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PHVSICS OF THE IMPOSSIBLE
causality, but they don't exist anymore. In fact, they might have played
an essential role in getting the universe to "bang" in the first place. In
that sense, tachyons are essential for some theories of the big bang.
Tachyons have a peculiar property. When you put them into any
theory, they destabilize the "vacuum," that is, the lowest energy state
of a system. If a system has tachyons, it is in a "false vacuum," so the
system is unstable and will decay down to the true vacuum.
Think of a dam that holds back the water in a lake. This represents
the "false vacuum." Although the dam appears perfectly stable, there is
an energy state that is lower than the dam. If a crack develops in the
dam and the water comes bursting out of the dam break, the system attains the true vacuum as the water flows toward sea level.
In the same way, the universe before the big bang, it is believed,
originally started off in the false vacuum, in which there were
tachyons. But the presence of tachyons meant that this was not the
lowest energy state, and hence the system was unstable. A tiny "rip"
appeared in the fabric of space-time, representing the true vacuum. As
the rip got larger, a bubble emerged. Outside the bubble the tachyons
still exist, but inside the bubble the tachyons have all disappeared. As
the bubble expands, we find the universe as we know it, without
tachyons. This is the big bang.
One theory taken very seriously by cosmologists is that a tachyon,
called the "inflation," started the original process of inflation. As we
mentioned earlier, the inflationary universe theory states that the universe started off as a tiny bubble of space-time that underwent a turbocharged inflationary period. Physicists believe that the universe
originally started off in the false vacuum state, where the inflation field
was a tachyon. But the presence of a tachyon destabilized the vacuum,
and tiny bubbles formed. Inside one of these bubbles the inflation field
assumed the true vacuum state. This bubble then began to inflate rapidly, until it became our universe. Inside our bubble-universe the inflation has disappeared, so it can no longer be detected in our universe.
So tachyons represent a bizarre quantum state in which objects go
faster than light and perhaps even violate causality. But they disappeared a long time ago, and perhaps gave birth to the universe itself.
PHVSICS OF THE IMPOSSIBLE
causality, but they don't exist anymore. In fact, they might have played
an essential role in getting the universe to "bang" in the first place. In
that sense, tachyons are essential for some theories of the big bang.
Tachyons have a peculiar property. When you put them into any
theory, they destabilize the "vacuum," that is, the lowest energy state
of a system. If a system has tachyons, it is in a "false vacuum," so the
system is unstable and will decay down to the true vacuum.
Think of a dam that holds back the water in a lake. This represents
the "false vacuum." Although the dam appears perfectly stable, there is
an energy state that is lower than the dam. If a crack develops in the
dam and the water comes bursting out of the dam break, the system attains the true vacuum as the water flows toward sea level.
In the same way, the universe before the big bang, it is believed,
originally started off in the false vacuum, in which there were
tachyons. But the presence of tachyons meant that this was not the
lowest energy state, and hence the system was unstable. A tiny "rip"
appeared in the fabric of space-time, representing the true vacuum. As
the rip got larger, a bubble emerged. Outside the bubble the tachyons
still exist, but inside the bubble the tachyons have all disappeared. As
the bubble expands, we find the universe as we know it, without
tachyons. This is the big bang.
One theory taken very seriously by cosmologists is that a tachyon,
called the "inflation," started the original process of inflation. As we
mentioned earlier, the inflationary universe theory states that the universe started off as a tiny bubble of space-time that underwent a turbocharged inflationary period. Physicists believe that the universe
originally started off in the false vacuum state, where the inflation field
was a tachyon. But the presence of a tachyon destabilized the vacuum,
and tiny bubbles formed. Inside one of these bubbles the inflation field
assumed the true vacuum state. This bubble then began to inflate rapidly, until it became our universe. Inside our bubble-universe the inflation has disappeared, so it can no longer be detected in our universe.
So tachyons represent a bizarre quantum state in which objects go
faster than light and perhaps even violate causality. But they disappeared a long time ago, and perhaps gave birth to the universe itself.