Almost all the ground-breaking
ideas look ridiculous at the start, same thing happened with concept of Multiverse.
A recently published research paper by a team of physicists revolves around
the same idea. Alexander Vilenkin, co-author
of the paer, professor of physics and director of the Institute of Cosmology at
Tufts University said: “Fifteen years ago, when you talked about the
multiverse, the attitude of many physicists was just ridicule, but there has
been a great change in attitude.”
The concept of a multiverse
is debatable and, at times, argumentative. Today, many scientists are
understandably doubtful about this concept. A few even reject the notion
completely. But for others like Vilenkin, the arguments for the multiverse are
so persuasive, they inspire others to think about it.
Vilenkin, who introduced the
idea of quantum creation of the universe from a quantum vacuum believes that
there could be infinite universes jam-packed with the different versions of
ourselves.
Another idea is also famous
among physicists that the Big Bang might not be the singular creation of all
space and time. There may have been other circumstances creating other
universes: a multiverse. Same as almost 100 years ago there was the concept
that Milky Way is the whole universe, then it was discovered that many other galaxies
exist outside the limits of our home galaxy.
Vahe Petrosian, a Stanford
professor of physics and of applied physics said:
“What lies beyond the visible
bounds of our universe? When I teach elementary courses, I usually say the
universe is everything that there is, If you go to the edge of it and there is
still some more, that is part of the universe, too”.
In late 2015, Vilenkin and
his colleagues proposed another way to determine if the multiverse exists:
black holes. Vilenkin says that there is a fair possibility that bubble
universes were shaped inside of the visible universe during the Big Bang. Many
of these universes warped up and made black holes. If the black holes are big
enough, they may have expanding universes inside of them, and these expanding
universes would be connected to the visible universe by wormholes.
About 13.8 billion years ago
Big Bang happened, a really hot, compact phase when the universe started
expanding. But there is also a universe that is restricted by what people can see:
the visible universe. Everything in the visible universe has to be younger than
that. But, hypothetically, researchers are uncertain that the universe seen
with telescopes, what we see may not the all that is there.
Petrosian said:
“You say this is the
beginning, and then you ask, ‘What was before that?’ If you go to some edge,
there is always the question, ‘Is there something beyond that edge? Say, what
are the possibilities, what happens if these bubbles interact, what sort of
information it will give us, once a reasonable idea comes, you can never say it’s
wrong. This is not too crazy. We will probably never have answers to these
questions, but it is important to ask them. So we do ask, and sometimes we are
successful.”
Inflation would thus leave
behind a population of black holes with a telltale range of masses. In
principle, by measuring the ripples in space and time produced in black hole
collisions—like the gravitational waves discovered by LIGO last
year—astronomers can take a census of black hole masses and see if they were
created by inflation, which would imply the multiverse.
But there is also a universe
that is limited by what people can see: the visible universe. Around 13.8
billion years ago there was a Big Bang, a really hot, dense phase when the
universe started expanding. Everything in the visible universe has to be
younger than that. But, theoretically, people suspect that the universe seen
with telescopes – what we see within the horizon of the Big Bang – may not be
all there is.
“You say this is the beginning,
and then you ask, ‘What was before that?’ If you go to some edge, there is
always the question, ‘Is there something beyond that edge?'” Petrosian said.
The theory of eternal
inflation, proposed in part by Vilenkin, could begin to answer these questions.
Eternal inflation says that space is always expanding overall, but some pockets
of space will expand and create universes while others stop expanding. The
universes that form are called “bubble universes” because they bubble up where
energy is being concentrated.
“We used to think that
beyond the visible universe there was simply more of the same,” said Vilenkin.
“More planets and stars and galaxies. But other universes may have different
physical laws.”
Not all bubble universes are
created equally. If the mass of a proton or electron were tweaked, the universe
might not have stars, planets or life. Some of the universes expand, contract
and collapse in a very short time before forming everything. Some universes are
like ours.
It’s possible that sometimes
these bubbles interact, and that one will interact with our bubble and produce
observational evidence. “Say, what are the possibilities, what happens if these
bubbles interact, what sort of information will it give us,” says Petrosian.
Despite the similarities
between Vilenkin’s theory and the film
Interstellar, many scientists have hope for the multiverse theory.
“Once a reasonable idea
comes, you can never say it’s wrong,” affirms Petrosian. “And this is not too
crazy. We will probably never have answers to these questions, but it is
important to ask them. So we do ask, and sometimes we are successful.”
Source: Stanford University and NPR Science Friday
