"And he shall speak great
words against the most High, and shall wear out the
saints of the most High, and think to change times and
laws." Daniel 7:25
Travelling in time might sound like a
flight of fancy, but some physicists think it might
really be possible. BBC Horizon looked at some of the
most promising ideas for turning this staple of science
fiction into reality.
Ron Mallett has a dream: He wants to
travel in time.
This isn't mere fantasy - Mallett is
a respected professor of physics.
"I think of myself as being an
ordinary person with a passion, and my passion is the
possibility of time travel," he says.
Prof Mallett has wanted to build a
time machine for most of his life. His passion, he
explains, can be traced to a tragic event early in his
Ron's father, a heavy smoker, died of
a heart attack at the age of 33 - when Prof Mallett was
just 10 years of age. Ron was devastated and withdrew
into his books.
"A year after that when I was 11,
I came across the book that changed everything for me.
That was The Time Machine, by HG Wells," the
University of Connecticut physicist told the BBC's
"The cover caught my attention, but it was when I
read the inside, and it said: 'Scientific people know
very well that time is just a kind of space and that we
can move forward and backwards in time, just as we can…
in space'. "When I read that I said: 'This is
Prof Mallett explains: "If I could
build a time machine, then I could go back into the past
and see my father again and maybe save his life and
Time travel may sound far-fetched, but scientists are
already exploring several mysteries of nature that could
one day see Ron's dream fulfilled.
Albert Einstein thought the three
dimensions of space were linked to time - which serves
as a fourth dimension. He called this system space-time,
and it's the model of the Universe that we use today.
But Einstein also thought it was
possible to fold space-time, creating a shortcut between
two distant locations. This phenomenon is called a
wormhole, and it can be visualised as a tunnel with two
openings, each emerging at different points in
Wormholes might exist naturally in
the cosmos; indeed, scientists in Russia are trying to
use radio telescopes to detect them. But using wormholes
for time travel won't be straightforward.
The nearest ones could be many light-years away. And
even if you could get to them and then survive the
journey through them, there's no guarantee where you'd
But some physicists have speculated
that we might be able to conjure up bespoke wormholes at
some point in the future - though we currently have no
Physics also predicts that wormholes
would have a habit of collapsing, crushing whatever's
inside them. If a time machine is ever to exploit them,
we'd have to find a way to stop this inconvenient
The mysterious phenomenon of dark
energy might provide a solution. In the 1990s,
astronomers found that the expansion of the Universe was
speeding up, rather than slowing down as might have been
"Something out there is having an
'anti-gravity' effect - it's pushing rather than
pulling. We don't know what that is, but it makes up
most of the Universe. We call it dark energy," says
Prof Tamara Davis, a cosmologist at the University of
Queensland in Australia.
A wormhole will only work for time travel if its "mouth"
can be held open for long enough that it allows
something to travel through it. That requires something
called negative energy, which doesn't really exist in
the everyday world.
But the dark energy that permeates
the cosmos fits the bill - if we can figure out what it
is, we might be able to prop open a wormhole long enough
to go in one end and out the other.
"We don't know whether we are able
to make a wormhole, whether that's technically within
our capabilities… But who knows what a future human
civilization is going to be able to do," says Prof
"Technology has advanced so
rapidly that maybe space and time themselves are
something that can come under our control."
Wormholes exist at the more
speculative end of physics, offering one approach to
travelling in time. But Ron Mallett has another.
He has drawn up plans for an actual
time machine, and his concept was inspired by a book he
read at age 12 about Albert Einstein's equations.
Prof Mallett has built a table-top
device that illustrates principles he thinks could be
used to build a real, working time machine. First,
lasers are used to generate a circulating beam of light.
The space inside this "ring laser" should become
twisted, "like stirring a cup of coffee", the
University of Connecticut professor explains.
Because space and time are intimately connected, warping
space should also warp time. Prof Mallett's theoretical
work has shown that, given enough laser intensity in a
small enough space, it should be possible to alter the
normally linear timeline we all inhabit.
"If space is being twisted
strongly enough, this linear timeline is going to be
twisted into a loop. If time all of a sudden is twisted
into a loop that allows us the possibility of travelling
into the past," says Ron Mallett.
However, in order to make it work,
the concept would require vast amounts of power and a
way of shrinking everything to a microscopic scale.
But once we have a time machine,
using it successfully will require a detailed
understanding of time itself.
The generally accepted view is that
the Universe is an unchanging "block" of space-time;
this idea arises directly from Einstein's equations.
"What's important about the model
is the idea that the past, present and future are all
equally real. So you can think of everything that ever
did exist, does exist or will exist as all somehow being
out there in space-time," says Dr Kristie Miller,
director of the Centre for Time at the University of
"The dinosaurs are all out there
somewhere in the past doing dinosaur stuff, we're all
here now and all of the future is out there somewhere in
One way to visualise the block model is to think of
other places in time as being like other places in
space: "We are here in Sydney, but there are other
people located in Singapore and London. Those places are
perfectly real, it's just that we aren't at them,"
says Dr Miller.
This is good news for the budding
time traveller, because it suggests there is nothing to
stop us from swapping where we are now for some other
place and time.
But, importantly, it also implies
that the past, present and the future are already
written, so that if we were to travel back in time, we
wouldn't be able to alter it. To take an oft-quoted
example, we shouldn't be able to kill someone's
grandparent so that their descendant will cease to exist
in the future.
The block model treats our everyday
concept of time as an illusion, a way that humans
rationalise reality. But Prof Lee Smolin, from the
Perimeter Institute in Waterloo, Canada, disagrees. He
believes that the passage of time is a real and
"Time travel is probably impossible," he says. "If
what's real is the present moment and the past is only
real in the sense that there are memories and records of
it in the present, and the future is still to exist…
there's nowhere to go."
His colleague Prof Neil Turok,
director of the Perimeter Institute, thinks the weird
world of quantum physics could be crucial to answering
This area of physics emerges at very
small scales, where the rules of classical physics we
learnt about in our school textbooks break down. For
example, in the quantum world, it might be possible for
a particle to be in many places at once.
"I think it's clear to me that
there is some probability of us going backwards in
time," he says. "In quantum physics, nothing is
impossible - particles travel through walls!"
Prof Turok explains that time travel
remains a distant hope because "no one really has any
plausible idea of how to go backwards in time right now".
But he adds: "One should never say never, because
some clever person will come along and tell you how to
break the rule."
The work being done in this area
along with what we have seen with CERN begs the question
as to whether mankind will reach a stage of
technological advancement that time itself could be
manipulated. This is actually one of the areas that some
researchers believe will involve the Antichrist due to
the passage in Daniel 7:25 referencing the Antichrist
seeking to change time. Is there a link here that needs
to be explored further? In what context is Daniel making
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