When you look up at the bright stars in the nighttime sky, do you WONDER what's out there? Of course, your science teachers have taught you that there are stars, planets, and entire galaxies out there.

But how do we know this? Man has walked on the Moon, but the Moon is fairly close to Earth when you're talking about outer space. How do scientists study the far reaches of the universe?

Over the course of history, man has developed amazing technology to help us see beyond our own planet into the vastness of our galaxy and even way beyond. This technology takes the form of some impressive machines and tools that scientists can use to study the heavens.

One of the earliest tools for space exploration was the telescope. Using lenses and mirrors to see beyond Earth's borders, telescopes gave scientists their first glimpses of what exists beyond Earth's atmosphere.

What scientists were able to learn with telescopes paved the way for manned space exploration. From trips to the Moon to dozens of manned space shuttle flights, teams of humans were able to travel in space and conduct research on a variety of scientific subjects.

Scientists have always been curious. The more we learn about outer space, the more we realize how much more there is to explore. This has led scientists to develop even more powerful tools to help them explore way beyond the places we can go as humans.

For example, the telescope is no longer an Earth-bound instrument. In 1990, the Hubble Space Telescope was launched into outer space. In the last 20 years, it has brought us images of our universe that couldn't have been captured in any other way.

It's a miraculous piece of technology that's powered by sunlight. With many different cameras and types of scientific instruments, the Hubble Space Telescope has provided scientists with invaluable data. In fact, NASA estimates that data from the Hubble Space Telescope has been used as the basis of over 10,000 scientific papers in the past two decades!

Since late 2000, scientists have also been able to conduct hundreds of experiments in low-Earth orbit thanks to the International Space Station (ISS). The ISS is humankind's first orbital space station meant to be used for long-term visits from astronauts from a variety of countries. What scientists learn from the ISS will likely be a stepping stone to sending humans on manned missions to Mars and beyond.

In the meantime, scientists have pushed forward with a wide variety of unmanned machines built to explore the deepest corners of our solar system. Unmanned probes, such as NASA's Cassini probe, have been sent to explore other planets. If you've seen a spectacular picture of Saturn recently, you can thank the Cassini probe.

Astronomers have always been fascinated by Mars, and we know more than ever about Mars today thanks to the Mars Reconnaissance Orbiter and the Mars rovers, Spirit, Opportunity, and Curiosity. The rovers are powerful robots that have helped scientists learn a tremendous amount about the geology of Mars.

As time marches on, scientists will continue to learn more and more about our universe using advanced scientific technology to create tools to explore the depths of space. For example, thanks to the Kepler telescope, launched in 2009, scientists now know that there are possibly over 3,000 planets orbiting over 2,000 stars in the Milky Way galaxy, none of which were known about until the last couple of years!

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