- 3959 - TIME - is it real? - Time is the apparent progression of events from past to future. While it's impossible to completely define the nature of time. Causes lead naturally to effects, we remember the past but not the future and the evolution of time appears to be continuous and irreversible.
----------------------------- 3959
- TIME - is
it real?
-
- Time is one
of the few things we regard as regular and unchanging. But is it really so
constant? There ia some physics of time to give us some answers?
-
----------------------- Is time relative?
----------------------- Is time travel possible?
----------------------- Can time be reversed?
----------------------- Is time discrete or continuous?
----------------------- Is time real?
-
- Einstein's
theory of special relativity revealed that the experience of the flow of time
is relative to the observer and their situation. Previously, the work of Isaac
Newton had assumed the existence of a "master clock" that kept
synchronized time throughout the universe.
-
- This clock
wasn't really thought to exist, but the concept allowed Newton's equations to
work. The key idea was that all observers could agree on the exact same moment
of time.
-
- Einstein
discovered that the passage of time is relative. In “special relativity”,
moving clocks run slowly; the faster you move in space, the more slowly you
progress through time. The closer you get to the speed of light, the greater
this effect becomes.
-
- Einstein
showed in his theory of special relativity that two observers cannot agree on
simultaneous events. In the decades
since Einstein first proposed this concept, physicists have made multiple
measurements that demonstrate this effect.
-
- An atomic
clock aboard a jet airplane will tick at a slower rate than one on the ground.
A subatomic particle called a “muon” doesn't exist long enough to travel from
the atmosphere, where it's generated when cosmic rays strike air molecules, to
the ground. But because muons travel at close to the speed of light, they seem
to exist longer from our perspective, allowing them to complete their journey.
-
- "time
dilation," situations involved with
gravity. The presence of strong gravity also slows the passage of time, so a
clock in a strong gravitational well.
Time on the surface of Earth or near a black hole will tick at a slower
rate than a clock in the middle of space.
-
- Time travel
into the future isn't just permitted, it's mandatory. With every passing second, all of us are
moving forward into our own futures. The future is unavoidable, and it is
impossible to escape. But the reality of relativity makes it clear that
"jumping" forward in time is perfectly acceptable.
-
- If a twin
sets off in a rocket ship and spends a few years traveling near the speed of
light, when they return to Earth, they will have aged less than their
Earthbound twin. Although only a few years may have passed on the spaceship,
decades or even centuries could have passed on Earth, depending on how quickly
the rocket traveled.
-
- In a
real-life example, NASA astronaut Scott Kelly has experienced a few
milliseconds less time than his twin Mark (Scott is also six minutes younger),
thanks to spending a longer time in space, traveling at speeds of around 17,500
mph.
-
- Time passes
differently in space: the faster you move in space, the more slowly you
progress through time. But, time travel
into the past appears to be forbidden.
There is no known mechanism in physics that permits traveling backward
in time. While certain time-traveling situations can be constructed in general
relativity, those situations require entities that don't seem to exist in our
universe, like matter with negative mass, or infinitely long cylinders.
-
- However,
physicists currently do not have a full understanding of why time travel into
the past is forbidden. Almost all laws
and equations that physicists use to understand the natural world are
symmetrical in time. That means they can be reversed without changing any
results.
-
- There is one
aspect of physics that does seem to respect a flow of time: the concept of
“entropy”, which is a measure of the disorder in a system. According to the
second law of thermodynamics, entropy always rises in a closed system, and this
evolution can't be reversed.
-
- Physicists
don't know if the growth of entropy gives rise to the "arrow" of time
or if it's just a coincidence. Almost
all physical theories treat time as a continuum, which is also how we perceive
the flow of time. There is no smallest "unit" of the passage of time.
All events flow smoothly without interruption or hiccups into the next.
-
- However, one
theory of quantum gravity, called loop quantum gravity, hypothesizes the
existence of a smallest possible unit of space-time. This unit would represent
the smallest possible extension of space and duration of time.
-
- In this
theory, what we perceive as smooth, continuous time is really a stuttering,
stop-motion progression from past to future. But because this happens for such
an incredibly brief duration, it appears to be continuous.
-
- Scientists,
philosophers and others have pondered the nature of time. And although we've
learned a lot about time, such as the reality of time dilation and the possible
connection between time and entropy, we haven't been able to come up with a
complete description of what time is.
-
- Some
philosophers and physicists have argued that what we experience as time is just
an illusion, an artifact of our consciousness. In this view, the passage of
time isn't real; the past and future already exist in their complete extent,
the same way the entirety of space already exists.
-
- What we
sense as the flow of time is a byproduct of the way our brains work as we
process sensory information from our environment.
-
April 15, 2023 TIME - is it real? 3959
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--- Saturday, April 15, 2023 ---------------------------
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