.
- Lincoln describes a proposed experiment using quantum-entangled particles to measure gravitational forces across multiple positional configurations, which could definitively determine whether gravity is a quantum or continuous phenomenon — potentially testable with near-future instrumentation.
- Lincoln argues that confirming gravity is quantized, even without a full theory of quantum gravity, would be scientifically transformative because it would eliminate continuous-gravity models and push the theoretical community toward quantum approaches, and could further support the idea that space itself is quantized.
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