Light speed, or 300,000 kilometers a second, might seem like a speed
limit, but this is just an example of 3 + 1 thinking – where we still
haven’t got our heads around the concept of four dimensional space-time
and hence we think in terms of space having three dimensions and think
of time as something different.
For example, while it seems to us
that it takes a light beam 4.3 years to go from Earth to the Alpha
Centauri system, if you were to hop on a spacecraft going at 99.999 per
cent of the speed of light you would get there in a matter of days,
hours or even minutes – depending on just how many .99s you add on to
that proportion of light speed.
This is because, as you keep
pumping the accelerator of your imaginary star drive system, time
dilation will become increasingly more pronounced and you will keep
getting to your destination that much quicker. With enough .999s you
could cross the universe within your lifetime – even though someone you
left behind would still only see you moving away at a tiny bit less than
300,000 kilometres a second. So, what might seem like a speed limit at
first glance isn’t really a limit at all.
To try and comprehend
the four dimensional perspective on this, consider that it’s impossible
to move across any distance without also moving through time. For
example, walking a kilometer may be a duration of thirty minutes – but
if you run, it might only take fifteen minutes.
Read more at: <span>https://phys.org/news/2011-10-light-speed.html#jC</span>
A planet cell is a cell on a planet
Answer:
Cohesion and adhesion of water molecules
Explanation:
Cohesion has to do with the ability of water to adhere together .
The cohesive properties of water which is occasioned by hydrogen bonding between adjacent water molecules allow the column of water to move up through the plant irrespective of the force of gravity as water molecules are evaporating at the leaf surface.
The adhesive properties of water, which means, the attraction between the water molecule and the xylem wall also ensure continuity in the movement of the water column in the xylem.
Hence the cohesive and adhesive properties of water molecules are important for transpiration to occur.
It is true that studies of animals show that they play only when the physical survival needs have been met; however, there is growing evidence that for children, play is crucial in terms of biological evolution as well as individual development.
