Spaceship Earth: We Are Interstellar Travelers

//

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!

Trace looks back on how humans first ventured beyond our atmosphere, and how very far we've come since those early days of space exploration.

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 through interstellar space, taking 225 to 250 million Earth-years to complete one orbit of the Milky Way.

PHOTOS: Astronomy Photographer of the Year 2013 Award Winners

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" but only 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.

PHOTOS: Top 10 Treats for Summer Astronomy

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.

PHOTOS: Monster Desert Telescope Construction Complete

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.

DISCOVERYnewsletter
 
Invalid Email