Scientists have developed the MEDE model — an extension of phenomenological dark energy models, where it appears late and then fades over time. This allows a smooth crossing of the 'phantom divide' (the boundary where the equation of state w < -1), as recent observations suggest. A joint analysis of cosmic microwave background, baryon acoustic oscillations, and supernova data favors this model over standard ΛCDM, making it competitive with the dynamical parametrization CPL. Imagine a cosmic 'wave' that rolls in and recedes — that's how dark energy behaves in this picture.
Since the late 20th century, astronomers have known that the recession of galaxies is accelerating, as if pushed by an invisible tailwind. This mysterious force was dubbed dark energy and long thought to be a steady, unchanging breeze — for its discovery, Adam Riess and Saul Perlmutter were awarded the Nobel Prize.
The MEDE model breaks this canon: dark energy is not an eternal wind, but a temporary gust that arose when the Universe had lived half its current age. Two simple numbers — the moment of appearance and the strength of the pull — fully define its character. Comparison with data from distant stellar explosions and the afterglow of the Big Bang revealed something unexpected: this 'scheduled wind' aligns with reality better than the classical, undiminishing tug. Moreover, this gust is not perfectly smooth: its strength apparently fluctuated, crossing a mysterious threshold where pressure begins to exceed energy, and MEDE naturally explains such jumps.
The most intriguing part — in the future, this gust will die out, and the expansion of the cosmos will continue by inertia, like a bicycle that's no longer being pedaled. The irony is that the greatest force accelerating the Universe turns out to be just an episode.
🎯 If the model is correct, in the distant future dark energy will disappear, and the expansion of space will continue only due to the accumulated momentum.