Of all the planets, Venus has got to be the one that's the most recognized by people.  It's known as the morning and the evening star.  Because it orbits closer to the Sun than the Earth it again, like Mercury, always has to be close to the sun in the sky.  So we're always going to see it either shortly after sunset, or shortly before sunrise.  But unlike Mercury, Venus is further away and so we can see Mercury a little bit later into the evening, which means it's easier to see.  And the other reason people have frequently seen Venus and identify it is because it is the brightest star like object in the entire sky.  The sun and moon are obviously the brightest, but Venus comes next.  Venus shines like a mirror in the sky reflecting the sun's light.  In fact, it's so bright that when Venus is up, and the Moon and Sun are down, you could even read a book just by the light of Venus; it’s that bright. 


Here's a beautiful picture. The first picture in our gallery shows the planet Venus, it's the really bright object there.  And this was a longer exposure picture so that you could see some of the other stars, but you could see that Venus light reflecting off the surface of this water.  And it's something I've seen off Lake Michigan, beautiful Venus reflecting like the sun almost off the surface, really a beautiful planet, which is why, of course, it was given the name Venus - for the goddess of beauty. 


Now Venus is a very interesting planet in lots of different ways. When you look at Venus through a telescope, you really don't see any details.  I've looked at Venus through a small telescope and it's just this little tiny circle.  If you're lucky, you might see some phases, like Galileo observed, but you don't see any details on the surface.  Even with a really powerful telescope, like the Hubble Space Telescope. That's what the second picture gallery shows.  When you look at Venus, all you see is a featureless ball. And that featureless ball is a thick atmosphere, full of clouds, that's reflecting the sun's light, like a mirror, which is why Venus looks so incredibly bright in our night sky. 


To see more of what's happening on Venus, we have to look in other parts of the electromagnetic spectrum; in other colors of light.  If you were to look at Venus, in ultraviolet light, then you would see a view like the third picture in our gallery.  And this is taken prior to the Hubble Telescope, but this illustrates the clouds that are covering the entire surface of Venus.  You can just see these, you know, it looks a lot like clouds on Earth, except the whole planet is completely covered.  So this is a very thick atmosphere on Venus and so it led people to think, well, maybe Venus is a lot like the Earth, you know, the Earth has a thick atmosphere, the Earth has clouds, maybe these clouds are made of water vapor, like the clouds on Earth.  Maybe there's just a lot of rain on Venus, maybe there's tropical forests covering the whole surface.  We can't see the surface of Venus, so people speculated, well, you know, what might be down there? 


Well, as technology improved, and throughout the 1970s, we got better and better ways of actually seeing through these clouds.  And the Russian, the former Soviet Union, actually spent a lot of effort in exploring Venus and probing through these clouds.  They did that in a couple of different ways.  


Well, wait, before I show you that, before I show you that, we should talk about these clouds because these clouds are important.  I know you're, you're dying to see the surface of Venus beneath these clouds, but the clouds are actually really important because in many ways, Venus is like Earth's twin. They're almost exactly the same size.  Right here I can show you that.  The fourth picture in the gallery illustrates that.  See, I've given you a sneak peek of what it looks like beneath the clouds.  


So you see Venus and the earth are almost exactly the same size so they're kind of considered like sister planets or twins.  And because of that, with these clouds, Venus has what's called a greenhouse effect.  So this greenhouse effect, we have that on the Earth as well and you've probably heard of that.  Let me just take a second to explain what the greenhouse effect really is. 


So in a greenhouse, you've got a traditional greenhouse and you got green glass, and you want it to be warm inside.  And the idea is that sunlight passes through the green glass; it just comes right in, and it gets absorbed and things warm.  And just like you and I warm up when sunlight falls on our skin, but when we're warm, we glow; we give off energy.  And the wavelength of light, the color of light that we glow in is the infrared.  Now, as we saw before, infrared light does not pass through glass - remember the man's glasses, they were completely dark in the infrared, because that gets trapped.  And the same thing happens in our atmosphere.  Remember, we saw that graph which showed that our atmosphere is opaque in the infrared.  And so what happens is visible light comes in through our atmosphere and then the heat is here, and then when it tries to escape again as infrared light, the atmosphere traps it, and the heat gets stuck.  And so in that sense, the atmosphere, just like the green glass of a greenhouse, it acts like a blanket, which keeps your planet warm. 


Now this is a good thing, right? It helps keep the Earth warm, which is good, we need a warm, warm place to live, but in the case of Venus, the cloud is so thick, and it has so much carbon dioxide in its atmosphere, in fact, the atmosphere is like 92% carbon dioxide, that the heat gets trapped so much that it is unbearably hot in beneath the surface, I'm sorry, beneath the clouds of Venus.  It's so hot that even day and night it's like 900 degrees Fahrenheit, that's like 450 or more degrees Celsius.  It's hotter than the surface of Mercury because of this runaway greenhouse effect.  


Okay, so the surface of Venus, the only way to actually see it because of this thick atmosphere, to map out the whole surface, the only way to really map it out is using radar.  And that's what these Soviet spacecraft did in the 1970s.  They would orbit around Venus and they would use radar, which is radio waves bouncing off the surface and then creating a visual picture by using all those little pings, those little bounces off the surface.  When you do that, Venus isn't necessarily this color, but this is a map showing what the surface, this is the fourth picture in the gallery, showing what the surface of Venus looks like when you create one of these radar maps. 


And you can see, unlike Mercury or the Moon, the surface appears to be active.  We don't see lots and lots of craters.  Instead, we see what looks like maybe lava flows, canyons, lots of different things.  So it looks like Venus is a geologically active place, much like the Earth is a geologically active place.  All the more reason to think that Venus is like a twin to Earth.  


Now it's really cool is in these 1970s space missions, the Russian spacecraft actually sent landers down to actually touch down on the surface of Venus.  And we have a few pictures of what the surface of Venus actually looks like.  Here's one of my favorites.  And these weren't rovers that could drive around, they would just land and snap a few pictures.  And you could see it looks kind of like a volcanic landscape kind of a dead, deserty landscape.  And the spacecraft that landed didn't last for very long.  In some cases, they crashed.  In other cases, they only lasted 10 or 20 minutes, and in some cases, maybe a few hours at the most because not only is it incredibly hot, I mean so hot, almost that like you know, metal would melt, but it's also an intense, crushing pressure of an atmosphere.  Because the atmosphere is so thick it's like 90 times the pressure that we experience from Earth's atmosphere.  So under those extreme conditions, these spacecraft could hardly operate without breaking.


So this is this amazing irony.  Even though Venus is the sister planet to the Earth, it's the one planet that's similar in size, appears to be geologically active and all these things, it is impossible really for us to ever dream of exploring Venus with people, because it's so hot and the atmospheric pressure is so high that it would be a deadly place to go.  


It paints a picture of how many things have to go right in order to have a planet where life can exist.  Our planet Earth is a beautiful place to live.  We can breathe air, we can drink water, water is everywhere.  It falls from the sky.  It's not too hot, it's not too cold.  There's seasons, there's all these things on Earth that are good and that make life possible.  But all the other planets in our solar system, it seems, have problems with them.  Something doesn't go right.  There's too much carbon dioxide in the atmosphere; there is no atmosphere, maybe there's no surface; it's just a big huge ball of gas.  So our planets have to be, rather meet specific conditions, so that life can be there.  


It's amazing, right?  We think the more you learn about astronomy, there's even more conditions, things like the presence of a moon actually can help life sustain life by blocking asteroids from hitting the surface.  A large planet like Jupiter can help protect a solar system.  So it's amazing to see all the ways that God has built a solar system so that life can exist, not only live on this planet Earth, but be sustained on this planet Earth.  In a sense, there's all these mechanisms and protections and shields that are built into our solar system to make life possible here.


Astronomers are looking for planets around other stars and have found many planets around other stars.  And what remains to be seen is whether any of these other planets have any other life on them. It's an exciting time in astronomy to explore those kinds of questions.  But it'll be interesting to see whether God in His infinite wisdom has put any other living creatures, any other grass or trees or insects or animals, or anything, anything like people anywhere else in this universe of ours.  But if our solar system is any indicator, there's a lot of places in our universe that are deadly places for any sort of living creatures, and there's only one that we know of so far that seems to be perfect for creatures such as ourselves. 


All right, we'll see you next time.



最后修改: 2023年09月25日 星期一 08:44