For Thursday morning Australian physicist Robert Foot thinks invisible asteroids have bombarded Earth in the past, unseen comets may be headed our way as you read this. In fact everything in the cosmos has a mysterious "mirror matter" counterpart, from stars to planets and even you.
Mainstream scientists are skeptical of the whole theory of mirror matter. It has been around for decades and is invoked by some to explain "
dark matter," an unobserved but significant amount of mysterious material that scientists say must exist based on the effects of gravity they observe in galaxies.Mirror matter theory holds that for each of the known basic particles, such as the electron, proton and photon, there is a distinct mirror partner. Because we are made of ordinary matter, the thinking goes, the mirror universe and its contents are invisible to us. But mirror matter would have mass, and so it would interact gravitationally with the observable universe.
A handful of physicists around the world adhere to the idea.
"If mirror matter exists, then there should exist also mirror stars, mirror planets, even mirror life," says Foot, author of a new book, "Shadowlands: Quest for Mirror Matter in the Universe" (Upublish.com).
Mainstream scientists don't all rule out mirror matter.
"The idea of mirror matter is plausible, and as such it should be looked into," said MIT researcher John Arabadjis, who studies
dark matter. "However, the evidence that has been used to support the idea that mirror matter actually exists in large quantities is, I think, very flimsy."Foot's latest defenses of the theory stretch plausibility beyond what Arabadjis and other researchers are willing to accept. In a statement issued this week by the University of Melbourne, where he works, Foot claims that a longstanding puzzle over "missing" comets could be explained by mirror matter.
Missing comets
For 50 years or so, astronomers have known that most comets come from a distant region of the solar system called the Oort Cloud. Theory predicts that more comets should make second trips through the inner solar system than what astronomers observe. In a recent issue of the journal Science, researchers said the best explanation is that the comets simply disintegrate.
But Foot has another explanation. He said the missing comets "could simply be mirror comets with embedded ordinary matter. Once they have passed the Sun, their ordinary volatile components progressively burn off, leaving an invisible mirror-matter core. This would explain why so many simply fade away."
Harold Levison, of the Southwest Research Institute and lead author of the
comet study published in Science, disagrees."The only reason I can see for invoking mirror matter here is if we did not understand what happened to the comets," Levison told SPACE.com. "However, we do. They disintegrate. It has been observed many times."
A
photograph of just such an event, released earlier this week, supports Levison's view.Exploding asteroids
Foot further claims that an infamous 1908 event in Siberia, an explosion that flattened thousands of acres of forest but left behind no hard evidence for the cause, involved mirror matter. All leading asteroid experts believe this so-called Tunguska event was caused by an asteroid that exploded above the surface, torn apart by atmospheric friction.
According to Foot, the atmosphere could cause heat to build up within a mirror asteroid, causing it to explode and making it visible, though no ordinary matter would be left behind.
He also cites an event reportedly observed in Jordan in April 2001. A ball of light was said to streak across the sky at low altitude, break in two, and then slam into a hill. Local astronomers found scorched trees but no crater.
"These events cannot be explained in terms of a space body made of ordinary matter," Foot said. "If the Jordan space body was made of ordinary matter it should have lit up a large part of the Middle East. This was not observed."
He goes on to suggest that tons of mirror matter might lie hidden just below the surface of these sites, waiting to be found. Mirror atoms could be sorted out in a centrifuge, he says.
Levison doesn't think there are any mysteries to look into in Jordan or Tunguska.
"It is well known and modeled that small, normal, rocky or icy impactors will disintegrate in the atmosphere before they strike the surface of the Earth," Levison explained. "These small objects can be moving fast enough that they cause a huge explosion at high altitudes without leaving a crater. I really don't think you need to invoke strange physics to understand the astronomical phenomena described" by Foot.
Until and unless the mystery of dark matter is unraveled, however, mirror matter theory is not likely to go away. And though it might not be needed to explain missing comets or mysterious explosions, there could be something to it.
Physics can be strange, points out Arabadjis, the MIT researcher.
When Paul Dirac used math to predict in the 1920s that basic particles have associated antiparticles, the idea "was so unbelievable to him that, well, he refused to believe it at first," Arabadjis said. Later experiments detected these antiparticles (though most scientists do not believe antimatter equals or begets mirror matter).
And over the past few years, astronomers have realized that the universe's expansion is actually accelerating, something Arabadjis calls "a truly bizarre result" that can't be explained. Exotic "
dark energy" has been proposed as a possible repulsive force behind this mystery."To be fair, physics sometimes produces really bizarre answers," Arabadjis said.
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