Archive | April, 2016

Jupiter D.5.1

30 Apr

What is the outer solar system? There is Jupiter, Saturn, Uranus, Neptune, and Pluto…

To reach Jupiter from Mars, we’d have to travel a distance that is more than twice the distance in going from the Sun to Mars. And we’d have to pass through the asteroid belt.

One thing about Jupiter is it’s got a very strong banded appearance to it. You’ve got white clouds and sort of reddish clouds. And they come in very distinct bands. And then somewhere out near the outer fringe you have the great red spot. And that great spot is large enough to swallow two or three times the size of the Earth.

Jupiter is mainly made of hydrogen and helium. And so if we plunged into Jupiter with a probe the pressure would crush it long before it ever got to the solid core.

Jupiter reigns over about a dozen moons and a very thin set of rings. And the four moons which Galileo discovered are called Galilean satellites, are Io, Europa, Ganymede, and Callisto. And they’re large enough to be considered planet-like worlds on their own.

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Mars D.4.30

29 Apr

Mars has a size that is about 50 percent the size of the earths, and it is a world of wonders containing ancient volcanoes that dwarf anything on earth. So, for example, Olympus Mons on Mars makes Mount Everest look like a little pop gun. There is a great canyon on Mars that runs one-fifth of the way around the planet. So Valles Marineris makes the Grand Canyon look like, child’s play.

It has ice caps. It is primarily made of carbon dioxide, so CO2, and water, H2O. And although it’s frozen today, you can clearly see evidence, geological evidence and visual evidence, that, from the presence of river beds, rock-strewn flood plains, minerals that only form when there is water offer clear evidence that Mars, at least sometime in the past, was warm enough to have very wet periods and water flowing over the surface. That probably ended about a billion years ago.

Mars is the most studied planet besides earth. More than a dozen missions have either flown past, or orbited, or landed on Mars, and there are plans for additional such missions in the future.

Earth D.4.29

28 Apr

Although earth is only a speck when viewed on the scale of our solar system, it is the only known oasis of life. And that drives; I think a look back at the blue marble from the surface of the Moon. It is the only planet that we know that has oxygen for us to breathe, an ozone layer to protect us from the ultraviolet rays coming down from the sun. It has abundant surface water to nurture life, and the atmosphere has just enough carbon dioxide and water vapor to maintain a moderate greenhouse effect.

The greenhouse effect is in some sense good. If earth did not have a greenhouse effect, we would be as frozen as Mars would be. The atmosphere would freeze out. But, on the other hand, you don’t want too much of a good thing. That would be Venus, where the greenhouse effect boiled off all the waters. And so we’re sort of like Goldilocks and the Three Bears. We’re right in the middle. We want to have just enough to make it temperate and nice for life, but not too cold and not too hot.

Venus D.4.28

27 Apr

Venus is nearly identical in size to the earth but rotates very slowly, so that its days and nights are very long. And not only does it rotate very slowly, it also rotates backwards relative to the other planets in the solar system. So if you take a look at our solar system from above, you would see that all the planets rotate in a counter clockwise direction, but Venus, because it rotates backwards Goes clockwise.

In other words, the sun rises in the west and sets in the east on Venus, so it’s a little bit different. Venus is mainly covered by clouds. The atmosphere is so thick, so heavy, so dense that you really don’t see anything.

Venus has a tremendous greenhouse effect, runaway greenhouse effect that keeps the temperature at about 470 degrees Celsius, same as Mercury’s, but it does so everywhere. Whereas Mercury had this very sharp differentiation between sun side and night side, Venus is the same burning temperature everywhere.

In part because of its amazing greenhouse effect, the fact it rotates slowly so there’s no weather, and so all of it makes for a really lovely place to visit, 470 C, year round, all the time, every day. The atmosphere is extremely thick. In effect, what happened is Venus had oceans, but those oceans evaporated and became the atmosphere. And so if you’re on the surface of Venus, you would effectively feel an ocean’s worth of atmosphere crushing down on you. It’s the equivalent of being like roughly a mile or so beneath the surface of an earth’s ocean. So if you want to see the surface of Venus.   If you want to get away from the cloud you have to look in wave lengths other than physical wavelengths other than optical. And so this has been done – In particular radar wavelengths from the Magellan spacecraft. Venus has all kinds of geological features associated with it. Clearly has lava flows. It’s been hit by some craters, but not a whole lot. But you can see an active geology taking place on Venus.

Mercury D.4.27

26 Apr

Mercury is the innermost. It is also the smallest of the eight planets. And, yes, I said eight planets. And it is a cratered world of iron and rock.

It has no volcanoes, no atmospheres, and no life. That doesn’t make it boring. It’s just different.

One of the interesting things about Mercury is that solar tides force it into a particular mode of spinning and orbiting the sun. So Mercury rotates three times for every twice that it orbits. And this gives Mercury days that last about three months each. And this relatively unique phenomena of the solar tides causing this three- rotation-to-two-orbit period is one of the things that was used in the early part of the 19th century as a, one of the first confirmations of Einstein’s theory of relativity.

To explain this motion with Newtonian gravity simply did not work all that well. And it took going beyond Newtonian gravity in order to explain this very unusual orbital phenomenon of Mercury. So Mercury is, may not have much geological activity or atmosphere or life, but nevertheless has been very important in our development of understanding of the solar system.

Because it has no atmosphere, the daytime temperature on Mercury reaches about 425 Celsius, which is about as hot as a piece of coal, from the blast furnace of the sun. But, on the other hand, because it doesn’t have an atmosphere, it can’t moderate its temperatures, and so in the shadows or in the nighttimes, it’s a frigid minus 150 degrees C, colder than Antarctica. So it’s quite possible to go from burning hot surfaces to cold, the colder Antarctica, inside of a little bit as you transition from a sun-baked side over to the night-time side.

The Sun D.4.26

25 Apr

The sun is a star. It is 4.6 billion years old. And it is the most influential object in our solar systems. It is gaseous throughout, so it’s made of gas. It’s made primarily of hydrogen, about 74 percent or so. About 24 percent is the next lightest element, which is helium, and only 2 percent is everything else, which, of course, is what makes you and me all that carbon, oxygen, iron, all this stuff, but only makes up 2 percent of what the sun and the rest of the solar system is made out of.

The sun contains 99.9 percent of our solar system’s mass, and its gravity utterly dominates the orbits of the planets. It’s light because there is fusion going on around the core. Its light is the primary influence on the temperature of planetary atmospheres and planetary surfaces.

For example, earth’s atmosphere is utterly dominated by the energy input coming from the light from the sun. And that happens both for planets closer in, whether that be Venus or whether it’s farther out on something like Jupiter.

In addition to its gravity and the light coming out, the sun also has this wind that blows out from it. It’s called the solar wind, typically is made of charged particles, protons and helium particles.

And that wind blows out and it helps shape what a planet’s magnetic field looks like and whether the solar wind can strip away the atmosphere of a planet potentially if it doesn’t have a magnetic field. And so there’s sort of like three really important, dominant reasons why the sun is sort of the big object in our solar system.

Observing non-visible light D.4.24

23 Apr

How do we catch bullets of light? How do we observe things like radio waves, or infrared, or ultraviolet, x-rays, and gamma rays? How do we catch those different types of lights which have different energies associated with them? And, can you take multiple telescopes make them act as one telescope and thereby improve your angular resolution?

Telescopes for non-visible light generally follow the idea of using a reflector to catch the light and bring it to a focal point. Now, let’s take it from the other extreme, where you have high energy photons like an x-ray photon or a gamma ray photon or something like that. And, these things are basically bullets of energy. How do you catch a bullet of light? Basic answer is, you don’t.

What you try and do is, you try and skip that high-energy photon. You just bend it a little bit each time. Bend it out, bend it out, bend it out, bring it on down until you bring it down to your detector. Which then, it’s okay to absorb the photon because you’re interested in what the energy of the photon, and where it came from, and so on. So, in order to catch the high energy bullets, you don’t catch it directly.

But, as you skip rocks as you skip it on down, until you bring it on to your target.