One of the fastest planned spacecraft on Earth is the Parker Solar Probe. This means that the spaceship may get to the Sun in around hours or nine days.
However, there is an additional problem. Since when it comes to space, distances take on a whole new value, maybe with this hypothetical scenario, we might more easily familiarize ourselves with the actual length of the Sun, how far away it is. So how long would it take to get to the Sun in a car? If our car would travel at a constant speed of around mph, and if we could drive for 24 hours without rest, then we would reach the Sun with our car in more than years. However, this also implies that our oxygen, food, and fuel reserves are infinite, and we would travel towards a correct estimation of where the Sun would be at, in around years.
In a Jumbo Jet, it may take up to 19 years to get to the Sun from Earth, so regardless of our current daily traveling methods, it would take more than a lifetime to reach the Sun. The next closest star to us is about 4. All of the other stars we can see with our eyes are farther, some even thousands of light-years away. Stars are found in large groups called galaxies. A galaxy can have millions or billions of stars.
The nearest large galaxy to us, Andromeda, is 2. So, we see Andromeda as it was 2. The universe is filled with billions of galaxies, all farther away than this.
Some of these galaxies are much farther away. It is A light-year is the distance a beam of light travels in a single Earth year, or 6 trillion miles 9. On the scale of the universe, measuring distances in miles or kilometers doesn't cut it. In the same way that you may measure the distance to the grocery store in the time it takes to drive there "The grocery store is a minute drive away" , astronomers measure the distances of stars in the time it takes for light to travel to us.
For example, the nearest star to our sun, Proxima Centauri , is 4. Unlike the speed of your car when running errands, the speed of light is constant throughout the universe and is known to high precision. To find the distance of a light-year, you multiply this speed by the number of hours in a year 8, The result: One light-year equals 5,,,, miles 9.
It's time to move to the metric system like everyone else. But what if you want the distance from New York to Los Angeles? Sure, you can still use meters with a distance of about 3. But really, kilometers is just a nice way of using meters. It's the same unit of distance, just with a prefix. Units of meters or kilometers works well enough for things as big as the Earth, with a radius of about 6. However, outside of the Earth stuff starts getting super big.
With very large things it's often useful to use very large distance units. Let's go over the three most common distance units in astronomy. The name of this unit sort of makes it sound more important than it is—it's still important, but not for the rest of the universe.
That's not technically correct since the Earth's orbit around the Sun isn't perfectly circular. Let's just say the AU is the average distance to the Sun—that will work for now. With the AU, it's much easier to measure distances in the solar system. For instance, the distance from the Sun to Mars is about 1.
But there is an even better reason to describe distances in AU than just convenience. Humans first used the Astronomical Unit because we didn't know the distance from the Earth to the Sun. Yes, that sounds crazy, but it's true. So, here's the deal. The ancient Greeks did some awesome measurements of the Earth and moon and they tried to get the distance to the Sun —but that one's pretty tough. But even without an accurate value for the Sun-Earth distance, later astronomers could still do some nice modeling of the solar system.
In fact Johannes Kepler found the the time it takes a planet to orbit the Sun was proportional to its distance to the Sun again, technically these orbits are ellipses. Using this, he determined the distance from other planets to the Sun in terms of the Earth's distance. Boomthat gets you the distance in AU. Of course no one wants to stop and leave all the solar system stuff in terms of AU.
We really want the conversion factor between AU and meters. To get this, you need to actually measure the Earth-Sun distance.
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