The concept of extra dimensions, that there are whole other regions of reality that we can’t perceive, has tantalized physicists for years. Although the math looks good (if you like that kind of thing), scientists want physical evidence they can measure. And how do you test for 4 dimensions of space when you’ve only got a 3-dimensional ruler? One idea is to use gravity, a force that might actually reach across an extra dimension and give scientists the evidence they’re looking for. In order to run this experiment, a pair of physicists think the best strategy is to start from scratch and build a whole new solar system… in miniature.
With powerful new equipment and sensitive instruments, astronomers are turning up mysteries faster than they can resolve them. We’ve got a handle on the 4% of the Universe that’s regular matter – while the other 96% is made up of dark matter and dark energy. One possible explanation for dark energy is that it’s not a mystery at all, it’s just regular, familiar gravity acting strangely over large distances. It just takes an extra dimension of space; one that we can’t see with our existing instruments.
A strange coincidence for this “gravity at large scales” theory is hinted at by the Pioneer spacecraft. Astronomers noticed in the 1980s that Pioneer 10 and 11 weren’t exactly where they were supposed to be. Some force is slowing them down, more than can be explained by gravity from the Sun. Unfortunately, the Pioneers are affected by gravity by many different objects, buffeted by the solar wind, blasted by cosmic radiation, and encountering interstellar particles.
Scientists need a better instrument to test their theories; a way to test gravity without outside interference. In a new paper called APSIS – an Artificial Planetary System in Space to probe extra-dimensional gravity and MOND, physicists Varun Sahnia and Yuri Shtanov propose an unusual spacecraft – a miniature solar system.
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They believe a spacecraft carrying a miniature solar system could launched to the L2 Lagrange Point of the Earth-Sun system. This is a spot along the Earth’s orbit where the forces of gravity from the Earth and the Sun cancel out. Spacecraft stationed there are very stable (WMAP’s there already). This artificial solar system would be enclosed within the larger spacecraft that would protect it from cosmic rays, dust, solar wind, and anything else that could interact with the orbiting “planets”. Even the spacecraft’s fuel tank, which will decrease in mass over time would need to be positioned as far away from the mini-planets as possible so they don’t experience changing gravity over time.
Once at the L2 Lagrange Point, the spacecraft would release the mini-planets into elliptical orbits inside its protective shell. Even if the orbits aren’t perfect, the spacecraft would have lasers it could use to make tiny changes with light pressure. The positions of the orbiting mini-planets could be tracked with tremendous precision over the course of several years. Any gravitational anomalies would compound over time, giving cosmologists mountains of data to test for the impact of an extra dimension.
In addition to its main function, the artificial solar system could help cosmologists test other theories of gravity, extra dimensions, dark energy and dark matter.
How many dimensions are there? String theory predicts that there could be 10 dimensions or even more.