04/21/2014 08:52 pm ET Updated Jun 21, 2014

Five Science Thoughts to Blow Your Mind


I'm very excited to be presenting at the 2014 USA Science and Engineering Festival, where I'll help share the new Story Time From Space program, which selected my five books for children as the first set to be read by astronauts from the International Space Station. (The books were launched in January. See photos, videos, and more at and on the program's Facebook page.) To give you a taste of what makes me so excited about science -- and of some of the ideas that I hope will inspire children and others -- I thought I'd present five of my favorite mind-blowing thoughts from science.

If You Could Hold the Sun in Your Hand...

Imagine that we could shrink our solar system down to one ten-billionth of its actual size, which would make the Sun about the size of a grapefruit. At this scale, how big is Earth, and how far is it from the grapefruit? Remarkably, Earth is only about 1 millimeter in diameter, or roughly the size of the period at the end of this sentence. This tiny dot orbits the grapefruit at a distance of 15 meters (16.5 yards), completing one orbit each year. The Moon -- the farthest a human being has ever traveled -- is only about 4 centimeters (2.5 inches) from Earth, which means you could fit the entire orbit of the Moon in the palm of your hand. Meanwhile, the rest of the planets are spread out over a distance of some 600 meters (more than one third of a mile) from the Sun. How about the nearest star besides the Sun, or the next grapefruit? Incredibly, it would be some 4,000 kilometers (2,500 miles) away -- equivalent to the distance across the United States at normal scale. (The Voyage scale model Solar System, which can be found in Washington, D.C., outside the National Air and Space Museum, and in several other cities, shows the solar system on this 1-to-10-billion scale.)

Counting Stars (and Planets)

The Sun is just one of more than 100 billion stars in the Milky Way Galaxy. Now, "100 billion" is easy to say, but it's a little tougher to wrap your mind around. So let's suppose you're having trouble going to sleep tonight, and you decide to count stars instead of sheep. How long would it take you to count 100 billion of them? If we assume that you can count at a rate of one per second, then it would take 100 billion seconds -- and if you do the math, you'll find that this is more than 3,000 years! Moreover, based on recent data from the Kepler mission, we infer that most stars have planets, making it likely that there are some 100 billion Earth-like planets in our galaxy. Knowing that it would take more than 3,000 years just to count these worlds, let alone study them in depth, what do you think about the likelihood of there being other life, or other intelligent life?

Black Holes Don't Suck

Imagine that the Sun magically collapsed, retaining the same mass but shrinking in size so much that it became a black hole. What would happen to Earth and the other planets? Ask almost anyone and they'll tell you confidently that the planets "would be sucked in." But it's simply not true. The Sun's change would make Earth very cold and dark, but Earth's orbit would remain essentially the same. So what do black holes really do? For a quick taste of the reality, imagine watching a former friend falling into (which is different from being "sucked into") a black hole. As your friend approaches the black hole's "event horizon," you'll notice her time slowing down -- for example, her heartbeats will happen farther apart -- and light coming from her will become more and more redshifted (from white light to red light to infrared to radio). In fact, from your point of view, time will come to a stop at the event horizon, which means she'll never actually reach it, though she'll fade from view due to the increasing redshift. But from her point of view, she'll barrel straight down through the event horizon in a very short time. This is not guesswork but well-established physics, embodied in Einstein's theory of relativity.

We Make the Universe Self-Aware

The vast scale and amazing phenomena of the universe may make us seem small and insignificant, but there's another way to look at it. As far as we know, we are the only piece of the universe that has any idea that the rest of the universe exists. Moreover, a common thread among nearly all philosophies and theologies is that a key purpose of life is to become truly self-aware. So in this sense we may actually be of the utmost significance to the universe, because after nearly 14 billion years of cosmic evolution, it is through our brain power that the universe has finally achieved self-awareness.

The Greenhouse Effect Makes Life Possible

Turning to a more pressing topic, global warming is one of the most significant threats we face, and it is driven by something called the "greenhouse effect," in which carbon dioxide (and other greenhouse gases) make a planet warmer than it would be otherwise. But the greenhouse effect is not in itself a bad thing; in fact, without the naturally occurring greenhouse effect, our planet would be far too cold for life as we know it. Of course, just because the greenhouse effect is a good thing for life and humanity doesn't mean that more would be better. Just ask Venus: With a thick carbon dioxide atmosphere, Venus has a greenhouse effect so strong that it bakes its surface hotter than a pizza oven -- providing clear proof that it is possible to have too much of a good thing. Let's hope that we learn to understand this message before it is too late. (To learn more about the greenhouse effect and global warming, visit