When you
stop to think about it, time is an arbitrary concept that we use to explain how
we get older and older. It’s merely a tenacious illusion that tries to explain
everything.
Time is
the subject of many quotations. One of my favorite quotations is from Abhijit
Naskar, author of “Love, God & Neurons: Memoir of a Scientist Who
Found Himself By Getting Lost.” He declared, “Time is essentially a
mental construct designed to support our perception of temporal presence in the
vastness of space. The past and future would not actually exist without the
neurons that build a virtual perception of them based on all of our
experiences. The now is all that exists.
Albert
Einstein, one of the most important scientists of all time, expressed a similar
viewpoint in his writing: “People like us who believe in physics know that
the distinction between past, present, and future is only a stubbornly
persistent illusion.” Time is an illusion, to put it another way.
Time is an
arbitrary construct, which makes sense when you consider that it’s how we make
sense of aging and growing older as the world changes all around us. It’s not
that complicated. So let’s examine how different locales affect how we perceive
time.
It’s All
Relative
According to Einstein’s own theories, time moves differently for
those living at sea level compared to those who are perched atop the world’s
tallest mountains (some studies claim that at sea level, you age one billionth
of a second slower annually than if you were living atop Mount Everest). This
is because of gravitational time dilation, a phenomena suggested by general
relativity.
The
explanation for gravitational time dilation is quite straightforward: Large
mass objects provide a potent gravitational field. These objects’ gravitational
fields produce what is known as gravity, which is noticeable warping of the
spacetime fabric. The stream of photons traveling at the speed of light appears
to bend when it encounters an object with enough gravity.
What’s
even more intriguing is that mass may warp time itself, making it move more
slowly or more quickly depending on the mass and gravitational pull of the
item. This is where our understanding of time dilation is thrown off.
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An astronaut venturing into a black hole.Source: NASA |
However,
it should be remembered that a person in significant gravity perceives time to
be moving normally. Time only moves slowly in relation to a reference frame
with weaker gravity.
A person
under strong gravity perceives time as moving regularly, whereas a clock with
weak gravity ticks quickly. While the clock appears to operate regularly to
someone in mild gravity, it moves slowly under strong gravity. The clocks are
in perfect working order, of course. Due to the relativistic warping of space
and time caused by mass, time is both slowing down and speeding up.
The sense
of time slows down as one moves quicker compared to a static observer. In
relation to a stationary point, matter moving at the speed of light does not actually
sense time or distance. People on Earth see a spaceship as traveling through
space and time considerably more slowly than how the people on board the ship
feel it is moving while they are simply watching it drift off into deep space.
The crew would age more slowly as they move more quickly.
Making
Time Dilation Simple
Here’s another fun illustration: Time dilation is shown
in the film “Interstellar” (spoilers ahead, obviously). In the film,
a team departs Earth in quest of a planet that is able to support life so that
we can abandon the dying Earth. A few crew members arrive on a water world near
a massive black hole/wormhole at one point in the movie. The planet experiences
waves that are unimaginably volatile due to its proximity to the extremely
dense star object, and temporal dilation becomes severe. For someone outside
the black hole’s orbit, one hour on the surface was equivalent to seven years.
Given that
the International Space Station is not moving at relativistic speeds,
astronauts on board suffer a considerably milder kind of time dilation. In an
experiment involving two identical twin astronauts, NASA determined that the
twin who spent the most time in space aged 5 milliseconds more than his
Earthbound sibling.
It Gets Even Weirder
Black holes and their surroundings may contain the wackiest instance
of time dilation. The closer you are to a black hole’s event horizon, the more
strangely time moves. If you had two clocks, one held by an observer outside
the object’s incredibly high gravity and the other by an observer passing by
the event horizon, the clock held by the observer farther away would tick more
quickly than the clock held by the observer closest to the event horizon.
From the
perspective of the spectator close to the event horizon, one day may have
passed while a decade may have passed for the observer on the outside.
Eventually, the observer close to the event horizon can experience a complete
cessation of time.
The
observer at the event horizon would start to redshift from the outside, which
means that the wavelength of light they emit would shift toward the red region
of the electromagnetic spectrum until the light started to get weaker. Time
would inevitably seem to stop completely before the observer entered the event
horizon. The object would appear to freeze but never actually enter the black
hole, thus in practice we would never see this happen.
When a big
star reaches the end of its lifespan and starts to collapse in on itself,
throwing out massive amounts of gas and dust in a supernova event, black holes
can develop. For this process to take place, the star must be at least three
times as big as our Sun. Extreme time dilation is thought to have a role in the
formation of supermassive black holes, which can range in mass from 100,000 to
tens of billions of times that of the Sun.
Devoured
By a Big Ole Black Hole
If you’re wondering what actually happens when
something gets sucked into the event horizon, the point at which nothing, not
even photons (or light itself), can travel faster than the object’s escape
velocity, thus having no chance of escaping its grasp, the physics gets a
little complicated and our understanding of how things work starts to fall
apart.
It is
thought that an observer within a black hole would gradually lose all sense of
time. Nevertheless, as the black hole gradually tore them apart, atom by atom,
they would expand out. The process of becoming shredded is known as
“spaghettification,” where the gravitational forces during a
“tidal disruption event” pull more strongly on your head than your
feet.
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Artist rendering of a star undergoing spaghettification as |
Fortunately,
when they affect other celestial objects, we can sometimes measure these
events. This is so that we can use specialist telescopes, like the ESO, to
detect the large amount of energy they produce. Often, gas and dust block our
vision, but if we are lucky enough to catch an event just right, we can learn
more about how a supermassive black hole eats matter.
As For Einstein…
According
to Einstein’s comment, both the past and the future are immutable and will
unfold exactly as they were intended to. He also thought that time is an
illusion.
Many
physicists have this opinion, but some have different predictions regarding how
events will develop throughout time. One postulates that the past, present, and
future are mostly unwritten. Or they are all occurring simultaneously. These
goals are greatly aided by the Block Universe Theory.
Do you
believe that Einstein was correct or incorrect overall?
