Spaceship Earth: We Are
Interstellar Travelers
NASA astronaut Karen Nyberg took this photograph of
the sun approaching sunset from the International Space Station in August 2013.
NASA/KAREN NYBERG
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Measuring velocity is a tricky thing to do --
more so if you are trying to measure the speed of a planet upon which you are
observing from. But, through careful observations by astronomers through
history, it has been possible to measure the Earth's orbital velocity around
the sun. Or planet is rattling around interplanetary space at a colossal speed
of 107,300 kilometers (66,700 miles) per hour!
Now, taking into account the movement of the sun
(with all the planets of the solar system in tow) around our galaxy's core
(which is approximately 20,000 light-years distant), we are traveling at around
900,000 kilometers (560,000 miles) per hour. This is a not-so-subtle reminder
that we live on a planet hurtling through interplanetary space, orbiting a star
that zooms throughinterstellar space, taking
225 to 250 million Earth-years to complete one orbit of the Milky Way.
A more obvious hint of our planetary motion is that
of the rotation of our planet around its axis -- the sun rises in the east and
sets in the west, and the stars slowly track across the sky. One day is 24
hours long and our clocks are based on the fact that it takes 24 hours for one
whole rotation. However, this is an 'estimate' since it takes 23 hours, 56 minutes
and 4 seconds for our planet to rotate once.
There are other inaccuracies that affect our
everyday lives. The orbital period of our planet is actually 365.25 days, which
gives us one year, but we use 365 days on our calendars. To correct for this
quarter-day addition each year we stick an extra day on the calendar in
February every four years -- this is known as a "leap year." There
are extra criteria if the year is a "century year" butonly if it is also
divisible by 400. (We do make things complicated for ourselves.)
As Earth travels around the sun, the distance
between the two bodies changes from the closest at 147 million kilometers (91
million miles) -- known as "perihelion" -- in January to the most
distant at 152 million kilometers (94 million miles) -- "aphelion" --
in July. Surprisingly perhaps, this change in proximity is not the cause of the
seasons we experience. Instead, it is the tilt of the Earth’s axis of rotation,
which means the Northern Hemisphere experiences summer when it is pointing
toward the sun while the Southern Hemisphere is in the depths of winter.
The Earth interacts with its surroundings as it
hurtles around the solar system and this can be beautifully demonstrated by the
beauty of meteor showers.
The showers of "shooting stars" are
actually debris from comets shed along their orbit as they orbit the sun. As
Earth plows through these debris clouds, the tiny pieces of dust burn up in the
atmosphere, heating up the surrounding air and ablating, lighting up the sky as
they descend. Earth passes through the orbit of the comets at the same time
each year producing 20 or so popular meteor showers.
It is not just meteor showers that we can observe
from our planetary "spaceship" as we travel around the sun. Aurorae
at high latitudes in the Northern and Southern Hemispheres generate beautiful
light shows as the aurora borealis and aurora australis, respectively.
Aurorae are caused by the interaction of the
Earth's upper atmosphere and solar plasma. We know the sun kicks out a lot of
energy, but it also generates the solar wind that is composed of charged
particles that travel at speeds in excess of 400 kilometers (250 miles) per
second. When they hit Earth they cause the gas in our atmosphere to glow in a
similar way electricity causes fluorescent tubes to glow.
During our busy lives, it can be easy to think that
we are cocooned in a large bubble called Earth, with the universe rotating
around us, when in fact it is us who are
blasting through space, interacting with the interplanetary medium. Instead, if
you look around you, there is plentiful evidence that we are actually
passengers journeying through the solar system and the Milky Way. On even
larger scales, our galaxy and the Andromeda Galaxy are barreling toward one
another at a rate of 400,000 kilometers (250,000 miles) per hour.
It is this movement, this trip on board a spaceship
that we call Earth,that grants us the beautifully changing sights in the night
sky.
SOPA DE LETRAS
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Earth, shooting
stars, atmosphere, comets, orbit, galaxy
Responde
1-¿De qué se trata el texto?
2-¿A qué velocidad aproximadamente se mueve
nuestro planeta?
3-¿Cuál es el indicio más fehaciente de
que nuestro planeta se mueve?
4-¿Cuántas
horas tiene un día?
5-¿Cuántos días tiene un año?
6-¿Qué son las lluvias de estrellas?
7-¿Cómo se producen las auroras?
1-Del movimiento de la Tierra
2-107,300
kilometros (66,700 millas) por hora
3-El movimiento de Rotación
4-23 horas, 56 minutos y 4 segundos
5-365,25 días
6-Las lluvias de "estrellas
fugaces" son restos de cometas arrojados a lo largo de una órbita.
7-Las auroras son causadas por la
interacción de la atmósfera superior de la Tierra y el plasma solar
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