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Mercury is the closest planet to the Sun, but that doesn’t tell us how close it is in miles. Due to the planet having a wildly elliptical orbit, the exact distance from Mercury to the Sun is always changing.
Trying to compare the distance of two moving objects traveling in elliptical orbits is even more complicated, and that’s exactly what you have to do if you want to figure out how far Mercury is from Earth.
Don’t worry, we break it all down for you here and answer a few other questions that you might have.
While NASA states that Mercury resides at an average distance of 36 million miles from the Sun, it’s important to note that its exact current distance from the Sun is always changing. Mercury, like all planets, has an elliptical orbit, so at some points, it’s closer to the Sun than at others. You might not think that makes much of a difference, but at its closest point, Mercury sits just 28.5 million miles from the Sun, almost 7.5 million miles closer! When Mercury is at its farthest point away from the Sun, it’s 43.5 million miles away, or 8.5 million miles farther than average! Basically, if you’re trying to calculate the exact distance from Mercury to the Sun, it’s going to change day by day and minute by minute.
This is a complex question because not only is the orbit of each planet elliptical, but they’re also going at different speeds. So, sometimes the planets can be on complete opposite sides of the Sun, while other times, they can be much closer to each other.
Still, on average, Mercury sits 1.04 AU away from Earth, which is about 96.7 million miles. If Mercury and Earth were at their closest possible points to each other, that distance would shrink to just 48 million miles. That hypothetical distance almost never happens, though; the closest that we usually get is a little over 50 million miles. But the farthest that the planets can get from each other is about 138 million miles!
That means there’s a 90-million-mile gap between the shortest distance and longest distance, which is almost the same average distance that the planet sits from Earth!
Light might travel fast but it’s not instant. Due to the extreme distances in space, it takes a little while for the light from Mercury to reach Earth.
Light travels at 186,000 miles per second, so at Mercury’s shortest distance from Earth, it takes just over 258 seconds for its light to reach us. That’s 4 minutes and 18 seconds!
When Mercury is at its farthest point from Earth, it takes just under 742 seconds, or 12 minutes and 22 seconds, for light to reach Earth.
Finally, from the average distance of Mercury, it takes about 520 seconds for light to reach Earth, or almost 8 minutes and 40 seconds!
Mercury sits much closer to the Sun than the Earth, so the light that leaves the Sun reaches Mercury far sooner. The average amount of time that it takes light to reach Mercury from the Sun is just 3 minutes and 13.5 seconds, but since Mercury has an elliptical orbit, this number does vary.
At Mercury’s closest point to the Sun, it takes light just 2 minutes and 33 seconds to reach the planet, and at its furthest point, it takes 3 minutes and 54 seconds for light to get there.
While Mercury might be the closest planet to the Sun, there’s actually a twilight zone on Mercury that humans could technically walk on without melting to a crisp or freezing to a popsicle.
One side of the planet is enough to melt lead, and the other side is one of the coldest places in space. The space in between is where the temperature is tolerable.
Even better, if you can keep moving, it’s completely possible to stay in that zone for as long as you want. It takes 88 days for Mercury to complete one day-and-night cycle, giving you plenty of time to keep moving to stay on the terminator line!
While 50 million miles is quite the distance, considering that a few of our spaceships go 25,000 miles per hour just to escape Earth, we should be able to reach Mercury in fewer than 3 months. So, why does it take years for modern space missions to reach the planet?
It all comes down to the need to slow down. Between the gravity of the Sun and the rockets that we use, getting there fast isn’t the problem. The problem is Newton’s first law of motion: An object in motion stays in motion with the same speed unless acted upon. When a spaceship is traveling at 100,000 miles per hour or faster, it takes a great deal of force and energy to slow it down.
Therefore, spaceships going to Mercury, not just completing a flyby, need to make multiple passes to get into Mercury’s orbit. This takes time, which means space missions take quite a long time to get there!
Related Read: How Did Mercury Get Its Name? What You Need To Know
Mercury is the closest planet to the Sun, and while it’s not right next to it, even a few million miles away, this planet is scorching hot when it faces the Sun!
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Featured Image Credit: TheSpaceway, Pixabay
Robert’s obsession with all things optical started early in life, when his optician father would bring home prototypes for Robert to play with. Nowadays, Robert is dedicated to helping others find the right optics for their needs. His hobbies include astronomy, astrophysics, and model building. Originally from Newark, NJ, he resides in Santa Fe, New Mexico, where the nighttime skies are filled with glittering stars.
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